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BULLETIN OF THE

No. 5

Contribution from the Bureau of Entomology, L. O. Howard, Chief
September 27, 1913.

'/n

THE SOUTHERN CORN ROOTWORM, OR
BUDWORM.

By F. M. Webster,
In Charge of Cereal and Forage Fnsect Investigations.

DISTRIBUTION.

The parent of the southern corn root worm {Diahrotica duodeciin-
piinctata Oliv.), or. as it is often termed, the biidworm, is a yellow
or greenish-yellow beetle having 12 black spots on the back, as shown
in figure 1, «, from
which its specific name,
meaning " 12-spotte(l."
is derived. It is closely
allied to the almost
equally common striped
cucumber beetle {Dia-
hrotica vlttata Fab.),
and also to the parent
of the even more de-
structive western corn
rootworm ( Diahrotica
longicornis Say).
Throughout the coun-
try east of the Rocky
Mountains, extending
from southern Canada
southward to North
Carolina. Tennessee,
Arkansas, and Oklahoma, these 12-spotted and striped beetles to-
gether frequent squashes and piunpkins, often collecting in num-
bers in the blossoms. The l"2-spotted species during late summer and
fall also frequents, often in conspicuous munbers. the flowers of the
various species of goldenrod (Solidago).

The larva* (fig. 1, c) do not generally attack growing corn in suf-
ficient numbers to cause any considerable injury, except perhaps

6134°— 13

Fig. 1. — The southoni corn i-ootworm i Diahrotica duo-
decimpunciata) : a. Beetle; 6, egg; c, larva; d, anal
segment of larva ; e, work of larva at base of corn-
stalk ; /, pnpa. All much enlarged, except e. reduced.
(Reengraved afti>r Riley, except /, after Chittenden.)

2 BULLETIN 5, U. S. DEPARTMENT OF AGRICULTURE.

locally, north of the States mentioned in the j^recedino- paragraph,
althongh in 1800 .some damage was done in the southern portions of
Illinois, Indiana, and Ohio. Southward from the latitude of these
States to the Gulf, and extending into Mexico, however, serious rav-
ages are of more or less frecpient occurrence. The author reared the
beetles from larvae that were attacking late-planted corn at La
Fayette, Ind.. during July and early August, 1888, though there was
no serious injury to the cro[) as a whole. A larva was also observed
by the author in the act of eating into a stem of young wheat in the
field, on October 11, 1890, in the same locality, but the species is not
of importance as a Avheat insect.

FOOD PLANTS OF THE LARV^.

It is probable that the larva? have attacked corn in the Southern
States for at least a century or more. Prof. A. L. Quaintance re-
corded them as feeding not only on corn but also on the roots of rye,
garden beans, and southern chess (Brofnus unioloides) in Georgia,^
worldng serious injury to both corn and beans. The author ob-
served the larvae attacking young wheat at La Fayette, Ind., October
11, 1890, while Mr. E. O. G. Kelly observed the same thing to occur
at Wellington, Kans., October 2, 1907. March 1, 1909, Mr. T. D.
Urbahns, at Mercedes, Tex., found larva? one-half inch in length
on the roots of young alfalfa and from these reared adults March 19.
April 20, 1911, Mr. George G. Ainslie found larva? in abundance
feeding on the roots of 3^oung oats about Jackson, Miss. Adults from
these larva^ emerged May 17. The same observer reared adults from
larvae found feeding on the roots of barnyard grass {E chinochloa
crus-galli) at Hurricane, Tenn., on July 12, 1912, the adults in this
case emerging on July 21. The grass upon the roots of which the
larvae were feeding grew up among and between corn that had pre-
viously been attacked and killed by the pest.

Dr. F. H. Chittenden ^ states that larva^ or pupae have been ob-
served at the roots of corn, wheat, rye, millet {Panicivm millaceum),
southern chess [Brotnus unioloides), beans, goldenglow {Rudheckia
sp.), and sedges of the genera Cyperus and Scirpus. Larvae have
been found and reared by him from about the roots of Jamestown
weed {Datura stramonium) and pigweed (Amaranthus), and it is
not improbable that they feed on these plants.

Prof. E. Dwight Sanderson ^ reported the larvae working upon the
roots of Johnson grass {Sorghum halepense) where these roots at
the time appeared older than those of the corn. Under date of Feb-
ruary 19, 1907, Mr. Dick Hatcher, of Fross, Tex., through Repre-

lU. S. Dept. Agr., Bur. Ent., Bui. 26, pp. .38-39, 1900.
- V. S. Dept. Agr., Bur. Ent., Circ. 59, p. 4, 1905.
3 Entomological News. vol. 17, p. 213, .June, 1906.

THE SOUTHERN CORN ROOTWORM, OR BUDWORM. 3

sentative Burleson of that State, informed the Avriter that the larva^
begin to work on the roots of Johnson grass during the hitter part
of July, They eat small holes under each joint, and by the latter
part of November the roots are dead, and the Johnson grass, as he
expressed it, '' looks more like rotten sea grass than anything I can
compare it to." This correspondent refers to their work on John-
son grass as being more beneficial than otherwise.

FOOD OF THE BEETLES.

The fully developed insect, or beetle (fig. 1, a), is a decidedly gen-
eral feeder, eating readily almost any cultivated plant. A list of
its food plants would be more interesting for what it did not include
and if given in full would be entirely out of place in a publication
of this character. Of grain and forage crops it has been observed to
feed on corn, wheat, oats, rye, barley, buckwheat (probably), alfalfa,
cowpea, soy bean, clover, timothy, milo maize, Kafir, pearl millet,
vetch, Johnson grass, and rape.

DEPREDATIONS OF THE LARV^ IN CORN.

Just when the southern corn rootworm, or budworm, as it is tenned
in the South, first began to attack corn is involved in obscurity. The
writer several years ago ^ called attention to the fact that it was
probably this insect to which a Mr. Charles Yancey,- of Buckingham,
Va., referred when he described '' a little white worm with copper-
colored head " which, perforating the stalks of young corn " just be-
low the surface of the ground," destroyed the growth. The budworm
has certainly been accused of attacking corn in Virginia and other
Southern Atlantic Coast States since long before the recollection of
the oldest inhabitants. Quaintance ^ found excellent ground for be-
lieving that the pest was injurious in the cornfields of Georgia '' many
years before we find any reference to it in the literature of economic
entomology." The first exact observations on the ravages of the
larva3 (fig. 1, r) in growing corn, the identity of the pest being known
at the time the observations were made, were by the writer and pub-
lished shortly afterwards,* as follows:

While in the South during the spring of 1886 we frequently heard of fields
of young corn being seriously injured during some seasons by a small white
v.orm which attacked the roots, usually during April. * * *

On April 12 of the present year [1887] we were enabled to solve the problem
by finding considerable numbers of these larviP in the field of corn in Tensas
I'arish, La., where they were working considerable mischief by killing the young

. 1 U. S. Dept. Ag!-., Insect Life, vo\. 4, p. 264. 1892.
-American Farmer, vol. 10, p. :!, 1828.
3 Loc. cit., p. .3(3.
* Report of the Commissioner of Agriculture for 1887, p. 148, 1888.

4 BULLETIN 5, U. S. DEPAKTMENT OF AGRICULTURE.

l/huits. As observed by us, tbeir mode of attack ditiered from that of their
northeru congener iu that they did uot appear to attack the fibrous roots or
bury themselves in longitudinal channels excavated in the larger roots. On the
contrary, they burrowed directly into the plants at or near the upper whorl of
roots, which alniopt invariably resulted in the death of the plant. These larvae
were much more active than those of hnigicorma, and on being disturbed would
make their way out of their burrows and attempt to escape by crawling slowly
into crevices in the soil, or if it were tiuely pulverized they would work their
way down into it out of sight. Often several individuals, varying greatly
iu size, would be found about a single plant. On the 20th of same month, in
another field, we found the larvse much more numerous and the crop injured
fully 75 per cent. Plants here, 6 to 8 inches high, were withering u]) and dis-
coloring. Both of these fields had produced cotton the preceding year.

April 27, 1888, serious attacks to j-oung growing corn were ob-
served on Perkins's plantation, near Somerset Landing, Tensas Par-
ish, La., and on May 12 similar depredations were noted in the vicinity
of Madison, Ark. Still later the author found the larvae attacking
late-planted corn at La Fayette. Ind., July 12, and on July 14 of the
same year 595 of these larvae were collected and placed in rearing
cages, adults from which appeared August 2 and 3. In all of the
localities just given, except the last, the ravages wereon corn growl-
ing in the low damp lands. Throughout the South and even farther
north the soil of the low lands and depressions in fields is of a darker
color than that of more elevated areas, hence the statement of farmers
and planters that the pest is more destructive on the " black lands."
Prof. H. Garman ^ stated that to his personal knowledge corn had
been injured during the years 1880 and 1890 in Virginia, Alabama,
Mississippi, Louisiana, Arkansas, Kentucky, Illinois, and Ohio.

LOSSES CAUSED BY THE LARV^.

As showing the magnitude of the losses caused by this insect,
especially throughout the South, illustrations have been selected from
notes and correspondence of the bureau. During May, 190G, the
writer found that one-fourth to one-third of the young corn growl-
ing on the farm of the State Hospital for the Insane, at Columbia,
S. C, w^as being destroyed by these j^ests. The damage was being
done more especially on the low parts of the fields with black or
gray soils. Under date of July 15. 1907. Mr. R. F. Haynes, of
Cheoah, X. C, stated that the corn cro]) had been ruined in many
j:jlaces during the spring by a worm that burrowed into the plant
just above the base of the roots. Under date of March 20, 1908,
Mr. D. P. High, of Whiteville, X. C. stated that farmers in his
neighborhood had difficulty in getting a stand of corn on their bot-
tom lands by reason of the attack of these worms. In his opinion it
was becoming the greatest cornfield pest, especially in cold, wet

1 Psyclie, vol. 6, p. 30, 1891.

THE SOUTHERX CORN KOOTWORM, OR BUDWORM. 5

sprinirs, like the one of tliat year. A similar complaint was received,
April 10 of the same year, from Mr. J. L. Hughes, of Chatawa,
Miss., who stated that he had replanted his corn three times and the
worms were still destroying- his crop, although the stalks of corn
were 6 inches to a foot in height. Under date of May 24, 1909, Mr.
Sidney Johnson, Boydton, Va., sent specimens of the larvae, with com-
plaints of serious ravages in his neighborhood. March 21, 1910,
Mr. Milton Mountjoy, Shacklett. Va.. stated that frequently the corn
in his neighlwrhood was ruined over gi^eat areas by this pest. Under
date of July 30, 1910, INIr. C. L. Foster, of Dalton, Ga., complained
of great damage to the coni crop of his section by this pest, and for-
warded specimens. In some instances the com had been replanted
three times and still was so badly injured that there was little pros-
pect of a crop. Mr. J. O. Taylor, writing under date of August 17,
1910. from Bastrop, La., stated that early planted corn during that
season had been seriously damaged and in many cases destroyed by
this rootworm or budworm, which he clearly describes, as well as
its method of attack. Julv 15. 1912, Mrs. A. E. Ballah, of Philippi,
W. Va., complained that her com had been ruined that year by this
pest. Writing under date of February 1, 1912, from Brandon, Ky.,
Mr. Kobert B. Parker, statistical agent, stated that corn was dam-
aged 50 per cent in his part of the country by these worms. In
some fields they had destroyed as high as 75 per cent of the crop.
May 27, 1912, Mr. George G. Ainslie found a portion of a cornfield
near Hurricane, Tenn., that had been damaged fully 95 per cent by
these larvae. Under date of December 4, 1912, Mr. G. M. Goforth.
county demonstrator, writing from Lenoir, X. C., stated that this
worm caused a loss of thousands of dollars every yeai^ in his
(Caldwell) county.

HABITS OF THE LARV^.

The actions of the very young larvae are in a sense forecasted by
the observations made by Quaintance on the method of oviposit ion.
No one else appears to have observed the method of oviposition in
the open fields, but Quaintance has found that the stylus-like ovi-
positor of the female is pushed down into the soil to a depth of from
one-eighth to one-fourth of an inch and held there until the egg is
forced down the exteu'^ible oviduct. This requires usually but a few
seconds, and after moving a short distance the beetle may deposit
another egg in the same manner.^ Quaintance further states that
larvae, placed on the roots of com at one end of a root cage, after
the destruction of this corn made their way through the soil to a

1 Mr. R. A. Viekpr.v, in North Carolina, found that ogss wore deposited in the soil by
females in confinement without reference to the corn plants growing therein.

6 BULLETIN 5, U. S. DEPAKTMENT OF AGEICULTURE.

plant 10 inches distant. He also observed that larvae may descend
from S to 10 inches below the surface of the soil in search of food.

These observations are substantiated by Mr. Georjre G. Ainslie, who
studied the habits of the larvae in the field at Hurricane, Tenn.,
during May, 1912. In this case, upon cligreing up the injured corn
plants he found that the roots and stem below the ground were
grooved, furrowed, and perforated. In many instances there was a
distinct perforation into the base of the plant which cut off the
croAvn, thus destroying the central leaves. The larva^ were found
either in the partly decayed kernel or along the underground stem in
the earth. Only occasionally were the larvae found with their heads
in these holes in the stem. Mr. Ainslie experienced difficulty in find-
ing these larvae, it being necessaiy to dig over the earth thoroughly
for a considerable distance around each plant, some of the larvae
being found 4 inches from the injured plant and at a depth of 3 or 4
inches. The author also had observed this habit in the young larvae
in previous years, and there is always difficulty in reconciling the
number of larvae one can obtain in badly infested fields with the
damage clearly to be charged to them. In many cases the hole made
in the plant is not clean-cut, as shown in figure 1, e, but has some-
what the appearance of liaving been simply bruised. This is prob-
ably the work of the young larvae, while the clean-cut hole is the
work of those individuals that are larger and more fully developed.

The larvae of the species under consideration, aside from the work
while very young, as described by Mr. Ainslie, eat directly through
the outer walls of the base of the plant into the heart of the plant,
usually just above the base of the roots, as shown in figure 1. e. The
term " rootworm " is somewhat of a misnomer, because these larvae
are not usually found in the roots, and as a rule do not feed within
them, as is the case with tlie allied western corn rootworm (/>?'«-
hrotica longlcornis).

OVIPOSITION.

The females, which have passed the winter in the adult stage, com-
mence egg laying soc«i after the first warm weather of spring. The
statement of Quaintance that the eggs are usually all deposited within
the space of two or three days, while perhaps true as a rule, is not
entirely borne out by the observations of others. For instance, Mr.
R. A. Yickery at Brownsville, Tex., found that one female deposited
102 eggs during January 18, 19, and 20: another female deposited
22 eggs, 9 on January 19 and 13 on January 28. There does, how-
ever, appear to be a tendency on the part of the individual female to
complete o^•iposition within a few days; and this feature in the
life histcry is of considerable economic importance, as it shows that
the egg-laying season for the individual in spring is not long drawn

THE SOUTHEEN CORN ROOTWOEM, OR BUDWORM. 7

out and that therefore remedial measures will be more effective than
they would be otherwise. It has been generally observed, however,
as between different females, that some contain eggs much less ad-
vanced than others, so that while the time required for the oviposition
of a single individual may be very short, some individuals may have
finished the process before others have begun. Even under such cir-
cumstances the egg-laying period can not be said to be exceptionally
protracted.

SEASONAL HISTORY.

While it is possible that the insect may occasionally pass the winter
as larva or pupa these instances have been observed too rarely to be
considered otherwise than abnormal. Throughout the entire coun-
try, from Brownsville, Tex., northward, the insect normally passes
the cooler months in the adult stage.

In southern Florida and southern Texas, where the insect remains
active throughout the winter, the generations are but indistinctly
defined. Northward, however, the species has a definite period of
hibernation.

Mr. Vickery has observed the sexes pairing in North Carolina in
November, and the author observed this at La Fayette. Ind., Sep-
tember 18, 1888, while Mr. Kelly made a similar observation at Man-
hattan, Kans. Mr. T. D. Urbahns found larvse about half an inch in
length in the roots of alfalfa at Mercedes, Tex., November 1, 1909,
from which two adults developed November 19. Mr. Vickery has
observed the males to fight each other most strenuously.

From the foregoing it would seem that pairing may sometimes
lake place during the late fall prior to the spring oviposition. Cer-
tain it is that many of the females are filled with fully developed
eggs in very early spring, and, as will be shown, they have been fre-
quently swept from wheat and oats, where they were observed to be
• feeding, before corn has even been planted.

This early appearance and feeding of the adults has been observed
b}' Mr. Vickery at AVinston-Salem, N. C, March 23. on rye, and at
Statesville, N. C, March 29, on wheat; by Mr. Urbahns at Santa
Maria, Tex., March 6, on oats; by Mr. George G. Ainslie at Nashville,
Tenn., January 15, on wheat; and by Mr. C. N. Ainslie at Mesilla
Park, N. Mex., April 1, on wheat. Adults were also observed by
Mr. Urbahns at Mercedes, Tex.. February 18, damaging young alfalfa
by feeding on the leaves. At Lanes, Ga., March 3, and at Troy and
Montgomery, Ala., March 5, they were observed by Mr. Vickery
feeding on oats. Mr. George G. Ainslie observed them at Hunts-
ville. Ala., April 14. feeding on oats; at Franklin, Tenn., February
15 to 18, feeding on wheat ; and at Clemson College, S. C, February
20, feeding on oats. Quaintance reported that adults were in evi-

8 BULLETIN 5, U. S. DEPARTMENT OF AGRICULTURE.

clence at Experiment, Ga., March 1-2, and that they had become
abundant on alfalfa by March 28.^

While all of these data may at first seem of little consequence, they
bear directly, as will appear later, on what noAv seems to be the
planter's only hope of eliminating the ravages of the pest in his
cornfields. It is fair to suppose that these females deposit eggs in
the fields as soon as there is food for the larwT, and it is the larva?
from these eggs that become so destructive in the fields of young
corn, especially in the South. The reason they are not equally in-
jurious in the North may perhaps be that by the time oviposition
begins in spring and the larva^ have hatched corn has become too
advanced in growth to enable these young larva? to penetrate the
stem at the usual point of attack.

Mr. Vickery, who followed the species through the season at Salis-
bury, N. C., in 1000, settled the (juestion of the number of generations
that occur annually at that point, finding that there are two. All of
the observations of the author and those of several of the men work-
ing under his direction have shown that this is generall}^ true
throughout the country where the adult hibernates, but may not
apply in the far South, where hibernation does not take place.

Prof. Quaintance, at Experiment, in central (leorgia, noted the first
appearance of the larva' attacking corn on INIay 2. The first pupa
was found May 8. and the first adult, evidently of the new generation,
May 12.

Mr. C. L. Foster wrote as follows from Dalton, in northern Georgia,
on July 30, 1010:

I am mailing you a sample of worm that is causing great damage to the
corn crop of our country. When the corn plant is small these worms bore into
the center of the stalk underneath the soil and kill the plant by destroying the
"bud." When the plants are larger they bore into some of the larger roots,
but more generally into the stalks among the roots, which does not kill the
plant outright, but injures it so that it rarely produces ^ ^coru to amount to,
anything. The plat where these were found has been planted three times this
season, and there are very few stalks now on the plat but what have been
injured by the worms. The worms were not so plentiful on July 23 as they
were on July 6, when the samples first sent you were collected.

From the foregoing letter it would appear that the second genera-
tion of larva' were at work in late June and July in northern Georgia.

Mr. George G. Ainslie studied the larva\ at that time 3 to G milli-
meters in length, at Hurricane, Tenn., May 27 to 30, 1012. They
must have been full grown by the latter date, as none could be found
in the fields June 5, and a recently emerged adult was taken on
June 14.

The author observed full-grown larva^ attacking late-planted corn
at La Fayette, Ind., July 12, 1888, and in such enormous numbers

^ Loc. cit.

THE SOUTHEEN COEN ROOTWOEM, OR BUDWORM. 9

as to enable him, two days later, to collect nearly GOO for experi-
mentation. It was simply impossible that these could belong to the
first generation, as he liad frequently observed adults feeding on
wheat in the fields in April and early May. One beetle was observed
eating out the opening buds of a cherry tree, April 17, 1888. Be-
sides, adults were secured in early August from these larvre found
attacking corn in July. Other adults were observed in the same
locality feeding on volunteer oats, December 14, 1888. Clearly there
are two generations in the latitude of northern Indiana.

Prof. Quaintance,^ in central Georgia, found that in one case the
period from egg to adult extended from March 14 to May 21, a total
of 68 days. In another case this period extended only from April
25 to June 5, or 41 days. Mr. Kelly, at Wellington, Kans., found
that the period from egg to adult was 40 to 45 days, wdiile
Mr. Vickery, at Salisbury, in western North Carolina, found that
this period extended from August 27 or 29 to October 24, or about
58 days.

From all available information it appears that the egg period
varies greatly and may require from 7 to 24 days, the larval period
from 15 to 35 days, and that of the pupa from 7 to 13 days.

NATURAL ENEMIES.

The Biological Survey has found Dhthrotica 12-purictata in stom-
achs of the following 24 species of birds: Bobwhite, Colinus vir-
f/inianus (found in 15 stomachs, one of which contained 12) ; scaled
quail, Callipepla squamata; California quail, Loplioriyx californi-
cus; prairie chicken, Tympanuchus ainericanus ; wild turkey, Mele-
agris gallopaco; yellow-bellied sapsucker, Sphyrapicus varius; red-
headed woodpecker, Melanerpes e rytkwce phalus ; nighthawk, Ghor-
deiles virginianus; scissor-tailed flycatcher, Muscivora forflcata;
kingbird, Tyrannus tyrannus; phcebe, Sayornis phmbe; wood pewee,
Myiochanes virens; western flycatcher, Empidonax difficilis; Acadian
flycatcher, Empidonax virescens; Traill's flycatcher, Empidonax
traill'i; least flycatcher, Empidonax minimus; red-winged blackbird,
Agelaius phoeniceus ; meadowlark, Sturnella magnd; Bullock's oriole.
Icterus hullocki; cardinal, Cardlnalis cardinnlis ; rose-breasted gros-
beak, Zamelodia ludooiciana; clitf swallow, Petrochelidon lunifrons;
wliite-ejed vireo, Vlreo griseus; robin, Planestlcus migratorius.

The most efficient of the insect enemies of this pest is the fly Cela-
toria diabrotica' Shim. (fig. 2), the maggot of which develops within
the body of the adult insect, killing its host. This parasite is not
sufficiently abundant, however, to exert mucli influence in reducing
the numbers of the insect.

1 Loc. cit.

10

BULLETIN 5, U. S. DEPARTMENT OF AGRICULTURE.

As far back in the past as 1888 the author found hirvw of a click-
beetle. Dasteriiis elegans Fab., a close relative of the wireworms,
under circumstances that led him to suspect that they were feeding
on the budworm. Since that time, also, they have been taken in
association with the larvae of this species and, though never observed
in the act, it is not at all unlikely that they do feed upon and destroy
the budworm. Mr. Ainslie also encountered them associated vritli
the budworm in his investigations of the latter at Hurricane, Tenn.

REMEDIAL AND PREVENTIVE MEASURES.

After having made its way into the crown of the young corn plant
there is no remedy for the work of the pest. The shoot is ruined past
all recovery, and the plant will only throw up worthless " suckers,"

which produce no ears and scant fodder.
Fertility of the soil, or the lack of this,
does not appear to have any influence on
the amount of damage produced.

Garman ^ states that of the seriously
ravaged fields of corn examined by him
one had been grown to tobacco and an-
other to oats the previous 3'ear, while
a third had been devoted to corn. The
ravaged fields observed in Louisiana and
Arkansas by the author had all been de-
voted to cotton the previous j^ear. It
would appear, therefore, that crop rota-
tion has little if any effect in protecting
fields of corn from the attack of the larvae.
In the light of all the information at this time available it would
seem that the farmer's only hope of relief from the ravages of this
pest in the cornfields lies in so timing his planting in spring as not
to subject his crop to severe attack. Quaintance, in central Georgia,
secured eggs in March and April. 1000: Urbahns found young larvae
at Mercedes, Tex., March 1, 1000; George G. Ainslie observed larvae
attacking oats at Jackson, Miss., April 20, 1011. The author saw them
damaging corn at Somerset Landing, La., April 12, 1887. and April
27, 1888; at Madison, Ark., May 12, 1888, and at Columbia, S. C,
on May 4, 1006. At the last point the ravages of the larva? w^ere
equally as serious as had been observed years before at Somerset Land-
ing, La., and Madison, Ark., but at Columbia the writer was informed
that corn planted after the middle of May escaped injury from the
pest. Nearly all of the complaints of injuries from this budworm
coming to us from the South refer to damage to the crop early in the
season. March or April, although to the northward early May is

Fig. 2. — Celatoria diabroticw, a
fly parasite of the southern
corn rootworm beetle. Much
enlarged. (From Chittenden.)

1 Psyche, vol. 9, p. 45, 1891.

THE SOUTHERN CORN ROOT WORM, OR BUDWORM. 11

included. It would seem, therefore, that there might be a possibility
of preventing- much of the loss to corn groAvers in that section of the
country by planting corn at a date that would bring the young plants
above ground at a time after most of the eggs had been deposited,
and not so late as to invite attack from the second generation, which
is evidently abroad in the fields in late June and early July in north-
ern Georgia and in July in northern Indiana.

Unfortunately heretofore the bureau has had neither the funds nor
the men to carry out an extended investigation of this insect through-
out its range of destruction. Now, with field laboratories at Colum-
bia, S. C. ; Nashville, Tenn. ; Greenwood, Miss. ; Brownsville, Tex. ;
and a temporary field station at Lakeland, Fla. — all equipped for this
sort of work and in the hands of experienced men — we hope, with
the cooperation of farmers and planters, to learn definitely whether
it is not possible through practical measures to prevent the greater
part of these ravages, and save or greatly reduce the losses caused b}^
the budworm.

ADDITIONAL COPIES of this publication
-tX may be procured from the Superintend-
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OflBce, Washington, D. C. , at 5 cents per copy

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1913

BULLETIN OF THE

u

No. 8

Contribution from the Bureau of Entomology, L. O. Howard, Chief
September 27 1913.

THE WESTERN CORN ROOTWORM.

By F. M. WEBSTiiu,
In Charge of Cereal and Forage Insect 1 nrestiyations.

INTRODUCTION.

The western corn rootworm {Dialrroticd Jongieornis Say) derives
its common name from the fact that the larva (fig. 1) was first
observed attacking the roots of corn in the Middle West, Its larval
habits, its life cycle, and the appearance of the adult insect (fig. 2)
are all entirely different from thoso of the southern corn rootworm
{Dlahrotlca duodeclmpnnctata Oliv.), though the worms themselves
are exceedingly alike in appearance. In figure 1 the larva is ex-
tended at full length, as when feeding, having
been drawn from living individuals.

The beetles (fig. 2) in life are about the size
of the striped cucumber beetle {Dlahrotlca
vlttata Fab.), but smaller and less robust than
the southern corn rootworm, and are entirely
of a green or yellowish-green color, except the
eyes, which are black. The farmer will be
most likely to observe these feeding among
the silk of the
ears and the
pollen of corn
during late Au-
gust and Sep-
tember, though
the writer has

seen them enter houses in the country at night, being attracted by
the evening lamps. An abundance of these beetles in a cornfield
should be a distinct warning that the field should not be planted to
corn the following year, but that it should be devoted to wheat, oats,
barley, rye. or to any crop other than corn.

SEASONAL HISTORY.

The eggs (fig. 3) are minute, yellowish-wliite objects, having to
the unaided eye much the appearance of minute grains of wliite sand.
6135°— i:;

Fig. 1. — The western corn rootworm
(Diahroticii lon;jiconiis) : Larva, or
" worm." Much enlarged. (Origi-
nal.!

Fi<;. 2. — The western corn
rootworm : Adult, or
beetle ; a, claw of liind
log. Muc'.i enlarged.
(Original.)

BULLETIN 8, U. S. DEPARTMENT OF AGRICULTURE,

Pig. 3. — The western corn
rootworm : Egg. Higli-
ly magnified. (Origi-
nal.)

They are deposited mostly in late August and in September, in shallow
crevices in the ground, more often among the brace roots of the corn.
These eggs hatch the following May and June, and the larvae, always
nearly white in color, attack the roots of the corn and never burrow
into the lower stem as does the southern bud worm. (See fig. 5.)
After comjileting their growth the larva^ abandon the corn roots and
construct earthen cells in the soil, within Avhich they change to pupse
(fig. -i), which are white like the larvae, and then, during late July
and xlugust, to adults or beetles. There is therefore only one genera-
tion annually. The beetles may perhaps live
over winter in extreme southern Texas, but
they do not do so farther north, where they
are of the greatest economic importance.

DISTRIBUTION.

The species occurs from Nova Scotia south-
ward to Alabama and Mexico, westward to
southern Minnesota and South Dakota, and
thence south to southern Xew Mexico.
Curious enough, but a matter of decided economic importance,
is the fact that its area of destructive abundance does not include
all of the territory which it inhabits. The greatest destruction has
been wrought, so far as known, in Illinois, Indiana, Ohio, Iowa, Mis-
souri, South Dakota, Nebraska, Tennessee, and prob-
ably Kentucky.

HISTORY OF THE INSECT AND ITS RAVAGES.

The beetle was described in 1823 by Mr. Thomas
Say, from specimens taken by him while connected
with the Maj. Long expedition to the Eocky Moun-
tains, and its habitat was given by him as the Arkansas
Territory.^

No facts concerning the habits of this insect were
recorded until the year ISOO, when specimens of the
beetles were referred to Mr. B. D. Walsh by Prof.
W. S. Robertson, of Kansas, who found them in
large numbers on imphee or sorghum, tlieir natural home being
a large thistle. Mr, Walsh, in acknowledging the receipt of the
specimens, stated that he had taken three specimens many years
before on flowers in central Illinois.- Eight years later, in August,
1874, Mr. H. Webber, of Kirkwood, Mo., sent some larva? and pupse
to Prof. Riley, with the complaint that the former were burrowing
into the roots of his corn and doing considerable damage. In July,

'/

Fig. 4. — The west-
ern corn root-
worm : Pupa.
Much enlarged.
(Original.)

i.Tourn. Aeiid. Nat. Sci. Phila., vol. 3. p. 4(>0, 1823.
" Practical Entomologist, vol. li, p. 10, 1806.

THE WESTERN CORN EOOTWOEM.

1878, Prof. Riley ^ again received larvse, this time from Mr. G. Pauls,
of Eureka, Mo..- and from these he reared adult beetles on the 14th
of the following month.

During the spring of 1874 the writer began to collect Coleoptera
in the vicinity of Waterman, Dekalb County, 111., but during this and
the following two years obtained only a single beetle of this species.
This single specimen, taken by the writer in the summer of 1874, was
captured in a field of corn, and the failure to secure more individuals
during the next two years will indicate the rarity of the insect at that
time. Within seven or eight years, however, it had become so abun-
dant throughout the neighborhood, and indeed on the same farm,
then as now owned b}^ the writer, as to render it impossible to secure
more than a single
full yield of corn
without changing for
a year to some other
crop. Up to that
time corn had gen-
erally been success-
fully grown on the
same ground for a
number of consecu-
tive years. The
writer's observations
in Dekalb County re-
flect with surprising
accuracy the condi-
tions that obtained
throughout the corn-
growing sections of
Illinois, as shown by
the information brought together by Dr. S. A. Forbes, then as now
State entomologist ■ of Illinois. May, 1884, the writer ceased to be
connected with Dr. Forbes's office and became associated with the
Division of Entomology of this department and was soon thereafter
transferred from Illinois to La Fayette, Ind.

The principal damage, as previously indicated, is caused by the
larva?, and since 1882, in localities where no preventive measures
have been used, the damage to the corn crop has been very serious.
In 1885 Mr. Moses Fowler, of La Fayette, Inch, owner of an exten-
sive tract of land, estimated his loss during that season through the
ravages of the pest at $16,000, or about 15 per cent of the entire crop.
On the basis of this estimate the loss sustained in 24 of the corn-

1 Americnn Entomologist, vol. :^, p. 247, 1880. (Note. — See "Roots of corn injiiretl by
somp unknown insect." American Entomologist, vol. 2, p. 275, 1870. 1
- Report of the Commissioner of Agriculture for 1878, p. 208, 1879.
3 14th Rept. State Ent. HI., pp. 10-31, 1883.

5. — Work of the v.-estern corn rootworm in roots of
corn ; at right, rootworm in situ. (Original.)

4 BULLETIN 8^ U. S. DEPARTMENT OF AGRICULTURE.

produciiio- counties of that State for that one year would amount to
nearly $2,000,000.' Although the pest is much more destructive on
high or tile-drained lands, Prof. Forbes in 1886 reported serious
injury to a field in southern Illinois which had been under water for
three weeks during the spring." There is no indication that the
insect is susceptible to meteorological influences, although the effect
of its ravages is aggravated by an extremely dry season. In fact,
the extreme eft'ect of the larva upon the plants is very similar to that
of severe drought.

Under date of March 7, 1887, Mr. B. F. Ferris, Sunman, Tnd., a
close observer, communicated with the writer as follows :

There has been for a unmber of years something, I know not what, working
at the roots of onr corn, so that in some seasons the corn does not have roots
sufficient" to support it, anything like a fresh breeze blowing it down, there
being scarcely any brace roots.

Sunman is in southeastern Indiana, close to the AVliite and Ohio
River Valleys, which connect with the lower Big Miami Valley in
western Ohio, and when the writer was transferred from Indiana to
Ohio, June 1, 1891, he at once became interested in learning whether
this corn rootworm had extended its depredations into the cornfields
of Ohio. The first report of injuries came from Sater, Hamilton
•County, in the extreme southwestern part of the State, during Sep-
tember, 1892, the charge being that the beetles ate the silk from the
ears of sweet corn before the kernels had become fertilized.

A careful survey of extreme western Ohio during the summer of
1893 revealed the beetles in cornfields throughout the country drained
by tributaries of the upper Wabash River, and throughout the valley
of Big Miami River, but not beyond, to the northward or eastward.
A similar survey, made in the summer of 1894:, revealed the pest in
the region of the upper Maumee River in the northwestern part of
the State and in the valley of the Little Miami River on the east. In
1895 the pest had reached the Scioto River Valley, almost if not
quite halfway from east to west across the State, and from Columbus
southward to the Ohio River; while in the opposite direction its
range extended from Columbus more or less irregularly northwest-
Avard to the Michigan line in Fulton County. Still later it appeared
farther eastward, in the upper valley of the ^Muskingum River.
There was no guesswork in these surveys, as they were carefully made
in person by the writer, who rode over the country each year when
the adult insects were abroad, examining fields and noting the pres-
ence or absence of the beetles. The following year these observations
were verified through larvae found at work by the writer or observed
and sent to him by farmers.^

1 Indiana Agricultural Report, p. 188. 1885.

- Entomologica Americana, vol. 2. p. 174. 1886.

3 Ohio Agr. Exp. Sta., Bui. 08 pp. nO-41. maps 1-2.

THE WESTERN CORN ROOTWORM. 5

It has been thus the writer's good fortune to follow personally the
destructive spread (though not the actual diffusion) of the species
throughout tliree States and from the years 1874 to 1002. both
inclusive.^

During the years 1911 and 1912 an outbreak of this insect was
studied in the Duck River Valley, middle Tennessee, by Mr. George
G. Ainslie. In 1913 the same observer foimd the larva> attacking
corn in the bottom lands of the Tennessee River about Chattanooga,
Tenn.

The pest appears to be making its way into and throughout the
bottom lands of rivers flowing through the Southern Atlantic and
Gulf States, preciselv as it has been observed to do in Indiana and
Ohio.

DIFFICULTY IN DETECTING INJURY TO CORN.

As will have been noted, the work of the larvae is very obscure and
few farmers are likely to detect them at work in the roots during
June and July, while it would be simply impossible for the farmers,
even if they did discover them, to connect them definitely with the
little green beetles that swarm in the silk of the ears during sununer
and early faU.

FOOD OF THE BEETLES.

In the cornfield the food of these beetles is made up of corn silk
and pollen. Rarely do they eat of the unripe kernels at the tips of
the ears, and then only when birds have previously pecked into these
kernels. Outside the cornfields the writer has found them in the
blossoms of thistle, sunflow^er, goldenrod, cucurbits, cotton, clover,
and rose, and on the leaves of cucumber and beans, while the species
has been reported to him as eating into ripe apples where the skin
had been previously ruptured by other causes. Dr. Forbes has found
spores of fungi and pollen of smartweed in their stomachs. More
recently Mr. George G. Ainslie has found the beetles feeding on the
leaves of corn and on the pollen of the evening primrose and asters.

1 Changed conditions that muij hnve caused a change of haMt in the ins-ect. — As the
writer well remembers, the principal crop in many portions of Illinois, especially through-
out the praii-ie country, up to 1802 was spring wheat. Influences of tlic Civil War at
that time brought the price of pork up to a point whore its production became a most
profitable occupation for the farmer. At the same time wheat growing declined rapidly,
the acreage being devoted to corn in order to afford food for the increasing number of
hogs. In those dajs crop rotation received .scant attention from the ordinary farmer,
and corn was more often than otherwise planted year after year on the same ground.
How soon it was, after this change in the principal crop from wheat to corn, that these
beetles, attracted to the cornfields perhaps by the enormous amount of pollen found
there as well as by the equally inexhaustible food supply offered by the silk, began to
deposit their eggs and develop in these fields, it is not possible to say. We do know,
however, from the records already given, that injuries from the larva? began to be noticed
in 1874, about 10 or 12 years after this change in production of wheat and corn took
place, thus giving us at least a clue to the primary causes which seem to have changed
the food of the insect to a cultivated crop.

6 BULLETIN 8, U. S. DEPARTMENT OF AGRICULTURE.

EFFECTS OF ATTACK OF THE LARV^.

The initiiil effect of the work of the larva^ in the roots of corn is a
shortening of the ears, leaving- long tips devoid of kernels. As the
infestation and injury increase, plants fail to develop ears, and
finally a dwarfing of the stalks occurs. The appearance of the crop
is precisely the same as it would be if the land were impoverished.
Indeed many farmers, ignorant of the real trouble, claim that their
soil has " run out " and is incaj^able longer of producing corn. One
farmer insisted that his corn was damaged by careless cultivation.
P^or this reason much injury may be done l)y the pest before it is
recognized at all.

NATURAL ENEMIES.

The Biological Survey has found specimens of Diabrotlea longi-
cornis in stomachs of the uighthawk {Chordeiles virginianns) and
the wood pewee {Myiochanes virens).

The natural enemies of this species are exceedingly few, the prin-
cipal one being the parasitic fly Celatoria diabroticce Shim., figured in
Bulletin 5 of this department as an enemy of the adult of the bud-
Avorm. Mr. George G. Ainslie. however, has found that the beetles
are attacked by the so-called chinch-bug fungus, Sporotrichnm
glohuliferum. The larvae of the click-beetle Drasterius elegans Fab.
are also frequently found among those of this species and may destroy
some of them.

CROP ROTATION AS A PREVENTIVE MEASURE.

In all of the history of this, one of the most destructive pests in
the cornfield, there is not an instance on record in which corn has
been injured when planted on land following a crop of small grain,
such as wheat, rye, barley, or oats. Except on grounds subject to
overflow, w^hich prevents a rotation of crops so that corn is or must
be grown for two or more successive years, this pest is one of the
easiest to control. Two instances only need be cited in order to prove
this fact.

Ill Dekalb County evidence of the protection afforded by the rotation of
crops is afforded on a much larger scale. On n farm of 4,600 acres owned by
Hon. Lewis Steward, near Piano, rotation of crops has been the regular rule;
1,600 acres of this land was planted to corn this year, and 700 acres were care-
fully examined by Mr. TV^ebster. In August only 10 acres of this entire tract
was found affected by tlie corn rootworm, and this was where, in the rear-
rangement of the tields, a small tract of ground happened to have been planted
to corn the previous year. All about Mr. Steward's place, on farms where
I'otation was not systematically practiced, the damage done was serious and
general.*

1 Quotation from 14th Itopt. State Ent. UI.. p. 29, 1885.

THE WESTERN CORN ROOTWORM. 7

The second instance is that of Mr. Moses Fowler, previously men-
tioned on page 3. At the time referred to (1885) the Fowler estate,
comprising a single tract of about 18,000 acres, near Fowler, Ind.,
was farmed by tenants and there were about 10,000 acres of corn
growing on the premises. Some of the fields were but slightly in-
jured and these were such as had either produced oats or grass wuthin
two or three years. Other fields were damaged from "10 to 75 per
cent or more. Mr. Fowler, the following spring, directed his tenants
to sow 5,000 acres of the worst infested fields to oats and the re-
mainder of the 10,000 acres were sown to oats the second year.
Thereafter no attempt Avas made to grow corn two successive j^ears
on the same ground, and as a result the pest was eliminated and no
further damage was sustained.

AAliat one man can do, who has control of thousands of acres, a
community can also accomplish if the people combine and follow a
similar course of procedure.

Dr. Forbes, in his thorough and painstaking investigations of the
insect in Illinois, has found many similar instances of the efficiency
of crop rotation in eliminating the insect from cornfields. These
data have been supplemented b}^ later studies of the writer and by
other observations made by him extending over the same period in
other States; so that there is no longer the slightest doubt of the
efficiency of this measure, which is now considered essential to good
farming.

POSSIBLE EXCEPTIONS TO EFFICIENCY OF CROP ROTATION.

In this period of nearly 10 years only a few possible exceptions to
the effectiveness of crop rotation have come to the wa'iter's knowledge.
One of these came from a farmer in northern Illinois Avhom the
writer knew personally and who in 1886 complained of the attack of
these larvae on his corn, which was planted on ground that had been
devoted to clover and timothy the year previous. This farmer was
familiar with the pest and its work and sent specimens of the larvae.
The only explanation that could be offered for this unusual injury
was that the beetles forsook the cornfields after the pollen had ceased
to fall from the tassels and the silk of the ears had become too dead
and dry to afford them food, and that some of the females which had
not already finished oviposition made their way to the clover field,
fed in the blossoms, and oviposited in the soil, thus giving rise to the
larva^ that the next year attacked the corn which followed the
clover crop in this field.

The second complaint came from a farmer in Indiana who for two
years had fed considerable corn fodder to stock in a pasture of blue
grass and timothy. After plowing up this ground and planting it

8 BULLETIN 8, U. S. DEPARTMENT OF AGRICULTURE.

to corn he reported that the crop was attacked by these worms. In
this case no specimens accompanied the complaint.

It goes without saying that the beetles are found and must develop
where very little corn is grown, but time hag shown that there is
little danger to be apprehended from these.^

Quite recently Mr. C. N. Ainslie, of this bureau, has found slight
injury to corn in fields in Nebraska where this crop has followed
small grain.

DEPREDATIONS ON LAND SUBJECT TO OVERFLOW.

The frequent submergence during fall, winter, or early spring,
even for weeks at a time, of fields in which the eggs of these beetles
have been deposited does not seem to ail'ect such eggs in the least.
Throughout the country north of the Ohio and Arkansas Eivers it
is these low bottom lands that are kept most continuously in corn,
and therefore it is here that in later years the danger from the pest
^s greatest. This is not, so far as now known, true of the lower
Mississippi A^alley, for the reason that planters there rotate with
cotton, otherwise the ravages of the insect would probably l)e felt
there as well as in the more northern States, as the writer has ob-
served the beetles feeding on the pollen of the cotton bloom. Thus
we see that throughout the country it is only where crop rotation
is neglected that damage is at all to be feared.

1 Possible origin of a corn-feeding race. — It will be noticed tliat Mr. B. D. Walsh, the
first State entomologist of Illinois, found three of these beetles in central niinois many
years prior to 1800 (Practical Entomologist, vol. 2, p. 10, 1866). Mr. Ottoman Reinecke,
of Buffalo, N. y., wrote the author in 189" chat he had, prior to 1880 and for some
years, collected the beetles in abundance on willow along the margin of a creeU near the
"city during July and August ; while :Mr. W. H. Harrington wrote the author years ago of
his finding them in Neva Scotia. Thus it is clearly shown that the eastward advance each
year, as previously recorded, does not represent the real advance of the species. It rep-
resents the advance of a race that feeds on the pollen and silk of corn, some of whose
larva> develop in the roots, the adults from these spreading from field to field and under
favorable conditions giving rise to myriads of worms that feed on the roots and destroy
the crop. The origin of this race appears to have been the prairie country in Illinois,
which in many places begins at the Mississippi River and extends into northwestern
Indiana. It is true that the first reports of injury to the roots of corn by the larvae
came from Eureka and Kirkwood, Mo., both of which are near St. Louis ; but just across
the Mississippi River in Illinois are wide stretches of prairie country which near the
river are subject to overflow.

ADDITIONAL COPIES of this publication
-l\. may be procun d f'-om the Superintend-
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WASHINGTON : GOVERN.MENT PRINTING OFFICE : 1913

BULLETIN OF THE "^

No. 14

Contribution from the Bureau of Entomology, L. O. Howard, Cliief
February 28, 1914.

(PROFESSIONAL PAPER.)

THE MIGRATORY HABIT OF HOUSEFLY LARV^ AS INDICAT-
ING A FAVORABLE REMEDIAL MEASURE. AN ACCOUNT OF
PROGRESS.

By Robert H. Hutchison,
Scientific Assistant.

INTRODUCTION.

In the proceedings of the tliird meeting of the General Malarial
Committee held at Madras in November, 1912, there is given a
surmnary of a paper on "Insect Psychology" by Prof. L. M. Howlett.
From liis experiments with fruit flies, the stable fly, and mosquitoes
he comes to the conclusion that "we must regard insects not as
inteUigent beings consciously shaping a path through life, but as
being in a sort of active hypnotic trance." Also, that "once we
discover the stimuli or particular conditions wliich determine a
mosquito's actions we hold the key to the position, since we can
then apply our knowledge to the mosquito's undoing." The second
statement might have been made as general and inclusive as the
first. One often hears expressed a general proposition to the effect
that the problem of the control of any insect is very largely a prob-
lem of its behavior. If its habits are known, some means of control
are usually not far to seek. Thus in the warfare against the common
housefly there are two important lines of attack based on a knowledge
of the habits of the adults. In the first place, advantage is taken
of their feeding and drinking habits in the use of such things as
sour milk, formalin and milk, beer and sugar, the fly poisons, etc.,
as bait for traps or as poisons. Secondly, a knowledge of the egg-
lajdng habits of the female leads to the use ol covered fly-tight
receptacles for manure, garbage, or other fermenting material.
Both of these methods are based on a knowledge of the habits of
the adults. The question now presents itself. Is there any phase
of the behavior of the larvae wliich may afford a line of attack ? Do
they have any characteristic habit of which advantage may be taken
in attempts to destroy them ?

26069°— 14

2 BULLETIN U, U. S. DEPARTMEXT OF AGRICULTUEE.

THE MIGRATORY HABIT

One need make only a few observations on the behavior of lioiisefly
IhTYSd to discover an excellent example of what Prof. Hewlett calls
'■■a sort of active hypnotic trance." This is to be found in the
migratory habit wliich is so much in evidence during the prepupal
stage. The habit has long been known and repeatedly mentioned
in the literature. Thus Newstead (1907)^ found that ''deep down
at the sides, in the cooler portions of the receptacles, the pupa or
chrysalis stage occurred in enormous numbers, looking like small
heaps or collections of reddish berries."

Griffith (1908) found that "the larvae remained in the hottest
part of the heap, but the pupae were all found near the surface where
it was cooler."

Jepson (1909), in certain rearing experiments in which moist
bread was used as food, found that "the larvae rarely left their
feeding ground till fully fed, when they left the moist mass of bread
for the surrounding dry area and there pupated."

Herms (1911) states that "the growing stage requires from four to
SLX days, after wliich the maggots often crawl away from their
breeding places, many of them burrowing into the loose ground
just beneath the manure pile, or crawhng under boards or stones
or into dry manure collected under platforms or the like. * * *
The larvae often pass three or four days in the prepupal or migrated
stage before actually pupating."

R. I. Smith (1911) says "it was very apparent that the maggots
wliich swarmed through the manure were inclined to congregate
in certain corners or crevices and pupate in a mass. * * * Scat-
tered pupa3 were discovered around the edges of the piles of cow
manure and even in the soil underneath where the maggots had
burrowed before pupating."

Hewitt (1912) states that "when full grown the mature larva
usually leaves the moist situation in wliich it has developed for
one of a drier nature, often crawhng for several yards in search of
some dry and sheltered crevice. Here it rests for a short time
preparatory to changing into the pupal stage."

If any further evidence were needed to demonstrate such an
habitual mode of action I might mention the following observations:
During the past few months it has been my duty to assist in carrying
out an extensive series of experiments in testing the value of various
chemicals in treating manure with a view to the destruction of the
larvae present. The manure is placed in large cages and the chem-
ical to be tested is sprinkled over it. The bottom of the cages con-
sists of a galvanized iron pan with sides 1 foot high. In the floor
of the pan are nine small holes. The sides of the cages above the

' Numbers in parentheses refer to dates in the bibliography, p. 11.

THE MIGKATOEY HABIT OF HOUSEFLY LARViE. 3

pan are of two layers of screen wire 2 inches apart. Now it was
found in the very first experiments that larvse were escaping from
the cages, and it was seen that they found their way put through
the holes in the floor of the cages and also through the screens at
the sides. The numbers so escaping were surprising. It often
happened that several hundred crawled out of the cage during 24
hours. They were found in the vessels placed beneath the cages to
catch any drippings. By day the light was sufficient stimulus to
prevent them from crawling out at the sides, but at night they were
actually seen, with the aid of a flash light, making their way through
both thicknesses of screen wire and dropping into the vessel below.

Moreover, in examming manure heaps on the open ground I have
many records showing this' "tendency to congregate" at the edges
of the piles near the ground. About two cartloads of horse manure
had been piled out on the open ground for five or six days during
August, and at the end of this time it was hauled away. I examined
the gi'ound where the heap had been and found many pupae, not
in the center of the area formerly covered by the heap, but around
the margm. Some were found on the surface, doubtless shaken out
of the manure at the time of removal; others were found buried a
half mch or more in the soil, where the larvse had burrowed just
previous to pupation.

In another case some 50 cubic feet of manure had been heaped
up in a pile the base of which covered an area about 4 feet square.
After the pile had stood three days larvse were found swarming
in the warm, moist parts of the heap near the top and some distance
in from the sides. After eight days the entire pile was torn apart
and gone over carefully m search of pupse. None was to be found
in the upper parts of the heap where I had previously seen great
numbers of larvse. In fact none was found until the very lowest
layers were exposed. Here about 9,000 were collected. Not
more than 100 were found below the sod. The mass of pupas were
scattered in little heaps about the margin. They were just outside
the moist area of the manure, yet sufficiently protected from drying
and sunlight by the overhanging straw. The explanation of their
presence in such a position is, of course, that the larvse, just before
pupating, had migrated from the moist feeding grounds to a drier
region more favorable to the resting stage. The examination of
many other piles of manure showed the very same conditions existing,
the only difference bemg in the number of pupse collected.

Altogether some 50 or more heaps of manure on open ground
have been examined. Each one contained from 40 to 50 cubic
feet of manure. Some contained much long straw, others very
little straw or beddmg of any Idnd. The puparia are not hard to
find nor hard to collect because of their occurrence in masses at the

4 BULLETIN 14, U. S. DEPARTMENT OF AGRICULTURE.

edges of piles. Here are some of the figures obtained from a count
of the pupae collected from different piles: 7,000, 1,500, 10,000, over
12,000, 4,500, 6,000, 6,700, 30,000, etc.

In a recent article in the American Journal of PubUc Health, I^evy
and Tuck make the following statement : " We therefore announce the
biological fact that the house fly does not pupate in manure if the
full-grown larvae can find any means of reaching and entermg the
earth." They claim that "the adult larvae regularly leave the manure
heap" and that they "enter the earth whenever it is possible for
them to do so." To be sm-e, larvae may and often do burrow into the
ground before pupatmg — witness Dr. Terry's observations at Jack-
sonville, Fla., where he found larvae and pupae m the ground of soil-
floor stables — but that they do so regularly is open to serious question.
The figures given above are for puparia collected above the surface of
the ground and in the manure. After the removal of the heaps,
examination of the ground revealed only a very small percentage
beneath the surface. The fact that some were found there shows
that it was not the compact nature of the soil which prevented the
majority from burro whig and that there was no reason why all could
not have done so if such were their regular habit. It would seem
that Levy and Tuck have put too much emphasis on this one point,
A broader view, includmg all the phases of the migration of these
creatures, is necessary and wiU not detract from the importance or
value of the "maggot trap" which they have devised.

It is quite certain that the migrating habit is deeply ingrained and
highly characteristic of housefly larvae. A consideration of the known
facts in the case will enable one to draw some inferences as to "the
stimuli or particular conditions" which determine this mode of
action. It has been noted that a sort of "wanderlust" seizes the
larvae just before pupation. It must be, therefore, that the migration
is initiated in response to internal stimuli incident to the maturing
of the larval stage and the onset of the metabolic changes preparatory
to the transformation to the pupal stage. The com-se and direction
of their travels are determined largely by external stimuH. It is quite
evident that as pupation draws near they flee the very moist regions
of a manure heap and seek the comparatively dry regions. If no such
dry places are to be found in the manure, they wiU leave it to pupate
in the ground or in cracks or crevices, imder boards or stones, in loose
material of any kind. Dr. Terry found both larvae and pupae in the
soil of du't-floor stalls. The larvae were found in that part of the
floor kept moist by the urine, while the pupae were found m a ling
in the drier soil outside the moist center. Fm-ther proof that moisture
acts as a stimulus in determinmg their choice of a place for pupation
is given below.

THE MIGhATORY HABIT OF HOUSEFLY LARV^. 5

It is well known that they avoid light, and the rapidity with which
they disappear from view when exposed to hght through the disturb-
ing of their feedmg grounds is a famihar sight. The observation
mentioned in which larvae were seen crawling out through the screened
sides of cages at night, but never durmg the day, is a case in point.

They avoid the extremely hot portions of manure heaps. Ther-
mometers inserted from 6 to 12 inches toward the center of a heap
will register an5rwhere from 110° F. to 170° F., which, of course,
would be fatal. The hotter the pile the nearer the surface are the
larvae to be found. They also avoid the moldy parts of the heap.
They seek, as it were, the safety of the middle region between the
heat and mold of the center and the exposure to sunhght and dryness
of the exterior. Doubtless other conditions also have an influence
in determhiing their actions.

The habit of seeking the comparatively dry regions near the edge
of manure heaps at the time of pupation is an adaptation of great
advantage in that the adult fly at the time of emergence is thus
afforded an easy path to freedom. It prevents the drowning of the
imagines and insures the quickest possible expansion and drying of
the wings. At least this is the teleological explanation. Yet it can
not be claimed that these are intelligent acts, nor that the future is
consciously provided for. We have here indeed a ''battaUon of
somnambuUsts " acting in bhnd response to various internal and
external stimuU.

THE BEARING OF THE MIGRATORY HABIT ON THE PROBLEM

OF CONTROL.

So far as I have been able to determine. Levy and Tuck were the
first to take advantage of the migratory habit in an attempt to destroy
the maggots. In their paper pubUshed in July, 1913, they report
two experiments. In the first they placed manure in a barrel in the
bottom of which several holes had been bored, with the result that
on the following day thousands of maggots were found in the tub
placed beneath, and the number seemed to increase for three days.
In a second experiment the bottom of the barrel was replaced by
stout wire gauze. The results of this trial are not given.

It was not until the beginning of November that I learned of their
work, and it was near the end of the month before I had an oppor-
tunity of reading the article. I had already carried out two experi-
ments during the summer at Ai-lington, Va., and others during the
fall at Audubon Park, New Orleans, La. The possibihty of taking
advantage of the migrating habit was suggested to me by experience
with larvae escaping from cages used in other experiments. The
results of the experiments were beyond my best expectations, and

6

BULLETIN 14, U. S. DEPARTMENT OF AGEICULTURE.

ill the hope that they may be of some interest to others they are here
reported in some detail.

A large galvanized iron pan, measuring 5 by 3 feet, with sides 4
inches high, was made. In this stood a container on legs 8 inches
high. Tliis container measured 4 by 2 by 2 feet. The sides and bot-
tom were of heavy wire, ^-inch mesh, supported by a light wooden
framework. Twelve cubic feet of manure well infested with eggs and
larvae were placed in this container and sprinkled with water. Water
was also poured into the pan below to the depth of about 1 inch.
Surrounding and covering both pan and container was a fly-tight
inclosure made of a large cage, 6 by 6 by 6 feet. This prevented
further infestation of the manure, and an arrangement of traps at
the top of the cage made it possible to capture and keep a record of
any flies that might emerge. At the time for the emergence of flies
the' sides of the cage were darkened Avith black cloth in order to
drive the flies into the traps at the top. Each day the larvae were
collected from the pan and counted, and each day the manure in
the container was sprinkled thoroughly with water and the pan was
washed out and again partly filled with water to drown the larvae
wliich fell into it. The records of Experiment No. 1 are summed up
briefly in Table I.

Table I. — Migratory habit of housejly larvx; Experiment No. 1.

Dale.

Larvfe
collected
from pan.

Flies from
traps.

Date.

Larvae
collected
from pan.

Flies from
traps.

1913

Aug. 27

28

29

30

31

Sept. 1

2

3

4

5

337
715

1,550

1 10, 000

18,000

2,160
670
263

(=)
304

1913
Sept. 6

8
9
10
12
15

0

88
102
23
19
9
5
6

3

18
8
22

23,999

303

1 Approximate.

* Collected on following day.

A few flies at the time of emergence fefl into the water of the pan
and were drowned. Aflowing for these and for the few which may
have escaped from the cage during the opening and shutting of the
door, the total number of flies may be placed at 350. It will be seen
from these figures that out of a possible total of 24,350 24,000, or a
little more than 98 per cent, were destroyed through the catching of
the larvae in the manner described.

A second experiment was started on September 16. The manure
used was from the same source as in the first experiment and con-
tained practically the same proportion of straw. The same amount
was used, viz, 12 cubic feet. The only respect in which this experi-

THE MIGRATOKY HABIT OF HOUSEFLY LARVJE.

ment differed from the first was in the fact that the manure in the
container was not sprinkled with water at any time, except for a
light shower on September 19 and another on September 22. Much
of tills rainfall failed to reach the manure in the container because of
the covering of the cage. A comparison of the results of this experi-
ment with those of the first indicate the importance of moisture as a
stimulus.

Table II. — Migratoi-y habit of housefirj larvse; Expervnient No. 2.

Date.

Larvae
collected
from pan.

Flies
caught
in traps.

Date.

I>arv8e
collected
from pan.

Flies
caught
in traps.

1913
Sept. 17
18
19
21
22
23
24
27
28
29

15
132
168
894
427

1913
Sept. 30
Oct. 1
2
3
4
6
7
8

64
80
125
52
78
84
44
22

35
0

« "

43
33

1,671

668

Allowing for the few larvae and adults which may have escaped,
the totals may be given in round numbers as 1,700 larvae and 700
adults. Thus from a possible total of 2,400, 1,700, or about 71
per cent, were destroyed. In passing it is unnecessary to point out that
here 700 flies did pupate in the manure in spite of the fact that they
had every opportunity to leave it.

With the approach of cold weather the work against the housefly
was transferred to the experiment station at Audubon Park, New
Orleans, La. Some other experiments of a similar nature were car-
ried out here with smaller containers and cages. The strong wu-e
baskets of the kind commonly seen in markets and stores for the
display of fruits and vegetables made first-rate "maggot traps."
The baskets used were 16 inches in diameter and 16 inches high
and stood on legs 9 inches high. A galvanized-iron pan 2 feet square
was made for this to stand in, and over all this was placed a cage
consisting of a light wooden framework covered with black cloth.
The top of the cage was covered by boards in which was an opening
for the attachment of flytraps.

The third experiment was started on November 13. The basket
was filled with manure taken from stables on November 12. The
manure, which contained very little straw or bedding of any kind,
was packed firmly in the basket and sprinkled with 4 quarts of water.
The iron pan below was partly filled with water. The cage with its
traps was not put in place until November 18, thus exposing the
manure to possible infestation for a period of five days. The manure
was sprinkled daily as long as larvae appeared.

8 BULLETIN 14, U. S. DEPARTMENT OF AGRICULTURE.

Table III. — Migratory habit of housefly larvx; experiment No. S.

Date.

Larvae
collected
from pan.

Flies
caught
in traps.

Date.

Larvae
collected
from pan.

Flies

caught

in traps.

1913.
Nov. 14
15
16
17
18
19
20
21
22
23
24
2.5
26

162

656

1,950

2,650

1,240

40

(>)

12

0

0

0

0

1913.

Nov. 27

28

29

Dec. 1

2

3

4

5

6

3
2
2
2
8
5
6
15
10
3

7

0

0

0

0

4 1

2

6,710

69

' Collected on following date.

Out of a possible total of 6,779 there were destroyed 6,710 larvsB,
that is to say, about 99 per cent were destroyed before they reached
the pupal stage.

The percentages obtained in these experiments clearly demonstrate
the habitual nature of the migration. They also demonstrate the
efficiency of the maggot trap which is designed to take advantage of
this mode of action. Tlie question immediately arises whether the
trap which appears so successful in an experimental way on a small
scale can be adapted to the handling of manure in a practical way and
on a large scale. Every consideration points to the probability that it
can and that it will afford "an additional weapon of great value."
However, the final verdict as to the value of the maggot trap must
wait upon the solution of certain practical problems. To point out
some of these here is to suggest lines for further investigation.

(1) In the first place, there must be determined what form, size,
and construction of trap will give the best results. The answer to
this will depend largely on the particular conditions obtaining at any
given stable, such as the amount of manure produced daily, the
arrangements for drainage, etc. It will also depend on the answer to
the following problems :

(2) How deeply may manure be heaped in a trap without inter-
fering with the migration ? It will probably be found that the depth
will make little difference, provided that the manure is kept moist,
and provided that avenues of escape are afforded at the sides as well
as at the bottom. The importance of providing a way of escape at the
sides was not taken into consideration by Levy and Tuck in their
preliminary experiments.

(3) How long must manure be kept in a maggot trap before it is
entirely free from larvae ? This is a very important question from a
practical standpomt, and one will find scant suggestion as to the
answer in the literature on the life history and habits. The housefly

THE MIGEATOKY HABIT OF HOUSEFLY LARViE.

9

breeds preferably in horse manure, but it has never been determined
just how long a given lot of manure continues to be an attractive place
for egg laying, nor for how long a period fly larvae will continue to
appear in it. It is obvious that the maggot trap would not be prac-
tical if the infestation of the manure were daily renewed for a long
time. Under ordinary conditions the drying»of the surface of a heap
of manure probably limits the period of egg laying to the first day or
two of exposure. But in a maggot trap the manure must be kept wet
in order to msure the greatest amount of migration. Would not such a
moist surface be daily reinfested and maggots continue to appear in
the manure as long as any fermentation were in progress? As a
matter of fact, the period of infestation appears to be rather short,
and even under the most favorable conditions maggots will rarely be
found in a given lot of manure after 10 or 12 days' exposure. In
support of this claim some experimental data may be given here.

A fourth experiment was carried out in the same manner as exper-
iment No. 3, except that no cage was used to cover the trap at any
time. The manure in the basket was thus continuously exposed to
flies and the surface was kept moist by daily sprinkling. The larvae
were removed from the pan each day and counted and the pan was
again partly filled with water. The manure used was taken from
stables on November 12 and the experiment started on the same date.
Larvae began to appear in the pan on November 13 and continued
daily to the 24th, as shown in Table IV,

Table IV. — Migratory habit of housefly larvae; Experiment No. 4-

Date.

Larvae
caught.

Date.

Larvae
caught.

Nov. 13

14

Nov. 20

1,040

14

2,230

21

560

15

16,000

22

465

17

15,000

23

140

18

2,530

24

36

19

2,070

1 Approximate.

The manure contained little straw or other bedding and was very
attractive to the flies as evidenced by the heavy infestation (about
20,000 from a little more than a bushel of manure). Yet no larvae
were to be found in the manure after 12 days.

Examination of heaps of manure on open ground has shown in
many cases that at the end of eight days only pupae were to be found
in the manure. Even in cases where the manure was especially
attractive to the flies, by reason of active fermentation and the
absence of straw, all were found to have reached the pupal stage by
the tenth day. Any device for applying the principle of the maggot
trap on a large scale must take this time factor into consideration.

10 BULLETIN 14, U. S. DEPARTMENT OF AGRICULTURE.

(4) The disposal of the maggots is another practical consideration.
If the larvae were allowed to drop to the ground they would burrow
into it to pupate there and nothing would be gained. It would be
necessary to have some sort of vessel, e. g., a concrete basin, beneath
the trap. This should have vertical sides and contain an inch or
more of a weak disinfectant or of water covered with a film of oil.
If such a basin were connected with a sewer or cesspool the maggots
collecting in it could be flushed out each week without the necessity
of handling them in any way and without any offensive decomposi-
tion.

That the maggot trap possesses certain advantages is obvious and
ought to lead to many attempts to develop it along practical lines.
Cheapness would be one of its strong points. Practically the only
cost would be the initial one for the construction of the trap and of
a basin or receptacle for catching and disposing of the maggots.
Very little additional time or labor would be required in operating
it. The sprinkling of the manure would be a very small part of the
daily routine of removing the manure from the stables. Proper
arrangements for the disposal of the maggots would require only a
few minutes' attention at long intervals.

Incidentally it may be noted that the maggot trap offers a conven-
ient and easy means to the investigator or teacher who wishes to
collect coprophagous larvae in large numbers. In the experiments
just reported the larvae of Musca domestica L. were the most numer-
ous, but in addition there were also collected larvae of Stomoxys
calcitrans L., of Homalomyia, of certain Sarcophagidae, and doubtless
of others. The total numbers collected were so large that no attempt
was made to determine the relative abundance of the various forms.

SUMMARY.

Observations and experiments show that the migratory habit is
deeply ingrained and highly characteristic of housefly larvae.

The migratory habit appears in the prepupal stage in response to
various internal and external stimuli.

Of the external stimuli, moisture is perhaps the most important in
determining the direction of their travels and the choice of a place for
pupation.

The migratory habit is an adaptation of gi'eat advantage in that it
insures to the issuing adult the easiest and quickest escape.

This deep-seated habit offers an important point of attack in the
attempts to control the pest.

Experiments with maggot traps show that 98 or 99 per cent of the
total number of larvae can be made to leave the manure, provided it
is kept moist. Even from comparatively dry manure as many as 70
per cent can be destroyed.

THE MIGRATORY HABIT OF HOUSEFLY LARV^. 11

The development of the maggot trap into an efficient weapon in the
warfare against the housefly involves the working out of certain
practical pomts, viz, the size and structure of the trap, the time nec-
essary to keep the manure in the trap to rid it of maggots, the disposal
of the larvae, etc.

REFERENCES TO LITERATURE.

Griffith, A. 1908. The life history of house-fliei^. Pub. Health, London, v. 21,
p. 122-127, May.

Herms, W. B. 1911. The house fly in its relation to public health. Univ. Cal. Col.

Agr. Exp. Sta., Bui. 215, p. 513-548, 15 figs.. May.
Hewitt, C. G. 1912. House-flies and How They Spread Disetise. Cambridge.

122 p., illus. (Cambridge manuals of science and literatuie.)
HowLETT, L. M. 1913. Insect psychology. Proc. Third Meeting of the General

Malaria Committee held at Madras Nov. 18, 19, and 20, 1912. Simla, p. 32-33.

Summary of paper read at this meeting.

Jkpson, J. P. 1909. Some observations on the breeding of Musca domestica during

the winter months. Rpts. to the Local Govt. Bd. [Gt. Brit.] on Pub. Health

and Med. Subjects, n. s. no. 5, p. 5-8.
Levy, E. C, and Tuck, W. T. 1913. The maggot trap — a new weapon in our warfare

against the typhoid fly. Amer. Jour. Pub. Health, v. 3, no. 7, p. 657-()60, illus.,

July.
Newstead, Robert. 1908. On the habits, life-cycla and breeding places of the

common house-fly (Musca domestica, Linn.). Ann. Trop. Med., Liverpool, v. 1,

no. 4, p. .507-520. pi. 44^9, Feb. 29.

Reprinted from Preliminary report issued by the Health Committee of the City of Liverpool, Oct.
3, 1907.

Smith, R. L 1912. The house fly (Musca domestica). No. Car. Agr. Exp. Sta., Col.

Agr. & Mech. Arts., Ann. Rpt. 34, p. 62-69, figs. 13-14.
Terry, C. E. 1912. Extermination of the housefly in cities; its necessity and

possibility. Amer. Jour. Pub. Health, v. 2, p. 14-22, Jan.

o

*3tX/'.<y^W^ .

BULLETIN OF THE

No. 15

Contribution from the Bureau of Entomology, L. O. Howard, Chief.
October 16. 1913.

A SEALED PAPER CARTON TO PROTECT CEREALS
FROM INSECT ATTACK.

By William B. Parker, Entomological Assistant.
ECONOMIC IMPORTANCE OF THE PROBLEM.

During an investigation of the insects attacking dried fruits at
Sacramento, Cal., during 1912, the infested condition of packed
cereals was brought to the writer's attention. The economic impor-
tance of these infestations is greater than at fu^st appears. The pur-
chaser usually returns infested packages to tlie grocer. The grocer
returns them to the mill where they were prepared. The mill screens
the cereal and seUs it as feed. Thus the condition of the cereal itself
is the cause of a disagreeable feeling on the part of the consumer and
occasions a loss of time to the gi'ocer and a considerable loss finan-
cially to the miller.

Besides this intrinsic loss, the consumer may demand of the grocer
another "brand" in the hope of fuiding a cereal which is not infested
by insects, or, by jumping to the sudden conclusion that all cereals
are infested during the summer, may forego the use of breakfast
foods for a time. The exact financial loss due to these conditions
can not be accurately determined, but extensive observations lead
to the belief that it is much greater than most millers suppose.

PRELIMINARY OBSERVATIONS.

Examinations of infested packages taken in grocery stores, ware-
houses, and mills showed that the majority of infestations com-
menced at the ends of these packages, or where a small hole had been
broken in the edge, due to rough handling. The cereal in these pack-
ages was sterilized prior to being packed, so that the insects wliich
caused the infestation must liave deposited then- eggs after, or shortly
before, the cereal was packed. The presence of the confused flour
beetle (Tribolium confusum Duv.) inside of the ends and the presence

6802°— 13

BULLETIN 15, U. S. DEPARTMENT OF AGRICULTURE.

of small openings at the corners of many packages led to the con-
clusion that if cereals were run directly from the sterilizer into cartons,
which in turn were properly sealed, infestation would not in most
cases take place. This theory was strengthened by statements from

grocers to the effect
that certain packages
whicli were carefully
sealed were not re-
turned to them be-
cause of the presence
of insects.

INSECTS CON-
CERNED.

Fig. 1. — The Indian-meal moth (Plodia inter punctella): a, Moth; b,
pupa; c, larva; /, same, dorsal view; d, head, and e, first abdominal
segment of larva. /, Somewhat enlarged; d, e, more enlarged.
(After Chittenden.)

There are several
insects which attack
stored cereal prod-
ucts. Among the more important are the Indian-meal moth (Plodia
interpu7ictella Hiihn.) (fig. 1), the Mediterranean flour moth (Ephestia
Icuehniella Zell.) (fig. 2), the meal snout-moth (Pyralis farinalis L.),
the saw-toothed grain beetle (Silvanus surinamensis L.), the confused
flour beetle (Tribolium. confusum Duv.) (fig. 3), the granary weevil
( Calandra granaria L. ) ,
and the rioe weevil
(Calandra oryza L.).
These are the principal
insects which are likely
to infest packed cereals.
Tliere is an errone-
ous opinion with some
people that the cereals
become infested by
spontaneous genera-
tion. This, however,
is impossible; and when any insects are found in packages it is because
the eggs, larvae, or adults have gained access to the cereal after it
has been sterilized.

EXPERIMENTS IN CALIFORNIA.

Using the foregoing observations as a basis, the foUowing experi-
ments were conducted, the idea being to test tlie efficiency of a cheap
sealed carton.

A cereal was sterilized to such an extent tliat when it was placed
in a package the temperature developed was 180° F. The packages
themselves were sterilized before being filled, but had there been any

Fig. 2.— The Mediterranean Qonr moth ( Ephestia kuehniella): a. Moth;
6, same from side, resting; c, larva; d, pupa; c, abdominal segments
of larva. a-tZ, Enlarged; c, more enlarged. (After Chittenden.)

A SEALED PAPER CARTON TO PROTECT CEREALS. 3

insects or eggs in tlieni tlie heat from the cereal would undoubtedly
have killed them.

When the ends of the packages were being fastened, the glue was not
placed near the corners, so that if it were possible to leave an opening
there by accident, the opening would be left in this experiment. All
of the packages were regularly closed by gluing the ends, but some of
them were covered by a piece of label paper (fig. 7) so that there were
no openings where an insect, could enter without piercing the label.
Some of the labels were put on with glue and some with flour paste.

Eighteen of these packages, nine labeled and nine not labeled, were
distributed in two wooden boxes. Between them flour and meal that

Fig. 3.— The confused flour beetle ( TriboUum confusum): a, Beetle; b, larva; c, pupa; d, lateral lobe of
abdomen of pupa; e, head of beetle, showing antenna; /, same of T. ferrugineum. a-c, Much enlarged;
d-f, more enlarged. (After Chittenden. )

were badly infested by the confused flour beetle, the saw-toothed
grain beetle, and the Mediterranean flour moth were packed. This
infestation of the boxes was very carefully done, and when the experi-
ment was observed on November 10, 1912, the outsides of all of the
packages were literally alive with insects. The condition of the con-
tents of eight of them is recorded in Table I.

Table

I. — Recorded conditions of infestation or noninfestation found in packages of cereal
opened Nov. 10, 1912.

No. of
pack-
age.

Not labeled.

Label pasted.

Isabel glued.

1

2

do . .

3

do

4

do

5

No infestation

do

6

7

No infestation.

g

Do.

A similar observation was made on January 24, 1913, the results of
which are shown in Table II.

BULLETIN 15, U. S. DEPARTMENT OF AGEICULTUEE.

Table II. — Conditions of infeslaiion or noninfestation of 10 packages of cereal left until

Jan. 24, 1913.

No. of
pack-
age.

Not labeled.

Label pasted.

Label glued.

9

Infested, containing web and adults

10

. . . do

11

do

12

do

13

do

14

No infestation

do

15

16

17

Do

IS

Do.

The results of this experiment seem

Fig. 4.— Results of experiments with cartons. Tlae one on
tiie left shows severe infestation; the one on the right had
a thin label pasted on the outside and is not infested. The
webs and adults of the infesting insects are shown on the
outside of both cartons. (Original.)

of severe infestation the ordinary paper
while the sealed carton will not.

very conclusive. Figure 4
shows the relative infestation
on the outside and inside of
the labeled and nonlabeled
packages. These packages
were all placed under the
same conditions and given
every chance to become
infested.

The thorough infesta-
tion of nonlabeled pack-
ages and the absence of
infestation in the labeled
packages clearly indicate
the efficiency of the label in
preventing the insects from
entering the cartons.

These experiments do not
prove that insects are in-
capable of boring into the
carton, thus infesting the
cereal, but they do prove
that when placed in regions
carton will become infested

WHERE INFESTATION TAKES PLACE.

In the process of sterilization the cereal is heated to a sufficiently
high temperature to cause the death of all insect life, but following
this process there are several ways in which it may become infested.

While on an elevator (see fig. 5) the cereal may be infested by eggs,
larvae, or adults of the several insects dropping or crawling into it.
Warehouses are usually more or less infested by insects which crawl
around on the packages. The grocer's storeroom and shelves are also

A SEALED PAPER CARTON TO PROTECT CEREALS. 5

places where infestation takes place. Unless put into insect-
proof carton the cereal, therefore, is subject to infestation from the

Fig. 5.— Cereal elevator which leads from sterilizer to packing room. Infestation may easily take place

here. (Original.)

time it comes from the rolls or the sterilizer until it is sold to the
consumer. Infestation may, of course, take place after the package

BULLETIN 15, U. S. DEPARTMENT OF AGRICULTURE,

is opened by the purchaser, but this does not concern the manufac-
turer.

DRYING THE CEREAL.

After the cereal has been sterilized it may contain too much
moisture to be packed, and a drying process then becomes necessary.
In the case of cereals which are not flaky and to which agitation is
not injurious, a sterile chute with baiSes (fig. 6), through which hot,

N

y\ \

\ y /

•s \

Fig. 6.— Diagram of chute with baffles for cooling cereal. (Original.)

dry air is blown, would be effective. The air is thus placed in contact
with the falling cereal. In the case of flaky cereals a belt elevator is
necessary, but this can be inclosed and the hot air used as in the
former case. Both elevators should be so constructed that they can
be readily sterilized with air at a temperature above 180° F. This
should be occasionally done as precaution against infestation.

THE SEALED CARTON.

The sealed carton may be made of a stiff, though perhaps a cheaper^
grade of cardboard than is used when the cardboard itself is printed.

The printed label
should be made in
three pieces,
namely, two ends,
which lap over the
edges and extend
a short distance
down the side ; and
a side piece, which
securely covers
the edges of the
end pieces. (See
fig. 7.) One sealed carton was observed which had a strip of paper
pasted across the corners before the ends were put on. This further
insures the resistance of the carton to insect attack and is advisable,
provided the cost is not too great.

A sealed package was observed on which the ends of the carton
were not as firmly glued as they would have been had the package

Fig. 7. — Diagram of carton, showing method of applying label to protect
inclosed cereal from insect attack. (Original.)

A SEALED PAPER CARTON TO PROTECT CEREALS. 7

not been labeled. The looseness of this end caused a break in the
label, which, of course, ruined the seal of the package. Care in the
proper sealing of the ends of the carton before applying the label will
remedy this defect.

The extra cost of a sealed package over the ordinary one will vary
with the labor or machinery available and the cost of materials. It
has been estimated at 1 cent for a 2-pound package, but it is best
determined by each miller for his particular locality. With right
management the cost should not prove excessive, while the use of
the well-made sealed package will minimize the chance of infestation.
The improved appearance of such a package, also, renders it more
attractive to the prospective buyer.

PACKAGES OTHER THAN SEALED CARTONS.

Other forms of packages have been suggested, the most promising
one being a sealed paper bag placed inside of an ordinary carton.

Fig. 8. — Carton with paper bag inside. Note larva on cover, and loose cereal which it has webbed together.

(Original.)

Although this forms a barrier to insects which have crawled through
the openings in the corners of the carton, it places them with little
or no food firmh' against a thin wall of paper through which they
would be very likely to force their way.

Furthermore, it was observed that the ends of the paper bags were
not readily sealed; small openings were left in many cases. One
firm using this package reported that about as many of this type
wore returned infested as of the old-st^le packages.

Again, the small amount of cereal spilled between the bag and the
carton is used by a larva, as shown in figure 8, and, in any event,
the presence of insects on the top of the bag would be sufficient cause
for the return of the package.

8 BULLETIN 15, U. S. DEPARTMENT OF AGRICULTURE.

SUMMARY.

The foregoing observations and experiments have brought out
several points:

(1) Cereals may become infested before they are packed, after the
packages are placed in warehouses, and in the grocery stores.

(2) Insects find their way in at the small holes which are usually
present at the corners of unsealed packages or at holes accidentally
punched in the sides.

(3) Thorough sterilization^ at 180° F. kills all insect life; and if
the cereal is run from the sterilizer either through a sterile cooler or
directly into sterile packages and immediately sealed, it will not
become infested unless the package is broken.

(4) Sterilization of the knocked-down cartons before packing and
cleanliness wath regard to the exclusion of insects from the packing
room will greatly facilitate the preparation of sterile packages and
is strongly recommended.

(5) It is absolutely necessary that all. machinery connecting the
sterilizer and the packages be free from insects. If the cereal is
passed through chutes or conveyors which can not be sterilized or
are not kept sterile, it will, through these sources, become infested
even though the cereal was previously sterile and was packed in

sterile packages.

• . . ___

1 The writer has not extensively investigated sterilizers, but the following description, furnished through
the kindness of Mr. Bert D. Ingles, of a sterilizer used by a large flour mill in California may be of interest
here. "In this sterilizer the screw conveyor is 6 inches in diameter and handles approximately 500 pounds
of cereal per hour. The steam is held at 160 pounds pressure, which is equal to 370.5° F. A machine 8 feet
long will heat the cereal under these conditions to 180° F. in two minutes without any difhculty. Such a
sterilization does not injure the cereal."

ADDITIONAL COPIES of this publication
-Li- may be procured from the Superintend-
ent OF Documents, Government Printing
Office, Washington, D. C. , at 5 cents per copy

BULLETIN OF THE

M

No. 19

Contribution from the Bureau of Entomology, L. O. Howard, Chief.
January 24, 1914.

(PROFESSIONAL PAPER.)

THE GRAPE LEAFHOPPER IN THE LAKE ERIE

VALLEY.

By Fred Johnson. Agent and Expert.
INTRODUCTION.

For several years past the grape leafhopper, TypJilocyha comes Say
(fig. 1 ) , has been increasing in destructive numbers throughout the vine-
yards of the Lake Erie Valley, and since 1910 it has been recognized
as a serious menace to the grape-growing interests of that region.
During the years 1910 and 1911 vineyard experiments for the con-
trol of this pest were conducted by the members of
the field laboratory force stationed at North East,
Pa., working under the direction of Mr. A. L. Quaint-
ance, in charge of Deciduous Fruit Insect Investiga-
tions of the Bureau of Entomology. Owing to the
pressure of work involved in the conduct of numer-
ous vineyard experiments against this pest, and also
against the rose-chafer (Macrodactylus suhspinosus
Fab.) and the grape-berry moth (PolycJirosis
viteana Clem.), it was impossible to make a de-
tailed study of the life history of the grape leaf-
hopper during those seasons. As most of these
field experiments had been brought to a success-
ful termination at the close of the season of 1911,
the investigations for the season of 1912 were
devoted largely to life-history studies of tliis pest.
In this work, which was carried on at the field
laboratory at North East, Pa., the writer was
assisted by Mr. E. R. Selkregg in the recording of the data bearing
upon the various stages of the life history of the insect.

The following pages contain a record of these Ufe-history studies,
together with a short historical account of the part this insect has
})layed as an enemy of the graj^evine in other grape-producing sec-
tions of the United States and Canada. A detailed account is given
10037°— Bull. 19—14 1

Fig. 1. — The grape leaf-
hopper ( Typhlocyba
comes): Adult, winter
form. Greatly enlarged.
(Original.)

2 BULLETIN 19, U. S. DEPARTMENT OF AGRICULTURE.

of its habits and destructiveness, the kinds of remedies that have
been devised for its control, and the nature of the spray equi]>nient
and spray material which, in recent experiments, have proved most
effective in holding the pest in check.

HISTORY.'

The first pubHshed record of this insect was made in 1825, when
specimens from Missouri were described under the name Tettigonia
comes by Thomas Say. It was next mentioned by Fessenden in
1828 as being a serious pest in Massachusetts. In 1841 T. M. Harris,
jn his Massachusetts report for that year entitled ''Insects Injurious
to Vegetation," gives a detailed description of the insect and an
account of its habits, life history, and injury to the grapevine. These
observations of Harris coincide quite closely with those recorded by
the more recent workers who have taken up the study of this pest.
Since the date of Harris's report the grape leafhopper has become in-
creasingly prominent as a vineyard pest, and in almost all parts of this
country and Canada it has, at some time or other, appeared in suffi-
cient numbers to prove a real menace to the grape-growing industry.
Although frequent mention of its injurious occurrence in many parts
of the country since 1841 is to be found in entomological literature,
but httle original study, from an economic point of view, seems to
have been bestowed upon this insect, for most of the references have
the appearance of being taken from Harris's account.

During this time, however, a great variety of forms of this species
had been collected, and as a result no less than six different specific
names had been given it. In 1898 the subfamily Tyi)hlocybina3 was
the subject of a special study by Prof. C. P. Gillette, who worked
out the synonymy of the insect as follows :

Typhlocyba comes Say, 1825.
Variety basilaris Say, 1825.
Variety vitis Harris, 1831.
Variety affinis Fitch, 1851.
Variety vitifex Fitch, 1856.
Variety ziczac Walsh, 1864.
Variety octonotata Walsh, 1864.
Variety coloradensis Gillette, 1892.
Variety maculata Gillette, 1898.
Variety scutellaris Gillette, 1898.
Variety rubra Gillette, 1898.
Variety infuscata Gillette, 1898.

By 1897 it had become so seiious a vineyard pest in Cahfornia as
to be placed next in destructive importance to the grape Phylloxera
{PhyUoxera vastatrix Planch.) and was the subject of a detailed

1 The titles of papers and books, and their places of publication, are not given under this and other
headings, but may be found in the Bibliography, pp. 43-17, by looking for the year indicated and,
under that, for the author.

THE GKAPE LEAFHOPPER IN THE LAKE ERIE VALLEY. 3

study by Prof. C. W. Woodworth. In 1901 Slingerland made a very
complete study of the life history of the eastern form, TypJilocyha
comes Say, and of remedial measures for its control, in the vineyards
of Chautauqua County, N. Y., pubUsliing the results in 1904. In
1908 Prof. H. J. Quayle conducted a similarly thorough investiga-
tion of the western form in the vineyards of California. Investiga-
tions of more recent date have been carried on in Chautauqua
County, N. Y., by F. Z. Hartzell, in 1912, and by the Bureau of
Entomology, United States Department of Agriculture, at North
East, Pa. (See Johnson, 1911 and 1912, in Bibliography.)

ORIGIN AND DISTRIBUTION.

Since TypMocyba comes and its several varieties are of common
occurrence on native grapevines in the wild state almost eveiywhere
that the grapevine is found throughout the United States and Canada,
and since this species is not recorded as occurring in Europe, it is
doubtless a native American species.

It was first recorded from Missouri in 1825, and since that date
it has been reported as occurring in destructive numbers in nearly
every State in which cultivated grapevines are grown, either in a
commercial way or for home use. The following statement by
Slingerland in regard to its occurrence is taken from Bulletin 215
of the Cornell Experiment Station, pages 84-85 :

In nearly all discussions of the insect enemies of the gi'ape during the past seventy-
five years, the grape leafhopper has been put in the front rank with the most destruc-
tive ones. The records show that it has deserved a prominent phxce in the rogues'
gallery of grape pests in Massachusetts since 1828, in New York since 1856, in Illinois
since 1871, in Michigan and California since 1875, in Ohio since 1888, and in New
Mexico, Colorado, North Carolina and Minnesota since 1890. Destructive local
outbreaks have also occurred in other States.

POOD PLANTS.

During the growing season of the grapevine the grape leafhopper
apparently confines its attacks entirely to the foliage of this plant.
Early in the spring, however, before the grape leaves commence to
unfold, the adult leafhoppers feed on the new foliage of almost any
and all plants with which they come in contact, whether it be the
foliage of trees and shrubs in woodlands or the weeds and grasses in the
more open sod and pasture lands. The following is a list of trees,
shrubs, and weeds the foliage of which showed evidence of feeding
by the adults in the spring of 1912: Beech, maple, wild cherry, wild
apple, hawthorn, dogwood, wild plum, hornbeam, hackberry, honey-
suckle, wild grape, Virginia creeper, raspberry, thimbleberry, black-
beny, strawberry^, goldenrod, nettles, wild columbine, and a great
variety of weeds and grasses. Along ravines and woodlands border-
ing badly infested vineyards, where large numbers of the adults

4 BULLETIN 19, U. S. DEPARTMENT OF AGRICULTURE.

hibernate, the low-growing foUagc of underbrush and shrubs will
have nearly all of the green coloring matter extracted by this pest
and present a whitened or sometimes brown appearance before the
spring migration of the insect takes place. Those adults which winter
in the vineyards feed upon the green blades and leaves of grasses,
weeds, and the various plants that are grown as cover crops. When
the leaves of the cultivated grapevine commence to unfold there is a
wholesale migration from the foliage of the wild plants, and even
from the foliage of wild grapevines, to that of the cultivated vines,
amounting in the course of a week or so, from about May 1 0 to 25 in the
region of the Lake Erie Valley, to a complete desertion of the foliage
of all plants other than those of the wild varieties of grape and possibly
the Virginia creeper. The percentage of hibernating adults remaining
on the wild grapevines is very small compared with the number found
there before the spring migration to the vineyards has taken place.

It has been observed that in seasons when the infestation through-
out the vineyard area of the Lake Erie Valley has been light, some
of the thinner-leaved varieties, such as Delaware and Brighton, are
apparently more heavily infested and suffer more from the attacks
of this pest than do the thicker-leaved varieties, such as Concord and
Niagara. On the other hand, when these insects are very numerous
throughout a large vineyard area but little if any difference in
respect to the amount of injury to the different varieties can be
observed. Usually vines of weak-growing varieties suffer most from
attack by this pest, yet it has been observed, in run-down Concord
vineyards in which the foliage was sparse, that reproduction of the
leaf hopper during the summer of 1912 was not so great on such
vines, even where the overwintering adults were very numerous in
spring, as in adjacent vineyards where vines of the same variety
were more vigorous and the foliage was more dense.

Although many observations have been made to determine if tliis
insect reproduces on the foliage of plants other than the wild and the
cultivated grape, all the evidence secured has been of a negative
nature . Attemp ts were made to rear nymphs on the foliage of the rasp-
berry, which appears to be a favorite food plant of adults when they
leave hibernating quarters in the spring. A large number of adults
were confined in Riley cages containing raspberry plants. Although
much of the foliage was whitened as a result of their feeding and many
of the adults lived until about the middle of July, there was no
appearance of nymphs at any time during the season upon the foliage
of these plants. All observations during this investigation indicate
that this insect reproduces only on the foliage of the wild and cul-
tivated grapes, and that where vines of cultivated varieties are avail-
able it shows a preference for them and reproduces more freely upon
them than upon the wild species.

THE GRAPE LEAFHOPPER IN THE LAKE ERIE VALLEY.

CHARACTER OF INJURY AND DESTRUCTIVENESS.

The grape leaf hopper injures the grapevine by attacking the foHage.
It is a sucking insect in both the nymphal and adult stages and injures
the plant by inserting its threadlike proboscis (fig. 2) into the under-
side of the leaf and extracting the juices therefrom. The result of
these punctures, and more especially the removal of the juices, is
first evidenced by a yellowing or whitening in patches on the upper
surface of the leaf (fig. 3), which later turns brown, and finally the
leaf falls from the vine prematurely. Where the injury is severe,
the whole leaf dries up and becomes almost functionless long before
the normal ripening period of the fruit arrives. This arrested func-
tioning of the foliage as a result of attack by this pest has a tendency,
when the injury is severe, to
check the development of the en-
tire vine, frequently to such an
extent that the cane growth is
considerably shortened, the size
of the crop of fruit reduced, and
the quality rendered inferior by
a reduction of its sugar content.
During very dry seasons the fruit
on heavily infested vines is badly
spotted by the droppings of the
adult insects.

The overwintering winged
adults commence to attack the
new leaves of the vines when the
shoots are a few inches in length.
Usually the sprouts starting from
the base of the vine and the new
growth along the lower trellis are
the fh'st parts to be attacked.
When large numbers of the adults are present feeding on tliis new
growth, patches of yellow soon appear on the upper surface of the
infested leaves, and in a short time these injured areas dry down and
become brown (fig. 4), and the leaves assume a crumpled appearance,
the result being a stunting of the badly infested shoots. During this
time shoots higher up on the vine, being less heavily infested, have
made a stronger growth which, where the vines are vigorous, soon
overshadows the stunted, badly infested shoots along the lower trellis.
Consequently it frequently happens that this gi'owth on the lower
trelUs develops few or no long, normal, healthy canes.

This condition is of considerable importance, since it is from the
healthy, well-ripened canes springing from the lower trellis that the

Fig. 2. — Head of grape leafhopper, .showing mouth-
parts: (J, Labrum; 6, labium; c, mandibles; r', max-
illte; e, maxillary seta. Greatly enlarged. (Origi-
nal.)

6 BULLETIN 19, U. S. DEPARTMENT 01^ AGRICULTURE.

fruiting canes for bearing the next season's crop are selected. For
the first season or two that a vigorous vineyard is infested, this stnnted
condition of the bearing canes is overlooked by all but the most
observant vineyardists. With each additional season of heavy in-
festation, however, it becomes increasingly difficult to secure well-
placed, robust, bearing canes, and there is a corresponding decline
in the quantity and quality of the crop until in some instances the

Fig. 3.— Grape leaf showing first, evidence of whitened spots resuhing from feeding of adiUt grape leaf-
hoppers in early summer. (Original.)

crop yield is so reduced that it pays little more than the season's
cost of operating the vineyard.

OCCURRENCE AND DESTRUCTIVE OUTBREAKS.

In speaking of the occurrence of this insect Slingerland has said:
"It has its periods of great destructiveness and comparative obscu-
rity, or its 'ups and downs,' like most of our insects." It may exist on
vines in limited numbers in some grape-producing section for several
seasons without attracting much attention either in regard to its

THE GKAPE LEAFHOPPEK IN THE LAKE ERIE VALLEY. 7

presence or its injury to the foliage of the vines. During these
periods serious injury to the vines or to the crop yield is confined to
a few rows of vines adjacent to ravines, woodlots, or rough pasture
lands. This limited amount of injury usually attracts little attention
and no attempt is made by the vineyardist to hold the insect in check.
Then a series of seasons favorable to its development may occur,
and there appears to be a steady yearly increase in numbers and fur-
ther encroachment into the infested vineyards. Finally it becomes
so abundant and thoroughly disseminated throughout the vineyard

Fig. 4.— Grapo loaf in advanced stages of injury. Areas between veins have turned a reddish brown.

(Original.)

area, and its destruction is so obvious, that it attracts general atten-
tion, and the so-called "outbreak" causes considerable alarm among
the vineyardists. Such "outbreaks" have been recorded from many
States, as is indicated in the quotation from Slingerland under the
caption "Origin and distribution." The same author states that
"outbreaks" have occurred at frequent intervals in various parts of
the State of New York as follows :

In Wyoming County in 1860; in the Hudson Valley in 1865, 1867, 1882, 1887, and
1897; on Crooked Lake in 1880; in Jefferson County in 1887 and 1888; in central New-
York in 1895 and 1899; and in Chautauqua County in 1900 to 1904.

8 BULLETIN 19, U. S. DEPARTMENT OF AORICULTUKE.

Durinji: the period from 1S97 to 1904 tlie writer of this paper resided
at Westfiekl, N. Y., during the suininer months and had the opportu-
nity to observe the development of the outbreak of 1900 to 1904.
There was not a sudden appearance of this pest in a single season, but
a steady increase in numbers for several consecutive seasons preced-
ing the so-called outbreak of 1900. On the other hand, during the
summer of 1903 there was an apparent sutlden disappearance of the
insect from many vineyards which during the two previous seasons had
been badly infested and suffered serious injury to the foliage during the
seasons of 1901 and 1902. In fact, after the season of 1904 this pest
disappeared from the vmeyards of this area of serious infestation to
such an extent that treatment was deemed unnecessary. For several
years after this disappearance in destructive numbers of the insect
from the vhiej-ards in the vicmity of Westfiekl, N. Y., its occurrence
in vineyards throughout the Lake Erie Valley was not considered of
sufficient importance to warrant treatment. In 1909, however, during
the conduct of vineyard experiments at North East, Pa., the appear-
ance of this pest in injurious numbers was again observed in portions
of several widely separated vineyards throughout the township. In
the latter part of the season of 1910 the area of serious mjury was
much more widespread and its increase was viewed with alarm by
vineyardists, and in the season of 1911 a number of the more pro-
gressive growers equipped themselves to fight the pest. During 1911
the injury wrought by the pest was greater than in preceding years,,
and the infestation was more widespread. The summer was unusually
hot, and this resulted in the development of an almost full second
brood which worked great injury to the vines late in the season.
Immense numbers of adults went into hibernation, and large numbers
of them emerged and made their appearance in the vineyards in the
spring of 1912. Early in the season of 1912, on account of the pres-
ence of so many overwintering adults, there was every indication that
the injury by this pest would be very great. There was an appar-
ently normal development of the first brood of nymphs, and by the
middle of the summer the injury in many vineyards was quite severe.
Fortunately, however, the months of July and August were unseason-
ably cool. The low temperatures which prevailed during these two
months so greatly retarded the development of the nymphs of the first
brood that only a small percentage of the adults transforming from
them deposited eggs for a second brood of nymphs. Hence there was
not such a great increase in numbers of the insect durmg the latter
end of the season of 1912 as there was at the end of the hot season of
1911. Nevertheless the mjury done by this pest to many vineyards
was very great. The injury to the foliage, coupled with the coolness
of the summer, resulted in badly infested vmeyards, in a retardation
of the cane growth, in a lack of proper development of the size of the

THE GEAPE LEAFHOPPER IN THE LAKE ERIE VALLEY.

9

berries in the cluster, and in a deficiency in the sugar content of the
fruit. For these reasons the aggregate injury by this pest during the
season of 1912 was fully as great as in that of 1911.

Thus far mention of the destructiveness of this pest has been con-
fuied to the vineyard areas of the Eastern States. For more than 25
years this species, Typhlocyha comes, including a western variety,
coloradensis (fig. 5), has caused an enormous amount of injury to the
grapevines in the vineyards of California, where it has been recorded as
an injurious grapevine pest smce 1875. Prof. H. J. Quayle, in Bul-
letin 198 of the California Experiment Station, states in regard to its
destructiveness that "with the exception of the Phylloxera, the vine
hopper is undoubtedly the most destructive insect pest of the vine m
the State. It is more uniformly present than any other insect attacking
the vine, and each year in some parts of the
State it occurs in very great numbers, and
in such sections it levies a heavy tax upon
the vineyard interests."

Thus it is evident that, taken in the aggre-
gate, the injury sustained by the vineyard
industry of the East and the West must
amount to an enormous sum. It should be
remembered, too, that the injury caused b}^
this pest is not confined to the crop of a
single season. It frequently happens that a
heavy infestation of one or two seasons'
duration may so stunt the growth of the vine
that its full fruiting capacity may be re-
duced for several seasons. In fact, if special
efforts for the resuscitation of badly injured
vines are not undertaken they may never re-
gain their former productive value. Hence
the loss to the vineyardist not only consists
in the crop shrinkage, but also in the additional cost of the fertiliza-
tion and care required to get the vine back into full bearmg condition.

ALLIED SPECIES.

In the region known as the Chautauqua and Erie grape belt, which
includes a narrow strip of territory stretching along the southern
shore of Lake Erie from Silver Creek, N. Y., to Harbour Creek, Pa.,
there are approximately 40,000 acres of vineyard, over 90 per cent of
which are of the Concord variety. The species of leafhopper found
in injurious numbers in the vineyards throughout this region is
Typhlocyha comes. Although occasional specimens of other varie-
ties and species may be found, their presence in numbers suflicient to
10037°— Bull. 19—14^—2

Fig. 5. — A western variety of the
grape leafhopper, Typhlocyha
comes var. coloradensis: Adult.
Greatly enlarged. (Author's
illustration.)

10

BULLETIN 19, U. S. DEPARTMENT OF AGKICULTUKE.

work a groat amount of injury has not been observed. The other
species most commonly found associated with T. comes is T. tricincta
Fitch (fig. 6,6), Tliis species, when present, is more hkely to be found
on the foUage of Delaware, Catawba, Brighton, and some of the wild
species of grapevine growing along ravines or in woodlands. It
is readily distinguished from comes by the larger size and by the
fact that it has three broad black bars situated as follows: One
just back of the head, another about midwaj^ across the elytra, and

Fig. 6.— The two species of grape leafhopper most common in vineyards of the Great Lakes Region:
a, Typhloct/ba comes; b, Typhlocyba tricincta. Greatly enlarged. (Original.)

the tliird at the tips of the elytra. Nymphs of tricincta (fig. 7)
have two black spots back of the eyes and two on the thorax.

Wliile making trips through the vineyard areas along the shore of
Lake Erie as far west as Sandusky, Ohio, it was observed that in the
Ohio vineyards east of Cleveland Typlilocyha tricincta was present in
greater numbers than in the vineyards of Chautauqua County, N. Y.,
and of Erie County, Pa., although more than 80 per cent were still
Typhlocyba comes. In the vineyards west of Cleveland T. tricincta

THE GKAPE LEAFHOPPER IN THE LAKE ERIE VALLEY.

11

was present in greater numbers than in the vineyards east of that
city. This condition also existed in the vineyards surrounding San-
dusky, Ohio. In vineyards on Kelleys Island, North Bass, South
Bass, and Middle Bass Islands both T. comes and T. tricincta were
very abundant and there were also a number of other species and
varieties in abundance which were not common in vineyards on the
mainland, the most common being T. vulnerata Fitch. It should be
stated that in the vineyards east of Cleveland, Ohio, the vines are
nearl}^ all of the Concord variety, whereas west of that city there is
a considerable percentage of Catawba and of Early Ohio, while
around Sandusky, Ohio, and upon the islands the percentage of the
Concord variety is small, Catawba benig the variety most commonly

Fig. 7. — Three nymphs of Ti/phlocyba tricincta on underside of grape leaf: a, Cast skin of nymph. Enlarged.

(Original.)

grown, as also Delaware, Ives Seedling, Elvira, and a number of
' other varieties used in wine making. In the vineyards on the main-
land around Sandusky T. tricincta was the species present in destruc-
tive numbers. T. conies was also present, but only in small numbers.

Observations in the vineyards of Michigan during the seasons of 1911
and 1912 showed that T. tricincta is the predominant species in vine-
yards surrounding Lawton and Paw Paw and in the vicinity of Ben-
ton Harbor and St. Joseph. In the vineyards of Michigan T. comes
is present in even smaller numbers than in the vineyards about San-
dusky, Oliio.

Although the development of these two species seems to be almost
identical, adults of T. tricincta brought from the vicinity of Dover,

12 BULLETIN 19, U. S. DEPARTMENT OF AGRICULTURE.

Ohio, in the spring of 1912 produced a brood of nymphs which
matured to adults. These adults, in turn, produced nymphs which
developed to adults of the second summer brood. Observations in
the vineyards of Ohio and Michigan, however, during August of 1911
and of 1912 indicate that this species produced a much smaller
number of second-brood nymphs than did T. comes in the vineyards
surrounding North East, Pa.

It should be added that a very large percentage of the grapevines
grown in the Michigan vineyards are of the Concord variety, and
that on these vines T. tricincta is the predominating species, whereas
in the vineyards of the Chautauqua and Erie grape belt, where the
Concord is the leading variety grown, T. comes is the predominant
and destructive species.

Little, if any, effort has been made thus far by the vineyardists of
Michigan to control T. tricincta, although in the season of 1911 it
was quite destructiA^e in many vineyards. Several vineyardists in
the vicinity of Lawton and Paw Paw were planning to combat it
with a tobacco-extract spray in 1912, but although there was a
heavy infestation of overwintering adults in the spring these failed
to produce a large enough brood of nymphs to injure the vines seri-
ously, thus rendering a spray treatment unnecessary.

DESCRIPTION.

THE ADULT OR WINGED FORM.

The adult grape leaf hopper {TypMocyha comes Say) (see fig. 1,
p. 1) is an insect about one-eighth of an inch long. The original
description of the insect by Say, made in 1825 (see Bibhography),
is as follows:

Pale yellowish with sanguineous spots. Inhabits Missouri.

Body pale yellowish; head, a transverse sanguineous line, profoundly arcuated
in the middle, and a smaller transverse spot before; eyes fuscous; thorax with three
sanguineous spots, the lateral ones smaller and the intermediate one arcuated; scutel,
a sanguineous spot at tip; hemelytra yellowish white spotted with sanguineous; spots
arranged two at base, of which the outer one is small and the inner one elongated
and abruptly dilated on the inner side at tip; two upon the middle, of which the
outer one is elongated in a very oblique line; the two behind the middle, of which
the inner one is obliquely elongated, and the outer one smaller and interrupted; and
a transverse linear one near the tip, ramose upon the nervures; feet whitish.

Length to the tip of the hemelytra one-ninth of an inch.

The line and spot on the head and the spots of the thorax are sometimes obsolete,
but are always visible, and the latter are sometimes connected by curving toward
the anterior edge of the thorax. The spots of the hemelytra are also sometimes
slightly interrupted, or connected into four oblique bands.

In winter the color markings are deep salmon-red. After the
insects have fed upon the foliage of the grapevme for a short time
the color becomes paler and is displaced by a Hght yellow. In the

THE GKAPE LEAFHOPPER IN THE LAKE ERIE VALLEY.

13

newly transformed adult these yellow markings are hardly discerni-
ble (fig-. 8), the whole body being very light straw color. In a short
time, however, they become more pronounced. Along toward the
middle of August the salmon color begins to appear, first as a light
tint on the thorax and at the base of the elytra and in a short time
extending to tlie tips of the wings. As the season advances the
sahnon color deepens until the insect takes on the more pronounced
red markings of the entering adidt.

THE EGG.

Tlie eggs of the grape leafhopper are not more than tliree-fourths
of a millimeter long and are shghtly curved (see fig. 10, d). They
are semitransparent, with a yellowish tinge, and are .very difficult
to locate, since they are deposited beneath the
epidermis of the underside of the grape leaf, which
in most varieties is covered with a heavy pubes-
cence. It is very difficult to detect them witli
the naked eye even after tlie most careful search.
They may be located, however, with the aid of a
hand lens or dissecting microscope by examining
the underside of the leaf in bright sunhght.
Under these conditions the egg's appear as sfight
shiny elevations under the epidermis. By care-
fully scraping away the pubescence covermg this
area the outline of the egg may be more plainly
discerned. Figure 9 is an enlarged photograph
showing the outlines of two eggs beneath the epi-
dermis of a leaf of Concord grape. The eggs are
extremely deficate and are very easily crushed
when an attempt is made to remove the thin,
semitransparent layer of leaf skin or epidermis
underneath which they have been tucked by means of the slender
ovipositor of the female (fig. 11). Figure 12 shows the anal segment
of a male of the same species, with its genital armature.

The eggs are usually deposited singly over the surface of the leaf,
sometimes in or near the ribs and veins, but usually m the spaces
between them. They do not appear to be placed in any regular
order, but occasionally several may be found in close proximity.
In one mstance, in the leaf of a Clinton vine, tlii'ee eggs were found
quite close together with the long axis of all extending in the same
general direction. SHngerland mentions finding the eggs laid from
six to nme in a row in leaves of the Clinton grape. In this variety
the leaf is less fleshy and has less pubescence than have the leaves
of nearly aU of the other varieties of grapes grown in the East.
Examinations of the location and proximity of eggs in tliin-leaved

Fig. 8.— Adult grape leaf-
hopper, summer form,
showing the lighter shade
of color markings of the
elytra. Greatly enlarged.
(Original.)

14

BULLETIN 19, U. S. DEPAETMENT OF AGEICULTURE.

specios of ^vild grapevim^s did not bear out the supposition that
deposition in rows is gcn(^ral in the thin-leaved varieties, for in all
other cases where eggs were found on them they were deposited
with an apparent disregard for regularity of position.

Among A^ineyardists there is commonly a mistaken idea that the
small, transparent globules that are seen on the new growth of the
grapevine, especially in the early summer, are the eggs of the grape
leafhopper. These are not eggs but are small drops of sap which
exude from the rapidly growdng leaves and tendrils.

THE NYMPH.

The young grape leafhopper, or nymph, when it hatches from the
egg, is very minute, white in color, and of the same general form as

Fig. 9.— Outline of eggs, a and 6, of grape leafhopper on underside of grape leaf with pubescence pushed
aside. Greatly enlarged. (Original.)

the adult, but differing from the mature parent in that it does not
possess wings. It attains its growth by casting its skin in a series of
five molts. These five nymphal stages are represented in Plate I.
The time required for the nymph to reach maturity varies greatly
with the different individuals. During the season of 1912 rearings
were made of a large number of nymphs.

First stage. — The newly hatched nymph has a wliite body and red
eyes. It does not run very rapidly at first, but moves over the
underside of the leaf with rather an uncertain, "wobbly" gait. The
number of days required for this stage, from hatching to the first

THE GRAPE LEAFHOPPER IN THE LAKE ERIE VALLEY.

15

Fig 10 —1 he grape Ic ifhoppcr a and 6, Eggs, p ir-
tialK shown iindoi pubos(ou(o c, pgg brought
into view ; d, greatly enlarged egg. All enlarged .
(Original.)

molt, may vary anywhere from 3 to 15. The majority of the nymphs,

however, complete the stage in from 3 to 5 days.

Second stage. — In the second nymphal stage the insect becomes

more active. The eyes lose some of their red color and the body

assumes a yellowish tint, and at the base of the thorax there appear

signs of the wing pads in the form

of lateral buds. The length of

this stage may vary from 1 to 7

days. The majority of nymphs

complete the stage in 3 to 4 days.
Third stage. — The insect in the

third stage moves about very ac-
tively when disturbed, running

with a sidewise motion. Very

rarely can one be made to hop for

even the shortest distance. The

red has disappeared from the eyes,

and the yellow markings on the

thorax have now become quite pronounced. The wing pads extend

to about the caudal margin of the first abdominal segment. Tliis

stage may occupy from 1 to 11 days. In most cases from 4 to 6 days

is required.

Fourth stage. — In the fourth stage the spines on the segments of the

thorax and on the legs
are more pronounced,
and the wing pads now
extend to the caudal
margin of the second ab-
dominal segment. This
stage may occupy from 3
to 13 days, although the
majority of nymphs com-
plete it in 3 to 7 days.

Fifth stage. — In the
fifth stage the wing pads
are considerably length-
ened, extending to about
the middle of the fourth
abdominal segment.
The legs are much longer,

and the insect runs very rapidl}^. This stage may cover from 4 to 20

days. The majority complete it in from 6 to 9 days.

The total length of time required to complete the nymphal stages,

from hatching to the last molt, when the mature insect has fully

developed wings, may vary from 19 to 37 days.

Fig. 11. — Anal segmenis of female grape leafhopper and details:
a, Anal segments; 6, ovipositor in oviposition; c, sheaths of ovi-
positor; d, sting. Greatly enlarged. (Original.)

16

BULLETIN 19, U. S. DEPARTMENT OP AGRICULTURE.

The number of days required to complete the stages of the nymph
were arrived at as a result of rearing 114 nymphs through all of the
five nymphal stages from hatching to adult during the season of 1912,
and the data given above are based on these rearings. It was observed
that variations in temperature greatly influenced the length of the
different stages. It was also noted that although there might be a con-
• siderable variation in the number of days that were required by nymphs
of the same age to complete any one of the stages, the total number of
days covered would vary but sUghtly ; since it frequently happened that
when one stage was protracted beyond the average period, some other
stage would be considerably shortened, and thus the total number of

days for the entire nymphal period would
be about the same for all nymphs of the
same age. (See Table XL)

SEASONAL HISTORY.

ACTIVITIES OF ADULTS IN EARLY SPRING.

The adult grape leafhoppers become
active in their hibernating places beneath
accumulations of leaves, trash, and dried
grass during the warm days of late winter
and early spring. During the warm sunny
hours of such days they rise in swarms
about one's feet when tramping through the
leaves and dried grass of woodlands and
swales which adjoin vineyards which were

clasper; d, inferior clasper. Greatly hcavily iufcstcd duriug the preceding SCa-
enlarged. (Original.) -rw • aU • i f i-' -^ ^1,

son. During these periods ol activity they
feed on the green parts of almost any plant that happens to be growing
near these places of hibernation. At first the green blades of tufts
of grass or the leaves of goldenrod or wild strawberry, and a little
later the unfolding leaves of wild raspberry and blackberry, appear
to form a favorite part of the menu offered by the woodland growth.
As the days become warmer the adults extend their flight and feed
upon the tender unfolding leaves of nearly all kinds of shrubs and
undergrowth. When the new growth of the cultivated grapevine has
attained a length of a few inches there is a general migration of the
insect to the vineyards. Tliis migration occurs about the middle
of May in the vineyards of the Lake Erie Valley, and if the days are
warm and bright the desertion of the woodland food plants for the
foliage of the cultivated grapevine in the course of a few days is quite
complete. In the spring of 1912 this migration from woodlands com-
menced about May 20. On May 24 the leafhoppers were extremely
scarce in woodland places, where until four or five days previous they
had beeii present in swarms since the time of first activity in spring.

Fig. 12. — Anal segments of male grape

loafhopper and details: a, Anal seg-

. ments; 6, genital hooks; c, superior

Bui. 1 9, U. S. Dept. of Agriculture.

Plate I.

The Grape Leafhopper.
greatly enlarged. (Original.)

First stage;
spread. All

THE GRAPE LEAFHOPPER IN THE LAKE ERIE VALLEY. 17

From this date on, the adults confine their feeding and other acti\a-
ties to the foliage of the cultivated grapevine. About this time the
red marking on the elytra disappears and is replaced by a light lemon-
yellow. After the adults once settle down on the foliage of the vines
in the vmeyards there is very little evidence of further migration, and
they seldom leave the shelter of the vmes except when disturbed, in
which case they fly but a short distance and return almost imme-
diately to the underside of the grape foliage. On bright, warm days
they become very active on the slightest disturbance of the vine,
whei'cas on cold wet days it is with the greatest difficulty that they
are dislodged from the underside of the leaves.

For several days after their appearance on the foliage ol the graj^e-
vhies the adults confine their activities to feeding on the underside
of the foliage. This they do by inserting their threadlike mouth
parts or proboscis into the tissue from the underside of the leaf and
suckhig out the juices.

TIME OF MATING.

It is exceedmgly rare to find copulating pairs of adult grape leaf-
hoppers before migration to the vmeyards takes place. After migra-
tion to the vineyards mating is not common until a week or ten days
of feedmg has elapsed.

The first copulating pair seen during the spring of 1912 was on
May 23 upon the foliage of a quince bush in the laboratory garden at
North East, Pa. Occasional copulating pairs were seen in vineyards
as early as May 25, 26, and 27, but mating did not appear to be gen-
eral until about June 1. After June 5 mating of overmntering adults
was rarely seen hi the vineyards, although daily observations were
made.

OVIPOSITION OF OVERWINTERING ADULTS.

No direct observation has been made of females in the act of ovi-
position. A number of experiments were made during the summer
of 1912 to secure records of egg deposition and the number of eggs
deposited by individual females, but without success. This failuie
was due to the fact that the leaves of all of the varieties of grapes
gi'own in the Lake Erie Valley possess a heavy pubescence or hairy
growth on the underside. This makes it extremely difficult to locate
the eggs, since they are inserted witliin the tissue of the lei^i beneath
this hairy growth and can only be found after a thorough search.
Even then many of them are doubtless overlooked, since it often hap-
pens that a large number of nymphs will hatch from grape leaves upon
wliich it has been possible to locate only a small ninnber of eggs after
a prolonged and careful search. On June 10 the first eggs seen in 1912
were located on leaves of a Delaware grapevine.
10037°— Bull. 19—14 3

18

BULLETIN 19, U. S. DEPARTMENT OF AGRICULTURE.

LENGTH OF EGG STAGE.

Since we were unable to secure actual records of egg deposition
from which to make a starting point in order to determine accurately
the length of the egg stage, an approximation of this period was ob-
tained in the following manner:

During the season of oviposition a number of adults were confined
hi an air-tight globe cage (PI. II, fig. 1) upon the uninfested foliage
of a small grapevine possessing not more than three or four healthy
leaves. After 24 hours all the adults were removed. The vine was
protected from further infestation and after seven days had elapsed
was examined daily for the appearance of nymphs. A record was
made of the date of the first nymphs to appear. These were removed
from the cage and all other nymphs to hatch were removed at inter-
vals of 24 hours. In the experiments recorded below the adults were
placed on an inclosed grapevine, July 4, at 1 p. m. These adults were
removed July 5, at 1 p. m. The newly hatched nymphs were removed
on the dates recorded hi Table I.

Table I. — Length of incubation period of eggs of the grape leaf hopper.

so adults placed on vine July 4, 1p.m.; adults removed
from vine Jiily 5, 1 p. m.

Date and hour of removal of newly
hatched nymphs.

Number
of nymphs
removed.

Incuba-
tion,
period.

1912.

Julv 17, 1 p. m

.hUy 18, Ip.m

JulV 19, 1 p. m

Julv 20, 1 p. m

July 21, Ip. m

6

46

58

7

5

Days.

11 to 13

12 to 14

13 to 15

14 to 16

15 to 17

50 adults placed on vine June 25, 2 p. m.; adults removed
from vine June 26, 2 p. m.

1912.
July 9, 2.30 p. m

15

45

13

0

1

Days.

11 to 13

12 to 14

13 to 15

Julv 10, 2.30 p. m

JulV 11, 2.30 p. m

Julv 12, 2.30 p. m ....

July 13, 2.30 p. m

15 to 17

100 adults placed on vine June 27, 2 p. m.; adults removed
from vine June 28, 2 p. m.

1912.
July 12, 2 p. m

14
44
19

8

1

Days.

13 to 15

14 to 16

15 to 17

16 to 18

17 to 19

July 13, 2p. m

July 14, 2 p. m

Julv 15, 2 p. m

July 16, 2 p. m

50 adults placed on vine July 27, 2 p. m.; adults removed
from vine Jiily 28. 2 p. m.

1912.
-Vug. 20, 2 p. m

15
4
11

Days.

22 to 24

23 to 25

24 to 26

Aug. 21, 2p. m

Aug. 22, 2 p. m

50 adults placed on vine August 10, 2 p. m.; adults removed
from vine August 11, 2 p.m.

1912.
Aug. 24, 2 p. m

2
1
3
0

i

Days.

12 to 14

13 to 15

14 to 16

Aug. 25, 2 p. m

Aug. 26, 2 p. m

Aug. 27, 2 p. m

Aug. 28, 2 p. m

Aug. 29, 2 p. m

Sept. 1, 2 p. m

17 to 19
20 to 22

THE GEAPE LEAPHOPPER IN THE LAKE ERIE VALLEY. 19

NUMBER OF EGGS DEPOSITED BY AN OVERWINTERING FEMALE GRAPE

LEAFHOPPER.

On account of the great difficulty encountered in locating the eggs
of the grape leafhopper, a record of the reproductive capacity of the
females was secured by confining pairs of overwintering adults upon
small grapevines in an arc-light globe cage similar to that shown in
Plate II, figure 1 , which had been protected from previous infestation,
the ol)ject being to determine the number of nymphs that appeared
on the vines. The pairs used for this purpose were among the first
to be found copulating and at a perio.d before any ovi^^osition had
taken place. Each pair of adults was allowed to remain on the
vine until they died. To avoid the probabiUty of the escape of the
adults, ordy a few examinations were made until the nymphs were
nearing the last molt. The parent adults were then removed and a
careful count was made of the nymphs found upon the fofiage; then
the parent adults were returned to the cage until later examinations
were made, and this process was continued until the death of the par-
ent adults occurred. After the death of the adults a period equal to
the length of incubation of the eggs was allowed to elapse before the
final count for the last nymphs to appear was made. Four separate
experiments were started May 27 with copulating pairs of adults.
Removal of nymphs took place as shown in Table 11.

Table II. — Number of nymphs produced by a female grape leafhopper in confinement.

Nymphs
1912. CAGE NO. I. removed.

July 1 1 34

July 17 ;13

July 25 36

Total 103

CAGE NO. II.

July 11 49

July 17 49

July 25 33

Aug. 1 8

Total 139

CAGE NO. III.

July 10 M

July 11 56

July 17 34

July 25 18

Aug. 1 1

Total 113

CAGE NO. IV.

July 11 34

July 17 33

July 25 36

Aug. ] 9

Aug. 2 2

Total 114

1 Four newly molted adults.

20 BULLETIN 19, U. S. DEPARTMENT OF AGRICULTURE.

Several additional experiments were conducted in the same manner
to determine the number of eggs per female. In each case several
copulating pairs of leafhoppers were placed in each cage.

Table III. — Experiment to determine extent of reproduction from four pairs of copu-
lating grape leafhoppers placed in a cage with a small grapevine June 19. 1912.

Nymphs
1912. removed.

July 27 154

July 30 159

Aug. 22 8

Aug. 27 30

Aug. 29 , 159

Total 510

Average 127. 5

Table IV. — Experiment to determine extent of reproduction from nine pairs of copu-
lating grape leafhoppers placed in a cage with a small grapevine June IS, 1912.

Nymphs
1912. removed.

July 24: 230

July 31 423

Aug. 12 172

Aug. 22 131

Aug. 29 65

Sept. 4 14

Total 1. 035

Average 115

Table V. — Experiment to determine extent of reproduction from four pairs of copulating
grape leafhoppers placed in a cage with a small grapevine June 19. 1912.

Nymphs
1912. ■ removed.

July 24 185

Aug. 9...: 153

Aug. 23 58

Sept. 6 52

Total 448

Average 112

These experiments show that for 20 females the number of nymphs
found ranged from 112 to 139 per female. This method of deter-
mining the egg-laying capacity of the females did not, of course,
take into consideration the number of eggs that failed to hatch, or
the number of fatahties which may have occurred among the nymphs
after the hatching period, but the fact that the average number of
nymphs reared from each of 15 females varied only from 112 to 115
would indicate that under favorable conditions a female may deposit
over a hunch-ed eggs, while the 139 nymphs o})tained in cage 2 would
indicate that under the most favorable conditions some females may
deposit about 140 eggs.

Bui. 19, U. S. Dept, of Asrnciiiture.

Plate II.

Fig. 1.— Cages Used for Rearing the Grape Leafhopper, at Laboratory, North
East, Pa., 1912. (Original.)

Fig. 2.— Steam-Enqine Power Sprayer Used in Spraying Against the Grape
Leafhopper, North East, Pa., 1912. (Original.)

THE GRAPE LEAFHOPPER.

THE GKAPE LEAFHOPPER IN THE LAKE ERIE VALLEY. 21

HATCHING OF FIRST-BROOD NYMPHS.

After the finding of eggs in the tissue of the leaves on June 10, daily
examinations of infested grape foliage were made both in badly
infested vineyards and on vines at the laboratory. On June 18 three
nymphs were found on the badly infested foliage of a Delaware grape-
vine. These nymphs were probably about a day or two old, since
they were slightly larger than newly hatched nymphs. They had
taken on a yellowish color, which indicated that some time had been
spent in feeding, for the newly hatched nymphs before having taken
any food are white.

On June 20 a number of newly hatched nymphs were found on
Concord vines. After June 20 the hatching of the nymphs became
general. By June 26 large numbers of them could be found in all
badly infested vineyards in the vicinity of North East, Pa.

The process of hatching was observed in several instances and
occupies a period varying from 10 to 25 minutes.

The hatching nymph appears as a small wliite object projecting
through the pubescence on the underside of the leaf. At first its
movement is almost imperceptible. Then, after three or four min-
utes, there is a swaying circular movement of the free end of this white
object, each succeeding movement becoming more vigorous. After
four or five minutes of this rapid motion the object commences to
assume a definite form. The ends of the antennae are freed, the eyes
become prominent, and the stricture dividing the thorax from the
abdomen may be distinguished. In a few minutes more the proboscis
and the legs may be seen moving, then the circulation of the body
fluids becomes visible through the transparent skin, and finally the
feet clutch the hairy pubescence of the leaf and the tiny insect draws
its abdomen free of the eggshell. By this time the body has dried,
and the nymph runs with a rather unsteady gait over the underside
of the leaf. Usually, however, its first excursion is a veiy short one,
for it soon settles down, inserts its minute proboscis into the leaf
tissue, and makes its first meal on the juices of its host plant.

APPEARANCE OF FIRST-BROOD ADULTS.

During the season of 1912 the first evidence of the appearance of a
new brood of adults occurred on July 12, when examinations of
nymphs in vineyards about North East, Pa., showed that at this date
an occasional nymph was making the last nymphal molt and devel-
oping wings. However, winged adults of this new brood were not
common in vineyards until from July 16 to 20, and even at the latter
date they did not represent more than 25 per cent of the total num-
ber of the new brood upon the foliage. In order to secure some of
these earUest transforming adults for the purpose of rearing a second
summer brood, about 150 of the oldest nymphs that could be found

22 BULLETIN 19, U. S. DEPARTMENT OP AORICULTURG.

were placed on tho foliage of a young (^oncord grape\ane on July iL'.
On July 13 several of these nymphs had transformed to adults. On
July 16 about 75 per cent of them had developed wings.

MATING OF FIRST-BROOD ADULTS.

On July 22 numerous pairs of adults of the new brood were found
copulating on the underside of grape leaves in the vineyards sur-
rounding North East, Pa. From July 23 to 27 copulating pairs of
new-brood adults were common, both in the vineyards and in cages
at the laboratory. After the latter date only occasional mating
pairs of adults were observed, either in the rearing cages at the
laboratory or in the open \dneyards, although observations along
this line were continued during the remainder of the active season,

NUMBER OF EGGS DEPOSITED BY A FEMALE OF THE FIRST BROOD.

On July 26 three copulating pairs of the new-l)rood adidts were
placed in separate cages on a Concord grapevine inclosed in an arc-light
globe cage similar to those in wliich pairs of overwintering adults had
been confined, the object being to ascertain the number of nymj^hs
that could be reared from them in order to see how it compared with
the number produced by overwintering females. The number of
nymphs reared from these first-])rood females is shown in Table VI.

Table VI. — Number of nymphs producrd by a fcmtile leaf hopper of fhe firxt brood.

CACE NO. I.

Nymphs
Date examined (1912). removed.

Sept. 4 12

Sept. 7 5

Sept. 11 7

Sept. 1-1 9

Total 33

CAGE NO. II.

Sept. 3 24

Sept. 5 16

Sept. 9 - ] 7

Sept. ] 1 9

Sept. 15 13

Total 79

CATJE NO. ni.

Sept. 4 37

Sept. 7 : 35

Sept. n 9

Total 81

In the case of these three females of the first brood, the average
number of nymphs produced by a single female was only a httle more
than half the number produced by the overwintering females under
similar conditions.

THE GRAPE LEAFHOPPER IN THE LAKE ERIE VALLEY.

23

TERMINATION OF OVIPOSITION OF ADULTS OF THE FIRST BROOD.

First -brood adults placed in cages with grapevines after August 10
gave no evidence of further reproduction, for nymphs failed to appear
on the foliage. About 50 adults were placed in each of five separate
cages on August 12, 15, 20, and 27, and September 9. No nymphs
appeared in any of these cages, indicating that the season of egg
deposition for them, at least, had closed.

Since there is a long period over which the nymphs of this first
brood transform to adults, an endeavor was made to determine the
date at which these later transforming adults would fail to reproduce
during the same season. With this end in view, on July 24, 1912,
100 nymphs of each of the five nymphal stages were placed in five
separate cages on the fohage of a small Concord grapevine in order
to ascertain if the adults transforming from any or from all of the
nymphs in these five cages would copulate and produce another
brood of nymphs. Frequent examinations were made of all of these
cages during the remainder of the season. All of the nyiuphs in the
five cages transformed to adults, but no mating of the adults was
observed nor did any nymphs of a new brood appear upon the foliage
of the vines in the cages.

On the other hand, in another cage in which 50 adults were placed
on July 22, to determine to what extent and how late in the season
they continued to reproduce, nymphs continued to hatch as late as
September 15. Below is given the daily hatching record of nymphs
from these 50 adults:

Table VII. — Flatching record of nymphs from 50 adult gra-pe leafho'p'pers placed in

confinement July 22, 1912.

Number

Number

Number

Number

Date.

of
nymphs

Date.

of
nymphs

Date.

of
nymphs

Date.

of
nymphs

removed.

removed.

removed.

removed.

1912.

1912.

1912.

1912.

Aug. 12

38

Aug. 22

143

Aug. 31

52

Sept. 9

25

Aug. 13

132

Aug. 23

76

Sept. 1

96

Sept. 10

13

Aug. 14

172

Aug. 24

83

Sept. 2

108

Sept. 11

8

Aug. 1.5

245

Aug. 25

50

Sept. 3

115

Sept. 12

6

Aug. 16

173

Aug. 26

137

Sept. 4

95

Sept. 13

4

Aug. 17

139

Aug 27

108

Sept. 5

89

Sept. 14

2

Aug. 19

272

Aug. 28

5

Sept. 6

48

Sept. 15

6

Aug. 20

250

Aug. 29

73

Sept. 7

49

Aug. 21

131

Aug. 30

47

Sept. 8

24

LONGEVITY OF OVERWINTERING ADULTS.

An effort was made to determine the length of life of overwintering
adults. Owing to the great activity of the adult leaf hoppers it was
found to be exceedingly difficult to keep a record of each individual-
In order to secure some data on this point 100 overwintering adults
were placed on a small Concord vine inclosed in an arc-fight globe
cage on May 31. A black cloth was stretched over the surface of

24

BULLETIN 19, U. S. DEPARTMENT OF AGRICULTURE.

the ground so that the dead adults falling from the fohage of the
vine might be more easily seen. An exananation for dead adults
was made every few days by looking for them upon the black cloth.
No dead adults were observed to July 12. On July 12 the adults
were transferred to a new cage to avoid confusing them with newly
transforming adults. During this operation IS adults either escaped
or were killed. In this new cage 82 adults were placed. Dead adults
were found in the cage on the dates shown in Table VIII.

Table VIII. — Longevity of overwintering adults of the grape leaf hopper.

I

Date of

Num-

Date of

Num-

examina-

ber

e.xamma-

ber •

tion.

dead.

tion.

dead.

1912.

1912.

July 17
July 2X
Aug. 2
Aug. 3
Aug. .5
Aug. 7

1

3
2

1 5

2 2

»3

Aug. 12
Aug. 17
Aug. 23
Aug. 27
Aug. 30

3
2
4
3
5

1 Escaped.

2 Killed.

3 Killed by spider.

On August 30 these adults were again transferred to a new cage to
avoid their being confused with newly transforming adults. During
this transfer 10 adults were either killed or escaped. In the new
cage there were 39 adults. The number of dead adults found in this
cage is given in Table IX.

Table IX. ^ — Longevity of overwintering adults of the grape leaf hopper.

Date of
examina-
tion.

Num-
ber
dead.

Date of
examina-
tion.

Num-
ber
dead.

1912.
Sept. 4
Sept. 7
Sept. 12
Sept. 14

4
3
1

6

1912.
Sept. 20
Sept. 26
Oct. 2

3

7
6

The last examination was made on October 2, when there were
four adults still living. Hence it is evident that some of the over-
wintering adults may remain on the vines during the entire growing
season. Yet in vineyards that were the object of frequent visits
during the seasons of 1911 and 1912 it was observed that there was
a period, about the middle of the summer each season, when a de-
crease in the number of hibernating adults was quite noticeable.
During the season of 1911 this period of apparent decrease of over-
wintering adults was about June 25. In 1912 it was about July 15.
In both instances this decrease in number of adults occurred about
two weeks before the transformation of the new brood in large
numbers to adults.

THE GRAPE LEAFHOPPER IN THE LAKE ERIE VALLEY. 25

EXPERIMENTS TO REAR A THIRD BROOD OF NYMPHS.

Rearing exporimonts were also conducted to determine if the adults
which transformed from the earliest hatching nymphs of the season
would produce a second summer brood of nymphs and also if the
ackilts transforming from these second-brood nymphs would mate
and produce a third brood of nymphs.

On July 2, 100 newly hatched nymphs, the product of overwinter-
ing adults, were placed on the fohage of a Delaware grapevine in-
closed in an arc-light globe cage. By July 28 a few of these nymphs
had transformed to adults. By August 14 all of these first-brood
nymphs had transformed to adults. On August 26 several nymphs
of the second summer brood in the first two nymphal stages were found
upon the foliage of the vine. On August 29 all of the adults of the
first brood were removed from this cage in order that there might
be no confusion with adults transforming from the second-brood
nymphs. On September 12 newly transformed adults of the second
l)rood were found in this cage. On September 27 nearly all the
nymphs had transformed to adults. The few remaining nymphs were
in the last nymphal stage. By October 7 all nymphs had trans-
formed to adults. Frequent observations were made after the ap-
pearance of the second brood of adults in this cage, but no mating
was observed nor did any new nymphs appear on the foliage of the
vine. Hence it would appear that reproduction did not occur among
the adults of the second brood during the season of 1912. A similar
rearing experiment was made on July 3 by taking 75 of the earliest
nymphs to hatch and placing them on a grapevine inclosed in an
arc-hght globe cage. By July 16 nearly all of the nymphs had trans-
formed to first-brood adults. On August 15 new nymphs of the
second brood were present. On August 28 all hrst-brood adults
were removed from the cage. All of the nymphs transformed to
second-brood adults. Although frequent examinations were made
of this cage for the remainder of the season, there was no evidence
of reproduction by these adults of the second brood.

In another rearing experiment the date of transformation of adults
of the second })rood was secured. The rearings were made by taking
nymphs of the first brood that were among the earUest of the season
to hatch. They were nearing the last molt when they were placed
on a Concord vine in a Riley cage on July 1 3 . By July 1 6 nearly all
of tlit^se nymphs had transformed to adults. On July 26 several
pairs were observed mating. On August 17 a few nymphs of the
second brood in the first and second stages were observed on the
grape foliage. On August 28 all adults of the first brood were re-
moved from this cage to avoid confusion with newly transforming
adults of the second brood. A record of the dates of transformation
of adults of the second brood is given in Table X.

26

BULLETIN 19, U. S. DEPARTMENT OP AGRICULTURE.
Tablk X. — Transformation to adults of second-brood grape leafhoppci

Date of
examina-
tion.

Number
of adults
trans-
formed.

Date of

e.xamina-

tion.

y umber
of adults
trans-
formed.

1912.
Sept. 7
Sept. 8
Sept. 9
Sept. 10
Sept. 11
Sept. 12
Sept. 13

1
4
0
37
76
51
51

1912.
Sept. 14
Sept. 15
Sept. 17
Sept. 19
Sept. 20
Sept. 21
Sept. 24

85
63
16
26

5
11

3

The last of the nymphs transformed to adults on wSeptemher 24.
This rearing experiment indicates that the transformation of the
second-brood adults which were the progeny of the earliest nymphs
of the season to appear upon the yines was much too late in the season
for the production of a third brood of nymphs.

REARING EXPERIMENTS TO DETERMINE LENGTH OF NYMPHAL STAGES.

A series of rearing experiments was made to determine the length
of the nymphal stages. The newly hatched nymph was placed in a
cage made as follows: A hole about an inch in diameter was punched
out of the center of a piece of yelyet about 2 inches sc{uare. The
velyet was then placed, nap side against the leaf, on tlie underside
of an uninfested leaf. A square of heayy manila paper of the same
size was placed on the upper side of the leaf directly aboye the square
of yelyet, to hold the leaf rigid. The newly hatched nymph was
then placed on the underside of the leaf in the circular space cut out
of the square of yelyet. A small watch glass, conyex side up, was
placed oyer the circular hole in the yelyet so as to oyerlap about
one-fourth of an inch onto the yelyet. Then the watch glass, the
yelyet, the portion of grape leaf, and the square paper were all held
tightly together by means of four paper clips, by slipping on one of
the clips from each side of the square, making them clasp the paper
and the yelyet and oyerlap on to the watch glass and hold the latter
firmly in place so that the nymph could not escape. In some instances
squares of thin sheets of celluloid were used in place of the watch
glasses, but it was found that the small nymphs would sometimes
drown in the moisture collecting on the inside of the celluloid. Then,
too, the concaye of the watch glass made the space larger. Eyen
with the watch glasses, drowning of the nymphs was likely to occur.
In order to preyent this, two squares of yelyet were glued together
with the nap side out. This raised the watch glass a greater distance
from the leaf, giying more space between the back of the nymph
and the glass, and less drowning of nymphs resulted. Each cage was
examined daily; thus the condition of the nymph was obseryed and

THE GEAPE LEAFHOPPER IN THE LAKE ERIE VALLEY.

27

record made ol" the date of each molt. During this ojjeratioii the
moisture was wiped from the inside of the watch ghiss.

The period covered by these rearing experiments was from June
22 to October 13. During this time 348 newly hatched nymphs were
placed on grape leaves confined in cages similar to those just described.
Many of the nymphs either died or escaped before they completed
all of the nymphal stages. Nevertheless, complete records of the
length of the five stages were secured for 114 nymphs. The greater
number of fatalities occurred among the young nymphs during the
early part of the rearing season before the leaf cage most suitable for
the purpose was secured. After the double thickness of velvet was
adopted fewer fatalities occurred.

The lengths of the several stages for the different individuals
show a great variation, but it will be noted by an examination of
Table XI that the variation of the total length of the five stages for
a number of nymphs hatching on the same date is not very great.
Changes in temperature appear to be the important factor in deter-
mining the length of time required to complete the entire nymphal
period.

In the last column of Table XI the average daily temperature
for the entire nymphal period of each of the 114 nymphs is given.
These average temperatures are computed from the average daily
temperatures given in Table XII. The average daily temperatures
given in Table XII are derived from daily readings of a maximum
and minimum thermometer, located in the garden of the laboratory
at North East, Pa., only a few yards distant from the grapevines
bearing the individual cages in which the nymphs were reared.

Table XI. — Length of each of the five nymphal stages of the grape leafhopper for II4
nymphs recorded from June 22 to October IS, 1912.

si

.g

B

03
A

0
03

■3

a

S3
.1

a

a
0

6

B

M

•73

!

03

i

0

a
0

03
0

1

6

1

03

k

C.2

c3 a
0

y e r a g e daily
temperature for
entire nymphal
period.

0

fe

t!^

CO

W

ir^

e

pR

(=^

s

Ph

^

<

1912.

1912.

Dys.

1912.

Dys.

1912.

Dys.

1912.

Dys.

1912.

Dys.

Dys.

T.

June 22

June 2,S

6

June 30

2

July 4

4

July 7

3

July 11

4

19

74.90

July 5

July 9

4

July 10

1

July 13

3

July 16

3

July 25

9

20

76.60

July 9

July 12

3

July 15

3

July 20

5

July 25

5

Aug. 8

14

30

69.97

Do...

July 15

6

July 18

3

...do

2

...do •

5

Aug. 7

13

29

70.10

Do...

...do

6

July 17

2

July 21

4

July 28

"

Aug. 8

11

30

69.97

Do...

July 12

3

July 15

3

July 20

5

Aug. 2

13

Aug. 12

10

34

70.04

Do...

July 13

4

July 16

3

July 21

5

July 27

6

Aug. 9

13

31

70.03

Do...

...do

4

July 17

4

July 19

2

July 25

6

Aug. 7

13

29

70.01

Do...

...do

4

...do

4

July 21

4

July 28

7

Aug. 10

13

32

70.11

Do...

...do

4

...do

4

July .19

2

...do

9

Aug. 9

12

31

70. 03

Do...

...do

4

...do

4

...do

2

...do

9

...do....

12

31

70.03

Do...

July 12

3

July 15

3

...do

4

July 25

6

Aug. 8

14

30

69.97

Do...

July 13

4

July 17

4

July 21

4

July 27

6

...do

12

30

69.97

Do...

July 14

5

July 18

4

July 23

5

July 29

6

Aug. 10

12

32

70.12

Do...

July 13

4

July 16

3

July 21

5

July 28

7

Aug. 9

12

31

70.03

28

BULLETIN 19, U. S. DEPARTMENT OF AGRICULTURE.

T.\BLK XL- Length of each of the Jive nymphal stages of the grape leafhopper for II4
nymphs recorded from June 22 to October 13, 1912 — ^Oontinued.

si

.a

0

1

s

0

a

*i

•0

0

w

to

p

C3

a

.in

^

0

fc

P^

m

1912.

1912.

Dys.

1912.

July 10

July 14

4

July 18

Do...

...do

4

July 17

July 11

July 15

4

July 19

Do...

...do

4

...do

Do...

July 16

5

...do

Do...

July 15

4

...do

Do...

...do

4

...do

Do...

July 14

3

July 18

July 12

July 17

5

July 20

Do...

July 16

4

July 21

Do...

July 17

5

...do

July 13

July 19

6

July 23

Do...

July 17

4

July 21

Do...

July 19

6

July 23

July 14

...do

5

July 25

Do...

July 21

7

July 27

Do...

July 19

5

July 25

July 15

July 22

7

...do....

Do...

July 21

6

...do....

Do...

July 20

5

July 26

July 18

July 25

7

Aug. 2

Do...

...do...

7

July 29

Do...

Aug. 2

15

Aug. 7

Do...

July 25

7

July 30

July 19

July 29

10

Aug. 6

Do...

July 24

5

July 27

Do...

July 27

8

Aug. 3

Do...

July 26

7

...do....

Do...

July 25

6

...do....

Do...

July 28

9

Aug. 6

July 20

July 27

7

July 29

Do...

July 26

6

Aug. 3

July 29

Aug. 8

10

Aug. 11

Do...

Aug. 7

9

...do....

Do...

Aug. 5

7

Aug. 10

Do...

Aug. 7

9

Aug. 11

Do...

Aug. 8

10

Aug. 12

Do...

Aug. 6

8

Aug. 11

July 30

Aug. 11

12

Aug. 14

Do...

Aug. 7

8

Aug. 11

Do...

Aug. 9

10

Aug. 14

Do...

...do....

10

Aug. 12

Aug. 5

Aug. 11

6

Aug. 15

Do...

...do....

6

...do....

Aug. 13

Aug. 19

6

Aug. 23

Do...

Aug. 18

5

...do....

Do...

Aug. 21

8

...do....

Do...

Aug. 18

5

Aug. 22

Aug. 14

Aug. 20

6

Aug. 25

Do...

Aug. 19

5

Aug. 24

Do...

Aug. 20

6

...do....

Do...

...do....

6

...do....

Do...

.do

6
5

...do....
Aug. 23

Do...

Aug. 19

Do...

Aug. 20

6

Aug. 24

Do...

Aug. 19

5

Aug. 23

Do...

Aug. 20

t)

Aug. 25

Do...

...do....

6

Aug. 26

Do...

Aug. 19

5

Aug. 23

Do...

Aug. 24

10

Aug. 29

Dys.
4
3
4

4
3

4
4
4
3

1912.
July 23
July 19
July 24

..do

July 25

..do

..do

July 23
July 26
..do

July 30

July 29

July 26

July 29

July 30

Aug. 4
Aug. 1
Aug. 5
Aug. 2
..do...

Aug. 8
Aug. 6
Aug. 9
Aug. 8
Aug. U

Aug. 3
Aug. 9
..do...
...do....
Aug. 12

Aug. 3

Aug. 9

Aug. 15

Aug. 17

Aug. 14

Aug. 15
Aug. 16
...do....
Aug. 20
Aug. 15

Aug. 19
Aug. 17
Aug. 20
...do....
Aug. 27

...do....
Aug. 29
Aug. 26
Aug. 31
Aug. 28

Aug. 29
Aug. 28
...do....
Aug. 27
Aug. 29

Aug. 27
Aug. 29
Sept. 2
Aug. 27
Sept. 2

Dys.
5
2
5
5
6

1912.
July 30
July 25
July 30

...do

Aug. 2

Aug. 1
Aug. 3
July 30
Aug. 4
July 30

Aug. 7
...do....
Aug. 2
Aug. 7
Aug. 9

Aug. 10
...do....
Aug. 11
Aug. 10
..do....

Aug. 14
Aug. 11
Aug. 15
Aug. 13
Aug. 15

Aug. 9
Aug. 15
...do....
Aug. 14
Aug. 15

Aug. 9
Aug. 14
Aug. 21
Aug. 22
Aug. 21

...do....
Aug. 22
...do....
Aug. 25
Aug. 21

Aug. 25
Aug. 22
Aug. 25
...do....
Sept. 2

Aug. 29
Sept. 3
Sept. 2
Sept. 4
Sept. 3

Sept. 5

Sept. 4

Sept. 3

Sept. 2

Sept. 3

Sept. 2
Sept. 3
Sept. 6
Sept. 3
...do....

Dys.

1912.
Aug. 11
Aug. 14
Aug. 12

...do

Aug. 13

Aug. 12

Aug. 13

Aug. 10

Aug. 13

Aug. 15

Aug. 14

Aug. 15

Aug. 12

Aug. 15

Aug. 17

Aug. 19
...do....
Aug. 21
Aug. 19
...do....

Aug. 22
Aug. 20
Aug. 24
Aug. 22
Aug. 25

Aug. 15
Aug. 23
Aug. 24
Aug. 23
Aug. 25

Aug. 23
Aug. 24
Aug. 31
Sept. 1
Aug. 29

Aug. 30
Sept. 1
...do....
Sept. 3
Aug. 30

Sept. 2

Sept. 1

Sept. 5

Sept. 3

Sept. 8

Sept. 9
Sept. 10
Sept. 8
Sept. 11
Sept. 9

Sept. 10
Sept. 11
Sept. 9
Sept. 8
Sept. 9

...do....

...do....
Sept. 14
Sept. 9
Sept. 10

1

S

C3

h

a. 2

C3 P,

Average daily
temperature for
entire nymphal
period.

Dys.
12

Dys.
32

"F.
69.81

20

35

69.86

13

32

69. 58

13

32

69.58

11

33

69.69

11

32

69.58

10

33

69.69

11

31)

69. 62

9

32

69.75

16

34

69.32

-

33

69.42

S

33

67.14

10

30

69.08

8

33

69.10

8

34

68.75

9

36

68.63

10

37

66.77

10

37

68.36

9

35

68.34

9

35

68.34

8

35

67.67

9

33

67.79

9

37

67.71

9

35

67.84

10

37

67.92

6

27

68.77

8

35

67.84

9

36

67.71

9

35

67.84

10

36

69.81

14

34

67.79

10

35

67.66

10

33

67.53

10

34

67.73

8

31

69.03

9

32

67.84

10

34

67.73

10

34

67.73

9

35

68.16

9

31

67.68

8

34

67.95

10

33

67.68

11

31

69.95

9

29

68.55

6

26

71.52

11

27

71.41

7

28

71.55

6

26

71.52

7

28

71.75

6

26

71.33

6

27

71.48

7

28

71.75

5

26

71.33

6

25

71.44

6

26

71.33

7

26

71.33

6

26

71.33

S

31

71.24

6

26

71.33

7

27

71.48

THE GRAPE LEAFHOPPER IN THE LAKE ERIE VALLEY.

29

Table XI. — Length of each of the five nymphal stages of the grape leaf hopper for II4
nymphs recorded from June 22 to October l.i, 1912 — Continued.

1912.
Do...
Do..
Do...
Do..
Aug. lo

Do...
Do...
Do...
Do...
Do...

Aim'. 10
Do...

Aug. 17
Do...
Do...

Do...

Aug. 20
Do...

Aug. 21
Do...

Do...
Do...
Do...
Do...
Do...

Aug. 22
Do...
Do...
Do...

Aug. 30

Sept. 4
Do...
Do...

Sept. 6
Do...

Do.
Do.
Do.
Do.

1912.
Aug. 20
..do....
..do....
..do....
.Vug. 23

-Vug. 21
..do....
..do....
..do....
..do....

..do....
..do....
..do....
Aug. 22
..do....

..do....

Aug. 2.=1
Aug. 24
Aug. 25
..do....

Aug. 26

Aug. 25

-Vug. 26

Aug. 25

Aug. 26

Aug. 27
Aug. 26
..do....
..do....
Sept. 3

Sept. 7
..do....
.-do....
Sept. 10
..do....

.do...
-do....
.do....
.do....

Dys
6
6

6
6

1912.
Aug. 25
Aug. 24
Aug. 25
Aug. 24
Aug. 26

...do...
...do...
...do.
Aug. 25
...do ...

...do...
...do...
Aug. 26
...do...
...do...

Aug. 27
Aug. 30
Aug. 27
Aug. 30
Aug. 29

Sept. 1
Aug. 29
Sept. 1
Aug. 31
...do....

Sept. 2
Aug. 31
Sept. 1
...do....
Sept. 7

Sept. 14
Sept. 12
Sept. 11
Sept. 14
...do....

-do....
...do....

Sept. 13
Sept. 14

Dys

5
4

5
4
3

1912.
Sept. 1
Aug. 29
Sept. 1
Aug. 27
Aug. 31

...do....
Aug. 30
Aug. 31
.'Vug. 30

...do....

...do....
Aug. 31
Sept. 1
Sept. 2
Sept. 1

...do....
Sept. 3
Sept. 2
Sept. 3
Sept. 2

Sept. 4
Sept. 2
Sept. 4
Sept. 3
...do....

Sept. 5
Sept. 3
Sept. 4
..do....
Sept. 9

Sept. 15
..do....
Sept. 14
Sept. 19
Sept. 18

Sept. 19
..do....
Sept. 18
..do....

Dys.
7

1912.
Sept. 4
Sept. 3
...do...,
Sept. 2
Sept. 4

...do...
...do...
...do....
...do....
Sept. 2

Sept. 3
Sept. 4

...do....
Sept. 5

...do....

...do....
Sept. 6
Sept. 5
Sept. 6
...do....

Sept. 7

Sept. 6

Sept. 7

Sept. 6

Sept. 7

Sept. 8
Sept. 7
...do....
..do....
Sept. 13

Sept. 22
Sept. 23
Sept. 20
Sept. 25
..do....

..do....
Sept. 24
Sept. 25
..do....

Dys. 1912.

3 Sept. 10

5 Sept. 9
2 Sept. 10

6 I Sept. 9

4 I Sept. 10

4 ...do....

...do....

...do....
Sept. 9
Sept. 10

...do....
...do....
Sept. 11
...do....
...do....

...do....
Sept. 13
Sept. 11
Sept. 12
Sept. 13

Sept. 14
Sept. 12
Sept. 14
Sept. 13
Sept. 15

...do....

Sept. 14
Sept. 15
Sept. 14
Sept. 22

Oct. 6
Oct. 8
Oct. 6
Oct. 12
..do....

..do....
Oct. 10
Oct. 13
..do....

"3

il-fe-S

"S"^^

^%^

«!>>

0.2

bCo3 C

s

- V.

csfe^Ti

M

03 ft

•- g'.iy.S

A

* 9-S ir

B

0

;>^sa

\^

Eh

'F.

Dys.

Dys.

6

•27

71.48

6

26

71.33

7

27

71.48

7

26

71.33

6

26

71.57

6

26

71.57

6

26

71.57

6

26

71.57

5

25

71.42

8

26

71.57

7

25

71.80

6

25

71.80

/

25

72.40

6

25

72.40

6

25

72.40

6

25

72.40

1

24

76.58

6

22

73.20

6

22

72.95

7

23

72.65

7

24

72.66

6

22

73.18

7

24

72.66

7

23

72.65

S

25

72.74

7

24

72. 83

7

23

72.78

8

24

72.83

7

25

72.78

9

23

72.50

14

32

65.01

15

34

64.41

16

32

65.01

17

36

63.64

17

36

63.64

17

36

63.64

16

34

63.53

18

37

63.32

18

37

63.32

30

BULLETIlSr 19, U. S. DEPARTMENT OF AGRICULTUEE.

Table XII. — Maxinium, minimum, and average temperatures taken at the field labora-
tory, North East, Pa., from June 1 to October 31, inclusive.

June.

July.

August.

September.

October.

Dav of

the
month.

a

1

i

i

i

^

.1

a

3

i

a

3
.1

.

2

a

3

a

3

2

)«!

.g

.g

1

>

>

s

<

a

a

<

^

s

■<

^

S

<

s

a

<

° F.

° F.

° F.

0 p

" F.

° F.

° F.

" F.

° F.

° F.

" F.

" F.

° F.

° F.

° F.

1

70

50

60.0

72

53

62.5

66

52

59.0

84

65

74.5

57

49

53.0

2

78

64

71.0

75

58

66.5

69

53

61.0

86

68

77.0

64

45

54.5

3

77

59

68.0

82

68

75.0

63

64

63.5

81

69

75.0

70

54

62.0

4

76

60

67.5

83

68

75.5

65

49

57.0

79

69

74.0

67

56

61.5

5

69

44

56.5

84

68

76.0

65

54

59.5

87

68

77.5

70

51

60.5

6

67

54

60.5

84

70

77.0

70

50

60.0

84

69

76.5

77

54

65.5

68

46

57.0

92

72

82.0

71

55

63.0

86

70

78.0

69

49

59.0

8

59

38

48.5

87

71

79.0

78

54

66.0

77

56

66.5

58

43

50.5

9

66

- 45

55.5

85

73

79.0

78

66

72.0

77

62

68.5

71

51

61.0

10

65

58

61.5

80

72

76.0

78

67

72.5

83

68

75.5

67

56

61.5

11

70

55

62.5

87

69

78.0

76

63

69.5

89

69

79.0

73

50

66.0

12

78

60

69.0

85

66

75.5

76

61

68.5

74

58

66.0

74

54

64.0

13

68

49

58.5

82

65

73.5

80

67

7.3.5

76

54

60.5

59

46

52.5

14

61

48

54.5

87

69

78.0

79

59

69.0

78

68

73.0

59

45

52.0

15

78

60

69.0

83

73

78.0

69

63

66.0

80

69

74.5

55

44

49.5

16

72

57

64.5

92

61

76.5

72

56

64.0

82

60

71.0

55

39

47.0

17

II

57

67.0

74

63

68.5

67

53

59.5

62

49

55.5

63

46

54.5

18

69

50

59.5

77

63

70.0

69

64

66.5

69

59

64.0

71

56

63.5

19

65

48

56.5

82

57

69.5

78

67

72.5

73

60

66.5

63

52

57.5

20

64

57

60.5

65

52

58.5

71

63

67.0

69

54

61.5

54

45

49.5

21

71

57

64.0

75

63

69.0

75

65

70.0

68

57

62.5

71

48

59.5

09

67

59

63.0

77

63

70.0

76

60

68.0

79

63

72.0

65

56

60.5

23

69

49

49.0

73

54

63.5

75

65

70.0

II

56

66.5

56

43

49.5

24

70

50

60.0

72

60

66.0

69

57,

63.0

62

55

58.5

44

41

42.5

25

74

65

69.5

70

68

69. 0

80

71

75.5

69

61

65.0

48

44

46.0

26

SO

61

70.5

75

61

68.0

82

66

74.0

78

61

68.5

54

44

49.0

27

78

58

68.0

75

52

63.5

82

58

70.0

64

47

55.5

56

41

48.5

28.

82

67

74.5

70

57

63.5

62

52

57.0

56

43

48.5

60

47

53.5

29

77

64

70.5

75

64

69.5

59

54

56.5

63

47

55.0

70

55

62.5

30

83

59

71.0

73

57

65.0

67

48

57.5

51

36

43.5

63

64

54.5

31

72

52

62.0

63

59

61.0

54

44

49.0

SUMMARY OF SEASONAL HISTORY OF THE GRAPE LEAFHOPPER.

The grape leafhopper (see fig. 1, p. 1) hibernates as an adult
among accumuhitions of leaves and trash in vineyards, but mostly
in adjoining woodlands, hedgerows, and pastures. It becomes active
during the first warm days of spring and commences feeding on
the new growth of almost any of the plants with which it comes
in contact. With the unfolding of the grape leaves there is a gen-
eral migration of the insect to the vineyards. In normal seasons
this takes place about the middle of May in the vineyards of the
Lake Erie Valley. After feeding for a few days the leaf hoppers
mate, and oviposition commences early in June. The eggs are
deposited singly and are tucked under the epidermis beneath the
pubescence of the underside of the grape leaf. The average length
of the egg stage is from 11 to 15 days. The nymphs commence to
appear on the underside of the leaves about the 20th of June, and
b}^ the end of tlie first week in July a large percentage of the first
brood has hatched and is present in one of the several nymphal stages,

THE GRAPE LEAFHOPPER IN THE LAKE ERIE VALLEY. 31

of which there are five. (See PI. I.) The average length of tlie
nymphal period is about 28 days, but with many it varies from 20
to 35 days. At the hist nymphal molt the adults have fully devel-
oped Avings. A few newdy transformed adults may be found in
vineyards from about July 7 to July 12.

In normal seasons, however, the majority of the first-brood adults
appear after the middle of July. Observations of the development
of the insect indicate that if the nymphal period is lengthened by low
tempei-atures during the month of July, the number of adults of the
new brood that will mate and deposit eggs for a second brood is
(|uite small; whereas, if liigh temperatures prevail during the early
part of July, a large number of the nymphs are likely to develop
rapidly and make their transformation about the middle of July.
These early maturing adults mate and deposit eggs, and the resulting
second brood of nymphs is quite large.

Mating of the first-brood adults appears to be common for oidy a
few days. In 1912 few mating pairs were seen except (hning the
period from July 23 to July 27.

Early in August the color markings on the elytra of the adults
change from Ught yellow to a pale salmon color, which becomes
more intense as the season advances. After the appearance of this
change in coloration of the elytral markings little oviposition occurs.

By the early part of September most of the nymphs of both the
first and second broods have transformed to adults, although a small
number of nymphs may be found on the foliage until quite late in
the fall. Toward the middle and latter part of September the adults
commence to migrate from the vineyards and during warm, calm
afternoons may be seen in swarms drifting through the air in an
apparently aimless manner. They usually come to rest in adjoining
woodlands or rough pasture lands. Here they remain more or less
active during the warmer parts of the days of October and the late
fall, seeking the shelter of leaves and trash at night and during the
cooler days, and becoming less active as the cold weather of winter
approaches.

REARING CAGES USED.

Since the adult grape leafhoppers ai'e ver}' agile creatures it was
impossible to study their habits and life history in detail on the
large fruiting vines in the open vineyard. Yet in order that the
adults might oviposit and the eggs develop normally, it was neces-
sary that the insects studied should be confined on healthy growing-
grape fohage. For this purpose a large number of young grape-
vines, including several varieties, were planted in the garden of the
laboratory early in the spring of 1912. The vines were planted in
rows about 3 feet apart. Those vines used for securing egg records,

32 BULLETIN 19, U. S, DEPARTMENT OF AGRICULTUKE.

longevity of overwinteriiisj; adults, number of eggs deposited per
female, length of nymphal stages, etc., were covered wnth a cage
early in the season so as to prevent the foliage from bcnoming
infested by other adults.

Since it was im])ossible to secure enough Riley cages, or to have
cages made that were sufficiently tight to prevent the escape of the
adults, recourse was taken to the use of a number of second-hand
arc-light globes, which were seciu'ed from the local lighting plant.
These were about 15 inches high, with a small opening about 4 inches
in diameter and a large opening about 8 inches in diameter. The
globe was j)laced over the vine with the lower oj)ening resting on the
ground, and the larger opening was covered with a piece of muslin
fastened to a stout wire ring. This cover was drawn tightly over the
large opening by means of four cords fastened to the wu-e ring and
connected to four pegs driven into the ground and tightened in tlie
same manner as are the cords of a tent. In this way it was possible
to draw the muslin perfectly tight all around tlic edge of the upper
opening of the globe. The insects were examined during the cooler
part of the day when they were least active. It was found that when
the lower opening was set into the ground, the temperature inside of
the cage was several degrees higher than that on the outside, owing
to a lack of circulation of air inside the cage. This was overcome l)y
taking a strip of fine wire screen about 4 inches wide and forming
it into a collar a little larger than the smaller opening of the globe.
This collar was then slip})ed over the young grapevine and j)ressed
fu'mly into the soil. The globe was then placed over the vine and
the small opening fitted into the wire screen collar, thus securing an
an- current into the bottom of the cage up through the muslin cover
or vice versa. The muslin cover was then made large enough to
shade the greater part of the globe. These modifications resulted in
securing a cage that was light and tight, and that had a temperature
about the same as that on the outside.

The cage that has just been described (see PI. II, fig. 1 ) is spoken
of as an " arc-light globe cage" in connection with the rearing experi-
ments mentioned under seasonal history.

A smaller cage, employed for rearing single nymphs for the pur])()se
of recording the length of the stages of individuals, is fidly described
on page 26 under another caption dealing with experiments to deter-
mine the length of the nymphal stages.

PARASITES AND PREDACEOUS ENEMIES.

Apparently the grape leafhopper sufters litth^ from the attack of
parasitic enemies. No records of parasites have been found in the
literature dealing with tliis pest . During the investigations on grape
insect pests conducted at North East, Pa., from 1907 to 1912, only

THE GRAPE LEAFHOPPEK IN THE LAKE ERlE VALLEY.

33

one instance of parasitism was noted. In this instance, on July 31,
1907, Mr. P. R. Jones, of the Bureau of Entomology, ohserved the
female of Aphelopus sp. in the act of tlirusting her ovipositor into
the body of a nymph. No attempt was made to determine if eggs
were deposited in the body of this nymph, nor was any further evi-
dence of parasitism of the nymphs or the adults of the grape leafhopper
observed.^

On the other hand, the nymphs seem to be especially subject to the
attack of many predaceous insects, mites, and spiders, while the
adults become entangled in spider webs and are
preyed upon by the occupants.

The literature on the grape leafhopper con-
tains the following records of attack by preda-
ceous enemies on either the nymphs or the
adults :

B. D. Walsh, in 1862, records Hemerodromia
superstitiosa Say, one of the dance flies, as feeding
on the ''hoppers" in Illinois.

Townend Glover, in 1875, records Hyaliodes
vitripennis Say, the glassy-vdnged soldier-bug,
as feeding on the nymphs.

M. V. Slingerland, in 1902, records a mite,
Rliyncliolophus parvulus Banks, the larvas of
Clirysopa, and aphis lions as feeding on the
nymphs.

J. H. Quayle, in 1908, records the destruction
of the nymphs by the beetles and larvae of lady-
birds, aphis lions, and ants, but states that all
of these predaceous enemies put together have little apparent influ-
ence in lessening the number of the pest.

During the investigation of this pest at North East, Pa., aphis
Uons, ants, mites, and spiders were frequently observed preying upon
the nymphs, and in addition to them a very active orange-colored
mite {Anystis agilis Banks) was often found feeding upon the nymphs
and occasionally upon the adults, especially just after the latter had
transformed and had not the full use of their wings. Both the nymph
and the adult of a capsid of the genus Diaphnidia near D. Jiamata
Van Duzee were frequently found with nymphs of T. comes impaled
on tlieu" long probosces. Yet all of these predaceous enemies com-
bined failed to have any appreciable influence in reducing the destruc-
tive numbers of the leafhopper.

• While Mr. J. F. Strauss, of this bureau, was making drawings of adults of T. comes for this paper he
found an adult among some material in alcohol with the pupa of a dryinid (see fig. 13) attached to the body.
These specimens were collected by the writer in vineyards near Euclid, Ohio, Aug. 9, 19U.

Fig. 13.— Adult grape leaf-
hopper parasitized by a
dryinid, and showing
cocoon of parasite pro-
truding from abdomen, at
left. Greatly enlarged.
(Original.)

34 BULLETIN 19, TJ. S. DEPABTMENT OP AGRICULTURE.

NATURAL CHECKS.

It would seem, however, that there are some as yet unknown
natural checks which greatly reduce the numbers of this insect and
occasionally almost entirely eliminate it over areas where only a short
time previously it had been a serious pest.

In 1865 Trimble observed that once when the thermometer reached
100° F. thousands of the "hoppers" were killed.

There was a great diminution in numbers of the adults in the
infested area of the Chautauqua County vineyards early in the season
of 1903.

A condition similar to this was observed by Mr. E. W. Scott, of
the Bureau of Entomology, during the season of 1912, when adults
of Typhlocyha tricincta were so very abundant in the vineyards near
Benton Harbor, Mich., that the vineyardists became greatly alarmed,
many of them making preparations to spray the nymphs when they
should appear. Yet this proved unnecessary, for when the time arrived
for the nymphs to appear upon the foliage in large numbers most
of the adults had disappeared and very few nymphs of the new
brood had hatched. As yet nobody appears to be able to account
for these sudden disappearances of the pest or to determine whether
they are due to climatic or other causes.

In September, 1890, Thaxter observed that in Connecticut grape
leaf hoppers in large numbers were injuring a vineyard. He foimd
that they were attacked by a fungous disease (Empusa sp.) which
apparently destroyed all of them. This is the only case on record
in which this insect was attacked by a fungous disease. Nothing of
this nature has been observed in the vineyards of the Lake Erie
Valley during the present investigation, and for the past four or five
seasons the pest has steadily increased. Probably the time may not
be far distant when large numbers of them will suddenly cUs appear,
as happened at Westfield, N. Y., in the season of 1903. However, it
is by no means safe for the vineyardist to count on these natural
checks, for while one is waiting for reUef fi'om such a source the pest
may work incalculable damage to his vineyard.

REMEDIES.

During the period that this insect has attracted the attention of
economic entomologists much experimental work has been undertaken
to determine the most effective means for its control. Early in the
control work undertaken against this pest, tobacco, in some form or
other, was employed as a killing agent. In 1828 Fessenden (see
Bibliography) recommended the smoking of infested vines by burning
tobacco stalks beneath them.

THE GKAPE LEAPHOPPEE IN THE LAKE EBIE VALLEY. 35

In 1843 J. F. Allen (see Bibliography) advised syringing or spraying
infested vines and also smoking them by burning tobacco stalks.
Since this date the use of tobacco in both of the forms mentioned has
occupied a prominent place among substances recommended for the
control of the grape leafhopper. The former method, that of fumiga-
tion, however, was impracticable for the open vineyard. In fact, it
is quite probable that the process of fumigation with tobacco was
originally intended for use against the insect when found infesting
grapevines gromng in hothouses which could be closed during the
period of treatment. On the other hand, the use of a liquid tobacco
decoction has withstood the test of numerous experiments in com-
parison with a large number of liquid spray materials and at the
present time is the insecticide most generally recommended in making
spray applications against the nymphs.

In the following paragraphs is presented a list of substances and
mechanical methods either experimented with or recommended by
various entomologists (see Bibliography) since this insect has been
a pest of economic importance:

Liquid sprays. — Syringing with tobacco water or soapsuds (W. Saunders, 1870).
Spraying with carbolic acid (W. L. Devereaux, Rural New Yorker, 1883). Spraying
with kerosene and water, or sheep dip (O. Lugger, 1896). Spraying the adults
with kerosene and water and the nymphs with whale-oil soap (M. V. Slingerland, 1904).

Dust sprays. — Dusting with lime and sulphur (C. J. S. Bethune, 18G8). Dusting
with hellebore (W. Saunders, 1870).

Other mechanical methods. — The use of sticky shields to trap the adults; torches to
attract the adults (C. V. Riley, 1873). Destruction of leaves to destroy adults in
hibernation (A. J. Cook, 1875). Sticky shields and cloth wet with kerosene to trap
adults (J. A. Lintner, 1887). Sheets of cardboard smeared with tar to trap adults
(F. M. Webster, 1893). Burning of leaves and rubbish in and surrounding vineyards
to destroy adults in hibernation (O. Lugger, 1896). Sticky fans to catch adults as they
fly from vines; collecting nets to catch adults (C. W. Woodworth, 1897). Box or cage
having inside smeared with a sticky substance ; the cage is placed over the infested
vine and the "hoppers" are caught on the sticky sides and bottom of the cage (H. J.
Quayle,1908). Sticky shields held on both sides of the trellis (M.V. Slingerland, 1904).

Many of the methods of control mentioned in the foregoing para-
graphs have been recommended by various other authors treating
this subject. The foregoing simply indicate the date of their first
mention in literature.

In his experimental work in vineyards m Chautauqua County,
N. Y., Slmgerland carried on quite extensive experiments with
sticky shields for catching the adults before the commencement of
egg deposition, the most practical shield for trellised vineyards being
constructed and used as follows :

Make a light wooden frame about seven or eight feet long and four feet wide, hav-
ing the bottom crosspiece about a foot from the ground and fasten to this stiff wires
extending down nearly to the ground and bent inward something like hay-rake teeth.
Tack over this a strip of table oilcloth ]]- yards wide and let it extend down over the

S6 BULLETIN 19, U. S. DEPARTMENT OF AGEICULTURE.

curved wire teeth, so that when the shield is held beside a vine, the oilcloth will come
under the vine to catch the "hoppers" that try to drop to the ground. Cover the oil-
cloth with the "stick-em" and all is ready to operate. Two men, each carrying one
of these light sticky shields on opposite sides of a trellis of vines, can reach over the
shields, jar the Adnes to disturb the '"hoppers" and thus go over an acre of vineyard
in a little more than an hour.

In California, where the vines are not trained to a trellis, Mr.
Quayle found that a screen cage having the inside smeared with crude
oil, with one side open and a V-shaped opening cut in the bottom
to admit the stem of the vine, could be used quite effectively
in the vineyards to catch the adults before egg deposition com-
menced. In the course of his field experiments in California Mr.
Quayle conducted experiments with suction apparatus for collecting
the adults from the vines. He also attempted to destroy them with
torches; by the application of dry powders, including lime, helle-
bore, and dry sulphur; and also by the fumigation of infested vines,
both with cyanid and sulphur gas. None of these latter methods
gave results of a practical nature, and the only mechanical method
of control against the adults recommended by him is that of the
screen cage previously mentioned.

Destruction of leaves and trash. — Many authors have urged the de-
struction of leaves and trash in and adjoinmg mfested vineyards,
while the insects are in hibernation, as a means of lessening their
numbers. However, since the adults rise in the air and either fly or
are carried considerable, distances by the winds during the migrations
which take place during the spring and fall, there are usually large
areas of wood lots and pasture lands at considerable distances from
vineyards where swarms of the adults may be found during the
winter. Since in many cases these areas of rough land are not con-
trolled by the owners of the vineyards there is slight possibility that
this cleanmg-up process will be undertaken on a large enough scale
to be of any great value in lessening the numbers of overwmtering
adults. Furthermore, at the present time there is a strong tendency
toward the growing of some form of cover crop, such as clover, vetch,
turnips, rye, oats, etc., in vineyards as a means of furnishing soil
protection and fertility; and this is very necessoj"y and desirable in
most of the vineyards of the Lake Erie Valley. This would have to
be abandoned if thd clean-culture method were followed. Observa-
tions along this line covering several seasons indicate that where
cover crops are growing in badly infested vineyards the number of
adult grape leafhoppers found among the shelter thus afforded is
generally very small compared with the number that have migrated
to adjacent wood lots and rough pasture lands. In fact, it would
appear that there is a tendency for the larger percentage of adults to
migrate from the vineyards in the fall, and this migration appears to
be their chief mode of dispersal as much as a means for securing suit-

THE GKAPE LEAPHOPPER IN THE LAKE EEIE VALLEY. 37

able hibernating quarters. Hence too much should not be expected
of this destruction of leaves and trash on a limited scale, since in the
following spring the adults are likely to swarm back mto the vine-
yards from areas not included in the cleaning-up process.

SPRAY TREATMENT.

During recent years a great deal of attention has been given to
combating this pest by means of liquid sprays. Owing to the agility
of the winged adults, and also to the fact that their sloping wing
covers protect their soft bodies from the kilUng action of spray
liquids not sufficiently caustic to injure the foUage of the grapevines,
it is a very difficult task to destroy many of them with Uquid spray
applications. This was demonstrated by Prof. SUngerland in his
field experimental work in the vineyards of Chautauqua County,
N. Y., during the outbreak of 1901-2. Since it frequently happens
that during seasons of heavy infestation the hibernating adults
appear on the new fohage in injurious numbers and cause consider-
able alarm among the vineyardists, he attempted to combat them by
means of a kerosene and water spray. He found, however, that the
margin between the percentage of oil necessary to kill the adults and
the percentage that would seriously injure the grape fohage was so
small that more injury to the vines was likely to occur than would
ofi^set the benefit derived from the number of fljdng adults that were
killed by the process.

Much greater success, however, was secured by him in spray appfi-
cations made against the nymphs by the use of whale-oil soap at
a strength of 1 pound of the soap to 10 gallons of water. With
this spray liquid he was able, by one thorough appfication when the
majority of the nymphs were present on the foliage, to reduce their
numbers to such an extent that those remaining caused no serious
mjury to the vines for the remainder of the season.

In experiments with fiquid sprays consistmg of 1 pound of whale-
oil soap to 1 5 gallons of water i\Ir. Quayle was able to destroy a very
large percentage of the nymphs infesting grapevines in California.
He was also able to obtain good results by the use of a spray consist-
ing of 1 jjound of resin to 15 gallons of water, using enough lye or
potash completely to dissolve the resin. This required 1 pound of
lye to about 8 pounds of resin.

The cliief objections to the use of whale-oil soap are the very
offensive odor connected A\dth its appfication and the fact that since
the vines have to be thoroughly drenched mth the spray in order to
strike the imderside of all of the leaves, the clusters of grapes are also
necessarily drenched. This soapy fiquid has a tendency to form in a
drop on the lower part of each berry, and after the moisture has evap-
orated a white stain remains which makes an undesirable discolora-

38 BULLETIN 19, U. S. DEPARTMENT OF AGRICULTURE.

«

tiou on the purple surface of the ripened grapes, rendering them
unattractive for table use.

During the last few years commercial brands of tobacco extracts
have come much into use as liquid spray substances for the control
of soft-bodied sucking insects. Hence once more, after a period of
over 80 years since it was first recommended, tobacco appears to be
the most promising insecticide for the control of this pest.

During the seasons of 1910 and 1911 the grape leafhopper was
present in very injurious numbers in many vineyards in the Lake
Eric Valley. Vineyard experiments were undertaken by the Bureau
of Entomology in the vicinity of North East, Pa., using the tobacco
extracts as liquid sprays against the nymphs. The results of these
experiments were very gratifjdng, since with one thorough applica-
tion of the tobacco extract the numbers of these insects in the treated
vineyards were so greatly reduced and the injury was so slight that
the foliage retained its dark green color throughout the season, the
cane growth was strong and well matured, the berries were large, the
fruit sweet, and the size of the crop considerably increased ; whereas,
on the untreated portion of the vineyards the foliage turned brown
and dropped prematurely, the cane growth was stunted, the berries
were undersized and lacking in sugar content, and the tonnage per
acre was much less than on the sprayed portions of the vineyards.

Detailed reports of these vineyard experiments against this pest
are given in Part I of Bulletin No. 97 and Part I of Bulletin No. 116
of this bureau.

SPRAY MATERIAL.

The forms of tobacco extract used in these experiments in 1910
and 1911 were the blackleaf tobacco extract containing 2.70 per cent
nicotine sulphate and the blackleaf tobacco extract containing 40
per cent of nicotine sulphate. The blackleaf tobacco extract con-
taining 2.70 per cent of nicotine was effective in kiUing all of the
nymphs which were thoroughly wetted by the spray, when applied
at a dilution of 1 part of tobacco extract to 150 parts of water or
Bordeaux mixture. The blackleaf tobacco extract containing 40
per cent nicotine sulphate was found to be effective at a dilution
of 1 part of tobacco extract to 1,500 parts of water or Bordeaux
mixture. Both of these forms of tobacco extract appear to be
equally effective in destroying the nymphs at the dilutions men-
tioned. The one containing the smaller percentage of nicotine
(2.70 per cent), however, necessarily contains more sticky inert mat-
ter. When this is applied as a spray to the vines late in the season,
i. e., toward the middle of August, and when little rainfall occurs
before the harvesting season, some of this sticky substance may ad-
here to the ripe grapes, giving the skins a slight flavor of tobacco.

THE GKAPE LEAFHOPPER IN THE LAKE ERIE VALLEY. 39

It was noted that this condition obtained during the dry fall of 1910.
The ''blackleaf 40" tobacco extract does not appear to carry so much
of this sticky substance, and owing to the greater dilution that is
possible in its use the dilute spray liquid is almost clear; hence there
is not the hkeUhood that it will leave the undesirable stain on the
ripened fruit. It should be stated, however, that neither of these
extracts is likely to leave the unpleasant stain or odor on the fruit
if applied in the early part or middle of July, which is usually the
period at which the maximum benefit is to be derived from them in
the destruction of the nymphs.

SPRAYING APPARATUS.

Various types of spraying machinery are used by the vineyardists
of the Lake Erie Valley. It was on account of the depredations of
the grape rootworm, requiring a spray application to the upper sur-
face of the foliage, that the use of spraying machinery in vineyards
became general. The sprayer in general use for this work is of the
tractor type (PI. Ill, fig. 1), the power being generated either by a
chain or an eccentric gearing connecting the wheel and the pump.
Thus in order to maintain a uniform liigh pressure with this type of
machine it is necessary to keep it in motion. Although most of these
macliines are supphed with a large air chamber so that the pressure
is held quite steady and does not vary with every stroke of the plun-
ger, yet as soon as the wheels of the machine stop turning the pressure
drops quite rapidly.

Other types of sprayers in use for vineyard work are compressed-air
l)ower outfits, gasohne-engine power outfits, and steam power outfits.
With all of these latter types the pressure is independent of the rate of
movement of the macliine through the vineyard rows.

In making spray applications against the nymphs of the grape
leafhopper it is necessary to apply large quantities of spray Hquid to
the underside of the infested grape leaves. Where the foUage is quite
dense the amount of spray required for thorough work may amount
to from 200 to 300 gallons per acre, whereas in making applications
to the upper surface of the fohage against the beetles of the grape
rootworm thorough work can be done on quite dense fohage with
about 100 to 125 gallons of Hquid per acre, and this may be accom-
phshed wliile the team is being driven slowly.

During the seasons of 1911 and 1912 all of the tyj^es of spray ma-
clnnery previously mentioned were observed in use in spraying against
the grape leafhopper, and in the hands of careful operators effective
work was accomphshed with all of them.

It should be stated that in all cases observed, with the exception
of the steam-engine power outfit, aU of the spray apphcations were
made by the trailer method. That is, the operator directed the spray

40 BULLETIN 19, U. S. DEPARTMENT OF AGRICULTURE.

to the underside of the grape leaves by holding a short rod, one end
connected to the spray hose and the free end carrying a large nozzle
of the cyclone type directed upward at right angles to the rod. (See
PI. Ill, fig. 1.) Effective results in kilHng the nymphs by this method
appeared to depend more upon the person manipulating this rod than
upon the type of sprayer used or the number of pounds of pressure
apphed, providing the pressure was not allowed to drop below 75
pounds. Of course wdth the higher pressure larger areas can be cov--
ered in a given time than with the low pressure. Yet the most effec-
tive work done in the control of this pest coming under observation
of the writer was accomphshed with a tractor machine, with a pressure
fluctuating between 70 and 125 pounds, in the hands of a very thorough
vineyardist. This feature is emphasized here because the small vine-
yardist, being under the impression that an expensive liigh-pressure
spray outfit is necessary, is frequently deterred in attempting to con-
trol this pest, whereas the most important thing is care in the direction
of the spray so that the greatest number of nymphs will be drenched,
and this can- be done with the same tractor machine that is used for
apphcations against the grape rootworm. On the other hand, it is
doubtless much more economical for the vineyardist with large areas
to cover to have larger high-pressure outfits, since with them two or
even more leads of hose may be used (PL III, fig. 2) , making it possible
to cover large areas in a very short time. This is highly desirable,
since there are only about 8 to 12 days during which the maximum
number of nymphs is present upon the fohage.

In order to lessen the time required to make the apphcation and
to reduce the cost, many attempts have been made to apply the spray
to the underside of the grape fohage by means of a fixed nozzle ar-
rangement instead of making the apphcation by the trailer method
described above. The chief difficulty arising in the use of a fixed-
nozzle arrangement is that such a device apphes no more hquid to
a vine carrying a large amount of dense fohage than to one carrying
a moderate amount of more widely spaced fohage ; hence it frequently
happens that much more spray than is necessary is apphed to the
vine carrying hght fohage and not enough is apphed to the one carry-
ing dense fohage.

The types of fixed-nozzle arrangement are being tried out in the
vineyards of the Lake Erie. Valley. One of these was for a tractor or
a gasohne-engine power sprayer, and was devised and used by Mr.
F. Z. Hartzell.^ The other arrangement was used for a steam-engine
power sprayer. (PL II, fig. 2.) Both of these arrangements are
reported to have given fairly satisfactory results in kilhng nymphs
where the fohage was not very dense. In most cases, however, suc-

1 Bui. 344, N. y. (Geneva) Exp. Sta., Pis. I-IV.

Bui. 19, U. 5. Dept. of Agriculture.

Plate III.

Fig. 1.— Rod and Single Cyclone Nozzle Used to Apply Spray to Underside of
Grape Foliage. Power Supplied by Tractor Sprayer. Vineyard of Mr. H. H.
Harper, North East, Pa. (Original.)

Fig. 2.— Gasoline-Engine Sprayer Supplying Power for Two "Trailer" Leads
of Hose in Spraying Against the Grape Leafhopper. Vineyard of Mr. J. E.
Beatty, North East, Pa. 'Author's Illustration.)

THE GRAPE LEAFHOPPER.

THE GRAPE LEAFHOPPER IN THE LAKE ERIE VALLEY. 41

cess with any type of spray apparatus in present use in work against
this pest appears to depend more on the care and ingenuity of the
intUvidual operator than upon the great superiority of any given type
of machine over another.

RECOMMENDATIONS.

Efforts to control the deprechitions of the grape leafhopper by the
destruction of the winged adults, by burning over or cleaning up
their hibernating places adjacent to vineyards, by trapping them on
sticky shields, or by endeavoring to treat them with contact sprays
when they appear on the new growth of the grapevines in spring
before oviposition takes place, have proven far from satisfactory.
Although these methods may furnish a certain measure of relief over
very limited areas, they are of very slight practical value as control
measures when serious infestations occur in large vineyards.

Observations indicate that except in seasons of extremely heavy
infestation, or over limited areas, the injury wrought by the over-
Avintering adults in spring to the new growth is not likely to reduce
greatly the entire seasonal growth of the infested grapevine provided
a large percentage of their offspring in the form of nymphs can be
destroyed before they reach the adult stage. In other words, it is
the steady drain made on the infested grapevines from the time the
overwintering adults attack them in spring, combined Avdth the
unchecked attack of the nymphs and adults of the new brood until
late September, that results in serious injury by curtailing the size of
the crop and the growth of the vme.

That the nymphs can be controlled by the spray method has been
thoroughly demonstrated. Successful control of the nymphs by this
method depends on thoroughly wetting all parts of the underside of
the infested leaves with the spray liquid.

Tobacco extracts have given excellent results, used according to
the following formulas :

I. Tobacco extract containing 2.70 per cent nicotine sulphate, diluted at the ratio of
1 part to 150 parts of water.

II. Tobacco extract containinc 40 per cent nicotine sulphate, diluted at the ratio of
1 part to 1.500 parts of water.

The killing equality of the tobacco extract is apparently just as
effective when added at the same dilution to the Bordeaux mixture
and arsenata of lead spray liquids, which are used to control fungous
diseases and chewing insect enemies of the grapevine, as when used
with clear water. No injury results from combining these spray
mixtures, namely, tobacco extract, Bordeaux mixture, and. arsenate
of lead. However, the tobacco extract should not be mixed with
spray mixtures containing ar^enicals in the form of Paris green or
arsenito of lime, for serious injury to the foliage is likely to occur as
a result of the combination.

42 BULLETIN 19, U. S. DEPARTMENT OF AGRICULTUEE.

The most effective time to make the tobacco spray appHcation
against the nymphs is just before those that hatched earhest in the
season luive reached the fourth moh-. This can be determined by
the length of the wing pads (PI. 1) which, in the fourth stage, extend
about one-third the length of the abdomen. At this time a larger
number of nymphs are likely to be present on the vines than at any
other time during the season. In the vineyards of the Lake Erie
Valley this condition occurs toward the end of the first week in July,
and the most effective work with the tobacco-spray liquid may be
done during the two weeks following this date. After this period,
or toward the end of July, a large percentage of the nymphs of the
first brood will have transformed to winged adults, and these latter
can not be successfully treated with the diluted tobacco spray.

In vineyards where black-rot, mildew, the grape rootworm, and
the grape-berry moth occur, it is suggested that arsenate of lead
and Bordeaux mixture be used with the tobacco extract to take the
place of the second spray application in the schedule of treatment
recommended against these diseases and insect pests.

Wlien it is deemed expedient to use sticky shields to capture the
winged adults before oviposition takes place, the best sticky sub-
stance for this purpose, according to Slingerland, is a mixture of
melted resin, 1 quart, in 1 pint of castor oil, smeared liberally over the
face of the shield.

CONCLUSIONS.

Typhlocyha comes, the species of grape leafhopp«r discussed in
this paper, is at the present time a very destructive enemy of the
grapevine throughout the vineyards of the Lake Erie Valley. For
several seasons it has caused great losses to the vineyardists of this
region by reducing the yield and quality of the grape crop and by
curtaihng the growth and lowering the vigor of the vines. The
vineyardist who desires to maintain his vines in full vigor and produce
high-quality fruit can not afford to allow this pest to develop in
destructive numbers in his vineyards, for if not controlled sooner or
later it is almost sure to occasion serious loss. Field experiments
prove conclusively that this pest can be controlled by spraying
against the nymphs with a tobacco-extract solution.

The hfe-history studies recorded in the preceding pages show that
there is only one full brood of nymphs a yeai' in the region of the
Great Lakes.

The spraying experiments recorded in Part I of Bulletin 97 and
Part I of Bulletin 116 of the Bureau of Entomology indicate that a
single thorough spray application, made when the greater percentage
of the nymphs of this brood is present on the underside of the grape
leaves, will so reduce their numbers that injury to the crop and the

THE GRAPE LEAFHOPPER IN THE LAKE ERIE VALLEY. 43

vines for the remainder of the season by those that escape the spray
action will be very slight.

In the vineyards of Ohio, west of Cleveland, mid in the vineyiU"ds
of Michigan another species of grape leafhopper, Typhlocyha tricincta
(figs. 6 and 7, pp. 10, 11), is the predominant and destructive species.
The life history and habits of this species, however, are so nearly
identical with those of Typhlocyha comes that the remedial treatment
recommended for the latter can also be used with success against the
former, namely, the application of the tobacco-extract spray to the
nymphs at the time they appear in maximum numbers upon the
underside of the grape leaves, which for these States is during the
last few days in June or very early in July.

BIBLIOGRAPHY.

1825. Say, Thomas. Descriptions of new hemipterous insects collected in the
expedition to the Rocky Mountains. Journ. Acad. Nat. Sci. Phila., vol. 4,
pp. 307-345.
Description of T. comes, p. 343.

1828. FESSENDE>f, T. G. New American Gardener, pp. 299-300. Boston.

Brief descri]Hion of the grape leafhopper and its injury to the grapevine. Remedy: Smoking
vines with tobacco stalks.

1841. Harris, T. W. Report on the insects of Massachusetts injurious to vegetation,
pp. 182-185. Cambridge.

"The leaf-hoppers (Tettigoniadse)." Description, life history, habits, injury to grapevines.
1843. Allen, J. F. Practical treatise on tlie grape vine, p. 154.

Brief mention. Remedies: Syringing with tobacco water, or smoking with tobacco stalks.

1848. Horticulturist [Downing], vol. 3, pp. 28-29.
Brief mention. Remedy: Tobacco water.

1855. Glover, Townend. Report of the [U. S.] Commissioner of patents for 1854.

Agriculture, pp. 77-78.

"The vine-hopper." Habits of insect, injury to grapevines. Remedy: Fumigation with
tobacco.

1856. Fitch, Asa. Third report on * * * the insects of * * * New York,

pp. 391-393.

" Vme leaf hoppers." Brief descriptions of Typhlocyba, Erythroneura, and Empoa. Discus-
sion of injury to grapevines.

1864. Walsh, B. D. Proc. Best. Soc. Nat. Hist., vol. 9, pp. 317-318.

"Erythroneura." Description of three species and mention that E. vitis Harris, E. vulnerata
Fitch, E. vitifex Fitch, and E. tricincta Fitch belong to this genus.

1867. Walsh, B. D. Pi-act. Ent., vol. 2, pp. 49-52.

"The true thrips and the bogus thrips." Explaining difference in appearance and habits of
true thrips and the grapevine leafhopper.

1868. Bethune, C. J. S. Canadian Farmer, vol. 5, p. 7.

"Grape-vine tree-hopper ( Tettigonia vitis Harris)." Description, habits, injury. Remedies:
Dusting with sulphur and lime; fumigating with tobacco.

1869. W^ALSH, B. D., and Riley, C. V., eds. Amer. Ent., vol. 1, p. 227.

" Grapevine leaf-hopper." Brief note recommending syringing with strong tobacco water.

1870. Saunders, William. Report of the Fruit Growers Assn., Ont., for 1870, pp.

111-113.

"The thrips (so-called) ( Tettigonia vitis, Harris)." Life history, habits, injury. Remedies:
Syringing with tobacco water, soapsuds, dusting with hellebore, fumigating with tobacco.

44 BULLETIN 19^ U. S. DEPARTMENT OF AGRICULTURE.

1871. Glover, Townend. Report i>f the [U. S.] ('(iiiuni,s,sioiuT of Agriculture for
1871, pp. 85-8G.

"The griipo-vino hopper (Krytltroneura ( Teltigonia) vitis)." Life hLstory and habils, injury
to grapevines. Remedies: Spraying with tobacco water, soapsuds, trap lights, etc.

1874. IliLKY, ('. V. Trans. 111. State Ilort. Soc, new ser., vol. 7, p. 138.

Brief mention; suggests use of sticky substance on stallc of vine in spring, sticky shields, torches.

1875. Cook, A. J. Thirteenth Annual Report of the State Board of Agriculture,

Michigan, for 1874, p. 14fi.

" Orape-vine leaf-hopper ( Erythroneura vitis)." Brief account of habits and injury. Remedy:
Destruction of leaves.

1877. Glover, Townend. Report of the U. S. Commi.ssioner of Agriculture for

1876, pp. 32-33.
" Erythroneura ( Tcttigonia) vitis." Hrief discussion of habits and remedies.

1878. Perkins, G . II . Fifth Report of the Vermont Board of Agriculture, pp. 285-286.

" Erythroneura vitis Harris." Life history, injury. Remedies: Washes — lye, soapsuds, tobacco
water; fumigating vines with tobacco.

1880. Riley, C. V. Amer. Ent., vol. 3 (ser. 2, vol. 1), p. 182.

"Terrestrial insects in stomach of shad." Mention of a Typhlocyba, probably vitis.

1883. Devere.\ux, W. L. Rurnl New Yorker, vol. 42, ]>. 474.

"The grape-vine hopper." Brief mention of habits and injury to grapevines. Remedies:
Fumigation with tobacco, spraying with carbolic acid.

1883. S.\UNi)ER.s, WiLLi.\M. Insects Injurious to Fruits, pp. 286-288.

"The grape-vine leaf-hopper (Erythroneura vitis)." Life history, habits, injury, remedies.

1884. Uhler, p. R. Standard Natural HLstory [ed. J. R. Kingsley], vol. 2, p. 24fi.

Brief description and note on habits and distribution.

188G. Lintner, J. A. Thirty-third Annual Report Massachusetts Board of Agricul-
ture for 1885, pp. 191-195.
"The grapevine 'Thrips.' " Discussion of habits, injury, and remedial measures.

1887. Lintner, J. A. Cultivator and Country Gentleman, vol. 52, p. 493.

"Grapevine leaf-hoppers." Brief description, habits, injury to grapevines. Remedies:
Spraying with tobacco infusions, soapsuds, sticky shields.

1888. Fernald, C. H. Mass. Hatch Exp. Sta., Bui. 2, pp. 3-5.

"The grape-vine leaf-hoppers." Life history, nature of injury to vines, remedial measures.

1888. Marvin, D. S. Rural New Yorker, vol. 47, p. 570, Septeml)er 1.

"Thrips, Tcttigonia vitis." Brief description. Mentions as remedies tobacco water, pyr-
ethrum-kerosene emulsion, and strong carbolic .soapsuds.

1889. Bethune. C. J. S. Ninth Annual Report of the Entomological Society of

Ontario, 1888, pp. 63-66.

"The grape-vine leaf-hopper {Erythroneura vitis Harris)." Detailed dis;m.s.sion of injury, hfe
history, habits, and remedies.

1889. WooDWORTH, C. W. P.syche. vol. 5, pp. 211-214.
"North American Typhlocybini."

1889. Fernald, C. H. Orange Judd Farmer, vol. 5, no. 20, p. 315, May 18.

"The grape-leaf hopper." Habits, injury. Remedies: Smoking vines in graperies, syring-
ing with soapsuds, tobacco water, torches.

1889. Fernald, C. H. Annual Report of the Massachusetts Hatch Experiment Sta-

tion, pp. 21-23.
"The grape-vine leaf-hoppers." Brief statement of life liistory and injury.

1890. Provancher. Abbe L. A. Petite Faune Entomologique du Canada, vol. 3,

l)p. 298-299.
Descriptions of Erythroneura vitis, E. vitifex, and E. vutnerata.

1890. Cassidv, .Tame.s. Colo. Agr. Exp. Sta., Bui. 6, p. 20.

Brief mention of two undetermined species of Erythroneura occurring on apple and grape.

THE GRAPE LEAFHOPPER IN THE LAKE ERIE VALLEY. 45

1890. Felton, W. B. Annual Report of the Colorado Stale IJfjrliciillunil and For-
estry Association, vol. 5, 1889, pp. 573-57(;.

"CodUng moth and leafhopper." Remedies: Burning leaves, torches, spraying with tobat-eo
decoction, sticky shields.

1890. Thaxter, Roland. Annual Report Connecticut Agricultural Experiment

Station for 1890, j). 97.
Brief mention of infestation l)y fungous disease.

189 L Blount, A. E. New Mex. Agr. Exp. Sta., Bui. 2, p. [6].

"The vinehopper (Tettigonia vitis.)" Brief mention of Injury to vines. Remedies: To-
bacco fumigation and kerosene sprays.

189L (iiLLETTE, C. p. Colo. AsT. Exp. sta.. Bui. 15, pp. 18-22.

"The grape-vine leaf-hopper." Gives Harris's description of Tettigonia vitis and a brief list
of remedies which may be effective.

1891. Fletcher, Jame.s. Can. ('entr. Exp. Farm, Bui. 11, p. 21, May.

"Grape-vine leaf-hopper { Erythroncura vitis Harris)." Brief mention. Recommends clean
culture and spraying with kerosene emulsion.

1891. TowNSEND, C. H. T. New Mex. Agr. Exp. Sta., Bui. 3, pp. 3-6.

"Insects injurious to the vine." Life history; mentions possibility of third brood. Reme-
dies: Kerosene emulsion, "LX.L." compound, tobacco water, and "shield method."

1891. LiNTNER, J. A. Cultivator & CcTuntry Gentleman, vol. 56, p. 815, October 8.
"Grapevine leaf-hopper." Brief discussion of habits and injury. Remedies: Sticky shields,
cloth wet with kerosene.

1891. Weed, C. M. Insects and Insecticides, pp. 123-124. Hanover, N. H.

"The grape-vine leaf-hopper (Typhlocyba vitis).'' Life history. Remedies: Pyrethrum,
tobacco dust, sticky screens.

1892. TowNSEND, C. II. T. New Mex. Agr. Exp. Sta., Bui. 5, pp. 3-5.

"Thevine leaf-hopper ( Typhlocyba vitis)." A r&um^ of paper in Bulletin 3 of the New Mex-
ico Station.

1892. Gillette, C. P. Annual Reports Colorado State Bureau of Horticulture for

1891-2, vol. 6, pp. 233-235.

"'I'he western grapevine leaf-hopper (Typhlocyba viti/ex Harris, var. coloradoensis GUI.)."
Description. Life history, two brooded. Remedies: Spraying with kerosene emulsion, sticky
shields.

1893. Fitch, Asa. Catalogue of the insects collected and arranged for the State

Cabinet of Natural History. Reprint in Lintner, 9th Rept. Inj. Ins. N. Y.
f. 1892, pp. 383-409.

"Erythroneura," pp. 402-403. Brief descriptions of E. vulnerata, E. vitis, and E. tricincta.

1893. Webster, F. M. Twenty-sixth Annual Report- Ohio State Horticultural

Society for 1892-93, pp. 63-70.

"Insects of the year." Brief statement of use of tar-smeared cardboard in destroying adults
in vineyards of New Jersey, p. 67.

1894. OsBORN, H. Report of the Iowa State Horticultural Society for 1893, vol. 28,

pp. 262-264.

"Insects affecting grapes." General discussion of life history, injury to vines, and remedial
measures against Typhlocyba vitis, p. 263.

1894. PYetcher, James. Reports Experimental Farms, Canada, for 1893, p. 181.

"The grape-vine leaf-hopper." Brief mention of habits and injury; remedies.
1894. \'an Duzee, E. p. Catalogue of the described Jassoidea of North America.
Trans. Amer. Ent. Soc, vol. 21, pp. 245-317.
" Typhlocyba comes," p. 312.
1891. Grave.stock, J. Semi-annual Reports Colorado State P.oard of Horticulture
for 1893-94. vol. 7, pp. 229-233.

Brief mention of remedies: Kerosene emulsion, hot water, |)p. 22ii-2:i().

46 BULLETIN 19, U. S. DEPARTMENT OF AGRICULTURE.

1895. (iiLLKTTK, 0. P., aud Baker, 0. F. Colo. Agr. Exp. Sta., Bui. 31, p. 113.
" Typhloq/ba viti/ex Hair. var. coloradensis Gill." Brief mention of date collected.

1895. CoMSTOCK, J. H. Manual for the Study of Insects, p. 154. Ithaca.

"The grape-vine leafhopper (ErylhroneuTa vilis)." Brief mention of appearance, habits, and
remedie.s.

1896. Lugger, Otto. Minn. Agr. Exp. Sta., Bui. 48, pp. 61-65.

"Grape-vine leaf-hoppers (Typhlocyba sp.)." Discussion of application.s: Kerosene and
water, sheep dips. Recommends burning leaves and rubbish to destroy hibernating adults.

1896. Marlatt, C. L. U. S. Dept. Agr., Yearbook, 1895, pp. 400-402.

" The graj>e leaf-hopper ( rj/pft^ocj/fta vili/ez Fitch)." Injury, life history, habits. Remedies:
Kerosene emulsion, sticky shields.
1896. Marlatt, C. L. Amer. Nat., vol. 30, p. 759, September.

"Grape insects." Review of U. S. Dept. Agr. Yearbook article, 1895.

1896. Slinoerland, M. V. Rural New Yorker, vol. 55, p. 689, October 17.

"The grapevine leaf-hopper." Brief discussion of life history, injury to grapevines. Reme-
dies: Spraying with kerosene emulsion, tobacco dust, sticky shields.

1896. Smith, J. B. Economic Entomology, ed. 2 rev., pp. 148-149. Philadelpliia.

"The grape leaf-hopper ( Erylhroneura vitis)." Brief mention.

1897. Woodworth, C. W. Cal. Agr. Exp. Sta., Bui. 116.

"California vine hopper." Detailed description of life history and habits, extent of injury,
remedial measures. Recommends use of sticky fans and nets for catching adults.

1897. Woodworth, C. W. Univ. Cal. Agr. Exp. Sta., App. to A'iticultural Repl.,

1896, p. 219.

Brief mention, use of sticky fans for vine hopper.

1900. Gillette, C. P. Annual Report Colorado Agricultural Exi)erinient Station,

p. 126.

" Important hisects of the year, Leafhoppers( Typhlocyba sj).)." Briefstatement of spring food
plants and breeding habits on grapevines and Virginia creeper.

1901. Felt, E. P. N. Y. State Mus., Bui. 53, pp. 737-738, 838.

" Grapevine leaf-hopper." Brief mention.

19(12. Felt, E. P. U. S. Dept. Agr., Div. Exit., Bid. 37, p. 103.
Brief note.

1903. Twelfth Report Oklahoma Agricultural Experiment Station, 1902-1903, j). 49.

' ' Grapevine leaf-hopper. ' ' Brief mention. Recommends dusting with equal parts of sulphjir
and fresh lime or pyrethrum.

1<)(»4. Slingerland, M. V. Cornell Univ. Exp. Sta., Bui. 215.

" The grape leaf-hopper ( Typhlocyba comes Say)." Full discussion of distribution, injury, life
history, habits, and rernedial measures; many illustrations.

1904. Smith, J. B. Report of the New Jersey Agricultural (College Experiment Sta-

tion, pp. 651-659.

"Rose-leaf tobacco extract." Describes experiment against grape leafhopper on a few vines
with this spray, applying it to underside of grape leaves.

1907. Quaintance, A. L. U. S. Dept. Agr., Planners' Bui. 284, pp. 19-22.
" Grape leaf-hopper." ' Distribution, life history, description, injury, remedies.

1907. QuAYLE, H. J. Cal. Agr. Exp. Sta., Bui. 192, pp. 111-116.

"The vine hopper ( Typhlocyba comes Say)." Injury to grapevines, life history. Remedies:
Hopper cage, spraying.

1908. QiTAYLE, H. J. .Tourn. Econ. Ent., vol. 1, pp. 182-183.

" The California life history of the grape leaf-hopper ( Typhlocyba comes Say)."

1908. QuAYLE, II. .1. Cal. Agr. Exp. Sta., Bui. 198.

"The grape leaf-lioppcr ( Typhlocyba comes Say)." Full discu.ssion of destruction, distribu-
tion, life history, habits, and remedial measures. Many illustrations.

THE GRAPE LEAFHOPPER IN THE LAKE ERIE VALLEY. 47

1910. Hartzeli,, F. Z. N. Y. Agr. Exp. Sta., Geneva, Bui. 3:51, pp. 568-579.

"The grape leaf-hopper ( Typhlocyba comes Say)." Economic importance, injury to grape-
vines. Brief description, seasonal history. Remedy: Black-leaf tobacco extract. Records of
/ineyard experiments.

1911. Johnson, Fred. U. S. Dept. Agr., Bur. Ent., Bui. 97, Pt. I.

"Spraying experiments against the grape leaf-hopper in the Lake Erie Valley." Brief dis-
cussion of life history, habits, and injury to grapevines. Remedies: Tobacco extracts. Record
of spraying experiments in vineyards.

1912. Hartzell, F. Z. N. Y. Agr. Exp. Sta., Geneva, Bui. 344.

"The grape leaf-hopper and its control." Life history, injury to grapevines, species and varie-
ties found in Chautauqua County, food plants, control experiments, aiUomatic spraying attach-
ment, spraying recommendations.

1912. Sanderson, E. D. Insect Pests of Farm, Garden and Orchard, ])]>. 520-523.
New York.

"The grape leaf-hopper ( Typhlocyba comes Say)." Life history, injury, remedies.

1912. O'Kane, W. (\ Injurious Insects, pp. 311-313.

"The grape leaf-hopper ( Typhlocyba comes Say)." Life history, habits, injury to grapevines,
remedies.

1912. Johnson, Fred. U. S. Dept. Agr., Bur. Ent.. Bui. 116, Pt. I.

"Spraying experiments against the grape leafhoppor in the Lake Erie Valley in 1911."
Results of vineyard experiments with tobacco extracts, giving method and cost of appUeation
and results in crop yield.

o

. I «Jf CTS

BULLETIN OF THE

u

No. 45

Contribution from the Bureau of EJitomoIogy, L. O. Howard, Chief
November 22, 1913.

EXPERIMENTS IN THE USE OF SHEEP IN THE ERADICATION
OF THE ROCKY MOUNTAIN SPOTTED FEVER TICK.

By H. P. Wood,
Bureau of Entomology.

PLAN OF EXPERIMENTS.

In order to test the destructive power of sheep against the spotted
fever tick and to ascertain what importance sheep might phiy in the
practical eradication of the tick, some experiments were performed
by the Bureau of Entomology in the Bitter Root Valley in Montana
in June and July, 1913. This work followed the announcement to
the Montana State Board of Entomology, by Dr. L. D. Fricks of the
Public Health Service, of observations on the death of ticks on sheep
wdiich have been published in the Public Health Reports of August
8, 1913.

Two experiments were performed, one with 20 sheep and the other
with 2 sheep. The first experiment, with 20 sheep, wdiich included
1 ram, 11 other adult sheep, and 8 lambs, was performed in country
laiown to be Avell infested with ticks. The country over which the
sheep ranged is adjacent to the foothills and is well supplied with
bushes of various sorts, a growth of small pines, a few fairly large
trees, and several streams of water. There was an abundance of
grass along the streams, but under the pines next to the foothills
there Avas little grass. In the ravine between two hills there was
a thick growth of brush. It is next to the foothills, where brush
abounds, that the ticks were found most abundantly. Very few
ticks were observed along the streams and where the grass was grow-
ing in abundance.

Previous to the time the sheep were driven onto a school section
which was used as an experimental pasture, they had been ranging
away from the foothills and were probably quite free of ticks. No
ticks were seen on cattle and horses running in the range from w^hich
the sheep were taken during the whole tick season, and the animals
were under close observation by the owner. It is fair, then, to sup-
pose that there could have lieen few, if any, ticks on the sheep at the
time they were driven into " ticky " country.
13747°— 13

2 BULLETIN 45, U. S. DEPARTMENT OF AGEICULTUEE.

In the evening of June 3 the sheep were driven onto the school
section into a small corral previously prepared for them. On the
morning- of June 4. and thereafter until the evening of June 14. the
sheep were herded twice a day for about two hours at each feeding.
For the remainder of the time they were kept in the corral. About
three-fourths of the time the sheep Avere herded, they were alloAved
to run at will, and tlie other one-fourth they were driven and made
to feed in places known to be well infested with ticks. During all
this time the development of the ticks was watched on some of the
sheep, and when it was found that some of the ticks were nearly
engorged the sheep were driven to the camp laboratorj^ about a mile
from the slieep corral. At the camp the sheep were examined, usu-
ally twice a day, so that the development of the attached ticks might
be followed, and any females tliat were engorged, or nearly so, were
removed. Here the sheep were allowed their freedom the greater
part of the day, but at night were confined in a shed. It is probable
that they picked up a tick or two about camp, but probably only a
very few.

Two thorough examina Jons were made of each sheep, to locate the
living ticks and to" remove the' dead ones. The first examination be-
gan on June 10 and was finished on June 15; the second was started
on Jtmc 23 u'l ended on June 27. Besides these examinations
numerous \>'^ ^ thorough examinations were made, any dead ticks
found boiDg removed and the living ones noted.

Xear the completion of this experiment two sheep were selected
1 om the adult sheep with heavy wool, and after thorough examina-
I >ns Avere utilized in another experiment. Ticks were collected by
dragging cloths over the ground and placed on these sheep. They
Avere first put on one sheep June 20 and on the other June 25. Until
June 28 these sheep were allowed to run with the others, but after
that time the other sheep Avere driA^en back to the oAvner and the
tAvo Avere taken out to feed. They Avere examined tAvice a day.

OBSERVATIONS AND RESULTS.

In order to show as exactly as possible the results obtained, the 20
sheep have been divided into three groups, namely, unsheared lambs,
unsheared sheep, and sheared sheep. In the first group were 8
spring lambs, Nos. 2-9, inclusiA^e ; in the second group were 7 adult
sheep with heavy wool, Nos. 10-16. inclusive, and in the third group
were the ram and 4 sheared adult sheep, Nos. 1 and 17-20. inclusiA^e.

The results have been summarized in Table I. The heading, " total
dead unfed ticks " includes all males and females which were thought
to have been killed before having fed to an}^ extent. It may also
include, besides males which had not fed to any extent, males which
had fed considerably, for it is usually impassible to distinguish fed

ERADICATION OF THE EOCKY MOUNTAIN SPOTTED FEVER TICK. 3

males from unfed males when they are dead. The headings under
" location of dead ticks on host's body " are self-explanatory. The
ticks taken from the head were usually in the wool on the top of the
head. The same statement also applies to the neck. The heading,
" total ticks found attached at first examination," is also self-explana-
tory. Only a few ticks were on the sheep at this examination. It
is likely that there were only a few ticks which had attached them-
selves and become detached before this examination, except those
which were found dead in the wool. The headings under "location
of living attached ticks " neecl some explanation. The " other place •'
referred to in the case of No. 1 was near the base of the right fore leg,
and in the case of No. 7 the tick was attached on the breast. Ticks
attached on the head were in all cases found attached in the wool.
No preference was shown by the ticks on sheep with heavj'^ wool for
j3laces where the wool was short. They attached both in short wool
and in long wool which was somewhat open. On the ram the ticks
attached in a bunch in the cavity where the horn ordinarily is located
(this ram was hornless).

All the ticks attached on sheared sheep, except one, were in front of
the ears where the wool was thin ; the exception w^as in the case of
one tick which was attached on the shoulders.

BULLETIN 45, U. S. DEPARTMENT OF AGRICULTURE.

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ERADICATION OF THE ROCKY MOUNTAIN SPOTTED FEVER TICK. 5

On the lambs, ticks were found attached in several different places:
Some were in front of the ears, some in the avogI on top of the neck,
others in the wool on the top and sides of the shoulders, and one was
attached, as stated before, on the chest. In no case were the ticks on
lambs found attached on the hind quarters or beneath the body.

The ticks referred to as crawling were no doubt those males and
females which had recently gotten on the sheep, or perhaps they were
males seeking females. Besides the females referred to in Table I as
" engorged one-half or more," there were some other females which
had fed slightly but had never become as much as one-half engorged.
This division at one-half engorged is made because females less than
about that size seldom lay eggs. Should ticks less than one-half full
get rubbed off, it is extremely doubtful if they would ever deposit
eggs. Just how many ticks were rubbed off or killed before complete
engorgement it is impossible to say, but a few cases of this kind were
observed. In all cases in which females are referred to " with males
beneath," such pairs were in the correct position to effect fertilization.
The " engorged females recovered from sheep," except one, were
picked from the host when they had reached full or nearly full
engorgement.

It seems probable that the dead unfed ticks found in the wool were
for the most part killed by the lanolin, although the heat of the wool
may have been a factor. It was found in a number of cases that ticks
died after attaching. This factor was indicated by a reddish spot on
the skin near the place where the tick was found dead. The ticks,
however, were usually found loose in the wool. Both living (at-
tached) and dead ticks were found at times in the same fold.

To show the location of the ticks recovered and the relation between
shearing and the development of the ticks, certain data in Table I
have been rearranged in Tables II and III.

Table II. — Location of ticks recovered from sheet).

Dead.

Alive.

Head

31
28
30
23
3

45

Neck

29

Upper parts

15

Sides

0

Underneath 1

23

I On the shoulder. 2 Two on leg.

Table III. — Relation between shearing and attaehment of ticks.

Lambs not sheared

Sheep not sheared

Sheep sheared (including ram)

Engorged
feraales.

6 BULLETIN 45, V. S. DEPARTMENT OF AGRICULTURE.

The data appertaining to sheep numbered 3, 8, and 11 have been
omitted from the tables because these individuals were dipped on
June 13.

Special observations were made on sheep No. 10. On June 20,

0 females and 3 males, collected by dragging, were scattered on the
back, neck, and head of this sheep. Most of the ticks went beneath
the wool immediately near where they were dropped. On the fore-
noon of June 21 a male and a female were found dead in the wool,
the female on the head and the male on the side. A female, nearly
dead, was also found in the wool on top of the head. The live ticks
attached were a male and a female on top of the head at a place
where the wool was very short. Six males and 12 females, collected
by dragging, were now scattered on the head, neck, and back. In
addition 1 female (one-twelfth engorged) which w^as picked from
a saddle horse was placed on the back of the sheep at the edge
of a spot where the wool had been worn short. In the afternoon
3 males were found dead in the wool on the back. These had never
attached. The one-twelfth engorged female was found dead and
shriveled about 8 inches from where it was placed, in heavy wool.
Eight males and 5 females, collected by dragging, were scattered on
back, neck, and head. On the morning of June 22, 3 males and 1
female were found dead in the wool. Two males were taken on the
shoulder and the other 2 ticks were taken from the head. None had
attached. The live ticks found attached at this time were 4 females
and 3 males, between the folds of heavy wool. Two of the dead ticks
that were removed were taken from a fold where 2 females and 1
male had attached. The attached ticks were scattered as follows:
2 females and 1 male in a fold near each other ; 1 male and 1 female
near each other in another place ; and 1 male and 1 female, each alone,
at still other places. All were in long wool. A male, barely alive, was
crawling at the edge of the short wool spot mentioned before. On
the forenoon of June 23, 2 females and 1 male previously found at-
tached were dead. These ticks were still attached when found. Two
dead males and 3 dead females were also found. These had never
attached. They were picked, 2 from the back, 2 from the head, and

1 from the neck. One of those on the back was a tick spoken of
before as barely alive. At this time 1 female was found slightly en-
Cforo-ed. A male was seen to be attached on the neck. A female loose
in the wool appeared entangled. In the afternoon of this day 4
females and 1 male, collected by dragging, were put on the head,
neck, and back of the sheep, as was also a male which had fed. All
ticks went quickly under the surface of the wool. On the morning
of June 24 the female that appeared entangled in the wool was dead.
Three males and a female were picked from the wool, dead. These
had never attached. Two females and 1 male were attached. The

ERADICATION OF THE ROCKY MOUNTAIN SPOTTED FEVER TICK. 7

2 females were ticks put on the day before. The male was attached
before. Two females, 1 on the head and 1 on the back, were barely
alive. On June 25, 2 dead females were picked from the avooI on
the head. They had never attached. One dead female was picked
from the wool on the back. This tick was spoken of as barely alive.
There were 3 females attached in long wool, 1 of Avhich was en-
gorged a little.

The following notes show the progress of the experiment:

June 27, a. m. : The 3 females are engorging to some extent. A male is un-
der the largest of the three.

June 28 : One of females on the head, which had begun to engorge, is now
dead. This female was probably killed by the host. There are 3 females at-
tached and feeding on the head. The largest is one-twentieth engoi'ged.

June 29, a. m. : One dead male was taken from tiie neck and a dead female
from the shoulder. The female had been attached. The one-twentieth engorged
female is now missing.

June 30, a. m. : Two males and 2 females are attached on the head. Both
females are feeding.

June 30. m. : One female, collected by dragging, was put on head.

July 1. a. m. : One female was picked from shoulder, which had never at-
tached. The 2 males and 2 females are still attached as before. One female,
collected by dragging, was put on the head. This female attached near one of
the other females.

July 2 : The female put on yesterday is attached as well as the other females.
Two females are now one-twelfth engorged. The two males are attached as
before.

July 3, a. m. : Three females and 2 males are now attached. The female put
on sheep July 1 has moved one-half inch from its former place. Two females
are about one-tenth engorged.

July 3, p. m. : One of the females that had become one-tenth full is now miss-
ing. The other is one-seventh engorged. Only 1 male was noticed attached.

July 5. a. m. : The female that was spoken of as one-seventh full is now full
or nearly so and has a male beneath. This is the first time that a male has been
seen near this female. The engorged female was picked.

July 6 : One dead unfed female was picked from back. One male and 1
female are now attached.

July 7, a. m. : The male that was seen under the engorged female is now dead.
It is crushed as though by the host. The female put on July 1 is now one-
fifteenth engorged.

July 7, p. m. : A thorough examination was made at this time. Two dead
females (unfed) and a dead male were picked from the back and sides of the
sheep. The attached female is one-twelfth full.

July 8: The attached female is about one-sixth full. No males are near.

July 9 : The attached female is about one-fifth full. No males are near.

July 10: The attached female is about one-fourth full. No males are near.

July 11 : The attached female is about one-fourth full. No males are near.

July 12: The female is not attached, but is loose in the wool near its former
place of attachment. It has begiui to shrivel.

July 13 : The female is dead in the wool at same place. It is shriveled and
discolored.

8 BULLETIN 45, U. S. DEPARTMENT OF AGRICULTURE.

The following notes record the observations on sheep No. 11 :

June 23. The sheep thoroughly examined and no ticks found.

June 25, a ni. : Four males and 11 females, collected by dragging, were put
on the head, neck, and shoulders of the sheep. A male and a female of the
foregoing were put in a fold close to the skin. The ticks put on the surface
wete out of sight in a few minutes.

June 25, p. m. : A dead male and a dead feanale were picked from the wool.
The male had his head near the skin but had apparently never attached. Two
females and one male were alive loose in the wool. The female that was placed
in wool next to the skin is attached. The male is not where it was placed.

June 26. a. m. : A male and a female were picked from the head, both dead.
These ticks had been attached. The female that attached in the fold where it
was put is no longer there. No ticks are now attached.

June 27: Two females, collected by dragging, were put on the base of the
sheep's ear; also 1 female (one-fourtJi engorged), picked from saddle horse,
was put on the sheep's back. One dead unfed female was picked from the side.
The tick had never attached.

June 28, p. m. : Two i)artly fed males were put on the head of the sheep.
One of the 2 females i)ut on the ear was found dead at the base of the ear.
It had never attached. One female was loose on the head, crawling. The one-
fourth engorged female was still alive, but has not attached.

June 29 : Two males and an unfed female found dead in wool on the head.
The partly fed female is now dead.

June 30, a. m. : One dead male was picked from wool on the head.

July 1 : One fejnale about one-twelfth engorged was picketl from a saddle
horse and placed in wool on the sheep's head next to the skin.

July 2 : The partly engorged female is now dead.

July 9 : No ticks were found after a thorough examination.

Table IV gives a summary of the experiments with sheep Nos. 10
and 11.

Table IV. — Summary of experiments ivith individual sheep.

Details.

Total number ticks put on sheep

Total dead unfed ticlis vvliich never attached

Total ticks which attached but died quickly

Total ticks which fed some but died or were killed before attain

ing any size

Partly engorged females which died quickly when put on sheep.

Total dead ticks recovered

Dead unfed ticks:

From head

From neck

From back

From side

Total ticks known to ha ve attached

Total female seen with males beneath

Total engorged females recovered

Sheep No. 10.

Male Female
ticks. ticks.

Sheep No. 11.

Male

ticks.

Female.

ticks.

It is a fact generally recognized that animals in confinement will
fight ticks more than animals running free. This fact will probably
account for the small number of ticks which were successful in en-

ERADICATION OF THE EOCKY MOUNTAIN SPOTTED FEVER TICK. 9

goi^ging. The last female on sheep No. 10 would probably have
become engorged had it been fertilized, for fertilized females engorge
rapidly, whereas with infertile females engorgement is slow.

THE APPLICATION OF THE INFORMATION OBTAINED TO PRACTICAL

ERADICATION.

The main point to be considered in the last experiment is the fact
that of 33 females put on sheep No. 10, only 1 fed sufficiently to lay
eggs. There were in nil, however, 6 females which stood a fair
chance of engorging, so that it is difficult to say what percentage of
females that get on a sheep in nature will enggrge to repletion. If
we assume that G females would have fed to repletion in nature, we
find that 5.5 per cent of those females which got on the sheep became
engorged. In the experiment with 2 sheep, at the end of 6 days these
animals had picked up at least 19 females, of which 13 females at-
tached. At the same rate in 30 days sheep No. 10 would have had at-
tached 80 females and would have picked up 94 females. If we take
5.5 per cent of 94 we have 5.17 females which would engorge to reple-
tion in a month. We would have to assume this many to be the maxi-
mum for the sheep with heawv^ wool in the experiment. The mini-
mum would be 0, since there were 2 sheep which had no females at-
tached at the examination. It would be impossible to strike <in aver-
age, but let us assume that each sheep would breed, on an average, 2
ticks per month. We would then have, for a her(J of 1.000 sheep,
2,000 ticks per month during the tick season. Each female means
about 4,000 larvae. This would make 8,000.000 larvae, which is a
rather large number, though it is of course impossible to estimate
what percentage of these would ever reach maturity. It might, how-
ever, be possible to eliminate the sheep which are likely to breed the
majority of the ticks. Could this be done, it would be possible to
use sheep in the destruction of ticks without dipping them. Until
that fact is demonstrated, hoAvever, it would seem necessary to dip
sheep along with other live stock in case they were allowed to run in
" ticky " country. Even if it were not necessary to dip sheep with heavy
wool, it would certainly be necessary to dip lambs or sheared sheep.
A mere glance at the table will show that lambs or sh'eared sheep will
breed a considerable number of ticks and kill but few. The only pos-
sibility, therefore, of employing sheep in the work of tick eradication
would be the using of wethers of other sheep with heavy wool. It
does not appear practicable to attempt to use wethers alone, under
any circumstances, as a means of ridding the Bitter Root Valley of
spotted fever ticks. Nevertheless it would appear to be possible to
use sheep as one means of reducing the numbers of the ticks, although
in this connection several considerations must be mentioned.

10 BULLETIN 45, U. S. DEPARTMENT OF AGRICULTURE.

There would be some very serious objections to using sheep ex-
clusively in the destruction of ticks, even though the}^ should be found
to kill practicall}'' all the ticks which get on them. In the first place,
it wOuld be necessary to eliminate all live stock except this on which
the ticks could be destroyed at weekly intervals by dipping or other-
wise. Secondly, it is impracticable to stock heavily a given area with
sheep and attempt to carry the usual number of other live stock on
the same pastures. It would thus be necessary to reduce greatly the
number of live stock other than sheep in order to graze a sufficient
number of sheep to have any appreciable value as collectors of ticks.
Moreover, it would be necessary to cut down all vegetation higher
than a sheep's back, for there are many ticks that await a host higher
than 2 feet from the ground. It would also be necessar}^ to drive the
sheep where the ticks were know^n to be located, for the sheep nat-
urally go where the feed is best. In the locality where the experi-
ment with 20 sheep was carried on it was found that there were few
ticks where the feed was abundant, but many next to the foothills
and in the ravines where the feed was scarce. The character of the
country on the western side of the valley in many places is also such
that it would not admit of herding sheep. Should sheep run con-
tinuously in the wooded and brushy country on the western side of
the valley they would wear off the wool, which would make them
increasingly more susceptible to tick attack and less profitable to the
owners.

The tendency of the tick to attach in bunches would indicate that
in case ticks obtained a start on any animal they would breed on that
animal with increasing facility ; for it would be more easy, as the fe-
males enlarged, for the males to find them. Since most of the en-
gorged females picked from the sheep in the experiment had males
beneath them, and all of the females which were removed when well
engorged deposited eggs which hatched normally, there* appears to be
little likelihood that there would be man}- females to drop which
would not be fertile.

The possibility that sheep may serve as a reservoir for the virus of
spotted fever is a point that should be tested before sheep are used
at all in the destruction of ticks.

It appears, however, that sheep are very good collectors of ticks.
Six sheep with heavy wool picked up in 11 days about 72 females
and 47 males. Although no comparative experiment has been per-
formed, it is the writer's opinion that G horses or 6 cattle under the
same conditions would not have picked up and retained nearly that
number. Therefore in " ticky " country which is favorable to the
herding of shee]) it would be advantageous to use sheep as collectors
of ticks. By dipping the sheep once in 7 days it would seem that
much good could be accomplished. To bring about the greatest good

ERADICATION OF THE EOCKY MOUNTAIN SPOTTED FEVER TICK. 11

it would be necessary to herd the sheep with a knowledge of the loca-
tion of the ticks. It is extremely doubtful if sheep would be of much
importance as collectors of ticks if they were allowed to run free.

The several limitations to the practicability of using sheep in the
eradication of the spotted fever ticks that have been mentioned em-
phasize the great importance of following the plan of dipping do-
mestic animals which is successfully under way. Sheej^ may be used
under some conditions in the work, but the main reliance must be
upon the dipping of horses and cattJe. The extent to which sheep
may be used will depend upon future experiments and observations.

o

VVASHIXGTOX : COVKRN'MKNT TRIXTINd OFFICE : 1913

BULLETIN OF THE

u

No. 59

Contribution from the Bureau of Entomology, L. O. Howard, Cliief
January 19, 1914.

(PROFESSIONAL PAPER.)

THE TOBACCO SPLITWORM.

By A. C. Morgan and S. E. Crumb,
Of Southern Field Crop Insect Investigations.

INTRODUCTION.

The folloA^dng account of the tobacco splitworm (Pliihorimaea
operculella Zeller), although not complete, contains data not hereto-
fore pubHshod. The life history notes, description of stages, etc.,
were made by the junior writer. Credit is due the senior writer
for the observations made in Florida and for the recommendations
under the heading: ''Remedial measures."

In California this insect is a serious potato pest, and Dr. F. H.
Chittenden ^ reports that in 1912 two growers at El Monte, Cal.,
lost $90,000 and S70,000, respectively, on the crop of that year.
Although quite generally distributed over the Southern States, this
insect has caused serious loss to tobacco growers in only one locahty,
viz., Dade City, Fla. The injury at that place was severe in 1906,
more severe in 1907, and culminated in 1908 in a conservatively
estimated loss of $150 per acre — a loss totaling $12,000 for the 80
acres of shade-grown tobacco. The injury since 1908 has been very
light, due in part to the early planting and in part to the very careful
and very thorough remedial measures employed.

The variation in food habits, which is noted later, had created the
suspicion that the form working upon potatoes might be specifically
distinct from the one attacking tobacco. During the summer of 1913
experiments were conducted to determine this point.

EXPERIMENTS ON THE SPECIFIC STATUS OF THE TWO FORMS.

The potato-tuber moths used in these experiments were of the
habitual potato-feeding type from Whittier, Cal., kindly furnished
by Mr. J. E. Graf. The splitworm moths were of the habitual
tobacco-feeding type from Florida, North Carolina, and Virginia.

' Chittenden, F. H., 1912. The potato-tuber moth. A preliminary accoimt. {Phthorimaea operculella

Zell.). U. S. Dept. Agr., Bur. Ent., Circ. 162, p. 2. Chittenden, F. H., 1913. The potato-tuber moth.
U. S. Dept. Agr., Farmers' Bui. 557, p. 2.

19794°— 14 1

2 BULLETIN 59, U. S. DEPAETMENT OF AGEICULTUEE.

LarvsB of the potato-tuber moth were reared on potato tubers
and on the foliage of Solanum carolinense, eggplant, Physalis sp.,
Datura stramonium C'jimsonweed"), and tobacco; they also mined
the leaves of Solanum nigrum until the plant died. Larvae of the
tobacco splitworm moth were reared on potato tubers and on the
foliage of Solanum carolinense, eggplant, Physalis sp., Physalodes
physalodes, Datura stramonium, and tobacco. There was no per-
ceptible difference in the period of development, in habits, or in
behavior of the two forms on a given food plant that could be ascribed
to the different origins of the individuals. A male potato-tuber
moth of the habitual potato-feeding type and a female splitworm
moth of the habitual tobacco-feeding type, reared from isolated
pupae and caged together, produced larvae that reached matu ity
upon tobacco.

The earliest stages of the two types show no appreciable differences
except in the case of the larva, and here the differences, excepting
size, are entirely colorational. The larva on potato is larger, grayish,
and has the mesothorax and metathorax pinkish, while the habitual
tobacco feeder is green and has the mesothorax and metathorax deep
maroon. By reversing the two food plants the larvae can be made to
approach each other in coloration, but even after two generations on
tobacco the habitual potato feeder is less green and has the thorax
distinctly paler than the habitual tobacco feeder; also, the coloration
of the latter type persists when reared upon potato tubers. The
larvae of the crossed moths were intermediate in coloration between
the two t3rpes just discussed.

The rather persistent color variation noted in the two larval types
under discussion, while probably of sufficient constancy to warrant
a varietal separation, is not, the writers beheve, of sufficient mipor-
tance to justify a specific separation.

Potato-tuber moths reared from potato are usually somewhat
larger than splitworm moths reared from tobacco. This difference
disappears when the potato-tuber moth is reared on other plants.
Potato-tuber moths reared from potato tubers, Physalis sp., Solanum
carolinense, tobacco, and Datura stramonium, and splitworm moths
reared from tobacco, potato tubers, and Physalis sp., were submitted
to Mr. August Busck, who reported that he could find no specific
differences.

DISTRIBUTION.

In the United States the species occurs in California and southward
from a Hue connectmg the District of Columbia and Colorado. The
definite localities include Tennessee, Virginia, North Carolina, South
Carolina, Florida, and Texas. Reports of more northern occurrence
are probably due to the shipment of mfested potatoes into these

THE TOBACCO SPLIT WORM. 3

localities. The known range also includes Cuba, Costa Rica, Peru,
Hawaii, Australia, Tasmania, New Zealand, Sumatra, Transvaal,
Algeria, and southern Europe.

COMMON NAMES.

Phthorimaea operculella when working upon tobacco is known as
the tobacco splitworm and the tobacco leaf -miner; when working
upon potatoes it is known as the potato-tuber moth and the potato
moth.

FOOD PLANTS.

The known food plants of Phthorimaea operculella include Solanum
torvum, S. verhascifolium, S. carolinense, S. nigrumCI), eggplant,
potato, tomato, PJiysalis peruviana, Physalis sp., Physalodes physa-
lodcs, Datura stramonium, and tobacco.

FOOD HABITS.

The larva occurs as a borer and also as a leaf-miner. The former
is probably the original habit, examples of which have been ob-
served by Quaintance in the fruit of eggplant, by Kotinsky in toma-
toes, and by C. W. Howard and Oliff iii the stems of tobacco. Dr.
L. R. De Bussy considers this the more common form of injury to
tobacco in Sumatra, where the larva forms a gall in the stem. C. W.
Howard reports a similar habit of the larva in the Transvaal.^

In Cuba and the United States the insect is known on tobacco as
a leaf-miner only. A boring tendency is still apparent, however, as
noted by Houser, in that the larva usually tunnels the midrib or a
vein in addition to mining the membrane of the leaf. In about 50
mines examined by us the larva had also tunneled the midrib or a
vein in almost every case.

Only the older tobacco leaves are affected, unless the infestation
is very severe; and in these, the lower leaves, grayish, irregular
blotches are produced, which later turn brown and become fragile,
so that the tobacco is unfit for wrappers. At ClarksviUe, Tenn.,
where the infestation is very slight, the larva in most cases begins
work in the ''ruffles" along the midrib and may afterward migrate
and form mines in various parts of the leaf.

In forming its mine the larva begins by spinning a tent of silk
between the midrib, or between the vein and the surface of the leaf.
Under this protection it soon forms a shelter between the leaf sur-
faces by consuming the parenchyma. The mined leaf becomes
more or less distorted, and this is especially noticeable on leaves,

1 Gnorimoschema heliopa Low causes similar injury to tobacco in India, Ceylon, and Java.

4 BULLETIN 59, U. S. DEPARTMENT OF AGRICULTURE.

such as those of Solanum carolinense, which the larva is more cap-
able of manipulating, but there is no tendency to form a firm, cylin-
drical, silk-hned tube, as is the case with the blue or bluish-green
larva of Phthorimaea glochinella Zell., which feeds upon some of the
same plants as does Phthorimaea operculeUa.

DESCRIPTION OF STAGES.

THE EGG.

The egg is pale, translucent, yellowish gray, and strongly irides-
cent; it is oval, 0.45 mm. long, 0.35 mm. broad at the middle, mem-
branous, and without apparent sculpture. The side upon which it
is deposited is sUghtly flattened.

THE LARVA.

The full-grown larva is 7 to 14 mm. long. The head shield is
0.80 to 0.86 mm. broad and fuscous brown. The cervical shield is
darker brownish fuscous, with a pale mid-dorsal line, shining, the
posterior margin medially straight. The anal shield is brown. The
mesothorax and metathorax are deep maroon. The body varies
m color through green and gray and is overlaid dorsally with purplish
as the larva nears pupation. It is slender, tapering from the meso-
thorax posteriorly and set closely and uniformly with minute gran-
ules each bearing a minute point, the granules of the thorax and the
Jast abdominal segment being the larger. The tubercles and their
setae are inconspicuous, brownish; tubercle II is slightly larger than I.
The legs are deep fuscous; the prolegs, green.

The larva which has just emerged is light grayish, with strongly
contrasting dark head and cervical shield.

Larvae which have been reared habitually upon potatoes are of
a larger average size than those reared upon tobacco, and the maxi-
mums of the foregoing measurements are from potato-feeding larvae.
The larva on potato is more grayish on the body than the tobacco
miner and has the mesothorax and metathorax pinkish instead of
deep maroon.

THE PUPA.

The pupa is yellowish brown, 5.5 to 7 mm. long and 1.5 to 2 mm.
broad; it is broadest tlu-ough the metathorax, tapering both ante-
riorly and posteriorly. The head is rather distinct and slightly nod-
ding. The abdomen, excepting the last three segments, is set with
very minute spinules; it bears at the tip mid-dorsally a short, curved,
erect, pointed horn flanked by about four pairs of long hooked*
spinules, and ventrally a pair of blunt, rounded lobes beneath which
are about four pairs of long hooked spinules. Each abdominal seg-
ment is set with a transverse row of spinules near the anterior margin.

THE TOBACCO SPLITWORM. O

As in the case of the larvae, the pupae of the habitual potato
feeder are larger than those from the habitual tobacco feeder and the
maximum measurements in the foregoing description are from
potato-reared pupae.

The adult is a slender, inconspicuous moth with dark grayish wings

bearing indefinite yellowish streaks and having an expanse of about

20 mm.

LIFE HISTORY.

At Clarksvillo, Tenn., the sphtworm requires 25 to 30 days in sum-
mer for completing its development from egg to adult. Of this time 4
days are spent in the egg stage, 15 to 17 days in the larval stage, and
6 to 9 days in the pupal stage. The length of these stages is consid-
erably affected by temperature, as is indicated in detail in the accom-
panying tables. By reference to Table III we see that at an average
mean temperature of about 81° to 82° F. the minmium pupal period
is^ obtained, and that when the average mean temperature falls below
about 68° to 70° F. the pupal period is very greatly lengthened.

Eggs are deposited singly upon the foliage of the host plant.
Moths begin to oviposit two or thi'ee days after emergence and con-
tmue ovipositing for several nights. The largest number of eggs
obtained from a single moth was 46, but this probably does not
represent the maximum oviposition under normal conditions.

The larva is very active, is capable of prolonged exertion imme-
diately after hatching, and clings very tenaciously to the foliage.
The frass is either stored in a particular part of the mine or is cast
outside whore, in the case of those working upon potato tubers, it
forms masses held together by silk. The larva pupates in a slight but
somewhat tough cocoon of silk and debris among clods or rubbish at
or near the surface of the soil.

Table I. — Length of egg stage of tobacco splitivorm.

Average

Eggs deposited

Eggs hatched

Egg

mean

night of—

night of—

stage.

tempera-,
ture.

Days.

o p

June 15,1910

June 19,1910

4

77.3

June 17,1910

June 21,1910

4

79.5

June 22,1910

June 27,1910

5

80.5

Julv 3, 1913

July 7, 1913

4

82

July 3, 1913

July 7, 1913

4

82

July 4, 1913

July 8, 1913

4

80.9

Julv 5, 1913

July 9, 1913

4

79.7

Aug. 5,1913

Aug. 8, 1913

3

88.6

Aug. 6,1913

lAug. 10,1913

3i

88

Aug. 21,1913

Aug. 25,1913

4

72.6

Sept. 11,1913

Sept. 15,1913

4

81.9

Sept. 12,1913

Sept. 16,1913

4

82.4

* Forenoon.

BULLETIN 59, U. S. DEPARTMENT OF AGRICULTURE.
Table II. — Length of larval stage of tobacco splitworm.

Eps; hatrhed
night of—

Larva pu-
pated night
of—

Larval
stage.

Average
mean

tempera-
ture.

Food
plant.

June 21,1910
July 9,1913
Aug. 25,1913
.\ug. 25,1913
Sept. 27,1911

Julv 6, 1910
Julv 25,1913
Sept. 10,1913
Sept. 11,1913
Nov. 3,1913

Days.
15
16
16
17
37

- F.

78.7
81.1
81.2
81.1
64.4

Tobacco.
Do.
Do.
Do.
Do.

The lengths of the larval stage given abo^e are corroborated by
about 25 records giving the combined length of the larval and pupal
stages.

T.\BLE III. — Length of pupal staoe of the tobacco splitworm.

Number
of indi-
viduals.

Larva pupated
night of —

Apr. 21,1909
May 22,1910
July 6,1910
July 25,1913
Aug. 19,1913

do

do

Aug. 21,1913
Aug. 27,1911
Aug. 31,1913

do

do

Sept. 1, 1913

do

Sept. 2,1913
Sept. 3,1913

do2

do

Sept. 10, 1913

do

Sept. 11,1913
Sept. 13,1913
Sept. 27, 1913
Sept. 30, 1913
Oct. 1, 1913

Moth emerged
night of —

May 14,
June 5,
July 14,
Aug. 1,
Aug. 28,

do...

Aug. 29,
Aug. 30.
Sept. 8,
Sept. 6,

do3.

do4.

Sept. 7,
Sept. 8,
Sept. 9,

do...

do...

Sept. 10,
Sept. 23,
Sept. 24,
Sept. 27,
Sept. 29,
Oct. 9,
Oct. 15,
do<.

1909
1910
1910
1913
1913

1913
1913 3
1911
1913

1913
1913
1913

1913
1913
1913
1913
1913
1913
1913 <

Average

Pupal

mean

stage.

tempera-

ture.

Days.

'F.

23

65.1

14

67-

8

83.3

7

85.1

9

77.1

9

77.1

10

77.5

8.5

76.4

12

76.8

6

83.7

5.5

83.7

6-

83.7

6

83.7

7

83.2

7

81.8

6

81.4

7

81.4

7

81

13

69

14

69.1

16

68-

16

67.6

12

70.4

15

68.3

14

68.3

Food plant of
larva.

Tobacco.
Do.
Do.

Potato.
"Jimsonweed.
Potato.
Tobacco.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.

Do.
Potato.

Do.
Tobacco.

Do.

Do.
Physalis.

1 Reared from moths of the habitual potato-feeding type. 'Forenoon. ' 2 p. m. < Afternoon.

SEASONAL HISTORY.

Full-grown larvae have been i eceived from Florida in late April, indi-
cating that oviposition may begin in that region as early as March.
Larvae have not been found at Clarksville, Tenn., earlier than June 3,
and moths have emerged in numbers as late as the middle of No-
vember. It seems probable that at least six generations are produced
in Florida and that about three or four are produced at Clarksville,
Tenn. Moths emerged in five cages at Clarksville November 14,
1913, and were still active December 15, 1913, upon which date
about an equal number of cages still contained pup». These records
seem to indicate that the winter is passed in both the pupal and
adult stages. No larvae, so far as known, have entered hibernation
successfully.

THE TOBACCO SPLITWOEM.

PARASITES.

Kotinsky* records two larval parasites, ClieJonus hlaclchumi Cam.
and Limnerium polymesiale Cam. About 25 per cent of the full-grown
larvae of a large shipment of splitworms, sent by Mr. G. A. Runner late
in August, 1913, from Kinston, N. C, were parasitized. Several
parasitic larvae emerged from each splitworm which was killed at or
just before the emergence of the parasite, and while still in the mine.
The parasites spun their cocoons in the mine and sometimes within the
larval skin. A single splitworm from which this parasite was reared
was included in another large shipment of material sent by Mr. Runner
from Appomattox, Va. Larvae of this parasite which emerged from
the host September 1, 1913, pupated September 3, and the adults
emerged September 10, giving a pupal stage of seven days.

REMEDIAL MEASURES.

Quaintance ' recommends the destruction of the larvae hi the mines
by pinching, and the destruction of all trash in and around tobacco
fields and tobacco barns. Both of these recommendations should be
followed. However, in severe infestations it may be necessary to
prime off and destroy the leaves infested by the earlier generations.
A heavy infestation would ruin the leaves for wrappers, in which case
the priming and destruction of the leaves will be a cheaper and more
thorough method of destruction, for it will cause the death not only of
the larvae but also of a large number of eggs. This plan was pursued at
Dade City, Fla., following the severe infestation of 1908, and with
excellent results. Since that year, also, the crop has been transplanted
much earlier than was the custom previously, and was matured before
the appearance of the most destructive generation of the splitworm.
Loss has been very light since 1908.

To summarize the remedial recommendations: (1) Transplant the
crop as early as possible, in order to mature it before the appearance of
the most destructive generation of the splitworm; (2) when the early
infestation is very severe, prime off and destroy the infested leaves;
(3) destroy all tobacco stubble as soon as the crop is harvested to pre-
vent the breeding of a hibernating generation; (4) clean up and de-
stroy all trash in and around tobacco fields and tobacco barns; (5) do
not follow potatoes by tobacco, for the infestation of tobacco has been
more severe in such cases than where a different rotation was followed ;
(6) grow potatoes as far as possible from tobacco fields.

1 Kotinsky, Jacob, 1906. Hawaii. Forester and Agr., v. 3, no. 7, p. 200-201.

2 Quaintance, A. L., 1898. The tobacco leaf-miner {Gelechia picipellis Zett.). Fla. Agr. Exp. Sta., Bui 4i<,
p. 178-181.

o

DIv . LNfc>C>v^Ao.

BULLETIN OF THE

u

No. 78

Contribution from the Bureau of Entomology, L. O. Howard, Chief.
May 18. 1914.

(PROFESSIONAL PAPER.)

THE SO-CALLED TOBACCO WIREWORM IN
VIRGINIA.

By G. A. Runner,

Entomological Assistant, Southern Field Crop Insect Investigations.

INTRODUCTION.

For the study of insects injurious to tobacco the Bureau of Ento-
mology during the last four summers has mamtained a temporary
field station at Appomattox, Va. Work of this station has been
under the direction of Mr. W. D. Hunter, in Charge of Southern
Field Crop Insect Investigations, and more immediately under the
supervision of Mr. A. C. Morgan. Laboratory quarters were fur-
nished by the Tenth Congressional District Agricultural School.
The results of investigations of the tobacco Crambus (Cram.bus cali-
ginosellus Clem.) are given in this bulletin.

The work in Virginia was in cooperation with the State experiment
station and the Bureau of Plant Industry of the U. S. Department
of Agriculture. Through an agreement with the cooperators, the
Bureau of Entomology was furnished all data pertaining to the rota-
tion of crops grown in connection with tobacco, and the plats of the
several tobacco stations in the State were placed at the disposal of
the agent in charge, for inspection and experiment. The records
of these stations, extending over a series of years, are of great value
in determining the crop rotations and cultural methods of control
best adapted to the special conditions to be dealt with in different
tobacco sections.

The experimental work with tobacco in Appomattox County, Va.,
was begun by the Bureau of Soils in 1904. The work has since been
conducted cooperatively by the Bureau of Plant Industry and the
Virginia experiment station. Since the first, owing to the work of

' Throughout the tobacco-growing sections of Maryland, North Carolina, and Virginia the larvae of the
tobacco Crambus are generally knowTi as " wireworms." They are also knowTa in other sections as "tobacco
wireworms," "budworms," "com worms," "stalk worms," "heart worms," "cutworms," "stem worms,"
"root webworms," and "screw worms." In parts of Tennessee and Kentucky the larvte are commonly
called "screw worms." The term "wireworm" is also applied, as in other sections, to the true wire-
worms (larvffi of Elateridsp), which the Crambus larvfr in no way resemble.

Note.— This bulletin is descriptive of an insect enemy of tobacco and corn. Of especial interest in
the eastern tobacco and corn districts.

30183°— Bull. 78-14 1

2 BULLETIN 78, V. S. DEPARTMENT OF AGRICULTURE.

the tobacco Crambus, great difficult}'- has been encountered, in
many of the experiments, in getting the perfect stand of plants so
essential for comparative tests. This led to a study of the life his-
tory of the insect and of the somewhat extensive cultural experi-
ments by the Bureau of Entomology aimed at its control. The
effect of certain crop rotations in reducing injury from the tobacco
Crambus was noticed during the early progress of the cultural in-
vestigations by Mr. E. H. Mathewson, Crop Technologist of the
Bureau of Plant Industry, to whom the writer is indebted for sug-
gestions concerning the cultural methods of control undertaken by
the Bureau of Entomology.

GENERAL HABITS AND ECONOMIC IMPORTANCE OF THE GROUP
TO WHICH THE TOBACCO CRAMBUS BELONGS.

The larvfe of insects included in the faixdly Crambidfp, to which
the tobacco Crambus belongs, feed mainly on the grasses (Graminese),
although some of them subsist on plants of other families. Many
construct tubular, web-lined galleries near the roots of the plants on
which they feed, and some bore or tunnel into the roots or stems; for
this reason they have been named "root webworms." The moths, or
adults, are inedium or rather small in size, wdth brown, yellow, or
white colors prevailing. Many species have metalhc markings on
the forewings, which are comparatively long and usually narrow.
When at rest the forewings are rolled around the body and conceal
the hind wings, which are folded beneath. This gives the body the
appearance of a tiny cylinder, and accounts for the term "close-
wings." The species are widely distributed over the globe, but are
apparently most numerous in temperate climates. In North America
comparatively few are known, and the majority of these belong to
the genus Crambus, in wliich Dr. H. G. Dyar' catalogues 60 species.

Moths of the genus Crambus fly mostly on dark afternoons and
during the early part of the night. They are more common in open
fields. When disturbed they make short erratic flights, rarely
flying more than a few rods at a time. They usually alight head
downward on the stems of plants, and their color often harmonizes
so perfectly with their surroundings that they can with difficulty be
seen. Most of the species are single-brooded; but as the moths of
different species emerge successively thi'oughout the season, one or
more of- the latter are present in most locahties from spring until
late fall. Though various species of Crambus are common in most
localities, they seldom attract much attention unless some important
crop is attacked. This is due (1) to the fact that the moths are
small and inconspicuous, (2) to the underground feeding habits of
the arvge, land (3) to the fact that damage from different species is
distributed throughout the growing season.

1 Dyar, narrison O. A List of North American Lepidoptera * * *. U. S. Nat. Mus. Bui. 52, pp,
404-410, 1902,

THE SO-CALLED TOBACCO WIREWORM IN VIRGINIA. 6

The principal species of the genus of economic importance in this
country are: Cramhus caliginosellus Clemens, which attacks tobacco
and corn; C. vulgivagellus Clemens, an enemy of corn, wheat, rye,
and grasses; C. trisectus Walker, an enemy of grasses, oats, and corn;
C. laqueatellus Clemens, which attacks corn and oats; C. zeellus Fer-
nald, C. luteoIeUus Clemens, and C. mutahilis Clemens, enemies of
corn; and C. hortuellus Hiibner, which is injurious to the cranberry.
Tlie wide distribution of several of these and their great capacity for
injury give them rank as species of considerable economic impor-
tance. Damage by them to cultivated crops is, in most cases, the
result of unusual conditions. Then- range of food plants is not
large, and the larvae are inclined to remain in or near one place.
The moths frequent the weedy fields, pastures, or meadows which
contain the natural food plants of the larvae, and the greater num-
ber of eggs are deposited in such localities. When such land is
plowed up the larvae are forced to live on other than their natural
food plants. With crops such as corn and tobacco this means a
concentration of larvae from many of the wild or natural food plants
to the comparatively few cultivated plants.

ECONOMIC IMPORTANCE OF THE TOBACCO CRAMBUS.

The tobacco Crambus {Cramhus caliginosellus Clem.) occurs in
most, if not all, of the tobacco-growing districts of the Eastern
States, but it seems to be most destructive in certain sections of
Maryland and Virginia. It is especially destructive in the famous
"dark-tobacco district" of the Piedmont section of middle Virginia,
although found in all sections of the State in which tobacco is
grown. In Virginia the damage to the tobacco crop alone from
the insect is estimated to average at least $800,000 annually.

At the Virginia tobacco experiment, stations, at Appomattox,
Bowling Green, and Chatham, injury has been recorded for a num-
ber of years. The reduction in value of the crop has been great,
amounting to about 14 per cent annually, through failure to secure
an early stand of plants. At the Appomattox Station, in one of
the experimental fields, there was a loss in 1910 amounting to
about 27 per cent. In 1911 there was still greater loss in some
of the plats. In many fields in the county fully one-half of the
plants were attacked, making several replantings necessary. At
the Chatham Station in 1909 there was an estimated decrease in
the value of the crop amounting to about $15 per acre.

In 1912 considerable damage occurred to tobacco in Montgomery
County, Tenn., and in Christian and Todd Counties, on the south-
ern border of Kentucky, growers in a number of instances report-
ing fully 40 per cent of the plants destroyed.

BULLETIN 78, U. S. DEPARTMENT OF AGRICULTURE.

The insect has for many years been a serious pest to tobacco and
corn in Maryland. W. G. Johnson, formerly State entomologist,
recorded the species as extremely abundant and destructive in
Prince Georges, Cecil, Kent, Queen Anne, and Dorchester Coun-
ties in 1897, and reported damage in various parts of the State in
1898, 1899, and 1900, many fields of young corn being almost com-
pletely destroyed.

M. H. Beckwith mentions it as injurious to corn in Delaware, and
John B. Smith has recorded injury to corn in New Jersey.

ORIGIN AND DISTRIBUTION.

Cramhus caliginosellus has been recorded only from North Amer-
ica. Its preference for the naturahzed buckliorn plantain and ox-
eye daisy as food plants, however, points to the possibiUty that it
has been introduced from Europe.

In literature the recorded distribution of the species is as follows:
Ontario (Saunders, Felt, and Fernald); New York (Grote, Felt, and

Fernald); Delaware (Beckwith); New
Jersey (Smith); Maryland (Johnson
and Howard); Massachusetts, Penn-
sylvania, District of Columbia, North
Carolina, Illinois, and Texas (Fer-
nald); Virginia (Mathewson, Ander-
son, and Runner); Ohio (Gossard).

In collections in the National Mu-
seum are specimens from the follow-
ing locahties: Washington, D. C.
(August Busck); Plummers Island,
Md. (H. S. Barber); Plainfield, N. J.
(F. O. Herring); Pittsburgh, Pa. (H. Engel); Clarksville, Tenn.
(A. C. Morgan); Chapel Hill, Tenn. (G. G. Ainslie); Vienna, Va.
(R. A. Cushman).

Records of the Bureau of Entomology show the insect to be present
in Pennsylvania, Delaware, Maryland, Virginia, West Virginia, North
CaroUna, South CaroUna, Oliio, Tennessee, and Kentucky.

These records indicate a wide distribution, but as most reports of
injury to cultivated crops come from certain portions of the Eastern
States it is probable that severe injury occurs only in localities where
natural food plants are exceedingly abundant, and where crops
subject to injury are planted at the time the larvae are completing
their growth and are in their most active feeding stage.

SEASONAL HISTORY.

The motlis (fig. 1) emerge during summer, the heaviest emergence
occurring at Appomattox, in central Virginia, during tlie first and
second weeks in August. The earliest emergence takes place during

Fig. 1 .—Adult, or moth, stage of the tobacco
Crambus,or " wireworm" { Crambus cali-
ginosellus). Enlarged. (Original.)

THE SO-CALLED TOBACCO WIREWORM IN VIR(iINIA.

the latter part of June, but moths are not abundant until about the
third week in July. From this time their numbers gradually increases
until about the second week in August, when they are exceedingly
numerous, at times appearing almost in swarms in weedy fields when
disturbed. From the middle of August there is a rapid decrease and
after the 1st of Septemlier only an occasional one can be found.
Table I gives dates of emergence of moths from some of the field
cages at Appomattox in 1910.

Table I. — Emergence of moths of the tobacco Crambun iir outdoor rearing cages at Appo-
mattox, Va., 1910.

Larvae col-
lected—

Food plant on
which found.

Moth
emerged—

Larvae col-
lected--

Food plant on
which found.

Moth
emerged—

1910.

1910.
July 2.
July 21.
July 22.
Aug. 3.
July 3.
July 14.
July 22.
July 23.
July 26.
Aug. 1.
July 29.

N

1910.

June 26

Do

Do

Do

Tobacco

1910.
July 18.

Do.

do

Wild carrot

Tobacco

Aug. 13.

Do

do

Aug. 6.

Do

.do

do

Aug. 15.

....do

June 28

Do

Do

July 1

Plantain

July 14.

Do

Corn

Daisy

Aug. 15.

Do

Aster (stickweed) .
Plantain

Aug. 7.

Do

July 29.

Corn

Do

Do

Tobacco

Aug. 14.

Do

Corn

July 27.

Do

Aster spp

The females die soon after egg laying is finished. There is appar-
ently only one generation a year, the eggs hatching in summer and
the larvfe coinpleting their growth during the follow-
ing year. The greater number of larvae are in the pupal
stage during the first half of July.

DESCRIPTION.

THE EGG.

The egg (fig. 2) is creamy white when first deposited, but grad-
ually assumes a pinkish shade, which deepens to orange rufous
before hatching. The average length is 4 mm. and the diameter
0.32 mm. It is regularly oval, with the ends slightly truncate,
and has a polished appearance. There are about 18 longitudinal
carinse and numerous transverse stri*.

THE LARVA.

FIRST INSTAR.

When first hatched, the body of the larva is semi transparent, and the alimentary
canal can be plainly seen. The outline of the body, when seen from above, is almost
triangular. The larva is white, or pale yellowish white, and about 1 mm. long, with
a few scattered, light-colored hairs on the head and body. The head shield measures
0.15 mm. in width, is yellowish brown, and moderately bilobed, with the clypeus
attaining the apical third. The cervical shield is tinged slightly with brownish.
Five pairs of prolegs occur on the 7th to 10th segments, inclusive, and on the 13th
segment.

LAST INSTAR.

The full-grown larva (figs. 3, 4) is about 1.5 mm. long, and yellowish white, with a
tinge of pink dorsally. The hairs of the body are slender, browjiish, and set on large
fuscous tubercles. The head shield measures 1 .2 mm. in width, and is pale yellowish

Fig. 2.— The to-
bacco Crambus:
Egg. Greatly
enlarged. (Origi-
nal.)

6

BULLETIN 78, V. S. DEPARTMENT OF AGRICULTURE.

Fig. :<— The tobacco Crambus: Full-grown larva, or "wlreworm.
Much enlarged. (Original.)

browni, flecked with darker brown. The cervical shield is distinct, shining, yel-
lowish brown, tinged with fuscous, and bears 12 hairs in two transverse equal rows.
The anal shield is pale fuscous. About the middle of abdominal segments 3, 4, 5,
and 6, and slightly above the spiracles, is a series of distinct, dark fuscous, chltinous
ureas about the size and shape of spiracles, one to each segment.

The arrangement of the tubercles is as follows: Beneath the anterior margin of the
rer\ncal shield is a tubercle bearing two hairs. The mesothorax above bears eight

setigerous tubercles on the
anterior margin, each, ex-
cept the lateral tubercle,
with two hairs. Posteriorly
it is provided vrith three bare
tubercles, of which the medi-
an is narrow and transverse.
The metathorax is armed,
as is the mesothorax . Each
abdominal segment above the spiracles bears two transverse rows of four tubercles
each. The anterior dorsal pair are subquadrate, with the posterior lateral angles
strongly rounded. The posterior dorsal pair are oblong, transverse, about half as
long as the anterior, with the posterior lateral angles strongly rounded. The anterior
lateral tubercles are supraspiracular, irregularly quadrate, with the lower margin
produced diagonally behind the spiracle, emarginate at the spiracle and before the
impressed area on segments 3, 4, 5, and 6. The
corresponding tubercle on segment 8 has the pro-
duced portion isolated and is placed anterior to the
spiracle. The posterior lateral tubercles are trans-
verse, elongate, and somewhat oblique.

Abdominal segments 1 to 7 each bear a minute
spinule anterior to and nearly equidistant from the
spiracle and the supraspiracular hair.

The legs are pale brown, the maxillary palpi
brown, and the mandibles brownish fuscous at
apices.

The color of larvae collected from differ-
ent food plants varies considerably, this
being merely an effect of the color, whether
light or dark, of the food in the alimentary
canal. Larvae collected from corn arc considerably lighter than those
collected from tobacco.

THE PUPA.

The pupa (fig. 5) measures about 8 mm. in length and 2 mm. in greatest width.
The general color is dark brown, or pale yellowish brown when newly transformed,
with the appendages and segments marked with dark brown. The head is blunt,
with a median apical emargination. The tt'ps of the wings are rounding on abdominal
segment 5; the margin of the inner wing is visible over segments 2, 3, and 4. The
spiracles are not prominent, the first three pairs being set on blunt tubercles. The
cremaster is transversely rounded oblong, with a lateral bristle near the apex.

THE ADULT, OR MOTH.

Expanse of wing, 13-25 mm. Head, palpi, and thorax dark fuscous, sprinkled with
gray scales. Fore wing dark fuscous, sprinkled with brown or yellowish, and fre-
quently with a few gray scales; median line dark brown, often edged with white, aris-

Fk;. 4.— 'I'he tobacco Crambus: Head
of larva. Greatly enlarged. (Origi-
nal.)

THE SO-CALLED TOBACCO WIREWORM IN VIRGINIA.

ing a little beyond the middle of the costa, extending outward, forming a very acute
angle, thence backward across the end of the cell to the hind margin, a little beyond
the middle, and giving off an outward angle on the fold. Subterminal line dark brown,
edged outwardly with dark lead-colored scales, and frequently dentate along the first
part of its course. It arises from the costa about half way between the median line and
the apex, extending down to a point beyond the end of the cell, where it forms an out-
ward angle, thence to the hind margin, a little within the anal angle, giving off an
inward angle on the fold. This angle is frequently connected along the fold with the
outward angle of the niedian line; terminal line dark brown, rather indistinct. The
lines are often obliterated more or less, especially the median. Fringes dark leaden
gray. Hind ^'^•ings dark fuscous; fringes a little lighter. [Fernald, I89G.] (See fig. 1.)

The moths vary somewhat m color and distinctness of markings,
some specimens being much darker than others when first trans-
formed. In the hind wing the frenulum is a single short spine in the
male. In the female the frenulum is more slender and is very finely
diA-ided at the tip. In the female of a number of other
species of this genus the frenulum consists of two dis-
tinct spines.

LIFE HISTORY.

HABITS OF THE MOTHS.

The moths fly during late afternoon, on dark days,
and during the early part of the night. They are
attracted to light, but in comparatively small num-
bers considering their great abundance at certain
times. The majority of the females collected at trap
lights are those which have deposited their eggs.
During the day, when disturbed, they make short,
erratic flights, usually alighting head downward on
the stems of weeds and grasses, their tightly closed
wings and grayish color making them very inconspic-
uous. As wdth other members of the genus Crambus, their long palpi,
extending parallel to the stem of the plant on which they are at rest,
help to make the outlines of the body conform to the appearance of
that part of the plant.

OVIPOSITION.

When the moths were confined in cages, the eggs were deposited at
random over the surface of the ground. They seemed dry when
de])osited, rolled about easily, and did not adhere to papers placed
over the soil in the rearing cages, or to glass when females were con-
fined in large test tubes. Normally the eggs are doubtless placed in
the same manner, for on two occasions eggs were found on the upper
surface of leaves of sweetbrier lying flat on the ground. Egg laying
commences shortly after the moths emero;e. Fertile esro-s were not
obtained from moths reared in the cases.

Fig. 5.— Thetobacco
Crambns: Pupa.
Much e n la r g e d .
(Original.)

8

lU'l.LETIN 78, r. S. DKPAHTMENT OF ACJKICn.TUKE.

Records obtained from a lari:;c number of females, collected in the
fields and placed in separate cages for egg deposition, show the average
number of eggs laid to be 1 77. Among the records obtained at Appo-
mattox, Va., during 1910, are those in TaWe IT.

Tablk II. — Number of eggs laid by the tobacco Crambus. Appomattox, Va.. 1910.

No.
of fe-
male.

Moth collected.

Feriod of ovipo-
sition.

Num-
ber
eggs
laid.

No.
of fe-
male.

.Molli collecte!.

I'eriofl of ovipo-
.sition.

Num-
ber
eggs
laid.

1

1910.

July 8

do

1910.
July 9-13

218
68
271
156
211
316
287
77
301

10
11
12
13
14
15
16
17

1910.

Aug. 11

do

Aug. 14

do

Aug. 15

do

1910.

-Vug. 12-15

Aug. 12-16

Aug. 1,5-20

Aug. 1,5-18

Aug. l(>-20

Aug. 16-19

Aug. 16-21

Aug. 16-18

83

2

.....do

203

3

do

July 10

July 12

July 17

July 9-14

218

4

July 11-14

194

5

July 13-18

222

(3

July 18 22

91

July 18-23

do

do

238

8

July 25

Aug. 11

July 26-30

03

9

Aug. 12-16

Several individual females laid over 300 eggs, and over 300 were
obtained in several instances by dissection. It is probable that tlie
average number of eggs deposited normally is above rather than
below the average obtained in the cages, as some of the moths may
have laid eggs before capture, although records were not included
from moths which deposited eggs within 12 hours after capture.^

The period of oviposition lasts from 3 to 5 days, the females dying
shortly after egg laying is finished. The records of two females col-
lected in the field on August 10, 1010, are given in Table III.

Table 111. — Rate of oviposition of the tobacco Crambus, Appomattox, Va., 1910.

Female No. 1.

Num-
ber of
I eggs de-
[posited.

1910.

Aug. 11

Aug. 12

Aug. 13

Aug. 14

Aug. 15

Total

Female No. 2.

1910

Aug. 10

Aug. 11

Aug. 12

Aug. 13

Total

Num-
ber of
eggs de-
posited.

DURATION OF THE EGG STAGE.

The period of incubation was found to be from 5 to 9 days, tlie
greater number of eggs hatching about the sixth day at ordinary
summer temperatures.

' The dissection of 17 females of Crambus caliginosellus collected in the field during the third week in
July, 1912, showed that 8 of the 17 collected contained more than 100 eggs. The number of eggs (mature
or nearly mature) found in the s moths containing more than 100 eggs was as follows: 143, 322, 127, 290,
307, 124, 342, 208.

j|. 78, U. S. Dept. of Agriculture.

Plate I.

Fig. 1.— Injury of the Tobacco Crambus, or "Wireworm," to Tobacco.

Fig. 2.— Injury of the Tobacco Crambus, or "Wireworm," to Corn.
WORK OF THE TOBACCO CRAMBUS.

Bui. 78, U. S. Dept. of Agriculture.

Plate II.

i

Fig. 1.— Poor Stand of Tobacco Resulting from Planting on Weedy Land.
Note heavy growth of oxeye dai^y in jiart of field not in tobacco.

^

:^t>!::^ ^^^;---^^|^

-

»r;

-rr- r-«^,.::'.;^'^:'"%<tjt^

m
t

Fig. 2.— Wild Carrot and Other Weeds in Field of Red Clover.
Injury from the " wireworin" occurs when land of tliis kind is planted in tobacco or corn.

RELATION OF WEEDY LAND TO INJURY BY TOBACCO CRAMBUS.

THE SO-CALLED TOBACCO WIREWORM IN VIRGINIA. 9

Table IV. — Duration oj egg stage of the tobacco Cramhus, Appomattox, Va., 1910.

Lot

No.

Kggs laid—

Eggs hatching —

Incuba-
tion
period.

Lot

No.

Eggs laid—

Eggs hatching—

Incuba-
tion
period.

1

19in.

Julv 7

July 11

July 12 .

1910.
Julv 12 .

Days.

5

S-9
7

6-7
6

6-7

5-<5

8
9
10
11
12
13

1910.

Aug. 12

Aug. 13

1910.

Aug. 17-18

do

Day^.
5 6

2

July 19-20

.Tulyl9 . .

4-5

3

Aug. 14

Aug. 15

Aug. 16

Aug. 17

Aug. 19-20

Aug. 20

5 6

4

July 1.3

July 19-20

July 31

Aug. 1-2

Aug. 16-17

5

5
6

7

Julv 25

July 26

Aug. 11

Aug. 21-22

Aug. 23-24

5-6

(i-7

HABITS OF THE LARV.«.

NATURAL FOOD PLANTS.

Larvae of the tobacco Crambus liave been found feeding on the
following wild plants:

Buckhorn plantain {Plantago lanceolata).
Oxeye dai.sy ((^hrjjsanthemwn leucanthe-

mum) .
Wild aster or "stickweed "' {Aster eri-

coides and other species).

Wild carrot (Daucus carota).
Sheep sorrel {Rumex acetoseUa) .
Senecio {Senecio jacobse.a) .
White-top (Erigeron annuus and other
species).

The first two plants named, the buckhorn plantain and the oxeye
daisy (PI. II, fig. a), were found to be the main food plants of the
larvae in the locaUties studied. The eradication or control of these
weed pests, therefore, will result in comparative immunity from loss
by this insect. Both species of plants have been found heavily
infested in many localities in widely separated sections. During
early spring the plantain seems to be the preferred food plant; later
a heavy infestation occurs on both plantain and daisy.

On July 8, 1910, 23 out of 25 oxeye daisy plants examined in a
weedy field were infested, there being a total of 69 larvae about the
roots. As many as 20 larvae have been collected from one plant of
the oxeye daisy.

In tobacco-growmg sections of Tennessee and Kentucky white-top
is a frequent food plant.

When meadows are plowed up and planted to tobacco there is
frequently serious injury from the "wireworms." (See PI. II.)
Where such injury has occurred the weeds mentioned above have
invariably been found abundant in the sod, which explains the pres-
ence of the ''worms." Injury has not been observed where there had
been previously a clean growth of grass or clover. Attempts to rear
adults from larvae confuied in field cages containing only timothy and
clover resulted in failure, although the larvae lived for a considerable
time Avithout other food.

30183°— Bull. 78—14 2

10 BULLETIN 78, U. S. DEPARTMENT OF AGRICULTURE.

INJURY TO TOBACCO.

The tobacco is attacked soon after planting, and feeding by the
larvae continue^ until the first or second week of July. The larvae
usually commence operations just below the surface of the ground,
although newly set plants are frequently attacked at the "bud" or
whorl of terminal leaves. As feeding continues the larvae, especially
the smaller ones, frequently enter the stalk and tunnel upward, the
burrows often extending to the base of the first leaves and some dis-
tance above the surface of the ground. (See PI. I, fig. a.) When not
feeding the "worms" are found al)out the base of the plant, usually
in cylindrical, web-lined galleries, wliich extend from the plant, often
for several inches, beneath the surface of the soil.

Injured plants may usually be detected by their stunted or wilted
appearance, which is more noticeable during hot, dry weather. The
stems are in some cases entirely cut off, although this form of injury
is rather unusual.

Although plants often partially recover they do not obtain full
growth, and it is evident that the presence of many dwarfed or
stunted plants must result in very materially lessening the yield. The
value of the crop is greatly decreased also, owing to the large proportion
of late plants resulting from replanting. Early planted tobacco is
usually better in quahty than the late planted, it being finer and
more elastic, curmg better, and consequently bringing higher prices.
The attacks of the larvae often make it necessary to reset the crop
several times, and a good stand of plants is not secured, if at all, until
too late to make the crop as profitable as it should be.

INJURY TO CORN.

Owing to its wide distribution in the Eastern States the tobacco
Crambus is a serious pest to the corn crop. Injury has been noted
in many localities where little tobacco is grown, and it is probable
that damage to corn amounts to even more than that to tobacco.
As with tobacco, injury is most severe when corn is planted on land
which has been in weedy pasture or meadow previously, or when
planted on land wliich has not been under cultivation for a number
of years and on which there has been a rank growth of weeds. On
such land it is usually difficult to secure a satisfactoi-y stand of corn,
and the yield is greatl}^ reduced. (See PL I, fig. h.) In central
Virginia many fields under observation were replanted several times,
and ow^ng to the lateness of the season when a stand was secured
the value of the crop was decreased fully one- third. Corn or tobacco
planted on newly-cleared land seldom suffers injury from the Crambus.
Since the species of weeds which are the natural food plants of the
insect do not thrive in woodland, the larvae are not present when the
crop is planted.

THE SO-CALLED TOBACCO WIRE WORM IN VIRGINIA. 11

The larvae attack the young corn near the surface of the ground and
burrow hito the l)ase of the stalks, the outer portion of the stalk being
fj-equently girdled. If the stalks are small when attacked, they are
either killed or so stunted or dwarfed that they never fully outgrow
the injury, and produce little or no grain. Much of the corn is
attacked just after the seed has sprouted. The larvse frequently
burrow into the folded leaves as the corn is coming through the
ground. As the leaves unfold they show transverse rows of holes.
When the stalks reach a height of a foot or more comparatively Httle
(himage is done. Several larvse are frequently found about the roots
of a single stalk, and as many as 22 have been collected from a single
hill of corn. In wet weather injury is not apt to be so severe, as
the plants are then more vigorous and the weeds, which furnish suit-
able food for the worms, more plentiful. As with tobacco, corn is
attacked when the natural food supply of the "worms" is cut off.

GENERAL FEEDING HABITS.

The feeding habits of the "wireworm" on plants other than corn
and tobacco are, in a general way, the same. There is a tendency to
girdle soft-rooted plants, such as plantain and the wild carrot (PI. II,
fig. h), and the larvse are often found embedded in cavities where they
have fed. The buckhorn plantain {Plantago lanceokita) is frequently
Idlled where the infestation is heavy. A marked preference is shown
for the natural food plants, and farmers, when the larvae are especially
troublesome, frequently take advantage of this fact by cultivating at
first only one round to the row, allowing the weeds to grow in the
center of the row until the corn or tobacco has become better estab-
lished. In a plowed field the larvse, if they have not finished feeding,
concentrate about plantain, daisy, and stickweed {Aster spp.) which
have not l)eeii killed by plowing.

The larvse do not seem to travel far in search of food, as was
ascertained by plowing badly infested land adjoining fields of corn
and tobacco. When disturbed they crawl actively in either direc-
tion, and they will often spin a slender silken thread ])y which they
may be suspended. They feed most actively at night.

THE PIIP.«.

The larvse pupate in the soil near the plants on which they feed.
Before pupation there often seems to be a rather long period during
which the larvse remain inactive in their cells. The pupal cells are
usually found at a distance of from 1 inch to 6 inches from the base
of the food plant and at a depth varying from one-haK inch to 4
inches.

Table V shows the depths at which pupse were found al)Out various
food plants in soils varying from hard stiff clays to loose sandy loams.

12

BULLETIN 78, U, S. DEPARTMENT OF AGRICULTLTRE.

Table V. — Depth at which pupation of the tobacco Crambus takes place, Appomattox,

Va., 1910.

Date.

Character of .soil.

Food plant.

Depth.

Date.

Character of soil.

Food plant.

Depth.

1910.
July 9
Do

Red clay

Tobacco....
. ...do

Inches.
2.5
3.5
1

.5
i
3.5

1910.
July 11
Do

Red clay

Tobacco

Corn

Daisy

Plantain . . .
Daisy

Inches.
1

Sandy loam

do

2.5

Do....

do

Plantain...
.do

Do....
Do....
Do....

Sandy loam

Rod clay

Do

Red clay

1

Do. .

Black loam

Gray sandy loam..

Daisy

Tobacco

do

1.5

July 11

Numerous measurements made at different times gave results very
similar to those shown above. The average depth at which pupation
takes place was found to be about 1.5 inches.

The cells averaged about 9.5 mm. in length and 4.5 mm. in width
(inside measurements). The lower portion of the cell is usually
somewhat larger than the upper portion, the pupa l3'ing in the larger
end of the cell in convenient position for its egress. The cells are
extremely fragile and are easily broken when removed from the soil.
They are constructed of fine particles of earth and grains of sand in-
terwoven with a silky weblike material. The walls are thin and the
interior surface quite spiooth.

The ])upal period, as shown in Table VI, lasts from 10 to 15 days.

Table VI. — Pupal period of the tobacco Crambus, Appomattox, Va., 1911.

Larvae
collected—

Pupated —

Moth
emerged —

Num-
ber of
days.

Larva?
collected —

Pupated—

Moth
emerged—

Num-
ber of
days.

1911.
June IS

Do

June 20

Do

Do

July 1

1911.
July 7-10. . . .
,Tulv 10-11...

July 7-9

July 12

July 15

July 28-31...

1911.

July 21

do

July 22

do

July 26

Aug. 10

11-11
10-11
15-17
10
11
10-13

1911.

Julyl

July 12

'Do

Do

Do

Do

1911.
July 8

Aug. 1-3

July 15

July 28-31. . .

Aug. 1-2

Aug. 1

1911.

JiUy22

Aug. 15

Aug. 1

Aug. 10

Aug. 15

Aug. 12

14
12-15

15
10-13
13-15

12

Table VII shows the duration of the period during which the
insect is in the pupal cell before and after pupation.

Table VII. — Duration of prepupal and pupal periods of the tobacco Crambus at Appo-
mattox, Va., 1911.

Num-
ber of
record.

Larvae ceased
feeding—

Moth
emerged—

Days.

Num-
ber of
record.

Larvae ceased
feeding—

Moth
emerged—

Days.

1

1911.
June 18

1911.

July 10

July 15

July 1(1

July 18

July 20

July 19

22

27
28
15
17
16

8
9
10
11

1911.

July 9

July 11

July 13

1911.
Aug. 1

23

2

. do

July 24

July 29

Aug. 3 . .

13

3

. ...do

16

■4

July 3

July 14

20

5

do

do

July 29

15

6

....do

THE SO-CALLED TOBACCO WIEEWORM IN VIRGlK'lA. 13

NATURAL ENEMIES.

In spite of its long larval period the tobacco Crambus does not
seem to be largely parasitized, at least during the later stages, this
being due presumably to the subterranean habits of the larvae and
the protection afforded by the loose web in which they usually lie
when not feeding. Nevertheless parasitic and predaceous enemies
are doubtless factors in keeping the insect in check. The vast num-
ber of newly hatched larvae as contrasted with the number found
later in the season shows that comparatively few survive the earlier
larval stages. This reduction is due in part to various natural ene-
mies the exact or relative importance of which it is hard to estimate.

Various carabid beetles have been observed to feed on the larvse.
Among them were Calosoma calidum Fab. and CMsenius tornentosus
Say. Adults and larvae of Harpalus (Harpalus pennsylvanicus De G.
and H.faunus Say) were observed to be very abundant about roots
of oxeye daisy and plantain which were heavdy infested with
Crambus larvae. As the species of Harpalus are known to be gen-
eral feeders, they were thought to feed on the larvae of the Crambus.
The adults, when confined in tubes with larvae, occasionally fed on
them.

Spiders of several species were observed to feed on the larvae, and
large numbers of the moths are captured in spider webs in weedy
fields.

Ants also occasionally attack the larvae. An ant found carrying
a partly grown larva at Chatham, Va., was examined by Mr. Theo-
dore Pergande and found to be a species of Solenopsis.

W. G. Johnson, in Maryland, reported the rearing of an undeter-
mmed hymenopterous parasite from the larvae. No parasitic
Hymenoptera were secured from the rearing cages at Appomattox,
although large numbers of larvae were confined.

Several Diptera were observed in cages containing larvae on vari-
ous occasions, but actual proof of parasitism was not obtamed,
although a species of Phoridae was secured from tubes containing
larvae under circumstances pointmg strongly to parasitism.

In the National Museum are specimens of a hymenopterous para-
site, Perisemus prolongatus Prov., labeled as reared from larvae of
Cramhus caliginosellus from La Fayette, Ind. The record is doubt-
ful, however, as the notes concerning the specimens in the files of
the Bureau of Entomology clearly refer to a different species of
Crambus as the host.

Birds are a factor in keeping the tobacco Crambus m check. Two
species, the quail {Colinus virginianus) and the kingbird {Tyrannus
tyrannus) were observed by the writer to capture the moths, and
others are known to feed freely on moths of this genus. F. M. Web-
ster states that the wood pewee (Myiochanes virens) was observed to

14 BULLETIN 78, U. S. DEPARTMENT OF AGRICULTUBE.

destroy large numbers of Cramhus laqueatellus at Haw Patch, Ind.,
and C. H. Fernald observed barn swallows feeding on different species
of Crambus in JSIaine. Meadowlarks frequent weedy fields which
harbor the larvae of Crambus, and as these birds are known to feed
on various species of cutworms, they doubtless feed also on the larvae
of the tobacco Crambus.

REPRESSION.

CULTURAL METHODS OF CONTROL.

Injury from the to'oacco Crambus occurs where crops susce})tible
to injury are grown on weedy land. Tobacco or corn planted on land
which has been under clean cidtivation the previous year and kept
free from weeds which live throughout the winter does not suffer
serious injui-y. The larvse can not live over winter in the soil from
tlie previous summer unless plants on which they are able to feed are
present. All field experiments and observations so far have shown
that the most effective means of control consist of freeing the land
from the weeds, such as buckhorn plantain, daisy, stickweed, etc.,
which have been found to be the natural food plants of the larvae.

Tliere are many methods by which weeds may be eradicated or
controlled, but the most practical and effective is the systematic
rotation of crops. Sowing clean seed, preventing weeds from ripen-
ing seed, fall or winter plowing, the use of lime or of certain fertil-
izers, and doing away with wide fence rows are important preven-
tive measures. Mowing and burning over weedy fields destroys
many weed seeds and weeds which live over winter, and also destroys
many injurious insects. Burning during August or September has
been found to destroy the eggs and young larvas of the tobacco
Crambus, but as this method destroys humus, which is so badly
needed in most tobacco soils, it is in most instances not advisable.

Many weeds are "soil indicators," their presence showing that the
soil is lacking in fertility and in some instances pointing to a deficiency
of lime.

CLEAN SEED.

One of the main factors in the control of weeds is clean seed, and
the importance of procuring such seed can hardly be overestimated.
Many weed pests are introduced and disseminated in the seed of
various crops, such as grass and clover. As tobacco or corn must
frequently be grown on land which has previously been in these
crops, and as injur}^ from the tobacco Crambus is apt to occur if the
meadows have been weedy, it is desirable, for this and other reasons,
to have the meadows as free from weeds as possible.^ Owing to

1 An analysis made by the Massachusetts Experiment Station shows that 1 ton of oxeye daisy (cured)
withdraws from the soil approximately 25 pounds of potash, 8.7 pounds of phosphoric acid, 22 pounds of
nitrogen, and 20 pounds of lime. To restore the stated amounts of the first three constituents to the soil
it would be necessary to apply about 50 pounds of muriate of potash, 65 pounds of superphosphate, and
140 pounds of nitrate of soda. (Farmers' Bui. 103, U. S. Dept. Agr.)

THE SO-CALLED TOBACCO WIEEWORM IN VIRGINIA. 15

careful cultivation of previous crops, the land is frequently fairly-
free from weeds when seeded to meadow; so that if the clover and
grass seed has been sown pure there ^\nll be few^ weeds in the tobacco
field or cornfield.

An examination of samples of clover and grass seed procured
from farmers and seedsmen in various sections of Virginia shows
that seeds of buckhorn plantain and oxe5^e daisy — both natural food
plants of the tobacco Crambus — are common. Of 30 samples ex-
amined by the seed expert of the Virgmia State department of
agriculture during 1910, 28 contained seeds of oxeye daisy, and of
these, 5 contained plantain and daisy. Of 70 samples of clover,
redtop, and timothy seed exammed at the Virginia Experiment
Station in 1909, seeds of buckhorn plantain were found in 16.*

The United States Department of Agriculture and those in charge
of similar work in many of the States have provided means by wdiich
samples of seed may be examined for purity by experts. Some of
the States, also, have laws compelling dealers to furnish a stated
guaranty as to the purity of the seeds sold.

WEEDS TO BE ELIMINATED.

The buckhorn plantain (Plantago lanceolata) is one of the numer-
ous naturaHzed weed pests from Europe. It ranks among the worst
weeds, particularly upon the fighter soils and on clay uplands.
"Ray-bud," "rib-grass," "ribwort," "buck plantain," "English
plantain," "ripple," "ripple grass," and "narrow plantain" are
names appfied to the plant in different sections. It is perennial
or biennial and is common in meadows. The seeds are widely dis-
tributed with clover seed, from which it is difficult to separate them.
Rotation of crops, thorough cultivation, and the use of clean farm
seed are the usual methods for its control.

The oxeye daisy {Chrysanthemum leucanthemum) (PL II, fig. a)
is also a naturalized species from Em'ope. It is often abundant on
old or poor soil. It spreads from the seeds, which are distributed
in various farm seeds, in hay, and in manm'e; also, by shoots from
the perennial root stocks, which must be entirely killed before the
plant can be whoUy eradicated. It is best controlled by rotation of
crops, by smothering out by means of cowpeas or other suitable
soiling crops, and by thorough cultivation. It is a bad weed pest
in meadowland. The seed can be prevented from ripening by
mowing the hay early.

Wliite top or fleabane (Erigeron annuus and other species) is a
common pest in meadows. In some locaUties it has been found to
be a loodi plant of the tobacco Crambus. Early mowing of infested
meadows before the seeds ripen and pastm'ing with sheej), which

1 Bui. 184, Va. Agr. Exp. Sta.

16 BULLETIN 78, U. S. DEPARTMENT OF AGRICULTURE.

readily eat the weed, are control methods commonly practiced.
Chemical sprays are fairly effective, but can not be used in meadows
where clover is grown, as clovers are killed by the solution. Sprays
have been found most effective while the plant is in bloom.

The stickweed or aster (Aster ericoides), known also as frost-
weed, steelweed, white heath, etc., and related species, are com-
mon and abundant weeds in old fields in tobacco-growing sections
of the Atlantic States. They are perennial and thi-ive on poor soil.
It is useless to try to eradicate them completely, but they can be
readily controlled by growing cultivated crops and by putting the
land in a higher state of fertility by the use of hme and clover.
Aster is not a usual food plant of the tobacco Crambus, but as the
weed is so frequently associated with daisy and plantain, which
thrive best under similar soil conditions, its control is essential in
the preparation of land for tobacco.

CROP ROTATION.

One of the main reasons for a rotation of crops is that the accumu-
lation of weeds in meadowland and pastures may be destroyed
during the cultivation of the crop that follows. • A rotation found
very satisfactory by the Virginia experiment station has been
devised by Mr. E. H. Mathewson, Crop Technologist of the Bureau
of Plant Industry. Tliis plan is slightly modified to meet condi-
tions in different tobacco-growing sections. It calls for a seven-
year rotation of crops, as foUows: First year, tobacco, fertilized
heavily; second year, wheat without fertilizing; third and fourth
years, mixed grasses and clover, seeded alone early in the fall and
top dressed early in the spring with 200 to 300 pounds of nitrate of
soda; Jlfth year, corn, with barnyard manure and a small amount of
fertiUzer; sixth year, cowpeas, fertilized with a little acid phosphate
and sulphate of potash; seventh year, tobacco.

Crops such as cowpeas, soy beans, and crimson clover, which aid so
greatly in fitting land for increased and more profitable yields of
tobacco and corn, not only add humus to the soil and increase the
fertility, but help to eradicate certain weeds by smothering them out.
The weeds are also destroyed or prevented from maturing seed when
crops are plowed under. Although eggs of the Crambus may have
been deposited in such a field, the larvae can not survive until the
tobacco is planted unless there are weeds which remain alive over
winter to supply them with food.

The following rotation experiments have been under observation
during the present investigation:

A test with tobacco following crimson clover was conducted as a
cooperative experiment on the J. R. Horsley farm in Appomattox
County, Va., in the season of 1910-11. The field selected contained

THE SO-CALLED TOBACCO WIREWORM IN VIRGINL\. 17

4 acres. It was in corn during the season of 1910. Previous to plow-
ing for corn the field was in weedy sod. The corn was badly injured
by the Crambus and was replanted twice. At the last cultivation of
corn in July, crimson clover was sown. Rains were frequent during
the latter part of the summer, and a fairly good stand of clover was
secured. There were some weeds, in spots, which cultivation at the
time clover was sown had not destroyed. The field was planted to
tobacco during the season of 1911. Damage by the Crambus was
estimated to be about 6 per cent.

A test with tobacco following cowpeas was conducted as a coop-
erative experiment on the S. L. Ferguson farm, Appomattox County,
Va., in the seasons of 1911 and 1912. A field containing about 6
acres was used in the experiment. The land previous to plowing for
cowpeas was in weedy pasture, and numerous Crambus larvie had
been observed. A good growth of the cowpeas was secured. The land
was deeply plowed during winter and was prepared for planting to
tobacco during the third week in May, 1912. Scarcely any injury
from the Crambus to the first planting was observed. After the first
planting damage from the Crambus and from other causes was esti-
mated to be less than 4 per cent. In the check field, where conditions
were similar to those in the experimental field, except that a crop of
cowpeas had not been grown, there was an estimated damage from
the Crambus of about 9 per cent. The sod in the check had been
winter-plowed.

In the plats of the Virginia Tobacco Experiment Station, at Appo-
mattox, nine experiments were under observation, as detailed below.

The first experiment was with tobacco planted on sod in an old
weedy pasture. A large part of the first planting was destroyed.
The plat was replanted three times. About 9 per cent of a stand was
secured by the second week in July. Owing to injury from " wire-
worms" and the large percentage of late plants the value of the crop
was decreased 25 per cent as compared with plats in which an early
stand of plants had been secured.

The second experiment was with tobacco following cowpeas on
land that had been uncultivated for several years and was very weedy.
Almost a perfect stand of plants was secured at the first planting,
which was made the last week in May. The injury (decrease in the
value of the crop) was less than 1 per cent.

The third experiment was on a plat used for fertilizer tests. The
condition of the land was similar to that used in the second plat,
except that cowpeas had not been grown during the preceding season.
The tobacco was replanted three times. The decrease in the value
of the crop was 7 per cent.

18 Hri.l.KTlN 7S, U. S. DKPAHTMKNT OF A( iKICLJl.TrRE.

The fourth experiment was again with tobacco planted on sod.
There were few weeds in the sod. Nearly a perfect stand of plants
was secured at the first planting, which was made during the last
week in May, The plat was replanted once. The loss was esti-
mated at less than 1 per cent.

The fifth experiment was again with tobacco following cowpeas.
A perfect stand of plants was secured at the first planting, made
duiing the last week in May. Injury from the tobacco Crambus was
estimated at less than 1 per cent.

The sixth experiment was with tobacco planted on red-clover sod.
The stand of clover had been good and there were few weeds. To-
bacco was planted during the last week in May. A good stand was
secured at the first planting. Loss from the Crambus was estimated
at less than 1 per cent.

The seventh experiment was on spring-plowed land where stick-
weed, daisy, and plantain had been abundant. The tobacco was
planted during the second and third weeks in May. The loss was
estimated to be about 20 per cent, owing to late plants, the tobacco
having been replanted three times. Injury from the Crambus was
worst in the portion, of the field where weeds had been most abundant.

The eighth experiment was with tobacco following rye. The
stand of rye had been poor and the stubble was weedy. The first
planting was made on June 8, and was almost completely destroyed.
Tobacco was replanted three times. A stand of 90 per cent was
secured by the second week in July. The estimated decrease in
the value of the crop was about 30 per cent.

The ninth experiment was with tobacco fo^.owmg cowpeas. The
first planting was made on June 2. About 20 per cent of plants
were injured by ''wireworms.'' The plat was replanted once, there
being only slight damage after the second planting. The estimated
loss in value of the crop was about 10 per cent. Most of the injured
plants were in the end of the plat where the stand of peas had been
poor.

Three experiments were under observation at the Mrginia Tobacco
Experiment Station at Chatham in 1910 by Mr, R. P. Cocke, super-
intendent of the station.

In experiment No. 1 tobacco was preceded by corn in which
crimson clover was sown at the last cultivation. This clover was
fallowed May 2. The corn was kept clean of weeds and grass.
Tobacco was set June 6. The fu'st replanting was made June 14
with 5 per cent of the plants injured; the second replanting was
made June 23, with 3 per cent mjury; and the third replanting,
June 28, with 2 per cent injury. About 97 per cent of a stand was
finally secured after the third replanting.

THE SO-CALLED TOBACCO WIREWORM TN VTROINL4. 19

In experiment No. 2 tobacco followed corn, in a plat used for
fertilizer tests. • Tobacco was set June 6. The first replanting was
made June 14, with 5 per cent injury; the second replanting, June
23, with 3 per cent injury; and the third replanting, June 28, with
2 per cent injury. About 98 per cent of a stand was secured after
the third replanting.

In experiment No. 3 tobacco was phmted after a cover crop of
wheat, in variety test plats. The wheat was fallowed May 1 . Tobacco
was set June 7. The first replanting was made June 17, with 20 per
cent injury, and the second replanting, June 28, with 6 per cent
injury. About 95 per cent of a stand was secured. In these plats
it was estimated that about 5 per cent of the entire loss was due to
cutworms and to true wireworms (larvip of Elateridae).

SUMMEK PLOWING.

The moths are local in habits and do not fly far from the weedy
fields, which furnish protection for them and which are suitable
places for them in which to deposit eggs. On emerging from plowed
or bare land, or from fields in which the vegetation is not suitable
for protection or for egg deposition, they fly to surrounding fields
where conditions are more favorable. The land from which emer-
gence took place will then be left free from worms which, if present
would attack the crop the following year.

The preparation of weedy land for tobacco or corn must, therefore,
be commenced the season before the crop is planted. Best results have
been obtamed by summer plowing, as the land was thus rendered
bare of vegetation, and conditions were not suitable for egg laying
when the moths emerged. By this means infestation of the land is
prevented in the first place. It has been found that it is difficult
to prevent injury, or to eradicate the worms, if they have once
become established. Summer treatment of land makes conditions
unfavorable for the moths to deposit eggs, destroys weeds which
furnish food for the young larvae, and kills many of the insects while
in the pupal stage.

The results of an experiment made in 1910 to ascertain the effect
of plowing on pupse is given in Table VIII. Larvae were placed in
large field cages. Wlien the greater number had pupated, one of
the cages was removed temporarily and the land plowed.

TableA'III. — Effect of plowing on pupal stage of the tobacco Crambus.

Cage No.

Number
of larvae.

Collected.

Moth.s emerged.

Num- Per
ber. cent.

1

200
200

June: Second and third week...
. ..do

July: Third and fourth week..
do

84 42

2 (.check) . . .

lis 59

20 lU'l.I.lCTTX T8, r. 6. DEl'AKTMEXT OF A(5RICri.TURE.

Pupation ttikos pbu-o n( an aviM-ao;o dopth of 1 \ inchos. 'Pli(> pupal
cells are iVanilr antl easily hroktMi up by i^lowinu' ov iliskinii'. Many
of (ho pupa> iwc (iet^ply hui'icHJ hy plowiuii" and (lu> moths are unaMo
to ri^ach tlu^ surface.

The satisfactory results folUnvinu" suuuuim' lrt\atnuMil of land,
\vh(>tluM- or not (OwpiMis ov oth(M' similar crops art> urown. are mainly
du(> to tin' fact tiujt c»)nditi(His are made unfavorable for the deposi-
tion of eggs by the moths and foi' the gi-o\vth of newly hatcheil larva\

lAl.l, AMI \Vl\rKK I'KKATMKNT Ol' LAND.

Puring Sej)tem!)er. HH)*>. two cultural cxjierimenls were begun in
Appomattox. Va.. to ascertain the elVect of fall and wii.ier Treatment
of land already infested with Crandms larva\

The fudd selected on the d. F. Purdum farm contained li\ t> i)lats
i»f one-half aci'e each. In this e\[>eriment (experiment \) fall and
winter ])reparation o( the tobai'co haul gave tlecidetlly beneficial
results. 'riu> held had been in ])asture previous to ])l(nving, but the
growth of weetls was uoi so rank as on the laml useil in ex])eriment B.
The following were the results obtained in each of the plats:

Plat Xo. 1. — Gnnmd plowed durinu soinnid week in December. 1909. Thoroughly
disked during lirst week in.lauuary, 19U>. Tobacco planted during last week in May.
Number of plants. 2.'J00. Xumber replanted. S9. Per cent injured, 44-.

PUit So. :J. — Land plowed during lust week in January, 1910. Disked during
second week in February. Tobacco planted during last week in May. Niunber of
plants. 2. ooO. Xumber of plants reset. Uio. Per cent injured. 7 + ■

Plat Xo. iS'. — Land plowed during last week in February, 1910. Disked during third
week in March. Tobacco planted during last week in May. Xumber of plants. 2.280.
Xumber of plants reset, 138. Per cent injured, G-f.

Plot Xo. 4- — Land plowed during third week in March. 1910. Disked dming third
week in April. Tobacco planted during last week in May. Number of plants. 2,214.
Xumber of plants reset, 251. Per cent injured. 11-|-.

Plat Xo. 5 {chirk- plat). — Land plowed during third week in April. Prepared for
planting dvu'ing last week in May. Tobacco planted diu'ing last week in May. Xum-
ber of plants. 2.225. Xumber reset, 375. Per cent injured. 17-|-.

Ti^bacco ii\ all ]dats was re})huited twice. A good stand of phuits
(about OS per cent) was secured by July 4. After duly 4 there was
but shght injury from the worms. The land had been heavily
fertilizeil, and the tobacco made aline growth.

The second tobacco cultural experiment was conducted on the farm
i>f Mr. J. ]\. Ilorsley (experiment B), in Appomattox County, Va.
Four ]>lats, each lontaiiting 1 acre, were inclinleil in the experiment.
Two chctdv phits, one at each end of the experimental plats, were
used. Kach of these contained 1 acre. The growth of weeds was
heavy, stickweed, daisy, and Inu-khorn plantain being abundant.

In tltis test beneficial residts from fall ami winter ])linving were not
so conclusive as in the experiment on the Purdum farm (e-^ptM'iment

THE SO-CALIJ;0 TOBACCO WIREWOHM IN VIRGINIA.

21

A). On f)lat No. 1 llu! viUtci of mowirijr arxi hiirriir)(^ the wfieds aftfir
the c^gH had hatched was noted.

Plat No. 1. — Weeds mowed and Imrned diiririf^ third wff;k in September, VMV.i.
The land wrh not, di.sturhed until the f^ronnd wa.s 7>repared for pianlin<,', durinj^ the
third week in May. Number of plant,s in plat, 4,400. .\umher of planti) res^it, 01 0.
Per rent injured, l.'?.8 + . Tobacco replanted twice.

Plat No. 2. Ground plowed during la.st week in September, l!JO!i. in .March,
April, and May it was disked and harrowed at frequent intervats, no vegetation being
allowefl to grow before the t/)bacco was planted, in order, if possible, t/O starve out the
hibernating larvae. Number of plants, 4,400. Number replanted, 415. Per cent
injured, 9.4-(-.

Plat No. 3. — Land plowed during .second week in .March and not disturbed until
just before planting. Number of plants, 4,400. Number of plants re.set, 410. Per
cent injured, {).?>-{-.

Plat No. 4. — Land plowed during third week in December, 1909. Nothing further
done tf; it until 7)repared for planting during last week in May, 1910. Number of
plants, 4,400. Number replanted, 540. Per cent injured, 12.2-j-.

The resiihs of these experiments are shown also in Table IX.
All plats were replanted twice. A good stand of 98 per cent was
secured by July 5.

Tablk IX,

-Effects of fall and riinter treatmerd on injury by the toharro drambus
in 1009 and 1910.

Exper-
iment
No.

Al

A2

A. '5

A4

A. 5
Bl

B2
B.3
B4
B5

Preliminary treat-
ment.

Plowed .

...Ao..

rlo..

do..

do

Weeds mowed and
t>umed.

Plowed

do

do

do

Time of treatment.

Later treat ment .

Tim<*.

Second week of December, 1909.

First week of January, 1910

Last week of February

Third week of March

Third week of April

Third week of September, 1909.

Last week of September..

Second week of March

Third week of December.
First week of April

Thoroughly disked.

Disked.

do.

do.

First week of

January,

1910.
Second week of

Februfiry.
Third week of

.March.
Third week of

April.

[Disked and har- 1 «,,„!, .,,;,
rowed at fre- l^^f^^ ^P"'-
qiient intervals. J ■*^^^-

Disked First week of

I May.

Kxper-

iment

No.

Planlerl toljacco.

Number
ofplants.

Number
reset.

Per cent,
injury.

Al
A2
A3
A 4
A. 5
Bl
B2
B3
B4
B5

Last week of May . .

do

do

do

do

Third week of May.

do

do

do

do

2,200
2,.3.'50
2,280
2,214
2,22.1
4,4fX)
4,400
4,400
4,400
8,800

89

m>

1.38
2.51
37.i
RIO

41.7

410

.540

1,218

n
11

17

13.8
9.4
9.3

12.2

1.3.9

In the season of 1910-11 another series of cultural experiments was
conducted on the J, F. Purdum farm, in Appomattox County, Va
The land previous to preparation for tobacco was in meadow

22 BULLETIN 78, U. S. DEPARTMENT OF AGRICULTURE.

(timothy, herd's grass, and clovei) which liad been quite weedy.
Natural food pLants of the tobacco Crambus were abundant. This
series was made for the purpose of ascertaining the effect on the
tobacco Crambus of preparation of weedy land at different times
during the fall and winter as compared with spring preparation of
land. Tlie field was divided into 6 plats containing one-half acre
each. Tobacco was planted in all plats on the same date. The
amount of fertilizer applied to each plat was the same.

In plat No. 1 the land was plowed September 6, 1910, and fallowed
February 25, 1911. It was harrowed and disked on April 3, April 10,
April 20, and May 3. The stand of tobacco was nearly perfect; after
the first planting except along one end of the plat. The percentage
of a stand secured was 95.4. In the preparation of this plat it will be
noticed that the land w^as plowed during the first part of September,
a time just after the larvse had hatched.

Plat No. 2 was plowed December 8, 1910, and fallowed February 28,
1911. It was harrowed and disked on April 3, April 10, April 20, and
May 3. Tobacco was replanted once. About 85 per cent of a stand
was secured at the first planting.

Plat No. 3 was plowed January 8, 1911, and fallowed or replowed
February 28, 1911. It was harrowed and disked on April 3, 10, and 20
and May 3. Tobacco was replanted once. About 85 per cent of a
stand was secured at the first planting.

In plat No. 4 the land was plowed on Apiil 11. No further treat-
ment was given until the third week in May, when the land was
prepared and bedded for planting. Tlie tobacco was replanted three
times. About 51 per cent of a stand was secured at the first planting.

In plat No. 5 the land was plowed on January 18, 1911, and disked
May 15. Tobacco was replanted three times. About 70 per cent
of a stand was secured at the first planting.

Plat No. 6 served as a check plat. The land was plowed during
the third week in April, and was prepared for planting on May 15.
Tobacco was replanted three times. About 55 per cent of a stand was
secured after the first planting.

• Further cultural experiments were conducted on the S. L. Ferguson
farm, in Appomattox County, Va., in the season of 1911-12. -This
series was made to ascertain the effect of deep winter plowing and
subsoiling of pasture land infested by the Crambus. Tlie field of
which the experimental plats were a part had been in sod for a number
of years and was used as pasture land. The general conditions for
the experiment were ideal. The oxeye daisy, buckhorn plantain,
and stickweed were abundant. There was not a rank growth of
weeds, however, as the field had been quite closely pastured. The
field was deeply plowed in February, a subsoil plow following the
turning plow, and the clay subsoil was broken up to a depth of several

THE SO-CALLED TOBACCO WIRE WORM IN VIRGINIA. 23

inches. The tobacco in all plats was planted at the same time. The
kind and amoimt of fertilizer applied was the same in all plats, and
after the fu'st cultivation all plats received the same treatment. The
land was divided into 3 plats of 2 acres each and 1 plat containing
one-half acre. Below are given the details of each experiment and
the results obtained.

Plat No. 1 contained 2 acres. It was deeply plowed and subsoiled
in February, 1911. The land was thoroughly disked and harrowed at
frequent intervals during March, April, and May and kept almost
entirely free from weed growth until tobacco was planted. The stand
of tobacco was practically perfect. Only an occasional plat could be
found which showed damage from Crambus larvae.

Plat No. 2 contained 2 acres. The land was deeply plowed and
subsoiled in February, 1911, and was not disturbed until prepared for
planting in May, when it was deeply disked, harrowed, and bedded
just before planting. Ninety-four per cent of a stand was secured at
the first planting. The plat was reset once.

Plat No. 3 contained one-half acre. The land was plowed and sul>
soiled in February, 1911, as in plats Nos. 1 and 2. The land was not
disturbed until prepared for planting as in plat No. 2. Weeds and
grass were allowed to grow after planting. The middle of the row
was not disturbed until after the first cultivation, in order to provide
natural food for the Crambus larvae, so that they would not be forced
to attack tlie tobacco plants. The infestation of this plat was not
heavy enough, so that the effect of tliis treatment, which is said to be
practicable under certain conditions, could be accurately determined.
The stand of tobacco secured at the first planting was 96 per cent. A
few larvfe were found in the weeds left in the middle of the row.

Plat No. 4 was used as a check. The land was plowed and ])ro-
pared for planting just before the tobacco was set out. The weed
growth and general conditions were similar to those in plats Nos. 1 ,
2, and 3. The stand secured at first planting was 86 per cent. The
tobacco was replanted twice. In land adjoining this tract which had
been under clean cultivation during the previous summer and where
there was no weed growth, about 98 per cent of a stand of tobacco
was secured at tlie first planting. Tliis land liad l)een prepared for
planting in practically tlio same manner a^ in the check plat. No. 4.

CHEMICAL SPRAYS FOR WEED DESTRUCTION.

Certain chemical sprays, such as iron-sulphate (copperas) solution,
copper-sulphate (bluestone) solution, and common-salt solution, are
frequently used for eradicating weeds and under certain conditions
have been found very effective. The success of this method of erad-
icating such weeds as oxeye daisy and wild mustard from grain and
pasture fields without injury to the grains or grasses depends largely

24 BULLETIN 78, U. S. DEPARTMENT OF AGRICULTURE.

ou the fact that cereals and grasses are narrow-leaved plants with a
single seed leaf, whereas the weeds injured are broad-leaved plants
with two seed leaves. Spraying with a solution of iron sulphate at a
strength of 1 pound to one-half gallon of water was found to be fairly
effective on the oxeye daisy in a test made at Appomattox, Va.
While spra>ang may be practical where certain weeds in grain fields
are to be eradicated, it is hardly a suitable remedy under most con-
ditions in tobacco-growing sections, except possibly where small
patches of weeds are to be destroyed. Chemical sprays have been
found to be more effective when applied on warm bright days when
the plants are dry. Immediately after weeds have been cut oft' close
to the ground an application of salt, kerosene, crude oil, or acid
solutions will often be found effective. In eradicating weeds from
pastures the salt solution is preferable, as copper-sulphate solution is
poisonous to stock.

LIMING.

Aside from improving the mechanical and chemical condition of
many soils, liming will be found to aid greatly in the control of several
of the weed pests which have been found to be the natural or favorite
food plants of the tobacco Crambus. Control of weed pests may be
accomphshed by making soil conditions less favorable for the weeds, or
by making conditions more favorable to the cultivated crop. Many
weed pests, like other plants, require for their best development certain
soil conditions; and they are excessively abundant in certain locali-
ties because soil conditions are peculiarly favorable to their growth,
or because conditions are less suited to more desirable plants wliich
under favorable soil conditions would crowd them out. A change in
the condition of the soil, brought about by the use of lime, will often
bring about a marked effect in checking or preventing the growth of
a weed pest, and at the same time make the soil better adapted to the
growth of certain cultivated crops such as clover.

The sheep sorrel ^ {Rumex acetosella) , on which newly hatched
Crambus larvae frequently feed, thrives in acid soil. Where lime had
been apphed to certain fields, and to some of the State experiment
station plats in Appomattox County, Va., the sheep sorrel was
practically eradicated or at least checked by the better growth of the
clover. Plantain, daisy, and aster (stickweed), all food plants of
the worms, are weeds which flourish in acid or worn-out soils. In all
cases where data have been secured, the use of lime has resulted in a
marked decrease in the abundance of these weeds. Most soils in the
Piedmont region of the Eastern States are greatly benefited by lime,
and its use has in many instances resulted in markedly increased yields
of tobacco. In plats of alfalfa at the Appomattox experiment station

^Attempts to rear larvse iii cages containing only sheep sorrel were not successful.

THE SO-CALLED TOBACCO WIREWORM IN VIRCilNIA. 25

there was scarcely any plantain (Plantago lanceolata) after a heavy
application of lime had been made, and there was an excellent crop
of alfalfa. In the unlimed check plats plantain nearly covered the
ground, and there was a very poor growth of alfalfa.

Increased fertility of the soil may also aid in the extermination of a
weed, as was noticed where heavy applications of acid phosphate had
been made to meadow land on which there was a heavy growth of
the oxeye daisy. The year following the application of the acid
phosphate but few plants of the daisy could be seen. In this manner
certain weeds may often be crowded out by grasses or clovers which
are enabled to make better growth owing to greater fertility.

The experience of the best tobacco growers has shown that intensive
culture gives largest profits, and no expense or trouble should be
spared m puttmg the ground in the best possible condition in every
respect before the crop is planted. By commencing the preparation
of weedy land the year before it comes in corn or tobacco, an excellent
opportunity is afforded to apply lime. Such land can often be con-
veniently plowed in whiter and during spring or early summer, and
easily be put in condition for such crops as crimson clover, cowpeas,
etc., which may be profitably followed by tobacco or corn the succeed-
ing year.

FERTILIZERS.

From observations of tobacco fields during the seasons of 1910
and 1911 it is evident that where the land receives heavy apphcations
of nitrogenous fertilizers the damage from the worms is not so great
as where light applications are made. Just as many plants are
attacked by the worms, but vigorous and rapidly growing plants
are more apt to recover from injury. This was very noticeable in the
fertilizer test plats of the Virginia experiment station at Appomattox
in 1910.

INSECTICIDES AND REPELLENTS.

The following insecticides and repellents were tested: Arsenate of
lead, Paris green, tobacco extract, nicotine sulphate, tobacco dust,
kerosene, kainit, and calcium cyanamid. In no instance were results
secured which would indicate that the substances tested were of much
practical value in combating the tobacco Crambus. The following
field notes give details of some of the experiments:

ARSENATE OF LEAD.

In experiment A, with powdered arsenate of lead, 1^ ounces of the poison to 2^
gallons of water was used. Two hundred plants were treated, the entire plant being
dipped into the solution. The plants were set in land which had been prepared a
few days before. The field had been weedy and the worms were numerous. Two
hundred untreated plants were kept as a check. On examining the plants five days
later 22 injured plants were found in the poisoned plat and 36 injured plants in the

26 BULLETIN 78, U. S. DEPARTMENT OF AGRICULTURE.

check plat. Three live larvse which had Uinnelled .in the stalks and were apparently
uninjured were found in plants in the poisoned plat. All treated plants had lived,
but were not as vigorous in appearance as those not treated.

In experiment B, with arsenate of lead paste, the poison was used at the rate of
2 ounces to 2h gallons of water. The tops only were dii)pod. One hundred plants
were treated and 100 left untreated. The plants were examined five days after trans-
planting. There had apparently been some injury from the poison, as th'^ plants
were in best condition in the untreated plat, while those treated were somewhat
stunted or dwarfed. Eight injured plants were found in the poisoned plat. Five
plants were found injured in the untreated plat. ,

PARIS GREEN.

Paris green at the rate of one-fourth ounce to 3 gallons of water was used on 100
tobacco plants, and an adjoining row kept as a check. The entire plant was dipped
in each case, and the plants set out at once. The field was weedy. It had been
recently plowed and Crambus larvae were numerous. A light rain fell a few hours
after the plants were set. After eight days the plants were examined. Twenty-one
plants were injured by worms in the poisoned row and 26 in the unpoisoned row.
There had been some injury to the plants dipped in the poison solution, as the un-
poisoned plants had a more vigorous start. In some instances plants in the poisoned
row were only slightly eaten, thus indicating that the poison had acted as a repellent
or had poisoned the worm before the plant had been badly eaten.

TOBACCO EXTRACT.

One row of tobacco plants in a field was sprayed with a 500-to-l solution of tobacco
extract, 320 plants in all being treated. The solution was applied with a compressed-
air bucket sprayer. The substance did not prove effective in preventing injury.
On June 6, five days after the mixture was applied, the plants were examined.
Fourteen plants were found injured by worms in the sprayed row and 11 injured
plants were found in the unsprayed row adjoining.

NICOTINE SULPHATE.

A 1,000-tu-l solution of nicotine sulphate was sprayed on 300 plants as in the fore-
going experiment, and an adjoining row used as a check. The plants were examined
four days after spraying. Eight plants had been attacked by worms in the sprayed
row and 13 plants in the check row. W^iile the foregoing substances did not prove of
much value in preventing injury from the worms, they seemed to repel flea-beetles,
as very few could be found on the treated plants whereas they were comparatively
abundant on the unsprayed plants.

TOBACCO DUST.

Tobacco dust was scattered about tobacco plants directly after planting. One row
containing 300 plants was used for the test and an adjoining row with the same number
as a check. Eighteen plants were found injured by worms in the treated row. Few
plants were found that were injured below the surface of the ground, the worm having
entered the plant at the "bud " or terminal leaf in most cases. Sixteen injured plants
were found in the row where the dust had not been applied. More of these plants
had been injured below the surface of the soil than where dust had been applied, this
indicating that the dust may possibly have some value as a repellent.

KEROSE.NE.

In the first experiment with kerosene the plants were dipped in a weak solution
of kerosene emulsion and were set out on June 15. Only 30 plants were used in the
test. None of these, when examined five days later, was found infested. There was
apparently no injury to the plants from the kerosene. Two infested plants were

THE SO-CALLED TOBACCO WIREWOKM IN VIRGINIA. 27

found in the check row of 30 plants. The number of plants treated was not large
enough to make this test of much value.

In the second experiment 'kerosene was mixed with sand and a small amount
sprinkled around 100 tobacco plants. One hundred plants in an adjoining row were
used as a check. A light rain fell a few hours after the sand was applied. On June
IS, eight days after treatment, the plants were examined. Sixteen were found
injured in the treated row and 22 in the untreated row.

KAINIT.

In one experiment kainit was mixed with the soil in the hill before planting. Too
large a quantity of the kainit was used in the test, as a consideralsle number of plants
failed to grow. One hundred tobacco plants were pat out in soil mixed with the
kainit, and 100 plants in an adjoining row were left for a check. A number of infested
plants were found where the kainit had been used, the substance evidently not being
of mucli value as a preventive, as the worms often enter the plant at the "bud " or
whorl of terminal leaves.

TURPENTINE.

In certain sections of Tennessee and Kentucky turpentine is said to have been used
as a repellent for Crambus larvte and cutworms. Before planting, the roots of the
tobacco plants are dipped in water in which a small quantity of turpentine has been
stirred.

A test on 1 acre of tobacco was made by Mr. Charles Armistead, of Clarksville, Tenn.,
and the field kept under observation by the writer. Entirely negative results were
obtained. The following are details of the experiment: The tobacco was on weedy
land containing an abundance of wliite top {Erigeron annuus) and plantain. The
first planting was entirely destroyed. When the tobacco was replanted turpentine
was used at the rate of 1 teaspoonful to 1 gallon of water, the roots of the plants being
dipped in the mixture. On June 27, two weeks after planting, the toljacco was
examined. Worms were still very numerous. Over 80 per cent of the plants had
been entirely destroyed, in both treated and check plats. There seemed no apparent
difference in infestation and damage lietween tlie treated tobacco and that on which
no turpentine had been applied.

CALCIUM CYANAMID.

Calcium cyanamid (lime nitrogen) is said to have a repellent or poisonous effect
upon insects, and on the suggestion of ]VIr. E. H. Mathewson, Crop Technologist of the
Bureau of Plant Industry, 'Mr. B. G. Anderson, superintendent of the Tobacco Experi-
ment Station at Appomattox, Va., and the writer made a test of the material during
] 911, using the calcium cyanamid at the rate of 300 pounds per acre. The land selected
had not been cultivated for several years. There was a rank growth of buckliorn
plantain, oxeye daisy, and stickweed, and Crambus larvae were exceedingly numer-
ous, making conditions ideal for the test. The plat, containing one-twentieth or an
acre, was divided into series of two rows each. The calcium cyanamid was used on
two rows and the next two rows were kept as a check. On the treated rows com-
mercial fertilizer at the following rate per acre was used:

Pounds.

Calcium cyanamid 300

Acid phosphate (JOO

Sulphate of potasli 1 00

On the check rows the fertilizer used (rate per acre) was as follows;

I'ouuds.

16 per cent blood 300

Acid phosphate COO

Sulphate of potash 100

28 BULLETIN 78, U, S. DEPARTMENT OF ACRICULTURE".

The calcium cyanamid analyzed about 17 per cent ammonia, this making the
amount of plant food in the treated and check rows practically the same. The fer-
tilizer was applied 14 days before the plants were set, as calcium cyanainid has the
effect of stunting tt)bacco plants if applied directly Ijefore planting. It was applied
to the rows with a drill, and thoroughly mixed with the soil by running a cultivator
over the rows. The plants were set on June 8. By June 30 the plants in Ijoth treated
and check rows had been almost completely destroyed by the Crambus larva^, there
being no indications of any beneficial effect from tlie calcium cyanamid in preventing
injiny. The tobacco was not replanted.

LE.\1) .\RSE\.\TE AND l'.\ lUS GliKKN USED WITH COAL TAR O.N SKEI) CORN To PREVENT
INJURY BY CRAMBUS I.ARV.E.

Experiments in the use of arsenate of lead and Paris green witli coal tar on seed
corn to prevent injury by Cramlius larAiv were conducted in 1910 on the J. F. Pur-
dum farm.

In experiment A, arsenate of lead in paste form was used at the rate of 1 ounce to
1 gallon of water. One peck of shelled seed corn was allowed to soak in the solution
about 10 minutes and dried by mixing with fertilizer (acid phosphate). A very little
coal tar (about a tablespoonful) was then poured on the corn, which was thoroughly
stirred until a thin coating of the tar covered each kernel. Fertilizer was then used to
dry the tar. With an ordinary jjlanter one-half acre was planted in seed prepared as
just described. Fully one-third of the corn failed to germinate, possibly owing t<j
exclusion of moisture from the seed by the tar, as the weather was dry. No benefit
in preventing injury by the worms seemed to result. In the check plat the stand
of corn was practically perfect. On June 16, four weeks after planting, a count was
made in the treated and check plats of hills of corn showing Crambus injury. Eleven
per cent of the hills showed injury in the treated plat and 13 per cent in the check
plat.

In experiment B, 1 ounce of Paris green was used to 1 peck of shelled seed corn.
A small amount of tar (about one tablespoonful) was poured over the corn, which
was thoroughly stirred until a thin coating of tar covered each kernel. The corn
was then dried l^iy mixing with fertilizer to which Paris green had been added. One-
half acre was planted with seed prepared in this manner. About one-fifth of the
seed failed to grow. In the check plat tlie stand was practically perfect.

A count of hills of corn shomng Crambus injury, made on June 16, tour weeks
after planting, showed the results of the treatment to l)e as follows: Injury in treated
plat, 11 per cent; injury in check plat, 9.5 per cent.

SUMMARY OF ECONOMIC CONTROL.

( 1) The eggs of the tobacco Crambus are deposited in weedy fields
during July and August. They hatch in a few days. The larvae
remain over winter in the soil and complete their growth during
June and Jul}^ They are in their most active feeding stage at the
time tobacco or corn is planted.

(2) Injury to tobacco or corn occurs when these crops are planted
on land which was weedy during the previous year. Crops planted
on land which has been under clean cultivation are immune from
injury.

(3) The weeds which have been found to be the more common
natural food plants of the worms are the buckhorn plantain, oxeye
daisy, stickweed, and whitetop. The presence of these weeds in
meadows accounts for injury to tobacco or corn when planted on sod.

THE SO-CALLED TOBACCO WIREWORM IN VIRGINIA. 29

(4) The worms when once estabhshed in land where their natural
food plants are abundant have been found difficult to control.

(5) Various insecticides and repellents have been tested, but
without satisfactory results.

(6) Fall or winter plowing has been found to reduce injury, but
is only partially effective, as some of the weeds remain alive and
furnish food for the larvae until the tobacco or corn is planted.

(7) Damage is best prevented by crop rotations, or by cultural
methods that prevent growth of the weeds which are food plants of
the worms, thus making conditions unfavorable for egg deposition by
the moths the summer hefore tobacco or corn is 'planted. Summer
plomng, thorough preparation of weedy land, and the growing of
crops of cowpeas or crimson clover, preferably cowpeas, the year
before crops subject to injury are planted, have been found to be the
most satisfactory and practical means of control.

BIBLIOGRAPHY.

1860. Clemens, Brackenridge. Contributions to American lepidopterology. No.
5. Proc. Acad. Nat. Sci. Phila. for 1860, p. 203-221, June, 1860.
The original description of Crambus caliginosellus, p. 204.

1880. (trote, A. R. Preliminary list of North American species of Crambus. Canada
Ent., V. 12, no. 4, p. 77-80, Apr., 1880.
Gives habitat, N. Y., p. 79.

1887. Moffat, J. A. Further additions to the list of Canadian microlepidoptera.
Canad. Ent., v. 19, no. 5, p. 88-89, May, 1887.

Specimen of Crambus caliginosellus in collection of Mr. Moffat, Hamilton, Ont., deter-
mined by Femald.

1891. Beckwith, M. H. Notes on a corn crambid. U. S. Dept. Agr., Div. Ent.,
Insect Life, v. 4, no. 1-2, p. 42-43, Oct., 1891.

Brief mention. Dr. J. B. Smith reports insect as injuring corn in New Jersey. Dr. L. O.
Howard reports insect as abundant in Maryland in 1886.

1891. Beckwith, M. H. Notes on a corn crambid. Del. Col. Agr. Exp. Sta., Bui.
14, p. 13-15, fig. 1, Dec, 1891.

Mention of species as injurious to corn in Delaware. Account of feeding habit of larvae.
1894. Felt, E. P. On certain grass-eating insects. Cornell Univ. Agr. Exp. Sta.,
Bui. 64, p. 47-102, 14 pis.. Mar., 1894.

"The sooty crambus," p. 61-62. Brief account of moth; description of eggs and newly
hatched larvae.

1896. Fernald, C. H. The Crambidse of North America. Mass. Agr. Col. Ann.

Rpt. 33 (Pub. Doc. 31), p. 77-165, pis. 6 & A-B, Jan., 1896. "
Redescription of moth, p. 137-138.

1897. Johnson, W. G. Notes on some little-known insects of economic importance.

U. S. Dept. Agr., Div. Ent., Bui., n. s., no. 9, p. 83-85, 1897.
" Crambus caliginosellus," p. 84. Account of injury to com in Maryland.

1898. Johnson, W. G. Report on the San Jose scale in Maryland and remedies for

its suppression and control. Md. Agr. Exp. Sta., Bui. 57, 116 p., 26 figs.,
Aug., 1898.

" Crambus calignosellus," p. 9. Account of injury and feeding habits of larvae.
1898. Johnson, W. G. Notes from Maryland on the principal injurious insects of
the year. U. S. Dept. Agr., Div. Ent., Bui., n. s., no. 17. p. 92-94, 189S.

"The corn crambus," p. 93. Brief mention as destructive in various parts of the State.

30 BULLETIN 78, U. S. DEPARTMEXT OF AGRICULTITRE.

1899. Johnson, W. G. The stalk worm: A new enemy to young tobacco. U. S.

Dept. Ac^r., Div. Ent., Bui., n. s., no. 20, p. 99-102, 1899.

An account of injury to tobacco by C. caliginosellus. States that tobacco growers in
southern Maryland reported injury for last fifteen years, or possibly longer. Recommend.s
system of crop rotation aimed at control.

1900. .loHNSON, W. G. Notes on insects of economic importanc e for 1900. U.S.

Dept. Agr., Div. Ent., Bui., n. s., no. 26, p. 80-84, 1900.

Brief mention of Crambus caliginosellus. Reports insect as destructive to tobacco on
sod lands, p. S3.

1902. Sanderson, E. D. Insects injurious to staple crops. New York, 1902.

"The corn-root webworra ( Cmmbtis caliginosellus Clem.)," p. 130 134. Account of
injury to com and tobacco. Recommendations concerning control.
190;^. Chittenden, F. H. The principal injurious insects in 1902. U. S. Dept.
Agr. Yearbook for 1902, p. 726-733, 1903.

Brief mention of Crambus caliginosellus. One of the most destructive insects to corn in
Delaware in 1902, p. 729.

1907. McNess, G. T., Mathewson, E. H., and Anderson, B. G. The improvement
of fire-cured tobacco. Va. Agr. Exp. Sta., Bui. 166, p. 186-234, May, 1907.
Account of difficulty of securing a satisfactory stand of tobacco in experimental work-
description of injury to plants.

1909. Mathewson, E. H. Iiilensive methods and systematic rotation of crops in

tobacco culture. U. S. Dept. Agr. Yearbook for 1908, p. 403-420 pi 33-37

1909. ' ' '

Mention of tobacco "wireworm" or "stalkworm" and eflect of crop rotation on control
p. 411.

1911. Runner, G. A. Report upon tobacco insect investigations, Va. Polyterh
Inst. Agr. Exp. Sta., Ann. Rpt. for 1909 and 1910, p. 40-43, 1911.

Amount of economic importance of insect, food plants, feeding habits of larvae. Recom
mendations concerning control, p. 41-42.

191 1. Morgan, A. ('. Insect enemies of tobacco in the United States. U. S. Dept.

Agr. Yearbook for 1910, p. 281-296.
Brief mention of tobacco Crambus, p. 291.

1912. Hunter, "W. D. Relation between rotation systems and insect injury in the

South. U. S. Dept. Agr. Yearbook for 1911, p. 201-210, 1912.
Discussion of importance of systems of crop rotation m relation to control.

o

WASHIXOTO.V : UOVEU.V.ME.NJ- I'lt I NTI .NC OFFICE : 1914

BULLETIN OF THE

No. 88

Contribution from the Bureau of Entomology, L. O. Howard, Chief,

April 30, 1914.

THE CONTROL OF THE CODLING MOTH IN THE
PECOS VALLEY IN NEW MEXICO.

By A. L. QuAiNTANCE, in Charge of Deciduous Fruit Insect Investigations.
INTRODUCTION.

For some years complaints have been received by the Bureau of
Entomology from the fruit growers in the Pecos Valley, N. Mex., of
the severe injury to apples and pears by the codling moth (Carpocapsa
pomonella L.). The methods employed m the control of this insect
m other apple-growuig regions have, m the Pecos Valley, been
stated to be there much less efficient, so that a considerable portion
of the crop of fruit has been wormy and unsalable.

The codluig moth should yield as readily to treatment in the Pecos
Valley as eisewliere, though, owmg to favorable clunatic conditions,
it was surmised that it might develop an additional generation. It
was not beheved, however, that the behavior of the insect in that
region was essentially different from its behavior in other sections,
and the lack of satisfactory results from spraymg operations, it was
thought, probably resulted from failure to accomphsh this work m a
thorough and timely manner.

Begmning in the sprmg of 1912 an mvestigation of the codling
moth was undertaken by the Bureau of Entomology, with head-
quarters at RosweU, N. Mex., and Mr. A. G. Hammar, who had had
much experience with this insect at other field stations of the bureau,
was assigned to the work. During that year he was assisted by IMr.
Earl R. Van Leeuwen, and durmg 1913 by ^Ir. L. L. Scott and ^li.
E. W. Geyer. Owing to the unfortunate death of ^Ii\ Hammar there
devolves upon the writer the necessity of preparing for pubhcation,
for the benefit of the Pecos Valley fruit growers, the results of IVir.
Hammar's experiments. The investigations carried out by Mr.
Hammar comprise a thorough inquiry into the life history and habits
of the codling moth in that region, and experiments with sprays in
orchards. The results of the life-history studies wdll be given in
another paper.

Note.— This bulletin describes the codling moth as it affects fruit growing in the Pecos Valley, N. Mex.
It is of interest to fruit growers in the Southwest.

a4853°— 14

2 BULLETIN 88, L^ S. DEPARTMENT OF AGRICULTURE.

The present article deals with results obtained in spraying in 1913.
Work was carried out m two orchards, namely, that of Messrs.
Sherman cS; Jolinson and that of IVIr. Kobert Beers. Unfortunately
the report of results in the latter orchard is not entirely complete, so
that the details of these experiments can not be given. In general,
however, the results obtained in the Beers orchard agree with those
secured in the Sherman & Johnson orchard, and the latter are given
in detail in the followdng pages.

EXPERIMENTS IN THE SHERMAN & JOHNSON ORCHARD.

A portion of the Sherman & Jolinson orchard, about 5 acres in
extent, was selected for sprajdng experiments and was subdivided
into plats, as sho\^^l in figure 1.

The trees were large, and codling-moth conditions were fairly
typical for the valley. Plat I received three applications; Plat II,
four appHcations; and Plat III, five applications of arsenate of lead
spray. Plat IV was left unsprayed throughout the season for pur-
poses of comparison. A good power sprayer was used, capable of
supphang three or four leads of hose, and maintaining a pressure of
200 to 225 pounds. (See fig. 2, showing outfit in operation, and size
of trees used.) Further information concerning the treatments and
the dates of spray appUcations for the respective plats is given in
Table I.

Table I. — Treatments and dates of applications of sprays for codling moth, Sherman &
Johnson orchard, Eos well, N. Mex., 1913.

Dates of appli-
cations.

Plat I (3 applications).

Plat II f 4 applica-
tions).

Plat III (5 applica-
tions).

Plat IV
(unsprayed).

Apr. 24-25

(After falling of
petals. )

May 7-S.

July 14-15.

Aug. 2.

Arsenate of lead, 6
pounds to 200 gal-
lons of water. Bor-
deaux nozzles. 16^
gallons per tree'
225 pounds pres-
sure.

Arsenate of lead, S
pounds to 200 gal-
lons of water. Ver-
morel type nozzles.
13} gallons per tree.
200 pounds pres-
sure.

Arsenate of lead, 8
pounds to 200 gal-
lons of water. Ver-
morel type nozzles.
15j gallons per tree.

Arsenate of lead, 6
iwunds to 200 gal-
lons of water. Bor-
deaux nozzles. 16V
gallons per tree.
225 pounds pres-
sure.

Arsenate of lead, 8
pounds to 200 gal-
lons of water. Ver-
morel type nozzles.
133 gallons per tree.
200 pounds pres-
sure.

Arsenate of lead, 8
pounds to 200 gal-
lons of water. Ver-
morel type nozzles.
15} gallons per tree.

Arsenate of lead, 8
pounds to 200 gal-
lons of water. Ver-
morel t>T)e nozzles.
17J gallons per tiee.

Arsenate of lead, 6
pounds to 200 gal-
lons of water. Bor-
deaux nozzles. Kii
gallons per tree.
225 poimds pros-
sure.

Arsenate of lead, 8
pounds to 200 gal-
lons of water. Vor-
morel type nozzles.
13} gallons per tree.
200 pounds pres-
sure.

Arsenate of lead, 8
pounds to 200 gal-
lons of water. Ver-
morel type nozzles.
15| gallons per tree.

Arsenate of lead, 8
pounds to 200 gal-
lons of water. Ver-
morel type nozzles.
17 J gallons per tree.

Arsenate of lead, 8
pounds to 200 gal-
lons of water. Ver-
morel type nozzles.
9J gallons per tree.

Unsprayed.

Do.

CONTKOL OF THE CODLING MOTH IN NEW MEXICO.

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Fig. 1.— Diagram showing anangement of trees used in codling-moth experiments, Sherman & Johnson
orchard, Roswell, N. Mex. (Original.)

Fig. 2.— Viewin Sherman& Johnson orchard, Roswell, N. Mex. , showing size of trees and power sprayer

in operation. (Original. )

BULLETIN 88^ U. S. DEPARTMENT OF AGRICULTURE.

It will be noted from Table I that the amount of spray used in
all applications was large, and probably considerably in excess of
that used by the average fruit grower in the valley. The amount
of spray applied immediately following the falling of the petals
(April 24-25) exceeded somewhat the amount given in any subsequent
application. It will be noted also that Bordeaux nozzles were used
at this time, whereas m subsequent treatments the so-called eddy
chamber or Vermorel type of nozzle was used, producing a fine cone-
shaped spray.

In Table II are shown the number and percentage of sound fruit
from each of five trees of each plat, as well as the total number and
total percentage of sound and wormy fruit for the five trees of the
respective plats.

Table II. — Number of sound and tvormij apples from each tree of each jilat, Sherman
d- Johnson orchard, Roswell, K. Mex., 1913.

riat and condition of fruit.

Tree 1.

Tree 2.

Tree 3.

Tree 4.

Tree 5.

Total

fruit

for

plat.

Total
per
cent
soimd
fruit.

Plat I.

138
2,918

141
2,022

1.53
3,3S2

179

3,418

152
3,239

760
14,979

Sound

Total

3,056
95.48

2,166
93. 35

3,535
95. 67

3,597
95.02

3,391
95.52

15,745

95. 13

Plat II.

W ormy

Sound.

86
4,271

39

4,086

33
3,378

37
3,344

70
5,504

265
20,583

Total

Per cent sound

4,357
98.02

4,125
99.05

3,411
99.03

3,381
98.90

5,574
98.74

20,848

98.72

Plat III.

Wormy

Sound

51
6,28:J

18
4,479

40
4,494

25
4,618

14
4,442

148
24,316

Total

Per cent sound ...

6,334
99.19

4,497
99.59

4,534
99.12

4,643
99.46

4,456
99.68

24,464

99.39

Plat IV.

Wormy

Soimd

5,308
2,871

2,671
2,349

3,813
2,873

3,486

2,7ti5

3,336
1,958

18,614
12,816

Total

Per oent sound . ,

8,179
35.12

5,020
46.79

6,686
42.97

6,2.51
44.23

5,294
37.03

31,430

40.77

It will be seen that Pint I, which received a total of three applica-
tions of an arsenate of lead spray, gave 95.1.3 per cent sound fruit.
Plat II, with four applications, yielded a somewhat higher quantity
of sound fruit, namely, 98.72 per cent; while from Plat III, which
received five spray applications, 99.39 per cent of the fruit for the
season was sound. Plat IV, which was not sprayed during the
season, shows only 40.77 per cent of the fruit free from codling moth
injury. In determining these results, examinations were made as
to worminess of all the apples produced on the five count trees
throughout the season; that is, the fruit which fell, the fruit which
was picked from the trees in thinning, and tliat picked at harvest time.

CONTROL OF THE CODLING MOTH IN NEW MEXICO. 5

It would appear that with the minimum of three appHcations,
made as shown in Table I, injury from the codling moth in the Pecos
Valley may be reduced to less than 5 per cent of the total crop of
apples produced. For each of the two additional applications an
increase in sound fruit is shown, but probably not in proportion to
the expense involved. It should be borne in mind, however, that in
these experiments appHcations were made with much thoroughness,
and unless the orchardist will do equally as thorough work it will be
better for him to make the additional applications.

PLACES OF ENTRANCE OF FRUIT BY CODLING MOTH LARV^.

Many observations in different parts of the country have shown
that the majority of codling moth larvae normally enter the apple at

Fig. 3.— Showing condition of calyx lobes of Ben Davis apple: a, Two days after falling of petals; b, ten
days after falling of petals. ( Original. )

the calyx end. A careful study of the places of entering sprayed
fruit by larva), whether at calyx, side, or stem, throws much light
on the relative effectiveness of the respective spray applications.
All experiments corroborate the statement that the treatment given
immediately after the falling of the petals is by far the most im-
portant one and that its omission can not be corrected by subsequent
treatments, however thoroughly made.

A study of the behavior of the calyx lobes of the recently set
apples in the Roswell section furnishes evidence of value in timing
spray applications. Ordinarily in the East there is a period of about
10 days following the dropping of apple blossoms during which the

6

BULLETIN 88, U. S. DEPARTMENT OF AGRICULTURE.

calyx lobes remain open, so that the spray may be successfully
directed into the calyx cups. In New Mexico, however, it would
appear that the calyx lobes of the little apples do not draw together
nearly so quickly after the falling of the petals and may remain
open in suitable condition for calyx spraying for a period of from two
to three weeks, var^nng somewhat -with the variety and season.
(Figs. 3 and 4.)

This condition renders it possible to apply the second spray in a
way to supplement the first spray into the calyx cups.

Fig. 4.— Showing condition of calyx lobes of Ben Davis apple: o, 18 days after falling of petals; 6, 30
days after falling of petals. ( Original. )

The effect of spraying in changing the relative proportion of larvae
which succeed in entering the fruit at the calyx, side, and stem is
shown for Plats I to III in Table III. The normal behavior of the
larvae in entering the fruit may be seen by referring to the figures for
Plat IV of this table. It will be noted that on the unsprayed plat
somewhat over one-half (53.72 per cent) of the total larvae for the
season entered the fruit at the calyx end.

Table III. — Number and percentage of codling moth larvae entering fruit at calyx, side,
and stem for Flats I-IV, Sherman & Johnson orchard, RosiceU, N. Mex., 1913.

Tof al larvtE for plat for season en-
tering at—

Plat
I.

Per cent.

Plat
II.

Per cent.

Plat
III.

Percent., ^j(.*

Per cent.

Calyx

19

789
10

2.31

96.45

1.24

17

249

5

6.27

91.88

1 s.";

10
128
10

6.76

86.48
6 76

12, 663
9,622

1 9SS

53 72

Side

40.82

Stem

.<; 4fi

Total

818

100.00

271 HIO on 1 14S

100.00 5:? -wn 1 im.oo

CONTEOL OF THE CODLING MOTH IN NEW MEXICO. 7

This table also shows the destructive influence of sprays in lessening
the actual number of larvse. Thus on Plat I, which received three
sprays, there was a total of 818 larvae for the season, on the five
count trees; on Plat II, which received four sprays, the number of
larvae for the five trees was 271 ; while on Plat III, which received
five sprays, only 1 48 codling moth larvae were found in fruit from the
five "count trees" during the year. The foregoing figures are in
marked contrast with the total number of larviie found in fruit from
the five unsprayed trees, namely, 23,570.

RECOMMENDATIONS BASED ON THE FOREGOING RESULTS.

While the results reported herewith are very clear-cut, the bureau
would not be warranted in formulating definite recommendations
based upon the work thus far carried out in the Pecos VaUey were it
not for the reason that these results substantiate the results obtained
from a large series of spraying experiments against the codling moth
in many parts of the United States. In Table I, showing treatments
and dates of applications, the reader will note that the first appUca-
tions were made with Bordeaux nozzles and the later apphcations
with eddy chamber nozzles. Entomologists of certain Western States
who have experimented with the codhng moth under arid conditions
insist upon the advantage of a coarse spray given at the time imme-
diately following the dropping of the petals. Tests of the compara-
tive value of coarse and fine sprays under eastern conditions show
that there is apparently but Uttle difference as regards the effective-
ness in the control of the insect of a coarse and fine spray. The
RosweU experiments did not include a comparison of coarse and fine
sprays and no specific information can be furnished on this point,
and it would appear safer for the orchardist to follow the methods
used by Mr. Hammar until further information is obtained. It ■s\'ill
also be noted that spraying was done under high pump pressure.
This should not be construed to mean that effective work in the con-
trol of the codling moth can not be accompUshed except by use of
power outfits working at high pressure. Very good results have been
obtained fi-om the use of barrel sprayers working at perhaps 100 to
120 pounds pressure.

The prime essential in the control of the codUng moth is that the
treatment given immediately after the faUing of the blossoms shall
be made with great thoroughness, in order to insure the lodgment of
poison in the calyx cup of each and every apple. This result is best
secured by so handUng the spray rods that the spray is directed
downward into the upright clusters of the httle apples. This spray-
ing especially should be made rather deUberately and with great
pains. Frequent examination of sprayed trees should be made to
determine how thoroughly calyx cups are being fiUed with poison.

8 BULLETIN 88, U. S. DEPARTMENT OF AGRICULTURE.

First application. — As soon as the petals have fallen, spray the
trees with arsenate of lead, \ising the poison at the rate of 6 pounds
to 200 gallons of water. Direct the spray straight into the calyx
cups, for which purpose an elbow or crook should be used on the end
of the spray rods. In spraying high trees a tower is indispensable,
as showji in figure 2.

Second application. — About two weeks after the falUng of the petals
spray with arsenate of h'ad at the rate of 8 pounds to 200 gallons of
water. Make an effort to apply this spray before the cal}TC lobes are
more than three-fourths closed, which may be determined by careful
examination in the orchard. (See fig. 3.) Direct this spray, also, as
much as possible straight into the calyx cups, and at the same time
take care to coat the leaves and fruit.

Third application. — Eight or nine weeks after the falling of the
petals spray again mth arsenate of lead at the rate of 8 pounds to 200
gallons of water. In tliis treatment cover the fohage and fruit as
uniformly as possible with the poison.

Subsequent applications. — The three applications specified, if thor-
oughly made, should effectively control the codling moth, as shown
by the results of experiments herewith reported. If these appHca-
tions have not been thoroughly made, and it is seen that the codhng
moth ^v'ill do considerable injury, additional apphcations will doubt-
less be desirable to check the insect as much as possible. Thorough
work, especially in appljdng the first and second apphcations, should
largely obviate the necessity for more than three treatments.

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OF THIS PUBLICATION MAY BE PROCURED FROM

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DIV.INS.ECT^

^ BULLETIN OF THE

No. 90

Contribution from the Bureau of Entomology, L. O. Howard, Chief
May 19, 1914.

THE ROSE APHIS.'

By H. M. Russell,
Entomological Assistant, Truck Crop and Stored Product Insect Invesligations.

INTRODUCTION.

Because of its beauty, and its hardiness as an outdoor })lant, the rose
has long been one of the most ])Opular ornamental flowers in this
country. Yet in spite of the appreciation given it the blossoms and
young foliage are frequently pei-mitted to suffer great damage from
the rose aphis {Macrosiphum rosx L.), whereas a few minutes' atten-
tion on the part of the owner each week would remedy the injury
and greatly increase the beauty of the bloom and foHage. This com-
mon rose pest was fii'st described by Linnaeus ^ in 1735, and since
that time has often been mentioned in systematic works by both
European and American ^vriters. However, the wiiter has seen no
account of it in American entomological publications in which the
hfe history, habits, or control have been treated with anything
approaching completeness. The writer, therefore, in 1910, while sta-
tioned at Los Angeles and under the direction of Dr. F. H. Chitten-
den, began a study of the hfe history and habits of the rose aphis
in its occurrence on the outdoor roses so largely growm in southern
Cahfornia. At a later period the work was carried on to some extent
in Washington, D. C. While this study is stiU incomplete, enough
has been learned to give the rose lover a fair understanding of the
habits of this insect and of the means for controlhng it.

RECENT RECORDS.

During the fall and mnter of 1909 and the spring of 1910 the
writer found the rose aphis attacking roses and causing extensive
damage to the buds and blossoms throughout the city and in the
vicinity of Los Angeles. On October 21, 1909, when firet observed.

' This bulletin is of interest to rose growers everywhere.

2 Linnaeus, C., Systema Natur., ed. 12, vol. 1, pt. 2, p. 734, 1767.

2 BULLETIN 90, U. S. DEPARTMENT OF AGRICULTURE.

this insect had become quite conmion, and many of the buds were
covered mth the females and young. Examination of surrounding
locaHties disclosed the same conditions of infestation. The aphides
increased rapidly until the cold weather in December checked,
although it did not entirely stop, their reproduction and growth. In
January, warmer weather again prevaiUng, the rosebushes began to
grow rai)idly, and the rose aphis became very abundant on the tender
stems and buds. It continued abundant and developed rapidly dur-
ing the months of February and March, although syrphus-fly larvae
devoured thousands. Early in April, however, there occurred sev-
eral very warm days when the temperature rose to 100° or 101° F.,
and immediately the numbere of aphides were greatly reduced.
Afterwards the aphis occurred scatteringly on the roses and caused
very httle damage. This was due in part to extreme heat and the
work of parasitic and predaceous enemies, and to the fact that in
June the roses became more or less dormant and ceased active
growth for some weeks. By the middle of August the rosebushes
had resumed active growth, and this insect again began to increase
rapidly and to cause damage, continuing to midtiply and injure the
roses until October 1, 1910, when observations ceased.

At Washington, D. C, during October and November, 1912, this
aphis was very abundant and injurious to roses grown in the yards
and gardens of the city. But by November 29 only a few aphides
remained on the plants, although these persisted as late as Decem-
ber 16.

DESCRIPTION.!

The rose aphis occurs in two forms, one in which the body is of a
pinkish color and the other in which the pink is replaced by bright
gi'oen. Both forms may be present on the same bush or twig, and in
some cases aU on one bush may be green and aU on another near it
pink. It would appear from the writer's observations that the green
aphides are much more abundant during the cooler months than the
pink forms.

The winged female (fig. 1, a) has a pear-shaped body which in one
form is pinkish and in the other bright green. The thorax is largely
black, apparently deeper black in the green form, and there is a row
of black spots on either side of the abdomen. These colors may vary
shghtly in shade. The antennae, cornicles, ends of femora, and the
tarsi are black, while the other parts of the legs are whitish. In both
pink and green forms, however, the head may be entirely black, and
the black antennae and cornicles may be hyahne at the tips. The

1 Another aphis commonly foimd on the rose is known as the small green rose aphis ( Myzus rosarum
Walk.), but this can be distinguished by its smaller size and by the fact that it has only a green form.
This species is shown in figure 2, in both winged state (o) and wingless state (6) with many details of struc-
ture. This aphis will yield to the same treatments as the common rose aphis.

THE ROSE APHIS. 6

eyes are dark red, the cauda is yellowish, and the veins of the wings
are light yellow. The legs, antennae, and cornicles are very long and
slender, the antennae longer than the body. The length of -the body
is about one-twelfth of an inch (2.5 mm.) from the front to the tip of
the cauda and the length of wing about one-sixth of an inch (4.2 mm.).

Fig. 1. — The rose aphis (^Macrosiphum rosx): a, Winged viviparoiis female; 6, wingless viviparous female;
c, e, g, third antennal article, cornicle, and style, respectively, of winged female; d,f, h, same of wingless
female. Greatly enlarged. (After Essig.)

In the wingless female, also (fig. 1, h), the body is pear shaped,
more or less blunted at the posterior end, and pinldsh or bright green
in color. The eyes are red. The antennae are as long as the body
and very Hght green. The cornicles and legs are long and slender
and hght green. The length of the body is about one-twelfth of an
inch (2.5 mm.).

4 BULLETIN 90, U. S. DEPARTMENT OF AGRICULTURE.

DISTRIBUTION.

The rose a])his is distributed over the entire United States, having
been rccorilcd from Massachusetts, New Jcrse} , IlUnois, Iowa, Minne-
sota, Colorado, and CaUfornia. It also occurs in Europe, from which
country it was first desciibed.

The WTiter has collected it in southern California on all the
commoner varieties of roses growing outdoors and has also taken it,
in 1913, in Connecticut, Maryland, the District of Columbia, and
Virjrinia.

Fig. 2.— The small green rose apliis ( yfijzus rosarum): a, Winged viviparous female; b, wingless viviparous
female; 1, 2, antcnnal articles of winged female; S, cornicle of same; 4, style of same; 5, third antcnnal
article of same; C, style of wingless female; 7, ,9, front and antenna of same; JO, cornicle of same; 5, process
of sixth aniennal article of same. Greatly enlarged. (After Essig.)

CHARACTER OF INJURY.

This insect, like all aphides or plant-hce, obtains its food by suction.
The slender beak with which it is furnished is inserted into the plant
attacked, and through tliis the plant juices are taken np. The rose
aphis in feeding chooses the tender and gro^nng shoots and flower
buds or the young unfolding leaves, and by feeding in large numbers
checks the growth, the leaves and flowers being curled or distorted
and prevented from attaining their perfect form. (Pis. I, II.)

Bui. 90, U. S. Dept. of Agriculture.

Plate 1.

Rose Buds Showing Injury by the Rose Aphis (Macrosiphum rosae). Enlarged.

(Original.)

Bui. 90, U. S. Dept. of Agriculture.

Plate II.

THE EOSE APHIS. 5

Because of the feeding of this rapidly reproducing insect, the flowers
may be largely spoiled for decoration, or, since the rose aphis, like
all aphides, secretes a sweet sticky hquid called honeydew, the appear-
ance of the foliage may be ruined because of the sooty mold that
develops where this honeydew has collected.

HABITS.

About the time the wingless females become ready to reproduce
they leave the parent colony and crawl or migrate to various parts
of the rosebush. Upon finding a growing twig or bud, the female
settles down with the head pointed toward the ground and begins
to feed. In a day or two she begins to give birth to young, wliich
ordinarily range themselves close together around the tender bud
or stem behind the adult, and A^dth the heads all pointing downward
begm feeding. (PI. II.) As the stem or bud becomes crowded
many move out until the flower itself is covered with them. As the
aphides continue feeding a large amount of honeydew is produced
which falls to the leaves beneath, causing a disagreeable stickiness
on the leaf, wliich either becomes covered with dust or black from
sooty mold.

A very slight jar causes the aphides to let go with one pair of legs,
and aU begin to twitch from side to side on the remaining four legs
until quiet is restored, while a severe jar causes many to fall to the
ground. A number of the young develop wings, and Vv^hen mature
they fly to other buds and form new colonies.

When the nymph changes to the winged form the sldn splits
along the dorsum and the adult crawls slowly out. When newly
transformed the adult is light reddish or green in color, with antennae,
beak, legs, and cornicles whitish or hyaUne, and the wings, which are
also white in color, appear as little sacks on the back. In about
20 minutes the wings become fully expanded, and two da3^s later the
aphis has the colors of the mature insect.

LIFE mSTORY AND REPRODUCTION IN CALIFORNIA.

In a chmate as mild as that of southern Cahfornia thJs insect
reproduces continuously throughout the year and undoubtedly is
capable of reproducing asexually and viviparously for an extended
period. While under observation it has been found giving birth to
Uving young throughout the entire year, and the writer has been
unable to find eggs during the same period. It ma}' be that in a
climate such as exists in that part of the country, where very cold
weather does not occur and where the roses continue to grow all

6 BULLETIN 90, U. S. DEPARTMENT OF AGRICULTUEE.

\vinter, sexual forms and eggs of tliis species are not produced, at
least until parthenogenetic reproduction causes deterioration.^

In other parts of this country where the winter conditions are more
severe the rose aphis passes the winter in the egg stage. At Wash-
ington, D. C, on November 29, 1912, the writer found a few eggs
of this species laid on the twigs of rosebushes. These small, oval,
shuiing black eggs were fastened to the sides of dormant buds.

Buckton 2 described the eggs as follows:

The eggs are at first yellow, but subsequently they become black by reason of
certain changes shown by Balbiani to result from fecundation. Previous to this time
the outer coats are sufficiently thin and transparent to allow the process of segmentation
to be observed.

Notwithstanding the great size of the ovum the female may carry five or more.
These, however, are not equally large, but are found to vary in bulk as they approxi-
mate maturity and the time for expulsion.

In California during the fall and spring, while the rose shoots are
growing vigorously and producing much tender growth, the rose
aphis reproduces very rapidly. During the summer, however, the
rate of reproduction seems to be much reduced, and, owing to the
attack of natural enemies, this insect does not greatly increase.
In the winter the time of development is lengthened and the rate'
of reproduction is considerably less.

During the months from October, 1909, to March 10, 1910, the
author endeavored to ascertain the number of young produced and
the average rate of reproduction under normal conditions. This
was done by marking rose twigs having a single female and, after
examining them every other day, removing all the young born at that
time. Thus the aphides were exposed to temperature, rain, and
aU other natural conditions wliich might influence them. Under
this method many females were knocked from the bushes and lost,
but as this would occur naturally it demonstrates fairly weU the
average rate of reproduction, if not the maximum, under the condi-
tions most favorable for the adult. These records have all been
included in Table I.

1 B. M. Lelong, in the Report of the State Board of Horticulture for California, for 1889, page 213, states
that " Kyber, in 1815, has had the rose aphis producing young for four years. From his carefully conducted
experiments and from corresponding ones made by other naturalists a law has been educed, which we dare
not destroy, ' that under certain circumstances, a female aphis may without coupling continue propagating
to infinity, provided that the necessary conditions for the development of the young— food and heat — are
not wanting.' "

2 Buckton, G. B., Monogiaph of the British Aphides, vol. 1, p. 107-108, 1875,

THE ROSE APHIS.

Table I. — Reproduction and development of the rose aphis, Macrosiphum rosae, in
southern California, 1909-10.

Date of birth, of female unknown;

gave birtli to first young Oct. 20,

1909: Number of

young.

Oct. 20 4

21 5

22 5

23 7

24 5

25 7

26

n_

Total 33

Average per day 5 V

Date of birth of female unknown;
date of birth of first young un-
known:

Nov.

6
4
2

4
(•)

Total.

IG

Average per day 3+

Female born Nov. 18, 1909; gave
birth to first young Dec. 6, 1909: ^

Doc. 6 1

8 5

10-11 6

12 3

13-14 4

15-16 9

17 2

18-19 3

20-21 6

22-23 5

25 2

28 C)

Total

Date of birth of female unknown;
gave birth to first young Nov.
19,1909: Number of

Nov.

youug.
9

19

20 2

21-22..... 4

23 4

24 2

25 2

26

27

28

29

30

2

(')

Total 22

Average per day 2

46

Average per day 2 J

Date of birth of winged female, red
form, unknown; date of birth of
first young unknown:

Nov. 18 "18

19 3

20 5

21-22 12

23 10

24 __C)_

Total 48

Average per day, about 6

1 Aphis lost.

2 Period from birth to reproduction, 18 days.

3 Aphis dead.

Date of birth of wingless female,
green form, unknown ; gave birth
to first young Nov. 19, 1909:

Nov. 19 2

20 5

21-22 6

23 5

24.
25.
26.

27.

28.

4
3

(?5)
4

Total 29

Average per day 3 +

Wingless female born Nov. 18, 1909;
gave birth to first young Dec. 6,
1909:2

Dec. 7-8 3

8 «

10-11 3

13 7

15-16 7

17 3

18-19 6

20 1

21...' e)

Total 30

Average per day 2

* Up to date.
6 Rain.

Table I.

BULLETIN 90, U. S. DEPARTMENT OF AGRICULTURE.

—Reproduction and development of the rose aphis, Macrosiphurn rosae, in
southern California, 1909-10 — Continued.

Date of birth of female unknown;

gave birth to first young Jan. 3,

1910: Number of

young.

Jan.S 2

Total

Average per day .

2
9
(0

13
3

Winged female, rod form; gave birtli
to first young Mar. 3, 1910:

Mar. 3 5

4 5

5 9

6 5

"Winged female, red form; gave birth
to first young Mar. 3, 1910 — Con-
tinued. Number of

young.

7 5

8 3

9 C)

Total

Average per day .

Mar. 7.

8.

9.

10.

32

5*

5
5

7

Q)

Total 17

Average per day 5|

Two females were observed that produced 30 and 40 young, respec-
tively, after which they died under normal conditions. They pro-
duced young on an average of 2 and 2^ per day for 15 and 20 days,
respectively, during the month of December. Other females observed
durmg the same period, but lost possibly before reproduction was
completed, gave birth to from 15 to 45 young at an average of 3^ per
day. Two females observed in the month of March, however, pro-
duced young at the rate of 5J and 5| a day, showing quite plainly
how the reproduction was accelerated during the prevalence of
warmer temperatures. Two females in October reproduced young
at the rate of 5^ a day for 6 days, or until lost.

From these observations it may be said that this insect is able to
reproduce for at least 20 days during the winter in southern CaUf ornia
and to give birth to as many as 45 young, wliile in the warmer seasons
the number of young is probably greater and the period of reproduc-
tion is considerably shorter. The reproduction experiments were too
few in number to justify making any statements more generalized
than these.

LIFE HISTORY AND REPRODUCTION IN THE GREENHOUSE.

During the fall of 1912 the rose apliis was under the direct observa-
tion of the writer in the insectary greenhouse at Washington, D. C,
and the life cycle was observed for a few individuals.

A wingless female born October 10 matured and gave birth to young
on October 19, or in 9 days. During the next 7 days she gave birth
to 45 young, or an average of 6|- per day.

Aphis lost.

THE EOSE APHIS. 9

Of four other aphides, born on October 10, two became adult and
gave birth to young on October 22, or in 11 days, whUe another
required 12 days, and the fourth 13 days.

Another aphis was born on October 19 and emerged as a winged
female on November 3, reacliing maturity in 15 days. This insect
Uvcd as an adult for 17 days and gave birth to living young for 14 days.
During tliis time she gave birth to 87 young, or an average of 6^^ per
day. During this time the average mean temperature was 67° F.

LIFE CYCLE IN CALIFORNIA.

During the winter months of 1909-10 the life cycle was observed in
California in a number of cases. Aphides born on the 18th of Novem-
ber became adult wingless females and began to reproduce young in
from 15 to 18 days, and in two cases the offspring of these same insects
became mature and began to reproduce in from 18 days for wingless
females to 21 days for winged females. Aphides born November 26
emerged from nymphal skins as winged adults in from 23 to 25 daj^s.
Thus the wingless forms developed in all cases from 7 to 8 days sooner
than winged forms.

This was the maximum life cycle, and during the rest of the year
the growth must have been much faster, but observations were not
made omng to press of other matters.

GENERATIONS.

Taking 25 days as a maximum, this would allow more than 12
generations annually, but with the shorter life cycle required during
the warmer part of the year tliis number must be exceeded by at least
7 or 8 generations. In greenhouses there are probably 25 to 30
generations in a vear.

LONGEVITY.

During the winter these insects are long lived for such dehcate
creatures. One lived under the direct observation of the writer for
40 days and another for 33 days. Probably this is longer than for
the same insect the rest of the year.

NATURAL CONTROL.

RAINS.

In southern California the rainy season extends from about October
1 to May or June. Usually before the rahis set in the weather becomes
cooler, but the rains are not as a rule hard and dashmg, as are those
so fatal to aphides in the East, and this apparently explains their
slight effects as observed on the rose aphis. Undoubtedly some are
washed away and destroyed by rain, but not to the extent occurring
in the East, although reproduction seems to be greatly checked during
a rainstorm. In the East this insect is many times nearly extermi-
nated by a hard, dashing rain.

10 BULLETIN 90, U. S. DEPARTMENT OF A(iKICULTURE.

Durijig the early part of April, 1910, when the aphis was very abun-
dant on the roses throughout the entire city of Los Angeles, three or
four very hot days occurred during which the temperature rose as high
as 100° F., and mthin a day or two thereafter the numbers of this
aphis had become very nmch diminished. After this it did not seem
to occur in large numbers again until about the middle of August.

BIRDS.

On March 19, 1910, the writer, with field glasses, watched a wliite-
crowned sparrow (Zonotrichia leucophrys leucoplirys) on a rosebush^
10 feet away, eating the rose apliides as fast as it could pick them
from the bush. Tliis was continued for fully 10 minutes, during which
time many hundreds must have been eaten, as the plant was ahnost
cleaned up by this bird.

On March 30, 1910, a CaUfornia house finch {Carj^oclacus mexicanu
frontalis) was observed b}^ the WTiter eating this aphis from a rose-
bush for fully 15 minutes.

PARASmC INSECT ENEMIES.

There are many different species of parasitic insect enemies that
attack aphides, and some of these will attack the rose aphis. On
June 13, 1910, many specimens of Macrosiphum rosse, were found
wliich showed signs of parasitism by an undetermined insect. These
apliides were rounded and fastened to the underside of the rose leaves.
The parasite when full grown had killed the host and, cutting its way
out beneath the body, spun a tiay cocoon between it and the leaf.
Unfortunately all of the parasites failed to emerge. While the para-
site was not rare, at least during the past year, it did not seem to
check the rose aphis to any extent.

Epliedrus incompletus Prov., a braconid, was reared by the writer
from this aphis at Washington, D. C, in 1912.

PREDACEOUS INSECTS.

Among the predaceous enemies the larvae of syrphus flies and lady-
birds were observed feeding on the rose apliis, and without a doubt
the most important check to this insect in 1910 was due to the larvae of
syrphus flies. While these did not seem able to clear a plant alto-
gether, still it was many times observed that strong thriving colonies
of 50 to 60 aphides or more would be reduced by these insects in one
or two days to a mere scattering here and there. During the year
1910 five different species of Syrphidse were reared from larvae feeding
on IfacrosipTium rosse. These were Syrplius rihesii L. (fig. 3) , Syrphus
opinator O. S., AUograpta fracta O. S,, Eupeodcs volucris O. S. (fig. 4)
and LasiopMliicus pyrasti L.

THE ROSE APHIS.

11

The adults of all these species seemed to have similar habits.
They flew swiftly from twig to twig and hovered over them in the
bright sunhght, the wings moving with extreme rapidity, always with
a distinct humming

sound. From time ^ 1\ ^~%^ T yfea

to time they alight-
ed on the twigs or
leaves and searched
here and there for
colonies of the
aphis. The abdo-
men was generally
kept in throbbing
motion, and when
an egg was to be
laid a long slender
ovipositor was
thrust out and the
egg was placed on
a leaf or twig in the midst of or near the colony of the host insect.
It was noticed that certain bushes shaded from the sun after 1.30
p. m. were immediately deserted by these flies until the next day.

Fig. 3. — Syrphus ribesii, an enemy of the rose aphis: a, Fly; 6, lateral view
of head; c, larva or active immature form; d, anal spiracles; e, thoracic
spiracle of same. All much enlarged. (From Chittenden.)

Fig. 4. — Eupeodcs volucris, an enemy of the rose aphis: o, Female fly; 6, abdomen of male fly; c, hypopy-
gium of male fly. Much enlarged. (From Webster and Phillips.)

The rearing of five different species of syrphus fhes from larvae
found feeding on the rose aphis rather surprised the writer, and he
regrets that lack of time has prevented a continuation of the work

12 BULLETIN 90, U. S. DEPARTMENT OF AGRICULTURE.

that it might be ascertained if other species would also be commonly
reared.

Although the ladybird Hippodamia ambigua Lee, v/as observed
during the entire time occupied by the observations on the rose aphis,
it occurred in small numbers, and on only one or two occasions did it
seem to be feeding on Macrosiphum rosse.

DISEASE.

On March 14, 1910, after a night of rain, one winged and two
wingless aphides were found enlarged to fully five times their regular
size, as if bloated. This was probably due to a fungous disease.

EXPERIMENTS WITH REMEDIES.

The abundance of the rose aphis is so marked in many years that
frequently almost daily complaints of damage are made in the Dis-
trict of Columbia and vicinity. Wherever it has been convenient or
desirable to eradicate this species on small acreages of plants, water,
appKed with a garden hose or syringe, has been the remedy employed,
not alone by the writer but by many persons resident in Washington.
Indeed this treatment, which consists in directing a forcible stream
of water against the affected portions of the plants has been one of
the standard remedies advised. Experiments have been made by
Dr. F. H. Chittenden, by Mr. C. H. Popenoe, and by Mr. A. B.Duckett,
all in the District of Columbia and vicinity. In other regions, Mr. W. B.
Parker has undertaken experiments with nicotine sulphate, and the
writer has conducted quite a series of experiments with the same
compound. Among other compounds used by Messrs. Chittenden and
Popenoe for this species are aphis punk and other nicotine papers,
always with gratif}^ing success. While treating other forms of insects
on roses, such as ''slugs" and thrips, the aphides were always the
first to perish.

EXPERIMENTS IN THE DISTRICT OF COLUMBIA AND VICINITY, i

On March 28, 1913, at Washington, D. C, four rosebushes in the
greenhouse, well infested by the rose aphis, were sprayed with " black-
leaf 40," a preparation guaranteed to contain 40 per cent of nicotine
sulphate, in combination with whale-oil soap in the following formula:

Nicotine sulphate ounce.. \

W^iale-oil soap pound . . ^

Water gallons. . 2\

Although the solution slightly injured the terminal buds and the
tender shoots, the results were all that could be expected, 100 per
cent of the aphides being killed. It is beUeved that the solution
could have been reduced 25 per cent in strength with equally good
results.

'By A. B. Duckett.

Bui. 90, U. S. Dept. of Agriculture.

Plate III.

Spraying Rose Bush with Compressed-Air Sprayer by Hand.

THE EOSE APHIS. 13

On April 23, at a Virginia station near Washington, a number of
large rosebushes trained on the side of a house and well infested wdth
aphides were sprayed. Both winged and wingless forms of aphides
were present. Nicotine sulphate was applied, with and v/ithout the
use of soap as in the previous formula, at the rate of 1 part to 1,000
of water. In the experiments without the use of soap some diffi-
culty was found in obtaining a spreading action of the spray, and con-
sequently only about 90 per cent of the aphides were reached. It is
believed that all reached by the spray were Idlled. When nicotine
sulphate was used at the rate of 1 part to 1,400 parts of water
and 1 part to 1,500 parts of water, results were not satisfactory, only
about 25 and 10 per cent, respectively, being destroyed. With the
use of soap 100 per cent of the aphides on the vines were killed, the
results being very satisfactory. At the rate of 1 part of nicotine
sulphate to 1,400 of water with a laundry soap added, 90 per cent of
the aphides were killed; whereas the results with nicotine sulphate
at 1 part to 1,600 of water and 1 part to 1,800 of water in combination
mth soap were unsatisfactory, only 70 per cent and 50 per cent being
killed.

In these experiments a compressed-air sprayer with Bordeaux type
of nozzle v/as used at an estimated pressure of 90 pounds, and a fine
but driving spray was employed. The water used for the dilution of
the insecticide was particularly soft, but contained a very small
proportion of sulphur.

From these experiments it may be concluded that nicotine sulphate
at the higher dilutions as used in these experiments is much more
effective against the rose aphis when used in combination with whale-
oil or other soaps, since the spreading action thus induced is much
more favorable. The plants may, however, be injured in case the
spray solution is too strong. It is not beUeved that the injury shown
in the experiments was caused by nicotine sulphate used at too great
a strength, since it has been applied experimentally to roses in the
greenhouse at the rate of 1 part nicotine sulphate to 15 parts of water
without injury other than the appearance of mildew, undoubtedly
superinduced by the spraying. It is apparent from the results
obtained that a spray can not be emplo37'ed weaker than 1 part of 40
per cent nicotine sulphate to 1,400 parts of water with satisfactory
results unless in combination with whale-oil or other soap.

ARTIFICIAL CONTROL IN THE GARDEN.

Experiments have been conducted against the rose aphis with
different nicotine extracts under different conditions as to strength
and weather. In no case, in the writer's experience, were the plants
injured, whereas the insect was destroyed in enormous numbers.
The aphis is easily controlled by spraying with nicotine solutions.

14 BULLETIN 90, U. S. DEPARTMENT OF AGEICULTUEE.

contaiiimg 40 per cent of nicotine at the rate of 1 part of the solution
to from 1,000 to 2,000 parts of v/ater, with whale-oil soap at the rate
of 1 pound to 50 gallons of spray mixture. When only a few rose
bushes require treatment the spray may be prepared in small amounts
as follows: To 1 teaspoonful of 40 per cent nicotine solution add 1
to 2 gallons of water and one-half ounce of whale-oil soap. The soap
should be shaved fine and dissolved in hot water.

There are on the market numbers of solutions containing less nico-
tine than the foregoing which may be used with good results with
the addition of whale-oil soap, as advised, at the strength recom-
mended by the manufacturei-s. If these are not obtamable, very
good results may be accomplished by dissolvmg 1 pound of whale-
oil soap or 2 pounds of common laundry soap in from 4 to 6 gallons
of water. Wherever possible, however, the nicotine solutions should
be used, as better results wiU be obtained.

This species, Hke practically all of the green aphides, can also be
controlled by repeated applications of a forcible stream of cold water.
Since the roses in California and some other localities are much sub-
ject to mildew, repeated use of this method has the disadvantage of
increasmg injury by this disease. In the case of the appearance of
mildew, however, either through syrmging with water or through
the application of nicotine sulphate, this disease may be readily con-
trolled by adding to the nicotme sulphate solution copper sulphate
or blue vitriol at the rate of 1 pound to 50 gallons of water (approxi-
mately 1 ounce to 3 gallons). A solution of copper sulphate used
at this strength and sprayed on the plants after the application of
the water treatment is effective in controlling the mildew. Another
common practice of florists for the prevention of mildew is to dust
the plants immediately after sprmkling or watermg with common
flowers of sulphur.

In order successfully to fight this insect these sprays should be
applied with a compressed-air sprayer (PI. Ill) or bucket pr.mp
capable of creating a fine penetrating spray. These pumps can
usually be purchased at the seed stores at from $3.50 up to $15. The
nicotme solutions are also carried by most seed stores. Wliere a
pump is not to be obtained much can be accomplished by dipping
the infested twigs into a pail of the solution of nicotine.

From the experiments of the writer it is evident that this insect
can be destroyed easily by the use of nicotine solutions of considera-
bly less strength than have heretofore been used, but the treatment
must be repeated at mtervals to kill the aphides missed by former
applications. With the different styles of pumps now on the market
at low prices no one who cares for roses has the slightest excuse for
allowmg them to be injured by this insect.

THE EOSE APHIS. 15

TREATMENT IN THE GREENHOUSE.

For the treatment of the rose aphis as it occurs in greenhouses the
nicotine sokitions may be used, but at a lower strength than advised
in the preceding paragraphs. Conditions vary somewhat, but it is
believed that in most cases if the nicotme solution is used at the
strength of 1 part to 2,000 of water it will not injure the rose plants
if applied on a dark day or late in the afternoon so that the plants
will not be exposed to reflected sunlight through the glass.

When greenhouses contammg different forms of plants are syringed
with a forcible stream of water or with neutral soaps of the castile
or similar types for the red spider and other insects, the rose aphis
and other green aphides wiU also be kiUed. The same is true in
regard to fumigations with hydrocyanic-acid gas for other rose pests.
Directions for the use of h57-drocyanic-acid gas for the fumigation of
greenliouses and cold frames are given in Circular No. 37 of the
Bureau of Entomology. In the experience of Dr. A. F. Woods, the
author of that publication, the young growth of roses is particularly
sensitive and has been more or less injured in experiments in the use
of this gas. This is particularly true of such varieties as "Perle des
jardins," ''Mermet," and "Bride."

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V

i>IV. INSECTS

BULLETIN OF THE

c

No. 92

5 Contribution from the Bureau of Entomology, L. O. Howard, Chief.

May 15, 1914.

DESTRUCTION OF GERMS OF INFECTIOUS BEE
DISEASES BY HEATING.

By G. F. White, M. D., Ph. D., Expert, Engaged in the Investigation of Bee Diseases.

INTRODUCTION.

To reduce the losses due to bee diseases beekeepers have often
employed heat in one form or another. The direct flame has been
used in scorching or burning the inside of hives that have housed
infected colonies. Before being fed back to bees honey is often
heated for the purpose of destroying the germs of bee diseases, should
any be present. Heat is used in the rendering of wax and in the mak-
ing of comb foundation. It is natural and very appropriate, there-
fore, that beekeepers should inquire about the amount of heating
that is necessary to destroy the germs that produce diseases among
bees.

As no work had been done to determine the facts relative to this
question with any degree of accuracy, the writer has performed during
the last two years a number of experiments for the purpose of ascer-
taining them. Of these experiments 55 arc summarized in the three
tables included in this paper. It may be of interest to beekeepers to
know in a general way how these experiments were made. A brief
description of the methods used will serve also to make the tables
more readily understood. An aqueous suspension of larvae sick or
dead of the disease is made and placed in a small glass tube. This
tube is immersed in water of the temperature desired in the heating.
After the germ-containing material is heated in this way it must be
tested to determine whether or not the germs have been destroyed.
In the case of American foul brood this can be done by inoculating a
suitable artificial medium with the heated material and o])serving the
presence or absence of gTowth of Bacillus larvse, the germ of this dis-
ease. As there is no artificial medium now known suitable for culti-
vating the infecting agent of either European foul brood, sacbrood,

Note.— This paper is of interest to beekeepers in all parts of the United States; it was read before the
New York State Beekeepers' Association, February 10, 1914, at Ithaca, N. Y.
35960°— 14

2 BULLETIN 92, U. S. DEPARTMENT OF AGEICULTUKE.

or Nosema disease, healthy colonies of bees must be inoculated in
making the test in case of these diseases. Tliis is done by feeding the
bees the heated germ-containing material in sirup. If the disease is
produced by tliis feeding, naturally the infecting agent has not been
destroyed by the heating; but if the disease is not produced, it vir-
tually has been destroyed by it. By repeated experiments of this kind
in wliich the temperature used in the heating is varied, the minimum
temperature at ^vhich any virus is killed can be determined. As will
be seen from the tables, 13 experiments for European foul brood,
22 for sacbrood, and 20 for Nosema disease were made in which healthy
colonics were inoculated ^v■ith heated germ-containing material
from these thi-ee diseases, resj^ectively. In the last disease the
stomachs from diseased bees furnished the germ-containing material
for heating and feeding. In these experiments the temperature was
mamtained for 10 minutes as a rule.

DISEASES OF THE BROOD OF BEES.

Nearly a century and a half ago the name '"foul brood" was used
for a destructive brood disorder of bees, and for almost a century
later it was apparently the custom to diagnose as foul brood any
destructive disease of the brood. About half a century ago bee-
keepers began to note that all of the brood diseases are not the same.
They began, therefore, to write of different forms of foul brood.
At the present time it is known that there are at least three infectious
diseases of the brood of bees. All of these diseases are more or less
destructive, and it is quite likely that each of them has now and then
been diagnosed as foul brood. In America these brood diseases are
now known as European foul brood, American foul brood, and sac-
brood.

EUROPEAN FOUL BROOD.

In European foul brood death occurs early, the larvae dying usually
before the time for cell capping. There is no viscidity (ropiness) to
the decaying larvse as a rule, and no pronounced odor present.

Numerous samples of this disease have been examined from the
United States, and some from Canada. Its presence also in England,
Germany, Switzerland, and Denmark is strongly suggested by written
reports from these countries. It is very probable that the disease
has a much wider geographical distribution than these facts indicate.

Two years ago the fact was demonstrated that the germ causing
European foul brood is the microorganism to which the name Bacillus
pluton is given. In a paper ^ announcing the fact it was stated that
the studies then made indicated that the germ is easily kiUed by heat.
This beUef has been confirmed by further experiments.

» White, G. F., 1912. The Cause of European Foul Brood. U S. Dept. Agriculture, Bureau of Ento-
mology, Cir. No. 157.

DESTRUCTION OF GERMS OF BEE DISEASES BY HEATING, 3

Table I gives a brief summary of 13 inoculation experiments per-
formed for the purpose of determining approximately the amount of
heating necessary to destroy the germ of European foul brood.

Table I. — A summary of the experiments made to determine approximately the minimum
amount of heating necessary to destroy the germ, causing European foul brood.

Dates of inocu-
lation.

Tempera-
ture.

Time of
heating.

Results of inoculation.

°C.

Min.

Sept. 12, 1912

75 to 80

10

No disease produced.

Do..

65 to 70

10

Do.

Sept. 23,1912

64 to 66

10

Do.

Oct. 12,1912

64 to 65

10

Do.

Oct. 1,1912

62 to 63

10

Do.

Oct. 8,1912
Oct. 10,1912

62 to 63
62 to 63

Do.

Disease produced.

10

Oct. 4, 1912

61 to 62

10

Do.

Aug. 8,1913

60

20

Do.

Sept. 3,1912

60

10

Do.

Sept. 20, 1912

58 to 60

10

Do.

Sept. 28, 1912

57 to 60

20

Do.

Sept. 20, 1912

55 to 50

10

Do.

It will be observed by an inspection of Table I that European foul
brood was produced in every instance where healthy colonies were
fed disease material which had been heated for 10 minutes at tempera-
tures below 63° C. (145.4° F.), but that no disease was produced when
temperatures higher than 63° C. (145.4° F.) were used for the same
length of time. The minimum temperature that can be used, there-
fore, in destroying the germ of European foul brood, if it is applied
for 10 minutes, lies som.ewhere between 60° C. (140° F.) and 65° C.
(149° F.), being near 63° C. (145.4° F.).

AMERICAN FOUL BROOD.

American foul brood is the disease of the brood of bees that is best
known to beekeepers and is the one the presence of which they have
been able to recognize most easily. In this disease the larvae usually
die after the cells containing them are capped. The disease is charac-
terized especially by the marked viscidity (ropiness) manifested by the
decaying larvae that are dead of the disease. The pronounced odor
noticeable within hives housing colonies affected by this disease, espe-
cially in its later stages, is another well-known characteristic.

This disease is very widely distributed geographically. Samples
of it have been received from many localities in the United States,
from Switzerland, New Zealand, Germany, England, and France, and
it is very probable that it has a much wider geographical distribution
even than is indicated by these facts.

Until seven years ago the cause ^ of American foul brood was not
known. At that time the fact was demonstrated positively that the

1 White, G. F., 1907
mology, Cir. No. 94.

The Cause of American Foul Brood. U. S. Dept. of Agriculture, Bureau of Ento-

.4 BULLETIN 92, U. S. DEPARTMENT OF AGRICULTURE.

germ causing the disease is the one to which the name Bacillus larvse
is given.

The facts obtained to date are too meager to justify anything
more than a general statement regarding the minimum amount of
heating that can be employed in rendering material containing the
germ of American foul brood noninfectious. Taking rather wide
limits, it may safely be said that the minimum temperature at which
this can be done, if the temperature is applied for 10 minutes, lies
somewhere between 90° C. (194° F.) and 100° C. (212° F.). It seems
quite probable, indeed, that a temperature less than 98° C. (208.4° F.)
wiU suffice if applied for 10 minutes. When 100° C. was used the
spores of Bacillus larvse were killed in less than five minutes.

SACBROOD.

Observant beekeepers have for many yeare noted the presence of
dead brood which seemed to them to be different from that dead of
foul brood. Some were inclined to believe that the disease was
an infectious one; a larger number apparently were disposed to
ascribe the trouble to such causes as an unsatisfactory queen, starva-
tion, and the like. This brood disease has been recently demonstrated
to be an infectious one, and the name "sacbrood" has been given to it.
Larvse that die of this disease do so almost invariably after the time
of cell capping. The most characteristic symptom of the disease is
the saclike appearance of the dead larvse when they are removed from
the cell. This fact suggested the name "sacbrood " for the disease.

Sacbrood is frequently met with. Its presence has been diagnosed
by Dr. A. H. McCray and the writer in 367 samples received from 44
States of the Union and in 13 samples received from Canada. Reports
from England, Switzerland, and Austraha indicate strongly that this
disease exists in these countries also. It is very probable that it has
a much wider geographical distribution than is shown by these facts.

More than a year ago it was again the wi'iter's fortune to determine
the cause of another brood disease. UnUke the cause of either
European foul brood or American foul brood, the infecting agent
causing sacbrood has not yet been seen. It was demonstrated,
however, that the infecting agent in this disease passes through the
pores of earthenware filters. For this reason the cause of sacbrood
is spoken of as a filterable virus.

In a paper ^ announcing the cause of sacbrood the statement is
made that the germ causing the disease is destroyed by a com-
paratively small amount of heat. This beUef is confirmed by the
results of the experiments summarized in Table II.

I White, O. F., 1913. Sacbrood, a Disease of Bees. U. S. Dept. of Agriculture, Bureau of Entomology,
Cir. No. 169.

DESTEUCTION OF GEEMS OF BEE DISEASES BY HEATING. 5

Table II. — A summary of the experiments made to determine approximately the minimum
amount of heating necessary to render sacbrood material noninfectious.

Dates of inocu-
lation.

Temperature.

Time of
heating.

Kesults of inoculation.

°C.

MinuUs.

July 27,1912

95 to 100

2

No disease produced.

Aug. 8, 1912

95 to 100

2

Do.

Aug. 29,1912

75 to 80

10

Do.

Sept. 5,1912

65 to 70

20

Do.

Sept. 3,1912

55 to 60

20

Do.

Aug. 26,1913

80

15

Do.

Do.

75

15

Do.

Do.

70

15

Do.

Do.

65

15

Do.

Do.

65

15

Do.

Sept. 2,1913

65

15

Do.

Sept. 3,1913

60

20

Do.

Sept. 9,1913

60

15

Do.

Sept. 10, 1913

60

15

Do.

Sept. 17, 1913

60

10

Do.

Sept. 10, 1913

58

10

Do.

Sept. 17,1913

58

10

Do.

Sept. 18, 1913

57

10

Sacbrood produced.

Sept. 9,1913

55

20

Do.

Sept. 10, 1913

55

10

Do.

Sept. 17,1913

55

10

Do.

Aug 6, 1913

50

30

Do

From Table II it will be observed that when larvae dead of sacbrood
were heated 10 minutes at a temperature of 57° C. (134.6° F.) or less
and then fed to a healthy colony, sacbrood was produced ; if, on the
other hand, the dead larvae used in making the feeding were heated
to 58° C. (136.4° F.) or higher, the disease was not produced. The
conclusion to be drawn from these experiments is that the minimum
temperature, when maintained for 10 minutes, at which the infecting
agent causing sacbrood is destroyed Hes somewhere between 55° C.
(131° F.) and 60° C. (140° F.), being near 58° C. (136.4° F.).

DISEASES OF ADULT BEES.

Very Uttle is known about the diseases of adult bees. Many names
have been used for the purpose of designating them, but the number
of such diseases is probably small. There is only one adult disease
that can be diagnosed at present by laboratory methods. This one is
the Nosema disease.

NOSEMA DISEASE.

Fifty-seven years ago Dr. Donhoff made a more or less brief study
of a disease of adult bees in Germany. He observed that the stomach
was the organ that was primarily affected. By feeding to healthy
colonies in sirup the crushed stomachs from affected bees Donhoff
demonstrated that the disease could be transmitted to healthy colo-
nies. It was therefore infectious.

The work by Donlioff had been practically forgotten, apparently,
when Zander,^ of Erlangen, Germany, five years ago observed the

' Zander, E., Aug., 1909. Tierische Parasiten als Krankheitserreger bei der Biene.
zeitung.

Miinchener Bienen-

6 BULLETIN 92, U. S. DEPAETMENT OF AGEICULTUEE.

l)resence of a disease among adult bees. From the e^-idence at hand
it seems most probable that the disorder encountered by DonhoflF and
the one encountered by Zander are one and the same disease.

Aside from rediscovering the disease Zander has identified the germ
causing it as a protozoan (a one-celled animal parasite) and has given
to it the name Nosema apis. For the disease he has used the name
"Nosema Seuche." Tliis is an appropriate one, as it suggests some-
what the nature of the disease. The name ''Nosema disease," which
the writer suggests as the common name for tliis disease, is, it will be
observed, only a translation of the German name used by Zander.

The germ Nosema apis gains entrance to the body of the bee by way
of the alimentary canal. In the walls of the stomach the growth and
multiphcation of the parasite take place to an enormous extent,
causmg the abnormal appearance manifested by the organ. When the
disease reaches an advanced stage the stomach is white and fragile
and reveals upon a microscopic examination the presence of the para-
site in very large numbers. In the spring of the year, especially,
many weak colonies show upon examination a high percentage of
Nosema-infected bees. Quite often, indeed, in the examinations that
have been made of such colonies, 50 to 90 per cent of the bees in sam-
ples taken from them were found to be infected with the parasite.
It is an interesting and important fact that a very large number of
colonies which are strong and apparently doing well are found upon
examination to contain at least a small percentage of Nosema-infected
bees.

Nosema apis has a very wide geographic distribution. It has al
ready been encountered in Germany by a number of investigators;
it has been found in Austraha, Switzerland, and England. The
writer has found it in samples of bees received from 27 different States
in the United States and in two samples of adult bees from Canada.

From the facts gathered it would seem that many of the cases called
"spring dwindling" by the beekeepers are caused, m part at least, by
Nosema apis. This statement is not by any means to be interpreted
as saying that Nosema disease and spring dwindling are always the
same.

It has been demonstrated experimentally that colonies can be
weakened and killed by feeding to them material containing Nosema
apis. For this and other reasons it seems certain that the disease
causes a loss to apiaries, but, for want of sufficient data, the extent
of such loss can not now be estimated at all definitely. From the
facts at hand one is justified in at least drawing the conclusion that
Nosema infection in a colony tends to weaken the colony. Nosema
apis is therefore a germ in which the beekeeper is economically
interested.

DESTRUCTION OF GEEMS OF BEE DISEASES BY HEATING. 7

For the purpose of determiiiing approximately the mmimum amount
of heatmg that is sufficient to destroy the germ Nosema apis the uioc-
ulation experiments summarized in Table III were made.

Table III. — Summary of experiments in which tlie germ, Nosema apis, was heated and

fed to healthy colonies.

Dates of inocu-
lation.

Tempera-
ture used
in heating.

Time of
heating.

Results of inoculation.

°C.

Minutes.

Oct. 29,1912

95 to 100

5

No Nosema infection produced.

Nov. 12, 1912

95 to 100

5

Do.

Oct. 29,1912

80

20

Do.

Nov. 9,1912

80

10

Do.

Nov. 11,1912

68 to 70

10

Do.

Do

68 to 70

10

Do.

Nov. 12, 1912

65

20

Do.

Jan. S, 1913

65

10

Do.

Nov. 11, 1912

60

10

Do.

Do

60

10

Do.

Nov. 20, 1912

60

10

Do.

Feb. 8, 1913

58

10

Do.

Oct. 4, 1913

58

10

Do.

Feb. 8, 1913

57 to 58

15

Do.

Oct. 15,1913

57

10

Do.

Do

57

10

Do.

Oct. 4, 1913

56

10

Nosema infection produced.

Oct. 15,1913

56

10

Do.

Jan. 8, 1913

55

20

Do.

Jan. 31,1913

55

10

Do.

It mil be observed from Table III that when Nosema apis was
heated to 57° C. (134.6° F.) or liigher for 10 minutes and fed to
healthy bees no infection took place, but when held at tempera-
tures below 57° C. (134.6° F.) for the same period of time the bees
became Nosema infected. It is shown, therefore, that the minimum
temperature that will destroy the germ Nosema apis in 10 minutes
lies somewhere between 55° C. (131° F.) and 60° C. (140° F.), being
quite near 57° C. ( 134.6° F.) .

By way of parenthesis it might be well to say a word or two further
regarding Nosema disease. The studies of this disease disclose the
interesting fact that it is not a new one in American apiaries. There
is no cause, therefore, for anticipatmg any additional losses to our
apiaries. Indeed, since the presence of the disease is known, hopes
may be entertained that methods will be determined for reducing the
losses due to it. Considerable work must yet be done, however,
before methods for its control can be recommended.

Nosema disease is being studied in England, Germany, Switzer-
land, and Australia. During the last two years the writer has de-
voted considerable time to its study in America. The plan is to
continue the studies during the present year, after which it is hoped
a further discussion of this disease will be justified.

8 BULLETIN 92, V. S. DEPARTMENT OF AGRICULTURE.

SUMMARY AND GENERAL REMARKS.

The results of these experiments show that when they are main-
tained for 10 minutes the minimum temperatures that can be used
for destroying the germs of the four bee diseases now known to be
infectious are as follows:

( 1) The minimum temperature for European foul brood hes some-
where between 00° C. (140° F.) and 65° C. (149° F.), being approxi-
mately 63° C. ( 145.4° F.) .

(2) The mmimum temperature for American foul brood lies some-
where between 90° C. (194° F.) and 100° C. (212°) F., being probably
less than 98° C. (208.4° F.).

(3) The minimum temperature for sacbrood lies somewhere between
55° C. (131° F.) and 60° C. (140° F.), bemg approximately 58° C.
(136.4° F.).

(4) The minimum temperature for Nosema disease lies between
55° C. (131° F.) and 60° C. (140° F.), being approximately 57° C.
(134.6° F.).

It will be noted, therefore, that 63° C. (145.4° F.) for European
foul brood, 98° C. (208.4° F.) for American foul brood, 58° C. (136.4° F.)
for sacbrood, and 57° C. (134.6° F.) for Nosema disease are the ap-
proximate minimum temperatures at which the germs of these dis-
eases, respectively, are destroyed. Since there are varying factors
in experiments of this nature that tend to produce slight variations
in results, these temperatures are referred to as bemg approxi-
mate. It is probable that future experiments may cause slight
changes to be made in these conclusions. Nothing more than a com-
paratively slight variation is to be expected, however. In practice
the beekeeper, in destroying these germs by heating, will naturally
use a quantity of heat somewhat in excess of the minimum amount
that is absoUitely necessary.

Some generalizations may now be made which will be of interest to
the beekeeper. The melting point of beeswax is between 62° C.
(143.6° F.) and 64° C. (147.2° F.), mclusive. It will be observed that
this same temperature in 10 minutes will destroy the germ causing
European foul brood, and that it is about 10° F, above that which will
destroy the germs of sacbrood and Nosema disease. A further inter-
esting generalization may be made concerning the heating of honey.
Honey when heated to 160° F. reaches a temperature 15° F. above the
temperature necessary to destroy the germ of European foul brood
and about 25° F. above the temperature that wiU destroy the infect-
ing agents of sacbrood and Nosema disease. The infecting agents of
these three diseases of the bee, therefore, wUl be destroyed when the
temperature of 160° F. is used in the commercial handling of honey.
Finally, it is believed that the results of this work on the thermal
death point of the viruses of the bee diseases will be directly applica-
ble to the control of these diseases.

o

2)l\\L 3.'

BULLETIN OF THE

u

No. 93

Contribution from the Bureau of Entomology, L. O. Howard, Chief.
April 30, 1914. I

THE TEMPERATURE OF THE HONEYBEE CLUSTER

IN WINTER.

By E. F. Phillips, Ph. D., In Charge of Bee Culture Investigations, and
Geokge S. Demuth, Ajncultural Assistant.

INTRODUCTION.

The care of bees in winter is one of the most perplexing problems
confronting the beekeeper, especially in the North. This appears to
be due chiefly to the fact that it is difficult to determine by direct ob-
servation the normal activities of the bee colony in winter, and conse-
quently it is well-nigh impossible to determine what external condi-
tions are most favorable except by the gross results of experience.
Nor can we by a study of our wintering successes and failures deter-
mine definitely whether the same conditions of temperature and
humidity are desirable throughout the entire winter. On account,
therefore, of the lack of accurate knowledge of the activities of bees
in the winter season this problem has been taken up with the aid of
certain special apparatus and equipment. This preliminary report is
not to be considered as giving definite recommendations as to the care
of bees in winter, but rather is issued to make known to beekeepers
some of the interesting results obtained in the first season's work on
the behavior of the bees during the winter season.

American beekeepers lose thousands of dollars annually in winter
from the actual death of colonies and even still more from those
colonies that do not die, but which are reduced in numbers and
vitality. The wintering problem is therefore a vitally important one.
The factors influencing the welfare of the colony and the behavior
of the bees are numerous and closely interrelated. Of tlie chief ones
may be mentioned external temperature, food, ventilation, humidity,
the condition of the colony at the beginning of winter, and various
forms of irritation. In the present paper special emphasis is placed
on heat production, by which is meant the responses of the bees of
the cluster to the outer temperature and to changes in the outer tem-
perature as manifested in the generation of heat by the bees.

Note.— This bulletin presents studies of bees as affected by temperature conditions
during winter and is of special interest to beekeepers in the North.
36157°— Bull. 93—14

2 BULLETIN" 93, U. S. DEPARTMENT OF AGRICULTURE.

A special reason for this emphasis in a preliminary paper is that
all previous Avork on the temperature of the cluster in winter, of
■which there has been considerable, has failed to show definitely what
the normal responses are. The data are often those of abnormal con-
ditions and are tlierefore misleading, making them almost valueless
for purposes of application. One source of error which is to be
found in all the records known to the authors is the use of the mer-
cury thermometer, for, when such a thermometer is used, it is almost
impossible to avoid disturbing the cluster at each reading so that it
reacts abnormally. Furthennore, as the authors will attempt to
show at a later time, disturbances of the colony may influence the
temperature of the cluster for a considerable period, often more than
one day. Usually no account has been taken of the necessary cor-
rections to be made for the mercury thermometer.

Because of the errors in other work on the subject, due to the use
of mercury thermometers, the thermometers chosen for the work
here recorded are of another kind. Electrical thermometers are used,
by means of which readings can be made without approaching the
hive, and the thermometers (couples) are of course permanently
fastened in place. These are of the type known as thermocouples
or thermal junctions and the readings are made by means of a poten-
tiometer indicator and a sensitive galvanometer of the d'Arsonval
type. The wires used in the thermocouples are copper and con-
stantin (a copper-nickel alloy), giving an electromotive force of about
40 [lV per degree centigrade. A detailed description of the appara-
tus is impossible here, and it need only be stated that the method as
used gives readings to an accuracy of 0.09° F. (0.05° C.) ; the ther-
mometers are practically instantaneous in their action — that is, show
changes in temperature without a " lag " ; the readings of many
thermometers can be made consecutively on one carefully calibrated
instrument, insuring uniformity, which is impossible in using many
mercury thermometers; and, a point of importance in such work,
the readings can be made at the rate of two a minute, which would
be impossible with widely scattered instruments. In all, 161,617 tem-
perature readings were made during the winter 1912-13, and the
work is being continued.

Part of the colonies are kept in a well-insulated room (used as a
" bee cellar ") in the zoological laboratory of the University of Penn-
sylvania, Philadelphia, Pa., which can be kept at a temperature
usually varying not over 2° F., far more uniform than the ordinary
bee cellar. Abundant ventilation is provided, and the room is com-
pletely darkened to avoid possible disturbance by light. The tem-
peratures of the indoor colonies are read from an adjoining labora-
tory to eliminate the possible errors due to disturbance, and the room
is entered rarely (about once a Aveek on an average and, if possible,

TEMPERATURE OF THE HONEYBEE CLUSTER IIST WINTER. 3

only after the day's records are made) and only when absolutely
necessary. It is found that entering the constant-temperature room
may under some conditions influence the behavior of the bees in a
marked manner.

Other colonies are kept on the roof of the same laboratory, where
they are left untouched from the beginning to the end of a series
of readings. The wires of the thermometers are led to the room
below through rubber tubes, and all the temperature readings are
made at a distance, as is absolutely necessary to eliminate disturbance.
Disturbances of outside colonies have also been found to influence
their behavior in a pronounced manner, especially in cold weather.

By studying the temperature of various fixed points within each
hive it has been found possible to use the temperature readings as a
substitute for direct observations. After becoming familiar with
the normal temperature and the temperatures incident to various
activities one can tell the shape, location, and various activities of
the cluster by a study of the temperature of different points within
the hive and can, in fact, form an opinion as to the welfare of the
colony. It has therefore been possible to follow closely the activities
of each cluster without opening the hives and even without going
near them.

THE INFLUENCE OF EXTERNAL TEMPERATURE ON HEAT

PRODUCTION.

The colony (A) to be discussed under this heading was wintered
out of doors (1912-13) on the roof, where the bees were free to fly
whenever the weather permitted. It was in a 10- frame Langstroth
hive, with the entrance reduced to f inch deep and 8 inches wide, and
was not packed or given additional protection. This hive contained
19 of the electrical thennometers — 12 among the combs, 4 in the cor-
ners of the hive, and 3 on the bottom board. Readings were made
hourly from 9 a. m. to 4 p. m. through the winter (Sept. 26 to Mar.
28), except Sundays and holidays, and at intervals additional read-
ings were made every 15 minutes (or sometimes every 30 minutes)
during the night (5 p. m. to 8.45 a. m.) for periods of several days
each. In all, 41,413 temperature records were made for colony A.

The reaction of the cluster in heat production, as induced by
changes in external temperature, is well shown by the records made
from noon November 13 to 2 p. m., November 15 (1912), when read-
ings were made hourly from 9 a. m. to 4 p. m. and every 15 minutes
at night. From noon on November 13 the outside temperature
dropped slowly until 6 a. m., November 15, and the weather was
cloudy, so that the bees did not fly. It will be seen from the accom-
panying diagram (fig. 1) that at noon on the 13th the outside tem-
perature was about 69.2° F. and all the points within the hive were

BULLETIN 93, U. S. DEPARTMENT OF AGRICULTURE.

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TEMPERATURE OF THE HONEYBEE CLUSTER IN WINTER, 5

then cooler than the outside air, due to the fact that it took some
time for the inside of the hive to warm up. At 4 p. m, the outside
temperature had dropped to 65.3° F., when it was lower than any
of the points within the cluster, which had in the meantime become
warmer. From this time until 6 p. m. the next day (14th) the tem-
perature within the cluster gradually dropped as the outer air cooled,
until the lowest one (No. 9) was 57° F. (Outside temperature,
48.2° F.) The generation of heat began at 6.15 p. m. at this point,
which was to one side of the cluster, and is to be attributed to the
movement of the bees in forming a definite cluster. At 6.30 p. m.
a rise in temperature was noticed on thermometer 19, at the other
side of the cluster. Until 10.15 p. m. the changes in temperature
are probably to be interpreted as incidental to the formation of a
compact cluster, and from this time until the next day at the close
of the series of readings the thermometers within the cluster showed
a considerably higher temperature than the outer air, or than the
thermometers outside the cluster. The maximum in this series
was reached at 3.15 a. m., November 15, when thermometer 12 in
the center of the cluster registered over 89.4° F.

After the coldest outside temperature was reached and the outer
air began to get warmer (6.15 a. m., November 15), there was a
tendency for the cluster temperatures to drop. This is somewhat
noticeable in the case now being discussed, and is more clearly seen
in records obtained in other series. In general, after a period of
cold, when the outside temperature begins to rise, the cluster temper-
atures drop slowly to meet the outside temperature. The generation
of heat is reduced, or even discontinued, only to be increased when
the outside temperature again drops, or when it gets high enough to
induce greater activity, as in flight. It is found also by taking more
frequent readings when the cluster temperature is above about 69° F.
that it is less constant than when it is below this temperature, indi-
cating that at temperatures above this point the bees move about to
some extent, while between 57° and 69° they are quiet, unless flight is
desirable owing to a long confinement.

This series of readings is supported by numerous records taken on
this and other colonies throughout the winter and, since all the ob-
servations tend to confirm what was first seen on the record pre-
sented here, the authors feel justified in presenting a definite state-
ment of the reactions of the cluster to outside temperatures. It may
be added that a careful study of the records of previous investigators
fails to show a similar statement on this subject. When a colony is
without brood, if the bees do not fly and are not disturbed and if the
temperature does not go too high, the bees generate practically no
heat until the coolest point among the bees reaches a temperature of
about 57° F. At temperatures above 57° F. a compact cluster is
not formed, but the bees are widely distributed over the combs. At

6 BULLETIN 93, U. S. DEPARTMENT OF AGRICULTURE.

the lower critical temperature, which is for the present stated as
57° F., the bees begin to form a compact cluster, and if the tempera-
ture of the air surrounding them continues to drop they begin to gen-
erate heat within the cluster, often reaching temperatures consider-
ably higher than those at which they were formerly quiet and satis-
fied. It is evident, therefore, that the temperature within the cluster
is far from being uniform in winter, as has been, in a sense, assumed
among practical beekeepers. At the temperature at which other in-
sects become less active (begin hibernation) the honeybee becomes
more active and generates heat, in some cases until the temperature
within the cluster is as high as that of the brood nest in summer. To
sum up, when the temperature of a colony of undisturbed broodless
bees is above 57° F. and below about 69° F. the bees are quiet and
their temperature drifts with the outer temperature; at lower tem-
peratures they form a compact cluster, and the temperature within it
is raised by heat generated by the bees.

The authors desire to state that while the lower critical point,
57° F., appears rather well established, the observations up to the
present do not justify too definite a statement concerning the upper
limit of quiescence. It must be emphasized that these conditions do
not apply when the colony has brood. The rearing of brood in win-
ter causes a marked increase in heat production and constitutes a
condition which may become one of the most disastrous that can be-
fall a confined colony. This will be discussed at a later time.

Wlien the heat production of the colony is explained, we are able
to understand to some extent the divergence in the records obtained
by other observers. It has, of course, long been known that bees
generate heat, and it has been pointed out that during cold weather
the temperature of the cluster is often higher than during warmer
weather. While the temperatures previously recorded are in most
cases abnormal, due to disturbance, the chief difficulty in under-
standing the phenomena which take place is due to insufficient ob-
servations. For example, if between noon November 13 and 2 p. m.
November 15 only a half dozen temperature records had been made
for the cluster (and perhaps without finding the warmest part of it)
and the outside air, it would have been impossible to determine the
limits of heat production. Most observers have been satisfied with
a few observations, and seemingly everyone who has inserted a ther-
mometer in a hive has felt called upon to publish the results, thereby
only confusing the problem.

THE EFFECT OF CONFINEMENT AND THE ACCUMULATION OF

FECES.

Before beginning a discussion of the effect of confinement and the
accumulation of feces, it may be recalled that during the active
summer season the length of life of worker bees is in a sense deter-

TEMPERATUEE OF THE HONEYBEE CLUSTER IN WINTER. 7

mined by the work done by them, rather than by days or weeks.
The greater the necessity for excessive activity the shorter the term
of life. The authors believe that they have evidence to prove that
this applies to the winter also, and this belief is entirely supported
by the experience of beekeepers everywhere. That bees may come
out of winter quarters strong in numbers and vitality it follows that
the work to be done by the bees in the winter should be reduced to a
minimum ; and the winter problem, as thus interpreted, is therefore
to find the conditions under which broodless bees do the least work.
The work which broodless bees do in winter consists, so far as has
been determined, solely in the production of heat or in activity inci-
dent to flying on warm days (if free to fly), and therefore the prob-
lem, so far as it is under the control of the beekeeper, is primarily
to obviate the necessity for the production of heat. If brood is
reared the work of the bees is necessarily enormously increased, and
their vitality is correspondingly decreased. So far as evidence is
available in this work, the colony is not fully recompensed for this
expenditure of energy by an increase in the strength of the colony
by bees thus reared.

The colonies^ to be discussed under this heading (Nos. 1 and 3)
were wintered in the constant-temperature room in special 6-frame
hives (to economize space and concentrate the colony so that fewer
thermometers would be required) with full entrances and were not
propolized or sealed at the top. During the regular series of read-
ings the room was kept at a temperature which rarely dropped below
40° F. or went above 45° F., and the average temperature from
October 14 to March 6 was 42.67° F. This temperature was chosen
as being nearly the one usually considered best by beekeepers. The
foods given these colonies were stored in the combs, just as placed
by the bees. There was some pollen available in colony No. 1,
(Fig. 2.)_

According to what has been said in the previous section, we should
expect bees at such a temperature to maintain a compact cluster and
to generate some heat at all times. This was actually the case, the
temperature of the interior of the clusters dropping below 64° F.
only a few times in either colony.

Colony No. 1, on honey stores, was in the constant-temperature
room from October 12, 1912, to March 24, 1913, or 163 days.^ It

1 In order that the young bees might all get a flight before the winter confinement, the
two colonies here discussed were placed in the constant-temperature room after the brood
had been removed. They were kept here several days, removed for a flight, and then
returned to the room for the regular series. The significance of this manipulation must
be reserved for a later discussion. This explanation is made to show how it was possible
to put these colonies in the room so early in a climate as mild as that at Philadelphia.
The object was, of course, to increase the time available for observation. Bees are
usually not wintered in cellars in climates as mild as that of Philadelphia.

- In all, 24,077 temperature records were made for this colony.

8

BULLETIN 93, U. S. DEPARTMENT OF AGRICULTURE.

was then removed for a flight and put back the same evening, where
it remained until March 28. From March 7 at 9 a. m, until March
28 at 4 p. m. readings were made on this colony every 15 minutes
night and day, with the exception of the period between 9 a. m.
and 7 p. m. on the 24th, when it was out of doors. During this
period of three weeks the temperature of the room was changed
slowly, being raised as high as 64° F. and cooled to 13° F.

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FIG. 2. — Average daily temperatures of the center of the cluster of bees in colonies 1
and 3 and room temperatures, Oct. 14, 1912, to Mar. 6, 1913. Taken from readings made
hourly from 9 a. m. to 4 p. m. The room temperatures are indicated by the heavy line.

Wlien this colony was first placed in the room for the regular
series of readings, after a preliminary confinement, October 12 (the
readings were begun Monday, Oct. 14) , it maintained a cluster tem-
perature which usually lay between 64° and 68° F., the daily average
temperature departing from these rather narrow limits only four times
up to November 22. The average temperature is 66.5° F. During the
first five weeks the temperature of the room was less regular than
later (due to faulty working of the regulating apparatus), and this
doubtless accounts for some irregularities in the cluster temperature.
At first the three thermometers in the cluster (1, 2, and 5) gave tern-

TEMPERATURE OF THE HONEYBEE CLUSTER IK WINTER. 9

perature readings quite close together, while thermometer 6, which
was near the cluster, gave readings intermediate between the three
thermometers of the cluster and the four otliers in the hive, farther
from the cluster. After November 22 the records of the thermometers
in the cluster were more widely separated and the temperature of the
center of the cluster (shown on thermometer 5) tended to rise gradu-
ally. It varied constantly, but by December 7 and from then until
the end of the month, it averaged between 69° and 75° F. On Novem-
ber 29 and December 12 the cluster temperature rose to over 88° F.
From the 1st of January until March 6, which ended the regular
series of readings, the cluster temperature became more and more
irregular, and on January 20 the cluster moved (probably to accom-
modate itself to the stores) until thermometer 2 was nearer the center
and showed a higher temperature than thermometer 5. The size of
the cluster was gradually decreased by the death of bees, and all the
thermometers except 2 and 6 show a gradual decrease in temperature
until finally, from about February 25 to March 6, they are all low
and of nearly equal temperature. The two thermometers giving high
readings continued to show in general a higher and higher average
temperature and to become more irregular (except from February 15
to March 1), the periods of increased heat becoming more frequent.
There was absolutely no regularity in these intervals. After Febru-
ary 1 the temperature of the cluster varied between 75° and 91° F.,
the average from February 1 being 85.4° F.

On March 6 all colonies in the constant-temperature room except
two were removed. The colony described above (No. 1) and one
other (No. 12), not to be described at present, were left. On March
7 at 9 a. m. the temperature of the room stood at 42° F., and the
temperature of the interior of the cluster was about 84° F. The
brine which cooled the room was then shut off and the temperature
of the room rose very slowly and regularly, until on March 11 at
8.45 a. m. it was 64° F. For the first day the temperature of the
cluster was slightly variable, and at 10.45 p. m. thermometer 6, which
.had been cooler than thermometer 2, showed a rise in temperature
(probably due to a shifting of the cluster), and from then on to the
24th they were nearly of the same temperature at all times. On
March 8, at 3 a. m., thermometer 2 rose to 87° F. (room temperature,
48.5° F.), having previously shown a cooling. The cluster tempera-
ture then dropped slightly, showing relatively little variation until
at 4.15 p. m., March 9, it stood at 77.3° F. (room temperature,
55.7° F.). As the room temperature continued to rise, the cluster
temperature increased still more rapidly, until at 8.15 a. m., March
11, it reached 93° F. (room temperature, 64.2° F.). A little brine
was now turned on, sufficient to lower the temperature gradually to
58° F. at 9 a. m., March 12, and it again rose to 63.3° F. at 5.45 p. m.,

10 BULLETIN 93, U. S. DEPARTMENT OF AGRICULTUEE.

March 15. Durina: this period the cluster temperature followed the
room temperature, but remained constantly over 20° warmer. The
room was ag:ain cooled slowly, and the cluster temperature dropped
until on March 16, at 3 p. m., the room was 49° F. and the cluster
77.5° F. As the room continued to cool, the cluster temperature in-
creased, the bees responding to the colder temperature, until at 4.15
a. m., March 17, the room was 48° F. and the cluster 88° F. The
room then gradually warmed, and again the temperature of the
cluster dropped and then again rose with the room temperature,
remaining always over 20° warmer. At 6.45 p. m., March 19, the
brine was turned on full and the room cooled rapidly, reaching the
minimum of 13° F. at 9 p. m., March 20. At no time, however,
did any of the thermometers in the hive record a temperature below
33° F. Here it remained constant within 0.1° F. for about six
hours, during which time the cluster temperature varied between
86.5° and 89.5° F. (a difference between the room and the cluster
temperatures of 73° to 76° F.). The brine was now shut off and
the room again warmed until 9 a. m., March 24, when it reached a
temperature of 44.5° F. During this warming the cluster cooled
until at the close it was varying between 72° and 79° F.

As stated above, the colony was now (9 a. m., March 24) removed
for a flight and put back the same day at 7 p. m. In the meantime
the room was cooled to 33° F. When the bees were put back into the
room the temperature of the entire inside of the hive showed great
variation and naturally an increase due to the warming up while out
of doors and to the activities of a good flight. The points outside
the cluster dropped rapidly, but it was midnight, March 25 (31
hours), before the curves of temperature again appeared normal.
The room was slowly warmed to 63.2° F. at 6.30 p. m., March 26,
and then slightly cooled to 54° F. at 6 a. m., March 27, and again
warmed to 58.5° F. at the close of the series, 4 p. m., March 28.
After the flight the temperature of the cluster never dropped below
89.5° F., and the highest temperature reached was over 95° F, (soon
after the flight). Thermometer 6 remained high, but thermometer.
2, which had previously been high, now approached the other ther-
mometers, probably due to a rapid loss of bees and to a decrease in
the number of bees during the flight. It must be recalled that these
bees had been confined for an abnormally long time and were sub-
jected to treatment which is at least unusual. After this colony was
taken from the room for the last time it was found that thermometer
6 was over a patch of larva?, and, estimating as accurately as possible,
the eggs from which these hatched must have been laid at the time
when the room was coldest (March 20-21) and when the cluster tem-
perature was at its highest point. There had been no brood previ-
ously, according to the temperature records as compared with those

TEMPERATURE OF THE HONEYBEE CLUSTER IN WINTER, 11

of this colony earlier and with those of other colonies, nor was there
much evidence of increased heat production due to the presence of
brood until after the flight. Probably no extra heat was produced
for the eggs, and possibly the hatching of the eggs was somewhat
delayed by the low outer temperature. The effects on the cluster
temperature which might be expected from a flight, in relieving the
accumulation of feces, were not observed, because brood rearing had
been begun.

Colony No. 3 was placed in the constant-temperature room October
12, 1912, after a good flight, and readings were begun en Monday,
the 14th. In all, 2,165 temperature records were made on Colony 3.
The stores provided this colony consisted of honeydew honey, which,
was gathered in the department apiary and which, since it granulated
almost at once^ had been removed by melting up the combs which
contained it. After this operation it remained liquid. During the
summer of 1912 some of this honeydew honey was fed to a colony
in the open, during a dearth of nectar, and was stored in new combs
above the brood chamber, in which no cells of pollen were to be
found. After the second storing the honeydew honey was clear, well
ripened, and did not granulate. This colony was also in a 6-frame
hive, as previously described, and contained five thermometers (Nos.
14-18) among the combs. It is of course well known to beekeepers
that honeydew honey is not a good food for winter.

^^^len this colony was first put into the constant-temperature room
it behaved much as did Colony No. 1, except that the temperature
varied between 69° and 78.7° F. for the first week, being slightly
higher and more variable than that of Colony No. 1. The second
week it remained much the same, the temperature, however, varying
between 69° and 80° F. From this time on the temperature of the
center of the cluster rose rapidly, never dropping below 79° F. from
October 29 almost to the close of the readings. After November 4
the temperature remained above 86° F., and after November 11 it
dropped below 89° F. only twice until the end. Thermometer 17
at first read about 4° below thermometer 14, but after November 11
they were close together until November 25, when thermometer 17
began to cool rapidly, due to loss of bees, and after November 30
thermometer 14 cooled rapidly until, on December 9, it showed that
no more bees remained alive. From December 2 to 7, inclusive, there
was little heat generated, due to the scarcity of bees. It is of interest
to observe the records of thermometer 16, near the cluster, but usually
outside of it. It at first showed a temperature but little higher than
the two thermometers away from the cluster, but on October 31 it
began to rise until, on November 12, it reached 80.5° F., when it was
doubtless covered by the bees. Even the two thermometers (15 and
18) clear to the back of the hive rose until, on November 13, they

12 BULLETIN 93, U. S. DEPARTMENT OF AGRICULTURE.

recorded 61.5° F. These thermometers showed about the same tem-
peratures for about 10 days, and then these two and thermometer 16
showed a cooling, since the bees were dying so fast that there were
no longer enough to warm up these thermometers away from the
center of activity. It was to be expected that this colony would die,
and the experiment was performed to learn the phenomena incident
to the loss.

Before summing up the results of these two colonies, Nos. 1 and 3,
it may be stated that, so far as the evidence here presented is con-
cerned, the results as far as here discussed are confirmed by records
from 10 other colonies kept in the constant-temperature room, but
fed other foods and otherwise different. There is in all of the records
no evidence Avhich the authors can interpret as at all contrary to the
views here stated. A discussion of these other colonies is reserved.

It is evident from the behavior of colony No. 1 that at least one
factor entered which gradually caused the bees in the cluster to
generate more and more heat until at the beginning of the special
series, March 7, the cluster temperature was about 20° warmer than
it was at the same room temperature at the beginning of the confine-
ment. It is also seen that during the special series, March 7-24, the
cluster temperature always remained at least 20° above the room
temperature, whereas from the discussion of bees unconfined
(Colony A) we might expect them to cease heat generation when
above the lower critical temperature (57° F.). In the case of colony
3, fed on honeydew honey stores, the factor which caused more heat
to be produced evidently increased much more rapidly. As stated
previously, honeydew honey is a poor food for winter and is so
recognized. It contains the same sugars as honey, but contains in
addition a considerable amount of dextrin, the particular lot fed to
colony 3 containing 4.55 per cent while good honeys contain only a
fraction of 1 per cent. From the evidence at hand it appears that
dextrin can not be digested by bees and, whether or not this is the
explanation, honeydew. honey causes a rapid accumulation of feces
which usually results in the condition known as dysentery, in bad
cases of which the feces are voided in the hive. In the case of colony
3 the whole hive inside and out, as well as the frames and combs, were
spotted badly, the inside of the hive being practically covered. Even
with fine honey stores such a spotting is usuallj^ noticed after a pro-
longed confinement, especially in severe weather (or during brood
rearing). It therefore appears that the accumulation of feces acts
as an irritant, causing the bees to become more active and conse-
quently (see later section) to maintain a higher temperature. We
are therefore justified in believing that the cause of poor wintering
on honeydew honey is due to excessive activity, resulting in the bees
wearing themselves out and ultimately in the death of the colony.

TEMPERATURE OF THE HONEYBEE CLUSTER IN WINTER. 13

In the case of colonies on good stores (e. g., colony 1) the feces
accumulate more slowly and the excess activity is not so marked and
is induced more gradually. The accumulation of feces due to con-
finement causes increased activity and this in turn is the cause of
excessive heat production, resulting in a reduction in the vitality of
the bees.

It therefore follows that excessive activity causes the consumption
of more food, resulting in turn in more feces, so that colonies on
poor stores are traveling in a vicious circle, which, if the feces can
not be discharged, results in the death of the colony. In the work
here recorded no attention was paid to the theory that dysentery is
due to an infection, since there is nothing in the observations made
that lends any support to that idea. If there is more than one kind
of dysentery, as has been held, then the observations here recorded
must be considered as applying only to the type which can be in-
duced at Avill in any confined colony by giving poor food and which,
as has been long recognized, can be relieved at once by an opportu-
nity for flight.

While the activity of the cluster is greater at some times than at
others, there are not, as has been held, regular intervals of activity
at which the colony rouses itself to take food. At no time is a colony
kept at a room temperature of 45° F. or less in a condition which
can be characterized as inactive. Presumably the reported " inter-
vals of activity " have occurred when the colony made a noise due
to disturbance by the beekeeper.

The bees in colony 3 were compelled to work constantly to main-
tain so high a cluster temperature. In fact, they did more work
than colonies wintered in the open air. Keeping these bees in a cel-
lar protected them from low outside temperatures, but the lack of
opportunity for a normal ejection of feces caused a condition more
serious than extreme cold weather. We seem to have here an expla-
nation of the fact, often observed by beekeepers, that some colonies
wintered in the cellar are in worse condition in the spring than col-
onies that are exposed to severe cold. Poor food is evidently a more
serious handicap than low temperature.

METHODS OF HEAT PRODUCTION AND CONSERVATION.

A colony of bees in cold weather forms a compact, approximately
spherical cluster, but this cluster is not, as is usually believed, uni-
formly compact. In order to study the formation of the cluster and
as an aid to interpreting the temperature records in terms of action,
a colony (C) was placed out of doors in a narrow hive with double-
glass sides and top, and the stores were so arranged that the only
space available for the formation of the cluster was next to the glass
on one side, where it could be kept under direct observation. Since

14 BULLETIISr 93, TJ, S. DEPARTMENT OF AGRICULTURE.

the bees did not have roonu for a spherical cluster, they formed a
ring on the glass. Thermometers were then placed close together in
the outside space, so that the temperatures of various points could
be determined as desired. This hive was on the roof, and, while one
person watched the bees, constant communication could be kept up
with the person reading the temperatures in the room below by means
of a telephone, arranged so that the hands of both observers were
free. This colony was of course in the light, but the normal cluster
was nevertheless observed. It was disturbed as little as possible.

The nearly spherical cluster of bees consists, between the combs
and somQtimes above or below them, of an outer shell of bees close
together with their heads toward the center. This ring may be several
layers thick. The position with the heads inward is typical, except
when condensed moisture drops on the cluster as it often does in cool
weather, when the bees at the top turn so that their heads are up-
ward. The bees in this outer shell are quiet except for an occasional
shifting of position. Inside this rather definite shell the bees be-
tween the combs are not so close together nor are they headed in any
one way. Considerable movement, such as walking, moving the abdo-
men from side to side, and rapid fanning of the wings, takes j)lace
inside the sphere and when a bee becomes unusually active the ad-
joining bees move away, leaving an open space in which it can move
freely. Two bees may often be seen tugging at each other. In
addition to the bees between the combs, placed as above described,
others are in the empty cells of the comb on which the cluster is
always formed, always with their heads in. A verification of these
statements is contained in the following observations, and the ex-
periment may easily be repeated by anyone. For the purpose of
obtaining a colony without combs for another experiment, a hive was
opened December 15, 1913, while the outside temperature was low
enough to cause the formation of a compact cluster. When the combs
were separated the circle of bees in the shell was clearly observed.
When a comb from the center of the cluster was shaken the active
bees in the center of the circle dropped off readily, and those in the
outer shell which were somewhat sluggish were removed with more
difficulty. After this was done those occupying empty cells in the
center of the sphere backed out of the cells and were shaken off.
Finally those occupying cells in the border of the sphere backed out,
showing a well-marked circle on the combs. Evidently the bees in
the shell, whether in the cells or between the combs, are less active
than those in the interior of the cluster. Naturally such a manipu-
lation as this is not to be recommended, except for purposes of
demonstration.

It is clear from observations previously recorded that the highest
temperatures are those of points in the center of this shell, and this is

TEMPEEATUEE OF THE HONEYBEE CLUSTER IN WINTEE. 15

to be expected, as the heat is generated here. The outer shell consti-
tutes an ideal insulator for the conservation of the heat, since the
bees arranged so close together form small dead air spaces in their
interlacing hairs, especially those of the thorax, and afford still more
insulation with their bodies. The abdomens of the bees in the outer
row are practically separate one from another, and must often be
exposed to severe cold. That this method of conserving heat is
effective is shown by observations on undisturbed colonies out of
doors. For example, on January 14, 1914, there was at 9 a. m. a
difference of 68° F. between thermometers 14 (center of the sphere)
and 16 (outside the cluster) of Colony D, which were less than 4|
inches apart on the same level in the same space between combs, and
a difference of 75° F. between this couple and the bottom board 4^
inches below it. What this difference might sometimes be in colder
climates may be imagined. Examples of this kind might be multi-
plied indefinitely from the records of these experiments.

The source of the heat of the cluster must, of course, be the oxi-
dation of the food consumed by the bees. The bee is classed as a
cold-blooded animal in that the temperature of the individual bee
is practically that of the surrounding medium. There is obviously,
from the records just given, no internal regulation of the tempera-
ture of the body such as is found in birds and mammals, for the
temperature of a broodless cluster varies greatly. From the obser-
vations made on the various colonies, especially Colony C, it is clear
that heat for the warming of the cluster is produced by muscular
activity. "While, of course, some heat is doubtless liberated by other
life processes, this is practically negligible when bees are quiet, as
in Colony A when above 57° F. That higher temperatures may be
produced, greatly increased muscular activity is required, and in
Colony C in cold weather bees in the center of the shell of insulating
bees were seen fanning vigorously and executing other movements,
such as shaking and rapid respiration. We thus have the para-
doxical condition that bees fan to heat the cluster in winter as well
as to cool the hive in summer. Observations of this kind were
repeated beyond number, and this theory of the method of heat pro-
duction is entirely supported by the repeated observation of a hum-
ming noise from the cluster during cold weather.

A few details of the observations on Colony C may be of interest.
For example, one bee was observed fanning vigorously for 7^ minutes
(9.53 to 10.00-1 a. m., Jan. 23) while the other bees kept a space cleared
for it. The temperature of the nearest thermometer rose ^° F. during
this time. At 9.52 this thermometer was almost a degree cooler than
at the time of greatest heat during the fanning. The rapidity of fan-
ning of the wings varied, and toward the end of the time it became
so slow that the outline of the wings was distinguishable. After the

16 BULLETIN 93, U. S. DEPARTMENT OF AGEICULTUEE.

excessive activity this bee stood in the same place for a time. Rapid
respiration may play a more important part in heat production than
at first appears. One bee was observed to breathe 21 times in 14
seconds and then cease the rapid respiration. On other occasions
60 or more bees would begin shaking their bodies from side to side.

It has been shown in earlier sections that feces in the rectum cause
irritation, which induces increased activity and causes greater heat
production. It has also been found that other kinds of irritation
bring about the same result, but a discussion of these points can not
be undert4iken here. It is at least evident from the records obtained
in this work that colonies of bees in winter, either in cellars or out of
doors, should be disturbed as little as possible. This appears to apply
especially to cold weather out of doors or in the cellar, especially
after the colony has been confined for some time.

The facts mentioned concerning the ability of the bees to conserve
the heat generated will perhaps raise the question as to the tempera-
ture of the hive outside the cluster in cold weather, when the cluster
is compact. In the case of Colony A the temperature of the hive
outside the cluster was often practically as low as the outside tem-
perature. This colony was not packed and had a rather large en-
trance. If the cluster forms such an efficient insulator in itself it
might be presumed that packing about the hive is of little value and
that it might even be harmful, in that it would not serve to conserve
lieat and would prevent the heat from the sun from penetrating to
the cluster. This line of reasoning, however, does not follow, and
in any case it is unsafe to speculate about these things without mo'
facts. The effects of various forms of packing are being studied.

In closing it may be desirable again to state that too hasty cor-
clusions must not be drawn from the facts here presented. For
example, the records on heat production might be interpreted as indi-
cating the desirability of a cellar temperature higher than beekeepers,
usually believe to be best. Experiments to test such a theory are now
being carried on, and it is found that a broad statement as to the
best cellar temperature can not yet be given. Under most conditions
colonies can not be brought to the critical temperature, 57° F., with-
out disturbance. It is hoped that more work will throw some much-
needed light on this important subject.

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^- . r'SEOTJ^.

BULLETIN OF THE

MPMllOrAffldTlI

No. 95.

Contribution from the Bureau of Entomology, L. O. Hov/ard, Chief
July 9, 1914.

INSECT DAMAGE TO THE CONES AND SEEDS OF PACIFIC

COAST CONIFERS.^

By John M. Miller,
Entomological Assistant, Forest Insect Investigations.

INTRODUCTION.

Recent damage by insects to the cones and seeds of conifers
has been brought to notice by the collectors of forest seeds. Com-
pared with other commercial seeds the market price of forest seeds
is high, owing to the limited demand, the special knowledge required
for their collection, and the irregular production of conifer crops.
A heavy percentage of damage materially decreases the profits of seed
collection and may result in time and money fruitlessly spent. Seed
that is badly infested or damaged by insects can not be sold to
reliable dealers when its character is recognized.

It has been found that insects sometimes destroy practically all
of the seed crop of a tree species in one locaHty in a season. In this
respect insects have a certain relation to the future supply of timber,
as the natural reproduction of forests is assured only by the produc-
tion of a prolific supply of uninjured seed. (PI. I, fig. a.) The
artificial reforestation of denuded areas must also depend upon the
collection of sound forest seed. An example of how insects may
interfere with reforestation by a desired species has been furnished
by the white fir on western national forests. ]\Iuch of the seed of
this species collected recently has been worthless for planting, a
great percentage of this loss being due to insect damage in the cones
and seeds.

Some information regarding insects that affect forest seeds and
reproduction has been given in previous publications of the Bureau

1 The names of the insects are not mentioned in this prehminary contribution because many of them are
not yet named or described. When this has been done it is intended that a special bulletin on the subject
shall be prepared by the same author.— A. D. Hopkins, in Charge of Forest Insect Investigations.

Note. — Information regarding insects that seriously affect forest seeds, especially in the coniferous
forests of the I'acific coast. A practical paper, of interest to seed collectors, dealers in forest seeds, and
planters of forest areas ; of particular appUcation to Pacific coast regions.
38961°— 14

2 BULLETIN 95, U. S. DEPARTMENT OF AGRICULTURE.

of Entomology.^ This bulletin gives further facts regarding the
character and extent of damage to the seed of coniferous forests
of the Pacific slope. It also furnishes preliminary information
on the more important groups of insects causing this damage, and
their habits, that it may be available to seed collectors during the
present spring and summer.

CHARACTER AND CAUSE OF DAMAGE.

Damage to the seed of conifei-s is caused by various species of
insects which feed upon the buds, flowers, immature cones and seed,
and mature seed. Great damage is accomplished while the cones
are immature and before the seed ripens. Cones which are infested,
or 'Svormy," are often found when the areas for seed collection are
bemg located. Wormy cones and seeds are caused by the adults
and grubs of small beetles, the ''worms" or caterpillars of moths, the
maggots of gnats, and the larvse of tiny wasps known as seed chal-
cidids. In his work the seed collector usually encomiters these im-
mature stages of insects which depend upon the cone scales and seeds
as their principal source of food supply. With the exception of the
cone beetles the adult insect is seldom found in the immature cone.
The insects may be found in almost any part of the cone or seed, the
feeding habits varying much with the different species. In many
cases the presence of these insects in the cone is evident and may be
recognized by the peculiar type or class of injury. Where this is the
case the daniage may be approximately estimated during the summer.

With the more important seed-infesting insects the damage will be
recognized in one or more of the following classes:

BUGHTED CONES.2

The cones are sometimes killed when small and immature. As a
result they wither and dry, and none of the seeds fill. Cones so
affected are often described as blighted. Most of the injury of this
character occurs in the cones of pine and is caused by the cone beetles.
The attack is usually on the second-year cones, although the small
first-year cones are sometimes killed. Some of the cone worms, also,
bore into the cones in such a manner as to kiU them and cause the
same blighted condition. Sugar-pine cones attacked by the beetle
nearly alwaj's fall to the ground during July and August. The cones
of other species usually adhere to the tree for a winter or two. Damage
of this type is easily recognized and can be estimated after the middle
of July.

1 Hopkiiis, A. D., Catalogue of exhibits of insect enemies of forests and forest products at the Louisiana
Purchase Exposition, St. Louis, Mo., 1904. U. S. Dopt. Agr., Div. Ent., Bui. 48, p. 13-14, 33, 1004.

Hopldns, A. D., Insect enemies of forest reproduction. U. S. Dept. Agr. Yearbook, 1905, p. 250-251,
1906. ( Yearbook Separate 381 . )

Rohwer, S. A., VI, Chalcidids injurious to forest-treo seeds. U. S. Dept. Agr., Bureau of Entomology,
Tech. Ser. 20, Pt. VI, p. 157-163, Feb. 10, 1913.

» PI. I, figs, cl, d; PI. II, figs, a, 6.

INSECT DAMAGE TO SEEDS OF PACIFIC COAST CONIFERS. 3

WORMY AND ABORTED CONES.i

In some forms of injury the cone is not lulled, but may show masses
of resin on the surface, castings caused by the feeding of larvae, or
little burrows through the scales, seed, and pith which contain small
larvas. In rare cases the cone may be aborted or deformed, forming
a pecuHar growth or shaj^e. The cone, however, continues to grow
and matures at the close of the season very much like a normal one.
The seeds which are not mined or eaten by the insects fill and mature.
Damage of this character may be foimd in practically all species of
conifers. Much of it is caused by the caterpillars of different species
of moths, some of which show nothing on the surface of the cone to
indicate their work in the interior. The amount of damage to the
seed of western yellow pine and Jeffrey pine throughout northern
California and southern Oregon in 1912 was estimated by the writer
to vary from 50 to 90 per cent of the crop.

WORMY SEED.2

This class of injury is found only in the seeds. The cone is not
affected and shows no indication of the insect. Practically all of the
reported damage of this type is caused by the larvae of tiny wasps
called seed chalcidids. A certain percentage of the seeds will be
infested by a small, white, headless larva. The infested seeds are of
normal size and appearance. The larvse feed entirely within the
inner lining of the seed. Damage of this type can be found only by
cutting the seed open. Seeds which have been attacked are hollow
and usually contain the small headless larvse of the chalcidid. After
the seed has been stored over winter some of the adults emerge,
boring small clean-cut holes through the outer shell of the seed. This
is the first external indication of these insects. Quite often seed
infested by the seed chalcidid is collected and sold before the infesta-
tion is detected. Injury of this type is very common in certain
species of fir, in which the damage has sometimes been found to run
as high as 75 to 90 per cent of the cleaned seed. Species of seed
chalcidids have also been found in the seed of western yellow pine
and Engelmann spruce.

MAGGOTY CONES.

Many cones are injured by the maggots of flies and midges, some of
which cause no appreciable damage to the seed. Small whitish or
pink-colored maggots are found in the cones of nearly all conifers.
They are the larvae of tiny gnats, or midges. The pinkish maggots
cause little masses of resin among the scales but do not seriously
affect the seeds. The whitish maggots in fir cones cause considerable
damage to both cone and seeds. (See PL III, figs, a, c.) They are
often present in vast numbers and leave the cones when these are

iPl. I,fig. 6 2 PI. Ill, flgs. 6, d.

4 BULLETIN 95, U. S. DEPARTMENT OF AGRICULTURE.

spread to dry. They are among the most common insects noted in
the work of seed collecting.

IMPORTANT GROUPS OF SEED-INFESTING INSECTS.

There are four important groups of insects which cause practically
all of the serious damage under the four classes described.

CONE BEETLES.

Cone beetles are small, dark, cylindiical beetles which attack the
cones of pines. The cones are killed by the attack of the adult,
which bores a small tunnel into the axis to deposit its eggs. (PL II,
fic. h 1.) The larvae (PI. I, fig. d) feed on the seeds and scales of the
withering cone and develop to the beetle stage within the dead cone,
where the beetles usually remain over winter. The attacks of several
species of these beetles are very common in western yellow pine and
sugar pine. The damage to crops of sugar pine is considerable, as
these beetles have been noted in some seasons to kill from 25 to 75
per cent of the cones over large areas.

CONE WORMS.

Cone worms are most frequently met with in the cones in the
caterpillar stage. They represent several species of moths which
infest the cones of pines, firs, hemlocks, and spruces, and even the
seed of incense cedar has been found to be attacked by the tiny larvae.
The moths are small and in most species dull colored and inconspicu-
ous. The small white larvae of one species are very common in the
cones of western yeUow pine and Jeffrey pine. They feed upon the
seeds and scales without killing the cone and overwinter as larvae
and pupae in galleries in the pith of the cone axis. (PI. I, fig. h.)
Another species is a very common enemy of Douglas fir seed on the
Pacific slope. The larvae mine a gallery through the scales, leaving
an opening at the surface through which resin and larval castings
exude. The pupae overwinter near the axis in resinous cocoons among
the scales. Nearly all species feed without killing the cone, but a
large caterpillar feeding on western yellow pine sometimes kills the
immature cone, the damage resembling that of the cone beetle.

SEED CHALCroiDS.

The adults of seed chalcidids are tiny wasps (PI, III, fig. d). The
larvae (PL III, figs. &, d) live witliin the seeds, apparently developing
as the seeds grow, so that the infested seeds reach normal size and

Explanation of Plate 1.— a, Photograph near Bray, Cal., showing cones of western yellow pine on
ground, but poor reproduction; b, mature western yellow pine coue, showing pith occupied by the cone
worm and seeds destroyed by it; cl, blighted western yellow pine cone caused by tlae cone beetle; cS,
normal cone; d, young living western yellow pine cone, greatly enlarged, to show character of damage
by the cone beetle and its larvae. (Original.)

Bui. 95, U. S. Dept. of Agriculture.

Plate I.

Insect Damage to Reproduction of Western Yellow Pine.
[For explanation of plate see note at foot of page 4.]

Bui. 95, U. S. Dept. of Agriculture.

Plate

Fig. a.— Sugar-Pine Cones Attacked by the Cone Beetle at Different Stages
OF Growth of the Cone. (Original.)

[The longer cone, which is about 11 inches long, resisted attack, while the others were killed.]

Fig. B.— Longitudinal and Transverse Sections of Sugar-Pine Cones, Natural
Size, Showing Primary Egg Galleries, B1, Made by the Cone Beetle.
(Original.)

WORK OF THE CONE BEETLE IN SUGAR PINE.

Bui. 95, U, S. Dept. of Agriculture

Plate III

Work of a Chalcidid in Seeds of Pacific Coast Conifers.

a, Cross section of sound, mature white fir cone with unaffected seed; 6, yellow pine seed,
enlarged, infested by larvse and newly transformed adults of a seed chalcidid; two un-
opened seeds show exit holes made by these insects; c, cross sections of two maggoty
white fir cones; d, male and female adults of seed chalcidid, larva in opened seed of
red fir {Abies magnijica), and exit holes in two other seeds of same. (Original.)

INSECT DAMAGE TO SEEDS OF PACIFIC COAST CONIFEES. 5

form. There are several species, one of which is very destructive to
the seed of Douglas fir, white fir, and red fir.

FIR-CONE MAGGOTS.

Fir-cone maggots are the larvae of small gnats which have been
found in the cones of white fir, red fir, and alpme fir. They mine
through the scales and seeds, causing great damage. The larvse do
not winter in the cones but burrow into the ground as soon as the cones
fall. They form small puparia within an inch or so of the surface,
and there they overwinter.

ADAPTATION OF THE INSECTS TO THE INTERMITTENT CONE-
PRODUCING HABITS OF THE HOST TREES.

There is a general life cycle for most of the cone-infesting Insects
corresponding to the period required by tlie host tree to develop the
seed crop. The adult insect, whether beetle, moth, fly, or seed
chalcidid, deposits the eggs in the spring or early summer while the
cones are small and undeveloped. With some species the attack is
such that the cone is killed; with others the attack and feedmg of the
larvae do not interfere with the growth of the cone, wliich matures
at the normal time, although much of the seed may be destroyed.
The feedmg of the larvae ceases, however, when the cone matures,
usually during September. The insects then undergo a long dormant
period either as larvae, pupae, or new adults. This dormant period
contmues until there is another crop of cones m a proper condition for
attack; that is, the soft, immature cones which are found in the spring
or early summer. Some insects pass this dormant period in the pith
of the cones or in resinous masses among the scales. Other species
leave the cones and form the pupae in the ground or in debris on the
surface.

The intermittent character of the seed production of conifers is a
well-estabhshed fact.^ A few cones are produced every year, biit a
good crop occurs at intervals of from two to five years. The years of
total failure are known as "oQ. years." It is evident that if the
entire brood of any of these species of cone-infesting insects emerges
annually, it will sooner or later encounter an off year of the host tree.
This would mean the complete failure of the food supply for one
generation and would result in the almost complete extinction of the
species within the forest area affected by the crop failure. As a
matter of fact, observations show that this seldom happens. All
the individuals of a brood of overwintered insects do not emerge the
following spring. Many of them do emerge after the fii-st winter, but
a large percentage of the brood, in some species 50 per cent or more,

' U. S. Dept. Agr., Forest Service, Bui. 98, p. 13, Nov. 18, 1911.

6 BULLETIN 95, U. S. DEPARTMENT OF AGEICULTURE.

continues for another year in the same condition in which the first
winter was passed. Usually this retarded part of the brood emerges
at the end of the second winter or sprmg.^ This is an adaptation
which to a certain extent accounts for the contmued mfestation of
certain species of insects in the seed of forest trees. In the case of a
species of gnat which infests the cones of white fir it was found that
the entire brood of insects which destroyed the 1911 crop of seed on
an area in northern CaUfomia did not emerge at all in the spring of
1912, but remained in the pupal state through the summer of 1912
and the folio whig w^inter. The adult flies finally emerged m the sprmg
of 1913. Under this adaptation it would appear that only a con-
tmued failure of the crop through a series of years would result in the
reduction of the numbers of the infesting species on a forest area.
Undoubtedly other agencies are responsible for the uninfested con-
dition of the seeds of certain trees during some seasons.

INDICATIONS OF INSECT DAMAGE.

Attack of the cone beetle in the seed crop is indicated by a small
entrance hole at the base of the cone, with castings or small pitch
tubes, during the early summer; later, by the brown, withered-appear-
ance of the cone.

The attack of the cone moth may sometimes be recognized by
little masses of pitch and larval castings on the surface of the cone
and sometimes by withered cones, but it is best to look for the cater-
pillar among the scales and in the seed and pith. It is always best
to cut the cone open, sectioning it several different ways, in making
the examination.

The attack of the fir-cone maggot can also be found by cutting or
breaking the cone open. The larval mines will be found in the scales
and seeds, in which will usually be found the small, white, active larvae.

The seed chalcidids show no external evidence, and the seeds must
be sectioned or otherwise opened to find the larvae of these insects.
Unless test is made the amount of damage can not be determined,
and seed that is badly infested may be taken as sound.

METHODS OF PREVENTING LOSSES.

There are areas of light infestation by these insects in certain
species of trees, and there are areas where the damage is very heavy.
The amount of infestation in the seed may also vary with succeeding
seasons. A careful examination of the cones before the seed matures,
during July and August, will usually reveal immature stages of the
seed-infesting insects. If cones of the past season are examined
during the winter and spring, they will indicate whether or not the

> This retarded emergence has not been observed in the case of the cone beetles, but it has been
observed in the more important cone worms, fir-cone maggots, and seed chalcidids.

INSECT DAMAGE TO SEEDS OF PACIFIC COAST CONIFERS. 7

area is infested by these insects. In the collection and cleaning of
forest seeds there is opportunity for use of the information which is
now being gathered on this subject. An intelligent selection of the
seed-collecting areas will prevent much of the loss due to gathering
seed which is afterwards found to be infested or worthless.

A count of the number of infested cones and of damaged seeds will
give a clue to the percentage of damage in the crop. Wliether or
not the damage is sufficient to make collection of the seed unprofitable
on the area will have to be determined by the collector.

o

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1914

BULLETIN OF THE

No. 96

5 Contribution from the Bureau of Entomology, L. O. Howard, Chief.

July 22, 1914.

(PROFESSIONAL PAPER.)

THE TEMPERATURE OF THE BEE COLONY. ^

By Burton N. Gates, Ph. D.,
Fornwrh/ ApicuUural Assislanf, Bureau of Entuinologi/.

INTRODUCTION.

There has been a decided need of accurate knowledge of the
temperatures and changes in weight of colonies of bees, particularly

ring the winter. Previously existing data have not been gained
under controlled conditions, but generally by casual observations,
limited in number. Most of the previous work has also been for a
short period of the year. In tliis work an effort has been made
to get more reUable information by collecting data for practically
the cycle of a year. The knowledge of the changes in temperature
and weights is needed in a careful study of methods for successfully
wintering bees. Tliis is one of the greatest difficulties which the
beekeeper has to meet, and it is hoped that the present work may
furnish data for a further study of the wintering problem. The
scope of the work here recorded is indicated by the following figures:

Period of experimentation, October 22, 1907, to September 26, 1908.
Number of observations, 2,576+.
Number of separate readings, 20,000+.

APPARATUS.

The apparatus was constructed to meet emergencies which might
arise, wMch accounts for its many parts. It was planned so that the
complete apparatus could be upon the scales at all times, thus
obA^ating complications from corrections in weigliings.

THE SCALES.

A finely adjusted platform scales was speciall}^ constructed,
wliich registered with a sensitivity of 10 grams to a maximum of
200 kilograms. It was expected that it would be possible to record

1 This report of work done for the Bureau of Entomolog}' has been accepted by the faculty of Clark Uni-
versity, Worcester, Mass. , as a dissertat ion in partial fulfdlment of the requii'ements for the degree of doctor
of philosophy , and accepted upon the recommendation of Dr. C. F. Hodge. The author has been appointed
to the position of assistant professor of beekeeping, Massachusetts Agricultui'al College.

Notf:.— A study of the eflects of temperature on l)eos, and of interest to beekeepers generally.

38957°— Bull. 96—14 1

BULLETIN 06, V. S. DEPARTMENT OF AGRICULTUEE.

1

slight changes in consumption or*increase of stores. By means of a
double beam it was possible to counterbalance for extra thermometers
or other small special apparatus wliich might be added temporarily,
\nthout necessitating a correction of the hourly readino-s. The
scales were found to be relatively satisfactory, but in times of heavy
^vind extra precaution was necessary in order to overcome the
influence of drafts on the scales. In winter this could easily be

accompUshed by closing the door
of the shed in which the experi-
ment was carried on. For outdoor
work, however, some difhculty was
experienced, as Arlll be explained.
The agate-set bearings were also
sensitive to jar, which was con-
stantly guarded against.

THE THERMOMETERS.

Seven mercury thermometers
were used, of the type known as
incubator thermometers, which
have a long stem and can be read
to fifths of a degree. One instru-
ment, how^ever, used to register
the temperature of the outside air
w^as an ordinary chemical ther-
mometer. These instruments were
standardized and w^ere graduated
to the centigrade scale.

^ THE HIVE AND ITS APPLIANCES.

Fig. L— The hive used iu the experiment on the
temperature of the bee colony: A , storage cham-
ber for accessories, with door; B, bottom board
with entrance; C , collar with feeder; D, brood
chamber; E, perforated zinc honey board; F,
second story for surplus; G, thin board wilhholes
for thermometers; //, case protecting thermome-
ters a-c: I, outside cover.

Figure 1 illustrates the general
appearance of the liive, showing
the live stories. Only one of these
w\as occupied by bees, as will be
explained. The liive was of the
standard 10-frame Langs troth

type. Tlii'oughout the experiment it stood on the scales (fig. 2) . The

several parts were as follows:

A. The lower part consisted of a hive body with one side rem vcA To the
bottom was nailed a thin cover board, which served as the floor of the comparl -
ment. The purpose of this chamber was to store fixtures, such as frames "dum-
mies," extra thermometers, and the like, while they were not in use. In this way it
was unnecessary to compute in the weighings for any change in the apparatus For
example, m the winter, when four frames in the brood chamber wen^ replaced by the
"dummies," these were taken from the storage chamber and the frames hung in their
place, without altering the weighings.

THE TEMPERATURE OF THE BEE COLONY.

B. An ordinary bottom board.

C. This wooden collar contained the feeder and increased the space between the
bottoms of the brood frames and the bottom board, thus allowing the insertion of a
thermometer below the frames. The feeder was what is known as an Alexander
feeder. The end may be seen extending out of the collar at the rear of the hive. In
this projection, which was provided with a wooden cover, the sugar sirup is poured
without disturbing the hive. The cover prevents drafts of air through the feeder.

D. Above the collar was the hive body in which the bees were located. The frames
were spaced with metal spacers (fig. 3), and wedges between the central frames held
all firmly in place. In this way everything was sufficiently secure to enable any
possible manipulation, even to turning the hive upside down, should it be necessary,
■without displacing parts. .
The wedges also increased
the -space between the
central frames sufficiently
to allow for the insertion
of the stems of thermom-
eters. The gauge in
frames 3 and 4 permitted
the insertion of thermom-
eter e (fig. 3). The frames
were wired and filled with
full sheets of foundation
before insertion. Two
holes were bored in the
middle of the front above
the entrance, for use in
case it should become de-
sirable to insert thermom-
eters. Throughout the
experiment these were
closed with corks.

E. Between bodies D
and F was a perforated
zinc honey board.

F. A second body was
provided in case more
comb space should be-
come desirable.

G. The top of the hive
proper was covered with
a thin cover. This, as is
shown in figure 3, had
four holes drilled in the median line and one directly over the rear part of the space
between frames 3 and 4. Through these holes thermometers fitted in corks were
inserted.

II. This was a special hive body used as a protection for the thermometers. One
side, shown in figure 2, was removable so as to permit easy reading of the instruments.
In this chamber and around the thermometers were two cushions of ground cork, for
the protection of the tops of the thermometers and for the conservation of the heat of
the cluster in the extreme of winter.

/. A metal cover.

Fig. 2.— Hive on scales in shed where it was kept during the winter.

4 BULLETIN 96, U. S. DEPARTMENT OF AGEICULTUKE.

A series of clamps, which drew over screw heads, held the several
parts firmly together, preventing the bodies from sliding and snapping
the stems of the thermometers.

The "dummies" above mentioned consisted of ordinary frames
into which boards were fitted snugly. These were used in the winter
months instead of the two outside frames on either side of the hive,
thus forcing the cluster to occupy six frames in the center of the
brood cliamber. In this way it was made certain that the cluster
would not shift away from the thermometers during the winter. The

Fig. 3.— The hive from above, showing the spacing of the frames. The corks in the cover indicate the

localiou of the thermometers.

"(himmies" were removed wlien l)rood rearing became established
in the spring. These were not intended primarily for protection and
did not fit the hive tightl3^

In order to eliminate the annoyance and possible complications
from propolizing, all the interior wooden parts were varnished and
polished to a piano finish.

It should be said that not all of the parts of the apparatus provided
were pressed into service. The extra body, Z>, was not needed, and
consequently the honey board, E, was not used. The outfit as

THE TEMPEBATURE OP THE BEE COLONY. 5

actually used and as it appeared in position until the writer was
forced to move the experiment to the country in July, 1908, is shown
in figure 2.

THE BEES.

Throughout the experiment Caucasian bees were used. Two colo-
nies were necessary. The first drew out the foundation in the frames
and was used during September and October, 1907. Tlie second was
hived in November, 1907, and served throughout the remainder of
the experiment. This colony did not swarm.

THE ARRANGEMENT OF THE THERMOMETERS.

The thermometers were designated a, h, c, d, e,f, and o. Thermom-
eters a, h, c, and d were inserted between the central combs. They
were arranged at regular intervals, a being at the front of the hive
and nearest to the entrance. Thermometer e was placed at the rear
of the hive between combs 3 and 4, and was expected to represent
the temperature of the margin of the cluster. Thermometer / was
inserted beneath the frames through the collar, as is described above.
Its purpose was to record the temperature of the air below the cluster
and which was likely to be affected by currents from the entrance.
Its bulb was directly below the central frames. The first five ther-
mometers extended about 7 inches below the cover. The outside
thermometer, o, was suspended close to the hive in such a way as to
register the temperature of the air which surrounded the apparatus.

LOCATION OF APPARATUS.

The apparatus was installed in a slied on a third-story back piazza
in southwest Washington, as is shown in figure 2. While the shed
afforded shelter from storms, which was necessary for the protection
of the apparatus and in taking observations, windows and door were
left open, making the conditions relatively like out of doors. The
shed was on the south side of the building.

In July, 1908, it was necessary to transport the experiment to
CoUege Park, Md. This, however, was found not to have affected
the results. The apparatus was arranged in a situation comparable
to the shed in Washington.

CHECK COLONY.

Besides tlie colony on the scales, in which the thermometers were
suspended, a check colony m a hive with glass top and bottom was
set up close by. The hive was constructed with a glass bottom board,
and a wooden shield to cut out light. The cover was also of glass
sealed to the hive, on top of whicli were several thicknesses of felt
paper and an ordinary hive cover. By removing the bottom shield

6 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

and the to]) ])r()tocti()n it was p<>ssil)lc nt any time of day or night
to look l)etweeii the combs at the chister. These protective cover-
ings were applied so as to be removed with the mmimiim jar. At
night, or even in the daytime, by means of a reflector, lantern light
could be thrown up between the frames. In this way the writer
was able to watch from day to day the shifting of the cluster and
the reaction of the bees to their environment and to compare this
with the readings of the thermometei-s in the hive on the scales. It
was necessary to maintain this check only during the winter period.

METHODS OF OBSERVATION AND RECORDING.

Since none of the instruments recorded automatically, it was nec-
essary to make frequent readings of both the weights and tempera-
tures. The experiment proper lasted from October 22, 1907, to
September 26, 1908. The first colony, used to prepare the combs,
was also under close observation, so that the whole period of experi-
mentation was almost a year. Readings were taken at least every
hour throughout the working day. Whenever the hive was manipu-
lated, or when peculiar meteorological conditions prevailed, readings
were taken half hourly, or even quarter hourly. On the average of
about once in three weeks, by means of assistance, it was possible to
take consecutive hourly readings for a period of two or three days.
In this way practically the whole activity of the colony for a period
of a year was recorded. During the summer months the readings
usually covered a period of 14 hours daily.

The temperatures were read to fifths of a degree. Weighings
were made to 10 grams. Every alteration or manipulation of the
colony was recorded. Hourly changes in the weather and activity
of the bees were also noted.

The readings were recorded on 12.5 by 20 cm. cards, the size
standard to the office note file. Later from these tables the curves
of the temperature and weights were plotted on millimeter cross-
section paper, one sheet to a month. The method of plotting is
obvious from examination of the several curves herein presented.

THE CONSUMPTION OF STORES IN WINTER.

At the outset of the investigations it was hoped by means of deli-
cate scales, which have been described, tliat sufficiently accurate
weighings could be made to show whether there is any correlation
between the loss in weight and the temperatures of the cluster in
winter. For mstance, it was desirable to know whether there is any
relation or rhythm in the consumption of stores to changes in tem-
perature due to metabolism. It has not been possible to detect any
such relations. Nevertheless several significant facts concerning the
consumption of winter stores have been discovered.

THE TEMPERATURE OF THE BEE COLONY. 7

The rate of consumption of stores, as is shown in figure 4, exhibits
a relatively constant decrease from month to month. At the begin-
ning of the season, l)efore the cluster was well established, when bees
were more active and before settled winter weather, food consump-
tion was greater than in midwinter. As the season progressed, during
February, for instance, consumption slackened. There are several
factors which may account for this. In the first place, as the winter
advanced there were fewer and fewer bees to be fed. The winter
was also less severe, and consequently less generation of heat was
necessary.

Humidity is another factor which noticeably influenced the daily
weights for a considerable part of February. This also occurred

OCT

A/Ol^

£>/^0.

c-^^54<r

/^£&.

At<^.

eooo

y^e-*o

^^3o\^^^

sooo
^■^ooo

^

sS.s-^0

'^s/o\.

J&fO-

§

\ JOOO
^ .POOO

^^NsJii"^"^

^■«cw^

^"^'^^^cxto

/eoo'^

/sso

/ooo
o

Fig. 4.— C.raphio representation of the loss in weight of the bee colony from November 6 to March 7,
due to the consumption of stores.

periodically in other months. Although condensation tended to
prevent a drop or even to raise the curves during a period of bad
weather, as will be shown below, the increased weight due to the con-
densed water vapor could neither be permanent nor affect the total
loss of weight durmg so long a period as a month. Whatever water
condensed during inclement weather would evaporate during the
following days of fair weather. Thus, while the scales might reg-
ister an increase during bad weather, consumption of stores was
actually going on all the time, but could not be detected in the
weights until fair weather had dispelled the moisture. Conse-
quently the records of single days are less significant than the aver-
ages of a month or of the season.

8

BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

There was, liowever, a gradual and constant lessening of the daily
consumption of honey, as is apparent in Table I, which presents the
monthly and average daily figures. From this table it will be seen
that while in November the average (hiily consumption was 53.2
grams, m Februaiy the average was but 30 grams a day. For the
entire winter 43.5 gi-ams of honey were consumed, on the average,
daily.

Table I. — Monthly and average daily consumption o/storc.t by nitilering bees.

Time.

Weight
of stores.

Monthly loss.

Average daily
loss.

November (Nov. 6, 9 a. m., to Dec. 1,9 a. ra.— 25 days). .
December (Dec. 1,9 a. m., to Dee. 31, 9 a. m.— 30 days). .

Grains.
6,640
5,310

5,310
• 3, 820

Grams.

1,330

1, 490

1,350

840

Pounds.
2. 932
3.284
2.976
1.852

Grams.
53.2
49.6
42.2
30.0
43.5

Grains.
821

Jamiary (Dec. 31. 9 a. m.. to Feb. 1, 9 a. m.— .32 days)

3,820
2,470

765

Febniary (Feb. 1,9 a. m., to Feb. 29, 9 a. m.— 28 days).. .

2,470
1,630

Total loss for 4 months

5,010

11.045

Average daily loss

671

Table II. — Daily loss in weight of colony of wintering bees.

Date.

Loss in

Date.

Loss in

Date.

Loss in

Date.

Loss in

grams.

grams.

grams.

Nov. 11

120

Dec. 10

+30

Jan. 10

70

Feb. 10

0

12

10

11

70

11

40

11

20

13

50

12

70

12

+10

12

20

14

70

13

60

13

30

13

0

15

50

14

20

14

50

14

+40

16

80

IS

25

15

60

15

+20

17

90

16

25

16

40

16

130

18

60

17

60

17

50

17

20

19

10

18

40

18

50

18

40

70

19

40

19

40

19

+40

Although the foregoing figures represent the usual daily conditions,
they do not by any means represent the actual daily consumption.
As will be seen in Table II, there was no such degree of constancy as
is represented by these averages. Taking the 10 days at the middle
of each month, it is possible to represent prevailing conditions for
that month. Thus the data of Table II are a fan- representation of
the actual variations as they occurred durmg the winter. It wUl be
seen in this table that the daily variation in weight is all the way from
a loss of 130 grams m some cases to no loss whatever or even an in-
crease of 40 grams. Therefore it is hardly possible to assume that the
weights of the entu-e hive will throw any light on the amount of
honey consumed in a single day.

This increase in the weiglit of the hive during bad weather is a
fact which, so far as the author is able to learn, has not heretofore

THE TEMPERATURE OF THE BEE COLONY.

9

^j(^AC3/

/=£-ff./

/x»-?

/=■£&. 3

s,

^.

^

i \

\

1 ll

1

%\

attracted attention. It can not be said in any wise that this is an
increase in the amount of stores. The phenomenon usually accom-
panied wet weather or fog and must be attributed to condensation
of moisture. In the check hive
moisture was frequently seen col-
lected on the glass top and even
on the frames and bees, but there
the conditions were perhaps less
normal than in the experimental
colony. Root ^ says that he has
seen confined moisture cause
icicles to form ui the hive. The
condensation may become so
great m extreme cases as to
cause the bees to freeze together
in a solid block when chilled down
by severe cold. (Root, pp. 332-
334.)

Honey is well known to be
hygroscopic, and if j)ut into an
ice chest or a damj) cellar, it
takes up moisture. Extracted
honey has also been observed to
accumulate enough moisture to
dilute it considerably. In the present case the hygroscopic property
of the honey can not be held wholly responsible for the increased
weight, although it may have contributed. Following an increase
of this kind, as has been mentioned, there was a marked decrease

with the coming of
fine weather and dry-
ness. For illustra-
tion, the increase of
40 grams on Febru-
ary 1 (fig. 5) occurred
during the early part
of the day, when it
was raining. That
afternoon and the
following day there
were fair weather and
wind. Then there came a marked decrease in weight, which not
only compensated for the increase during the storm, but also showed
that stores had been consumed constantly, although the weights

1 A B C and X Y Z of Bee Culture, 1908 ed.
38957°— Bull. 96—14 2

Fig. 5. — Curve showing changes in weight of the bee
colony from Jan. 31 to Feb. 4.

A/Ol^.^O

/V27/<^/

A'OI/.^^

/*/OK^3

A^

";s

f

1

y

1

\

seoo

Fig. 6. — Curve showing changes in weight of the bee colony from Nov.
20 to Nov. 23.

10 BULLETIN 96, U. S, DEPARTMENT OF AGEICULTURE.

failed to demonstrak' it at the time. Tins same point is illustrated
by the fi2:ures presented in figure 6. Such conditions suggest the
compUcations which arise in attempting to correlate the colony tem-
perature mth the consumption of honey.

GENERAL PHENOMENA OF THE CLUSTER IN WINTER.

During the winter the be(>s are relatively quiet; the cluster expands
and the bees fly only in th(^ warmth of the warmest days. The heat
maintained in the cluster has a general relation to the prevaiHng
temperature of the air.

This relation of the cluster temperature to air temperature is
especially evident in a comparison of the maximum and minimum
temperatures of th(> several thcuinometers of the hive with the tem-
perature at the outside thermometer, o. The daily maxima and
minima were practically synchronous for all of the thermometers
with the exception of c, which usually had its maximum when the
temperatures registered by the other thermometers were lowest.
Conversely, the minimum of c occurred when the outside thermometer
and the others in t^e hive were at their highest points. This will be
(explained in detail under a following caption. With the exception
of c, then, and for the particular conditions under which this colony
was kept, the minima occurred daily some time between 6 a. m. and
12 m., but usually about 8 or 9 o'clock. The maxima occurred daily
in the afternoon, usually between 2 and 4 o'clock.

While c registered the highest in cold periods, the temperature
recorded by the other thermometers showed a similarity with the
prevailing temperature of the air. Thus, in periods of cold, as for
example in December, the thermometers in the hive as a whole
registered lower than they did in warm periods. In warm periods,
when the bees are able to expand the cluster and move about, the
maximum cluster temperature lacked but a few degrees of the
maximum summer temperature. This is repeatedly shown in
figure 7; and in March, on a warm day, the temperature reached the
extreme of 33.2° C. (91.76° F.). The temperature of the cluster did
not fall below 17° C. (62.6° F.), and usually the bees did not permit
the temperature of the cluster to fall below 20° C. (68° F.).

The amplitude of the fluctuations between the maximum and
minimum temperatures showed a close relationship to the external
conditions. In the center of the cluster, for instance, c registered
much more constantly than the thermometers in the outside layer of
the cluster. The daily oscillations of c were usually not greater than
1 to 5 or 6 degrees Centigrade. On the contrary, in the case of the
other thermometers in the hive wliich were more affected by the rise
and fall of the temperature out of doors, the amplitude of the oscilla-
tions was as great as 3 to 20 degrees Centigrade. The center of the
cluster, therefore, shows more clearly the activities of the bees. The

THE TEMPERATURE OF THE BEE COLONY.

11

active portion of the cluster has a higher and more uniform tempera-
ture than the other parts, while the outside layers are subject more
directly to the fluctuations of the winter weather. Most of the fol-
lowing study of the winter conditions of the beehive will be based on
the records of the center of the cluster.

It would naturally be expected that the heat radiating from the
bees would tend to delay the effects of the penetration of the cold of
the outside air on the cluster. In other words, it might readily be
expected that the clustt^ thermometers would reach their maxima and
mmima later than the outside thermometer. However, this occurred
seldom and only in severe weather, when the changes were rapid and
considerable. Even then there was a delay of only an hour or two

at the most. This
again suggests the
sensitiveness a n d
the responses of the
cluster to the
changes in the ex-
ternal air. The ad-
aptation of the bees
to changes in the
atmospheric condi-
tions wall be more
apparent when de-
tails are considered.
As has been sug-
gested above, there
was a tendency for
the cluster gradu-
ally to maintain a
liigher temperature
as the season ad-
vanced toward spring and the beginning of egg laying. The schematic
curve, figure 7, presents grapliically the conditions of temperature at
thermometer c throughout the winter. It will be noticed that dur-
ing the month of November, when the bees were less definitely and
constantly clustered, the amplitude of the daily variation and the
general temperature of the cluster were higher than in the succeeding
months. Tliis is also evident in the fact that the curve of the ther-
mometer c at this time of the winter tended to follow the curve of
the outside thermometer o to some extent. In December, however,
there was a change in the course of the temperatures at c, in response
to the change in outside conditions. The conditions remained more
nearly constant from this time until egg laying commenced in the
spring, except that as the weather tended to warm up at the approach

Fig. 7. — Schematic curve sliowng cluster temperatures of the bees dur-
ing the winter and after brood rearing began.

12 BULLETIN m, V. S. DKI'AIITMENT OF AURICULTUKE.

of si)iin<i' the moan oi tho clustor IcMuporaturo ulso raised. Finally
wiuMi Iho (lays had oonsidorably longlheued and wore relatively
warm, tlu> anipUtiule of the cluster variations increased, as is shown
in the schema tic curve (lig. 7). When the summer season for the
bees began, accompanied by the beginning of incubation, the tem-
perature of the center of the cluster rose to 34° C. (93.2° F.) or 35°
C. (05° F.) and continued practically at this level. For the winter,
then, it might be said in a general way that the temperature prevail-
ing for several days is in a measure an index of (lie temperature of
the cluster.

TEMPERATURE BELOW FRAMES IN RELATION TO OUTSIDE AIR.

The tliermometer f, situated below the bottom of the frames and
cluster, as is shown in the general views of the apparatus (figs. 1 and
2), registered the temperature of the air at the bottom of the frames.
It should have shown, if they were present, the effects of the cluster
on the temperature of the air below the frames. It might be expected
that the presence oi the bees would have raised the temperature of
the air in this part of the hive. For comparison with the other tem-
peratures, thermometer o was hung in the shed in which the experi-
ments were conducted, and registered tlie temperature of the air
which enveloped the hive. Comparison of the readings of thermome-
ters /'and o reveal some significant facts not altogether in accord with
tlie general belief of beekee[)ers.

During the winter as a whole these thermometers registered almost
identically. Slight variations occurred, but only for a few hours at a
time, and may be attributed to minor inlluences of the cluster, to
peculiar atmospheric conditions, to drafts, and to the agitation of
the bees. It should also be noted that the air which came in the
entrance entered from outside the shed and the temperature of this
air may not have been exactly that recorded by the thermometer o.

During the period of most protracted cold, from January 23 to Feb-
ruary 1 , when the mitside air ranged about 0° C. (32° F.), thermometer
/'followed the outside temperature closely, and the coui'se of the two
curves is practically the same. In some cases, as for instance on
January 26, thermometer /'was slightly lower than the record of the
outside air, which may possibly be exj)lained by lack of ventilation or
stagnation of the air of the liive. Tlie lowest recorded outside tem-
perature was —10° C. (14° F.). Since it was impossible to read
these low temperatures on instrument/, and since the two curves are
parallel so far as records were possible, it may be assumed that ther-
mometer /"would have registered almost the same as thermometer o.

During the warmest days and nights the recorded temperatures
were the same. The maximum for the wanter period came on March

TTTE TEMPERATURE OF TTIE BEE COT.ONY.

13

15, when the outside thermometer readied 22.6° C. (72.68° F.). In
all the other winter months there were days when the thermometers
registered only 2 or 4 degrees less.

In conclusion it may be said that throughout the season the tem-
perature below the frame was practically the same as that of the out-
side air. Of special significance is the fact that the daily extremes,
the maxima and minima, no matter what were the variations at other
periods of the day, were usually identical. From these observations

Fig. 8.— Curves showing relation of temperature of center of bee cluster to outer temperature, Teb.

1 to 10.

it would appear that the contraction of the entrance and the tight
bottom board were not of much service in protecting the colony from
cold. Colonies without bottom boards have frequently been known
to survive extreme winter cold. It may be, however, an advantage
to a colony to be protected from the sweep of violent winds; but
there is no evidence that tliis colony appreciably warmed the lower
part of the hive in which it was wintering. Under such conditions
the bottom of the cluster is bathed in an atmosphere of thB same
temperature as the outside.

14 BULl.ETTN 00, IT. S. DEPARTMENT OF AGRICULTURE,

COMPARISONS OF TEMPERATURES OF THE CENTER OF THE (LUSTER
AND OF THE OUTSIDE AIR.

The curves have revealed no more strikhi<; results than the relation
observed between the temperature in the center of the cluster, c,
as compared with the temperature of the outside air, o. These
curves (fi^. 8) at times show a peculiar inverse relation; for instance,
when the thermometer out of doors registered low, below zero, the
thermometer in the center of the cluster registered liigh, and vice
versa. It should be observed that the maximum within the cluster
occurs practically simultaneously with the minimum outside, and
vice versa. Even minor changes outside are accompanied by cor-
responding inverse fluctuations in the cluster. The responses of the
cluster to the outside temperature were shown particularly by the
thermometer which recorded the temperature of the center of the
cluster, c.

Up to the day of the first egg laying in the spring, March 9, the
general courses of e and o continued relatively constant. But with the
commencement of egg laying c changed its trend. The temperature
of the brood cluster then became more and more constant, as may be
seen in the results of the summer observations.

At first glance these curves might be interpreted as independent
of each other, that the outside atmosphere has no effect on the center
of the cluster, that it does not penetrate and modify the readings of c
as it appears to have done in the case of the temperatures in the margin
of the cluster. In all probabiUty c more nearly represents the
activities of the bees than do the other temperatures; but there is a
relation of c to o. It might be supposed that the reaction registered
by c is deferred for a period of hours and consequently appears at a
time when o has changed. For instance, corresponding to the
minimum of o on the 4th of February, the minimum of c came nine
hours later. If this is due to a delay or "lag," maxima and minima
in some cases are delayed for 24 hours or more. But this can not be;
there are many minor variations which appear on the curves, and
wliich are synchronous. Were there no relation of c to o these minor
variations would either not have appeared in c, or, more especially,
they would not have occurred simultaneously with a minor fluctua-
tion in the outside temperature. It is therefore impossible to explain
the phenomena on the ground of retardation (lag), for in that case it
would be far more constant than is e\'ident.

Related to the assumed explanation by delay or "lag," humidity or
condensation, convection, radiation, and conduction might be
assumed to be factors involved. The experimental colony furnishes
no data for a consideration of humidity or condensation. The factors
of convection, radiation, and conduction can not be conceived as slow
enough to retard c from 9 to 24 hours nor would it account for its minor.

THE TRMl'KRATURE OF THE BEE COLONY

15

synchronous variation. Without doubt of tlu'sc tln-ec factors the
loss of heat from the cluster by convection is sufficient to counteract
the hypothesis of the lajji;. Coupled mth this the other factors would
be expected to participate. The convection is also modified by the
generally known contraction and relaxation of the cluster, referred
to elsewhere.

These })hysical phenomena are evidently unsatisfactory as an inter-
pretation from this standpoint of the lag. Thorough comparison of
the charts fails to provide suitable material for conclusions as to the
cause.

Table III shows the relative increase of temperature in the cluster
corresponding to the progress of the winter season, while Table IV
shows the montldy maximum and minimum temperature of the center
of the cluster during the period from November 9 to March 9.

Table III. — Relative increase of temperature in the bee duster corresponding to the
progress of the winter season.

Range of temperature.

November, beginning of winter conditions

December

Jan. 1 to 18

Jr.n. 19 to 31

February

Mar. 1 to 9

When brood rearing is establislied

°c.

20 to 24

20 to 22

22 to 25

23 to 28

24 to 30

27 to 32

34 to 35

"F.
68. 0 to 75. 2
68.0 to 71.6
71.6 to 77.0
73. 4 to 82. 4
75. 2 to 8P. 0
80. 6 to 89. 6
93. 2 to 95. 0

Table IV. — Monthh/ maximum and minimum temperature of the center of the bee cluster
during the -winter period, Nov. 9 to Mar. 9.

Temperature of clu.stcr.

Mondi.

Maximum.

Minimum.

27° C

17° to 18 2° C

80.60° F

02. ('0° to 64 76° F

Deceml)er

18.5° and 31.3° C.i

r5.30° and 88.34° F....
.30 2° C2

18 1° C

Janaary

64.58° F.
19° C

S(;.36°F

66.20° F.

February

32° C.3

21° C

89.60° F

69 80° F.

Mar. 1-9

33.2° C.4

27° C

91.76° F

80.60° F.

1 On a very warm day, Dec. 28.

2 This occurred on two occasions, Jan. 14 and 30, at 8 a. m., when the outside temperature was 4° C. or
more below freezing;.

3 Approximated several times when outside temperature was below freezing.
■• Occurred after a warm day; approaches summer conditions

EFFECTS OF MANIPULATION ON THE CLUSTER.

Good beekeepers know that it is not well to open a hive in winter,
but perhaps few realize the resulting effects on the colony. In
Washington there are days in every winter month wliich are suf-
ficiently warm to permit opening a hive without chilling the bees.
It was necessary, partially in order to observe the effects on the

16 BULLETIN 9fi, IT. S. DEPARTMENT OF AgrIGI^LTUBE.

colony jiiul partially; to knoW i\i'eit Condition, to op.en the hive under
experimentation. The results recorded by the thermometers on all
of these occasions are pronounced. In the course of the observations
on this colony it was found impossible to disturb the colony in the
slightest degree, even to remove and replace a thermometer, to
jar the colony, or to puff smoke in at the entrance, without notice-
ably affecting the temperature. These eft'ects, as in the case of open-
ing the hive, were not always temporary, but sometimes lasted for
hours. Any disturbance resulted in an almost immediate rise in the
temperature, and was appreciable throughout the cluster.

On March 12 the colony was opened for 15 minutes at 1 o'clock
in the afternoon. The thermometers throughout the hive and even
the one below the frames to some extent registered an immediate
rise in temperature. When the liive was closed the cluster was soon
reestablished but it was several hours before the temperature in the
margins of the cluster became normal. On the interior of the cluster,
however, the excitement and its effects were not so soon overcome.
The curve for c shows that not until the next day did conditions ap-
proximate normal ; the effects were appreciable even the day following
the opening of the hive.

These results agree with the experience of many practical bee-
keepers, who consider it unadvisable to open their liives during the
winter.

BEHAVIOR OF THE CLUSTER IN WINTER: OBSERVATIONS ON THE CHECK

COLONY.

By means of the check colony with glass top and bottom, described
on pages 5-6, it was possible to watch the movements of the bees
throughout the winter at any time of day or night.

Various theories have been advanced by beekeepers to account
for the behavior of bees in winter, but the writer is not aware that
they are based on continuous and close observation. For instance,
it has been maintained by some that bees semiliibernate ; by others
it is affirmed that there is at intervals a general warming up of the
colony in order that it may feed. The theory is that at stated periods
bees generate enough heat to enable them to brave the cold and to
expand the cluster sufficiently to enable them to reach fresh stores.
It is not necessary to multiply theories on the condition and activities
of bees in winter.

In a pre\dous portion of the text the relation of the temperatures
of the cluster to the temperature of the outside air has been suffi-
ciently considered. It remains now to describe the activity of the
bees as seen in the glass check hive. In some respects the move-
ments (^r the reaction of the bees, and more particularly of the cluster
as a whole, to the stimuh of changes in the atmospheric conditions
was rather pronounced.

THE TEMPERATURE OF THE BEE COLONY. 17

In watching this colony it was found that the density, and conse-
quently the shape of the cluster, varied from day to day. When the air
outdoors was warm, the chister expanded; with cold, it contracted.
The expansion usually did not cause the bees to cover more frames,
but caused them to cover more completely those frames which they
were occupying. Thus the expansion was usually downward toward
the bottoms of the frames and in the direction of the entrance.
With cold, the bees receded from the bottoms of the frames and from
the top bars.

At all times tlie colony was sensitive to the slightest jar. The bees
were also especially sensitive to the light which burst in upon them
whenever the covering of the glass top was removed. If the hand
were passed over the glass, bees would fly toward it as if to sting.
This was noticed no matter how cold the day and shows that the
colony, and particularly the outside of the cluster, is far from torpid,
inactive, or semiquiescent. At practically all times there were bees
movmg on the outsitle of the cluster or on the top bars of the frames.
Wlienever the hive warmed up m the sun, although there were no
bees flymg, this was evident. There can be no question, therefore,
of the alertness and activity of a colony in winter.

One of the most surprising observations was the apparent inter-
change of bees from the inside of the cluster with those on the outside
of the cluster. As the writer watched the cluster, the head of a bee
would gradually appear from below the bees forming the shell of the
cluster. Finally this bee emerged and took her place with the others
on the outside. Similarly, bees were frequently seen to disappear
into the mass. The behavior was in no way general, but apparently
was going on constantly and gradually. The phenomenon was
repeatedly observed under all manner of conditions and at different
times of day and night. By carefully arranging the covers, so that it
was unnecessary to remove them, and thus cause a j ar, it was proven
that this behavior is normal and not the result of a disturbance of
the bees. It must be concluded, therefore, that in this way the same
bees may not be exposed to the outside cold for a long period. So
long as they are able to keep up their own body temperature they
remain outside, but when chilled they pass into the interior. Thus
there must be a continual interchange of bees from the outside to the
inside. Were it possible of observation, there would doubtless be
found a relation of the interchange to the meteorological conditions.
In cold weather the interchange may be expected to be greater.

In severe weather the bees were especially compact and their
arrangement definite and constant. They were arranged side by
side between the tops of the frames, with their heads downward. At
the lower part of the cluster they were also arranged head down but
wi.th a little less regularity. It is difficult to see just what this means.

18 BULLETIN Ofi, U. S. DEPARTMENT OF AGRICULTURE.

As further evidonco that tlie colony is not torpid in cold weather,
some of the otiier activities ol)served will be of interest. Durhig the
day, particularly, the bees were seen grooming and combing one
another, feeding, and fanning at the outside of the cluster; and when
the light was achuitted to the top, they sometimes flew up as if to
sting. It should also be stated that on nights of the most severe
weather the bees in both this check colony and in the experimental
colony were heard faintly and intermittently buzzmg. This buzzing
was oven more noticeable on cold nights than on warmer ones. A
peculiar trembling of the bee such as is seen in summer was not
infrequently noticed. All of these activities are commonly observed
in summer, but heretofore have not been thought to occur in whiter
and spring before the colony is able to fly forth.

It is probable that the lieat of the sun has no slight influence on
the cluster. At least in the clieck colony under observation it was
evident that the cluster sought the sunny side of the hive, the front
al)()ve tlie entrance, where from 10 or 11 o'clock in tJie morning until
sun(h)wn the sun shone on tJie hive.

TEMPERATURE ACCOMPANYING THE LAYING OF THE FIRST EGGS.

With the laying of the first eggs in the spring, which marks the
beginning of summer activity, striking changes occur in the behavior
and temperature of the cluster. The central thermometers h and c
were particularly aft'ected. Upon opening the hive March 12 eggs
less than three days old were discovered. Up to March 9 c had
usually contimied its winter course inversely to o, as is described and
illustrated above by figure 8. But after March 9, when the first
eggs were seen, the course of c changed and the inverse relationsliip
was no longer apparent.

In order to explain the change ui the course of c in relation to o,
the behavior of the bees at egg-laying time must be considered.
During the winter, whde fresh air is necessary, there is no such need
of it as when the eggs, or more particularly the brood, appear.
Moreover, for incubation and for brood rearing a much higher and
more constant temperature is needed. The effects of drops in the
temperature of the outside air must be overcome. In preparing
room for the laying of the queen, the zone for the brood nest is
established, which is an important factor in the change in the course
of curve c. All of these things appear immediately in the curve
at the time of incubation. Formerly, when the bees went forth on a
warm day there was a drop in c\ now the trend of c is slightly upward
durmg the warmth of the day corresponding somewhat with the
warmth outside. Flight occurs nearly every day.

It is the belief of many beekeejjers who winter their bees in cellars
that tt)o high a temperature is likely to cause uneasiness and brood

THE TEMPERATURE OF THE BEE COLONY. 19

i-earing. Root (1908) calls attention to the necessity of Jiiaintainiiig
a temperatuie of not more tlian 45° F. (7.22° C.) at the approacJi of
spring. The \M'iter is not aware that any systematic stnciy of the
t(smperatures of bees in cellars has ever been made, so that it is
impossible to say how the temperature of the cluster would compare
with that of the colony under experin.ientation. The prevailing
outside temperature, however, in the present experiment was found
to be about 45° F. (7.22° C.) for several days previous to the laying
of tlie first eggs, March 9.

At any rate in this experiment it appears that a temperature of
45° F. (7.22 C), with, an occasional maximum outer temperature of
8° to 11° C, is closely associated with the beginning of egg laying.
But there are probably other factors of importance, particularly the
matter of food. In establishing the experimental colony late in the
fall, it was impossible for the bees to store any poUen. In the spring,
however, for a week previous to egg laying they were ;;een gathering it.
This might be expected to be an important stimulus to egg laying,
and the bees could not rear brood until some could be gathered.
While there appears to be a close relation between stimuli, tempera-
ture out of doors, and pollen gathering to the laying of eggs, details of
the phenomena can be worked out only on a larger number of colonies
under experimental conditions.

Another noticeable phenomenon which occurred at this time was
the equalization of the temperature throughout the cluster. This
might occur earlier in colonies protected from the winds and in sunny
locations and later in colonies less favorably situated. If, however,
upon experimentation this should be found to be one of the funda-
mental stimuli to egg, laying, it would in a measure explain the fact
that eggs do not always appear at the same time in all of the colonies
of a bee yard. Another factor would be the strength of the colony
and the resulting heat which it could produce and conserve. Th se
results of the present investigation suggest groat possibiHties for dis-
covering the stimuli w^hich regulate the beginning of egg laying in the
spring and wdiich might influence the periodicity of brood rearing
during the summer.

So far the consideration has been largely of the period in which
eggs were laid and which preceded directly the beginning of incubation
or brood rearing. It will be seen, therefore, that this time is in a sense
transitional from the winter condition to the summer season, the
topic which wHU next be considered.

TRANSITION FROM WINTER TO SUMMER CONDITIONS.

The phenomena mentioned in the preceding caption w^hich accom-
panied the la^,'ing of the first eggs marked the beginning of the transi-
tion from uinter to summer conditions, but this transition was not

20 BULLETIN 96, U. S. DEPARTMENT OF AGRICULTURE.

completed until brood rearing was well established. With the estab-
lishnKMit of brood rearing, the changes which manifested themselves
with the first eggs became intensified. The course of the temperature
recorcUnl at c became unlike that which was observed in the winter
and was influenced more directly by the outside temj^erature. The
influence of the outside temperature became less and less marked, as
is shown from the fact that the oscillation of c became less and less,
the temperature in the center of the cluster became more constant,
and the temperature throughout the hive became more equaUzed.
As was stated, the turning point came on the 9th of March, but it was
a little more than two weeks, about the 24th or 25th of March, before
the colony really assumed normal summer temperature condition.
Once this was gained, the temperature, particularly of the center of
the cluster, remained relatively constant until fall. This transition
period of two weeks was characterized by several features.

There was an increase of temperature both in the colony and out of
doors. Out of doors the maximum ranged between 12° and 18° C.
(53.6° to 64.4° F.), but even more favorable weather followed the
establishment of brood rearing and the maximum ranged from 18° to
25° C. (64.4° to 73.4° F.). To a certain extent the temperature of the
colony was raised like that of the outside temperature. The increase
was general throughout the colony and must be attributed to the
need of more heat for brood rearing, more ventilation, and the general
increased activity of the bees. At this time h and c ranged constantly
between 33° and 35° C. (91.4° to 95° F.), which will be seen to be prac-
tically the range throughout the summer.

In a word, the transition from winter to summer conditions was
accomplished in a surprisingly short time. Accompanying incuba-
tion and brood rearing the temperature was gradually raised and
became equalized through the hive, and once well established was
maintained during the summer. Although the transition was rela-
tively abrupt, it would be expected to vary with the colony and
perhaps be prolonged in unfavorable weather.

GENERAL PHENOMENA OF THE SUMMER TEMPERATURE.

The constancy and equalization of the temperature and the range
of 33° to 35° C. (91.4° to 95° F.), which characterized the close of the
transition from winter to summer conditions, characterize equally
well the prevailing summer phenomena. So constant were the tem-
peratures in summer that their peculiarities may be briefly sum-
marized. Few external factors influenced the hive temperature, and
these affected it but slightly. In the original plan of the experiment
it was hoped that it would be possible to discover whether there is
any correlation between honey flows and temperatures ; but inasmuch
as the season was excessively dry and the flowers secreted no nectar

THE TEMPERATURE OF THE BEE COLONY. 21

for weeks at a time, this phase of the experiment could not be canied
out.

RELATION OF C TO THE OUTSIDE TEMPERATURE.

Whatever is said of c in the following paragraphs applies equally to
h, and practically as well to all the thermometers in the hive.

Although the temperature at c coursed constantly in the opposite
direction to o during the winter, there is no appreciable correlation
between the temperatures in the summer. It might be said of the
hive that the temperature as a whole was independent of external
conditions. A few exceptions to this will follow, however. During
a period of stormy and cooler weather, for instance, although there
were slight changes which will be discussed later, the temperatures
were largely unaffected. Moreover, since the oscillation of c was
slight, as will be explained, there was little relationship between the
temperature of the center of the cluster and o.

THE MAXIMA AND MINIMA OF C IN RELATION TO O.

The daily oscillation between the maximum and minimum of c
was usually less than 1° C. (1.8° F,), and in many instances it was but
one or two tenths of a degree. On the whole the temperature in the
brood nest is remarkably constant, ranging between 34° and 35° C*
(93.2° to 95° F.).

Even with this slight fluctuation there was perceptible on many
days a maximum and mmimum for c, and particularly for the other
hive thermometers which perhaps were the most influenced by ex-
ternal conditions. It may be said that, roughly, the maxima and
minima occurred within two hours of the maxima and minima of o,
but since in some instances this happened previous to the maximum
and minimum out of doors, the warming up of the colony due to the
increasing activity of the bees must have had its effect.

To show how closely the maxima of the thermometers in the outer
parts of the cluster ultimately approached the readings of the central
thermometers, it may be said that while in April the maximum of
the outer thermometers in the hive was 19° C. (66.2 F.), in the fol-
lowing months it rarely fell below 34° C. (93.2° F.). In September,
however, with the general cooling of the atmosphere, it fell to 28° C.
(82.4° F.). This showed the tendency at the close of the experiment
for the colony to approach winter conditions. The facts show again
the unity or equalization of the temperature throughout the cluster,
which in the brood-rearing season ranges between 34° and 35° C.
(93.2° to 95° F.). The maxima and minima are shown in Table V.
The range of the oscillation shows the constancy of the temperature
during the height of the season and the greater fluctuations in spring
and fall.

22

BULLETIN 96, U. S. DEPARTMENT OF AGKICULTUKE.

Table \'.— Maximum and minimum temperatures of the center of the cluster during

summer. Thermometer C.

Month.

Ml ximum.

Minimum.

Approximate
range.

' a

35.4
36.0
35.5
35.0
35.8
34.8

o p

95.7
9f).8
95.9
95.0
96.4
94.6

° C.
31.6
33.8
33.6
33.2
33.8
28.0

° F.
88.9
92.9
92.5
91.8
92.9
82.4

" C.

4
2
2
2
2
7

" F.
7.2

3.6

3.6

July

3.6

3.6

12.6

FLUCTUATIONS IN THE HIVE TEMPERATURE AND THE CAUSES.

It luis iilready been said that the fluctuations in the hive tempera-
ture wore shght and that hot days and mnds had very shght effect
on the cluster tempei-ature. There are some minor fluctuations due to
internal and external disturbances which caused decrease or increase
in the hive temperature.

THE EFFECT OF "ORIENTATION" OR "PLAY FLIGHTS."

Every beekeeper is famihar with the "play flights" of young bees
about noon on warm sunny days. These are generaUy behevcd to
be ''orientation flights," in which the young bees fly forth in circles
and with head toward the hive in order to learn its location. During
the period of resumed brood rearing in August these flights occurred
every few days in the experimental colony. At such times ther-
mometer readings were taken at short intervals. Instead of causing
the heat of the hive to increase these flights first caused a decrease,
then a slight increase. Table VI presents figures for a typical observa-
tion, made after the bees had been confined to the hive by inclement
weather for three days.

Table VI. — Ejfects of "' orientation Jlighls" of bees on the temperature of the hire.

Thermometer.

Au?. 28.

0.

6.

c.

d.

e.

/.

0.

6a.m.i

7 a. m

' C.
34.0
34.0
34.0
34.0
34.0
33.8
33.8
34.0
34.0
33.8
34.0
34.0
34.0
34.0
34.0

" F.

93.2

93.2

93.2

93.2

93.2

92. 84

92 84

93.2

93.2

92. 84

93.2

93.2

93.2

93.2

93.2

° a

34.4
34.4
34.2
34.0
34.2
33.8
34.0
34.0
34.2
34.0
34.0
34.0
34.2
34.2
34.4

° F.

93.92

93.92

93. .56

93.2

93.56

92. 84

93. 2

93.2

93. n6

93.2

93.2

93.2

93.56

9.3.56

93.92

° a

34.4
34.4
34.2
34.3
34.3
33.8
34.0
34.0
34.2
34.0
34.0
34.2
34.2
34.2
34.4

° F.

93.92

93.92

93. r.6

93.74

93.74

92.84

93.2

93.2

93.56

93.2

93.2

93. .^)6

93.. 56

93. .56

93.92

" C.
34.4
34.0
34.0
34.0
34.0
33.8
34.0
34.0
34.0
33.8
34.0
34.0
34.0
34.0
34.2

° F.

93.92

93.2

93.2

93.2

93.2

92.84

93.2

93.2

93.2

92.84

93.2

93.2

93.2

93.2

93.56

° C.
33.6
33.4
33.4
33.2
33.2
33.2
33.8
33.6
33.6
33.6
33.6
33.6
33.8
33.8
33.8

° F.

92. 48
92.12
92.12
91.76
91.76
91.76
92.84
92. 48
92. 48
92.48
92. 48
92. 48
92.84
92. 84
92.84

° C.
34.6
34.4
34.6
34.6
34.8
34.2
34.4
34.4
34.8
34.}
34.4
34.6
34.8
34.8
34.8

- F.

94.28
93.92
94.28
94.28
94.64
93. .56
93. 92
93.92
94.64
93. 92
93. 92
94.28
94.64
94.64
94.64

° C.
15.6
16.4
16.8
17.4
18.0
19.4
20.0
19.6
20.2
20.2
20.4
20.0
20.4
20.8
20.2

°F.

60.08

61.52

Sa. m.'

9 a. m

62.24
63. 32

10a. m

lla.m.3

11.30 a. m. ■«....

12m

1 p. m

64.40
66.92
6.8.0
67.28
68.36

2p. m.5

2.15 p. m

2.30 p. m."

2.45 p. m

3 p. m

4 p. m

68, 36
68.72
68.0
68.72
69.44
08.36

1 Cloudv.

2 Bees fly slightly.

s First good fly for three day.s.

< Quieted flight.

5 Bees fly freely again.

e Quiet again.

THE TEMPERATURE OF THE BEE COLONY.

23

It will be noticed tliat short flights were taken at 8 o'clock in the
morning when the thermometer c fell 0.2° C. At 11 o'clock the first
flight of importance occurred. Then there was another slight drop
in the temperature followed by a rise. At 2 o'clock there was a
similar fhght and change in the thermometer. In aU cases within
15 to 30 minutes the thermometer had regained its normal tempera-
ture. Whib the drop was actually slight, when it is remembered
tliat tlie daily fluctuation in the temperature was frequently but a
fraction of a degree, tlie decrease was relatively considerable. The
same effect was noticed in the spring and in the early part of the
season, when the bees first commenced to take field trips. This
coohng effect must be attributed to the rushing forth of the bees
from the cluster; in so doing they Hberate the confined heat of the
cluster. Another factor is probably the excessive fanning at the
entrance which usually accompanies these '' play" flights. When the
activities wane and the bees commence to return to the liivc, the
temperature resumes its normal condition.

A simdar decrease in temperature was common in the early morn-
ing when the bees commenced to leave tlie hive for tlie field. For
comparison with the foregoing, the readings taken in the early morn-
ing of August 3 and 4 are presented in Table VII.

Table Yll.—Eferts of early morning Jiight of bees on, ternperaiare of the hive.

Date.

Aug. 3
Sa. m

9 a. m

10 a. m

11 a. m

12 m

Aug. 4.

5a. ml

(ia. m

7a. m2

8 a. m ,

9 a. m

Thermometer.

°C.
34.0
33.8
33.9
34.0
34.0

34.4
34.4
34.0
34.0
34.0

°F.
93.2
92. 84
93.02
93.2
93.2

93. 92
93. 92
93.2
93.2
93.2

"C.
34.2
34.2
34.4
34.4
34.6

34.6
34.6
34.4
34.4
34.8

"F.

93. 56
93.56
93. 92
93.92

94. 2S

94.28
94. 28
93. 92
93.92
94.64

°C.
34.6
34.4
34.8
34.8
34.8

34.8
34.6
34.6
34.8
34.8

°F.
94. 28
93.92
94.64
94.64
94.64

94.64
94. 28
94. 28
94.64
94.64

°C.
34.2
34.2
34.2
.34.6
34.6

34.6
34.6
34.2
34.4
34.4

°F.
93. 56
93.56
93. 56
94.28
94.28

94. 28
94.28
93. 56
93.92
93.92

°C.
34.0
33.8
34.0
34.0
34.0

34.2
34.4
34.0
34.0
34.0

"F.
93.2
92.84
93.2
93.2
93.2

93.56

93.92

93.2

93.2

93.2

°C.
22.6
26.0

26.8
27.4
28.0

21.2
21.0
22.6
25.0
27.0

"F.

72.68

78.80

80.24

81.32

82.40

70.16
69.80
72.68
77.00
80.60

Fanning entrance.

" Bees begin to fly freely.

EFFECTS OF CLUSTER HEAT ON THE TEMPERATURE BELOW THE

FRAMES.

It was found that the heat from the cluster had no perceptible
influence on tlie temperature of the air below the frames during the
^\^nter. Practically tlie air was at the outside temperature. But in
summer totally different conditions prevail; the temperature within
the hive becomes equahzed. Furthermore, the crowding of the bees
at certain seasons tends to force them to hang down from the bot-

24 BULLETIN m, U. S. DEPARTMENT OF AGRICULTURE.

toms of the frames or even out at the entrance. Consequently that
space which was outside tlie frames assumes cluster conditions.

Early in the season / averaged 3° C. higher than o at all times;
at the end of the season, September, it averaged from 5° to 6° C.
higher. By the mid(Ue of May /stood only 1 ° or 2° C. lower than the
thermometers in the cluster, although the thermometer in the outside
air was nmch lower. Throughout the summer there was practically
no difference between c and /. During the storm period, as will
be seen in Table IX, which is (hscussed farther on, / ranged even
higher than the prevailing chister temperature. This was undoubt-
edly (kie to the massing of the bees below the frames as they were
crowded in from the alighthig board.

THE EFFECTS OF STORM.

Since the summer of 1 908 was remarkably dry and free from storms,
it is not possible to draw any definite conclusions upon the effects
of storms, cold waves, and winds upon the cluster temperature.
The only severe storm of the summer occurred in the latter part of
August. The outside thermometer went as low as 14° C. (57.2° F.),
while before and after this period there were frequent readings
ranging from 20° to 30° C. (68° to 86° F.). During the storm there
were several high winds. These, however, did not blow directly in at
the entrance. The bees were thus confined for three days, and at
times showed much evidence of shifting and massing at different
parts of the hive. In a glass observatory hive the bees were actually
seen to cluster now in one part of the hive and then in another.
The wind and rain also drove the bees in off of the alighting board
and forced them to hang from the bottoms of the frames. If the
readings of the thermometers nearest the outside of the hive are
rightly interpreted, the cluster withdrew from the walls of the hive,
and this caused a decrease in the temperature at these points. While
there is some evidence in the figures that the cold outside the hive
had its effects on the center of the cluster, the temperature was not
permitted to remain below 34° C. (93.2° F.). No fall was recorded
lower than 33.8° C. (92.84° F.). Thus the bees appear to be able
to control and conserve the temperature with remarkable constancy,
even though there be high wind and relatively low temperature.
Table IX, in comparison with the figures for a bright day in Table
VIII, reveal these facts.

THE TEMPERATURE OF THE BEE COLONY.
Table VIII. — Temperatures of a bee colony on a normal day.

25

Time.

Thermometer.

Month
and day.

Hour.

I.

&.

c.

d.

€.

0.

°C.

°F.

°C.

°F.

°C.

"F.

"C.

°F.

"C.

°F.

"C.

"F.

Aug. 15

6 a. m.i

34.4

93.92

34.4

93.92

35.0

95.00

34.8

94.64

34.8

94.64

24.4

75.92

7 a. m

34.4

93. 92

34.4

93. 92

34.8

94.64

34.8

94. 64

34.6

94.28

26.0

78.80

8 a. m

34.2

93.56

34.4

93.92

34.8

94.64

34.8

94.64

34.8

94.64

24.6

76.28

9 a. m.-

34.2

93.56

34.4

93.92

34.8

94. 64

34.8

94. (i4

34.8

94.64

25.8

78.44

10 a. m

34. G

94.28

34.6

94.28

34.8

94. 64

34.6

94.28

34.6

94.28

27.6

81.68

11 a. m

34.8

94.64

34.8

94. 64

35.0

95.00

35.0

95. 00

35.0

95.00

28.8

83.84

12ra

34.8

94. 64

34.8

94. 64

.35. 0

95.00

35.0

95.00

35.0

95.00

29.0

84.20

1 p. m

34.8

94.64

35.0

95.00

35. 0

95.00

35.0

95.00

35.0

95.00

29.6

85.28

2 p. m

35.0

95.00

35.0

95. 00

3.5.0

95.00

35.2

95. 36

35.2

95.36

30.4

86.72

4 p. m

35.0

95.00

35.0

95.00

35.0

95. 00

35.2

95. 36

35.2

95.36

29.2

84.56

6 p. m

35.0

95.00

35.0

95.00

35. 2

95.36

35.2

95.36

35.2

95. .36

28.2

82.76

7 p. m

34.8

94. 64

34.8

94. 64

3.5.0

95.00

35.2

95.36

35.0

95.00

27.6

81.68

8 p. m

35.0

95.00

35.0

95.00

35.0

95.00

35.0

95.00

35.0

95.00

26.6

79.88

Aug. 18

6a. m

34.0

93.2

34.2

93. 56

34.0

93.2

34.0

93.2

34.2

93.56

21.8

71.24

7 a. ni.3

34.2

93. 56

34.2

93. 56

34.4

93. 92

34.4

93. 92

34.2

93. .56

22.0

71.60

8 a. m

34.2

93. 56

34.2

93. 56

34.4

93.92

34.4

93.92

34.2

93. 56

22.4

72.32

9 a. m.*

34.4

93.92

34.4

93.92

34.6

94.28

34.6

94.28

34.4

93.92

25.0

77.00

10 a. m.'->

34.4

93.92

34.6

94. 28

34.6

94.28

34.8

94.64

34.6

94.28

26.0

78.80

11 a. m

34.6

94.28

34.8

94. 64

34.8

94.64

34.8

94. 64

34.8

94. 64

26.5

79.70

12 m

34.8
34.8

94. 64
94. 64

34.8
34.8

94. 64
94.64

.35.0
35.0

95.00
95.00

35.0
35.0

95.00
95.00

35.0
35.0

95.00
95.00

27.4
28.6

81.32

1 p. m

83.48

2 p. m

34.8

94. 64

34.8

94. 64

35.0

95.00

35.0

95. 00

35.0

95.00

29.0

84.20

3 p. m

34.8

94. 64

34.8

94. 64

35.0

95.00

35.0

95. 00

35.0

95.00

28.0

82.40

4 p. m

34.8

94. 64

34.8

94. 64

35.0

95.00

35.2

95. 36

35.2

95. 36

28.0

82.40

6 p. m

34.8

94.64

34.8

94.64

35.0

95. 00

35.0

95.00

35.2

95. .36

27.4

81.32

7 p. m

34.8

94. 64

34.8

94. 64

35. 0

95. 00

35.0

95.00

35. 0

95. 00

26.2

79.60

8p. m

34.8

94. 64

34.8

94.64

35.0

95.00

35.0

95.00

35.0

95.00

25.6

78.08

1 Cloudy and cabn.

2 Clearing, calm and close.

3 Cloudy.

< Clearing and cabn.
5 Clear.

Table IX. — The effects of storm and wind on the temperatures of the bee colony.

n.

Thermometer.

a.

6.

c.

d.

e.

/.

0.

Mo«* Hour,
and day.

°C.

°F.

"C.

"F.

"C.

°F.

"C. ! 'F.

"C.

°F.

°C.

"F.

"C.

"F.

Aug. 25
Aug. 26

8a. m.i

8.30a. m...
9a. m.2

10 a. m

11 a. m.i....

12 m

1 p. m.<

2p. m

3p. m

4p. m

5 p. m

6p.m.<

7 p. m

8p. m

9p. m

lOp.m

U p. m

12 p. m

1 a. m

2 a. m

3 a. m.6

4 a. m.6

5a. m.6

6 a. m.6

7 a. m.6

34.2
34.2
34.4
34.0
34.2
34.0
34.2
34.0
34.0
34.0
34.0
34.0
34.0
33.8
34.0
34.0
34.0
33.8
33.8
33.6
33.6
33.6
33.6
33.6
33.6

93. 56
93. 56
93.92
93. 20
93. 56
93.20
93.56
93.20
93.20
93.20
93.20
93.20
93.20
92.84
93.20
93.20
93. 20
92.84
92.84
92.48
92.48
92.48
92.48
92. 48
92.48

34.4
34.2
34.4
34.2
34.4
34.8
34.4
34.6
34.4
34.8
34.0
34.2
34.4
34.2
34.2
34.4
34.2
34.0
34.2
34.0
34.2
34.2
34.0
34.2
34.4

93.92
93.56
93.92
93.56
93. 92
94.64
93. 92
94.28
93.92
94.64
93.20
93.56
93.92
93.56
93.56
93.92
93.56
93.20
93. 56
93.20
93.56
93.56
93. 20
93. 56
93.92

34.2
34.2
34.2
34.2
34.4
34.2
34.2
34.0
34.2
34.2
34.2
34.0
34.2
34.2
34.2
34.4
34.4
34.2
31.0
34.0
34.2
34.2
34.2
34.2
34.2

93. 56
93. 56
93.56
93.56
93. 92
93.56
93.56
93. 20
93.56
93.56
93.56
93. 20
93.56
93. 56
93. .56
93. 92
93. 92
93. 56
93. 20
93. 20
93. 56
93. 56
93. 56
93. 56
93.56

.34.2
34.2
.34.2
34. 2
34.2
34.4
34.2
34.0
34.2
34.0
34.0
34.0
34.2
34.0
34.0
34.4
34.2
34.0
34.0
34.2
34.0
34.0
34.0
34.0
33. 6

93.56
93.56
93. 56
93. 56
93. 56
93.92
93.56
93.20
93.56
93.20
93.20
93. 20
93.56
93.20
93.20
93. 92
93. 56
93. 20
93.20
93. 56
93.20
93. 20
93.20
93. 20
92.48

34.0
34.0
33.8
34.0
34.0
34.0
34.0
34.4
34.0
34.0
34.0
33.6
33.6
33.4
33.6
33.0
33. 2
33.4
33.4
33. 0
33.4
33.4
33.2
33. 2
33.4

93.20
93.20

92. 84
93.20
93.20
93.20
93.20

93. 92
93.20
93.20
93.20
92.48
92.48
92.12
92.48
91.40
91.76
92.12
92.12
91.40
92.12
92.12
91.76
91.76
92.12

34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6
34.6

94.28
94.28
94.28
94.28
94. 28
94.28
94.28
94.28
94.28
94.28
94.28
94.28
94.28
94. 28
94.28
94.28
94.28
94.28
94.28
94.28
94.28
94.28
94.28
94.28
94.28

20.4
19.8
19.8
20.8
20.2
20.6
18.4
17.8
17.6
17.0
16.2
18.2
16.4
16.2
15.0
15.0
14.6
15.4
15.6
14.8
17.4
16.2
17.0
16.6
17.0

68.72
67.64
67.64
69.44
68.36
69.08
65.12
64.04
63.68
62.60
61.16
64.76
61.52
61.16
59.00
59.00
58.28
59. 72
60.08
58.64
63.32
61.16
62.60
61.88
62.60

1 Cloudy.

2 Breeze from north.

3 Raining a little.

< Rain.

6 High wind from east.

6 High wind from east, no rain.

26 BULLETIN nfi, U. S. DEPARTMENT OF AGRICULTUEE.

Another fact to which reference has been made under the caption,
"Effects of chister heat on the temperature below the frames,"
should be mentioned here. During this period of storm, jf" frequently-
recorded a higher temperature than the thermometers above it.
This was undoubtedly due to the crowding of the bees in off of the
ahghting board, forming a curtain below the frames. This is an
advantage in helping to conserve the heat and in preventing the cold,
inward draft tlu-ough the entrance from striking directly on the
brood.

THE EFFECTS OF TRANSPORTATION ON THE TEMPERATURE OF THE

COLONY.

Not infrequently beekeepers sustain heavy losses in moving their
bees, although it is not usually done in extremely hot weather.
Since the moving of the experimental colony to College Park, Md., a
distance of about 11 miles, was unavoidable, the writer decided to
make the most of the necessity and determine in so far as possible the
effects of transportation on the colony. Even with precautions,
strong and populous colonies sometimes smother. Brood is often
killed, supposedly from excessive heat. With these points in mind
every precaution was taken to protect the colony from harm; and
since no damage resulted, the experiment reveals the temperature
conditions in a successful transportation of a strong colony under
most adverse circumstances — extreme heat and humidity and bad
roads.

The trip was commenced at 10.30 a. m. on July 2. The day was
humid, with intermittent sunshine and clouds, and no breeze. In
Washington the mercury rose to 32.33° C. (90° F.) at 2 o'clock. The
road was through the city of Washington over asphalt and stone
pavements for several miles and then over rough country roads, which
had scarcely any shade. The colony was moved on a spring express
wagon with cover, the curtains of which were kept down on the sunny
side so as to prevent the sun from striking directly on the hive. The
other curtains were rolled up in order to allow all the ventilation
possible, but since there was no breeze all the draft which the
bees got must have been procured by fanning and by the movement
of the wagon.

The colony was crowded into a 10-frame Langstrotli hive and the
entrance was screened the night previous. All of the thermometers
remamed in position. This, of course, prevented giving ventilation
through the top of the hive, which is the common practice in moving
bees. In order to give room for expansion of the cluster and to con-
fine the ail' as little as possible, the hive was set over an empty body,
on the bottom of which wire cloth was tacked. In order to allow the
air to circulate freety beneath the hive, it was supported above the

THE TEMPERATURE OF THE BEE COLONY. 27

bottom of the wagon on |-inch strips of wood, the spring of which
reheved to some extent the jolt of the wagon. In the morning, before
the colony was disturbed and just after it was loaded, thermometer
readings were taken. On the road readings were also made at short
intervals. In this way tlie result of every successive event in the trip
was known.

The first disturbance, carrying the hive downstairs and loading, was
immediately responded to by the bees. The first 15 minutes on the
road were but slightly more disturbing. Gradually, however, the
temperature increased until 1.30 o'clock in the afternoon and an hour
previous to releasing, when practically the maximum was reached,
36.0° C. (96.8° F.). It should be mentioned, however, that during
the next few hours and even after the bees had their liberty the ther-
mometers in the distant parts of the hive, a and e, registered 36.2° C.
(97.16° F.). But it is probable that the bees clustered more densely
at these pomts than they did in tlie center of the hive. This tempera-
ture can not be considered particularly abnormal, although it is
higher than any temperature registered immediately before or after
the transportation. On several occasions durmg the summer and
even in May, practically the same degree was reached; but since in
normal cii'cumstances it never went higher than 36° C. (96.8° F.),
the temperature observed is probably nearly as high as can be reached
by bees without damage. It would not have taken many' degrees
more than this to have softened the combs and to have caused them
to sag and break. The melting point of pure wax is 62° to 64° C.
(143° to 145° F.), but the difference between the melting point and
the point at which combs become soft enough to sag must be con-
siderable, perhaps 20° C. (36° F.).

It can not be said that the temperature was higher at any one part
of the hive than at another, unless possibly there was a slight tend-
ency for the brood cluster to be mamtained cooler. This would
naturally be expected, but under such trymg circumstances the phe-
nomenon could not be measured satisfactorily. At no tune on the
trip did the bees hang dowTi from their combs into the lower body,
and upon releasmg them there was no evidence of condensation. At
all times, as would have been expected, there was considerable
fanning. Furthermore, the bees were not made cross by their con-
finement, as was the case when the rest of the colonies of the apiary
were moved, which was done under much more favorable circum-
stances except for ventilation. That no brood died in the experi-
mental colony is further evidence that 36° C. (96.8° F.) is not
abnormal.

The colony was placed in its new position at 2.30 o'clock and the
bees liberated. The effects of their liberty on the temperatures were
not apparent, however, as will be seen in Table XI, for more than an

28

BULLETIN 90, U. S. DEPAKTMENT OF AGRICULTURE.

liour, when tlie temperatures began gradually to fall. Finally, when
tlio beos liad orientated themselves and had commenced to return to
the hive, there was a noticeable quietmg and a perceptible drop in
the mercury. At 7.30 o'clock, after all the bees had returned to the
hive, conditions were practically normal.

In conclusion it may be said that the conditions under which the
bees were moved, although trying and about as adverse as possibly
could be encountered, did not produce abnormal heat in the hive.
The temperature increased only 2°, from 34° to 36° + C. (93.2
to 96.8° F.) . "VVliile it is generally admitted that ventilation from the
top is i)referable in movuig bees, on the hypothesis that warm air
rises, ventilation from the bottom was a success in the case under dis-
cussion. In moving the rest of the department apiary to CoUege
Park earlier in the season, when the weather was more favorable, the
day being cloudy with showers, three colonies suffered severely from
overheating and condensation. These colonies were screened at the
entrance and over the top of the hive; but apparently the screenuig of
the top was not sufficient, because when the bees became excited and
expanded as a result of the heat, they packed so tightly against the
top screen as to shut out all ventilation. The tendency of bees is
upward and toward the light. On the contrary, if ventilation is given
from below, there is less tendency for them to pack agamst the screen.
While it is generally maintained that for moving colonies top ventila-
tion is preferable, the present experiment would indicate that bottom
ventilation is practical and advantageous.

For comparison, figures taken the day previous (Table X) and the
day after the transportation (Table XII), as weU as on that day
(Table XI), are presented.

Table X. — Readings of thennometers, July 1, on day previous to transportation of bee

colony.

Thermometer.

Hour.

a.

6.

c.

.

e.

0.

"C.

°F.

°C.

°F.

"C.

°F.

°C.

°F.

°C.

°F.

°C.

°F.

9 a. m

10 a. m

33.4
33.6
33. 8
33.9
34.0
34.4
34.4
34.6
34.8

92.12
92.48
92.84
93.02
93.20
93.92
93.92
94.28
94.64

34.0
34.0
34.2
34.5
34.5
34.8
34.8
34.8
34.8

93.20
93.20
93.56
94.10
94.10
94.64
94.64
94.64
94.64

34.0
34.2
34.2
34.5
34.5
34.8
34.8
34.8
35.0

93.20
93.56
93.56
94.10
94.10
94.64
94.64
94.64
95.00

33.8
33.6
33.8
33.9
34.0
34.0
34.0
34.2
34.8

92.84
92.48
92.84
93.02
93. 20
93.20
93.20
93.56
94.64

33.8
33.6
33.6
33.9
34.0
34.0
34.0
34.2
35.0

92.84
92.48
92.48
93.02
93.20
93.20
93.20
93. 56
95.00

25.8
27.0
28.5
29.0
29. S
31.5
31.5
32.2
29.0

78.44
80.60

U a. m

12 m

83.30
84.20

85.64

2 p. m

88.70

3 p. m

4 p. m

88.70
89.96

8 p. m

84.20

THE TEMPERATURE OP THE BEE COLONY.

Table XI. — Headings of thermometers during transportation of bees, July

extremely tvarm and sultry.

29

Day

Thermometer.

Hour.

a

6

c

d

e

Observations.

°C.

°F.

°C.

°F.

°C.

°F.

°C.

°F.

"C.

"F.

9a. m

34.4

93.92

34.4

93.92

34.4

93.92

34.0

93.20

34.0

93.20

Hive closed but un-
moved.

10.15 a. m.

35.0

95. 00

35.0

95.00

35.0

95.00

34.8

94.64

34.8

94.64

Hive loaded on wagon.

10.30 a. m.

35.0

95.00

35.0

95.00

35.0

95.00

34.8

94.64

34.8

94.64

Drive to College Park

started.

10.45 a. m.

35.2

95. 36

35.0

95. 00

35.1

95. 18

34.9

94.82

35.0

95.00

11 a.m....

35.4

95. 72

35.2

95. 36

35.2

95.36

35.0

95.00

35.0

95. 00

]1.15 a. m.

35.4

95.72

35.0

95. 00

35.1

95. 18

35.0

95.00

35.0

95.00

Sun and clouds.

11.30 a. m.

35.6

96.08

35.2

95.36

35.2

95. 36

35.0

95. 00

35.0

95.00

Do.

11.45a. m.

35.8

96.44

35.4

95.72

35.6

96.08

35.1

95.18

35.2

95.36

Do.

12m

35.8

96.44

35.6

96.08

35.6

96.08

35.3

95.54

3.5.4

95.72

Do.

12.15p.ra.

35.8

96.44

35.8

96.44

35.6

96.08

35.4

95. 72

35.6

96.08

Do.

12.45 p.m.

35.8

96.44

35.6

96.08

35.6

96.08

35.4

95.72

35.6

96.08

Stopped 30 minutes for
lunch.

1 p. m

35.8

96.44

35.6

96.08

35.6

96.08

35. 6

96.08

3.5.6

96.08

1.15 p. m..

36.0

96. SO

35.8

96.44

35.8

96. 44

35. 8

96. 44

3.5.8

96.44

1.30 p. m..

36.0

96. 80

36.0

96. 80

35.9

96.62

35. 8

96.44

36.0

96.80

2p.m

36.0

96.80

36.0

96.80

36.0

96. SO

35.9

96.62

36.0

96.80

2.30 p.m..

36.2

97.16

36.0

96.80

36.0

96.80

36.0

96.80

36.1

96.98

Hive set on stand and
opened.

3p.m

36.2

97.16

36.0

96.80

36.0

96.80

36.0

96.80

36.2

97.16

3.30 p. m..

36.2

97.16

35.8

96. 44

35.8

96. 44

36.0

96. SO

36.0

96. SO

4p.m

36.1

96.98

35.4

95. 72

35.8

96.44

36.0

96.80

36.0

96. 80

4.30 p.m..

35.4

95. 72

34.1

93. 38

34.8

94.64

35.1

95.18

35.4

95.72

5p.m

35.0

95. 00

34.0

93. 20

34.6

94.28

34.9

94.82

35.0

95.00

6.30 p.m..

34.6

94.28

34.2

93.56

34.2

93.56

34.4

93.92

34.4

93.92

Bees all returned to
hive.

7p. m

34.4

93. 92

34.2

93.56

34.2

93. 56

34.2

93.56

34.2

93.56

7.30 p. m..

34.4

93.92

34.0

93.20

34.0

93.20

34.2

93.56

34.2

93.56

Quiet and normal.

Table XII. — Readings of (herm.oyneters, July .?. J)ay after transportation of bees.

Thermometer.

Hour.

a

6

c

d

e

Observations.

°C.

"F.

"C.

°F.

°C.

°F.

"C.

"F.

"C.

°F.

7.30 a. m...
8.30a. m...

10 a. m

11a. m

12m

7p. m

8p. m

33.8
33.8
33.8
34.0
34.0
34.8
34.8

92.84
92.84
92.84
93. 20
93.20
94.64
94.64

34.0

33.8
34.0
34.0
34.2
34.8
34.6

93.20

92.84
93.20
93. 20
93. .56
94.64
94. 28

34.0
34.0
34.0
34.0
34.2
34.6
34.6

93. 20
93. 20
93. 20
93.20
93.56
94.28
94.28

33.6
33.4
33.4
33.4
33.6
34.2
34.0

92.48
92.12
92.12
92.12
92.48
93. .56
93. 20

33.0
33.0
33.6
33.4
33.4
34.0
34.0

91.40
91.40
92.48
92.12
92.12
93.20
93.20

Cloudy.
Breeze.

Bees returned.

o

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1914

BULLETIN OF THE

No. 100

Contribution from the Bureau of Entomology, L. O. Howard, Chief.
August 31. 1914.

(PROFESSIONAL PAPER.)

WALNUT APHIDES IN CALIFORNIA.

By W. M. Davidson,
Scientific Assistant, Deciduous Fruit Insect Investigations.

INTRODUCTION.

The study of walnut aphides dealt with in the following pages was
begun early in the year 1911 and contmued until the summer of 1913.
The observations were at first made at San Jose, Cal., but after Sep-
tember, 1912, the work was done chiefly at Walnut Creek, Cal. Prac-
tically all the life-history observations were made at the former
locality, and much of the control work was done at Walnut Creek.
The habits of the aphides do not vary materially throughout Cali-
fornia. It was at first the writer's intention to confhie his studies to
the European walnut aphis (ChroTnapMs juglandicola Kalt.), as this
species alone infests walnuts of commercial value grown in California,
but latterly two native species of Aphididae were found to be pests
on native walnuts much used for stock on which to graft the European
or Persian nut, and thus the studies were extended so as to include
all three species. The two native aphides above mentioned are MoneUia
caryse MoneU, the American walnut aphis, which affects the eastern
black walnut (Juglans nigra) and MoneUia caryella Fitch, the little
hickory aphis,^ which affects the California black walnut (Juglans
calif ornica) . Both of these species infest the Royal Hybrid walnut
(a cross between the eastern black walnut and the California black
walnut), while the Paradox Hybrid walnut (a cross between the
European walnut and the California black walnut) is attacked by the
European walnut aphis and to a lesser extent by the little hickory
aphis. Both of these hybrids are rapid growers, and a certain per-
centage of the seedlings obtained from the crossings makes good
stock on which to graft the commercial varieties of nuts. The great
majority of European nuts and their varieties are grown m California

1 This is the name Fitch gave to species which he found on hickory, and it seems best to retain it,
although rather an unfortunate title in so far as California is concerned, as the only wild member of the
Juglandacese in that State is Juglans californica.

40859°— Bull. 100—14 1

2 BULLETIN 100, U. S. DEPARTMENT OF AGEICULTUEE.

on roots of either the California black walnut straight or on roots of
one or the other of these two hybrids. When a graft has been made
and both stock and scion are putting out leaves simultaneously, more
than one species of apliis will usually occur on the same tree. In
such a case the two species feed on theu- own particular host, but the
migrant forms of either may be found resting on foliage of the oppo-
site host. The Paradox and Royal hybrids are used in various parts
of California as shade trees and will furnish a fine grade of wood,
which will take on a high polish.

THE EUROPEAN WALNUT APHIS (Chromaphis juglandicola Kaltenbach).

Lachnus juglandicola Kaltenbach, Monographie der Familien der Pflanzenlause,

Aachen, 1843.
Calliptcrus juglandicola Koch, Die Pflanzenlause Aphiden, Niirnberg, p. 224,

1857.
Calliptcrus juglandicola Passerini, Gli Afidi, Parma, 1860.
Callipterus juglandis Walker, The Zoologist, ser. 2, v. 5, p. 2000, Feb., 1870..
Pterocallis juglandicola Buckton, Monograph of the British Aphides, v. 3, London,

1881, p. 32-34.
Callipterus juglandicola Schouteden, Mem. Soc. Ent. Belg., v. 12, p. 209-210.
Chromaphis juglandicola Essig, Mo. Bui. Cal. State Com. Hort., v. 1, no. 5, p.

190-194, figs. 72-73, April, 1912.

In 1870 Walker erected the genus Chromaphis and designated
Callipterus juglandicola Kaltenbach as the type species. Reference
to this is made by H. F. Wilson in his paper ''A Key to the Genera
and Notes on the Synonymy of the Tribe Callipterini, Family Aphi-
didae," Canad. Ent., v. 42, no. 8, p. 253-259, Aug., 1910.

HISTORY OF THE SPECIES.

The species was described originally by J. H. Kaltenbach in his
"Monographie der Familien der Pflanzenlause" as Lachnus juglandi-
cola. A somewhat free translation of this description is as follows:

Wingless: Pale yellow, egg-shaped, flat, square, incised, and armed with glandular
hairs on the margins; legs whitish- yellow, a black spot on the apex of the hind femora.
Length, Y'-

Winged: Yellow; eyes red; antennae whitish, with black rings; cornicles yellow,
hardly noticeable; tail lacking.

This tree louse occurs sporadically in June and July in numbers under the leaves
of the walnut tree (Juglans regia).

Wingless: Antennee shorter than the head and thorax combined, not markedly
jointed, whitish-yellow. Apex of antennae black, of third joint ringed black. Eyes
light red; beak short, scarcely reaching to the first coxae. On the dorsum occur two
longitudinal rows of black spots, which are absent on younger individuals. Cornicles
and tail lacking. Legs hyaline whitish-yellow; a black spot is found on the upper
side of the hind femora at their apices.

Winged: Antennaj noticeably shorter than the body, pale, the four major joints
black at their apices; third joint distally enlarged; sixth joint with a gradually
tapering thin apex. The body is yellow; in many cases the black dorsal spots of the
abdomen are absent; in other cases but two to six are present; cornicles scarcely per-

WALNUT APHIDES IN CALIFORNIA. 6

ceptible, yellow; tail not present. Legs pale; the spots on the apex of the hind
femora are larger than those of the wingless. In well-colored examples such spots
occur on the middle femora and those on the hind femora are enlarged into a ring.
The wings are transparent; the stigma yellow, cubitus and the two inner veins brown
and markedly stouter at the base, then gradually becoming finer and paler; veins of
lower wing and wing margin pale yellow; stigmatic or foiurth vein very fine and
strongly curved.

There is no doubt that Kaltenbach's species is the same that
occurs commonly all over California on the European wahiut. The
black femoral spot, together with the antennae as described, estab-
lishes its identity. Kaltenbach's wingless form appears to be the
oviparous female in her penultimate molt, for the true apterous vivip-
arous female — a common form in the majority of plant lice — does
not exist, or, if it does, is extremely rare, the author in two years of
close observation having failed to observe it. Buckton (1872) ^
gives a description of the apterous viviparous form, but he also seems
to have had before him the immature oviparous form.

The insect probably occurs wherever the European walnut is
grown. It has been reported from aU over Europe, as weU as from
the States of Colorado (GOlette, 1910), Oregon (Wilson and Lovett,
1911-12), and California (Essig, 1909).

GENERAL DESCRIPTION: CHARACTER AND EXTENT OF INJURY.

This aphidid is a small, lemon-yellow insect, about one-sixteenth
of an inch in length. It occurs sporadically on the underside of the
leaves and on the young fruit of the European walnut (Juglans regia)
and its cultivated forms and hybrids. It appears on the upper sur-
face of the leaf only at times of very severe infestation. It is to be
found from late February or early March until December, persisting
as long as the leaves remain on the tree, but is present in greatest
numbers during the months of July and August. As many as 200
individuals may occur on a single large leaflet if infestation be severe,
while the author has observed over 30 aphides on a single young nut.
Nuts badly infested while young never attain their normal size.
Many of them mature half-sized, covered on the upper surface with
the black sooty fungus which thrives on the sticky exudations of the
aphides. Attacks on the tree year by year also materially reduce
its vitality, since the aphides will be present in the spring even before
the leaves have opened and will remain until these drop.
§ Plate I, figure 1, shows the difference in size between infested and
uninfested nuts of one variety of European walnut, while Plate I,
figure 2, demonstrates the appearance of the sooty fungus on a
walnut leaf.

1 Dates in parentheses refer to the Bibliography, p. 47.

i

BULLETIN 100, U. S. DEPAKTMENT OF AGKICULTUKE.

LIFE HISTORY AND TECHNICAL DESCRIPTIONS.

The Viviparous or Asexual Forms.
When the young stem-mother is ready to emerge in the spring she
causes the shell of the winter egg to burst with a longitudinal sht on
the dorsal surface from the micropylar end. (See fig. 1.) Egress is
performed head first, and antennae and legs are requisitioned by the
young larva in worming its way out of the shell. Wliile the process
of emerging, which occupies half an hour or more, is taking place, the
aphis assumes an erect position at right angles to the long axis of the
egg. After the exit of the young the eggshell has a large triangular
hole at the micropylar end.

As soon as the buds begin to swell in early spring these stem-mothers
hatch and continue hatcliing until the leaves have fully opened out, at
which time all will have issued from the egg. The earliest plant-lice
to emerge may be seen wandering over the bare twigs and buds,
apparently feeding a little upon the scales protecting the unopened
buds, but not showing much growth until the buds
have opened and can afford nourishment.

Undoubtedly many of the apliides that hatch
early die of ill nourishment, and some of these do
not attain their full development for six or seven

weeks, while those hatching later and findmg

YiG.i.-chromapMsjvgiandi- tender food iu abundance become full grown at
cola: Group of eggs, three ^| j ^£ £^^ wccks. Certain it is that on a

lowest hatched. Twenty i n u

times natural size. (Origi- particular tree the stem-mothers all became
°^''^ winged almost simultaneously. On trees which

leaf early the stem-mothers will begin emerging [from the egg as
early as February 15, but on the Franquette and such late varie-
ties no aphides will be found until in April. Immediately after
hatching the Uce seek the buds-or young leaves. In the former case
the aphides crawl in between the scales, but on the leaves they
appear on the lower or exposed side, notwithstanding the fact that
much better protection is afforded by the upper, as yet unfolded, sur-
face which at that time is almost entirely hidden from view. Possibly
the sticky character of the upper surface of the leaves repels them.
Table I indicates the fife cycle of four stem-mothers which hatched
after the buds had opened.

Table I. —Period of development of the stem-mother of Chromaphis juglandicola, San

Jose, Cal., 1912.

No. of individual.

Date of
hatching.

Date of

acquiring

wings.

Period from
hatching to
maturity.

1

Mar. 24
24
24

24

Apr. 28
28
28
29

Days.
35
35
35
36

2

3

4

Average period.

35.25

Bui. 100, U. S. Dept. of Agriculture.

Plate I.

Fig. 1.— Three Matured Nuts of European Walnut Seedling.
[Middle nut iiiitural size, other two undersized from attack by aphides.]

Fig. 2.— Upper Side of Three Leaflets of European Walnut Seedling.

[The central leaflet shows growth of fungus thriving upon the exudation of aphides above.
Two-thirds natural size.]

WALNUT APHIDES IN CALIFORNIA. 5

THE stem-mothek; newly hatched young (fig. 2).

Oval, lemon yellow. Eyes red, of moderate size. Antennae 3-jointed, not quite
reaching to base of second coxae; joint III nearly three times as long as joints I and II
together. Legs comparatively long, entirely pale. Body covered with capitate
hairs. Cornicles very small, pale whitish -yellow, hardly raised above the surface of
the body. Cauda small, pale, bluntly conical. Beak entirely pale, reaching second
coxse. Black knee spots characteristic of this species absent. Measurements: Length
of body, 0.72 mm.; width, 0.30 mm.; antenna, joint I, 0.04 mm.; joint II, 0.035 mm.;
ioint III, 0.145 mm. Almost immediately after birth the legs and antennas turn
dusky gray and the dark abdominal spots appear. In
this respect the young of the stem-mothers differ from
those of all other generations, for the appendages of the
yoimg aphides of subsequent broods never turn entirely
dusky nor do the abdominal spots appear so early.

the stem-mother; 4 DAYS OLD.

Yellowish -green, flatly oval, closely appressed to the
surface of the leaflet or bud scale. Antennae and legs
dusky gray. Eyes circular, red, small. Head, thorax,
two proximal antenual joints, and abdomen bearing capi-
tate hairs which arise (those of the antennae excepted)
from small tubercules situated in the middle of a small, ^f • 2.-Cftromapfeis ju^-
, r> • • 11 1- 1 • • ?ond?co/a.- Stem-mother, newly

circular, dusky area. Antennae 3-jomted, the distal joint hatched. (Original.)

the largest. Cornicles very small, erect. Cauda almost as

long as the hind tarsus, its apex blunt. Cornicles and cauda concolorous with the
abdomen. Beak very pale, reaching second coxae, its extreme apex brown. Under-
side of the head very pale yellow; of the abdomen greenish-yellow.

THE stem-mother; after first molt and just previous TO SECOND MOLT.

Pale lemon-yellow or yellowish green, flatly oval, closely appressed to the plant
surface, occurring on the underside of the expanding leaves, between the ribs.
Antennae and legs very pale yellow, almost hyaline. Antennae short, reaching slightly
beyond the posterior margin of the prothorax, 3-jointed, with a rudimentary suture
on the distal half of joint III . This joint is about three times aa long as the two proxi-
mal joints together. Eyes crimson, not fully developed. Legs entirely pale, with-
out any trace of dark knee spots. Thorax and segments 1 to 6 of the abdomen with two
longitudinal rows of black or brown spots, on each of which occurs a small pale tubercle
bearing two capitate hairs, one larger than the other. On the thoracic segments and
on abdominal segments 1 to 7 occur two rows of pale lateral tubercles, each of which
bears tliree capitate hairs. The frontal margin of the head bears six such hairs on
tubercles. Antennal joints I and II with a capitate hair on their inner margins near
the middle, and joint III with one such hair on the inner margin near the base. The
eighth abdominal segment bears a dorsal fringe of six capitate hairs, those on either
end being smaller than the four inner ones. Cornicles situated on segment 6, as broad
as long, erect, concolorous with the abdomen. Cauda without armature, bluntly coni-
cal, almost hyaline, about as long as the hind tarsus. Beak barely reaching second
coxae, pale yellow, the extreme tip brown. Measurements: Lengtli of body, 1.55 mm. ;
width, 0.775 mm.; antenna, joint I, 0. 053 mm.; joint 11,0.048 mm.; joint 111,0.304
mm.

Described from specimens collected at San Jose, CaL, March 28,
1912.

6

BULLETIN 100, U. S. DEPARTMENT OF AGKICULTUKE.

Fig. 3. — Chromaphis juglandicola: Larva of
stem-mother after second molt. (Orig-
inal.)

After the second molt the spines on the dorsum of the body disap~
pear. (See fig. 3.)

The pupal and imaginal stages of the stem-mother show no appar-
ent diiferenco in respect to size, color, or structure from those of the

later viviparous generations, and thus
one description of these forms will suf-
fice for all the winged viviparous gen-
erations.

THE PUP.A. OF THE WINGED VIVIPAROUS
FEMALE (fig. 4).

General color pale lemon-yellow. Eyes red,
fully formed. Antennae reaching a little be-
yond the base of the wing-pads, pale, joint III
the longest, joints IV and V subeqtial. Ocelli
present. Anterior margin of the head bearing
six capitate spines. Thoracic segments pale
yellow. Wing-pads pale yellow, closely ap-
pressed to the sides of the body. Legs pale
yellow, with the dark knee spot on the hind
femora only; tarsi dusky. Abdomen oval, pale
lemon-yellow, with a A'^arying number of dark
spots on the dorsum, which spots are always present on segment 5 but often lacking on
the other segments. Head, thorax, and abdomen furnished with lateral rows of capi-
tate hairs wliich stand on small pale tubercles. Cornicles small, as wide aa long,
slightly constiicted in the middle, situated on the sixth abdominal segment. Cauda
short, about as long as the cornicles, bluntly rotmded at the apex. Cornicles and
Cauda concolorous with the body. Beak short, pale, stout, reaching to the first pair of
coxae. The pupa has the legs relatively a little shorter than those of the adult and is
thus more closely appressed to the leaf surface . The
body is quite flat. Measurements: Length of body,
1.87 mm. (average); width, 0.85 mm. (average max-
imum); antenna, joint I, 0.050 mm.; joint II,
0.042 mm.; joint III, 0.183 mm.; joint IV, 0.081
mm.; joint V, 0.076 mm.; joint VI, 0.065 mm.;
filament, 0.034 mm. Cornicles, 0.04 mm.

The stem-mothers pass through the
pupal molt about one week before the final
molt takes place, and after the latter they
acquire their full development as winged
adults. In the latter generations the
pupal instar occupies from three to six
days.

THE WINGED VIVIPAROUS FEMALE (fIG. 5).

General color pale lemon-yellow; many individ-
uals are darker yellow, yellowish-brown, or salmon-
pink. Antennae on very small frontal tubercles, about one-half the length
of the body, yellow, with the inner lateral margins of the first two joints dusky;
articulations of joints III to VI and the whole filament dusky to black. Eyes red.
Ocelli present. Prothorax yellow. Thoracic lobes and sctitellimi light brown, some-
times greenish-yellow, pale yellow in newly-molted individuals. Wings of medium

Fig. -1. — Chromaphis jtiglandicola:
Pupa of winged viviparous fe-
male. (OriE;inal.)

WALNUT APHIDES IN CALIFORNIA.

size; subcosta and wing insertions pale yellow; stigma pale gray, with a darker area
at the confluence of the third discoidal vein, and another such though smaller area at
the apex; veins rather heavy, dark brown, all three discoidals arising from the sub-
costa and thickened at their bases; second branch of third discoidal nearer the -mng
apex than the first fork; third discoidal describing a regular gentle curve for its entire
length; stigmatic vein entire, the depth of its curve varying in different examples,
generally reaching the wing margin midway between the apex of the stigma and the
the end of the third discoidal (often it touches the margin considerably nearer the
stigma, but rarely neai-er the tliird discoidal) . Legs rather irhort, but a little longer than
those of the pupa; front pair yellow with the tarsi and apical third of the tibise dusky

I

Fig. 5.— Chromaphis juglandicola: Winged viviparous female (appendages of left side removed), a.
Left antenna; 6, riglit cornicle; c, front tarsus. (Original.)

gray and the knee spot rarely present (gray when present); middle pair yellow, with
an indefinite gray spot on the upper side of the femur above the knee and with the
tarsi dusky gray; hind pair yellow, with a coal-black spot (sometimes produced into
an annulation) on the upper side of the femur above the knee joint and wath the tarsi
dusky gray as in the other i^airs. The knee spots are always present on the hind
femora, while they occur in about 80 per cent of individuals on the middle femora.
In 35 individuals examined throughout the year all had the spots on the hind femora,
28 had spots on the middle femora, and only 1 had spots on the fore femora. Abdomen
pale lemon-yellow, widest at segment 3, considerably wider than the thorax, gen-
erally bearing two oval brown spots on segment 5 and more rarely with two similar but
smaller spots on segment 4 ; occasionally immaculate . These spots are sometimes gray-
ish, varying in intensity, and appear to be the pupal markings retained in theadultform.

8 BULLETIN 100, U, S. DEPARTMENT OF AGEICULTURE.

Cornicles (fig. 5, b) pale yellow, constricted in the middle, barely as long as broad.
Abdominal segments 3 to 6 inclusive bearing pale lateral tubercles. Body without
hairs. Cauda very pale, globular, about as long as the cornicles. Beak pale yellow,
the extreme tip black, reaching a little beyond the first coxae. Sternum pale brown.
Measurements: Length of body, 1.62-2.55 mm., average 2.08 mm.; width of body at
segment 3 of abdomen, 0.71-1.06 mm., average 0.88 mm.; wing expanse, 4.42-5.21
mm., average 4.77 mm.; antenna, joint I, 0.046-0.067 mm., average 0.055 mm.; joint
II, 0.039-0.055 mm., average 0.043 mm.; joint III, 0.267-0.408 mm., average 0.337
mm.; joint IV, 0.153-0.233 mm., average 0.196. mm.; joint V, 0.133-0.191 mm., aver-
age 0.162 mm.; joint VI, 0.079-0.094 mm., average 0.083 mm.; antennal filament,
0.038-0.043 mm., average 0.040 mm.; total length of antenna, 0.775-1.060 mm., aver-
age 0.916 mm.; cornicles, 0.05 mm.; cauda, 0.056 mm.

There are from 6 to 8 transverse oval sensoria on antennal joint III, 1 terminal sen-
sorium on joint V, and three terminal ones on joint VI. Buckton's measurements
(Buckton, 1872) seem to have been taken from small examples for, with the exception
of those of the antennal joints, his measurements are all smaller than the average found
by the writer. It may be that California examples are larger than the European.

Within a few hours after the last molt the wings harden and the chitin
stiffens. The stem-mothers then begin to deposit the young that
have been visible as pseudova for a week or longer inside their bodies.
In the life-liistory experiments the greatest number of young pro-
duced by one viviparous female was 44. These were extruded from
the body in 20 days, 30 in the first half and 14 in the last half of that
period. Several adults under observation deposited 11 or 12 young
within 12 hours after reaching maturity, and no more after that,
dying with many unborn pseudova in their bodies. In the field
the aphides deposit all their young on one leaf or on several leaves
near one another. The average number of young deposited by a single
adult ranges between 25 and 35. This seems to be about the same as
in other closely related CaUipterini, but is a much smaller number
than that occurring in members of other tribes of Aphididse. The
aphides of the fall viviparous generation produce fewer young,
those which develop in November depositing only 6 or 8. As many
as 30 oval unborn aphides may be seen in the .body of one recently
molted female. These embryos vary in size, only those to be de-
posited immediately being fuUy grown. Each is inclosed in a very
thin hyaline sac in which they are contained at birth.

The newly deposited young of the second and subsequent genera-
tions, both viviparous and oviparous, differ from the infant stem-
mothers in that they are entirely pale yeUow (rarely suffused with a
faint pink) and remain thus until the first molt, while the young
stem-mothers have dusky appendages and abdominal spots. The
young deposited by the stem-mothers pass through their first molt
in from three to six days. After this molt there appear brown or
black dorsal spots in the majority of the individuals, and these
marldngs persist through the succeeding molts. A small percentage

WALNUT APHIDES IN CALIFORNIA.

of examples remain immaculate throughout development. The
"lice" of the second generation develop more quickly than the stem-
mothers or first generation, owing to greater abundance of food
supply and to the higher temperature existing at that later period.
In 1911 second-generation young were deposited in the field on
early varieties of walnuts a httle before April 23, while in the following
year these were deposited as early as April 6. Tliis is to be expected,
since in 1912 the trees came out in leaf two weeks earlier than in the
previous year. Table II shows the life cycle of 41 individuals of the
second generation at San Jose, Cal., in 1911.

Table II. — Life cycle of the second generation of Chromaphis juglandicola, San Jose,

Cal, 1911.

No. of
individ-
ual.

Date of—

Life
cycle.

No. of
individ-
ual.

Date of—

Life
cycle.

Deposi-
tion.

Acquiring
wings.

Deposi-
tion.

Acquiring
wings.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

Apr. 23
23
23
23
23
24
24
24
24
24
25
26

May 1

2
2
2
2

May 12
12
14
16
18
18
18
18
18

1.8
20
21
21
21
21
21
21
21
21
22
22

Days.
19
19
21
23
25
24
24
24
24
24
25
25
20
20
20
20
20
19
19
20
20

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

May 2
2
3
3
3
3
3
4
4
5
5
5
6
6
6
6
6
7
8
9

May 22
22
22
22
22
22
22
23
23
25
25
25
26
26
27
27
27
27
28
27

Days.
20
20
19
19
19
19
19
19
19
20
20
20
20
20
21
21
21
20
20
18

Life cycle: Days.

Maximum 25

Minimum 18

Average 20. 7

The apliides of the third generation appear on the earliest varieties
of wahiuts about the middle of May, but on the late varieties such
as the Franquette this brood appears as much as a month later. The
individuals of this generation are on the average slightly larger than
those of other generations. In a large series of adult viviparous females
taken throughout the year of 191 1 the largest example was of the third
generation. Its body was 2.55 mm. in length and 1.06 mm. in width,
and both of its antennae measured 1.06 mm., or 0.02 mm. in excess
of the next longest antenna in the series. Table III indicates the life
cycle of 97 individuals of the third generation.
40859°— Bull. 100—14 2

10

BULLETIN 100, U. S. DEPARTMENT OF AGEICULTUKE.

Table III. — Life cycle of the third generation of Chromaphis juglnndicola, Snn Jose,

Cal., 1911.

Date of—

Date of—

No. of
indi-
vidual.

Life
cycle.

No. of
indi-
vidual.

Life
cycle.

Depo-

Acquir-

Depo-

Acquir-
ing.

sition.

ing

sition.

Days.

Days.

1

May 19

Juno 4

16

50

May 19

June 7

19

2

19

4

16

51

19

19

3

19

4

16

52

19

19

4

19

4

16

53

19

19

19

5

17

54

19

19

6

19

5

17

55

19

19

7

19

5

17

56

19

19

8

19

5

17

57

19

8

20

9

19

5

17

58

19

8

20

10

19

5

17

59

19

8

20

11

19

5

17

60

19

8

20

12

19

5

17

61

19

8

20

13

19

5

17

62

19

8

20

14

19

5

17

63

19

8

20

15

19

5

17

64

19

8

20

16

19

5

17

65

19

9

21

17

19

5

17

66

19

9

21

18

19

6

18

67

22

10

19

19

19

6

18

68

22

U

20

20

19

6

18

69

22

11

20

21

19

6

18

70

22

11

20

22

19

6

18

71

22

11

20

23

19

6

18

72

22

11

20

24

19

6

18

73

22

11

20

25

19

6

18

74

22

11

20

26

19

6

18

75

22

11

20

27

19

6

18

76

22

11

20

28

19

6

18

77

22

11

20

29

19

6

18

78

22

11

20

30

19

6

18

79

22

11

20

31

19

6

18

80

22

11

20

32

19

6

18

81

22

11

20

33

19

6

18

82

22

11

20

34

19

6

18

83

22

11

20

35

19

6

18

84

22

12

21

36

19

6

IS

85

22

12

21

37

19

6

18

86

22

12

21

38

19

6

18

87

22

12

21

39

19

6

18

88

22

12

21

40

19

6

18

89

22

12

21

41

19

6

18

90

22

13

22

42

19

6

18

91

22

13

22

43

19

7

19

92

22

13

22

44

19

7

19

93

22

14

23

45

19

7

19

94

22

14

23

46

19

7

19

95

22

14

23

47

19

7

19

96

22

15

24

48

19

7

19

97

22

15

24

49

19

7

19

Life cycle: Days.

Maximum 24

Minimum 16

Average 19. 1

Generations IV to VIII inclusive occupy roughly 16 days apiece
for development, and this period is the average life cycle during the
summer months. Some aphides will develop in 14 days and others
in 19 or 20. Table IV gives the life-cycle records of these five genera-
tions and also that of the ninth. The records in some instances are
small, but the fact that in the first five of these generations there is
practically no difference in the duration of the life cycle was cor-
roborated by a larger series of experiments during the summer months
with individuals of which the respective generations were unknown.

WALNUT APHIDES IN CALIFORNIA.

11

Table IV. — Life cycle of the summer generations of Chromaphis juglandicola, San Jose

Cal., 1911.

Generation No.

No. indi-
vidual.

Date of—

Life
cycle.

Form of indi-
vidual.

Deposi-
tion.

Reach-

infr adult

state.

Days.

{ 1

June 8

June 28

20

Viviparous.

2

16

July 1

15

Do.

3

16

1

15

Do.

IV

4
6

16
16

1

9

15
16

Do.
Do.

6

16

2

16

Do.

7

16

2

16

Do.

1

July 1

15

14

Do.

V

2
3

1
1

15
17

14
16

Do.
Do.

4

1

18

17

Do.

1

15

31

16

Do.

2

15

31

16

Do.

3

15

31

16

Do.

4

15

31

16

Do.

5

15

31

16

Do.

6

15

31

16

Do.

7

15

31

16

Do.

S

16

Aug. 1

16

Do.

9

16

1

16

Do.

10

16

1

16

Do.

VI

11
12

16
16

2
2

17
17

Do.
Do.

13

16

2

17

Do.

14

16

2

17

Do.

15

17

2

16

Do.

16

17

2

16

Do.

17

17

2

16

Do.

18

17

3

17

Do.

19

17

4

18

Do.

20

18

5

18

Do.

21

18

6

19

Do.

22

18

6

19

Do.

1

Aug. 2

17

15

Do.

2

2

17

15

Do.

VII

3

2

17

15

Do.

4

2

19

17

Do.

5

3

20

17

Do.

6

3

20

17

Do.

7

3

20

17

Do.

f 1

18

Sept. 1

14

Do.

2

19

2

14

Oviparous.

3

19

2

14

4

19

3

15

Do!

5

19

3

15

Do.

6

19

3

15

Do.

7

19

3

15

Do.

8

19

3

15

Do.

VIII

9
10

19
20

3

4

15
15

Do.
Do.

11

20

4

15

Do.

12

20

4

15

Do.

13

20

6

17

Viviparous.

14

20

6

17

Oviparous.

15

20

6

17

Do.

16

20

7

18

Viviparous.

1

Sept. 5

30

25

Oviparous.

2

5

Oct. 1

26

Do.

3

5

6

31

Viviparous.

4

5

6

31

Do.

5

5

8

33

Do.

6

5

8

33

Do.

7

7

9

32

Do.

IX

8
9

7
7

11
13

34
36

Do.
Do.

10

7

14

37

Do.

11

7

14

37

Do.

12

8

12

34

Do.

13

8

17

39

Do.

^ 14

8

17

39

Do.

12 BULLETIN 1(X), U. S. DEPARTMENT OF AGRICULTURE.

An inspection of Table IV shows that the length of the Ufe cycle
of Generations lY to VII was almost the same. This is to be ex-
pected, since in 1911 the months of June, July, and August had
ahnost identical temperatures both day and night. It mU also be
observed that there was a very noticeable difference between the Ufe-
cycle periods of Generations VIII and IX, 16 individuals of the eighth
generation averaging 15.4 days and 14 individuals of the ninth gen-
eration averaging 33.4 days. The ninth generation thus required
for development a period over twice as long as that required by the
preceding generation, developing almost as slowly as the stem
mother generation (see Table I). Yet the temperature during the
daytime influencing the ninth generation differed but little from
those which obtained during the development of the eighth. The
probable causes of the slow development of the ninth generation lice
is to be foimd in the colder night temperatures to wliich they were
subjected and in the fact that the leaves at this time are becoming
less vigorous and consequently afford poorer nourishment for the
aphides than earlier in the season. There is a tenth generation, and
in warm early seasons probably an eleventh, but in these generations
the brood is small and the ''Uce" grow slowly. Plant lice may be
found in early December giving birth to young, which are destined
to perish either when the leaves drop or through exposure to hard
frost. The author has observed dead aphides of all sizes on the
brown frosted leaves during early winter.

All the plant Uce used for tlie life-history experiments were reared
out of doors on young seedUng walnut trees planted in pots and in-
closed with glass cyhnders. In 1911 the stock was procured from
stem mothers collected on the earhest varieties of walnuts. When
the work was started in 1911 it was too late to procure eggs, and so
the data on the stem-mother cycle was acquired in 1912.

After the ninth generation no more Hfe-history experiments were
carried on in the rearing cages, but a weekly examination was made
of infested leaves in the field to determine the proportions of the dif-
ferent forms, sexual and asexual, during the fall months.

THE OVIPAROUS OR SEXUAL FORMS.

The oviparous forms are the true sexes, comprising the winged
male and the wingless oviparous, or egg-producing, female. The
female aphis, after fertilization by the male, deposits true eggs, in
which form alone the insect can tide over the winter months when
no food supply is procurable.

As is shown in Table IV, there is no real oviparous generation, for
in all the later or faU generations a certain percentage of the young
will develop either into the sexed males or the sexed females. On
heavily infested trees oviparous aphides appear as early in the season

WALNUT APHIDES IN CALIFORNIA.

13

as July, while on trees attacked by few lice these forms will not occur
until September or October. It therefore seems that the more
heavily a tree is infested the earlier will the sexed forms be produced.
A glance at Table IV demonstrates that the first oviparous form
of the life-cycle material became adult September 2, and was a
member of the eighth generation. In the field the first oviparous
form was observed in 1911 on July 7, and in 1912 on July 9. Both of
these occurred on early-leafing trees and probably belonged to the fifth
or sixth generation. As the growth of the aphis colony may be said to
have reached its zenith about the middle of July, it is at the time of
its greatest abundance that the sexed individuals begin to appear.
And, indeed, for the welfare of the species they appear none too
soon, for it is in July and August tliat the hordes of natural enemies
work tremendous havoc, frequently cleaning up a bad infestation on
a tree within three weeks. Those sexual females that have gone to
the trunk and limbs to deposit their eggs very often escape destruc-
tion wliile the others remaining on the foliage are devoured. Until
the middle of August the sexual forms are comparatively rare and
comprise less than 5 per cent of the whole, but after that time they
become more and more abundant. The sexed females always greatly
outnumber the males. Table V indicates the advance and decline
of the sexual forms in the late summer and fall. The data were ob-
tained by weekly visits to badly infested trees, during which the
lice on a certain number (50) of leaflets picked out at random were
comited. It must be borne in mind that as the fall advances more
and more sexual females repair to the limbs for the purpose of depos-
iting their eggs, and that therefore in the case of the later counts a
reaUy greater proportion of these were present on the trees than
would appear from the records.

Table V. — Comparative numbers of sexual and asexual forms of Chromaphis juglandicola
observed on the foliage at different dates, San Jose, Cal., 1911.

Number of —

Percent-
age of—

Date of collection.

Vivipa-
rous
forms.

Ovipa-
rous
forms.

Males.

Vivipa-
rous
forms.

241
258
203
171
166
207
172
420
233
10

247

355

143

66

74

117

111

80

36

0

4
5
6
9

14
9
4

11
7
0

49

^ 23 ::::::: :::::::::::;::::::::.

42

30 ...

58

70

14

65

24

62

60

9

82

16 . . .

84

23

100

Total

2,081

1,229

69

61.6

r 1

14

BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE.

The maximum number of aphides found on a single leaflet through-
out the counts was 90, of which 64 were sexual females. This oc-
curred on the first date of collection.

It will be noticed from Table V that on the first two dates the ovi-
parous forms were predominant but that on all later dates these were
outnumbered by the viviparous individuals. On the date of the
fourth collection (October 7) numerous sexual females were found on
the limbs of the tree, and their number was more and more augmented
each succeeding week. About October 1 the males appeared in num-
bers, very few of them having been in evidence previous to this time,
although the first male of the season was noticed July 10. Table VI
indicates the preponderance in numbers of the sexual female over
the male.

Table VI. — Preponderance of the sexual female of Chromaphis juylandicolaover themale.

Date of collection or count.

Number of

sexual
females to
each male.

Date of collection or count.

Number of

sexual
females to
each male.

September 15 . . .

62

October 24

13

23

71

November 2

28

30 ..

24
7.3
5.3

9

7

16

5

14. .

23

0)

1 None of either sex seen on leaves.

Table VI was compiled from the same material as that used for
Table V. On November 9 nearly all the sexual females were clus-
tered on the limbs, and two weeks later they and all other plant lice
at the experimental trees succumbed to a severe frost, which had
at the same time withered all the leaves. This clustering of the
sexual females or sexuparae about the limbs explains the small per-
centage of this form as compared with the males on November 9
and 16.

Copulation seems to occur only on the leaf, and the females are not
fertilized until they have passed through the last molt, A single
male may fertilize several females — probably quite a large number
when it is considered that the latter sex so greatly outnumbers the
former and that very few eggs prove infertile. Copulation in all
instances observed by the writer occupied some 30 seconds of time —
a very short period for an aphis. If the male be disturbed, he will
immediately retract his genital organ and move off. In 1912 the
males appeared in comparative abundance in the vicinity of San
Jose as early as August 26.

In general appearance the adult oviparous female differs from the
viviparous form in that it is wingless, has a wider body, and bears
three conspicuous transverse brown or black bands on the dorsum
of the abdomen. The male is greenish-yellow, winged, with black

WALNUT APHIDES IN CALIFORNIA.

15

Fig. 6. — ChromapMs juglandkola: Oviparous
female, penultimate instar. ( Original.)

or dusky gray legs and anteimse. The oviparous or sexual female
molts four times but does not differ in appearance from the viviparous
form until the third molt is passed.

THE OVIPAROUS FEMALE, AFTER THE THIRD MOLT (fIG. 6).

Rather smaller and narrower than the full-grown form. General color pale gamboge-
yellow, sometimes lemon yellow. Body twice
as long as wide. Eyes bright red. Head with
six erect, capitate spines on the anterior margin.
Antennae short, reaching barely to the middle of
the mesothorax; 7-jointed, joint III the longest,
joints IV and V subequal, joint VI longer than
its spur or filament. Spur dusky, rest of anten-
nae palti lemon yellow. Head, thorax, and ab-
domen with two longitudinal rows of oval black
spots on the dorsum. Thorax and abdominal
segments 1-5 with two lateral longitudinal rows
of circular black spots, on which are situated
small tubercles bearing capitate haii-s. Such
tubercles also occur on the black dorsal spots.
Eighth segment of the abdomen unmarked,
bearing on its posterior margin a fringe of six
capitate hairs. Legs pale greenish-yellow with
the characteristic knee spot on the hind femora
only; tarsi gray. Cornicles on the sixth segment, quite small, wider than long, pale
lemon-yellow. Cauda equal in length to the hind tarsus, pale yellow, rounded. Beak
very pale, almost white, reaching to the anterior coxae. Measurements: Length of

body, 1.51 mm.; width of body, 0.76
mm.; antennae, joint I, 0.063 mm.;
joint II, 0.048 mm.; joint III, 0.136
mm.; joint IV, 0.083 mm.; joint V,
0.085 mm.; joint VT, 0.08G mm.; fila-
ment, 0.021 mm.

Described from specimens
collected at Walnut Creek, CaJ .,
and San Jose, Cal., October 16
to 26, 1912.

THE OVIPAROUS FEMALE, ADULT STAGE
(fig. 7).

General color gamboge, varying in
newly molted examples to lemon yel-
low and in older individuals to salmon
pink or with a distinct brownish tint.
Eyes crimson. Head and prothorax
with indefinite dusky brown markings.
Ocular tubercles small. Anterior mar-
gin of the head with six capitate hairs
projecting forward. Thorax mottled all over with shades of brown, its lateral margins
lighter. Prothorax with two capitate hairs on either side of its posterior portion. Ab-
domen with two or three hairs on the lateral margins of each segment. Segments 4 and
5 and posterior half of 3 with dark brown or black markings which generally coalesce to

Fig. 7.-

-ChromapMs juglandkola: Oviparous female.
Right antenna. (Original.)

16 BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURil.

form tliree transverse bars or bands, of which those on segments 4 and 5 do not quite reach
the lateral margins of the segments, while that on the third segment is slightly shorter
and but half as broad as the others. Wings absent. Cornicles quite similar to those of
the winged viviparous female. Cauda globular, concolorous with the abdomen, larger
than that of the wdnged viviparous female. Anal plate large, U-shaped, extending
beyond the cauda when viewed from above. In reality it has a shallow incision at
the apex. Antennse on slight frontal tubercles, reaching to the middle of the meta-
thoracic segment, white, with the apices of joints 3 to 6 black. Legs very pale yellow,
almost hyaline; tarsi dusky gray at their apices. All six femora have the character-
istic black or brown knee spot. Beak yellow, the extreme tip black, reaching to the
second coxae. Hind tibia? not much swollen, bearing about 35 circular sensoria
occurring evenly on the middle two-thirds of the tibia and arranged in an irregular
spiral. Measurements: Length of body, 1.60 mm.; width of body, 0.81 mm.; an-
tenna, joint I, 0.06 mm.; joint II, 0.04 mm.; joint III, 0.22 mm.; joint IV, 0.125
mm.; joint V, 0.109 mm.; joint VI, 0. 081 mm.; filament, 0.023 mm. Cornicles, 0.06
mm. Cauda, 0.085 mm.

Described from specimens collected in the fall of 1911 at San
Jose, Cal.

THE FULL-GROWN MALE PUPA.

In its immature stages the male pupa resembles the oviparous
female. A description of a single full-grown male pupa taken at
San Jose, Cal., October 27, 1912, is as follows:

General color pale lemon yellow. Antennse pale, whitish, reaching to the anterior
margin of the metathorax; last three joints black or dusky. Head and prothorax
brownish. Eyes bright red. Wing pads very pale. Legs entirely whitish, only the
hind femora bearing the characteristic knee spot; tarsi dusky gray. Cornicles as
broad as long. Cauda very small, rounded, ('ornicles and cauda pale yellow. Head,
thorax, and abdomen with two longitudinal dorsal rows of oval black spots and with
two such lateral rows of circular black spots. On each of these spots is situated a tuber-
cle having a single capitate hair. Excluding the wing pads the body resembles that
of the immature sexual female. Measurements: Length of body, 1.01 mm.; width
of body, 0.50 mm.; antenna, joint I, 0.049 mm.; joint II, 0.035 mm.; joint III,
0.121 mm.; joint IV, 0.081 mm.; joint V, 0.087 mm.; joint VI, 0.063 mm.; filament,
0.023 mm.

THE WINGED MALE, ADULT STAGE (FIG. S).

General c-olor of the body pale yellow or greenish yellow. Head, prothorax, and
thorax grayish black. Scutellum black. Eyes bright red. Antennae not on frontal
tubercles, reaching to the posterior margin of the first abdominal segment, pale yellow;
joints I and II, the filament or spur, and the articulations of joints III to VI dusky
gray. These dark articular annulations are less pronounced than in the viviparous
female. Wings of medium size; costa, subcosta, and insertions pale yellowish gray;
stigma short and gray, with its central area paler; veins gray, second fork of third
discoidal nearer to the wing apex than to the first fork and arising beyond the apex
of the stigmatic vein; stigmatic vein evenly and gently curved, absent in the middle
for a space equal to one- third of its length. Legs longer in proportion to the body than
those of the other forms; fiont legs and middle tibiae very pale yellow or yellowish
green; distal two-thirds of the middle and hind femom shaded gray, the black knee
spot being present on these four femora; hind tibiae shaded gr&y for its proximal three-
fourths, its apical fourth pale yellow; all tarsi light gray. Abdomen barely as long
as the head and thorax combined, widest at the fourth segment, and with a pair of

Bui. 100, U. S. Dept. of Agriculture.

PLATE II.

Eggs of European Walnut Aphis (Chromaphis juglandicola) on
Piece of Bark of European Seedling Walnut. Twice Natural
Size.

WALNUT APHIDES IN CALIFORNIA.

17

oval gray transverse spots on the fifth, segment, which are separated by a space equal
to their length. Cornicles pale yellow, about as broad at the base as long, very much
as in the winged female. Cauda pale yellow, globular, not quite as long as the hind
tarsus. Sexual organ pale yellow. Beak pale yellow, slightly exceeding the fore
coxije. Sterna black. Sensoria transversely oval, situated in -an u-regular row as
follows; joint III, 11 to 16; joint IV, 5 to 7; joint V, 4 to 6; joint VI, 2 besides usual
terminal.

Measurements: Length of body (average), 1.47 mm.; width of body (maximum),
0.48 mm.; expanse of wings (average), 4.20 mm; antenna, joint I, 0.05 mm.; joint II,
0.04 mm.; joint III, 0.34 mm.; joint IV, 0.12 mm.; joint V, 0.12 mm.; joint VI, 0.08
mm. ; filament, 0.03 mm. ; cornicles, 0.05 mm.

Fig. 8. — Chrojnaphis juglandicola: Winged male (appendages of left side removed), a, Left antenna.

(Original.)

Described from many individuals collected in 1911 and ' 12 at
San Jose, Cal.

Both the male and the winged viviparous female nen disturbed
have a habit if jumping psyllid-Uke into the ax. Their flight is
generally in the form of a long spiral, and when disturbed they fly in
an upward direction.

EGG DEPOSITION.

As mentioned before, the first sexual females of the year remain
longer on the leaves after they have reached the adult state than
those developing later. In 1911 eggs were not observed in the
field until September, or seven weeks after the first appearance of
sexual females. In 1912 some eggs appeared in August. This long
period between the first appearance of the sexed females and the
40859°— Bull. 100—14 3

18 BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE.

earliest egg deposition may be explained by the fact that until late
in August males are quite scarce and so the females must wait on
the leaves until the males are developed. Directly after mating the
female repairs to the branches and limbs to deposit her eggs. Al-
though eggs may be deposited anywhere along the limbs, and more
rarely on the newer growth, the locations most preferred are the old
scars of fallen leaves and the surface of the larger limbs near their
bases. Another favored location is that in the crotches of the smaller
limbs. Eggs are rarely laid along the stalk of the leaf or at the base
of the leaflets, and if placed in those positions they fall to the ground
when the leaf drops. Cavities and interstices in the bark are also
chosen, but when infestation is very severe the eggs are laid in the
open on the larger limbs (see PL II). In such a case large groups of
eggs are massed together by many females, but a single female lays not
more than tlu-ec or four in a group. The eggs are fastened together
and to the plant surface by a thin, transparent, gluey substance. No
accurate information was obtained as to the number of eggs a single
aphis produced, but from general field observations together with
dissections of gravid females the writer arrived at the conclusion that
not more than 30 eggs fell to the share of each adult, and probably
not over half that number. On July 20, 1911, five gravid females
were dissected. These contained respectively 5, 3, 3, 4, and 4 well-
developed ova, besides about a dozen much smaller ones. On August
28, 1912, four oviparous females dissected contained respectively
2, 2, 4, and 2 fuU-grown ova besides about 20 much smaller ones. AU
these individuals were taken on the leaves and had not oviposited.
The largest eggs dissected were lozenge-shaped and measured 0.37
mm. in length by 0.14 mm. in width.

THE EGG (fig. 1; PL. II).

Wlien first laid, the egg is pale lemon-yellow or whitish yellow, oval,
almost twice as long as broad, flatter than most eggs of Aphidid?e,
and slightly broader at the micropylar end. After two or three days
it turns black and sliines obscurely when placed under a strong light.
The surface is beautifully sculptured with granular hexagonal mark-
ings. These markings are tliickened portions of the shell. The nar-
row intermediate portions of the shell are extremely thin, so much so
that four months after the egg has been laid the yellow interior sub-
stance is plainly visible through them if subjected to a liigh power of
magnification. It appears that about 85 per cent of the eggs are
fertile. The average size is 0.50 mm. by 0.28 mm. The egg stage
may be said to occupy, on the average, five months in CaHfornia.

WALNUT APHIDES IN" CALIFORNIA. 19

ANT ATTENDANTS.

The sweet juices excreted by the European wabiut apliis attract
hirge numbers of ants, of which a large black species, Formica sub-
sericea Say, is the most abundant. The author is indebted to ]Mr.
Theo. Pergande, of the Bureau of Entomology, Washington, D. C,
for the determination of this species.

THE AMERICAN WALNUT APHIS (Monellia caryae Monell).'

Callipterus^ caryae Monell, U. S. Geol. & Geog. Survey Bui. 5, No. 1, p. 31, Jan. 22,
1879.

Monellia^ caryae Gillette, Jour. Econ. Ent., v. 3, No. 4, p. 367, fig. 6, Aug., 1910.

HISTORY OF THE SPECIES.

This plant-louse was first collected in Missouri by Mr. J. T. Monell
in 1879. His original description is as follows:

Winged form; general color pale yellow; tips of antennal joints black; legs entirely
pale whitish. Antennae a little shorter than the body; seventh joint equal to or
one-third longer than the preceding; fifth joint as long as the two following taken
together. Nectaries not perceptible. Rostrum not reaching to the middle coxae.
Wings hyaline, veins pale; stigma rather short and blunt at the apex. Stigmal vein
subobsolete, its course being only traced with difficulty. The distance between the
apex of the lower cubital branch and that of the second discoidal equal to about
one-half the distance between the apices of the first and second discoidals. Apterous
viviparous females and pupaj with four rows of tubercles, each mounted with a capitate
bristle.

Leaves of walnut, hickory and pecan. June-July, St. Louis, Mo.

This aphis has been reported from lUinois (Thomas, 1880; Davis,
1910), Nebraska (WiUiams, 1910), Oregon (Gillette, 1910), and
Michigan (Gillette, 1910), and doubtless occurs in America wherever
its food plants grow.

GENERAL DESCRIPTION; CHARACTER AND EXTENT OF INJURY.

This apliis is about one-sixteenth of an inch long and about one-
third as wide and is generally of a pale lemon-yellow color. It
occurs on the lower surface of the leaf and on the nutlets of the
eastern black walnvit tree and crosses derived from it. Wlien infes-
tation is severe, the aphides wiU also be found on the upper surface
of the leaves. The species, according to IVIr. Monell and other
writers, feeds also on hickories and pecan. The character and extent
of its injury is altogether similar to that of the European walnut
aphis {Chroma pliis juglandicola Kalt.). This plant-louse does not he
so flatly appressed to the plant surface as the European species and
is much more active, bearing longer legs and antennae in proportion

1 Mr. J. T. Monell, of the Bureau of Entomology, has kindly identified the specimens sent to him by the
author as Monellia caryae Monell.

2 The genus Callipterus ("beautiful-winged") was erected by Koch (1855).

3 The genus Monellia was erected by Oestlund (1887), with caryella Fitch as the t3rpe species.

20

BULLETIN 100, U. S. DEPAETMENT OF AGRICULTURE.

to the size of the body. When on the lower surface of the leaflet it has
the habit of resting with the head directed straight toward the
peduncle of the leaflet. In July and August, in which months this
insect is most abundant, as many as 400 individuals may be found on
one leaflet, 5 per cent of which AviU be resting on the upper side. At
this time it is much sought after by ants, which feed on the liquid
excreted by it. A large red and black species, determmed by IVIr.
Theodore Pergande as Formica ohscuriventris Mayr, is a very common
attendant. Formica suhsericea Say also attends it. The sweet excre-
tions of the apliis attract many flies of the families ^Muscidse, Anthom-
yiidae, Oscinidse, and Syrphid?e, many large bees including the
honeybee, wasps of the f anuly Pompihdse, and parasitic wasps of the
famiUes Iclmcumonidse and Braconidse, and numerous smaller forms
of insect life. The author fii'st observed this aphis on July 20, 1911,
at San Jose, Cal.

life history and technical descriptigns.

The Viviparous or Asexual Forms.

The stem-mothers hatch as soon as the buds start to swell, about
the 1st of April. These develop into mnged aphides and pass their
life cycle in from 25 to 30 days, according to temperature and the
amount of food supply. The viviparous aphis passes through four
molts, becoming winged after the fuial one. Table VH indicates the
life cycle of 38 individuals of the summer generations.

Table VII.^ — Life-cycle of viviparous females of Monellia caryae, summer generations,

San Jose, Cal, 1912.

No. of indi-
vidual.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19

Gener-
ation.

II
II
II
II
II
II
II
III
III
III
III
III
III
III
III
III
III
V
V

Date of
deposi-
tion.

Apr. 22
22
22

Mav 1
1
1
1
13
13
13
13
13
13
13
13
13
13

June 22

Date of

acquiring

wings.

May 12
12
12
20
22
23
23
29
29
29
29
29
30
30
30
30
30
4
7

July

Life
cycle.

Days.
20
20
20
19
21
22
22
16
L6
6
6
6

No. of indi-
vidual.

Gener-
ation.

V

V
V
V
V
V

^'

V
V
V
V
V
V
V
V
V
V
V
VI

Date of
deposi-
tion.

June 22
23
23
24
24
24
24
24
24
25
25
25
25
25
27
27
27
27

July 13

Date of
reaching
maturity.

July 7

7
7

8
8
9
10
10
10
10
Aug. 1

Life
cycle.

Days.
15
14
14
13
13
13
14
14
14
13
13
13
13
14
13
13
13
13
19

Thus, the second generation requires 20 days, the third 16 or 17,
and the fifth 15, in which to complete the Hfe cycle. Records of the
fourth generation were not obtained owing to premature death of all

WALNUT APHIDES IN CALIFORNIA.

21

individuals of this generation of which the date of deposition had
been ascertained. Individuals of the fourth generation probably
mature in an average of 16 days. The" leaves of the Eastern black
walnut fall earUer than those of the European or California black
types, and consequently the viviparous apliides are not found so late
on the trees. There are probabl^^ not more than nine generations of
these in a year.

Immediately after passing the final molt the aphides begin depos-
iting young. These are entirely pale lemon-yellow with red eyes
and four longitudinal rows of capitate hairs and do not exceed 0.70
mm. in length. From 10 to 20 young are produced by a single female,
dependent on the season of the year. The earher generations are
more prohiic. After midsummer the progeny becomes smaller and
smaller with successive broods.

THE PUPA OP THE WINGED VIVIPAROUS FEMALE (PIG. 9).

After the second molt the pupal wing pads are apparent as small
emarginations on the sides of
the thorax, but after the fol-
lowing molt they are much
more readily seen. The pupa
of the winged viviparous female
may be described as follows :

Color generally pale lemon-yellow,
sometimes white; head often with a
reddish tinge. Antennse on small
frontal tubercles, pale yellow, with
the filament and articulations of joints
3 to 6 dusky black. Eyes bright red.
Thoracic segments and wing pads
light yellow, wing pads projecting
out from the body at a very acute
angle. Legs pale, tarsal apices dusky.
Body beset with long capitate spines
in four rows. Cornicles on segTaent 6
of the abdomen, hardly perceptible,
broader than long. Cauda blunt,
conical, and short. Cornicles and cauda concolorous with the abdomen. Beak
pale, reaching to the middle coxae. Measm-ements: Length of body (average), 1.87
mm.; width of body (average), 0.71 mm.; antenna, joint I, 0.058 mm.; joint II, 0.050
mm.; joint III, 0.287 mm.; joint IV, 0.207 mm.; joint V, 0.201 mm.; joint VI, 0.128
mm.; filament, 0.136 mm.

This pupa is distinguishable from that of Chromaphis by the pres-
ence of the dorsal rows of spines and by the absence of the black
femoral spots. The penultimate instar occupies on the average four
or five days. At its termination the final molt occurs, and after this
the insect has acquired its full development.

Fig. 9.-

MoneUia caryas: Pupa of winged viviparous
female. (Original.)

22 BULLETIN 100, U. S. DEPARTMENT OF AGKICULTUKE.

THE WINGED VIVIPAROUS FEMALE (FIG. 10).

General color pale lemon-yellow; many examples are greenish yellow and others
decidedly pinkish. Head, thoracic lobes, and scutellum pale hrown or yellowish
brown. Eyes pink. Antenna? on small frontal tubercles, about half as long as the
body, pale yellow, with articulations of joints III to VI black; joint "ill the longest,
not noticeably thickened basally; joint IV slightly longer than V and barely as long
as joint VI, together with its spur or filament. Bases of antennae encircled, in the
majority of individuals, with a narrow dusky ring. Close to the lateral margins of
the prothorax and roughly parallel to them occur two narrow black lines. (These are
sometimes absent.) Wings of moderate size; costa, subcosta, and stigma^pale yellow-
ish green, other veins light brown, of medium thickness. Stigmatic vein entirely
subobsolete, its coirrse not easily made out. Legs very pale, whitish, tarsi and apex

Fig. 10. — Monellia caryse: "Winged viviparous female, a, Antenna. (Original.)

of tibiae dusky grey; anterior and posterior femora in about half of the individuals
bear a grey knee spot cjuite like that of Chromaphis juglandicola Kalt. but smaller.
This spot never occurs on the middle femora. Abdomen pale yellow, sometimes
greenish and at other times reddish, with four rows of small black spots, which are
very variable and often wholly absent. The two lateral rows have larger spots and
these are found on segments 2-6; the two median rows are smaller and their spots
exist on segments 2-8. Cornicles on segment 6, hardly perceptible, more than twice
as broad as long, about 0.008 mm. long. Cauda globular, shorter than the hind tarsus.
Cornicles and cauda concolorous with the abdomen. Anal plate bifid, armed with
spines. Beak pale, extreme tip brown and not quite extending to the second pair of
coxae. Sensoria occur on the antennae as follows: Joint III, 6-9 transversely oval on
basal half or two-thirds of joint; in an equally spaced row; joint V, 1 terminal; joint VT,
4 terminal (1 large, 3 small). Measurements: Length of body, 2.16 mm.; width of

WALNUT APHIDES IN CALIFORNIA. 23

body, 0.754 mm.; wing expanse, 4.44 mm. Antenna, joint I, 0.076 mm.; joint II
0.060 mm.; joint III, 0.416 mm.; joint IV, 0.273 mm.; joint V, 0.273 mm.; joint VI,
0.143 mm.; filament, 0.164 mm.

Described from many specimens taken at San Jose, Cal., during
1911 and 1912.

The complete absence of the stigmatic vein and the relatively
longer antemise, together with the diminutive cornicles, will readily
distinguish this species from the European walnut aphid.

In 18 months' study of this plant-louse the author has failed to
find any trace of the existence of a wingless viviparous form.

The Oviparous or Sexual Forms.

If a tree be heavily infested, the sexual forms appear first about the
middle of July and probably belong to the fifth and sixth generations.
If infestation be only moderate or shght, these forms are not pro-
duced until several weeks later and will be members of the seventh
and following generations. The sexod forms from the beginning are
produced in comparative abundance and comprise from 30 to 50
per cent of the whole. The young sexed females are paler and more
spindle-shaped than the young of the viviparous individuals, while
the male larvae and pupae are conspicuously brick-red in color. The
male is not so greatly outnumbered by the female as in the European
walnut aphis, and from the first comprises from 20 to 30 per cent of
the sexed insects. On August 26 and 27 and September 5, 1912, a
count of the forms on 34 leaflets taken at random from an Eastern
black walnut tree showed 177 viviparous females, 14 males, and 26
sexed females. Probably as many again of the sexed females in
proportion to the leaflets counted could be found on the twigs
ovipositing. Copulation takes place on the leaf and occupies half a
minute. All through August and September, 1912, the oviparous
females were observed on the twigs, but few eggs were found until
September. After the middle of September few apliides were found,
the great majority having been destroyed by their natural enemies,
but those that escape perpetuate the species until the leaves fall in
November. The majority of aphides born in the late fall are sexual.
The sexed female shortly after mating becomes much swollen by
reason of the growing ova in her body, and the last four abdominal
segments become orange colored. She repairs to the twigs and limbs
and wanders around searcliing for locations wherein to oviposit.
Occasionally immature females wander off to the twigs, but later
return to the leaves to resume feeding. The fully mature fertilized
oviparous female once she has forsaken the leaf rarely if ever returns,
and thus escapes many predatory foes. Having found a crevice or
crack in the cortex suitable for her purpose she grips the limb with

24 BULLETIN 100, U. S. DEPARTMENT OF AGRICULTUEE.

her six legs and bends the hind part of the abdomen at a right angle
to the rest of the body and then gives her abdomen a succession of
jerks to get it into place. This performed to her satisfaction, she
remains motionless for 60 seconds while the egg is being extruded, and
after depositing it walks off. The writer has never seen the eggs of
this species placed in an open situation, but always in some protected
position in the bark. On August 28, 1912, four gravid females were
dissected and were found to contain respectively 3, 4, 2, and 4 large
eggs, and all had several smaller ones. Another had 8 large eggs in
her ovaries and was greatly distended therefrom. The egg is bluntly
oval, bright yellow when first laid, but changing in a day or two to
black and obscurely shining. It measures 0.35 mm. in length and
0.17 mm. in width, and is therefore considerably smaller than the

egg of the European walnut plant-louse.

The oviparous forms are described below.

THE OVIPAROUS FEMALE, FULL GROWN (fIG. ll).

General color pale greenish yellow or sometimes
greenish white, the four apical segments of the
abdomen at first colored like the rest of the body
and later orange colored. Body rather narrow,
not at all flattened, the sides nearly parallel and
produced posteriorly into a conical tube. An-
tennae a little over one-half the body in length,
I^ale, with the apical third or fourth of joints III
to VI dusky gray; joint II gray and armed with
a capitate spine on its inner margin; joint III
longest; joints IV and V subequal; joint VI
shorter than its spur or filament. Legs very pale

,, „. ^ . yellow, with a dark spot close to the apex of the

IiG. 11.— Monelha caryx: Oviparous •' . , . \ ,_ .....

female. (Original.) anterior and posterior femora. (In many individ-

uals these spots are absent.) Eyes pink. The
arrangement of capitate spines is as follows: The head bears eight, the prothorax
six, the mesothorax, metathorax, and abdominal segments 1 to 5, inclusive,
four, and abdominal segments 6, 7, and 8 two; these spines appear as four lon-
gitudinal rows. Cornicles greenish yellow, broader than long, hardly percep-
tible, located on segment 6. Cauda concolorous with the body, globular, armed
with four noncapitate spines, half as long as the hind tarsus. Genital plate protrud-
ing beyond the cauda, pale, its margin beset with short noncapitate hairs. Beak
pale, its extreme tip brownish, just exceeding the second pair of coxse. Measure-
ments: Length of body, 1.68 mm.; width of body, 0.72 mm.; cauda, 0.038 mm.;
antenna joint I, 0.04 mm.; joint II, 0.035 mm.; joint III, 0.300 mm.; joint IV,
0.17 mm.; joint V, 0.17 mm.; joint VI, 0.100 mm.; filament, 0.12 mm.

Described from many specimens collected at San Jose, Cal., during
1912.

WALNUT APHIDES IN CALIFORNIA. 25

YOUNG MALE PUPA.

Light red in general color; appressed closely to the leaf surface. Dorsum of head
in front black, behind gray. Dorsum of thorax gray. Antennae six-jointed (i. e.,
with five joints and filament), one-third as long as the body, pale gray. Eyes bright
red . Legs pale, femora dusky gray. Mesothorax, metathorax, and first five abdominal
segments each with four black spots in a transverse row. Abdominal segments 6 to 8,
inclusive, with two such spots. A single capitate spine arises from each of these
spots. Cornicles imperceptible. Cauda pale, short, conical. Beak pale, tip dusky
gray, reaching first coxae.

FULL-GROWN MALE PUPA (fIG. 12).

General color pale brick red; head pale orange. Antennae half as long as the body,
seven-jointed, pale yellow, with dusky articulations. Eyes bright red. Legs very
pale, femora usually slightly dusky. Wing pads white. Whole body with four
longitudinal rows of dark capitate spines distributed as in the oviparous female.
Cornicles on segment 6, appearing as little rims on the body surface, broader than
long, concolorous with the body. Cauda bhmtly conical, A'ery short, pale yellow.
Beak pale yellow, extreme tip brown, reaching to the

first pair of coxae. Measurements: Length of body, ^ »

1.58 mm.; width of body, 0.57 mm.; Cauda, 0.045 mm. tt^ J^t^U^k!^ ft

Antenna, joint I, 0.071 mm.; joint II, 0.054 mm.; >|\ if m'\^"^y%%. i

joint III, 0.257 mm.; joint IV, 0.173 mm.; joint V, ^^^^:^:^^"i~iv:=^^

0.200 mm.; joint VI, 0.12 mm.; filament, 0.12 mm. /^_.7^--4_^\

Described from several specimens col- /<f^ /'^^ *^"^r^X
lected at San Jose, CaL, in 1912. I [ h^f "^3^) m,

WINGED MALE (fIGS. 1.3; IS, a). Jf /I/^^^^^^'F H ^^^^X^s.

General color pale lemon-yellow or greenish yellow; | 'V„^ \^^ i

head and a median quadrilateral area on thorax dark ^ ^i^~J\J^ 11

brown; scutellum dark brown; eyes dark red. An- i/ ^%E;k^ ll

tennae not mounted on frontal tubercles, about as long M ^^ ^

as the body ; joints I and II with a dusky central part ;

. . _^-r'^, %^^ , •,!.,• ■ 1 , Fig. 12.— J/onrfZio coruav Male pupa.

joints III to VI pale, with their apices dusky gray; (Original )

filament pale; joint III longest, bearing about 24

small oval sensoria; joints IV and V subequal, both bearing 10 to 15 small sensoria
arranged along the outer margin; joint VI bearing 4 sensoria, of which the most
distal is apical; joint VI longer than the filament, the two together scarcely as
long as joint V. Ocelli distinct. Wings of medium size; costa and insertions
greenish yellow; stigma short and moderately broad, dusky gray, with a large paler
central area; veins brown, the third discoidal curving considerably to meet its
second fork; second fork twice as near to the first fork as to the apex of the wing;
stigma tic vein obsolete in its middle portion. Legs longer in proportion to the body
than in the winged viviparous female, pale greenish yellow, with a large dusky area
near the apex of all six femora; apices of tibiae and tarsi dusky gray. Abdomen
short, not quite as long as the head and thorax together, widest at the third segment;
segments 1 to 7, inclusive, with two lateral black spots, one on each side; segments
1 to 6, inclusive, and segment 8 with two dorsal black spots, one on either side of the
dorso-median line; the lateral spots on segments 1 to 6, inclusive, are circular or sub-
circular; the dorsal pairs on these segments are oval; the dorsal spots on segments 6
and 8 coalesce narrowly in the middle. Cornicles on segment 6, hardly perceptible,
broader than long. Cauda globular, dusky, half as long as the hind tarsus. Repro-

26

BULLETIN 100, U. S. DEPARTMENT OF AGEICULTURE.

ductive organ white, when extended about as long as antennal joint IV. Beak pale
yellow, extending a little beyond the first pair of coxae. Sterna and ai^ical half of
the underside of the head dark brown. Very often one or more of the dusky abdominal
spots are absent. Measurements: Length of body, 1.39 mm. ; width of body, 0.69 mm. ;
wing expanse, 4.10 mm.; cauda, 0.049 mm.; antennal joint I, 0.051 mm.; joint II,
0.058 mm.; joint III, 0.362 mm.; joint IV, 0.238 mm.; joint V, 0.240 nam.; joint
VI, 0.114 mm.; filament, 0.134 mm.

Described from four specimens collected at San Jose, Cal., in 1912.

Fig. 13. — MoneUia caryx: Winged male, a, Iveft antenna. (Original.)

THE LITTLE HICKORY APHIS (Monellia caryella Fitch).

Aphis caryella Fitch, [First] Report on the noxious, beneficial, and other insects

of the State of New York, Albany, p. 163-165, 1855.
Callipterus caryellus Fitch, Third report on the noxious and other insects of the

State of New York, Albany, p. 448-449, 1856.
Monellia caryella, Oestlund, Geol. & Nat. Hist. Survey Minn. Bui. 4, p. 45, 1887.

HISTORY OF THE SPECIES.

The little hickory aphis was first collected in New York State by
Dr. Asa Fitch, previous to the year 1855. The following is Fitch's
original description :

The Little Hickory Aphis (Aphis caryella) is pale yellow with white antennae which
ai'e alternated with black rings, the wings are transparent and without spots, their
veins slender and pale yellow, the legs yellowish white to their ends. Length 0.12
to the tips of the "wings. The abdomen is depressed, egg-shaped, its apex slightly

WALNUT APHIDES IN CALIFORNIA. 27

narrowed and elongated. The antennae are longer than the body, tapering, seven-
jointed; two basal joints as broad as long, twice the diameter of the followmg joints;
third joint longest, slightly thicker towards its base; fourth and fifth joints rathershorter
than the third, cyliudric; two last joints together about equalling the fifth in length;
the sixth swelled at its tip into a long oval knob, the seventh more slender but not
capillary, shorter than the sixth; a broad black band at the base of the third and each
of the following joints. First vein of the fore wings straight and almost transverse;
second vein bent near its base, running first towards the apex and then turning rather
abruptly and continuing straight to the inner margin, more than twice as far from the
first at tip as base; third vein arising from the stigma near its anterior end, and not
from the rib-vein forward of the stigma, as it does in the aphides generally, except
those pertaining to this group, its base and its apex about the same distance from the
second vein that this is from the first, forking rather forward of its middle, strongly
bent at this point, and from hence to its tip parallel with the third vein or but slightly
diverging from it, its tip a thhd nearer that of the third vein than this is to the second ;
second fork nearer the fourth vein at tip than to the first fork, the triangular cell be-
tween it and the first fork with its three sides equal; foiu-th vein short and often nearly
abortive, shorter than the second fork, equally curved through its whole length, its
tip much nearer that of the rib-vein than that of the second fork ; rib- vein very slightly
diverging from the margin from the base to the stigma, curved from thence to its tip.
Stigma oval, about twice as long as wide, watery, sometimes tinged with yellowish. A
variety Jias the stigma dusky at its tip. Another variety (costalis) has the rib-vein
coal black interrupted with whitish towards the stigma, which is dusky and black at
each end.

In a general discussion of this species before his description Fitch
refers to the minute cornicles characteristic of this and kindred
species. In his third report on the insects of New York he mentions
the European walnut aphis and says "European C. juglandicola of
Koch" [Clwomapliis juglandicola Kalt.] "appears closely related to
this present species" [i. e. Callijiterus caryellus]. Fitch gave the
host plant of his species as the hickory. Oestlund (1887) reports it
in IMinnesota from Carya amara Nutt. Davis (1910) and other Eastern
writers record it from hickory in the Eastern States. In Cahfornia
the normal food plants are the California black wahiut (Juglans
californica) and hybrids derived from this tree.

GENERAL APPEARANCE; CHARACTER AND EXTENT OF INJURY.

In general appearance this aphis is very similar to the American
walnut aphis (Monellia caryse MoneU) and can not be distinguished
from it except when viewed under the microscope or a powerful hand
magnifier. Its habits of hfe and the character and extent of its
injury are also very similar to those of M. caryse. The writer had
observed this aphis for several months before he realized that it was a
distinct species and not a variety of caryse, as he had previously
supposed. When the sexed forms appeared it was noticed that the
oviparous female of caryella differed markedly from the same form
of caryse, and this led to a closer scrutiny of the viviparous form
resulting in the establishment of the points of divergence shown in
Table VIII.

28

BULLETIX 100, U. S. DEPAETMEXT OF AGRICULTURE.

Table VIII. — Divergences of structure between Jlonellia caryx Monell and M. caryella

Fitch.

yfcynellia caryx Monell.

Monellia caryella Fitch.

"Winged viviparous female.

Pupa of viviparous female .
Oviparous female

Antennal joint III very slightly
thickened basally.

Sensoria on antennal joint III
occupving basal half or two-
thirds".

Antennal joint VI and its spur or
filament subequal, or VI less
than spur.

Dusky Imee spots often present.

Four longitudinal rows of capitate
spines.

Smaller than the viviparous fe-
male.

Four longitudinal rows of capitate
spines.

Antennal joint III quite notice-
ably thickened for its basal half.

Sensoria on antennal joint III oc-
cupying basal third.

Antennal joint VI one-third as
long again as its spur or filament.

Dusky knee spots absent.

Six longitudinal rows of capitate
spines.

Larger than the viviparous fe-
male.

Six longitudinal rows of capitate
spines.

LIFE HISTORY A^a) TECHNICAL DESCRIPTIONS.

Life-KistorY studies on this plant-louse began iii August, 1912, at
San Jose, CaL, but no rearing work was done until the appearance
of the sexed forms in September. Observations taken in August
and September indicated a development of the summer generations
similar to that found in Monellia caryx. This was further confirmed
by studies during 1913. The sexed forms were studied at Wahiut
Creek and San Jose, Cal. In both localities these did not appear until
late in September, even on trees heavily infested. The aphides re-
mained on the trees as long as there were leaves on which they could
subsist and were to be found until mid-Xovember. After September
the great majority of aphides deposited were oviparous, and of these
the males were extraordinarily scarce, the writer observing only one
individual of this sex among hundreds of oviparous females. Table
IX indicates the life cycle of plant-hce deposited by four viviparous
females and shows the preponderance of the sexed form over the
asexual m the late fall.

Table IX. — Life-cycle record of the progeny of four viviparous females of Monellia

caryella, Walnut Creek, Cal., 1912.

FEMALE NO. 1; DEPOSITED 3 YOUNG.

Date of—

No. of larva.

Hatch-
ing.

Molt L

Molt 2. Molt 3.

Molt 4
(becom-
ing
adult).

Form of individual.

Life
cycle.

1

Oct. 4
•t

Oct. 7

7

Oct. 10
11

(?)
(?)

Oct. 16
18

Winged viviparous fe-
male.

Oviparous female

do

Bays.
12

2

14

3'

1

! 1

FEMALE NO. 2; DEPOSITED 6 YOUNG.

Oct. 12

Oct. 15

Oct. 18

Oct. 21

Oct. 28

12

1.5

18

21

28

12

15

19

22

29

12

15

19

23

30

12

(?)

(?)

(?)

29

12

(?;

(?)

(?)

30

Oviparous female.

do

do

do

....do

....do

1 Died permaturely.

WALNUT APHIDES IX CALIFOEXIA.

29

Table IX. — Life-ojde record of the ■progeny of four viviparous femahs of Monellia
caryella, Walnut Creek, CaL, 1912 — Continued.

FEMALE NO. 3; DEPOSITED 16 YOUNG.

Date of—

No. of larva.

Hatch-
ing.

Moltl. Molt 2. ; Molts.

Molt 4
(becom-
ing
adult).

Form of individnal.

Life
Cycle.

101.
111.
IIK
131.
141.
151-
161.

Oct. 16
16
16
17
17
17
17
18
18

Oct.

(?)
(?)

<P
(?)
(?)

(?)
(?)
(?)
(?)
(?)
(?)

Nov.

(?)
(?)
(?)
(?)
(?)
(?)

Nov.

I Oviparons female.

' do

I do

I do

do

I do

do

.do-
-do.
-do.
.do.
-do.
-do.
.do.
.do.
-do.

Days.
22
22
22
22
22
22
22
21
22

FEMALE NO. 4; DEPOSITED S YOUNG.

1

2

3

4

51

Oct. IS Oct. 22
IS 1 22
IS 22
IS 22

Oct. 27
27
27
27

Nov. 2
3

4

4

Nov. 7
9
9
9

0 viparous female

.....^0

do

do

do

20
22
22
22

6'

do

71

do

gj

do

Died prematurely.
SUMMARY.

Life cycle (30 oviparous females).

Davs

Maximum.

Minimum

Average

First instar (13 individuals), average —
Second instar (13 individuals), average..
Third Instar (11 individuals), average...
Fourth instar (11 individuals), average .

The riviparous forms, so far as the author has observed, all
develop wings.

The eggs of this aphis are larger than those of the American walnut
aphis and measure on the average 0.536 mm. in length and 0.222 mm.
in maximum width. Ther are elongate-oval in shape, rather feebly
shining, and have a softer shell than is found in the egg^ of the
majority of plant-lice, but one not so soft as is that of CTiromapTds
juglandicola . They are placed either singly or in groups of two or
three ai'ound the axils of the buds or m crevices in the bark and in
scars caused by fallen leaves on the smaller limbs and twigs. Ovipo-
sition is in. progress during the months of October and November, each
oviparous female laying on the average about 12 eggs. Owing to the

30 BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE.

scarcity of males in the fall of 1912 at Walnut Creek, Cal., it seemed
very probable that a largo proportion of the eggs would prove to be
sterile, and in the followuig spring examinations of egg-infested trees
showed this assumption to be correct.

The Viviparous Forms.

The stem-mothers commence hatching very shortly after the leaf
buds open in the latter part of March. Previous to the first molt
they are pale lemon-yellow with red eyes, hyaline legs, and dusky
tarei; the joints of the antennae have black articulations; on the
abdomen are four longitudinal rows of circular dusky spots from each
of which arises a capitate spine. They are destined to become winged
and in their later stages do not differ from the summer winged
viviparous individuals.

Fig. 14. — Monellia caryclla: Pupa of winged viviparous female. (Original.)
THE PUPA OP THE WINGED VIVIPAROUS FEMALE (fIG. 14).

General color pale lemon-yellow; some individuals exhibit a decided greenish,
others a decided salmon colored tinge. Antennae two-thirds of the body in length;
apices of joints III to VI and the whole filament dusky, otherwise pale yellow, almost
white. Eyes bright red. Head with eight capitate spines, six of these on the frontal
margin and two near the hind border. Prothorax with six capitate spines, two of
these near the middle of the segment and four in a transverse row along the hind
margin. Mesothorax, metathorax, and abdomen with six longitudinal rows of capitate
spines. Legs pale yellow, tarsi dusky. Wing pads pale, after being imbedded in
balsam for a few days becoming dusky. Cornicles barely perceptible, wider than
long. Cauda rounded, not as long as the hind tarsi and without hairs. Beak pale
with a brown tip, almost reaching the second pair of coxse. Measurements: Length
of body, 1.81 mm.; width of body ,'0.72 mm.; antenna, joint I, 0.070 mm.; joint ET,
0.050 mm.; joint III, 0.253 mm.; joint IV, 0.198 mm.; joint V, 0.183 mm.; joint VI,
0.134 mm.; filament, 0.105 mm.

Described from four specimens. Walnut Creek, Cal., October, 1912.

WALNUT APHIDES IN CALIFOENIA.

31

THE WINGED VIVIPAROUS FEMALE (fIG. 15).

General color pale lemon-yellow, somewhat varying in shade. Antennae about
fonr-fifths as long as the body, pale yellow, with joints III to VI, inclusive, bearing
an apical black ring (on joint III this ring is narrower than the other joints); fila-
ment of joint VI dusky; joint III is the longest; joints IV and V subequal or joint IV
• slightly longer than V; joint IV about four-fifths as long as III; joint VI together with
its filament about equal to V; filament about three-fourths as long as VI; basal third
of joint III noticeably swollen and bearing from five to seven oval transverse sensoria;
usual apical sensoria on both joints V and VI. Head pale yellow, with the frontal
margin black. Eyes bright red. Prothorax pale yellow, with two narrow, black,
longitudinal stripes arising from the anterior angles and extending for two-thirds

Fig. 15.-

-MonclUa caryella: Winged viviparous female,
number of sensoria.

a, Right antenna, enlarged, with variations of
(Original.)

of its width. Thoracic lobes and scutellum light brown, sometimes with a salmon-
pink tinge. Wing insertions, costa, subcosta, and stigma pale lemon-yellow; dis-
coidals yellowish -b rown ; first and second discoidals heavier than the other veins;
third discoidal obsolete at its immediate base, its first fork equidistant from the
second fork and the base of the discoidal, its second fork nearer to the first fork than
to the apices of its two branches; branches of second fork equal in length; stigmatic
vein very weak, its basal half traceable only with difficulty; lower wing colorless.
Legs pale yellow; tarsi and tibial apices dusky. Abdomen entirely pale lemon-
yellow, the body widest at the third segment. Body somewhat narrowed laterally.
Cornicles pale yellow, hardly perceptible, wider than long. Cauda globular, bearing
a fringe of weak hairs, about equal in length to the hind tarsi, concolorous with the
abdomen. Genital plates armed with weak hairs, pale yellow. Beak pale yellow,
its extreme tip bro^vn, extending halfway between first and second coxas. Measure-

32

BULLETIN 100, U. S. DEPARTMENT OF AGEICULTUEE.

ments: Length of body (average), 1.67 mm.; width of body (average), 0.61 mm.;
wing expanse (average), 4.02 mm.; antenna, joint I, 0.053 mm.; joint II, 0.046 mm.;
joint III, 0.41 mm.; joint IV, 0.335 mm.; joint V, 0.32 mm.; joint VI, 0.191 mm.;
filament, 0.123 mm.; caiida, 0.084 mm.; Cornicles, 0.009 mm.

Described from numerous specimens, Walnut Creek, Cal., October,

1912.

The Oviparous Forms.

THE OVIPAROUS FEMALE (fIG. IC).

Wingless. General color pale lemon-yellow, iu mature individuals the central part
of the abdomen diffused with orange. Body elliptical, "widest at the third abdominal
segment. Antennae half as long as the body, not on frontal tubercles, pale, with

Fig. 16. — MonelUa caryella: Oviparous female. (Original.)

an apical black ring on joints III to VI, inclusive; joints I, II, and filament dusky;
joint in longest; joints IV and V subequal and each about four-fifths as long as joint
III ; filament a Little shorter than VI; VI about four-fifths as long as V. Eyes crimson.
Legs pale yellow; tarsi dusky. Hind tibiae slightly thickened. Cornicles very
small, pale. Cauda i^ale, globular, beset Avith a fringe of weak hairs, not as long as
the hind tarsi. Thorax and abdomen with six longitudinal rows of capitate bristles,
each surmounting a pale tubercle. Penultimate segment of the abdomen encircled
near its posterior margin with a fringe of weak hairs. Eight capitate spines on the

WALNUT APHIDES IN CALIFORNIA.

33

head and six on the pro thorax. Tibiae armed with a row of short bristlea on their
inner margins. Beak pale, the extreme tip dusky, extending a little beyond the
anterior coxse. The young o\'iparous female is entirely pale yellow and can be dis-
tinguished from the young viviparous female only by its more eliptical shape, that
of the latter being more oval. Measurements: Length of body, 1.89 mm.; width of
body, 0.92 mm.; antenna, joint I, 0.075 mm.; joint II, 0.042 mm.; joint III, 0.312 mm.
joint IV, 0.203 mm.; joint V, 0.218 mm.; joint VI, 0.167 mm.; filament, 0.108 mm.
Cauda, 0.080 mm.; cornicles, 0.009 mm.

Described from numerous specimens, Walnut Creek, Cal., October,
1912.

WINGED MALE (fIGS. 17; IS, 6).

General color pale green or greenish yellow. Head and prothorax olive-green.
Frontal margin of head and frontal margin of prothorax, black. Prothorax with two

ViG.n.— MonelliacaryeUa: Winged male. (Original.)

blimtly rounded dusky tubercles on the dorsum. Dorsum of head and thorax with
indefinite dusky markings. Eyes red. Antennae dark olive-green, about three-
fourths of the body in length; joiat VI longer than its filament. Sensoria as follows:
III, about 21: IV, 7 to 9; V, 6 to 10; VI, 2 to 4 (besides the usual apical). Wings of mod-
erate size; insertions and subcosta greenish -y ellow ; stigma light brown, with a paler
central area ; discoidals 1 and 2 thicker than the other veius and with a narrow smoky
border; stigmatic vein obsolete except for its apical thu'd; veins brown. Legs pale
greenish-yellow; coxse, trochanters, apical five-sixths of femora, and basal four-fifths
of tibiae black; tarsi gray. Thoracic lobes and scutellum black. Under the wings

34 BULLETIN 100, U. S. DEPARTMENT OF AGRICULTUEE.

occurs a large black spot on the pleura.
Abdomen unarmed, pale green or green-
ish yellow; segments 1 to 8, inclufiive,
with two dusky brown oval spots on
each. Cornicles pale, concolorous with
the body, very small, considerably
broader than long. Cauda concolorous
with the abdomen, globular. Abdomen
about as long as head and thorax com-
bined, not wider than the thorax.
Beak pale, barely reaching second
coxae. Sternum and underside of the
eighth abdominal segment black.

Measurements: Length of body, 1.57
mm.; width of body, 0.62 mm.; ex-
panse of wings, 4.62 mm.; antenna,
joint I, 0.080mm.; joint II, 0.041 mm.;
joint III, 0.412 mm.; jomt IV, 0.317
mm.; joint V, 0.260 mm.; joint VI,
0.175 mm.; jaiament, 0.108 mm.; cauda,
0.067 mm.; cornicles, 0.009 mm.

Described from three speci-
mens, Walnut Creek, Cal., 1912
and 1913.

MONELLIA CALIFORNICA Essig.

Monelha californicus Essig, Pomona
Jour. Ent.,v.4, no. 3, p. 767, Nov.,
1912.

In southern California feeding
on the underside of the leaves of
the California black walnut
(Juglans californica) there has
recently been found a plant-
louse closely allied to MoneUia
caryse and M. carijella. The
wi-iter has never seen this aphis
in natuie, but has received speci-
mens from Mr. Essig, who de-
scribed it.

KEY TO THE SPECIES OF MONEL-
LIA KNOWN TO OCCUR IN CALI-
FORNIA.

The following key will serve
to distinguish the four species
of walnut aphides occurring in
California.

Fig. 18.— a, MoneUia caryse, antenna of male;
h, MoneUia caryeUa, two views of right an-
terma of male. (Original.)

WALNUT APHIDES IN CALIFORNIA. 35

Key to the Species of Aphidid^ Known to Occur on Walnut in California.

A. Cornicles quite evident, about as Avide as long.

ChromapJiis jiiglandicola Kalt.
AA. Cornicles barely perceptible, considerably wider than long.
B. Tibiae of winged \'iviparous female entirely dusky.

Monellia californica Essig.
BB. Tibiae of winged viviparous female for the most part pale.

C. Filament of joint VI longer than joint VI; oviparous female with

four longitudinal rows of capitate hairs Monellia caryx Monell.

CC. Filament of joint VI shorter than joint VI; oviparous female with
six longitudinal rows of capitate hairs Monellia caryella Fitch.

NATURAL CONTROL OF WALNUT APHIDES.

INTERNAL PARASITES.

In July, 1912, a small chalcidid wasp was observed ovipositing in
a pupa of Monellia caryx. Tliis is the only record of parasitism or
attempted parasitism observed during two seasons, so there is good
reason to believe that these aphides are practically immune from the
attacks of internal parasites.

FUNGOUS DISEASES.

Although occasionally a plant-louse may be noticed here and there
killed by fungus, only a single instance of the destruction of a colony
by this agency came under the writer's notice. This occurred on
May 20, 1911, following a rainstorm, and all the plant-lice on a few
leaves were destroyed. The disease did not spread far, some cause
or other checking the fungus shortly after its appearance.

PREDACEOUS ENEMIES.

Predaceous enemies are of prime importance in the control of
plant-lice on walnuts and where the aphides occur in any numbers
may always be fomid preying on them from June to September.
Unfortunately they do not make their appearance on the walnuts
until their prey has had time to do much damage to young nuts and
to become abundant enough to cause collective injury to the tree.
Should these predaceous forms appear in early spring they would
quickly wipe out the few plant-lice present at that time and conse-
quently their progeny would starve to death. As injury is thus done
to the nuts and to the vitality of the tree before the advent of natural
enemies, artificial measures must be practiced in order to insure
healthy trees and perfect nut crops.

The predaceous enemies of walnut plant-lice include syrphus-fly
larvaj, agi'omyzid larvae, chrysopid and hemerobid larvae, coccinellid
beetles and their larvae, Camptohrochis hrevis Uhler (Heteroptera) and
its larva, and various spiders.

36 BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE.

Spiders.

The commonest spider predaceous on walnut plant lice is The-
ridium jplacens Keyserlmg. This spider may be found on the trees
during the months of August and September and has a habit
of eurling around itself the edge of the leaf under the protec-
tion of -which to deposit its egg sac. This species was determined
by Mr. Nathan Banks, of the Bureau of Entomology, who says of it
"* * * a species found on the Pacific coast. They do not
choose their food, but from location of web are apt to get many
plant lice." This and other spiders are of comparatively small
economic importance in the control of aphides.

CaMPTOBROCHIS BREVI8 UhLER.

Camptohrochis hrevis Uhler, which was determined by Mr. Otto
Heidemann, of the Bureau of Entomology, is a small black capsid,
measuring in the adult stage 4.2 by 1.9 mm. Its larva is white, with
conspicuous black markings. Both immature and mature individ-
uals were observed actively and abundantly attacking plant lice
during August, 1912. They do not occur hi numbers earlier m the
year and disappear in September. Thus their beneficial work is

Imiited.

Leucopis sp.

A fly of the family Agromyzidse, Leucopis sp., in its larval state
preys upon walnut plant lice from June to August. The small
yellow maggots superficially resemble syrphid larvae. They are
never very abundant and are not a great factor in the control of the
"lice." The life cycle in summer is completed m 24 days or less
and there are several broods in California.

Chrysopid or Lacewing Flies,

Of scarcely less importance economically than the ladybird beetles
and syrphid maggots are the active reddish-brown larvae of the "lace-
wings." Clirysopa majescula Banks and C. calif ornica Coq. are two
species of economic unportance m California. Table X shows the
predatory activities of two larvae of the latter species in the fall of
1912. The aphides consumed by these larvae were of all sizes and
averaged about 1.5 by 0.5 mm.

Table X. — Chrysopa califomica: Predatory activities on walnut plant lice, Walnut

Creek, Cal, 1912.

Larva
No.

Date of—

Number
"lice"

eaten to
molt 1.

Date of
molt 2.

Number
"lice"
eaten,

molt 1 to
molt 2.

Date of
spinning
cocoon.

Number
"lice"
eaten
from
molt 2
to pupa-
tion.

Total
"lice"
eaten.

Num-
ber
days
feed-
ing.

Hatch-
ing.

Molt 1.

1
2

Sept. 18
18

Sept. 22
21

11
22

Sept. 27
26

70
57

Oct. 8

7

265
300

346
379

20
19

WALNUT APHIDES IN CALIFORNIA.

37

Larva No. 1 ate on the average 17.3 "lice" per day, while larva

No. 2 consumed 19.9 "lice" per day. The lacewing larvae appear

in numbers toward the end of June and may be found until the end

of October. There are probably at least three broods, the last one

wintermg in the cocoon, which is white, short oval, with a central

brown annulation, and is spun among the leaves or under a piece of

bark. The closely allied but smaller hemerobiid larvae also attack

walnut plant lice,

Syrphid Larv^.

Next to the ladybird beetles the larvae of flies of the family
Syrphidae are of greatest importance in the natural control of walnut
aphides. The author has reared the following species of Syrphidae
from lai*vae collected while they were feeding on walnut aphides:
Catabomha pyrastri Linnaeus (1911-12) ; Sphserophoria melanosa Wil-
liston (Aug. 24, 1912); SpliseropTioria sttZ^^/mnpcs Thomson (Oct. 15,
1911); Allograpta ohliqua Say (Aug. 6, 1912) ; Eupeodes volucris Osten
Sacken (July, 1911). SyrpTius opinator Osten Sacken, and probably
other membere of this genus, prey on the aphides. Catabomha pyrastri
is the most abundant as well as the largest of these flies. Its aphido-
phagous capacity is almost double that of any of the other species
enumerated above. Table XI indicates the predatory activities of
two larvae of the last brood of this fly.

Table XI. — Catabomha pyrastri: Predatory activities on walnut -plant lice, Santa Jose,

Cat., 1912.

Date.

Number of

"lice" eaten

by-

Date.

Number of

"lice" eaten

by-

Date.

Number of

"lice" eaten

by-

Larva
No. 1.

Larva
No. 2.

Larva
No. 1.

Larva
No. 2.

Larva
No. 1.

Larva
No. 2.

Aug. 29

15
20
12
11
11
23
68

(')
4

15
15
17
17
18
36
46

Sept. 9

53
65
76
17
70
62
84
74
71

59

85
62
20
83
77
63

a3

105

Sept. 18

92
50
36
35

2 14

107

30

10

19..

104

31

11....

20

10

Sept. 2

12

21

2 13

3

13

22....

4

14

Total

5

15

959

1 035

6

16..

8

17

1 Hatched on this date.

2 Pupated on this date.

The ''lice" consumed were of a similar average size to those eaten
by the chrysopid larvae (Table X). The larva of Catabomha pyrastri
is pale green, with three longitudinal white stripes the whole length of
the body, and when fully extended exceeds half an inch in length.
The anterior segments of the body are retractile, giving it a slugiike
appearance. If food is plentiful the larva moves but little, although it
is capable of rapid crawling over the foliage if food is scarce. A para-
site, Bassus sp., preys upon it, often destroying as much as two-thirds

38

BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE.

of a brood and thus reducing its oconomic value. The maggot of the
fly pupates commonly among fallen leaves or rubbish at the base of
the tree, forming a light brown puparium (sometimes dark purplish-
brown, in which case the specimen is parasitized), with a paler
median longitudinal stripe. The adult fly is a large, shining black
form, with three interrupted, pale-yellow, arcuate cross-bands
(rarely wanting), and is 12 mm. long. Syrphid larv86 may be found
preying upon wahmt plant lice from May to November, although
they are quite scarce in the two extreme months.

Ladybird Beetles (Family Coccinellid^).

Ladybu'd beetles are the principal enemies of aphides affecting
walnuts. The author has observed the following species feeding on
these apliides: (1) OlTxi ahdominalis Say; (2) Adalia Tnelanopleura
Le Conte; (3) CocdneUa Juliana Mulsant; (4) Adalia Jiumeralis Say;
(5) IIii:>iJodamia convergens Gucrin; (6) HijJ'podamia amhigua Le
Conte; (7) Coccinella calif ornica Mannerheim; (S) Adalia hipunctata
Linnaeus; (9) Chilocorus orhus Casey. Nos. 1 to 8 m both adult
and larval stages feed on the plant lice on the leaves, while the adults
of the Chilocorus occasionally attack the winter eggs on the limbs.
Nos. 1 to 4 are the most pereistent enemies of the aphides, the others
only appearing spasmodically on the trees. The Hippodamia group
of lady bu'ds seems to prefer such intensely gi'egarious plant lice as
the plum louse (Hyalopterus arundinis Fabricius) or the bean aphis
(Aphis rumicis Linnaeus) and pay much less attention to the more
sporadic varieties such as the aphides on walnuts.

Table XII indicates the predatory activities of five larvae of OUa
ahdominalis (the ashy-gray ladybird.)

Table XII.-

-Olla ahdominalis: Predatory activilies on walnut plant lice, San Jose,
Cal., 1912.

Num-

Num-

Num-

Larva

Date of

Date of

ber of
"lice"

Date of

ber of
"lice"

Date of

ber of
"lice"

Date of

Total
"lice"
eaten.

Date of
adult

No.

hatching.

molt 1 .

eaten

molt 2.

eaten,

molt 3.

eaten,

pupation .

to molt

molts 1

molts

1.

and 2.

2 to 3.

1

Aug. 27

Aug. 30

29

Sept. 2

36

Sept. 5

91

Sept. 13

477

Sept. 22

2

31

Sept. 5

38

9

30

12

45

19

417

25

3

31

5

24

9

33

12

50

18

237

25

4

31

5

35

9

27

12

59

18

234

25

5

31

5

39

9

31

12

53

18

320

25

In all, 1,685 "hce" were eaten in 90 days, or 18.7 ''lice" per day
per larva. The ''Uce" were of similar average size to those consumed
by the lacewing larvae (Table X). It was noticed that before the
first molt the ladybu'd larvae would eat only very small aphides.

The following is a brief account of the stages of the ashy-gray lady-
bird {Olla ahdominalis) (PI. III). The egg: YeUow, later becoming

WALNUT APHIDES IN CALIFORNIA.

39

orange-colored; cylindrical, long oval, slightly tapering to either end,
four times as long as broad ; deposited in compact masses of from 5 to
25 on the leaf, usually on the underside, and with their long axis at
right angles to the leaf surface; size, 1.3 by 0.35 mm. The larva: All
black at hatching, later with pale markings, becoming more distinct
after each successive molt. After the third molt the general color
is dark purplish-black, with a median line of pale brick-red spots on
the thorax and abdomen and also two lateral rows of similar spots.
On segments 1 and 4 of the abdomen occur also two pale spots, one on
either side of the median brick-colored spot and midway between it
and the corresponding lateral spot. The fuU-grown larva has a
length of 8 millmieters. The pupa: General color white, wing pads
sienna brown. A large number of black spots and dashes are present
but the prevailing color is white. Average size, 4 by 3.3 mm. The
adult: Hemispherical, ashy-gray, with black markings, the elytra
sometimes difi'used mth dull reddish blotches; head black, with
central portion white or light gray; thorax (pronotum) black, with
gray margms; elytra ashy-gray, with eight black spots on each
elytron; legs yellow; abdomen reddish-yellow; average size, 5.2 by
4.2 mm. The adults of this species, if confined without food, will
devour one another.

Table XIII indicates the predatory activities of two larvae of
Adalia melanopleura on walnut plant lice.

Tablio XIII.^

-Adalia melanopleura: Predatory activities on walmit plant lice, Walnut
Creek, Cal., 1912.

Larva
No.

Date of
hatching.

Date of
molt 1.

Num-
ber

"lice"

eaten
to

molt 1.

Date of
molt 2.

Num-
ber
"lice"
eaten,
molts
lto2.

Date of
molt 3.

Num-
ber
"lice"
eaten,
molts
2 to 3.

Date of
pupa-
tion.

• Total
"lice"
eaten.

Date of
adult
emer-
gence.

1
2

Sept. 17
17

Sept. 20
19

41
35

Sept. 24
22

38
34

Sept. 26
25

30
33

Sept. 30
30

181
194

Oct. 12
12

In all, 375 plant lice were eaten in 26 days, or 14.4 per day per larva.
The feedmg period of both larvae was 13 days as contrasted with an
average of practically 18 days for the larvae of the ashy-gray lady-
bird. Adalia melanopleura is considerably smaller than that species,
its larva consuming in a period of 13 days half as many plant lice
as the larva of the larger species will devour in 18 days. This
larger species will consume 70 larvae in a single day while the maggot
of the large syrphid fly (Catahomha pyrastri) will dispose of over 100
and durino; the 23 days or so of its existence will devour over 1,000, or
about 43.5 lice per day. However, in contrasting the two groups of
predaceous insects — Syrphidae and Coccinellidae — it must be remem-
bered that the former are aphidophagous only m the larval state

40 BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE.

while both the adults and larvte of ladybirds feed on plant lice.
Ml-. E. K. Carnes/ experimenting in the State Insectary at Sacra-
mento, Cal., found that 20 adult beetles of Hijypodamia convergens
averaged 21.8 aphides per day and that the larvae of this species each
consumed from 250 to 300 plant lice during their larval existence.
He found that adult females would deposit eggs for from a month to
sLx weeks, laying on the average 15 eggs per day and fcedmg on the
plant lico all the tune. Essig - states that in the walnut orchards of
Ventura County, Cal., OUa ahdominalis, the ashy-gray ladybird, is by
far the most beneficial insect in the natural control of the European
wahmt apliis (CJiromajyMs juglandicola) .

ARTIFICIAL CONTROL OF WALNUT APHIDES.

The writer has been unable, save in one instance,^ to find any pub-
lished account of artificial control tried or adopted for walnut plant-
lice. Until the year 1910 no such work seems to have been performed
along this linC* In August of that year Mr. P. R. Jones, late of the
Bureau of Entomology, carried out a series of laboratory experiments
with a view to determining the efficiency of various washes against
these aphides. A small hand pump was fitted with an Eddy-chamber
nozzle and the applications made at a medium high pressure. Care
was taken that not enough pressure was exerted to kill any of the
"lice" by the force of the spray alone. Examinations were made 10
minutes after the applications. From these experiments the fol-
lowing results were obtained :

Commercial tobacco extract No. 2, containing 40 per cent nicotine, at strengths of
1-1,040 to 1-2,048, effective; dilutions weaker than 1-2,048, not effective.

Commercial tobacco extract No. 1 containing about 4 per cent of nicotine at strength
of 1-60, effective; dilutions weaker than 1-60, not effective (1-80 partially effective).

Commercial tobacco extract No. 1, at strengths varying from 1-60 to 1-200, com-
bined with a 3 per cent distillate-oil emulsion, effective.

Commercial tobacco extract No. 2 at strengths varying from 1-1,000 to 1-2,650 com-
bined with a 3 per cent distillate-oil emulsion, effective.

Commercial tobacco extract No. 1 at strengths varying from 1-60 to 1-200 combined
with a 2 per cent distillate-oil emulsion, effective.

Commercial tobacco extract No. 2 at strengths varying from 1-1,000 to 1-2,620 com-
bined with a 2 per cent distillate-oil emulsion, effective.

Distillate-oil emulsion at 2, 3, and 4 per cent strengths, effective.

Commercial lime-sulphur, 1-50, combined \vith commercial tobacco extract No. 1,
1-100, effective.

1 Sept., 1912. Cames, E. K. Insectary Division Reports for the months of June and Jul}', 1912. Mo.
Bui. Cal. State Hort. Com., v. 1, no. 10, p. S20-S2S;.

Some experiments with the common ladybird ( Hlppodamia convergens), p. S21-S26.

2 Apr., 1912. Essig, E.O. The walnut plant louse ( CAromapftis JMj/Zondi'eo/a [Kalt] Walker). Mo. Bui.
Cal. State Com. Hort., v. 1, no. 5, p. 190-194, figs. 72-7.3.

Control, p. 192.

3 Cf. Biennial Crop Pest and Hort. Report 1911-1912, Oregon Agr. Coll. Exp. Sta. Jan. 10, 1913, p. 165.
" Blackleaf 40" and kerosene emulsion 10 per cent recommended.

•• Since going to press control experiments undertaken in the spring of 1913 in Southern CaUfornia by
tlie University of California have been published in Circular 107 of the Agricultural Experiment Station
of the University of California.

|i

Bui. 100, U. S. Dept. of Agrlcultun

Plate III.

The Ashy-Gray Ladybird 'Olla abdominalis).

[A, adult; B, eggs; C, larva; D, pupa. (After Essig.)]

Bui 100, U. S. Dept of Agriculture.

Plate IV.

Fig. 1 .—Tree of the Royal Hybrid Walnut in Grove of Mr. F. Leib, San Jose, Cal.

Fig. 2.-GENERAL View of Walnut Grove of Mr. F. Leib, San Jose, Gal.

WALNUT APHIDES IN CALIFORNIA. 41

Commercial lime-sulphur, 1-50, combined with commercial tobacco extract No. 1,
1-200, effective.

Commercial lime sulphur, 1-70, combined with commercial tobacco extract No. 2,
1-1,000, effective.

Commercial lime-sulphur 1^5, combined with commercial tobacco extract No. 2,
1-2,000, effective.

It is noticeable that the weaker solutions of tobacco extracts were
not effective alone, but when combined with distillate-oil emulsion or
Ume-sulphur proved quite satisfactory. Possibly the most success-
ful result was obtained with distillate-oil emulsion of only 2 per cent.
Field experiments failed, however, to justify the use of this wash alone,
for it proved to lack the killing power found in the tcrbacco-extract
sprays. The emulsion serves, however, as a very good "spreader"
for the nicotine killing agent, since it serves to distribute the spray
over the leaf surface. Commercial tobacco extract No. 2 proved to
have greater insecticidal value than commercial tobacco extract No. 1,
judging by the corresponding strengths of the two sprays; and there-
fore in the field only the former was used. Foliage tests on an Eastern
black walnut tree were made of all the washes used in the laboratory
experiments, and in no case was any burning observed to result. This
type of wahiut seems more susceptible to burning injury than does
the European or so-called ' ' Persian ' ' walnut.

FIELD EXPERIMENTS.

SPRING AND SUMMER TREATMENT.

Experiment No. 1. — Lime-sulphur (commercial 1-50) combined with commercial
tobacco extract No. 2 (1-1,500). Orchard of Mr. I. Du Bois, San Jose, Cal. Two large
European walnut trees badly infested with aphides were sprayed July 1, 1911, under an
even pressure of 170 pounds. A count made on the following day showed that 95 per
cent of the aphides had been destroyed by the wash.

Experiment No. 2. — -Three per cent standard distillate-oil emulsion combined with
commercial tobacco extract No. 2 (1-2,000). A large, badly infested European walnut
tree in the yard of the experiment station at San Jose was treated, July 3, 1911, with
this spray at an even pressure of 170 pounds. A count made July 5 showed that over
95 per cent of the aphides had been killed.

Experiment No. 3. — Commercial tobacco extract No. 2 (1-1,500). Orchard of Mr.
F. Leib, near San Jose, Cal. (PI. IV, figs. 1, 2). A block of 10 walnut trees badly infested
was sprayed, May 21, 1912, under a pressure fluctuating from 60 to 140 pounds. A
count made two days later showed that not over 40 per cent of the "lice" were de-
stroyed .

Experiment No. 4- — Commercial tobacco extract No. 2 (1-1,500) combined with 2
per cent homemade distillate-oil emulsion. Orchard of Mr. F. Leib, near San Jose,
Cal. A block of 10 badly infested walnut trees was sprayed, May 21, 1912, under
pressure similar to that of experiment No. .3. A count made two days later showed
that 98 per cent of the insects had succumbed. Some oil burning appeared on the
foliage and nuts owing to insufficient agitation in the preparation of the emulsion
and consequent freeing of oil.

Experiments Nos. 3 and 4 were made to determine whether the tobacco extract
alone would prove effective in the field. Results indicate that a weak solution of
oil emulsion is necessary to act as a "spreader" for the tobacco.

42 BULLETIN 100, U. S. DEPARTMENT OF AGRICULTUEE.

Experiment No. 5. — Distillate-oil emulsion, 2 per cent. Orchard of Mr. F. Leib,
near San Jose, Cal. A block of six badly infested walnut trees was sprayed under
110 pounds pressure, July 31, 1912. A count made on August 6 showed that 74 per
cent of the "lice" had been destroyed.

Experiment No. 6. — Distillate-oil emulsion, 2 per cent, combined with commercial
tobacco extract No. 2 (1-2,000). Orchard of Mr. F. Leib, near San Jose, Cal. (PL
IV, figs. 1, 2). Six walnut trees, badly infested, were sprayed under a pressure of
110 pounds. A count, made August 6, showed that 85 per cent of the "lice" had
been killed by the spray.

Experiment No. 7. — Whale-oil soap, 1 pound; water, 5 gallons. Orchard of Mr.
E. I. Hutchinson, Concord, Cal. A block of 12 moderately infested European walnut
trees was sprayed under 150 pounds pressure. May 10, 1913. A count made two days
later showed that out of 473 "lice" counted, 263, or 55.6 per cent, had been destroyed.
A thorough drencliing had been applied and the trees were in full leaf. It was noticed
that the great majority of the "lice" that escaped were situated close to the base of
the midrib. In this position they were partly protected by the projecting rib, and
it is to be supposed that the wash lacked the pressure necessary to reach these
individuals.

All the foregoing experiments were undertaken on irees on which
the foliage was fully developed. It was noticeable that on thickly
foliated trees the percentage of plant lice killed was the smallest,
while on thinly foliated trees the greatest mortality resulted. Much
of the leaf surface on thickly foliated trees is almost inaccessible
to spray.

A comparison of the results of the foregoing tests favors distillate-
oil emulsion and tobacco. The most desirable combination for spring
and summer spraying is a 2 per cent distillate-oU emulsion, commer-
cial or homemade, combined with commercial tobacco extract No.
2, 1 to 1,500. High pressure (150 pounds or over) is desirable,
although not absolutely necessary unless the spraying be done before
the wahiut leaflets have flattened out in spring.

In timing the application for the aphides on the leaves it is desirable
to spray as early as possible in order to reduce the amount of leaf
surface to be covered by the wash and to destroy the plant lice before
they attack the nuts. On the other hand it wiU be found very hard
to destroy the plant lice before the leaflets flatten out, for the young
leaflets are pressed against one another in a manner that affords
very good protection to the insects from a spray. Moreover at this
period all the stem-mother plant lice will not have hatched from
the winter eggs. The time most preferable for the application is
just as soon as the growing leaflets shall have flattened out and before
they have attained their full size. At this time the ''lice" have aU
hatched and are all exposed on the undei-side of the leaves. Should
an oil spray be applied care should be taken that there is no free oil
in the emulsion, as the young nuts arc susceptible to burning. No
stronger than a 2 per cent distillate-oil emulsion should be used for
this early application. The spray should be directed to the underside
of the leaves, and angle nozzles used. A round nozzle is to be pre-

WALNUT APHIDES IN CALIFORNIA.

43

f erred to one of the Clipper type, as the former will diffuse the spray-
better over the leaf surface. Such a driving-spray nozzle as that
devised by the Massachusetts Agricultural College is desirable for
spraying trees of large size. If there are unsprayed walnut trees
in the vicinity it may be necessary to make a second application
some two or three weeks later, as plant lice are apt to have migrated
from these to the sprayed trees.

On account of the extended period over wliich the sexual forms are
produced, fall spraying for these forms, unless repeated again and
again, will be of Uttle value.

It should be borne in mind that the number of "hco" hatching in
the spring from the winter eggs varies considerably year by year in a
given locality or orchard and also that the hatching time of these
"Uce" is regulated by the sap flow in that particular tree upon which
the eggs happened to be placed. The hatching of the winter eggs
is not regulated by temperature conditions. Hence the stage m the
seasonal development of the aphidids corresponds to the stage in
development of that particular tree on which the stem-mother lice
were produced, leaving out of consideration the possibihty of mi-
grants arriving from other trees. This point is of importance when
it is considered that the different varieties of cultivated walnuts put
out their leaves and produce their nuts at different times and that
these functions are performed by individual varieties at different
times dependent on locahty and seasonal meteorological conditions.

Table XIV summarizes the control experiments made for spring
and summer treatment.

Table XIV. — Sur.imary of spring and summer spraying experiments against walnut
aphides, San Jose and Walnut Creek, Cal., 1911, 1912, and 1913.

Character of spray.

Date of appli-
cation.

Number

trees
sprayed.

Result of
spray; per

cent of
plant lice

kUled.

Cost per
diluted
gallon.

Commercial lime-siilphur, l-oO and commercial tobacco
extract No. 2 (1-1,500)

July 1,1911

July 3, 1911
May 21,1912

do

2

1
10

10
6

6
12

95

95
40

9S
7-1

85
55.6

$0,012

3 per cent distillate-oil emulsion (homemade) and com-
mercial tobacco extract No. 2 (1-2,000)

.0088

Commercial tobacco extract No. 2 (1-1,500)

.008

2 per cent distillate-oil emulsion (homemade) and com-
mercial tobacco extract No. 2 (1-1,500)

.0098

2 per cent distiUate-oil emulsion (commercial) .

July 31,1912
do

.0067

2 per cent distillate-oil emulsion (commercial) and com-
mercial tobacco extract No. 2 (1-2,000)

.0127

Whale-oil aoap (homemade), 1 pound to 5 gallons water. .

May 10,1913

.004

WINTER TREATMENT.

Experiment No . 1 . — Crude-oil emulsion, 12 per cent (crude oil, 27° Baume) . Orchard
of Mr. George Whitman, Concord, Cal. A block of 31 European walnut trees of moder-
ate size were sprayed February 25, 1913, under a pressure of from 150 to 175 pounds.
Three gallons of spray were applied to each tree and "Friend" nozzles used. The trees
were well drenched. Examination made April 5, 1913, showed that trees were start-
ing to leaf. Most of the leaves were as yet tightly closed, but the basal leaves of many

44 BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE.

shoots were opened. A general survey of the sprayed block and of a check unsprayed
block indicated equal infestation by young stem mothers. Plant lice were not all
hatched. An examination made April 15, 1913, showed that trees were well out in
leaf. All stem mothers had hatched. A general survey of sprayed and unsprayed
trees showed no apparent difference in infestation. A count of 28 leaf clusters selected
at random from the sprayed trees yielded 21 stem mothers, while a similar count of
the same number of leaf clusters from unsprayed trees yielded 29 stem mothers. It
may be inferred from this experiment that the crude-oil emulsion destroyed few, if
any, of the winter eggs.

Experiment No. 2. — Commercial lime-sulphur, 1-10. (Concentrated solution, 33°
Baum^.) Orchard of Mr. George Whitman, Concord, Cal. A block of four large trees
of the European walnut were sprayed March 5, 1913, imder a pressure of 100 pounds.
About 14 gallons of spray were applied to each tree and " Friend" angle nozzles used.
Eggs were abundant on both sprayed and check trees. The leaf buds on these trees
began to open April 1, 1913. Examination was made April 15, 1913. Trees were then
well out in leaf. The stem mothers were all hatched. The lime had no effect in
retarding leafing. A count of 20 leaf clusters taken at random on the sprayed block
yielded no plant lice, while a similar count of the same number of leaves on the check
trees yielded 27 stem mothers. Further examination showed that on the sprayed
trees no plant lice could be found, while on the check trees nearly every leaf cluster
had one or more of the insects.

A subsidiary experiment was undertaken on two young California black walnut
trees, both infested with eggs. One of these trees was treated with commercial lime-
sulphur, 1-9 (concentrated solution 33° Baume), and the other left as a check. On
the sprayed tree no eggs hatched and when examined on April 17, 1913, the eggs were
shrunken and distorted, the embryos having been destroyed within the eggshell.
The eggs on the check tree hatched normally about the end of March.

Experiment No. S. — Crude-oil emulsion, lime-sulphur, and "Yel-
ros." Vrooman orchard, Santa Rosa, Cal. Four plats were
sprayed, April 9-11, 1913, with a power outfit at high pressure, as
follows: Plat 1, 40 trees, crude oil (22° Baum6) emulsion, 8 per cent;
plat 2, 40 trees, hme-sulphur, 1 to 8; plat 3, ''Yel-ros," 1 to 25,
16 trees; plat 4, ''Yel-ros," 1 to 40, 24 trees. These apphcations
were made on late Franquette walnuts, dormant at the time of spray-
ing. The orchard was well infested with the winter eggs of the plant
Uce. An examination, May 27, 1913, showed that the trees were well
out in leaf. Stem mother plant lice were mostly about two-thirds
grown. Counts of SO leaves (about 480 leaflets) taken at random
from each of the four plats and from a check unsprayed plat resulted
as follows:

Table XV. — Winter spraying experiment No. 3 against walnvt aphides, Vrooman
orchard, Santa Rosa, Cal. , 1913.

Number of
Plat. "lice" on

80 leaves.

Per cent
of number
on check.

Crude-oil emulsion, 8 per cent .

Lime-sulphur, 1 to 8

"Yel-ros," 1 to 25

"Yel-ros," 1 to 40

Check— unsprayed

10.6
1.9
13.4
93.2
100.0

WALNUT APHIDES IN CALIFORNIA.

45

The best results, therefore, were obtained by the lime-sulphur
wash. The greater efficiency of the 8 per cent crude-oil emulsion
over the 12 per cent crude oil used in experiment No. 1 is probably
due to the heavier grade of oil (22° Baume) used in the 8 per cent
experiment. The heavier oil remains longer on the trees and coats
the eggs of the aphides more satisfactorily than the oil of lighter
grade. As may be seen from Table XVI both the 8 per cent crude-
oil emulsion and '' Yel-ros," 1 to 25, gave good results, but " Yel-ros,"
1 to 40, was quite ineffective. Table XVI is a summary of experiments
against the winter eggs:

Table XVI. — Summary of experiments on the winter eggs, Walnut Creek and Santa

Rosa, Cal., 1913.

Character of spray.

Date of ap-
plication.

Number
of trees
sprayed.

Date of ex-
amination.

Plant

lice
present
(check—

100).

Cost per
diluted
gallon.

Crude-oil (27° Baura^) emulsion, 12 per cent.

Commercial lime-sulphur, 1 to 10

Crude-oil (22° Baum6) emulsion, 8 per cent. .

Commercial lime-sulphur, 1 to 8

" Yel-ros, '' I to 25

"Yel-ros," 1 to 40

Feb. 25...

Mar. 5

Apr. 9-11.

do...

do...

do...

Apr. 5, 15.
....do...
May 27...

do...

....do...
....do...

Per cent.
72.4
.0
10.6
1.9
13.4
93.2

$0.01
.02
.0073
.025
.028
.0175

It is in a measure unfortunate that the homemade 1-2-1 lime-
sulphur spray was not tried. This is considerably cheaper than the
commercial article, but there is no reason to suppose that the winter
formula of the homemade lime-sulphur would not prove quite effective
judging by the results obtained with commercial lime-sulphur.

In recommending winter sprays for the plant lice infesting walnut
trees the writer must accord the preference to lime-sulphur, 1-8 to
1-11, while good work may be expected from crude-oil emulsion, 8 to
12 per cent, using the heavier grades of oil (not lighter than 24°
Baume), and from "Yel-ros," 1-25. The oil emulsion (homemade) is
the cheapest winter spray, although there is little difference between its
cost and that of the homemade hme-sulphur wash, winter formula.

In applying the spray for the aphis eggs the wash should be directed
so as to cover completely every part of the twigs and limbs. Late
spraying, i. e., making the appHcation just before the buds are begin-
ning to swell, is preferable to spraying earUer, especially if crude-oil
emulsion is used, as the oil does its best work soon after it is applied
and the plant hce at hatching time are more easily destroyed by it.

In concluding the section on artificial control the author would like
to express his thanks to Mr. Frank Leib, San Jose, Cal., and Messrs.
George Whitman and E. I. Hutchinson, Concord, Cal., for their help and
cooperation in the carrying out of field experiments on their orchards,
and also to Balfour, Guthrie & Co., San Francisco, Cal., by whose
courtesy the Santa Rosa experiments were made possible, they having
made the spray applications under the author's supervision.

46 BULLETIN 100, U. S. DEPARTMENT OF AGRICULTUEE.

SUMMARY.

The life history of walnut aphides in California is briefly as follows:
A week or so before the buds open on the trees in the spring the
aphidids begin to hatch from the winter eggs. As soon as the young
foliage appears the "lice" settle on it, and after feeding for a month
or so become adults. Tliese stem mothers are always Avinged and like
plant lice of later generations are capable of migrating to other trees
and orchards. As soon as they arc fully developed they produce
young parthenogenetically. These second-generation young become
mature in three weeks and in turn produce young. The individuals
of the third and subsequent generations of summer mature in about
16 days. On early-leafing varieties there are 10 or 11 viviparous
generations in the year while on late varieties there are 8 or 9. The
production of the sexual generation is prolonged over four months,
these forms first appearing in July. After the sexes (comprised of
the winged male and the wingless female) mate, the female repairs to
the twigs antl limbs of the tree, there to deposit her eggs. Winter is
passed in the egg stage only.

In general the aphidids inhabit the underside of the leaves, but those
of the second, third, and fourth generations often attack the nuts,
sometimes seriously dwarfing them (see PI. I, fig. 1). Occasionally
the ''lice" will be found on the upper surface of the leaf. Wlien infes-
tation on the leaves and nuts is severe the vitality of the infested tree
is impaired. The aphidids excrete a sweet, gummy, transparent sub-
stance much sought after by ants, and in this thrives a black sooty
fungus. This black fungus often covers the upper sides of the lower
leaves and the upper part of the nuts, thereby interfering with the
respiratory action of the plant tissues.

Walnut plant lice have many natural foes, all predatory. These
serve to keep the aphidids in" check but do not appear in sufficient
numbers until after the "lice" have had time to injure tlie nuts. The
most persistent of them is the ashy-gray ladybird beetle (Olla abdoin-
inalis Say).

Aphidids on walnuts can be controlled artificially with sprays. The
winter spraying directed against the eggs is the easier to apply, and high
trees can be reached by a winter wash with ease, whereas in the spring
and summer so thick is the foliage that a thorough application is hard
to accomplish satisfactorily. Furtliermore, far less material is
required when the trees are bare. Lime-sulphur and crude-oil emul-
sions are effective, especially the first named. The spray should be
directed all over limbs and twigs so as to cover every part. If it
is necessary to spray in spring or summer, a combination of 2 per cent
distillate-oil emulsion and commercial tobacco extract No. 2 (1 to
1,500) wiR prove effective provided it be applied under a pressure of
at least 150 pounds and the spray directed on the nuts and underside
of the leaves.

WALNUT APHIDES IN CALIFORNIA. 47

BIBLIOGRAPHY.

Chromaphis juglandicola Kaltenbach.

1843. Kaltenbach, J. H. Monographie der Familien der Pflanzenlause . . . Aachen,
1843.

"Lachnusjttglandicola." Original description, v.-ilh colored figures.

1857. Koch, C. L. Die Pflanzenlause Aphiden, Niirnberg, 1854-1857.

" Callipterus juglandicola Koch," p. 224, fig. 297, 1857. Description and colored figures.
1860. Passerini, Carlo. Gli Afidi, Parma, 1860.

" CaUiptcTUs juglandicola Kalt." recorded.

1870. Walker, Francis. Notes on aphides. Zoologist, ser. 2, v. 5, pp. 1996-2001,
Feb., 1870.

" Callipterus juglandis," p. 2000; Callaphis proposed, p. 2000. " Chromaphis peglandicola,"
p. 2001. Genus Chromaphis erected.

1881. Buckton, G. W. Monograph of the British Aphides, v. 3, London, 1881.
" PterocalHs juglandicola Kalt.," p. 32-34. Description and colored plate.

1906. Schoutcden, H. Catalogue des Aphides de Belgique. Mem. Soc. Ent. Belg.,
V. 12, pp. 189-246.

" Callipterus juglandicola Kalt.," p. 209-210. Recorded.

1909. Essig, E. 0. Apliididse of southern California, II. Pomona Col. Jour. Ent.,

V. 1, no. 2, pp. 47-52, June, 1909.
" Callipterus juglandicola Koch," p. 51-52. Description and figures.

1910. Gillette, C. P. Plant-louse notes, family Aphididae (continued). Jour. Econ.

Ent., V. 3, no. 4, pp. 367-371, pi. 24.

" Chromaphis juglandicola," p. 367, fig. 4. Note of occurrence and figure of antenna of
winged female.

1910. Wilson, H. F. A key to the genera and notes on the synonymy of the tribe
CalUpterini, family Aphididae. Canad. Ent., v. 42, no. 8, pp. 253-259,
Aug., 1910.

" Chromaphis juglandicola Kalt.," pp. 257-258. Refers to Walker's erection of the genus
Chromaphis.

1912. Essig, E. O. The walnut plant louse {Chromaphis juglandicola (Kalt.) Walker).

Mo. Bui. Cal. State Com. Hort., v. 1, no. 5, pp. 190-194, figs. 72-73, April,
1912.

Description and figures, natural control notes.

1913. Wilson, H. F., and Lovett, A. L. Miscellaneous insect pests of orchard and

garden. Bien. Crop Pest and Hort. Rpt. 1911-12, Oregon Agr. Col. Expt.
Sta., pp. 147-165.

" Chromaphis juglandicola Kalt.," p. 165. Note of occurrence and remedies.

MONELLIA CARY^ Mouell.

1879. Monell, J. Notes on the Aphididae of the United States, Part II. Notes on
Apliididae, with descriptions of new species. IT. S. Geol. and Geog. Sur-
vey Bui. 5, no. 1, pp. 18-32, Jan. 22, 1879.
"Callipterus caryse, n. sp.," p. 31. Original description.

1879. Thomas, Cyrus. Eighth Report of the State Entomologist on the Noxious and
Beneficial Insects of the State of Illinois, Springfield, 1879.
" Callipterus caryx, n. sp.," p. 199. Ncrte of occurrence.

48 BULLETIN 100, U. S. DEPARTMENT OF AGRICULTURE.

1910. Williams, T. A. The Apliididae of Nebraska. Nebr. Univ. Studies, v. 10
no. 2, pp. 85-175, April, 1910.

" Callipterus caryx Monell," p. 115. Description and note of ocwirrence.

1910. Gillette, C. P. Plant-louse notes, family Apliididee (continued), pi. 24. Jour.
Econ. Ent., v. 3, no. 4, pp. 367-371, Aug., 1910.
" Monellia caryx," p. 367. Note of oocurrence and figure.

1910. Davis, J. J. A list of the Apliididse of Illinois, with notes on some of the
species. Jour. Econ. Ent., v. 3, no. 5, p. 407-420, Oct., 1910.
" CalUplerus caryx Monl.," p. 417. Note of occurrence.

Monellia caryella Fitch.

1855. Fitch, Asa. First Report on the Noxious, Beneficial, and other Insects of

the State of New York, Albany, 1855.

"Aphis caryella Fitch," pp. 163-165. Original description.

1856. Fitch, Asa. Third Report on the Noxious and other Insects of the State of

New York, Albany, 1856.

"Hickory gay-louse, Callipterus caryellus Fitch," pp. 448-449. Short description.

1862. Walsh, B. D. On the genera of Aphididse found in the United States. Proc.
Ent. Soc. Phila., v. 1, pp. 294-311.

" Callipterus caryellus Fitch," p. 302. Reference.

1879. Thomas, Cyrus. Eighth Report of the State Entomologist on the Noxious
and Beneficial Insects of the State of Illinois, Springfield, 1879.

" Callipterus caryellus Fitch," pp. 170-171. Note of occurrence.

1887. Oestlund, O. W. Synopsis of the Aphididae of Minnesota. Geol. and Nat.
Hist. Survey Minn. Bui. 4.

"Monellia caryella Fitch," p. 45. Genus Monellia erected. Note of occurrence.

1910. Davis, J. J. A list of the Aphididae of Illinois, with notes on some of the spe-
cies. Jour. Econ. Ent., v. 3, no. 5, pp. 407-420.
"Monellia caryella Fitch," p. 419.

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BULLETIN OF THE

u

No. 104:

Contribution from the Bureau of Plant Industry, Wm. A. Taylor, Chief
July 10, 1914.

THRIPS AS POLLINATORS OF BEET FLOWERS.

By Harry B. Shaw,
Assistant Pathologist, Office of Cotton and Truck Diseases and Sugar-Pkmt Investigations.

INTRODUCTION. 1

While conducting breeding experiments with sugar beets during a
period of more than five years, it could never be observed that the
beet flower, despite the pungent fragrance of its nectar and the
remarkable abundance of its pollen, attracted nearly as many insect
visitors as numerous blooms offering less pronounced attractions.
Especially significant was the rarity of the visits of the honeybee
and other common species of Hymenoptera. It appeared as though
nature had vainly provided powerful insect lures, excepting only
those of conspicuous size and color. It is true that insects, some of
them capable of transferring pollen from flower to flower, do visit
beet flowers, but relatively their numbers are small and their visits
few.

Thes.e breeding experiments necessitated the isolation and hand
pollination of numerous beet flowers. Not infrequently, in spite of
careful teclmic, it was found that single flowers which had been
emasculated and protected by paper bags from pollination became
fertilized and produced seed in a manner at the time inexplicable.
Although the actual percentage of such cases was small, it was
sufficient to attract attention and to cast doubt upon the thorough-
ness of the protection afforded by the bags. Not only is the beet
flower protandrous, but numerous attempts of the waiter to effect
close fertilization by preserving the pollen until the stigma of the
same flower should become receptive, then applying the pollen, have
failed. The above-mentioned fertilization, therefore, could not have
been accomplished by pollen from any one of the single flowers
operated on, even had such pollen reached the stigma; in other
words, the beet flower can not be self-fertilized. . The most probable
explanation for the fertilization of these isolated flowers was tlio

Note.— The investigations and experiments reported In this bulletin are of interest to horticulturists and
plant breeders.

42131°— 14

2 BULLETIN 104, U. S. DEPARTMENT OF AGRICULTUEE.

unobserved access of minute pollen-bearing insects. None of the
common visiting insects other than thrips is minute enough to
gain entrance through the interstices between the mouth of the
paper bag and the stem .when the bag is tied closely about the beet
spike. Thrips, however, are so tiny as scarcely to be visible to the
naked eye, the mature larvae being about ^ inch long and only
about -^ inch long immediately after hatching; hence it seemed
probable that some of these insects might have crawled up "udthin
the mouth of the tied bags and dropped on the stigmata of the
isolated flowers some of the pollen they were carrying.

OCCURRENCE OF THRIPS ON BEET FLOWERS.

Besides several other species not identified, the Bureau of Ento-
mology determmed the following among specimens of thrips col-

FiG. 1. — The bean thrips (Heliothrips fasciatus): a, Adult female; 6, ventral side of abdominal segment of
same; c, antenna of same, a, Greatly enlarged; 6, c, more enlarged. (After Russell.)

lected from beet flowers at Garland, Utah, in 1909 and 1910: Ilelio-
thrips fasciatus L. (fig. 1), Frankliniella fusca Hinds, and Frank-
liniella tritici Fitch. The species most abundant during the seasons
of 1911 and 1912 at Ogden, Utah, was Thrips tahaci, the onion thrips.
The few observed at Jerome, Idaho, during the summer of 1913 have
not yet been determined.

At Garland the seed beets were grown near fields of alfalfa, whence
many of the thrips found on beets doubtless migrated, the same species

Bui. 104, U. S. Dept. of Agriculture.

Plate

Thrips tabaci Dislodged from the Beet Flowers Shown in Plate II.
Natural Size. (Original.)

Bui. 104, U. S. Dept. of Agriculture.

Plate II.

^f

,^

#

BRANCHED SPIKE OF BEET FLOWERS FROM WHICH THE THRIPS SHOWN IN

Plate I Were Dislodged. Natural Size. (Original.)

THKIPS AS POLLINATORS OF BEET FLOWERS. 3

being exceedingly abundant in alfalfa blossoms. In Ogden the experi-
mental plats were located in the heart of a trucking district, where
many onions and other general truck crops are grown. At Jerome
the beet plats were surrounded by alfalfa fields. At Garland these
insects were fairly abundant. At Ogden in 1911 they were very
abundant. This may be better appreciated by a glance at Plate I,
which shows the thrips that were dislodged from the small branched
spike depicted in Plate II after the spike of flowers had been exposed
for a short time to the fumes of chloroform.
Before the thrips had recovered from anes-
thesia the spike and its branches were
distinctly outlined by the stupefied insects.
Notes taken at the time read as follows:

August 7, 1912. — After treatment with chloroform, 85
thrips fell from a spike possessing 80 open flowers; from
another branched spike 190 thrips were dislodged.

Inspection of beet flowers sometimes re-
vealed as many as five or six thrips in a
single perianth.

In 1912, on the site of an old Chinese truck
garden at Odgen, thrips became extraordi-
narily numerous during the late blooming ?'«• 2.-side view of the head of

^ -^ ^ '^ _ fc" a thrips, showmg the mouth

period, when they fairly swarmed in and parts. Much enlarged. (After
about the beet flowers. It was then as- Mouiton.)
certained that in addition to drinking the nectar and devouring the
pollen they may also injure the floral organs.

Earlier studies of the injurious effects of various suckmg insects,
including aphides, red spiders, and thrips, on sugar beets, had estab-
lished the fact that the last-named insects sustain their unenviable
character on sugar beets also; they cause on young sugar beets a
great diversity of leaf curls and distortions. On the spikes and bract-
lets of seed beets smaU silvery scars may be found as a result of their
attacks. The thrips is more destructive than most sucking insects,
because, not satisfied with merely puncturing, it tears and grubs up
the surface tissues of its food plants with its powerful mouth cones, or
proboscis (fig. 2), in order to release a more copious flow of the plant
juices.^ It reminds one of the actions of a hog.

These studies were extended to the observation of tlu-ips on the
inflorescence of sugar beets. The spikes and spikelets of the sugar
beet, with their closely arranged spirals of flower clusters, are very
numerous and aft'ord excellent hiding places for these insects. It
was found that as the period of most abundant bloom approached,
thrips became increasingly numerous, partly through migration from

' Moulton, Dudley. The pear thrips and its control. United States Department of Agriculture, Bureau
Of Entomology, BuU.'tin 80, pt. 4, p. 54, 1912.

BULLETIN 104, U. S. DEPARTMENT OF AGRICULTURE.

other plants, but more especially through breedmg. Eggs are]
deposited and hatched on the spikes themselves. On hatching, the
young larvffi quickly seek the flowers, doubtless attracted by the
pungent fragrance of the nectar, and literally wallow in the nectar
and pollen, avidly di-inkuig the one and voraciously devouring the
other.

()})servations covermg five seasons have shown that several species
of Thysanoptera visit beet flowers and that the number of individuals
varies greatly with the locality and general environments, notably
mth the crops in the vicinity. At Jerome, Idaho, in 1913, on land only
recently cleared from sagebrush, thrips were rather scarce, although

somewhat abundant in alfalfa in near-by
fields. These insects have also been seen in
moderate abundance on seed beets in Indiana
and Michigan.

THRIPS AS POLLEN BEARERS.

The v^riter has been able to discover in the
literature very little reference to thrips as a
pollen bearer and no proof of its ability to
bring about the fertilization of flowers.

Darwin was familiar with the visits of thrips
and kept in rnind the possibility that they
might gain entrance through his nets.

Hermann MiiUer ^ records their occurrence
in the flowers of several genera and species,
but does not mention beets. In a paragraph
on Thysanoptera he says that ''probaldy few
flowers, if any, are altogether exem]^t from
their visits, and though they have seldom been
detected in the conveyance of pollen, yet from
their great abundance, their value as fertilizers
must not be overlooked. It is almost im-
possible to exclude these tiny insects by means of nets. The Thysan-
optera seek both poUen and honey. They seize a single pollen grain
in their mandibles and convey it to the mouth."

Uzel,2 in Bohemia, has noted the visits of several species of Thy-
sanoptera among sugar and stock beets, but adduces no evidence in
proof of the actual pollmation of those flowers by tlu-ips.

On August 3, 1911, at the experimental plats in Ogden, Utah,
spikes of beet flowers were exposed to the fumes of chloroform to

1 Miiller, Hermann. The fertilisation of flowers. Tr. and ed. bj' D'Arcy W. Thompson, London, 1883,
p. 44-45.

2 Uzel, Heinrich. tJber die Insekten, welche die Bliiten der Zucker- und Futterriibe besuchen. Zeit-
schriftfiir Zuckerindustrie in Bohmen, Jahrg. 37, p. 182-197, 1913.

Fig. 3.— Larva of Thrips tabaci
(second stage) taken from a
sugar-beet flower. The insect
carries numerous beet-pollen
grains on its body. X 50.
(Sketch of the larva after Rus-
sell.)

THRIPS AS POLLINATORS OF BEET FLOWEES. 5

dislodge insects that might be harboring in them. As already stated,
thrips in unsuspected number were thus removed. (Pis. I and II.)
A microscopic examination of many of these — larvse and adults —
showed that without exception beet pollen grains were present on
their bodies (fig. 3).

The original notes under this date are as follows:

August 3, 1911. — Discovered that Thrips sp. [later determined as Thrips tabaci] are
exceedingly numerous on and among beet flowers. Some spikes were collected, and
absorbent cotton sprinkled with chloroform was held over them to stupefy any insects
that might be present. Thrips fell off and were microscopically examined. Without
exception, each bore among its body hairs numerous sugar-beet pollen grains. Some
open flowers were then examined, and thrips, as they recovered from their stupor, were
observed to enter the perianth, where they moved about quite actively, traveling over
every part. Many pollen grains were picked up by the Insects' body hairs, others
were dropped ; pollen was also transferred from one insect to another when they came
in contact one with another.

Almost at the close of the blooming period of beets, counts were
made of the pollen grains borne by a number of thrips dislodged with
chloroform from beet spikes, as shown in Table I.

Table I. — Beet pollen grains on thrips, near the close cf the blooming period.

Stage of development of the insect.

Number of grains found on
surface indicated.

Dorsal.

^^nar'" Total.

30

G2
53

10 40

Adult

7S 140

Do

S2 135

These poUen grains were distributed over every part of their bodies,
even along the antennae. Nor do these figures represent unusual
individuals. The blooming period was practically over at this time;
poUen was therefore not very abundant. Both larval and adult
thrips have since been seen to be literally covered with beet pollen.

EXPERIMENTS IN THE POLLINATION OF BEET FLOWERS.

The foregoing results were both interesting and surprising, and at
once suggested, among others, the following queries :

(1) Do the thrips in this instance redeem themselves from their hitherto wholly
evil reputation by playing an essential, or even an important, role in the fertilization
of beet flowers? Or, do they simply convey pollen from one flower to another on
the same plant and thus effect close pollination only? ^

1 Other experiments have shown close pollination of beet flowers to be almost absolutely ineffective in
bringing about fertilization, which is undesirable even when successful. Self-fertilization is not possible.
The term "self-fertilization" is here used to mean that resulting from the pollen of the same flower; "close
pollination," or "close fertilization," that effected by the application of pollen from one flower to another
on the same plant; "cross-pollination," that between any two plants.

6

BULLETIN 1(U, U. S. DEPARTMENT OF AGRICULTURE.

(2) Inasmuch as the}- consume large quantities of pollen, do they thus work injury
to beets?

(3) Do they injure the lloral organs of beet flowers?

To bo cfTective agents in the fertilization of beet flowers, they must
tlo more than convey pollen from one flower to another on the same
spike, stem, or plant; they must bring about true cross-pollination.

^Vlthough already late in the season when the foregoing observa-
tions were made, experiments were at once planned to ascertain
whether pollination and fertilization might be effected through the
agency of thrips. To this end several vigorous seed beets, still in

bloom, were selected. On August 7
and 8, 1911, the largest buds on a
number of spikes were emasculated,
the smaller and more immature buds
being trimmed off. This work was
done at the stage when the sepals
were just about to separate at the
tips and disclose a tiny yellow spot
of the anthers, and it w^as performed]
under a pollinating tent in order to|
exclude flying insects and wind-
carried pollen (fig. 4 ) . As each set of|
buds was emasculated it was at onc(
covered with a white manila papel
bag, 4 by 6 inches in size. A tuft o|
absorbent cotton was first wrappec
carefully about the spike some
inches below the buds. The bag was
then drawn over the spike until th(
emasculated buds were situated in-j
side the bag near the top, while the
mouth of the bag reached well belo>
the buds and came in contact witl
the wrapping of cotton. The mouth of the bag w^as then folded diagon-l
ally in such a manner as to pinch the cotton-wrapped stem in one
corner; then it was. folded a second time to make tight contactj
Metal clips were finally set along the edge of the double fold to secure
it (fig. 5). The stems bearing these spikes were tied to stakes t(
prevent too much movement and to keep them in an upright posi-
tion. Before covering the spikes a close search was made for thrips
or other small insects, any such being removed. The stigmata oi
these flowers became receptive three days later. Thrips were thei
collected from other beet flowers into small vials. As each lot was
collected it was immediately transferred to one of the bagged spikes]

Fig. 4.— roUmaliiii; tent of white sheeting,
which may be completely closed and secured
with hooks and eyes or buttons. (Original.)

Bui. 104, U. S. Dept of Agriculture.

Plate 111.

FiQ. 1.— Flowers of Sugar Beets to Which Thrips Had Access. Natural Size.

(Original.)

Fig. 2.— Spikes of Sugar-Beet Flowers on Check Plants, Which Remained
Sterile. Natural Size. (Original.)

THRIPS AS POLLINATOES OF BEET FLOWEES.

To accomplisli this a slit was made iii one side of the bag at least 2
inches below the buds of the inclosed spike, so that no pollen or thrips
might fall upon the flowers when the vial was inverted over the slit,
and the pollen-bearing thrips were jarred downward into the bag.
This being done, the slit was closed with adhesive plaster, leaving
tlie inclosed thrips free to seek the nectar and distribute the pollen
they carried. About 25
thrips w^ere put in each bag.
Three forms of control or
checks were employed at
this time:

(1) Spikes of emasculated buds
were isolated, as above described,
and left undisturbed.

(2) Similarspikes were isolated,
and when the inclosed flowers had
become receptive, slits were nqade
in the bag and at once closed
without introducing thrips.

(3) Spikes of buds were pre-
pared as for emasculation and iso-
lated without that operation being
performed. These also were then
left undisturbed.

One month later, all the
bags were opened to exam-
ine the inclosed flowers.
The time had been too brief
for the maturation of seed,
but it was ample for fertil-
ization and for the develop-
ment of seed to the milky
stage. The results were as
follows :

Every flower on the checks remained sterile, the sepals of some remaining green.
In other cases the entire flower had withered (PI. Ill, fig. 2). Among those to which
thrips had been introduced, one set of flowers was lost; of a second set, 16. G6 per cent
of the flowers became fertilized and produced seed; a third showed 20 j^er cent of
fertilization; and a fourth, 28.6 per cent. For the entire set, the percentage of effec-
tive pollination by thrips was 20.37 (PI. Ill, fig. 1).

On August 26, 1911, eight spikes of wild-beet flowers were similarly
treated. Three of these were used as checks, Thrips were placed
with the others in the manner above described. Some of these spikes
were afterwards broken off, but of those remaining none of the checks
became fertilized; of those to which thrips had been admitted only
one remained, and 20.5 per cent of its flowers had been fertilized and
produced seed.

Fig. 5.— Spikes of beet flowers isolated by means of paper
bags, showing the method of admitting pollen-bearing
thrips through an opening. (Original.)

8 BULLETIN 104, U. S. DEPARTMENT OF AGRICULTUEE.

Tlie flowers of a beet spike open successively; therefore, few at any
one time attain the same stage of development. This fact not only
limits the number of available buds on each spike, but also may
reduce the percentage of effective hand poUination as much as 50 per
cent. The above results may therefore be considered not only posi-
tive, but surprising. Tlie complete notes of the results of this experi-
ment are shown in Table II.

Table II. — Pollination of beet f outers — experiment of Augutst 26, 1911.

l)escription.

Flowers.

Seeds.

Spike.

On
spike.

Sterile.

Num-
ber.

Per
cent.

Remarks.

No la.

Check

22

14
36
22

10

22

14

22
10

0

0
0
0
0

0

0
0
0
0

Not emasculated; spike dry and
brown.
Do.

No. 2a

do

No. 2b

do

Emasculated.

No. 2c

do

Do.

No. 3a

..do

Emasculated; stems and flowers

Total

Thrips admitted...
Missing....

green.

104

104

0

0

No. 3b

No. 3c

7

6

2

28.6

No. 4-^

No. 4b

Thrips admitted...
do

12
35

10
28

2
7

16.66
20.00

Total

Wild beets.
Check

54

43

11

20.37

For the entire set.

No. 1

No. 2

do

No. 4

do

All.

0

0

Broken off.

No. 3

Thrips admitted...

Do.

No. 5

do

Do.

No. 6

do

Do.

No. 7

do

Do.

No. 8

do

24

19

5

20.83

During the following season two similar experiments were carried
out. The first experiment was made on June 26, 1912, when the
plants were flowering abundantly. On this date two spikes were
prcj^ared as already described, except that the adchtional precaution
was taken to spray thoroughly all ])arts of the flowers and spikes
with water from an atomizer to remove any thrips that might be
hidden there. Three days later thrips were collected and transferred
to the bags. A month later complete notes were made, %\ith the
results shown in Table III.

On July 12, 1912, the second experiment was started in the same
manner with three spikes, and a month later the data shown in Table
III were secured.

These experiments demonstrate that thrips transferred from one
flowering beet to another may carry sufficient poUen on their bodies
to effect fertihzation.

THRIPS AS POLLINATORS OF BEET FLOWERS. 9

Table III. — Pollination of beet flowers — experiments of June 26 and July 12, 1912.

Experiment of June 26. 1912.

Experiment of July 12, 1912.

Description.

Flow-
ers.

Seeds.

Spike.

Description, i

Flow-
ers.

Seeds.

Spike.

1
p.

a
o

1

s

3

'A

a
Q

.a
6
D
'A

o

PL,

No.l
No. 2

Thrips admitted

do.

18
14

6
4

12
10

60.66
71.14

No.l
No. 2
No. 3

Thrips admitted

do

13
20
20

8
17
20

5
3
0

38.46
15

Totals

Check

0

32

10

22

68.75

1 Of the 33 flowers to which thrips were admitted in this experiment, 24.24 per cent are sho%vn to have
been fertilized, while all the checks remained sterile.

2 For entire set.

CROSS-POLLINATION BY THRIPS.

As already stated, other studies have shown that close poUination
of beets rarely results in fertilization and that self-fertilization does
not take place. To be of service to beets, thrips must therefore
bring about cross-pollination. The writer has found the impression
rather general that thrips do not travel from plant to plant to any
great extent. On this point the following evidence from the writer's
notes is available:

July 19, 1912. — A great number of thrips had been shaken from seed beets in full
bloom into a large pan. In the slanting rays of the evening sun many of the adults,
which are winged, could be seen to fly from the collecting pan and alight on adjacent
plants. Their flight was sustained and fairly steady, though not nearly so rajsid as
that of gnats.

July 21, 1912. — Since attention was attracted to the flight of thrips, careful watch-
ing, when their wings glitter in the evening sunshine, revealed the fact that their
flight from plant to plant is voluntary and frequent; this flight is well sustained,
though very slow. They were seen to travel not only from one plant to the next,
4 feet away, but to more distant ones. The flight of many of these thrips was inter-
cepted by a sheet of white paj^er, upon which they alighted. Some of them were
chloroformed and examined. Pollen at this time was not very abundant, because
the plants were long past the time of maximum bloom. Counts were made showing
that 5 different thrips carried grains of pollen, as follows: No. 1, 5 grains; No. 2, 44
grains; No. 3, 3 grains; No. 4, 38 grains; No. 5, 4 grains.

July 23, 1912. — An examination of the seed beets in plat 2, where seed is almost
ripe, showed an absence of thrips. The number of these insects on the plants now in
bloom in plat 1 is immense. [Plat 1 lies about 50 feet north of plat 2. Many beets
in plat 1 were planted later than those in plat 2 and were therefore still in bloom.]
Thrips were fairly numerous in plat 2 when the plants there were in bloom; therefore
it would appear that thrips migrate some distance in pursuit of pollen and nectar.
An examination of plants in plat 1, some of which had been planted earlier than
others, showed the earlier planted ones, now without bloom, to be devoid of thrips.

This study established the fact that not only are thrips capable of
collecting and carrying pollen on their bodies and of effecting cross-

10 BULLETIN 104, U. S. DEPARTMENT OF AGRICULTURE.

pollination and subsequent fertilization when transferred from one
flowering beet to another, but that they voluntarily travel from plant
to plant and carry pollen throughout a sustained flight.

From this evidence there can remain no doubt that these insects
are capable of playing an important r61e in the pollination of beet
flowers. May it not be a very significant one? It is known that in
certain parts of Europe and the United States beets have sometimes,
perhaps frequently, failed to produce seed, although an abundance
of bloom appeared. It seemed possible that the presence or absence
of thrips in great number might in part be responsible for this phe-
nomenon. Subsequent observations, however, afford evidence in dis-
proof of this theory. It is safe to say that thrips undoubtedly assist
in the pollination of beet flowers, perhaps to a greater extent than
any other species of insect. It can scarcely be doubted that they
perform a hke service for many other plants.

INJURY TO SEED BEETS.

Thrips feed avidly upon the nectar and pollen of beets, but beet
pollen is so abundant that unless thrips be present in enormous num-
bers they apparently do no damage to the floral organs, preferring as
food the nectar and pollen. However, should they become extraor-
dinarily numerous, as was the case at Ogden in 1912 during the
latter part of the season, it would seem that the nectar and pollen
are not sufficiently abundant to supply their truly voracious appe-
tites. They then attack the more delicate and succulent parts of the
flowers. Sometimes the styles are cut through at the base, but
more frequently the papiUse, with which the lobes of the stigma are
thickly studded, are torn to pieces. Furthermore, they may devour
so much pollen as to interfere with both wind and insect pollination
by too greatly diminishing the supply. Thrips move actively from
flow^er to flower of the same spike, from spike to spike and stem to
stem of the same plant, and in this way bring about much more close
pollination than cross-pollination, and in fact effect all the close polli-
nation and fertilization of which the plant is susceptible. This in
itself is undesnable and even harmful. Close fertilization has been
shown to cause degeneration among beets, even in the sense of pol-
lination and fertilization between different individuals of the same

progenv.

TROUBLE TO PLANT BREEDERS.

The writer has experimentally show^n that the larvae of thrips in
all stages readily pass through the meshes of fuie silk chift'on and
much more readily through the net, cloth, and sheeting frequently
used by horticulturists and plant breeders to isolate flowers designed
to be hand-polUnated. He has also been able to demonstrate that

I

THRIPS AS POLLINATORS OF BEET FLOWERS. 11

they actually do effect pollination and fertilization after passing
through such covers.

The following is an instance of what might be expected to occur
through the agency of thrips: The horticulturist of a well-known
firm of seedsmen in the United States noted that his asters became
fertilized although covered with cloth bags. The writer suggested
that thrips might be responsible for this. The horticulturist replied
in part that "the aster flowers were merely covered with coarse-
meshed cloth to see if they were self-fertile. Insects as small as
thrips would not have been excluded. We merely learned that the
fertilization of asters is not dependent on the insects — mostly
beetles — that one ordinarily sees on the flowers."

The horticulturist and plant breeder may not disregard these
insects. They introduce an element of uncertainty to be guarded
against with the utmost care and circumspection. Their minute size,
inconspicuous color, great numbers, and the fact that they are almost
ubiquitous make them a factor to be reckoned with by every worker
along these hues and necessitate the development of special precau-
tions and technic.

Covers of net, cloth, and sheeting afford no real protection against
them; even paper bags must be applied with great care. The writer
found the method described and illustrated in connection with these
experiments to be simple and efficacious.

It is as necessary to rid the isolated portion of plant and flower of
thrips already present as to prevent the access of others after isola-
tion. In these experiments the practice was made of carefully scru-
tmizing each spike of buds or flowers before covering it and brushing
off any thrips that might be present with a camel's-hair or sable
brush, sometimes also spraying the spike thoroughly with water. In
the summer of 1912 the use of nicotine sulphate also was tried, as
shown in the following notes :

July 24, 1912. — At this late blooming period, tlirips have become exceedingly
numerous on all spikes in bloom; they interfere seriously with pollination work.
To ascertain whether a simple, practical method might be availal^le to rid the individ-
ual spikes completely of these pests, the following experiment was carried out: Some
spikes, badly infested with thrips, were selected. Before operating on the spikes,
they were immersed in the following solution: AVater, 2 pints; nicofume (nicotine
sulphate), 1 tablespoonful.

Spikes 1, 2, and 3 (in their normal condition, i. e., bearing flowers of all stages —
buds, flowers just opening, and flowers already fertilized) were immersed in the above
solution 10 seconds; then they were at once isolated with manila paper bags in the
manner previously described.

Spike 4, with selected buds emasculated, was treated with nicofume like the pre-
ceding, bagged, and (when stigmata had become receptive) pollinated.

Spikes 5 and 6 were treated like No. 4, but not pollinated.

Spike 7 was merely shaken and flowers blown upon to dislodge thrips; flowers
emasculated.

12 BULLETIN 10-i, U. S. DEPARTMENT OF AGRICULTURE.

August 19, 1912. — All spikes examined.

Nos. 1, 2, and 3 in good condition; no signs of thrips or other insects; no injury
from nicofurae; good seed formed.

No. 4. No inJTiry from nicofume apparent; no evidence of thrips or other insects;
emasculated July 24, li>12; pollinaled July 27, 1912; of 10 flowers pollinated 8 pro-
duced seed.

No. 5. General condition similar to No. 4; emasculated July 24, 1!)12; not i)olli-
nated; 13 flowers emasculated; all remained sterile.

No. 6. Similar to No. 5; all flowers remained sterile.

No. 7. Check; spike dead.

This experiment shows that the treatment with nicotine solution
did not perceptibly injure beet flowers and that it at the same time
removed thrips from them.

CONCLUSION.

From these experiments it is seen that these minute insects, the
numerous species of Thysanoptera, some of which more or less injuri-
ously infest practically all our plants, are also active agents in pol-
lination. Among beet flowers they are frequently very numerous
indeed, effecting both close pollination and cross-polhnation upon
them. However, after taking into account the various forms of
injury they do, it is doubtful whether the balance remains in their
favor in regard even to beets. Under ordinary conditions, in fields
of commercial seed beets, it is believed that on the whole their work
is beneficial; but should they become excessively numerous, they
sustain their reputation as one of our really destructive pests. To
the horticulturist and plant breeder they are pests of the worst type,
necessitating constant watchfuhiess and a refined technic in all
pollination work.

The suggestion is ventured that certain supposed mutations may
really have been the result of unsuspected cross-pollination by means
of one or another species of thrips, whether in cereals supposedly
not susceptible to cross-polHnation without the intervention of man
or in flowers which were thought to have been isolated against
cross-2)ollination.

o

4

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1914

s u

OJ

1 nt:ie:

\

BULLETIN OF THE

No. Ill

Contribution from the Bureau of Entomology, L. O. Howard, Chief
July II, 1914.

(PROFESSIONAL PAPER.)

THE SEQUOIA PITCH MOTH, A MENACE TO PINE
IN WESTERN MONTANA.

By Josef Brunner,
Agent and Expert, Forest Insect Investigations.

INTRODUCTION.

In the area near and at the divide between Swan River and Clear-
water River in Montana and extencUng, so far as known at present,
about 8 miles southeast from that divide, the sequoia pitch moth
(Vespamima sequoia Hy. Edw.)^ is at present the most destructive
insect. It menaces the lodgepole pine timber, in which it propagates,
and all other trees in the vicinity of those attacked are jeopardized
by the forest fires fed by the dead timber resulting from the work
of its larvae. The range of its peculiar injury to trees in that region
has also been traced by the writer about 6 miles west from the wagon
road which unites the Clearwater and the Swan River country from
Rainy Lake toward the Mission Range. Roughly, the area in which
the insect is a very serious factor in forest destruction is about 12
miles long by as many miles wide and covers about 144 sections of
forest land, or more than 90,000 acres.

Control and practical elimination of this insect, as a serious menace
to the very existence of the forest growth of this area, depends largely
on a knowledge of its habits and life history. Insufficient familiarity
with these two points would result in unnecessary waste of time in
locating infested trees and in conducting control operations at a time
of the year when the result would be out of proportion to the cost.

DESCRIPTION OF THE INSECT.

Vespamima sequoia (fig. 1) is a clear- winged moth in general appear-
ance strongly resembUng a hornet or "yellow jacket." Tins resem-
blance is so perfect that a truck gardener near Missoula, Mont., evi-

1 Identiflcation by August Busck, as the species which was first found to iiiliabit the sequoia.
Note. — This bulletin is a report on an insect infesting lodgepole pine in the Rocky Mountain region of
Montana.

44394°— 14

2 BULLETIN 111, U. S. DEPARTMENT OF AGRICULTURE.

dently familiar \vith the hornet, refused to believe that a specimen
which had just emerged and ^na as being observed on the tree in which
it had attained maturity was not a "stinger" until the difference was
pointed out to him.

The female is about two-thirds of an inch in length and the male is
somewhat smaller. In the female the last three segments, and in the
male the last four, arc bordered with rich lemon-yellow, which makes
the sexes easily distinguishable, even to the uninitiated.

The mature larva is from three-fourths inch (male) to 1^ inches
(female) long and is of a dirty white or yellowish color.

Fig. 1. — Female pitch moth ( Vcspamima sequoia) 15 minutes after
emerging. (Original.)

LIFE HISTORY.

Observations on this species in different localities, together with
the dates of emergence of adults reared in the laboratory, show that
the general flight of the mature insects and oviposition occur between
June 25 and July 15, the greater number of them probably flpng
about July 10. However, variation in latitude and altitude and un-
usual weather conditions prevailing during the spring of certain years
may put the date of this general emergence a few days ahead or

THE SEQUOIA PITCH MOTH. 3

behind those given hero. The flight and oviposition of the insect are
over by August 1 .

It appears tliat the adult insect is rather short-Uved, as all the
specimens that were reared and observed in captivity cUed within four
days of emergence. Out of 20 females thus under observation only
one oviposited, the rest dying without issue. This would show that
the female dies, unless she is fertihzed, within three days after
emergence.

As this species is very active it is reasonable to suppose that it
deposits but few eggs in any one place. In fact, it was frequently
observed that wherever two larvae are too close together one of them
invariably dies. Wherever an occasional pitch mass is found to
contain as many as three larvae, each one of them occupies an inde-
pendent tube. This shows that the scattering of the eggs is neces-
sary in order to enable most larvae to sur\'ive the evidently fierce
struggle for existence. Exactly how long it takes the eggs to hatch
is unknown to the writer, but the injury to the newly infested trees
by the young larvae is quite perceptible by August 15. By the time
frost arrests their activity, about October 1, the larvae, especially
the females, have attained considerable size. The following summer
is de\oted by the larva to lengthening the tunnel and growing, and
toward the second winter it drives a rather roomy tunnel into the
pitch exudation wliich, during the following June, it lines vnih. silky
thread preparatory to pupation.

During the two months preceding pupation all the larvae of the
same sex are of practically the same size, so that the two generations
are almost inseparable. However, one famihar with tliis and alhed
species can separate them by the difference in color and density of
skin, which is rather white in the younger generation and yellowish,
leathery, in the older one.

Tlie length of the pupal stage is 30 days, i. e., the insect remains
in the chrysalis for 30 days from the day it transforms into that
stage until it emerges as adult. Tlie chrysalis is free in the tunnel,
moving back and forth in it at will by means of spines on the body,
and is usually found on warm days quite near the surface and far
back when it is cold. When ready to emerge the pupa forces about
half its length out through the thin shell of pitch at the mouth of the
tunnel and the adult insect (fig. 1) emerges by bursting the shell of
the chrysalis. This occurs two years after the egg was laid. In
other words, the larvae hatching from the eggs deposited in June and
July of one year develop into adults during the same months two
years later, thus making the generation biennial.

There seems to be indication of an alternation of seasons of abun-
dance and scarcity of the insect. During late autumn, 1913, the
young larvae were quite scarce in the vicinity of Rainy Lake, espe-
cially east of the wagon road from Clearwater to Swan River, wliile

4 BULLETIN 111^ U. S. DEPARTMENT OF AGRICULTURE.

1-year-old larvae were abundant. If this observation holds good,
the insect being biennial, we should be able to forecast the years
when it will be abundant and when scarce. Hence there should be
great flights during 1914, 1916, 1918, etc., unless the insect is con-
trolled, and small flights during 1915, 1917, 1919, etc.

RELATION TO THE MOUNTAIN PINE BEETLE.

Tlie only insect which is of any consequence in its relation to the
pitch moth in the Clearwater country is Dendrodonus monticolae
Hopk. This beetle frequently attacks trees infested by the larvae
of the moth. Tliis attack is always fatal to the hitter, because
Dendroctonus kills the tree almost immediately, and without the flow
of sap the larvae of the moth can not survive. On October 1 every
larva of the moth wliich was found in trees attacked by the beetle
after August 1 was dead. Some of the trees had the appearance of
having been infested by the beetle only two or three weeks; never-
theless, the moth larvae were dead, although they were in perfectly
fresh condition otherwise.

Vespamima sequoia is apparently little subject to attack by either
parasitic or predaceous enemies. In fact, it is less troubled by insect
enemies or diseases than any other species known to the writer; and
as birds also never seem to pursue it, there is no present evidence
that natural agencies might check it in the course of time.

HABITAT.

Tlie insect prefers sunny openings within the forest and slopes
where the soil is rather sandy and quick to dry. Ridges along
watercourses are also favorite places for it. It avoids the damp and
densely shaded bottom lands along streams. It prefers pine, open
stands of lodgepole pine, as, for example, within and alongside the
big old burn which extends from the wagon road toward and along
the Flathead Range, where there are few trees 3 or more inches in
diameter that have escaped attack and are not infested now.

HOST TREES, AND CHARACTER OF INJURY.

Lodgepole pine is numerically the principal species of tree in the
region and, with the rare exception of the yellow pine, is the species
subject to attack by the pitch moth, although the moth attacks
almost all kinds of conifers in other localities within its range.

The trees infested by tliis insect (see fig. 2) are readily located by
the never- absent pitch exudation over the tunnel of the larva. This
may be readily seen at quite a distance, if the stand of trees is not
too young. Even on very small trees of but 1 or 2 inches in diameter
the pitch tube is of the size of a walnut the first season of the infesta-
tion and more than twice that the second year.

The pitch exudation on the tree shown in figure 3 weighed over
10 pounds, and such trees are so numerous that many tons of pitch

THE SEQUOIA PITCH MOTH. 5

could be collected within the comparatively small area infested by
this insect.

The trees are all of them attacked at the extreme base, and the
exuding pitch flows out from the tree not infrequently a distance of
10 or 12 inches upon the humus which covers the ground.

THE WORK OF THE LARVA.

The larva begins its mine in a crevice in the bark, where the egg
was deposited, proceeding tlirough the outer layers until it reaches
the cambium. Close to the wood it begins to construct a transverse

Fig. 2.— Lodgepole pine trees infested by the sequoia pitch moth. Trees of all sizes are infested in the

Clearwater country of Montana.

mine running in both directions from where it entered. It widens
this tunnel at the center, thereby causing the appearance of a cen-
tral chamber. In small trees the mine is always practically straight
across the grain of the wood.

It is a puzzle to the waiter how the larva determines how far it
can go in the two directions without entirely girdling the tree, thus
killing it and thereby depriving itself of sustenance. It is a note-
worthy fact that of the great many trees less than 3 inches in diameter
examined, all were found girdled to within 1 or 2 inches, and none
entirely girdled.

6 BULLETIN 111, U. S. DEPARTMENT OF AGRICULTURE.

It is evident tluit the entire girdling of about 0.5 per cent of the
older infested trees is accomplished by more than one larva which
happen to infest these trees at one and the same time. Each larva
evidently tries to get as far away from its neighbor as it can, and
thus the tree is girdled. But, as indicated, plural infestation is rare.
To test this point experimentally the WTiter has several times planted
in captivity two larvte on one piece of wood, and invariably one of
them left the sustaining slab. On a few occasions when, because

Fig. 3. — A lodgepole pine tree infested by the sec|uoia pitch moth. The new , flowerlike exudation
indicates present infestation. (Original. )

none vacated, the writer supposed he had made a success of ''double
planting," he found later that one of the larvae was dead.

Tunnels in trees infested only the second year, as well as those in
trees that have been infested by several successive generations of the
insect, look as if they had been engraved by the larvae eating the
wood, but such is not the case. The appearance is caused by the
larvae preventing the wood from forming a new layer across the
tunnel. Thus the tunnel, in the course of many seasons, gradually
becomes deeply embedded in the w^ood tissues.

In rare cases the tunnel is slightly slanting, running on one side of
the center, a few inches below the surface of the ground, while the end

I

THE SEQUOIA PITCH MOTH. 7

of the other side is several inches above ground. Under no circum-
stances is the tunnel parallel to the grain of the wood.

As stated, the activity of the larvae within the cambium of the tree
causes a heavy flow of pitch toward the exterior, and fresh, flowerlike
nodules upon older exudations (fig. 3) are a definite proof that the tree
is still infested.

EFFECT OF THE INFESTATION ON TREE GROWTH AND THE FOREST.

It is obvious that with one-half and, in the majority of cases, two-
thirds of the circumference of the tree trunk cut off from the root

Fig. 4. — Stump of a pine tree G4 years old which grew to ho 9J inches in diameter breast high at 41 years
of age and added only seven-eighths inch to this diameter during the last 23 years of its life, owing to
attack by the Sequoia pitch moth. (Original.)

system by the dividing tunnel, the growth of the afflicted tree has to
suffer. Count of annual rings and measurements on a tree which was
considered to be a fair example of the general injury in the area
brought out the fact that during the first 41 years of its life and nor-
mal health it had added annually about one-fourth inch to its diam-
eter, wliile it added only about one thirty-second of an inch, or the
thickness of an ordinary visiting card, annually during the 23 years
it had been infested by the pitch moth. (See fig. 4.)

8 BULLETIN 111, U. S. DEPARTMENT OF AGEICULTURE.

SECONDARY INJURY BY FIRE.

About one-half of 1 per ct nt of the trees infested by Vespamima
sequoia is killed. In case of a slight surface fire in places where, out-
side of humus, no litter covers the ground, all the infested trees which
are not killed outright come through it wdth the bark on the sides
where the pitch exudation is located literally cooked, and for the
balance of their existence they display the "fire wounds" (fig. 5), of
which the pitch moth was the primary cause. They remain green
but add little to their size annually. Subsequent fires fell them

Fig. 5.— Fire wounds on jjine tree injured ])y the Sequoia pitch moth. (Original.)

readil}", and their burning injures and kills perfectly healthy trees,
wliich would otherwise have remained unscathed.

There is abundant proof in the area under discussion that unat-
tacked trees, on ground not littered with fallen timber, pass through
surface fires with but slight injury. Thousands of such trees are
mingled ^^^th as many which display "fire wounds" and the tunnel of
Vespamima burned indelibly into the base of the latter, thus explain-
ing why it is that some trees are half burned while others, under the
same conditions and at the same place, have escaped with scarcely a
scar.

THE SEQUOIA PITCH MOTH. 9

Many trees with fire wounds are reinfested on the sound side and
killed, thus adding to the material which makes a surface fire in the
area really serious. The heat generated by them in burning, either
standing or prostrate, injures and kills healthy trees in the immediate
vicinity.

During decades fallen timber, primarily caused by insects, accumu-
lates and provides such an amount of inflammable material among
the uninjured green trees that finally a fire sweeps such areas clean of
all tree growth and enters and destroys adjoining areas which contain
healthy trees only.

In the infested zone in the vicinity of Rainy Lake the forest looks
much like a checkerboard. There is an area of 50 acres here with a
stand of 10-year-old trees on them; adjoining this is a square-cut
piece of 200 acres with 40-year-old trees as a cover; next to this are
80 acres on which reforestation started only a few years ago, and so
on. This thing has been going on for at least 100 years, so far as can
be traced, and probably existed before time was counted. Everyone
of these variously aged tree patches is the result of a separate fire.
The explanation of the occurrence of so many of them within an area
comparatively so small is found in the peculiar meteorological condi-
tions prevailing hero.

TOPOGRAPHY OF THE AREA.

Kunning from the southeast toward the northwest are the rocky
walls of the Flathead Range; west and parallel to it lies the Mission
Range ; and on the divide between Swan River and Clearwater River,
extending from the Mission Range toward the wagon road which
passes over the lowest elevation, and running from west to east is a
high ridge. This ridge forms an effective barrier to storm clouds
driven up Swan River between the walls of the Flathead and Mission
Ranges. Their only outlet is between that ridge and the Flathead
Range over the Rainy Lake territory.

The clouds driven up Swan River, inconsequent though they might
be under different conditions, strike the ridge dividmg the two water
courses and are promptly thrown back upon their own mass by the
resistance of the ridge. On the west are the walls of the Mission
Range, so there is no escape for them in that direction; thus they
drift eastward and toward the outlet over Rainy Lake. Part of them
escape there. But the greater part are thrown upon the wails of the
Flathead Range, from which they tumble back upon the oncoming
mass in a turmoil before this also by and by finds its way to the only
avenue of escape. The great numbers of lightning-struck trees in
this area abundantly testify to the great role played hero by lightning.

10 BULLETIN 111, U. S. DEPARTMENT OF AGRICULTURE.

Remembering that in the comparatively small zone about Rainy-
Lake infest(>d by the pitch moth there are tons of thousands of trees
with heavy pitch exudation at their base which, once ignited, will
burn for several days, ram or shine, and that during the violent
thunder storms there many trees are struck l)y lightning and the
pitch set on fire, we will have the combination which explains the
frequency of fires in that area.

Let us illustrate. Lightning strikes a tree infested by Vespamima
and sets it afire. During the storm the gromid is soaked sufficiently
to prevent the fire from spreading. The pitch, however, owing to its
thickness and inflammability, continues to burn. On the following
day a clear sky allows the sun to dry the ground cover around the
burnmg pitch sufficiently so that a surface fire is startc^d which wUl
be ended by the next shower. If the stand consists of medium or
small sized trees and the area has passed through fires before, every-
thing is killed, and the place, w^hen it has been reforested, wdll stand
out clear in the checkerboard of forest and elemental battles even
after half a century or more, as is the actual case in this territory.

As storms are evidently quite frequent there, the patches burned
are usually small, ranging from 50 to 200 acres. However, there are
also some burns which an accumulation of debris had undoubtedly so
augmented that whole sections were swept. All the traceable evi-
dence in the biggest burn in the area points to insect work as the
primary cause, just as in the smaller burns where the evidence is
more definite and is easier of location.

With a knowledge of these facts, one can not but conclude tliat the
pecufiar results of the work of Vespamima sequoia are the chief and
primary contributing cause of the frequency, we might almost say
continuity, of fire damage to forest growth in tliis area. To eliminate
or ameliorate this condition, it is manifestly necessary to ehminate
the insect or at least reduce it to such an extent that it loses its
m.enacing aspect.

REMEDY.

Since nature and its agencies are powerless in the control of this
insect, the scourge has to be combatted by man through direct action
if it is not to continue its injurious activity in the future as it has in
the past. There is only one way to reduce the insect, and that is to
destroy it while it is in the larval stage.

As is apparent from the portion of this bulletin relating to the life
history of the moth, larvae can be found in the infested trees at any
time of the year.

However, in order to destroy the greatest number of them with the
same amount of effort, operations should be conducted during the
months of September to June, inclusive, when there is no snow on the

THE SEQUOIA PITCH MOTH. 11

ground to cover the pitch exudations. During most seasons the snow
eliminates November, December, and January as control months.

By September 1 all of the eggs which have not been lost have
hatched, and the young larvae have attained a size sufficient so that
they can be seen and destroyed, and up to June 25 hardly any of the
second-year larvae have reached the adult stage.

The statements under ''Habitat" suggest where to look for infested
trees. To locate the larvae, separate the pitch exudation from the
trees, thereby exposing the larvae. Kilhng the larvae outright, or
taking them up for later counting and destruction, or, in other words,
hand picking, is really the only thing that can be done to reduce the
numbers of the insect.

RECOMMENDATIONS.

If the control work is done without utilization of the pitch, it will
be at direct cost ; and the taking up of the larvae, though slower than
destruction on finding, is preferable, as it enables a proper checking
up of the extent of damage and of the amount of control work ac-
compHshed. But if the pitch is of sufficient commercial value to pay
the cost of its collecting and shipment, it would be possible to control
the insect by utilizing its products.^ If the pitch is marketed, it is
not necessary to keep a close check on the work beyond keeping tab
on the weight of the pitch shipped and the returns from the sales.

Note. — The statements in this paper, with the exception of those under "Descrip-
tion of insect," "Life history," "Relation to the mountain pine beetle," and, to a
certain extent, "Remedy," refer to Vespamima sequoia in the Clearwater country of
Montana alone and are not applicable in other regions where the destructiveness of
the insect is known to assume a different character.

> Just before going to press analyses of these resins were received from the U. S. Bureau of Chemistry,
with the following comment. — A. D. Hopkins, in Charge of Forest Insect Investigations.

"The volatOe oils obtained from these two resins are slightly heavier than ordinary oil of turpentine.
They show smaller percentages, distilling below 170° C. However, as turpentines as heavy as these will
find a market as pamt and varnish thinners, it is anticipated that no dlfflculty would be encountered in
disposing of the tm-pentine produced from this material. Especially is this opinion held since * * * jt
is more than likely that owing to the size of the sample and the manner of packing, as well as the exposure
of the crude gum, the percentage of volatile oil is lower than it would be in material which was collected in
the ordinary commercial way.

"The rosins do not appear to diSer essentially from the rosin made from longleaf pine, and we have no
hesitation in expressing an opinion that it would be entirely suitable for soap-making purposes and would
command the ordinary market price according to the grade. Attention may be called to the fact that
lighter colored rosins, therefore higher grade rosins, would undoubtedly be made in practice, provided
bark, dii't, etc., are kept out of the resin.

"Nothing was observed in this examination which would warrant the opinion that the nature of the
product was due to the particular manner of its production. It is believed that essentially the same product
would be obtained by the ordinary commercial chipping of the tree except so far as prolonged exposure on
the trimk of the trees, as probably took place with these samples, favors volatilization of the light oils
and this aflectstherelativeproportionsofvolatileoils and ofrosin and the specific gravity of theoils." — F. P.
Veitch, Chief of Leather and Paper Laboratory , Bureau of Chemistry.

o

WASHINGTON' : GOVERXME.VT PRIXTIXG OFFICE : 1914

ADDITIONAL COPIES

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BULLETIN OF THE

No. 112^

Contribution from the Bureau of Entomology, L. O, Howard, Chief
August 21, 1914.

THE OAT APHIS.^

By J. J. Davis.
Entomological Assistant, Cereal and Forage Inseet Investigations.

INTRODUCTION.

Of the three important plant-lice attacking wheat and oats above
ground, the oat aphis {Aphis avencB Fab.)^ is probably the most
widely distributed and most common over its area of distribution,
and is second in importance as a wheat pest, first rank being held by
the so-called "green bug" {Toxoptera graminum Eond.), a species
well known in the Southwest because of its periodic depredations.
Like the "green bug," the insect under discussion is an imported
species, and was probably
introduced into the United
States during the first half
of the last century, at least
previous to 1851, the date
of what appears to be the
first published record of its
occurrence in this country.^

The oat aphis has never
been considered a pest of
great importance, although
observations would lead to
the belief that it is worthy of more consideration and study. It does
not ordinarily appear suddenly in great swarms as does the " green

1 This bulletin describes an insect found on the small grains, more especially oats. The
bulletin is of interest to growers of cereals.

= This common name, used by some of the early writers, is adopted here, since the name
European grain-aphis, used by some authors, is scarcely distinctive, all three of the com-
mon grain aphides probably being native to Europe.

3 Specimens labeled "Aphis avcnw Fabr. — A. padi Kalt. on Triticum vulgare, Russia
merid.," received from Dr. N. A. Cholodko\ sky, of St. Petersburg, agree well with the
Aphis avenw of this country.

This species has the following synonyms : 8iphocoryne avenw Fabricius, Siphonophora
avenw of some authors, Aphis mali of some authors, Aphis annuw Oestlund (included
as a synonym on the authority of Mr. Theodore Pergande, U. S. Dept. Agr., Div. Ent.,
Bui. 44, p. 9, 1904), and Aphis fltchii Sanderson.

* Fitch, Asa. Fourth Ann. Rpt. Regents Univ. N. Y., 1851, p. 65 ; reprinted in Lint-
ner, J. A., Ninth Rpt. ... on the insects of N. Y., 1893, p. 405.
45614°— 14

Fig. 1.

-Distribution of the oat aphis
United States. (Original.)

in the

BULLETIN 112^ U. S. DEPARTMENT OF AGEICULTURE.

bug," although occasionally it may be found in conspicuous and alarm-]
ing numbers, but it is ever present on wheat ; and, especially in the fall.!
when it occurs at the base of the plant and on the roots, it is easily]
overlooked by the casual observer. However, there is no doubt that
these plant-lice, even though they may not be conspicuous anc
apparent, Aveaken the plants and decrease the yield. This de-
crease in yield is presumably general, but may not as a rule be'
locally conspicuous as in the case of the "green bug," that is, not

enough to be recognizable. On the
whole, however, it can hardly be doubt-
ed that these little insects are respon-
sible for the loss in this country of thou-
sands of bushels of wheat annually.

DISTRIBUTION.

The oat aphis is almost cosmopoli-
tan in its distribution, and irl this
respect rivals such well-known plant-
lice as Macrosiphum pisi Kalt., M.
(/i'anariu?7i, and Toxoptera graminum.
It has been found in all parts of
Europe, as well as in most of the
States of the United States. Quite
likely it will also be found to occur
in Asia, and probably, in Africa,
although we believe it has never
been reported in literature from
these countries up to the present
time.

The map (fig. 1), compiled from rec-
ords made by assistants in the Cereal
and Forage-Crop Insect Investigations and from authentic pub-
lished records, indicates the present known distribution in the United
States. It will be observed that the species has not been found in the
Gulf region.

DESCRIPTIVE.

Fig. 2. — The oat aphis (Aphis
avenw) : Wingless viviparous
female, much enlarged. a.
Antenna of same, still more en-
larged. (Original.)

On grain two forms of the oat aphis are found — the winged and
wingless viviparous females. As will be explained later, it occurs
on the apple where there are to be found, in addition, the sexual
forms, namely, the wingless oviparous female, the winged male, and
eggs. (See fig. 5.)

The wingless vivij)arons female (fig. 2) is yellowish green to
olive green, often somewhat mottled. The stem mothers on apple

THE OAT APHIS. 3

in the spring are more often lighter, with a darker green median
longitudinal area, while those found on wheat in the fall of the
year are darker, sometimes becoming greenish brown. The bases
of the cornicles are surrounded, in the spring forms, with areas
yellowish to orange in color, while these areas are larger and are
usually orange to dark reddish in the fall and in hibernating indi-
viduals. The antennae are about one-half the length of the body,
and the cornicles, or " honey tubes," are slightly vasiform.

The winged viviparous female (fig. 3) has a black head and
thorax, the abdomen being olive green, sometimes paler, with a row
of more or less conspicuous black sjiots on each side anterior to the
cornicles, and usually with a rusty or brownish red area about the
base of each cornicle. The antennse are black and reach a little
beyond the middle of the body. The cornicles are black and slightly

Fig. 3. — The oat aphis : Winged viviparous female, greatly enlarged, a. Antenna of same,
still more enlarged. (Original.)

vasiform. The last branch of the median vein in the wings branches
near the apex of the wing.

The immature aphides are paler green, but almost invariably the
yellowish to pinkish areas about the bases of the cornicles are quite
noticeable, although sometimes faint in very young individuals.

The winged mjole is similar to the winged viviparous female except
that it is smaller and has a narrower abdomen, and the color is
usually more of a dusky green.

The wingless oviparous f empale is somewhat like the viviparous
female, but the abdomen is more tapering toward the tip, and the
color is pale yellowish green to greenish dusky, or even has an
orange tint. Rather conspicuous orange or reddish areas are present
on the abdomen at the bases of the cornicles.

The eggs (fig. 5, a) are laid in the crevices of the bark or between
the leaf bud and twig, and when first deposited are pale greenish, but

4 BULLETIN 112^ U. S. DEPARTMENT OF AGRICULTURE.

they soon change to shining black and retain this color until theyj
hatch in the spring.

SPECIES LIKELY TO BE CONFUSED WITH THE OAT APHIS.

This species may be recognized in the grain field by the pinkish,!
orange, or reddish areas on the abdomen at the bases of the comiclesJ
It may also be distinguished by the wing venation, by the short^j
slightly swollen cornicles, by the mottled pattern of coloration of
the abdomen, and in the winged form by the rows of black spots oi^
either side. The antenna^ also differ from those of other species.

The large green grain-aphis {Macrosiphum granarium Kirby) is
larger than Aphis aveme and does not have the colored areas at the
base of the cornicles. These last are longer, reaching nearly to the
tip of the Cauda, or tail, and are more cylindrical, and the antennae
are longer in relation to the length of the body.

The spring grain-aphis, or "green bug" (Toxoptera graminum
Eond.), is more nearly the size of Aphis averue, but it need not be
confused with that species if we remember that it is pale green, about
the color of the wheat leaf, and that this coloration is quite uniform
over the entire abdomen ; that it does not have the orange or reddish
areas at the bases of the cornicles; and that the winged female is
without the black spots on each side of the body. Further, the
venation is ordinarily different in the two species, the median vein
of avencB (fig. 3) being twice branched, except in rare instances,
while in the " green bug" (fig. 4) it is but once branched.

Aphis averuB is readily distinguished from other aphides on apple.
Aphis pomi De G., the most common apple aphis, is quite different,
the wingless individuals being uniformly pale apple green Avith black
and rather conspicuous cornicles and no trace of orange or pink on
the abdomen about the cornicles. The winged individuals are simi-
lar, except that the head and thorax are shining black and the abdo-
men pale apple green; also the venation of the wing is different, the
last branch of the median vein not dividing near the apex of the
wing. This aphis spends its entire life cycle on the apple and related
trees.

The rosy apple aphis {Aphis sorhi Kalt.) varies greatly in color
from the greenish blue, pulverulent females hatching from eggs to
the more or less pinkish forms. It is slightly larger than the oat
aphis and does not have the pinkish or orange areas about the bases
of the cornicles, although the distal end of the abdomen may be
pinkish, and in some stages, such as the pupal stage of the spring
migrants, the entire body may be pinkish or salmon colored. The

THE OAT APHIS.

6 BULLETIN 112, U. S. DEPARTMENT OF AGRICULTURE.

winged female has its Aving venation much like that of Aphis pomi;
the cornicles are black, tapering and reaching almost to the tip of
body, and the abdomen is rather conspicuously marked by a large
black patch on the dorsum.

HOST PLANTS.

Aphis avenfv has been recorded from a large number of plants, par-
ticularly of grasses. Owing to the confusion with the larger grain
aphis {M aerosiphum graTmrmm) in some of the literature, it is im-
possible in many cases to determine which species of plant-louse was
meant, and consequently the following list includes only those plants
in cases where the identity of the aphis is reasonably certain. This
list does not include all of the plants upon which this species has been
found in Europe.

GRAMINE^.

Wheat, Triticum vulgare

Triticum dicoccum ^
Rye, Secale cereale
Oat, Arena sativa
AVilrl oat. Avena fatiin '
Tiill oat grass, Arrhcnatlierum ela-

tius 3, 4
Barley, Hordeum vulgare
Two-rowed barley, Hordeum distichon ^
Wall barley, Hordeum murinum*
Tiiuolhy, Phleuiii pratense
Canada bine ^rass, Poa compressa
Kentncky blue grass, Poa pratensis
Annnal or dwarf meadow grass, Poa

annua ^
Rough-stalked meadow grass, Poa

tririalis
Crab grass, Syntherisma sanguinale
Upright chess, Bromiis raceiiiosus
Rescue grass, Bromtis unioloides
Cheat, Brotnus secalinus ^' *
Hungjirian bronie grass, Bronms in-

cniiin 3, i
Orchard grass, DactyUs glomerata
Italian rye grass, Lolmm mulUflo-

rum 3, ■*
Perennial rye grass, Lolium perenne 3, *
Redtop, Agrostis alha 3, *
Red fescue. Festuca rubra 3, 4
Sheep's fescue, Festuca ovina s, *
Meadow fescue. Festuca pratensis

l^elatior} 3,4

1 Recorded by Mordwilko as hosts oi' Aphis padl Kalt. — ai-eiiw Fabi-.

3 Recorded by Fabricius ; so far as known, there is no record on this plant from
America.

3 In 1000 Mr. T. H. Parks, at that time connected with the Bureau of Entomology, con-
fined this species with various plants and found that it would breed contentedly and freely
on these plants. Other plants tried, and which the aphides refused, are Muhlenbergia,
Afjropyron occidentale, Panicum viryatum, and P. hulbosum.

* Recorded here for the first time.

'^ Recorded as hosts of this species by Passerini.

GBAMiNE.E— continued.

Hard fe.scue, Festuca ovina durius-

ciila 3, 4
Reed canary grass, Phalaris arundi-

nacea 3. 4
Melic grass, Melica bauhini''

Melica peniciUaris '
Johnson grass. Aiidropogon halepensis^
Broom corn, Andropogon sorghum var.
Sorghum. Andropogon, sorghum var.
Koeler's grass, Koeleria cristata ^
Wild rye, Elymus geniculatus [—are-

nanus] ^
Virginia wild rye. Elymus virginicus *
Nodding wild rye, Elymus canadensis*
Corn. Zca mays
Teosinte (Euchlaena mexicana) 3,4

TYPHACE^.

Cat-tail. Typha latifolia '

AMMIACE.E.

Celery, Apium graveolens

COMPOSITE.

Tickseed, Coreopsis sp.?

MALACE.E.

Apple, Malus malus

THE OAT APHIS.
MALACE^ — continued.

Ninebark, Opulaster opulifoUus.^

AMYGDALACE^.

Plum, Primus sp.

Choke cherry, Padus virginiana

Wild black cherry —

Padus serotina

Padus' padus

Pear, Pyrus communis
Hawthorn, Cratwgus coccinea, etc.
American mountain ash, Sorbus

aiiicricana
Quince, Cydonia vulgaris
Double-flovveriug crab apple (Alalus

sp.)
Wild crab apple {Mains sp.)

In addition to the foregoing list of food plants, Mr. Theodore
Pergande lists dogwood {Cor^nus sp.), shepherd's purse {Bursa bursa-
pastoris), and burdock (Arctium minus) ; but in each case he notes
that it is, or evidently is, accidental.

Although this species, as shown, has a large number of available
host plants, it is more often to be found in the fall and spring on
wheat, blue grass, apple, and pear. In early summer it is frequently
found on oats, wheat, blue grass, and, previous to June, on apple and
pear, and in later summer on volunteer wheat and oats and on blue
grass.

INJURIES AND METHOD OF WORK.

Probably no other species among the plant-lice has been so com-
pletely confused in literature as the one under discussion. Numerous
reports of injury to apple^ wheat, and oats have been made since its
discovery in 1851, but in most instances there seems to have been some
confusion in the species, and it is impossible in such cases to deter-
mine just which of several species may have been responsible for the
damage. Thus in 1865 Fitch - described and figured a Macrosiphum
on wheat, although some of his observations doubtless refer to Aphis
averue. In 1879 Thomas ^ reported a plant-louse which damaged
wheat considerably in Illinois in 186G and again in 1876, but in his
description he has confused two species, Macrosiphum granarium
and Aphis avenm^ and there is no means by which the particular
species troubling grain in the years mentioned can be identified.
Again, Riley in his report for 1889 * discusses, under the name
Siphonophora avena?^ at least two species, and the facts relating
to life history, injuries, parasites, etc., refer to more than one species;
consequently this data must be ignored for the present, although the
colored figures and probably most of the data contained in the arti-
cle refer to MacTOsiphuiiv granarimn rather than to the species under
discussion. The same must be said of many other references to grain

^ Recorded here for the first time.

-Sixth report on the insects of N. Y., 1865, p. 91-97. "Aphis avenw, Fabricius."
2 Eighth report of the State entomologist on the * * * insects of the State of
Illinois, 1879, p. 51-55. "Siphonophora avenw. Fab."
*U. S. Sec. Agr. Rpt. for 1889 (1889), p. 348.

8 BULLETIN 112, U. S. DEPARTMENT OF AGRICULTURE.

aphides in which the author has either failed to describe the insect
or its habits, or has confused two or more species in his- descriptions.
On the other hand, we have one important reference to injury
recognizable as that of the true Aphis avencB. In Insect Life ^ Prof.
F. M. Webster says :

The wingless viviparous females of this species flock to the fields [of wheat]
and on these [wheat plants] give birth to their young, which at once make
their way to the roots, where they continue reproduction, sapping the life
from the young plants. On very fertile soils this extraction of the sap from
the roots has no very serious effect, but where the soil is not rich, and especially
if the weather is dry, this constant drain of vitality soon begins to tell on the
plants. Though they are seldom killed outright, these infested plants cease to
grow, and later take on a sickly look * * *. it is very seldom that the
affected plants fully recover, at least in autumn, and the results must be to
reduce their productiveness the following year.

In January, 1891, Mr. Christian Steiffel, of Salem, Ind., reported
this plant-louse as injuring wheat, causing it to turn yellow and die
out in spots.

Prof. Webster received a report from Wooster, Ohio, of serious
injury to Avheat in December, 189S, on land subject to overflow. The
wheat came up very well and remained green for about a month,
after which it began to assume a brownish cast, and the warmer the
weather and the more sunshine the plants got, the browner they
became. In a letter dated December 4, 1901, to this bureau, Mr, J. D.
Hummell, of Carroll, Ohio, writes:

This plant louse seems to have almost completely destroyed one field of
wheat in which it appeared early in the fall, and is not yet dormant, although
we have had nights when the temperature was down to 15° F.

November 12, 1908, Mr. E. O. G. Kelly, of this bureau, reported
this species abundant on the roots and stems of wdieat at Caldwell,
Kans., and doing considerable and noticeable injury to the early
sown wheat.

Mr. A. A. Cooke, in a letter dated August 21, 1910, reported
damage by this aphis to dwarf broom com at Dale, Union County,
N. Mex., the insect covering the plants and causing the foliage to turn
a reddish color.

This insect was abundant in western North Carolina in March,
1913, reports of serious damage to wheat, oats, and rye having been
received from several parties.

Numerous reports w^ere received by this bureau from Oklahoma
and northern Texas in December, 1913, and January, 1914, to the
effect that the " green bug," which had ravaged the wheat fields in
these areas in 1907, was again abundant and destructive to oats and
wheat. Detailed examinations were made by Messrs. W. E. Penning-

^U. S. Dcpt. Agr., Div. Ent., Insect Life, v. G, no. i;, Dec, 1893, p. 1.52.

THE OAT APHIS. 9

ton and H. E. Smith, of this bureau, under directions from Prof.
Webstef . They found very few of the " green bug," while the oat
aj)his was present in considerable numbers. After a careful examina-
tion of the fields, the conclusions reached were that the injuries
Avere due to one or more of three causes, namely, attacks by the oat
aphis, impoverished soils, and weather conditions, particularly ex-
cessive rains during the late fall and early winter. Of these, weather
conditions seem to have been the cause of the greatest amount of
injury, although in certain areas the damage was more probably
the result of attacks of the oat aphis. However, the parasites were
in noticeable evidence everywhere, so that with normally late winter
and spring weather they should prevent the aphides from becoming
injuriously abundant.

As described by Prof. Webster in the foregoing quotation, the
infested plants take on a yellowish or greenish yellow color, appear
sickly, and cease to make any apparent growth, and since the insect
works on the lower parts of the plant and is not always easily
detected, the cause of the injury may sometimes be overlooked.
During the summer this aphis usually feeds on the under surface of
the leaves, on the stems, and in the axils of the leaves — seldom in
the grain heads, as does Macrosiphum granarium.

CAUSES OF OCCASIONAL OUTBREAKS.

Prof. Webster ^ has made clear the reason for periodic outbreaks of
the spring grain-aphis {Toxoptera graminum), and the usual abun-
dance of the oat aphis in certain years may be attributed to the same
cause. As in the case of the spring grain-aphis, the oat aphis breeds
and multiplies at a temperature of about 40° F., or above, while the
common parasite of these and many other aphides, Aphidius testa-
ceipes Cress., is hardly active at a temperature less than 56° F. Con-
sequently, mild winters and cool springs, when the temperature
fluctuates between 40° and 56° F., permit the aphis to multiply, unin-
terrupted by attacks from their common natural enemy.

LIFE HISTORY OF THE INSECT.

The oat aphis occurs on grains and grasses throughout the sum-
mer, the spring colonies originating either from viviparous females
which passed the winter on wheat, grasses, etc., or from spring mi-
grants from apple and related trees — that is, the progeny of aphides
hatching from eggs laid the previous fall on such trees. The plant-
lice usually become more abundant toward fall, and as the weather
becomes cooler they seek the lower parts or roots of wheat and other

^U. S. Dept. A^M-.. r.ur. Ent., Circ. 85, Mar. 20, 1007, and U. S. Dept. Agr., Bur. Ent.,
Bui. 110, Sept. 6, 1012.

10 BULLETIN 112, U. S. DEPARTMENT OF AGRICULTURE.

plants of the grass family and liere pass the winter as viviparous
females; or the winged fall migrants from grain may seek such
trees as the apple, where the true sexual forms are produced, the
oviparous females of this generation in turn depositing eggs on the
twigs and branches, usually in the axils of the dormant buds or in
crevices in the bark. (Fig. 5.)

In the latitude of La Fayette, Ind., the species commonly winters
either as viviparous females on grains and grasses or in the egg
stage on apple. Farther north, and especially in extremely cold
winters, this species is probably unable to winter in any but the egg
stage, while in the southern parts of the United States, where the
winters are moderate, the aphides may live over winter as vivip-
arous females only, no egg stage appearing.

The theory, put forth by Pergande,^ " that the species is biennial
and that the progeny of the spring migrants from the apple subsist
almost exclusively upon various grains and grasses until the fall of
the second year, when a generation of return migrants makes its
appearance," is hardly a correct one. The writer's experience shows
that while the apple may be a fall or spring host of aven(p, it is not
a necessary alternate host, and that the species may subsist indefi-
nitely on grains and grasses, and especially is this probably the rule
in the Southern States. The species has been reared through more
than GO consecutive generations, covering a period of over two years,
and through three winters on wheat, the w^arm greenhouse being used
to carry the species through the winter months, and the line of
viviparous generations could probably have been continued indefi-
nitely but for an accident, the aphides having been killed when the
greenhouse was fumigated without the knowledge of the writer.

Continuous-generation experiments were conducted at La Fayette,
Ind., in 1909 by Messrs. W. J. Phillips and T. H. Parks and in 1911
and 1912 by the writer. In 1909 and 1911 the summers were unusu-
ally hot, and the experiments were not satisfactory, but in 1912 it
was possible to get continuous first-born and last-born generation
series without breaks. In 1909 Phillips and Parks obtained a maxi-
mum of 15 generations from May 15 to October 7 and a minimum of
8 generations in the same length of time. In 1911 a maximum of
18 generations was obtained from April 29 to October 12, and in 1912
a maximum of 23 and a minimum of 9 generations from May 3 to
November 13, or a mean average of 16 generations. In the Southern
States, where the species may breed throughout the winter months, a
much greater number of generations would occur. In the experi-
ments of 1909 the average number of young per female, in the 21
cages where records were kept, was 30.6; in 1911 the average for

1 U. S. Dept. Agr., Div. Ent., Bui. 44, 1904, p. 7.

THE OAT APHIS.

11

Q " S r/i

12 BULLETIN 112, U. S. DEPARTMENT OF AGEICULTUBE.

17 mother plant-lice was 22.1 young; and in 1912 the average for 43
individuals was 32.7 young, with a range of from 12 to 65 young
per female. There was thus an average for the three years of 32,3
young. The largest number of young produced by a single female
was 103, and normally, in the cooler parts of the year, the number
ranged between 50 and 60. The number of young produced per
day ranged from 1 to 8 per female, and the length of the period from
birth to maturity varied from 6 to 15 days and averaged about 8^
days, excepting in late fall, when the length of time was ordinarily
much greater. According to the numerous tests the species molts
but four times, as do other species.

It will be seen from the foregoing that this species, like many
other plant-lice, is quite prolific, although not so prolific as the
"green bug" {Toxoptera graminuTn) . It is computed that in 15
generations, averaging 30 young jDer female, the progeny from a
single individual, providing all lived and reproduced, would cover
almost the entire land area of the world, or, if packed 256 to the
square inch and piled 25 high to the inch (6,300 to the cubic inch),
would cover the entire State of Texas to a depth of 7 inches. For-
tunately plant-lice are delicate insects, being highly susceptible to
rains and inclement weather, and are preyed upon by many preda-
ceous and parasitic animals, as well as being subject to fungous
diseases.

In 1879 Dr. Cyrus Thomas ^ aptly discusses the winter habits
of the wintering viviparous females in the following words :

When winter appears they move down toward the ground, some of them, at
least, entering the soil and feeding upon the sap of the roots. At any rate, I
find the apterous ones at this time working upon the roots, but at the same
time I find a winged individual above ground. I have also observed them
heretofore at the root of the wheat, late in winter, while snow was on the
ground ; and what somewhat sui-prised me. I found them busy at work under
the snow, and the apterous females bearing well formed larvae.

There are numerous office records in which the occurrence of this
plant-louse is reported on wheat and gi-asses during the winter
months, but the following individual record will substantiate the
belief that the insect may survive even rather severe winters as
viviparous females. At Wellington, Kans., Mr. T. H. Parks found
adult wingless viviparous females of the oat aphis on wheat roots
April 9, 1910, and these had undoubtedly passed the winter on wheat,
or were the direct progeny of overwintering females. The winter
of 1909-10 was an unusually severe one at Wellington, according
to Mr. E. O. G. Kelhs the ground becoming frozen early in Decem-
ber, 1909, and remaining frozen until February, 1910, after which

1 Eighth Kept. State Entomologist, 111., 1879, p. 53.

THE OAT APHIS. 13

it alternately froze and thawed until March, 1910, the weather
being so severe that 50 to 75 per cent of the wheat in that vicinity
was killed by the cold.

Sometimes these winter root forms are attended by ants, as has
been observed by Prof. Webster and the writer. The forms which
go to apple migrate early in October in the latitude of La Fayette,
Ind., and usually fully a month later in the latitude of northern
Oklahoma. In the rearing cages it has never been possible to get
the forms from wheat to migrate to apple, the failure doubtless re-
sulting from the use of too small cages. On the other hand, there
was no difficulty in getting the spring migrants to go to wheat and
there continue to reproduce throughout the summer from apple
shoots, even in small lantern globe cages.

NATURAL CHECKS.

Like most j)lant-lice of the genus Aphis, avencp- is freely attacked
by various parasitic and predaceous animals, principally insects, and
doubtless these
are responsible for
the usual control
of this pest.

Among the in-
ternal parasites.
Fitch ^ has re-
corded Toxares

triticaphis Fitch, Fig. 6. — AphicUus testaccipes ovipositing in the body of the
(Praon) AphicUus '^""^ S^ain-aphis. Enlarged. (From Webster.)

ave7iaphis Fitch, and AUotria tritici Fitch, but it is probable that he
reared these from M acrosiphum granarium, rather than from Aphis
avence as was supposed by Mr. Pergande.- In 1894 F. M. Webster "^
reports rearing Pachynewron micans Howard and {Lysiphlebus)
Aphklius testaccipes Cresson {tritici Ashmead). The latter species
(figs. 6 and 7) is the one which ordinarily holds the spring grain-
aphis {Toxoptera graminuin) in check, and doubtless is likewise
beneficial in preventing undue multiplication in avenm. Mr. Theo.
Pergande * reared another species of Aphidius {A. nigriceps Ash-
mead) in considerable numbers from this aphis.

Among the predaceous insects Pergande * has reared a common
syrphid fly {Syrphus americanus Wiedemann) (fig. 8) ; the writer
has reared a species of Aphidoletes from larvae feeding on Aphis

1 Sixth Rpt. on the noxious and otlier insects of the State of N. Y.. 1865, pp. 98-112.

2 U. S. Dept. Agr., Div. Ent., Bui. 44, 1904, p. 13.

3 Ohio Agr. Expt. Sta., Bui. 51, 1894, p. 117.
* Op. cit.

14

BULLETIN 112, U. S. DEPARTMENT OF AGEICULTUKE.

avence at La Fayette, Ind., and Washburn ^ says that this plant-louse
is attacked by a "red mite.'' Of the ladybird beetles which attack
this aphis, Fitch mentions Ilipfodamia parenthesis Say, Coccinella
9-notata Herbst, and Coccinella S-notata Kirby, although it seems
probable that Fitch was dealing with a different plant-louse, and he
may not have observed them feeding on the oat aphis. At different
times assistants of the Cereal and Foragfe-Crop Insect Investigations
have observed the following ladybird beetles, or their larvas, feeding
on the oat aphis in various parts of the United States: Cycloneda
munda Say, Coccinella 9-notata Herbst, Megilla maculata DeG.,
Scymmis sp., and Hippodamia convergens Guer.
(fig. 9), the last species being by far the most
abundant, and consequently the most useful of
the coccinellids in the control of the aphis.

In addition to the foregoing enemies, the
larva? of several species of lace-wing flies
(Chrysopidse) are known to feed upon this
aphis.

Miss Margaret Morse, of Worcester, Mass.,
(in litt.) has found that quails eat these aphides
in confinement, and while definite field observa-
tions are lacking, it is quite probable that the
quail, or bobwhite, as well as other birds fre-
quenting grain fields, plays an important part
in the control of this and other grain aphides.

Among other natural agencies which assist in
holding the aphis in check are fungous diseases.
These, like most fungi-attacking insects, thrive
best under moist conditions; hence the diseases
commonly attacking plant-lice are most preva-
lent and useful in moist seasons. Eains likewise
have a beneficial effect, particularly " driving "
rains.

Webster ,2 in his Ohio report, " suspects "' two
minute insects, Gonatocerus hrunneus Ashm. [MS.] and Polynema
longipes Ashm. {Co^mocena citripes Ashm.) as destroying eggs of
avence, but this observation has apparently never been authenticated.

Fig. 7. — Dead aphides,
showing holes from
which the matured par-
asites of Aphidius tes-
taceipes emerge. The
top figure shows the
lid still attached, but
pushed back ; the bot-
tom figure shows the
parasites e m e r gi n g .
Enlarged. ( From Web-
ster.)

REMEDIAL AND PREVENTIVE MEASURES.

As in the case of the well-known spring grain-aphis, or "green
bug" {Toxoptera gramium), it is practically impossible to control

1 Twelfth Rpt. state Entomologist of Minn, for 1907 and 1008, Dec, 1908, p. 50.

2 Op. cit., p. 117.

THE OAT APHIS.

15

the oat aphis after it has once gained much headway in numbers and
diffusion, but by proper precautions it is possible to prevent serious
outbreaks.

Fig. 8. Byrphus americanus, whose larva destroys the oat aphis, a, Female fly ; h, second
abdominal segment- of male. Enlarged. (From Webster and Phillips.)

DESTRUCTION OF BREEDING PLACES.

As has been observed by the writer and other assistants of the
Cereal and Forage-Crop Insect Investigations, the plant-louse under
discussion thrives best in rank-growing wheat, for instance in spots
where manure piles or straw stacks have stood, as well as in the
vicinity of straw
stacks where the
growth of grain
is usuall}^ luxu-
riant. In fact,
observatio ns
show that the lat-
ter place is the
usual center of
infestation, for
during the colder
winter months
the plant-lice

may be found here when it is impossible to locate them elsewhere.
Such locations also provide much better protection from inclement
weather, and reproduction may continue, more or less, throughout
the winter. Therefore it is evident that if the growth about straw

Fig. 9. — The convergent ladybird {Htppodamia convergena),
an enemy of the oat aphis : a, Beetle ; h, pupa ; c, larva.
. Enlarged. (From Chittenden.)

16 BULLETIN 112, U. S. DEPARTMENT OF AGRICULTURE.

stacks be plowed under or otherwise destroyed late in fall, the aphides
harbored thereon will be destroyed. In some cases it may be de-
sirable to destroy this vegetation even earlier; that is, before the
winter wheat is planted or at least before it makes any growth above
ground. Likewise the pasturing of cattle in wheat and oat fields in
Oklahoma and Texas during the late fall and early winter is desir-
able; indeed, observations made by Messrs. ^Y. E. Pennington and
H. S. Smith, of the Cereal and Forage-Crop Insect Investigations,
show that where this procedure had been followed, the grain was
practically free from the oat aphis, although adjoining unpastured
fields showed rather heaA-y infestation.

CULTURAL METHODS.

As in the case of many other grain pests, crop rotation is of much
importance in the control of this aphis, ^^^leat fields should be
located as far from the previous year's grain fields as possible, and
especially should they be planted some distance from standing straw-
stacks. It is also advisable to plant grain as far as possible from
apple and other trees, which harbor the insect during the fall,
winter, and spring months.

SPRAYING.

Direct applications are hardly practicable in grain fields, but
where only small areas are badly infested spraying with blackleaf-40
at the rate of 1 part of this insecticide to 900 parts of water, plus 1
pound of soap to each 100 gallons of spray liquid, will doubtless
prove efficacious, providing the application is thorough.

Another method which might be adopted in localities where the
aphides freely migrate and deposit eggs on apple, is spraying such
trees early in spring before the eggs hatch, preferably just pre-
vious to their hatching and while the trees are yet in a dormant
condition, with commercial lime-sulphur mixture at the rate of 1 part
of the mixture to 8 parts of water.

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•iUTsi^

BULLETIN OF THE

No. 113

Contribution from the Bureau of Entomology, L. O. Howard, Chief
August 22, I9I4.

(PROFESSIONAL PAPER.)

THE LESSER BUD-MOTH.

By E. W. Scott and J. H. Paine,
Entomological Assistants, Deciduous Fruit Insect Investigations.

INTRODUCTION.

During the spring of 1912, while engaged in apple spraying experi-
ments at Benton Harbor, Mich., the senior author noticed the work
of a small larva in the buds of unsprayed apple trees. The injury
inflicted by this minute insect was quite severe in a neglected orchard
near the laboratory, and this insect, among others, was the most
important factor in the destruction of the entire crop of fruit. From
the character of the injury, the attack on the swelling buds; and the
tying together of the growing leaves the damage was at once at-
tributed to the eye-spotted bud-moth {Tmefocera ocellana Schiff.).

In 1913 a study was made of the life history and habits of this
insect, supposedly the eye-spotted bud-moth, and experiments were
tried with remedial measures. The first discrepancy noticed between
the habits of this insect and those of the eye-spotted bud-moth, as
stated in literature, was the fact that the hibernaculse were not neces-
sarily situated near the buds, but were to be found in any suitable
place upon the limbs. Following this, many other even more strik-
ing differences in habits were noted during the course of the season,
and the fact was soon impressed upon the writers that they had to
deal with an insect whose economic importance had not been recorded
in the United States,

The adult moths, upon submission to Mr. August Busck, of the
Bureau of Entomology, were identified as Recurvaria cratcegella
Busck (1903),^ a species described by him (with no indication of its
life history) in 1903 from material submitted by Mr. William Dietz
from Hazleton, Pa., who reared it from hawthorn {Crataegus tomen-

1 Bibliographic citations in parentliesis refer to " Literature cited," pp. 15 and 16.
Note. — Describes an imported insect which is very destructive to several kinds of
growing fruit and has attained quite wide distribution throughout the Northeastern and
North Central States.
45779°— 14

2 BULLETIN 113, U. S, DEPARTMENT OF AGEICULTUEE.

tosus) in June. Busck makes the following statement in his de-
scription :

I am, at present, unable to separate this siiecies from a series of authentic
European specimens of R. nancUa Iliibuer, and I am conscious of the probability
of my making a synonym of this species, the life history of which, according to
Meyrick's Handbook of British Lepidojttera, is not definitely known, but whichi
is A-ariously said to feed in flowers or the shoots of pear or on lichens growingj
on the trunk.

However, in the same year Houghton (1903) published a short]
though complete account of the life history of Recurvaria nanellaA
corresponding in detail to our observations in Michigan. In view of
this identity between the life histories as observed in Europe am"
America, Busck feels certain of the identity of the two insects,
appears in a statement by him in the accompanying footnote.*

HISTORY OF THE SPECIES IN EUROPE.

Stephens (1834) records Recurvaria nanella as "not very uncom-
mon in gardens within the metropolitan district (London), frequent-
ing the trunks of apple trees in June and the beginning of July."

Stainton (1854) records the larva as feeding in May, in England,
on the pear, making a gallery across the flowers with pieces of the
petals and stamens interwoven with silk.

Eossler (1871-72) observed the tying together of the young leaves
of fruit trees by larva? of Recurvaria nanella and its effect in hinder-
ing the development of the new leaves, at Wiesbaden, Prussia. The
insect was present in such large numbers as to attract the attention
of the public to the deformed trees and to arouse the fear that serious
harm would result. In view of the fact that the larva was so small,
ate so little, and did not attack the blossoms, Rossler considered that
it w^as not to be feared.

Houghton (1903) published quite a complete though short account
of the life history and habits of Recurvana nanella from an eco-
nomic jDoint of view, as observed by him in England. His attention
was directed to the insect in an apricot orchard, where the crop had
been practically destroyed by it in previous years. He was the first
to note the fact that the larva, after hatching, passes the time before
hibernation as a miner in the leaf. He also observed that it was the
habit of the larvae to bore into the swelling buds in the spring. The
larvae appeared in swarms on peaches and apricots and less com-
monly on cherries and plums. In his description of the lar\a he men-

i Recurvaria crataegella Busck (Proc. U. S. Nat. Mus., v. 25, p. 811, 1903) is
identical with the Kuropean R. nanella Iliibner, as already suggested in tlie description.
At that time the life history of the species was but fragmentarily known in Europe, and
it was deemed the soundest course to give the American form a separate name, even
though it was realized that it would probably prove the same as the European species.
The subsequent careful study of the life history in Europe by J. T. Houghton and in
this country removed all doubt about the synonymy. — A. B.

THE LESSER BUD-MOTH. 3

tions the different colors assumed by the caterpillars as they near
maturity, and this observation corresponds with our own.

DISTRIBUTION OF THE SPECIES.

The distribution of Recurvana nanella in Europe is given by
Staudinger and Rebel (1901) as follows: Central Europe, Sweden,
northern Spain, southern France, central and northern Italy, Dal-
matia, and southwestern Russia.

Specimens of Recurvana nanella^ all identified by Busck, have
been received by the Bureau of Entomology and by the United States
National Museum from a number of localities in the United States.
As previously stated, the first specimens were received in 1903 from
Mr. William Dietz, Hazleton, Pa. Others have been received from
Pittsburgh, Pa., collected by Henry Engle; from Denton, Md., col-
lected by Quaintance in April, 1905, on peach; from College Park,
Md., by Girault in August, 1905, on apple, " from fruit ; " from Ben-
nings, D. C, collected by Girault in May, 1905, " found resting in
numbers on trunks and larger limbs, simply swarming on peach
trees ; " from Albany, N. Y., by Felt ; from Hampton, N. H., by
Shaw; from Dublin, N. H., by Busck; and from Cleveland, Ohio,
by Prior, the larvae eating apple leaves.

It is improbable that the insect has attained this distribution in the
United States through natural means from a single importation from
Europe, but it is likely that it has been imported a number of times
on nursery stock shipped to various points in this country. In fact,
the importation of this insect, which spends six or seven months in
hibernation concealed in minute cracks and crevices of the bark,
could occur most easily.

FOOD PLANTS.

In the earlier references to Recurvarla nanella the pear is usually
given as the host plant. Houghton, however, failed to observe it infest-
ing this fruit, but finds it swarming on the apricot, destroying the crop.
On the other hand, it is certain from the observations of other authors
that the pear is a favorite food plant, for the insect has often been
observed frequenting pear trees in the vicinity of London. Other
European host plants are apple, peach, plum, cherry, wild plum, and
hawthorn. It has been recorded as attacking the peach in swarms.
At Benton Harbor, Mich., the insect was reared from apple, peach,
pear, plum, and sweet and sour cherries. The infestation was light
on plum and cherry. At Hazleton, Pa., it was reared from a wild
hawthorn.

It is interesting to note the immunity of the Kieffer pear to the
attack of the young larva in the fall or leaf-mining stage. The
larvae, upon hatching, bore into the tissue of the leaves of this va-

4 BULLETIN 113, U. S. DEPARTMENT OF AGEICULTURE.

riety, showing no discrimination against it; the mines, however, are
never developed to any great extent, for the tissue of the leaf about
the mine turns dark and apparently hardens, effectually stopping the
operations of the insect. Many larvae must thus meet their death,
being unable to secure food. This is another instance illustrating
the resistant qualities of the Kieffer variety of pear.

CHARACTER OF THE INJURY.

The first attack by tlie larvae of Eecurvana 7ianella in the spring
is aimed at the swelling buds (PL II, figs. 3 and 4) of both blos-
soms and leaf. The insect bores into the bud, eating the tender
tissues as it goes, showing particular partiality for the young stamens
and pistil, if it has been lucky enough to select a blossom bud. As
the buds open and the leaves begin to expand the larva ties the tips
of the leaves together, spinning about them a tiny silken thread,
thus greatly deforming and hindering the succeeding leaves as they
develop (PL I, fig. 2). It is this injury, when inflicted by countless
numbers of this tiny caterpillar on nearly every bud on a tree (PL
I, fig. 1), that results in a serious, if not almost total, loss of the crop.

SYNONYMY.
Reciirvaria nanella.

Tinea nanella (Schiff.) Hiibn., 1796 (?), Tinese, pi. 39, fig. 267.

Euota prumella Schiff., 1776, Syst. Verz. Schmet, C. 75.

Tinea aleella Fab., 1794, Eut. Syst., v. 3, pt. 2, p. 317.

Recurvaria nana Haw., 1S29, Lep. Brit, v. 4, p. 554.

Trichofripis nanella Hiibn., 1S16, Yerz. bels. Sclimet., p. 425, No. 4143.

Anacampsis nana (Haw.) Curt., 1827, Brit. Ent., v. 4, pi. 189.

Anacampsis aleella (Fab.) Steph., 1829, Syst. Cat. Brit. Ins., pt. 2, p. 197.

Oelechia nanella (Hiibn.) Her.-Schaf., 1S53-1S55, Syst. Bearb. Sclimet., v.

5, No. 416.
Recurvaria nanella (Hiibn.) Heinem., 1870, Die Schmet. Deutsch. u. d.

Schweiz., Bd. 2, p. 280.
ApJianaul a nanella (Hiibn.) Meyrk., 1895, Handb. Brit. Lep., p. 580.
Recurvaria cratccgella Busck, 1903, in Proc. V. S. Nat. Mus., v. 25, p. 811.

DESCRIPTION OF THE LESSER BUD-MOTH.

THE ADULT.

The adult (PL II, fig. 6) of Recurvaria nanella^ or lesser bud-
moth, is a very small streaked moth with a wing expanse of half
an inch, although as it appears on the tree trunks it is not more
than one-fourth of an inch long; the black and white banded legs
are quite conspicuous. The following technical description is as
given by Busck for R. cratcegella (1903) :

Antennae whitish, with indistinct, narrow, dark-brown annulations. La-
bial palpi whitish, with two black annulations on each joint; tip white.
Face, head, and thorax white, suffused with fuscous.

Fore wings white, thickly sprinkled with fuscous.. From near the base
of the costa is an outwardly directed, oblique, ill-defined black streak, which

I

Bui. 1 1 3, U. S. Dept. of Agriculture.

Plate I.

^ :.,,.• 3* ^-'^■;t^:;f-|«,V^

Work of Larv/e of the Lesser Bud-Moth (Recurvaria nanella'.

Fig. 1.— Neglected peach trees partially defoliated by larvae. Fig. 2.— Work of larvie on pear twigs
resulting in the destruction of some of the buds. (Original.)

Bui. 1 13, U. S. Dept. of Agricuitur.

Plate II.

The Lesser Bud-Moth iRecurvaria nanella).

Fiff. 1.— Partially developed mines of larva in a peach leaf. Fig. 'J.— Upper and lower views of pupa
Fig. 3.— Excrement (a) deposited at entrance to larval burrow in eherrv bud. Fig. 4.— Apple bud
infested with larv», showing excrement («) deposited at entrance to burrows. Fig 5— Full-
grown larva in cocoon on bark removed from trunk of pear tree. Fig. fi.— Moth at rest on bark
Fig. 1, slightly enlarged; figs. 2, 5, 6, about six times enlarged; fig. 4, about twice enlarged; fig 3'
natural size. (Original.)

THE LESSEE BUD-MOTH. 5'

does not reach the dorsal edge and which is more or loss interrupted at the
fold and bordered on the outside with white scales. From the middle of
the costa is a similar, parallel, interrupted dark streak still less clearly
defined. At the end of the cell in the middle of the wing is a short, black,
longitudinal "streak ; below this on the dorsal edge is a small black spot, and
on the costal edge are two similar black spots, one at the apical third, the
other just before apex. Cilia white, speckled black, and fuscous. Hind wiogs
light silvery fuscous; cilia a shade lighter than wing; male without costal
hair pencil.

Abdomen dark fuscous, anal tuft silvery gray; legs white, with black an-
nulations; hairs on posterior tibia silvery white. Alar expanse, 12 mm.

The species is very near the other fuscous species of the genus and is easily
confused with Recurvaria cristateUa Chambers, but besides minor colora-
tional variations, it differs in the lack of the hair pencil at the base of the
hind wings in the male.

THE LARVA.

In the larva (PL II, fig. 5) the usual characters of Gelechiidse are
exhibited. Up to the time of hibernation the young larvae are light
reddish brown, with the head, a plate on the second segment, a
small plate on the anal segment, and the upper surface of the legs
Vandyke brown. Soon after issuing from their hibernacula in the
spring they lose the anal plate, and as they reach their full growth
many of them turn from brown to pale green, while others exhibit
various shades between the two. This color variation of the larva
has no effect on the appearance of the moth, for both brown and
green larvae have been isolated and reared, resulting in adults of a
uniform type.

The larva shortly after hatching measures a little over 1 mm.,
or about one-twentieth of an inch, in length. It grows slowly and
at the time of hibernation measures from 2.1 to 2.6 mm., and when
full grown from 8 to 10 mm., or about three-eighths of an inch, in
length.

THE PUPA.

The pupae (PI. II, fig. 2) shortly after the transformation takes
place vary in color from brown to green, as do the larvae; in a few
days, however, they all turn brown. They measure 4 or 5 mm., or
three-sixteenths of an inch, in length.

LIFE HISTORY AND HABITS.

ADULT STAGE.

The first moths (PI. II, fig. 6) issued in rearing cages at Benton
Harbor, Mich., on June 22. Some individuals may have emerged in
the orchards before this date, for they Avere found there in consider-
able numbers on June 23. In the rearing cages the maximum emerg-
ence took place on June 30, and the last moths to appear issued on
July 10; the period of emergence thus covered 19 days. In Table I

6 BULLETIN" 113^ U. S. DEPARTMENT OP AGRICULTURE.

is given the record of the emerging moths in cages in the rearing
shelter and the emergence of hymenopteroiis parasites of the hirvse.
The total number of adults that issued was 383 ; of larval parasites, 14.

Table I.

—Record of emergence of adults and larval parasites «/ the lesser
hud-moth in rearing cages at Benton Harbor, Mich., in 1913.

Date of emergence.

Number of
moths.

Number of

larval
parasites.

Date of emergence.

Number of
motte.

Number of

larval
parasites.

5

10
12
17
21
36
64
47
65
42

0
0
2
4
6
2
0
0
0
0

July 2

13
35
11
0
1
0
2
0
2
0

0

23

3

0

24

4

0

25

5

0

26

6

0

27

7

0

28

8

0

29

9

0

30

10

0

July 1

11

0

In figure 1 this record of the emergence of the adults is graphically
shown.

Fic. 1. — Graphic representation of time and relative emergence of adults of the lesser bud-
moth in rearing cages at Benton Harbor, Mich. (Original.)

During the first few days of emergence the number of males issuing
was greatly in excess of the females; toward the last of the period,
however, the reverse was true. Table II shows the proportion of
males and females as they issued on successive days.

Table II. — Relative number of males and females of the lesser bud moth issuing
in rearing cages at Benton Harbor, Mich., in 1913.

Date.

Number of
males.

Number of
females.

Date.

Number of
males.

Number of
females.

20
12
10
12
16
11

4
3
4
14
17
29

June 30

7
3
6

15

25

July 1

4

26 . . . .

2

13

Total

28

97

103

29

THE LESSER BUD-MOTH. 7

In the field the moths were found in hirge numbers resting on
the trunks of the trees. They remained motionless until touched,
and even then often flew only a short distance, taking a new position
on the same trunk. As many as 15 were counted on the shady side
of the trunk of a small Kieffer pear tree. However, the insects did
not confine themselves to the trunks of the trees alone, but were occa-
sionally found resting upon near-by weeds or upon the branches and,
in a few cases, upon the leaves.

All attempts to feed the moths in captivity failed. They appar-
ently refused to taste the brown-sugar sirup offered them. Nor were
attempts to obtain eggs in confinement more successful, as the insects
would not oviposit under the unnatural conditions of the rearing
cage.

EGG STAGE.

Although a most diligent search was made for the eggs of the
lesser bud-moth, no trace was found of them. This failure is in a
measure due io the fact that nothing of the habits of the insects was
at that time known to us. The adults were seldom observed any-
where except at rest on the tree trunks, although without doubt they
deposit their eggs on the underside of the leaves singly, as evidenced
by the location of the entrance opening to the leaf mines. Eggs in
the egg tubes of the females were observed when dissected, but
nothing of their appearance after oviposition could be sunnised.^

LABVAL STAGE.

It is in the larval stage that Recurvarki nanella spends most of its
life. In Benton Harbor the eggs commenced hatching about July 15.
The larvae at this time are very small, measuring scarcely more than
1 mm. in length. They at once bore through the epidermis of the
leaf on the underside and commence the construction of a most
curiously shaped mine in the inner tissues of the leaf. (See PI. II,
fig. 1.)

The larva first eats its way in a small circle, then constructs a
main burrow which soon divides, the branches in turn again dividing,
often after the manner of the branching of a tree. The form of these
mines, however, is by no means regular, but shows considerable
diversity. The insect does not finish the construction of any branch
of the mine at once, but feeds at will in all parts, keeping the whole

^ As this paper is going to press, speeimons of eggs of the lesser bud-moth have been
received from Mr. E. H. Sicgler, of the Bureau of Entomology, who has been successful in
obtaining them from moths confined in glass jars, at Benton Harbor, Mich. Some of the
eggs received had been loosely deposited among the hairs on the underside of an apple
leaf, singly or several sticking together, for the most part along the veins of the leaf.
Another lot had been deposited on a twig under the edge of a small scale. The egg is
oblong, inclined to be cylindrical, though irregularly so, and is flattened where it comes
in contact with another in the cluster. It is minute in size, measuring about 0.32 mm.
long by 0.2 mm. broad, and is pale, shining yellow in color.

8 BULLETIN 113, U. S. DEPARTMENT OF AGRICULTUBE.

mine open and ejecting all excrement at the point of entrance. Thus,
if the larva, which can be seen through the epidermis, be disturbed,
it will rapidly crawl to another part of the mine; and if followed,
will escape at the entrance hole.

The larvae show no preference as to the point of entrance, eating
their way into the leaf tissues at any point from the midrib to the
edge.

One or many mines may be constructed in a single leaf, according
to the degree of infestation. "Where the insects are numerous, the
mines form a network covering the leaf. It is evident that the adult
female in depositing her eggs lays a number at one time on adjacent
leaves, as the mines usually appear in groups, several affected leaves
occurring on the same twig or neighboring twigs.

Upon the arrival of the first cold days of fall the larvae begin
leaving the mines to construct the small silken hibernacula in which
they pass the winter. The desertion of the leaf mines commenced
about September 12 (1913), the temperature showing the first con-
siderable drop of the season at that time. By September 17 prac-
tically all the larvae had disappeared from the mines. However,
upon picking off small pieces of loosened bark, or lifting up old
bud scales, the larvae were discovered spinning the minute cocoons
which were to be their winter shelter.

No preference w^as shown in the selection of a place for hiberna-
tion, the larvae taking possession of the first available protection.
On large trees the}'^ confine themselves to the twigs and smaller
branches, but on small trees they may be found in abundance on the
larger limbs and trunk. The hibernating larvae on large trees, even
where the infestation is severe, are difficult of location, being very
small and inconspicuous. However, after a few warm days in the
spring the larvae begin to appear in great numbers, as if spontane-
ously.

As the weather warms and the buds on the fruit trees swell, one
may discover, upon close observation, minute masses of reddish or
greenish pellets upon the buds. This is the excrement which the
larva within has deposited at the entrance to its burrow (PL II,
figs. 3 and 4).

The first larvae at Benton Harbor were observed working in the
buds in considerable numbers on April 15, when the buds were just
beginning to swell. They probably began emerging in small numbers
one or two days before.

The insect appears to show little preference as to the point of its
attack on the bud, for it enters either at the side or at the tip. As a
rule those entering at the side do so just at the edge of the bud
scales, although sometimes one will pierce the scales themselves. In

THE LESSER BUD-MOTH. 9

a few cases larvae were noted entering buds which had not begun to
swell, but which* were still in a dormant state. Over the entrance to
the burrow the caterpillar spins a fine netlike web. The larva bur-
rows to the center of the bud both by means of eating its way, the
material passing through its alimentary canal, and by biting off bits
and carrying them to the outside. The latter method is used when
the insect is piercing the tough outer layers of the bud.

Should the temperature drop after a warm day has tempted the
caterpillars to come out of hibernation, but before they have had the
opportunity to enter a bud, they will seek shelter under loose bark
on the limbs. Many larvae were found under the bark on April 16,
but by April 23 all had apparently entered buds.

As before mentioned, the larva upon entering a bud makes its
way directly to the center, there feasting on the tender ovary of the
unopened flower, provided the insect has entered a flower bud, which
the majority do. It is this habit which does the greatest amount of
injury (PL I, fig. 1), for often every bud on a large limb will
be affected. After consuming the inner portions the larvae feed
upon the leafy tissue of the bud, remaining within until the bud
expands and the leaves begin to unfold.

As the first leaves open out, the larva fastens them together, spin-
ning its fine strand of silk as it crawls about (PI. I, fig. 2). It now
constructs for itself a shelter or cocoon of silk, often rolling over the
edge of a leaf and constructing it from within, or bringing the tips
of several leaves together and spinning it in the midst, or making a
combination of the tAvo methods. As a rule, the larvae during the
day are to be found at rest within this cocoon, giving evidence for
the supposition that the insects are nocturnal feeders.

On May 15 it was noticed that some of the nests in the leaves were
empty, and by the next day a large percentage of the larvae had dis-
appeared. However, a search revealed the caterpillars under bits of
loose bark on the limbs and trunk constructing cocoons in which to
pupate (PL II, fig 5). On large trees where there is a great deal
of roughened bark the cocoons are difficult to locate, but on smaller
trees they will be found clustered in the crevices on the trunk;
this is especially true on young pear trees, where most of the bark
is smooth, affording the insects no shelter. A search among the leaves
and debris on the ground beneath the trees revealed a few larvae trans-
forming in the shelter there afforded.

The last crawling larvae in the orchard were found on June 19.
Thus the larval stage covers an average period of about 10 months.

The number of molts of the larva was not accurately determined,
the only data taken on this subject being measurements of the width
of the head taken at successive intervals during the development of

10

BULLETIN 113, U. S. DEPARTMENT OF AGRICULTURE.

this stage of the insect. These measurements, arranged numerically,
are given in Table III. It is not the writers' opinion that these
figures show definitely the number of molts, but they are presented
merely for what they are worth. However, a study of Table III
seems to warrant the interpretation that there are five instars, or four
larval molts. In the last instar considerable variation in the width
of the head will be noticed, but as this same variation is found
among full-grown larvae taken from their cocoons, they are all con-
sidered as belonging to the same stage.

Table III. — Measurements of ividth of head of larvce of the lesner bud-moth
taken at intervals throughout their decelopment at Benton Harbor, Mich,.,
in 1913.

Date.

Width of
head.

Stage.

Date.

Width of
hei.d.

Stage.

Mm.

Third molt.

July 2'J (just hatched).

0.12
.12

J/tti

.'l2

0.31

.14

.31

.16

April 8 (in hiberna-

.34

.15

tion).

.35

.16

.36

.16

First instar.

.36

.16

.38

Fourth In-

.16

.38

star.

.16

April 18 (in buds)

.38

August

.16

.41

.16

.41

.16

.43

.16

.43

.48

First molt.

Fourth molt.

.19
.19

.56

.19

.57

.19
.20
.21

Second in-
star.

,57
.59
.60

.21

.62

.21

.62

.21

.64

.64
.64
.66
.86

Fifth instar.

Second molt.

.245

.245

.96

September

.25
.26

Third instar.

1.12

.60

.275

May 27 (in cocoon)

.64

.275

1.02

PUPAL STAGE.

The first pupa? (PI. II, fig. 2) of the lesser bud-moth were found
on May 18 under the loose bark on the trunlis of young peach trees,
incased in their small, white, silken cocoons. The last larvae to
pupate in the rearing cages did so on June 16. The average time
spent as a pupa is about 19 days, varying, however, from 15 to 30
days.

Table IV is a record kept of isolated larvae, giving dates of pupa-
tion and of emergence as adults.

THE LESSER BUD-MOTH.

11

Table IV. — Pupation and emergence record of the lesser bud-moth in rearing
cages at Benton Harbor, Mich., in 1913, showing number of days spent as
pupa'.

Date of—

Days.

No. of observation.

Date of—

No. of observation.

Pupation.

Emer-
gence.

Pupation.

Emer-
gence.

Days.

1

June 2
June 3
...do....

June 25
June 27
...do

23
24
24
30
21
21
21
21
21
22
22
18
17
19
18
18
18
18

19

June 12

Juno 14

do

June 30

...do....

do

18

2

20...

16

3

21

16

4

...do

July 3
June 27
...do

22

do

do

16

5

June 6
...do

23

do. .

do

16

6

24

do

July 1
July 3
July 1

...do

do

17

...do

...do

25

do

19

8

...do

...do

20

Jime 10

...do....

do.

15

9

10

...do....
...do

...do....
June 28
...do

27

28

15

15

11

...do

29

do

July 2

16

ll!

June 9
...do ..

June 27
June 26
June 28
...do....
..do ..

30

31

do

16

13

...do....

July 3

17

11

...do

Id

June 10
...do

IS 9

IG

Maximum

Minimum

30

17

...do

...do

IS

June 12

June 30

INSECT ENEMIES.

The following hymenopterous parasites, representing six families
and seven genera, were reared from Recurvai'ia nanella., from ma-
terial collected in the larval and pupal stages, and confined in breed-
ing jars. Braconidae: Phanerotoma recurvarice Cushman; Ichneu-
monidse: Dladegma sp. and Itoplectis sp. ; Pteromalidse : A broken,
undetermined specimen ; Encyrtidae : Eupelmus sp. ; Eurytomidse :
Eurytoma sp. ; Chalcididse : Dibracliys sp.

EXPERIMENTS IN CONTROL.

Experiment I. — A young apple orchard at Benton Harbor, Mich.,
was used for experimental spraying against the lesser bud-moth.
This orchard consisted of 50 trees of the Oldenburg {Duchess)
variety about 9 years old. Early in the spring, before the buds began
to swell, the trees were examined and numerous hibernating larvae
were found under the loose bark, the infestation appearing uniform
over the entire orchard. The orchard was divided into eight plats,
each plat consisting of not less than eight trees. The material was
applied with a hand barrel sprayer equipped with Vermorel nozzles.
The results were determined by actual count of all infested and un-
infested fruit and leaf buds from five trees of each plat, 10 days
after the blossoming period. The results are shown in Table V.

12

BULLETIN 113, XT. S. DEPAETMEKT OP AGRICULTURE.

Table V. — Spraying experiments against the lesser bud-moth on apple, Benton

Harbor, Mich., 1913.

Plat
No.

II
III

iIV

IV

VI

Treatmqpt.

One application of commercial lime-sulphur solu-
tion (1 gal. to 8 gals, of water) on Apr. 8. Trees
dormant

One application of soda-sulphur solution (1 lb. to
5 gals, of water) on Apr. 8. Trees dormant

One application of imfiltered lime-sulphur solu-
tion ( 1 gal. to 8 gals, of water) on Apr. 8. Trees
dormant

Two applications of arsenate of lead (2 lbs. to 50
gals, of water) on Apr. 16, when buds began to
swell, and on May 1, when cluster buds opened. .

Three applications'of arsenate of lead (2 lbs. to 50
gals, of water) on Apr. 10, when buds bcfran to
swell, on Apr. 24, when cluster buds were halt
open, and on May 1, when cluster buds were open .

Check (imspray ed )

Number
of buds
infested.

1,G38
080

924

956

523

Number
of buds
sound.

7,5.34
4,228

5,918

7,019

8,000
4,129

Total
number
of buds.

9,172
4,908

6,842

7,975

8,529
9,078

Total
percent-
age of
sound
buds.

82.14
86. 14

86.49

88.01

93.86
45.48

1 Lime-sulphur solution, U gallons to 50 gallons of spray, was added in the last application in plats IV
and V, mairuy for the control of apple scab.

As will be noted, the best results v^ere obtained on Plat V, where
three applications of arsenate of lead were used. In this case the
buds were kept covered with poison, so that the larvse had little
chance to gain entrance into them. The next best results were
obtained where two applications of arsenate of lead were used. How-
ever, the application of the lime-sulphur and the soda-sulphur solu-
tions when the trees were dormant, both used at the strength recom-
mended for the San Jose scale, were almost as effective as the arsen-
ate of lead. The action of the sulj)hur compounds on the larvse is
not known, but they probably act largely as repellents.^ The larvse
were examined in their hibernacula at various intervals from the
time the application was made until they came out to enter the buds,
and in all cases they were found unhurt and untouched by the spray.
However, this was expected, since their hibernacula were protected
from the spray by the loose bark under which they were hidden.
Then, too, the hibemacular cases are of such construction that they
can not be easily penetrated by spray. /Wlien the larvse emerged,
they disappeared, either having been repelled from the tree or killed
by the action of the sulphur sprays subsequent to their emergence.

Almost the entire crop of fruit on the check trees was lost on
account of the work of the larvse, there being less than half a dozen
apples on each tree, while the crop was unhurt on the sprayed trees.

Experiment II. — An apple orchard of the Rhode Island Greening
variety, consisting of 120 trees about 40 years old, belonging to Mr.
W. H. Woodruff, Benton Harbor, Mich., was also used for ex-

'^ Lime-sulphur solution was found to act as a strong repellent against certain other
lepldopterous larvse in other experiments conducted during the season.

THE LESSER BUD-MOTH.

13

perimental spraying against the lesser bud moth in 1913. Previous
to that year the orchard had been badly neglected, not having been
cultivated, pruned, or thoroughly sprayed for several years. The
owner reported that no crop had been harvested from the orchard
during the preceding eight years, although it is not known that this
was due to the work of the lesser bud moth. However, last season it
was noted by the senior author that almost every bud was infested
with this insect, resulting in a total loss of the crop. The experi-
mental spraying was done with a gasoline-power sprayer equipped
with nozzles of the Vermorel type. The orchard was divided into
six plats, each containing not less than 14 trees. The treatments and
dates of application are shown in Table VI.

Table YL— Treatments and dates of applications of sprays for the lesser bud-
moth, Mr. W. H. Woodruff's apple orchard, Benton Hartor, Mich, 1913.

Plat No,

I

II
III

IV
V

Treatment at-

First application, Apr.
(Trees dormant.)

Lime-sulphur solution (1 : 8).
Lime-sulphur solution (1 : S) .
Soluble-oil solution (1 : 15).

Blackleaf40

None

VI Check (unsprayed).

Second application, Apr. 12.
(Buds swelling.)

Third application, Apr. 29.
(Cluster buds open.)

None

None

None

None '_,

Arsenate of lead (2 : 50)'.

None.

Lime-sulphur solution (IJ : SO).

Do.

Do.
Lime-sulphur solution (1 : 50)
and arsenate of lead (2 : 50).

As the trees in this orchard were too large for counts to be made
of the infested and uninf ested buds, the results were determined only
by observation and by comparing the amount of the fruit that set on
the sprayed and unsprayed trees. While the infestation was not as
heavy in this orchard this year as last, the larva? were numerous
enough materially to affect the crop, and at the time of blossoming
quite a contrast could be noted between certain sprayed plats and the
unsprayed plat.

Entirely satisfactory results were obtained on Plat I, which re-
ceived only an application of lime-sulphur solution at the rate of 1
gallon to 8 gallons of water when the trees were in the dormant state.
Only a few larvse could be found on these trees at blossoming time,
and there was practically no loss of fruit from their work, the trees
bearing a good crop. Plat II received the same treatment, with the
exception of an additional application of lime-sulphur solution at
the rate of 1^ gallons to 60 gallons of water when the cluster buds
opened. The results were the same as on Plat I. Plat III, sprayed
in the dormant state with soluble oil at the rate of 1 gallon of the oil
to 15 gallons of water, and Plat IV, receiving a dormant application
of blackleaf 40 at the rate of 1 gallon of this insecticide to 800 gal-
lons of water, gave no noticeable results. Both of these plats re-

14 BULLETIlsr 113, U. S. DEPARTMENT OF AGEICULTURE.

ceived an application of lime-sulphur solution at the rate of 1^ gal-
lons to 50 gallons of water when the cluster buds opened, chiefly for
the purpose of controlling apple scab. Plat V received two applica-
tions of arsenate of lead at the rate of 2 pounds to 50 gallons of water
when the buds were swelling and wdien the cluster buds opened. The
results on this plat were satisfactory, being practically the same as
where the dormant application of lime-sulphur solution was used.

More than 50 per cent of the fruit buds on the unsprayed trees
were infested with the larvfe, and the trees set less than half a crop
of fruit.

Observations were made throughout the vicinity of Benton Harbor,
Mich., to determine the extent of infestation of the lesser bud moth. It
was noted that practically all unsprayed apple and peach orchards
were badly infested, while all apple orchards which were thoroughly
sprayed for the San Jose scale in the dormant state and followed up
by later sprayings were free from infestation. No apple orchards
were found which received only the dormant application, so that
the effect of this one spraying could not be determined. However,
the peach orchards in this section are sprayed with lime-sulphur late
in the spring, just before the buds open, for control of the San Jose
scale and leaf-curl, and in only a few cases do they receive any other
application of spray. In these orchards, which receive only the
dormant application of the lime-sulphur solution, the lesser bud-
moth is thoroughly controlled, while unsprayed peach orchards are
moderately to badly infested.

RECOMMENDATIONS FOR CONTROL.

The foregoing experiments, as well as general observations made
throughout the infested section at Benton Harbor, Mich., show that
the lesser bud-moth can be controlled by thoroughly spraying the
trees in the dormant state with lime-sulphur solution at 32° Baume
used at the rate of 1 gallon to 8 gallons of water. Lower testing
material should be used at increased strengths. The spraying should
be done just before the buds swell, or preferably when the buds are
swelling. This treatment is especially to be recommended, as it
involves no extra application where it is necessary to spray during
the dormant season for other insects, such as the San Jose scale,
oyster-shell scale, scurfy scale, and blister-mite, and for the peach
leaf-curl.

In cases where it is not expedient to use the lime-sulphur solution
two early applications of arsenate of lead at the rate of 2 pounds to
50 gallons of water should be made. This should be applied first when
the buds are swelling and again when the cluster buds open. This
latter application coincides with the first apple-scab treatment. In

THE LESSER BUD-MOTH. 15

case of a bad infestation it would be advisable to make another appli-
cation of arsenate of lead when the buds are half open or bursting.
It should be borne in mind that thorough control of this insect by
use of an arsenical necessitates keeping the buds covered with poison
as nearly as possible from the time they begin to swell until they
are open.

LITERATURE CITED.

1776. ScHiFFEKMULLER, I. Systematisclies ^'erzeiclinis der Scbmetterlinge der
Wiener Gegend, Wien, 1776.

Original description of Tinea nanella, C. 68. Original description of Euota
pruniella, C. 75.

1794. Fabricius, J. C. Entomologia Systematica, v. 3, pt. 2, Hafniae, 1794.
Original description of Tinea aleella, p. 317.

1796(:0 HtJBNEK, Jacob. Tinete, pi. 39, fig. 267.

Figures Tinea naneUa Scliiff., fig. 267 ; figures Euota pruniella Schiff., fig.
175.

1816. HtJBNER, Jacob. A'erzeicliulss Bekannter Scbmetterlinge, Augsburg, 1816.

Lists Trichotripis nanella Schiff., p. 425, No. 4143 ; lists Euota pruniella
Schiff., p. 408, No. 3930.

1827. Curtis, J. Britisb Entomology, v. 4, London, 1827.

Lists Anacampsis nana from Haworth's MSS., No. 189.

1829. Haworth, a. H. Lepidoptera Britannica, v. 4, London, 1829.

Gives Tinea nanella IliUx and Tinea aleella as synonyms of Recurvaria nana
Haw., p. 554.

1829. Stephens, J. F. A systematic catalogue of Britisb Insects, pt. 2, London,
1829.

Gives Tinea nanella Hiib. and Recurvaria nana Haw. as synonyms of
Anacampsis aleella Steph., p. 197, No. 7214.

1834. Stephens, J. F. Illustrations of Britisb Entomology. Haustellata,
v. 4, Loudon, 1S34.

Noted in gardens on trunks of apple trees in June, p. 215.

1853-1855. Herrich-Schaffek, G. A. W. Sy sterna tiscbe^ Bearbeitung der
Scbmetterlinge von Europa, v. 5, Regensburg, 1853-1855.
Lists as Gelechia nanella Hub., p. 167, No. 416.

1854. Stainton, H. T. lusecta Britannica. Lepidoptera : Tineina, London,
1854.

First account of habit of larva of feeding on pear, p. 129.

1854. Wood, William. Index Entomologicus, London, 1854.

Noted as common in gardens near London in June, p. 170, fig. 1213.

1870. Heinemann, H. von. Die Scbmetterlinge Deutscblands und der Scbweiz.
. . . Zweite Abteilung, Kleinscbmetterlinge, Bd. 2., bft. 1, Braun-
scbweig, 1870.

Description of Recurvaria nanella, p. 280, No. 417.

1871-72. RossLER, A. Beobacbtungen iiber einige in Garten vorkommende
Kleinscbmetterlinge. Jabrb. Nassau. Ver. Naturk., Jabrg. 25/26, p.
424-425, 1871-72.

Describes larvae attacking fruit trees in large numbers.

16 BULLETIN 113, U. S. DEPARTMENT OF AGRICULTUEE.

1895. Meybick, E. A liandbook of British Lepidoptera, London, 1895.
Description of adult and larva of Aphanaula nanclla, p. 580.

1901. Staudingee, O., and Rebel, H. Catalog der Lepidopteren des Palae-
arctischen Faunengebietes, 3. aufl. des. Cataloges der Lepidopteren
des Euroi>iiischen Faunengebietes, Berlin, 1901.

Distribution of Recurvaria nanclla, pt. 2, p. 155, No. 2874.

1903. BuscK, August. A revision of the American moths of the family Gele-
chiidiE. Proc. U. S. Nat. Mus., v. 25, p. 767^938, 1903.
Description of Recurvaria crataegella, p. 811.

1903. Houghton, J. T. Contribution to the life-history of OelecMa {Recur-
varia) nanella, Hb., from an economic point of view. Ent. Mo. Mag.,
V. 39 (ser. 2, v. 14), p. 219-221.

Most complete account of life-history of the species.

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WASHINGTON : GOVERNMENT PRINTING OFFICE : 1914

BULLETIN OF THE

DOTIlHIOfAfflCmiH

No. 118.

Contribution from the Bureau of Entomology, L. O. Howard, Chie!
July 14, 1914.

(PROFESSIONAL PAPER.)

EXPERIMENTS IN THE DESTRUCTION OF FLY
LARV^ IN HORSE MANURE.

By F. C. Cook, Physiological Chemist, Bureau of Chemistry, U. H. Hutchison,
Scientific Assistant, Bureau of Entomology, and F. M. Scales, Assistant
Mycologist, Bureau of Plant Industry,

INTRODUCTION.

The great activity in antifly campaigns in recent years, together
■with the recognition of the fly as a disease carrier, has created such
"widespread demand for some means of destroying the fly that this
investigation has been undertaken for the purpose of finding a chemi-
cal that would destroy this pest in its principal breeding place,
namel}^ horse manure, without injuring the bacteria or reducing the
fertilizing value of the manure. This work was undertaken in 1913
at the suggestion of Dr. L. O. Howard to Dr. C. L. Alsberg, who
has heartily cooperated in this study and secured the cooperation of
Dr. W. A. Taylor. The entomological work Avas done under the-
direction of Mr. W. D. Hunter and the bacteriological work in co-
operation with the laboratory of Mr. K. F. Kellerman. It is the
purpose of this paper to review some recent experiments, the results
of which point to an economical, practical, and effective way of de-
stroying fly larvse by the chemical treatment of manure. A con-
sideration of the larvicidal powders of a number of chemicals more
or less effective as larvicides, together with an account of their effect^
on the value of manure so far as may be estimated by chemical and
bacteriological analyses, is included.

HISTORICAL.

American workers were the first to attack the problem of the chem-
ical treatment of manure with a view to destroying fly larva?. Pio-
neer work of this nature was begun in 1897 by Dr. L. O. Howard,
who showed that kerosene emulsion, while effective with small

45780°— Bull. 118—14 1

2 BULLETIN 118, U. S. DEPARTMEXT OF AGRICULTURE.

amounts of manure, was not practical for use on a large scale. Chlo-
rid of lime, however, was foimd to be a good maggot killer, but
its action on the bacteria was not studied. Dr. Howard (1911)^
published an account of his own experiments and of the work of other
investigators.

Prof. S. A. Forbes (Howard, 1911, p. 197), State entomologist of
Olinois, found that lime, borax, borax and sodium arsenate mixture,
iron sulphate, and carbon bisulphid — the last in closed-box tests —
were effective larvicides.

Herms (1910) claims that many of the common insecticides are
more or less effective if used in proper concentrations and amounts,
but none of these can be applied with safety, as they are poisonous,
inflammable, or corrosive.

^ In 1912 Prof. K. I. Smith (Smith, 1912, p. 64), then State ento-
mologist of Xorth Carolina, found that 2 gallons of kerosene
sprinkled over 25 square feet of a manure pile gave no mdication of
any larvicidal action. Acid phosphate proved entirel}^ worthless
from the standpoint of killing the maggots, even when used at the
rate of 400 pounds to every 2.000 pounds of manure. Finely ground
phosphate rock (floats) had no effect on the larva?. A 4 per cent
formaldehyde solution thoroughly applied to heavily infested manure
piles did not destroy any maggots.

This seems to be the extent of the experimental work, as reported
in the literature, up to the year 1913. It is evident that the chemical
treatment of manure has not received the attention which it deserves.
Moreover, Dr. Howard (1911) has pointed out that all these experi-
ments have left unanswered the question as to what effect the treat-

•ment will have on the manure itself. Xo analyses were made to
determine how the chemical composition of the manure was affected
by the larvicides; nor were any field experiments carried out to
ascertain whether the fertilizing value of the manure was altered in
any way.

MANURE: ITS ROLE IN FLY BREEDING.

As stable manure is one of the most valuable fertilizers known, a
large number of investigations have been carried on to determine the
best means of utilizing as well as preserving it. In addition to its
eontent of nitrogen, phosphorus, and potash the value of manure de-
pends on the number and species of bacteria present, as well as on its
content of organic material which the bacteria convert into plant
food. Manure, when undergoing fermentation in the open, loses
some of its valuable nitrogenous constituents, especially ammonia and

1 Authors and dates ia parentheses refer to '" Literature cited," p. 26.

DESTRUCTION^ OF FLY LARV^ IIST HORSE MANURE. 3

gaseous nitrogen, the extent of the loss depending on the nature of the
fermentation, the aerobic fermentation, due to the rapidity of combus-
tion, producing a greater loss than the anaerobic. To prevent this
loss of plant food in the course of fermentation, various chemicals
have been used, either to retard bacterial action or to fix the volatile
constituents. Among the various substances used for this purpose
maybe mentioned ground phosphate rock (floats), kainit, various lime
compounds, carbon bisulphid, formaldehyde, and ferrous sulphate.

The house fly is attracted to horse manure, possibly by its odor,
and on alighting crawls an inch or so under the surface and there lays
its eggs. On account of the temperature of the manure the eggs
hatch within one day. The larval or maggot stage continues from
four to five days, during which the larvaj migrate to the sides of the
pile and toward the base, feeding on the manure during their journey.
The pupse are found, after a few days, congregated in the outer edges
of the manure near the ground, as seen in Plate I. It is therefore
about 10 days from the time the eggs are laid until the mature fly
emerges.

GENERAL PLAN OF EXPERIMENTAL WORK.

Experiments were carried out at the Experimental Farm of the
Bureau of Plant Industry at Arlington, Va., and continued during
the autumn at the Experiment Station at Audubon Park, Xew Or-
leans, La.j under a cooperative aiTangement entered into by the
Bureau of Entomology, the Bureau of Chemistry, and the Bureau of
Plant Industry.

CAGE EXPERIMENTS.

An idea of the structure of the 15 cages, which were designed by
Mr. W. D. Pierce, of the Bureau of Entomolog}'^, may be gained from
the accompanying photograph (PL II). Each cage has an inside
measurement of 2 by 2 by 4 feet. The bottom of ther cage consists of
a galvanized-iron pan 1 foot high. Above this pan bronzed wire
screening (16 meshes to the inch) is tacked both on the inside and
outside of the framework. These two layers of screening are 2
inches apart. In tliis way manure once put into the cages was protected
from further infestation from the outside. In order to prevent the
larvae from escaping from the sides of the cages through this screen-
ing it was found necessary to fasten sheets of tin on the inside above
the galvanized-iron base. These strips are 1 foot high, and thus there
was afforded a space of 8 cubic feet from which larvae had little
chance to escape. In the bottom of the cage nine small holes were
made which permitted excess liquids to drain off. Some larva? found
their way out through them, but these were caught in the pan below
and a record kept of the numbers thus escaping.

4 BULLETIN 118, U. S. DEPARTMENT OF AGEICULTURE.

The top of the cage is a wooden door which is fastened down
tightly with hinges and hasps. In the center of this door is an open-
ing 5 inches in diameter and above this a board provided with two
openings of the same size. Cone-shaped flytraps are fitted into these
openings. This board is placed in grooves so that either one of the
two traps may be brought over the opening in the door by merely
sliding the board.

On one side of the cage is a small trapdoor 5 inches square through
which samples of manure may be taken out for examination.

Each cage stands on legs 4 inches high and in a galvanized-iron
pan 3 feet square with sides 4 inches high. This pan serves to collect
drip water and escaping larvae, and to isolate the cage from such
predatory insects as ants.

Eight bushels of manure were used in each of the cage experi-
ments. It was dumped in at the top and the chemical, in solution,
was sprinkled on with a watering can. After two preliminary ex-
periments it was found necessary, in order to insure thorough pene-
tration, to use 10 gallons of the liquid per 8 bushels ; that is, at the
rate of 1 gallon to 1 cubic foot. Usually the sprinkling was done in
three layers by putting 2 bushels of manure in the cage and apply-
ing 2^ gallons of the solution. This was repeated in the second layer
of 2 bushels. Finally, the remaining 4 bushels were added and the
last 5 gallons of the solution applied. A^Hien a chemical was applied
in dry condition it was scattered over the surface of the manure,
which was treated in three layers as in the case of the solution; 10
gallons of water were afterwards added.

The manure in the control cages was sprinkled with water equal
to the volume of the solutions of the chemicals used. In this way
the moisture content of the manure was made as nearly as possible
the same in all cages. It will be understood that 10 gallons of
solution were applied to 8 bushels of manure in all the cage experi-
ments mentioned below, unless some other explanation is given.
After treatment in this way the doors of the cages were closed and
the flytraps put in place. The cages were examined every day. The
escape of any larvse into the drip pan was noted, and the volume
of the drip water measured and a sample analyzed. A quart sam-
ple of manure was removed through the small door at the side of
the cage after a day or two and the percentage of living and dead
maggots determined. The larval counts of quart samples were
very unsatisfactory so far as indicating the comparative larvicidal
value of the chemicals, but the results of some of these counts are
given in the tables.

After five to seven daj^s flies began to emerge, and then it was nec-
essary to darken the cages with black cloth tacked on the sides, as seen

Bui. 118, U. S. Dept. cf A

Plate I.

So

DC go
1,1 "C

Bui. 118, U. S. Dept. of Agriculture.

Plate II.

Destruction of Fly Larv/e in Horse Manure.

Cage used in the chciiiical treatment of manure, .':howiiig the flytrap.s at the top, the small door
at the side throuf,'!) which samples of manure ean be removed, the pan for collecting drip
water, and other details of the structure. (Original.)

Bui. 1 18, U. S. Dept. of Agriculture.

Plate III.

ts; v.\

> -

c s

desteuciiojst of fly larv^ in horse manure. 5

on the cage to the left in Phite II. In this way the only light came
from the opening into the flytrap at the top, and flies very soon after
emerging made their way up into the trap. The flies caught in the
traps were chloroformed and counted daily. At the end of each ex-
]:)eriment the total numbers of flies from each cage were compared.
The difference between the total numbers of flies from a cage of
treated manure and from the control cages is taken as an index of
the effectiveness of the chemical. In any one set of experiments
the manure used was all from the same source and, being in fresh
condition, contained only eggs and larvae. It was mixed before
transferring to the cages, but it is evident that under the condi-
tions we could not be sure of an equal infestation in all cages. There-
fore the chemicals were not regarded as having any larvicidal power
if the differences in the totals were small.

OPEN-PILE EXPERIMENTS.

In order to simulate natural conditions a parallel series of experi-
ments was carried out by treating manure piles on the ground. Here
again 8 bushels were used for each treatment, but repeated applica-
tions of both manure and chemicals were made. At the beginning
of an experiment a quantity of fresh manure was divided into piles
of 8 bushels each. Chemicals to be tested were tried at the rate of
10 gallons to 8 bushels except as otherwise noted. One pile was
sprinkled with water only and was used as a control. On the follow-
ing day another lot of fresh manure was similarly divided and piled
on top of that of the previous day, and the treatment repeated. At
the end of four days there was a pile of 32 bushels which had
received four a^Dplications of chemicals. Plato III gives an idea of
the size of the piles and shows that the experiments were carried
out on a practical scale.

Eight to ten days after the fourth and last treatment the piles were
opened and gone over carefully in search of pupa?. The pupse were
collected from the edges of the piles (compare PI. I), spread on
a large sheet of paper, counted, and the numbers compared. Chemi-
cal and bacteriological examinations were made of certain of these
open piles.

METHODS OF SAMPLING.

Manure consists of urine and dung more or less intimately mixed
with straw, wood shavings, sawdust, peat, or other absorbent. ^Vlien
first carried from the stable it is not uniform in composition, as the
dung may predominate in one part of the mass and the straw or
other absorbent in another part. Thorough mixing will help greatly
in making it more uniform, but as the eggs and larvse in the manure

6 BULLETIN 118. U. S. DEPARTMENT OF AGRICULTURE.

are readily shaken out, it can not be mixed as thoroughly as desired,
and consequently there is no way under ordinary field conditions by
which a small sample may be obtained that will be truly repre-
sentative.

The errors due to sampling are necessarily large, and the differ-
ences in the results from the controls show the extent of this varia-
tion. This is unavoidable and must be recognized in all work on
manure, and applies to the bacteriological results as well as to the
chemical data, but is not so pronounced in the former cases, as the
difference between the counts of the controls and treated samples is
so much greater than for the chemical results.

In order to secure the most uniform samples under these conditions
for bacteriological and chemical analyses, the following procedure
for obtaining samples was adopted. Approximately an inch of mate-
rial was first removed from the top and then half a pound of the
underlying manure weighed on a spring balance ; another half pound
was then weighed from the center of the pile, and finally the same
quantity was taken from the bottom. The three samples were -all put
in the same container for transportation to the laboratory, where the
whole samjjle Avas spread out on a clean sheet of wrapping paper and
then cut into small pieces and thoroughly mixed. "Wlien the material
appeared quite uniform the sample was quartered. One quarter was
then cut into half-centimeter lengths with clean shears. The straw or
shavings were cut with the other material. When this was completed
the sample was again thoroughly mixed. As the bacterial content
of manure is ver\^ high, no attempt was made to work under abso-
lutely sterile conditions because the contamination arising from ordi-
nary handling of the material was of no importance when compared
with the great number of organisms present. However, precautions
were taken to prevent excessive contamination by using clean paper,
shears, etc., for each sample. The carefully jDrepared quarter sample
was put in a clean Mason jar.

BACTERIOLOGICAL EXAMINATION.

Two 10-gram samples of the manure, prepared as described above,
were taken for each bacteriological determination. A sterile spatula
was used to convey the sample from the jar to the tared watch glass
on the balance pan. One of the 10-gram samples w^as dried at 100° C.
for one hour to determine the percentage of solids. The other sample
was brushed into a 2-liter flask containing 1 liter of sterile water.
The cotton plug was thereupon replaced by a clean rubber stopper
which had been lightly flamed. The flask was then vigorously shaken
for five minutes and again, after a five-minute interval, for three
minutes. A 1 c. c. sample was then withdrawn and run into 100 c. c.

DESTRUCTION OF FLY LARV^ IN HORSE MANURE. 7

of sterile water. Five dilutions were prepared, ranging from 1 part
ill 10,000 to 1 part in 100,000,000. A duplicate series of Petri dishes
was then prepared from these dilutions and standard beef agar.
After five days' incubation at 28-30° C. the plates were counted. The
average counts of the duplicate plates were taken and converted into
equivalents for 1 gram of dry manure by the use of the figures ob-
tained from the dujDlicate 10-gram samples that had been dried at
100° C.

The results obtained by plating on the standard beef agar are com-
parative and serve to show the germicidal action of the chemicals on
the majority of the bacteria present in the manure. The total bac-
terial counts on this medium include not only some of the bacteria
that increase the value of the manure by their metabolic processes,
but also many that may decrease its value in the same way by de-
stroying nitrogen salts available for plant food. For this reason the
total bacteriological counts on beef agar are not considered as entirely
indicative of the fertilizing value of the manure. Ifc is even possible
that the germicidal effect of formaldehyde, calcium cyanamid, and
potassium cyanid in the manure might prove highly beneficial, as
Russell and Buddin's (1913) results with formaldehyde, toluene^
cresol, phenol, etc., in the soil indicate.

CHEMICAL EXAMINATION.

The method of taking the samples was described above, but the
samples for chemical examination were twice run through a sausage
grinder after cutting with shears and were placed in screw-capped
Mason jars provided with rubbers and analyzed as soon as possible.
Samples for chemical examination were taken from the control cages
immediately after the experiments were started, and from all 15
cages after 10 days. In this way it was thought an idea of the
change which had taken place in the various samples could be ob-
tained, the changes in the controls being taken as an index of the
normal rate of decomposition of the manure.

The manure samples were analyzed for solids, ash, ammonia, and
nitrogen, using the methods of the Association of Agricultural
Chemists (Wiley, 1908). The total nitrogen determinations were
made by the nitrogen laboratory of the Bureau of Chemistry. The
results obtained by the magnesium oxid distillation method for am- j
monia, although much higher, showed the same general tendencies
as the results obtained on the water extracts.

Water extracts of the manure were prepared from each sample
by taking 25 grams of the finely divided manure and adding 500 c. c '
of distilled water, allowing them to stand for one hour, with occa-
sional shaking. The solutions were filtered through S. & S. folded
filters No. 588, and the following determinations were made : Water-

8 BULLETIN 118, U. S. DEPARTMENT OF AGRICULTURE.

soluble nitrogen, ammonia, amino nitrogen, nitrites, nitrates, and
reaction.

Ammonia was extracted bytheFolin and Macallmn (1912) aeration
method and nesslerized. The amino nitrogen was determined by the
Van Slyke method (Van Slyke, 1911), but as very little nitrogen in
this form was present in the extracts, the figures are not given.
Nitrites were determined with the sulphanilic acid reagent and
nitrates by the reduction method with aluminum foil (American
Public Health Association, Laboratory Section, 1912). Nitrites and
nitrates were not usually found in the samples examined, because the
manure had not stood sufficiently long. The reaction was determined
by taking 20 c. c. of the water extract, diluting with 200 c. c. of
carbon dioxid free water, and titrating with N/20 acid, using
Alizarin red as indicator. Fehling's solution was not reduced by any
of the 20 or more water extracts tested.

GENERAL ACCOUNT OF CHEMICALS USED.

In the course of the season 24 different chemicals were tried in
various concentrations. Of these onl}'^ seven have shown any effective
larvicidal action in the strengths used. In the following paragraphs
some of the chemicals which gave negative results are first noted,
and later in the paper those which appeared to have the greatest
value are described in more detail.

CHEMICALS WHICH GAVE LOW LARVICIDAL RESULTS.

KEROSENE EMULSION.

Kerosene emulsion, prepared according to the Riley-Hubbard
standard formula, was used in strengths varying from 1 part
emulsion in 5 parts water to 1 part emulsion in 50 parts water.
In no case were results obtained which showed any appreciable
larvicidal action. Even from the cage subjected to the strongest
dosage 956 flies were taken, the average from the two control cages
being 1,355 flies.

No chemical analyses of the manure were made. The bacterial
count, where the strongest emulsion (1-5) was used, was 16,600
million per 1 gram of dry manure as compared with 6,130 million
in the controls. These counts were made eight days after treatment
with the chemical, but as the bacterial content of manure varies
greatlj'' and only one determination was made no conclusion can be
drawn.

Kerosene emulsion M^as not used on any open-pile experiments.
We have already called attention to the fact that Dr. Howard in
his tests found that this reagent was ineffective when applied on a
large scale.

DESTRUCTION OF FLY LARV^ IN HORSE MANURE.

Kainit, which consists of potassium chlorid and magnesium sul-
phate, furnished us by Dr. F. Zerban, of New Orleans, was used in
two cage experiments and in one open-pile test. In the cage experi-
ments 4 pounds of kainit were used. The total number of flies
obtained from the treated cages averaged 2,194, and from the two
controls 3,104 flies. In the open-pile experiment three applications
of 4 pounds per 8 bushels were made, and after 10 days about 12,000
pupse were found. The corresponding control pile contained about
20,000 pupa^.

In the two cage experiments no chemical or bacteriological exami-
nations were made. In the open-pile experiment the bacterial count
was- high, 17.5 million, as compared with 5.9 million in the control.
One hundred c. c. of water extract, equivalent to 5 grams of the
manure, from the treated pile contained a trace of nitrites and
nitrates. No nitrites or nitrates were found in the kainit, nor did
the control manure show any. The ammonia nitrogen in the kainit-
treated manure was 12.3 per cent and in the control manure but 8.8
per cent of the total nitrogen. The high bacterial count and the
increased amount of NH3 obtained, as well as the fact that nitrates
were found in the kainit-treated and not in the control manure,
suggests that this compound may have a stimulating action on the
bacteria, but no conclusions are justified from this one test. This
chemical may be used to reenforce manure, but possesses little larvi-
cidal power.

PYKOLIGNEOtJS ACID.

Pyroligneous acid was used in commercial form without dilution.
Certain claims have been made in some districts of the South, espe-
cially in North Carolina, that pyroligneous acid is of value as a repel-
lent, and in our experiments special attention was given to this point.
Two piles of fresh manure of 8 bushels each were sprinkled with
10 gallons of pyroligneous acid. Before treatment no eggs were to
be found anywhere on the surface of either pile. Two hours later
fresh batches of eggs were found on both piles. The pupae collected
numbered about 6,000 and 8,000. Further observations showed that
fly eggs were deposited on other piles of manure treated with the
pyroligneous acid. Evidently the pyroligneous acid has little, if
any, value as either a repellent or a larvicide. The bacterial counts
showed a great increase, rising from 25 million in the control to 653
million in one of the pyroligneous acid piles.

ISTHMIAN CANAL COMMISSION'S LAKVICIDE.

The Isthmian Canal Commission's larvicide, which has been suc-
cessfully applied in the Canal Zone for the purpose of killing mos-
quito larvae, is prepared according to the following formula: 150
45780°— Bull. 118—14 2

10 BULLETIN 118. U. S. DEPARTMENT OF AGRICULTURE.

gallons of carbolic acid are heated to 212° F. and to this 150 pounds
of iinely broken resin and 30 pounds of caustic soda are added and
the mixture kept at 212° F. till a dark emulsion without sediment is
formed. The resultant emulsion is a good larvicide, 1 part to 10.000
parts of water killing mosquito larvte in less than half an hour.
However, we did not find it effective against house-ily hirvic. The
resultS'of three cage experiments are given in Table I. Series A, Xos.
1, 2, and 3. Compared with the corresponding controls (Xos. T, 8,
and 0) it seems as if few. if any. fly larva^ were destroyed, but the
fact that a considerable number of larvse were found in the drip
water from the control and only a few from the three treated cages
should be considered.

The chemical analyses, given in Table I, show variation in the
total nitrogen of the treated and control manures. This is true of
many of the samples analyzed and shows the normal variations.
The water extract of the treated manure showed more nitrogen and
ammonia present than did the water extract of the control manure.
The reactions of the water extracts varied considerably. Xo nitrites
or nitrates were present either in the larvicide treated or in the
control manure.

Unfavorable action on the bacteria is shown where the numbers
are progressively decreased as the volume of the larvicide was in-
creased. The highest count for the larvicide-treated samples is
considerably lower than the lowest control count.

Several open-pile experiments were also carried out. One of these
was started September 15 and the treatment repeated on four suc-
cessive days. From the resulting pile of 32 bushels of manure about
10,000 pupa^ were taken on September 26. The control pile contained
about 7,000 pupae. This was a typical experiment and is sufficient
to show that even with repeated daily applications this reagent is of
no value as a maggot destroyer.

IROX SILPHATE.

The results of three cage experiments with iron sulphate are given
in Table I, Series A, Xos. 4, 5, and 6. The controls for these are
Xos. 7, 8, and 9. The total number of flies caught from these cages
shows that the manure was rather lightly infested. However, a
comparison of the total number of flies that emerged and the number
of larvae found in the drijD pan from treated and untreated cages
indicates that this chemical may have had some larvicidal power.
However, in three other cage experiments not shown in the table
no larvicidal action was evidenced.

Iron sulphate was not used on open piles. The chemical and bac-
teriological findings in Table I show an injurious action on the

DESTEUCTION OF FLY LAEV^ IN HORSE MANURE.

11

manure. The number of bacteria was noticeably reduced, var3'ing-
inversely with the strength of the solution used. The amounts of
water-soluble nitrogen were materially lowered in the iron-sulphate-
treated manure, depending on the amount of iron sulphate employed.
The iron sulphate evidently acts as a precipitant for some of the
water-soluble nitrogen compounds. The ammonia was fully doubled,
due possibly to the reduction of alkaline reaction, two of these three
samples showing a faint acidity. Iron sulphate blackened the
manure and deodorized it, as noted by Forbes. On the whole, we
find iron sulphate less effective as a larvicide than Forbes's experi-
ments seem to indicate. It is important, however, to note that the
amount of iron sulphate used by Forbes was much greater tljan that
used in these tests.

Table I. — Desi ruction of fij/ larva- in horse nuinurc — Results with inctfcctirc
larvicides — Cag<' experiments ut Arlington, Va., summer of 1913.

No.

Series A :
1....

Series B:
1....

Treatment of 8 bushels
of manure; 10 gallons
used whenever solu-
tion was applied.

Canal lan^icide, 1-75 (7i

gallons)

Canal larvicide, 1-75 (,10

gallons)

Canal larvicide, 1-75 (12^

gallons)

Iron sulphate, Impounds

per gallon

Iron sulphate, 1 pound

per gallon

Iron sulphate, -i pound

per gallon ....".

Control (water only)

....do ;

do

Sodium c h 1 o r i d , 2\

pounds per ga lion

Sodium c h 1 o r i d , 1

pound per gallon

Copper sulphate, 1 pound

per gallon

Copper sulphate, i pound

per gallon

Control (water onlv)

....do ".

Larval mor-
tality, 1
quart sam-
ple of ma-
nure 2 days
after treat-
ment.

Alive.

28

Dead.

Num
her.
113

110

179

73

171

81
146
102

76

141
217
101

Per

cent.

0

0

0

32.4

0

25.0
0
0
0

55.5
30.0

67.4

132 57. 4
322 0
298 0

Num-
ber.
6

1

0

0

0

0

15

127

221

0

100

0

Few.

100
30

A

E .

^^

g

&^

Is

"^•o

a

C3

o,^

S

.V

o a

3

s

!S

■2

«

a

Mil-

Per

lions.

cent.

3,700

0.73

2,600

.61

1,600

.53

700

1.05

970

.67

2,800

.76

5,200

.84

6,000

.68

5,100

.65

2,550

.51

.45

648

.69

4,070

.75

3,060

.55

4,800

.72

Water extract.

In per cent

of total

nitrogen.

Per
cent.
35.62

34.43

32.08

10. 48

16. 42

22. 37
26.19
25.00
18. 46

32. 94

28.67

9.71

14. 93
23.45
21.11

•3 ri

2 ^

as

So c
a2^

Per

cent.
6.58

3.93

3.96

5.05

6.72

6. 84
2.62
3.09
2.46

7.65

3.7S

3.78

2.40
2.55
2.08

C.c.
12.00

1.50

10.62

11.25
10.50
6. 5u
5.00

4.40
7.50
2.75

I. lO

7.50

' Acidity.

SODIUM CHLORID (TABLE SALT).

The results of two cage experiments with manure treated with
sodium chlorid are given in Table I, Series B, Nos. 1 and 2. The
corresponding control cages are numbered 5 and 6. The average

12 BULLETIN 118, U. S. DEPARTMENT OF AGRICULTURE.

number of flies from these two controls is 310. Presuming that the
infestation of the manure at the start of the experiment was the
same in all cages, it appears from the table that sodium chlorid used
at the rate of 2^ pounds per gallon killed 55 per cent of the larvse.
The 1-pound per gallon application showed a 30 per cent destruction
of the maggots. The chemical results of the salt-treated manure are
not very different from those of the untreated manure except that
there is an apparent increase in the nitrogen and ammonia in the
water extract of the treated samples. Only one bacterial examina-
tion was made and this showed that the strongest salt solution
reduced the number of bacteria somewhat.

COPPEK SULPHATE.

Nos. 3 and 4 of Series B, Table I, give the results of two cage
experiments with copper sulphate. WTien compared with the con-
trols it would seem that the dosage of 1 pound per gallon killed 67
per cent of the maggots and the one-fourth pound strength 57 per
cent.

The bactericidal power of copper sulphate is well known. When
added at the rate of 1 pound per gallon sufficient copper sulphate
remained in solution to kill 87 per cent of the bacteria. Their number
was not affected by the smaller quantity of this chemical.

The chemical analyses show an injurious effect from the heavier
application of copper sulphate, which reduced the amount of soluble
nitrogen and the alkaline reaction of the water extract. With the
weaker strength the only apparent effect is a slight reduction of
water-soluble nitrogen. No open-pile experiments with copper sul-
phate were carried out.

LIME-SULPUUK MIXTURE.

Lime-sulphur was used in three cage experiments, but in no open
piles. There is no evidence that the lime-sulphur possessed any lar-
vicidal power, for more flies developed from the cage receiving a
1-5 treatment than from the control. The bacteria do not appear to
be affected by this treatment. From two other experiments where
lime-sulphur was used in strengths of 1-15 and 1-30 fewer flies
emerged than in the control, but this was probably due to differences
of infestation.

In addition to the chemicals mentioned, acid phosphate, a proprie-
tary fertilizer, and several proprietary disinfectants were tested with
negative larvicidal results.

PARTIALLY EFFECTIVE LARVICIDES.

In Table II, page 15, some results obtained wnth potassium cyanid^
Paris green, and formaldehyde, which were found to possess some
larvicidal action, are recorded. Each of these three substances in the

DESTRUCTION OF FLY LARV^ IN HORSE MANURE. 13

heaviest application, and formaldehyde in all cases, reduced the num-
ber of bacteria.

POTASSIUM CYANID.

Potassium cyanid gave favorable results in three cage experiments.
These results are given in Table II, Series C, Nos. 1, 2, and 3, the con-
trol being No. 4. Quart samples of manure two days after treatment
showed a large percentage of dead larva? for the two stronger appli-
cations. The total numbers of flies developing were very much re-
duced. It appears that the two higher concentrations killed 93 per
cent of the larvae. The chemical results of analyses of these three
samples of manure show considerable variations, but there is no evi-
dence that the manure had been injured by the application of the
potassium cyanid. The increased alkalinity results of the control
and of No. 2 may be explained by the large amount of water-soluble
nitrogen in these two cases. No open piles were treated with potas-
sium cyanid. This reagent, when used in proper concentrations,
will undoubtedly be found a very effective maggot killer, but its ex-
tremely poisonous nature makes it objectionable and dangerous. The
bacterial counts show that potassiimi cyanid in the manure had no
very definite bactericidal effect. A stimulating action is rather in-
dicated in the two higher dilutions, but as the difference in the num-
ber of bacteria between the three treated samples is no gi^eater than
that between some of the controls, no conclusions can be drawn from
this experiment.

PARIS GREEN.

Paris green was used in three cage experiments, the results of
which, together with those of the corresponding controls, are given
in Table II, Series D. The Paris green was not all dissolved, but was
applied in the form of a suspension. The suspended particles were
deposited on the surface and only the part in solution filtered into the
deeper parts of the manure. It appears from these experiments that
Paris green killed from 70 to 90 per cent of the larvae.

The bacteriological counts vary considerably and inversely with
the strength of the solution used. The most concentrated solution
was strongly bactericidal and reduced the number of organisms by
about 50 per cent. The higher dilutions showed the general stimulat-
ing action of poisons in small quantities. The effect in general is the
same as that of potassium cyanid, but is much more marked.

The water-soluble nitrogen varied with the amount of Paris green
used, and was lowest where the strongest application of Paris green
was made, due probably to the precipitating power of the copper, and
about equal to the control where the two weaker .applications were
made.

14 BULLETIN 118, U. S. DEPARTMENT OF AGRICULTURE.

FORMALDEHYDE.

Formaldehyde solution was used in six cage experiments, but on no
open piles. Three concentrations were tried, by mixing 1 part of
the commercial 40 per cent formalin with 3, 6, and 12 parts of water,
respectively. The results of three of these tests are given in Table
II, Senes E, together with the corresponding controls. In three
experiments not given in the table the infestation of the manure
was so slight that it was not possible to form any judgment as to
tlie larvicidal action of this chemical. Even in the experiments
which are given in the table, the manure was lightly infested. How-
ever, all the concentrations show considerable larvicidal action. Tak-
ing the average total number of flies of the controls it is evident that
from 75 to 85 per cent were killed. It is probable that if this treat-
ment had been made in closed boxes or receptacles to retard the
loss of formaldehyde by evaporation, the larvicidal action would
have been still higher.

As might be expected, the formaldehyde in these dilutions caused
a great reduction in the number of bacteria. The highest dilution
(1-12) killed 99.6 per cent of the bacteria that would grow on beef
agar. The chemical results show a decreased alkalinity of the water
extract. The ammonia results average slightly higher than those
obtained on the control samples, but in No. 2, where the dilution
of formaldehyde used was 1-6, the bacterial count, the water-soluble
nitrogen, the ammonia, and the alkalinity are higher than in eitjier
of the other two treated samples. The fact that formaldehyde pro-
duces an acid reaction, either by conversion to formic acid or by
combining with amino acids, a reaction used by Sorensen (1907)
for the quantitative estimation of the amino acids, may explain the
reduced alkalinit}^ of these extracts. Nitrites and nitrates were de-
tected in all three cases of the manure treated with formaldehyde.
It is interesting in this connection to note that Russell and Buddin
(1913) carried out some experiments on the action of various volatile
antiseptics in the soil, and found that formaldehyde increased the
production of nitrates and ammonia. While formaldehyde is ex-
tremely disagreeable to work with on account of the instating action
which it has on the mucous membrane, nevertheless further work with
this chemical will be undertaken.

DESTRUCTION OF FLY LARV.E IN HORSE MANURE.

15

Table II. — Destruction of fly larvw in horse manure — Results with partially
effective larvicides — Cage experiments at Arlington, Va., summer of 1913.

a .

Water extract.

Larval mor-

tality, 1

a

'CDfl
In per cent \m ^

quart sam-

E§

5f

Treatment of 8 bushels

ple of ma-

c

*-< -4^

1-1

of total >5 ^

No.

of manure; 10 gallons

nure 2 days

P.

"c3

'5

nitrogen, o'"

used whenever solu-

after treat-

■

&

tion was applied.

ment.

c

%

i-

a'C

^ " a>

~-

P.T3

03 . >>" 3

1

^

a

.SoT

a

gg •£§§

.£

£8
>

15

. 3
d

d S' - '='

Alive.

Dead.

11

<^d

f1 » —

=5p-o

<

JVum-

Per

Num-

Mil-

Per

Per

Per

Series C:

hcT.

cent.

ber.

lions.

cent.

cent.

cent.

C.c.

1

Potassium cyanid, 0.1
per cent solution.

2

9

82

93.6

5,250

0.68

19. 85

3.09

10.25

-

Potassium pyanid, 0.02
per cent solution.

11

21

86

93.3

100

7,260

1.00

23.60

2.90

14.50

3

Potassium cyanid,. 0.004
per cent solutioii.

11

4

251

80.6

350

7,620

.63

20.48

Trace.

10.00

\

Control (water only)

64

1

1,287

0

400

6, 1.30

1.12

24.11

3.57

17.65

Series D:

1

0

-

02

35

32

322

70.3

88.7

89.7

0

Few.

Few.

Few.

100

1.740
7.300
19,950
3,060

.70
.59
.56

.55

13.43
22.88
25.00
23.45

2.71
1.86
4.64
2.55

9.00

0

7. .50

3

Paris green, 1-80

0

48

1
0

6.00

4

Control (water only)

7.75

5

do ....

12

0

298

0

30

4,800

.72

21.11

2.08

7.50

Series E:

1

Formaldehyde,' 1-3 solu-
tion.

0

'

20

81.5

1

14

.58

18.97

3.62

.75

2

Formaldehyde, 1-6 solu-
tion.

3

1

16

85.2

22

!4

.46

21.74

4.57

2.00

3

Formaldehyde, 1-12 solu-
tion.

165

15

27

75

0

22

.60

18.33

2.8;?

. lO

4

Control (water only)

32

0

140

0

15

.5,200

.84

26.19

2.62

10.50

h

do.

22
5

0
0

102

76

0
0

127
221

6,000
5,100

.68
.05

25.00
18.46

3.09
2.46

6..';0

fi

.do

5.00

• Nitrites and nitrates were found in Xos. 1, 2, and 3, Series E.

SODIUM FLUORID.

Sodium fluorid was used in two cage experiments. In one it was
applied at the rate of 2 pounds per gallon, and 454 flies developed.
In the other 1 pound per gallon was used, and 1,053 flies developed.
From the two control cages the totals were 6.152 and 5,870. Thus
the stronger concentration destroyed over 90 per cent of the maggots,
and the weaker strength 84 per cent. No open piles were treated.

No bacteriological or chemical analyses were made of the manure
treated with sodium fluorid. From the limited number of tests with
this chemical, it is evident that it may possess some value as a larvi-
cide, and further experiments will be conducted, using commercial
sodium fluorid, although the cost (5 pounds. $1) may prohibit its
general use.

AMMONIACAL GAS MyUOR.

Ammoniacal gas liquor, which is a by-product of the manufacture
of illuminating gas, evidenced some larvicidal effect when
used in the strengths of 1-5 and 1-25. From the cage treated with
the stronger dosage 206 flies were caught and 179 flies from the

16

BULLETIN 118, U. S. DEPARTMENT OF AGRICULTURE.

other. The control cages showed 1,508 and 1,287 flies. The gas
liquor in the 1-5 strength was strongly bactericidal, reducing the
number of bacteria as shown in the control from 6,130 million to
92.8 million. In view of the fact that the gas liquor showed a bacte-
ricidal action and that the transportation of a liquid in large amounts
is expensive, it was not studied further, although it possesses certain
advantages, as it contains a considerable amount of nitrogen, practi-
cally all of which is in the form of ammonia. This nitrogen is,
however, all in soluble and volatile form and easily lost.

CALCIUM CYAN AM ID.

The treatment with calcium cyanamid was tried at the suggestion
of Dr. Alsberg. It has been used in cage experiments at Arlington,
Va., and the results obtained are recorded in Table III.

Table III. — Dcstrnction of fly larva in horse manure — Larvicidal results with
caleium cyanamid — (Jage experiments at Arlington, Va., summer of 1913.

No.

Treatment of 8 bushels of manure with 10 gal-
lons of water.

Larval mor-
tality, 1 quart
sample of ma-
nure 2 days
after treat-
ment.

Alive. Dead

P'lies
emerged.

Larv8B
killed.

Larv89

in drip

pan.

Series F:

1....

2....

3....

i....
Series 0:

1....

2....

3....

i....

Calcium cyanamid, 20 poimds.
Calcium cyanamid, apounds..

Control . . 1

do

Calcium cyanamid, 5 poiuids.
Calcium cyanamid, -1 pounds.
Calcium cyanamid, 3 pounds.

Control..".

....do

Number.

7

52

1,508

1,287

92
761
56
25
204

Per

cent.
99.5
96.3

0

0

20.0

Num-
ber.

51.3
0
0

12
400

39
20
25
50
10

The calcium cyanamid was scattered over the manure in powdered
form and in all cases water was added. From the table it appears
that the 20-pound application killed over 99 per cent of the larvae.
The 5-pound applications gave varying results, as seen in the table,
and in one cage experiment not shown 58 per cent of the larvae were
destroyed. This gives an average larvicidal power of 58 per cent for
this amount of the calcium cyanamid. In one cage test not shown
where 4 pounds were applied, 40 per cent were killed, but in the cage
experiment given in Table III no larvicidal action was apparent.
Since calcium cyanamid is used to some extent as a fertilizer and is
a means of adding nitrogen to the manure, and thus to the soil, it is
highly desirable that a further study of this chemical be made, not
only to determine more exactly its larvicidal action, but also to de-

118, U. S. Dept. of Agriculture.

Plate IV.

<n — '
rr >.■"■

IS?:

-J ^S.

1^ ~s

DESTEUCTION OF FLY LARV^ IN HORSE MANUEE.

17

termine by field experiments whether the amount of nitrogen thus
added compensates for the cost of treatment. The cost of tlie cyana-
mid in 100 or 200 pound lots is about 3^ cents per pound.

The results of two typical open-pile experiments with calcium
cyanamid are given in Table IV. The 5-pound application killed
82 per cent of the larvae and reduced the number of bacteria mark-
edly. The 4-pound application killed 71 per cent of the larva3 and
reduced the bacteria 50 per cent. In both cases the water-soluble
nitrogen, ammonia, and alkalinity were considerably increased.

Table IV. — Destruction of fly larvce in horse manure — Results with calcium
cyanamid — Open-pile experiments (three applications) at New Orleans, La.,
November, 1913.

Treatment of 8 bushels of ma-
nure with 10 gallons of water.

Total
number
of pupae
found
after 8
to 10
days.

Larvae
kiUed.

Bac-
teria
per 1
gram

ma-
nure,
dried

at
100° c.

Water e.N;tract.

No

Manure.

In per cent of
total nitrogen.

AlkiV-
linity,
N/20

Solids.

Total
nitro-
gen.

Nitro-
gen.

Am-
monia
nitro-
gen.

Ii2S04

per 100
c. c. (5
grams
ma-
nure).

Series H:
1

2

Calcium cyanamid, 5 pounds. . .
Calcium cyanimid, 4 pounds. . .
Control. . ."

3,500
5,500
19,000

Per

cent.
81.0
71.0
0

Mil-
lions.
43
75
158

Per

cent.
31.30
30.47
27.14

Per

cent.

0.72
.59
.43

Per

cent.
44.44
47.46
19.54

Per

cent.

8.89
13.56

6.51

C.c.
7.35
8.15
5.30

EFFECTIVE LARVICIDES (BORATES).

The most favorable results were obtained by the use of borax
(sodium borate) and calcined colemanite (crude calcium borate).
Both substances possessed a marked larvicidal action and appeared
to exert no permanent injury on the bacteria. These two borates have
been used in a large number of experiments and the results all uni-
formly show a very high larvicidal action, both in cages and open
piles, and whether applied in diy form or in solution.

A comparison of the total number of flies or of pupa? from borax-
treated manure with the totals from control manure shows a larvi-
cidal power of over 99 per cent in nearly all trials. One of the
reasons why borax is so effective in reducing the number of flies is
due to its toxic effect on the eggs, which do not hatch after contact
with this chemical. The piles in one experiment, started on Septem-
ber 13, 1913, were examined for pupse on September 25. At this time
large masses of eggs of the house fly, perhaps 600 to 800, were found
in a borax-treated pile. They were not empty, collapsed shells, but
kad normal shape and evidently had not hatched. They were some-
what discolored, many having a bluish tinge. Some of these were

18 BULLETIN 118, V. S. DEPARTMENT OF AGRICULTUEE.

taken to the laboratory and examined daily under a microscope.
None of these hatched after a week at room temperature and favor-
able moisture conditions. On October 6, in g-oing over a pile, last
treated with borax solution on September 28, batches of a thousand
eggs or more were found. They had a bluish tinge. A mass of these
eggs with surrounding manure was kept in a jar in the laboratory
for a week and examined daily. Xone had hatched at the end of this
time. Similar observations were made on other borax-treated piles.
No such masses of unhatched eggs were ever found on control piles,
nor on piles treated with other chemicals after the first three or four
days of exposure.

Calcined colemanite, being largely insoluble, did not show this
effect on the eggs. Borax acts ver}^ effectively through its toxic action
on the eggs, but its action is not confined to the egg stage, as larvae
are also killed. In nearly all cases examinations of open piles showed
the presence of dead larva? as well as pupse. In Table V it will be
noted that in some piles large nimibers of pupse were found, but
these were black, shrunken, wrinkled, and were not normal in shape,
having more nearh' the form of the larva* than of the pup?e.
PL IV.) When kept in the laboratory for a long time 1 per
cent or less hatched. The borax had evidently killed them just at
the time of transformation from larvae to pupa?. This may be ex-
plained in several ways. (1) It may be that the larvae, in the
younger stages, resisted the action of the borax they had ingested
but became very sensitive to it at the time of the breakdown of larval
tissues. (2) The action of the borax may be cumulative and so may
not evidence its toxic action until toward the end of the larval stage.
(3) It may be that the larvae in their earlier stages were found some
distance in from the surface where the borax had not penetrated, but
that, when ready to pupate, they migrated to the outer lower edges of
the manure pile where the concentration of the borax was greatest and
were killed by it. The migration of the larvae in the cages and open
piles has already been referred to on pages 3 and 5, and is discussed
more in detail by Mr. Hutchison (1914:).

The fact that small quantities of borax are not detrimental to the
normal fermentation of manure is further shown by some temperature
determinations.

The manure piles were made with no attempt to pack the manure,
because it was believed that the higher temperatures prevailing where
aerobic fermentation was in progress would be an attraction to the
flies. Three series of experiments were used for these tests. The
temperatures were taken by inserting a thermometer about a foot
deep in the top of the piles. As the piles were small the temperature.^
at this depth were very nearly the maximum. The three controls
attained their highest temperature. 66° and 67° C. (150.8° and 152.6^

DESTRUCTION OF FLY LARV.E IN HORSE MANURE. 19

F.) ill f 10111 live to seven days after the experiment was started. At
the same time the borax-treated piles reached their maximum of 58°
to 63° C. (136.4° to 145.4° F.). Even where one-eighth pound of
borax was used the temperature was slightly suppressed, as it reached
only 61° C. (141.8 F.). This effect, however, may have been due to
the borax preventing the growth of organisms which produce fire-
f anging. The effect of borax in entirely preventing this condition has
been reserved for a future investigation. However, it was found that
in three cases the control piles showed evidences of firefanging and
the presence of a white powdeiT mold in the interior. This condition
^\ as never found in the borax-treated jjiles. After attaining a maxi-
mum, the temperature of all the piles declined rapidly. The treated
ones continued lower than the controls.

One manure pile treated with 5 pounds of calcined colemanite
showed a steady decline in temperature from the beginning of the ex-
periment. The bactericidal effect of this large dose is further shown
by a comparison of the bacterial count obtained from a sample of
this pile and that of the control ; a decrease of 64 per cent in the num-
ber of bacteria occurred.

The data of the borax-treated manure are recorded in Tables V and
VI. The open-pile experiments, which are recorded in Table V, show
marked variations in numbers of bacteria, but whether this is due to
a variation in the penetration of the borax because of different nat-
uial factors, or because the samples were not representative of the
pile, although taken in the usual manner (see page 5), can not be
stated at this time. There is a reduction in the number of bacteria
in Series J, Nos. 1 and 2, and Series L, Nos. 1 and 2, where colemanite
was used. There are marked increases in Series I, Nos. 1 and 2, and
Series K, Nos. 3 and 4. In Table VI, where the results are recorded
for the manure experiments made in cages, an increase in the number
of bacteria is seen in all the borax-treated samples.

The manure from the open-pile experiments, Table V, indicates an
increase of water-soluble nitrogen and ammonia in the borate-treated
samples. The reaction of the water extract is increased in all of these
cases. Further, in four of the open-pile experiments nitrites and
nitrates were both found. In no case did the control manure give a
reaction for nitrites or nitrates. The presence of nitrites and nitrates
in the borax-treated piles is very interesting and if it is obtained in
all cases where the borax-treated manure has been allowed to stand
for several Aveeks a strong argument will be presented for its use in
addition to the effective larvicidal action which it is seen to possess.
There are considerable variations in the water-soluble nitrogen and
ammonia results for the open-pile experiments as well as for the
bacterial counts as noted on page 6. -

20

BULLETIN lib, U. S. DEPARTMENT OF AGBICULTURE.

Table V. — Destruction of fly larvce in horse manure — Retiults icith horates-
Expenmcnts on open piles, IS^eic Orleans. La., November. 1913.

Treatment of S bushels of ma-
nure; 10 (;aUons used when-
ever liquid W5V8 .-ulded.

Num-
ber of
ap-
ph-
ca-
tions.

Total
mmi-
bcr of
pupfe
found
after

S-IO

days.

Bacte-
ria per
gram
ma-
nure,
dried

at
100" C.

Manure.

Water extract.

No.

In per cent

of total

nitrogen.

Alka-
linity,
N/20

per 100
c. c, 5
grams
ma-
nure.

Solids.

To-
tal
ni-
tro-
gen.

Nitro-
gen.

Am-
mo-
nia
nitro-
gen.

Series I:
I

Na-borate,' 2J pounds dry (no
water added)

4
4
4

4
4
4

3
3

3
3
3

3
3
3

J 5, 000
24,200
10,000

30

39

2,500

= 985
2575

3 1,700
81,900
20,000

<2,600
<3,200
19,000

Mil-
lions.
141
172
105

.659
.577
316.

2
5

38

36

6

38
26
158

Per

cent.
39.59
39.14
34.54

42. 51
43.29
42.43

36. 69
43.08

34.72
43.01
34.04

30.58
30.77
27.14

Per

cent.

0.60
.55
.46

.67
.68
.63

.52
.56

.47
.53
.49

.49
.44
.43

Per

cent.
30. 67
29.09
30.43

44.78
39.71
30. 16

25.00
21.43

34.04
26.42
24.49

30.61
31.82
19.54

Per

cent.
7.33

8.18

a 69

12.64
11.03
8. 89

8.27
7.50

11.91
11.13

8.78

16.33
9.09
6.61

C.c.
11.05

2

do.i

10.60

3

Control (water)

5.90

Series J:
1

2

Na-borate, 2 pounds dry (no

water) ^

do

10.20
10.90

3

Control (water)

6.50

Series K:
1

Na-borate in solution, i poimd
per gallon

12.45

2

...do

7.85

3

Na-borate > in solution, J pound
per fjallon

8.65

4

..do."

7.35

Control (water)

6.10

Series L:
1

Calcined colemanite, 3 pounds

7.05

2

do

7.20

3

Control (water)

5.30

1 Nitrites and nitnitcs pr&sent.

' Approximate. Of pupte from borax-treated piles about 1 per cent hatch.

3 Of aU tlieise only 10 flies emerged after many days in the laboratory.

< Abnormal in shape and color. Only 1 fly developed in sample of .500 pupoe.

Table VI. — Destruction of fly larvae in fiorse manure — Results with horax — Cage
experiments at New Orleans, La.. November, 1913.

Larval mor-

■g

Water extract.

tality, 1-
quart sam-

•e

\

.

ple manure

,«

fa

In per cent of

r'i

2 days after

S

g

i"

total nitrosen.

3

Treatment ol 8 bushels of
manure with 10 gallons
of liquid.

treatment.

1

0

Ed

11

3
g

0
a

1

"Sg

No.

0 g

i

a

1

•a

a

■a

03
1

id

1

3
0

i

1

£

E
1

11

<

0

H

cq

H

Z

<

Series M:

Mimr>n.

P.ct.

P.ct.

P.ct.

Co.

1

Borax, I pound per gallon..

5

0

15

12

7,392

0..51

33.33

9.41

19.50

2

.do

2
35

0
0

18
38

15
3

3,1)03
7,452

.55

.58

18.18
27. .59

10.18
11.55

16. 50

3

Borax, i pound per gallon..

13.00

4

do

5

82

4
0

22
25

6
50

5,800
2,204

.58
.74

37.93
10.22

10. SO
4.46

13.75

5

Control (water)

8.30

6.

do..

22

0

204

10

3,484

.84

14.29

1.79

7.50

In the cage tests, Table VI, the water-soluble nitrogen, ammonia,
and reaction were lower for the controls than for the borax-treated

DESTRUCTION OF FLY LAEV.E IN" HORSE MANURE.

21

manure. The low water-soluble nitrogen and ammonia result/S of
the controls may possibly be clue to the unusual fermentation going
on in these two samples, as indicated by the peculiar odor. The
fact that, after grinding, the manure tended to cake or lump may
have prevented the usual amount of material from going into
solution. The bacterial counts in the cage experiments are higher
than the controls, and also higher than those of the open piles. This
is undoubtedly due to the artificial conditions of the cage experi-
ments. The increase of water-soluble nitrogen, ammonia, and alka-
linity has been found in all the borax-treated manure, both cage and
open-pile tests, at Arlington and New Orleans.

In Table VII additional cage experiments showing the larvicidal
action of borax, dry and in solution, and calcined colemanite with
water, are recorded. Borax in small amounts, such as 1^ pounds per
8 bushels of manure, destroyed 98 to 99 per cent of the maggots,
and calcined colemanite, even when 2 pounds per 8 bushels of manure
were used, showed the same percentage of larvicidal action.

Table VII.

-Caffc experiments shoicinr/ lankidal action of borates on fly larvw
in horse manure.

No.

Treatment of S bushels of manure; 10 gallons used whenever liquid was added.

Total
number of

flies
emerged.

Series X:

1....

2....

3....

4....

5

Series O:

1....

Na-borate, dry powder, 2i pounds (no water added)

Na-borate in solution, J pound per gallon

do

Control (water)

do

Na-borate in solution, j pound per gallon .

do ,

do

Na-borate in solution, J poimd per gallon .

do

Calcined colemanite, 4 poimds plus water.
Calcined colemanite, 3 pounds plus water.
Calcined colemanite, 2 pounds plus water.

Control (water)

do

12

1

2

6, 152

5,S70

5

13

CS

4G

50

55

165

29

3,069

3,140

RECENT EXPERIMENTS TO DETERillNE MINIMUM AMOUNTS OF BORAX AND CALCINED
COLEMANITE M'HICH ARE EFFECTIVE AS LARVICIDES.

Some recent tests at New Orleans to determine the minimum
amounts of borax and calcined colemanite which are effective have
shown that 0.G2 pound of borax and 0.75 pound of calcined colemanite
are effective as larvicides, but when smaller amounts of either
are used their larvicidal value is reduced. It is therefore appar-
ent that 0.62 pound of borax and 0.75 pound of calcined colemanite
to 8 bushels of manure (10 cubic feet), with the addition of 2 to 3
gallons of water, are the minimum quantities of these borates that
will destroy practically all the fly maggots in manure.

22 BULLETIN 118, U. S. DEPARTMENT OF AGRICULTURE.

ADVANTAGES AND COST OF BORAX.

The great demand for borax, due to its uses in the arts and in the
household, has made this substance available in all parts of the coun-
try. It has the further advantage of being comparatively nontoxic,
noninflammable, and easily transported and handled, as it is a
powder. Thus borax is superior to most of the substances that have
been tested as larvicides. Several investigators (see Haselhoff, 1913)
have shown that in small amounts borax has a stimulating effect on
plant growth, while larger amounts are toxic.

Borax is prepared from colemanite (calcium borate) , which is
mined in California, and has the following composition: Boron
trioxid, 50.9 per cent ; calcium oxid, 27.2 per cent ; water, 21.9 per
cent. The crude colemanite was tested for its larvicidal action, but
this was so slight, undoubtedly due to its insolubility, that it was
discarded in favor of borax and calcined colemanite. Calcined
colemanite is prepared from crude colemanite by simply subjecting
it to high temperatures.

The crude colemanite is not sold as such, but a considerable amount
of the calcined colemanite is used in various industries. The calcined
colemanite is a gray powder and is largely, but not entirely, in-
soluble in water. It costs about 2 cents per pound in large ship-
ments, and in smaller amounts sells at approximately 4 cents per
pound. Borax (NaoB^O-lOHoO) is prepared from colemanite by
treatment with soda ash. It retails at about 10 cents per pound, but
can be obtained in 100-pound lots or more in Washington at 5 to 6
cents per pound. Borax is readily soluble in water.

EFFECTS OF BORAX-TREATED MANURE ON PLANTS.

The chemical analyses and bacterial counts to which references
have been made throughout this bulletin do not indicate any perma-
nent deleterious effects of the borax on manure. On the contrary,
a beneficial effect is suggested. This was especially the case with the
chemical results where an increase of ammonia was obtained in all
cases and no apparent reduction in the total nitrogen was evident.
Nitrites and nitrates were found in several of the open piles where
borax had been applied. In order to be certain of the effect of
borax-treated manure on plants, extensive experiments have been
performed both in the greenhouse and in open plats. The field work
was conducted at four points in the South, as well as on the Arling-
ton farm, and the pot tests were conducted in the greenhouses of the
department at Washington. The following plants were tested :
Wlieat, tomatoes, peas, beets, radishes, kohl-rabi, oats, corn, cucumber,
lettuce, as well as apple seedlings and rosebushes. Such elaborate
experiments seem to be necessary on account of the known toxic

DESTEUCTION OF FLY LARViE IN HORSE MANURE. 23

effects of large applications of boron upon the growth of plants, as
shown by several investigators. In this connection it is important
to note that investigations of Russell and Buddin (1913) in Eng-
land have shown that the application of very small amounts of vola-
tile and some nonvolatile disinfectants have eventually resulted in
the stimulation of plant growth. This same effect is indicated in
some of the experiments with borax.

In the field and pot experiments no deleterious effects were ob-
served from the application of borax at the rate of 0.62 pound per 8
bushels (10 cubic feet) of manure, except possibly on wheat. Larger
doses of borax produced a discoloration of the tips of some other
plants. In our field experiments with winter wheat the plants when
4 inches high showed a decided yellowing of the tips where very
heavy applications of borax were made, but at the start of the
growing period in the spring the yellowing of the tips decreased and
the wheat was nearly normal in appearance. These effects vary with
the plants and the amount of moisture present in the soil. T\niere
rainfall is heavy the effects disappear quickly. At Orlando, Fla.,
for instance, where the experiment was conducted during a drought
and larger amounts of borax than 0.62 pound per 8 bushels were
used, injurious effects were much more evident than in other
localities. In all these cases, however, except at Orlando, recent ob-
servations have shown that the plants have practically recovered —
so far as can be determined without estimating the actual yields,
which can not be done at the present time. From these experiments
it is believed that no injurious effects will follow the application of
the minimum amount of borax found necessary to destroy the larvae,
namely, 0.62 pound per 8 bushels of manure, which may be applied
t-o the field at the rate of 15 tons per acre. If more is necessary,
untreated manure may be used. Some recent pot tests have indicated
that the addition of slaked lime in amounts equal to half that of the
borax present tends to offset the toxic action which results from heavy
applications of borax. Some questions relating to the effects of borax
on the growth of plants remain to be determined, notably its possible
cumulative action, and these will be reported later. It is expected
that interesting results will follow from the experiments now under
way with calcined colemanite, which, though cheaper than borax, is
effective in destroying fly larvae when applied at the rate of 0.75
pound per 8 bushels.

SUMMARY.

CLASSIFICATION OF CHEMICALS TESTED.

The substances used in the experiments dealt with in this bulletin
may be arranged in two classes, as indicated below. The term
" satisfactory " is used to indicate destructive action on fly larvae,

24 BULLETIN 118, U. S. DEPARTMENT OF AGRICULTURE.

noninjurious effect on manure, and luck of extr3mely poisonous prop-
erties. Among the unsatisfactory or partially satisfactory substances
are included several which when used in large amounts may kill fly
larvae but are placed in this class because of the large amount required
or because of their extremely poisonous properties.

Iron sulphate has been used as a larvicide and in considerable
amounts is stated to be effective. However, no studies of the effects
of iron sulphate on the fertilizing value of manure have been re-
ported. Our experiments indicate injury to the manure even from
small applications of iron sulphate (see p. 10). Paris green and
potassium cyanid are effective as larvicides, but are objectionable on
account of their extremely poisonous nature.

Unsatisfactory or Partially Satisfactory Substances.

Kerosene emulsion. Pyroligneous acid.

Kainit. Sodium chlorid (table salt).
IsthmiiUi C:uial Commission Inrviclde. Copper sulphate.

Iron sulphate. Lime-sulphur mixture.

Several proprietary disinfectants. Paris green.

Potassium cyanid. Sodium fluorid.

Formaldehyde. Ammoniacal gas liquor.
Calcium cyauamid.

Satisfactory Substances.
Borax. Calcined colemanite.

By far the most effective, economical, and practical of the sub-
stances is borax in the commercial form in which it is available
throughout the country.

Borax increases the water-soluble nitrogen, ammonia, and alka-
linity of manure and apparently does not permanently injure the
bacterial flora. The application of manure treated with borax at the
rate of 0.62 pound per 8 bushels (10 cubic feet) to soil does not in-
jure the plants thus far tested, although its cumulative effect, if any,
has not been determined.

DIRECTIONS FOR TREATING MANURE WITH BORAX TO KILL FLY EGGS AND

MAGGOTS.

Apply 0.C2 pound borax or 0.75 pound calcined colemanite to
every 10 cubic feet (8 bushels) of manure immediately on its removal
from the barn. Apply the borax particularly around the outer edges
of the pile with a flour sifter or any fine sieve, and sprinkle 2 or 3
gallons of water over the borax-treated manure.

The reason for applying the borax to the fresh manure immedi-
ately after its removal from the stable is that the flies lay their eggs
on the fresh manure, and borax, when it comes in contact with the
eggs, j3revents their hatching. As the maggots congregate at the

DESTRUCTION OF FLY LARVAE IN HORSE MANURE. 25

outer edges of the pile, most of the borax should be applied there.
The treatment should be repeated with each addition of fresh ma-
nure, but when the manure is kept in closed boxes less frequent appli-
cations will be sufficient. Wliere the calcined colemanite is available,
it may be used at the rate of 0.75 pound per 10 cubic feet of manure,
and is a cheaper means of killing the maggots. In addition to the
application of borax to horse manure to kill fly larvae, it may be
applied in the same proportion to other manures, as well as to refuse
and garbage. Borax may also be applied to floors and crevices in
bams, stables, markets, etc., as well as to street sweepings, and water
should be added as in the treatment of horse manure. After estimat-
ing the amount of material to be treated and weighing the necessary
amount of borax a measure may be used which will hold the proper
amount, thus avoiding subsequent weighings.

WARNING IN CONNECTION WITH THE USE OF BORAX-TREATED MANURE.

While it can be safely stated that no injurious action will follow
the application of manure treated with borax at the rate of 0.62
pound for 8 bushels, or even larger amounts in the case of some
plants, nevertheless borax-treated manure has not been studied in
connection with the growth of all crops, nor has its cumulative effect
been determined. It is therefore recommended that not more than
15 tons per acre of the borax-treated manure should be applied to
the field. As truckmen use considerably more than this amount, it
is suggested that all cars containing borax-treated manure be so
marked, and that public-health ofl^cials stipulate in their dkections
for this treatment that not over 0.62 pound for 8 bushels of manure
be used, as it has been shown that larger amounts of borax will
injure most plants. It is also recommended that all public-health
ofiicials and others in recommending the borax treatment for killing
i\y eggs and maggots in manure warn the public against the injuri-
ous effects of large amounts of borax on the growth of plants.

COST OF BORAX TREATMENT.

The amount of manure from a horse varies with the straw or other
bedding used, but 12 or 15 bushels per week represent the approxi-
mate amount obtained. As borax costs from 5 to 6 cents per pound
in 100-pound lots in Washington, it will make the cost of the borax
practically 1 cent per horse per day. And if calcined colemanite is
purchased in large shipments the cost should be considerably less.

26 BULLETIN 118, U. S. DEPARTMENT OF AGEICULTUEE.

LITERATURE CITED.

American Public Health Association, Laboratory Section.

1912. Standard Methods for the Exniiiination of Water and Sewage. 2d
ed. New York. Amer. Pub. Health Assoc, 144 p. (Cover title:
Standard Methods of Water Analysis. A. P. H. A. 1912.)

FoLiN, Otto, and Macallum, A. B.

1912. On the determination of ammonia in urine. In Jour. Biol. Chem.,

V. 11, no. 5, p. 523-525, June. See p. 523.
Haselhoff, E.

1913. Landwirtschaftlichen Versuchs. vols. 79 and 80, p. 399.'

1913. Uber die Einwirkung von Borverbindungen auf das PUauzenwachs-

tum. In Landw. Vers-Stat., Bd. 79 u. SO, p. 399-429, pi. 4-7,
1913.
Hebms, W. B.

1910. How to control the common house fly. Cal. State Board of Health

Bui., May 5, no. 2, p. 269-277.
Howard, L. O.

1911. The House Fly — Disease Carrier. New York, Frederick A. Stokes

Co., 312 p., illus. See p. 196 and 197.
Hutchison, R. H.

1914. The migratory habit of house-fly larvte as indicating a favorable

remedial measure. An account of progress. U. S. Dept. Agr., Bui.

14. 11 p. Feb. 28.
Russell, E. J., and Buddin, Walter.

1913. The action of antiseptics in increasing the growth of crops in soil.

In Jour. Soc. Chem. lud., v. 32, No. 24, p. 1136-1142. Dec. 31.
Smith, R. I.

1912. The house fly (Musca domestica). No. Car. Agr. Expt. Sta., Col.

Agr. & Mech. Arts, Ann. Rpt. 34, p. 62-69, figs. 13-14. See p. 64.
Sorensen, S. p. L.

1907. Enzymstudien. In Biochem. Ztschr. Bd. 7, Hft. 1/2, p. 45-101, Dec. 6.
Van Slyke, D. D.

1911. A method for quantitative determination of aliphatic amino groups,
Applications to the study of proteolysis and proteolytic products.
In Jour. Biol. Chem., v. 9, No. 3/4, p. 185-207, May.
Wiley, Harvey W., editor.

1908. Official and provisional methods of analysis, Association of Official

Agricultural Chemists. U. S. Dept. Agr., Bur. Chem., Bui. J07
rev. 272 p.

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BULLETIN OF THE

No. 124

Contribution from the Bureau of Entomology, L. O. Howard, Chiel

August 28. 1914.

THE ALFALFA CATERPILLAR.

By V. L. WiLDERMUTH,

Ento)iiological Assistant, Cereal and Forage Insect Investigations.
INTRODUCTION.

The alfalfa biitterflj^, Eurymvs cvrytheme Boiscl. (fig. 1), is one
of the most beautiful and interesting of the group of butterflies
known as " the yellows " ; beautiful because of its golden and orange
colors which contrast so conspicuously with the bright green of
alfalfa fields, and in-
teresting because of
the wide individual
variation, extending
from the white or al-
bino forms to those
that are deep or-
ange. To the al-
falfa grower in the
Southwest, however,
its chief interest lies
in the great destruc-
tiveness of the larvse
(fig. 2.) One seeing
the yellow butter-
flies darting here
and there over a green alfalfa field would hardly suspect that a few
weeks hence they would cause the same field to appear as brown,
dead stubble. Yet this is what happens nearly every year to a
greater or less degree in the Imperial Valley of California and in
the Salt River Valley of Arizona.

It was not until 1910 that this butterfly was known to entomolo-
gists as a serious pest. Previous to that time reports received from

Note. — This bulletin is especially applicable to the Southwest, where the alfalfa catei"-
pillar occurs in destructive numbers in irrigated alfalfa fields.

48305°— Bull. 124—14 1

Pig. 1. — The alfalfa caterpillar (Eurymus eunjtheme) ; Fe-
male in the adult, or butterfly stage. One-half enlarged.
(Author's illustration.)

2 BULLETIN 124, U. S, DEPARTMENT OF AGRICULTURE.

the Southwest, placing on this species the blame for injury to alfalfa,
were doubted. In the spring of that year, however, the writer was
detailed to investigate these reports in the Imperial Valley and
discover whether the butterflies bore any relation to the destruction
of alfalfa by a " green worm." His observations showed that the
accusations were well founded, for in July, 1910, the butterflies were
seen to lay the eggs that hatched into the green larvue which ate up
the alfalfa crop, causing a loss of thousands of dollars.

At the end of the first year's investigation, experiments and ob-
servations had been completed which were thought to be of immediate
benefit to the ranchers in controlling the pest, and a preliminary
report v\'as made and published as Circular 133 of the Bureau of
Entomology. During the three years subsequent to this preliminary

Fig. 2. — The alfalfa caterpillar : Full-srown larva. Enlarged about three diameters.

(Original. )

investigation the writer and others have made a more exhaustive
study of the species, its habits, and natural or artificial methods of
control, and the object of this bulletin is to record these observations
as they have been interpreted.

GENERAL DISTRIBUTION.

According to Scudder ^ this insect is well distributed over the
United States, but is found in its greatest numbers in the Mississip.pi
Valley (see map, fig. 3) and to the westward. In only a few cases
does it appear east of the Allegheny Mountains, but its range ex-
tends northward into Canada, even as far as Hudson Bay. In 1911
Mr. R. A. Vickery made observations on the species at Brownsville,
Tex., thereby considerably extending the southern range from that
included in Scudder's map. In past years the species has been espe-
cially abundant throughout the alfalfa -growing sections where irri-
gation is extensively developed.

1 Scudder, S. H. The Butterflies of the Eastern United States and Canada, v. 2, Cam-
bridge, 1889, pp. 1131-1132.

THE ALFALFA CATERPILLAR.

ECONOMIC HISTORY OUTSIDE THE BORDERS OF ARIZONA AND

CALIFORNIA.

In regions outside of Arizona and California this species has at
various times been suspected, both by agents of the Bureau of Ento-
mology and others, of doing more or less injury to alfalfa. In 1906
a correspondent of the Department of Agriculture reported the cater-
pillars as infesting lucerne fields in Brigham County, Wyo. In
the same j^ear another correspondent, writing from Dell, Oreg.,
reported the butterflies in " countless thousands playing on the
alfalfa blossoms."

In 1909 Mr. C. N. Ainslie found eggs and larvae on alfalfa at
Springer, N. Mex., but not in sufficient numbers to be doing any ap-
parent damage. In July, 1913, on nearly the same ground, the writer
found larvse quite abundant. It is apparent that the reason Mr.
Ainslie did not find

m^

m

Fig.

-Map showing distribution of the alfalfa caterpillar.
(Original.)

them in numbers

was the lateness of

the season. In the

same year, 1909, Mr.

E. O. G. Kelly, at

Wellington, Kans.,

reported the larvae as

rather numerous on

alfalfa plants and

feeding freely ; and

the following year,

at the same place,

Messrs. T. H. Parks

and H. T. Osborn observed the larvee feeding upon alfalfa, and reared

parasites therefrom.

In 1910 Mr. R. A. Vickery, at Brownsville, Tex., reported the
species as being abundant in the alfalfa fields as late as November.
He states: " These larvse are the most numerous and injurious of the
several species of caterpillars that are injuring alfalfa now."

In the summer of 1911 the species was found in a number of locali-
ties, and reported by diiferent members of the Bureau of Entomology
as injuring alfalfa at the following places: Cokeville, Wyo., Idaho
Falls and Blackfoot, Idaho (T. H. Parks) ; Ely, Nev. (C. N.
Ainslie). In July, 1911, Prof. S. B. Doten, of the Nevada Agricul-
tural College, received from The H. F. Dangberg Land & Live
Stock Co., JNIinden, Nev., a letter reporting damage from this worm,
an extract of which follows: "We are this day mailing you imder
separate cover a species of worm which at the present time is doing
a great deal of damage in our alfalfa fields. They seem to congre-

4 BULLETIN 124, U. S. DEPARTMENT OF AGRICULTURE.

gate on different parts of the field, and wherever they are the crops
are totall}^ destroyed." The same month Mr. Frank C. Jones, of
Gardnersville, Nev., reported : " The caterpillar of the yellow butter-
fly is seriously damaging the alfalfa fields of Carson Valley. It
seems to develop most abundantly about the time of the first cutting
and feeds on the young shoots, retarding the growth perhaps two
weeks."

During the season of 1913 the species was reported by Mr. E. H.
Gibson as doing slight damage at Jackson and Nashville, Tenn., and
at Greenwood, Miss. Here the butterflies were abroad from early
April until late November and, while everywhere present, never
seemed to do a great amount of damage. Mr. W. H. Larrimer, also
working at Nashville, reported larvae in considerable numbers.

ECONOMIC HISTORY IN CALIFORNIA AND ARIZONA.

It was Henry Edwards ^ who, in 1877, reported the occurrence at
various times of what since has proved to be one of the many color
forms of this species. No account can be found in w^hich he treats
the species as of economic importance, but he says : " This * * * is
an abundant insect in clover and alfalfa fields from July to Septem-
ber," thus intimating that its numbers might be great enough to
cause damage. Most of his records were for California.

In 1899 Prof. T. D. A. Cockerell,^ in studying the insects of the
Salt River Valley of Arizona, noted the abundance of these butter-
flies, but did not stress the probabilit}^ of damage to alfalfa. He
says: "I never saw these butterflies so extraordinarily abundant as
they were last October at Phoenix. * * * These caterpillars be-
ing very numerous must eat a great many leaves and so reduce the
crop, but it is probable that their ravages w^ould not be very notice-
able under favorable conditions of moisture and temperature. At all
events, it is not practicable to take any measures against them." We
have here the first record of the insect as actually destructive to
alfalfa.

It would seem that after this, as irrigation in the warm valleys of
southern Arizona and southern California began to be more highly
developed and alfalfa became a more important crop, the damage
became more noticeable each year. In 1907 Mr. Geo. G. Carr, writ-
ing to the Department of Agriculture from Hanford, Cal., reports
considerable damage to alfalfa. An extract from his letter follows:

1 Edwards, Henry. Pacific Coast Lepidoptera, No. 24. Notes on the genus Colias, with
descriptions of some apparently new forms. In Proc. Cal. Acad. Sci., v. 7, p. 4, Feb. 5,
1877.

- Cockerell, T. D. A. Some insect posts of Salt River Valley and the remedies for them :
Ariz. Expt. Sta. Bui. 32, p. 286-288, Dec, 1899.

j|. 124, U. S. Dept of Agricultur

Plate I.

Fig. 1 .—Alfalfa Plants Stripped of Leaves by Alfalfa Caterpillars.

(Original.^

Fig. 2.— Herding Turkeys as a Method of Reducing the Numbers of
Destructive Insects. (Original.)

Fig. 3.— Field Showing Improper Cutting. The Alfalfa Caterpillar
Thrives in the Long Stubble. (Original.)

THE ALFALFA CATERPILLAR.

THE ALFALFA CATERPILLAR, 5

As to the "cutworms," they result from the yellow butterfly, which is often
noticed in the alfalfa fields in this valley. The butterfly lays an egg which
hatches into the so-called " cutworm " [fig. 2] ; the latter goes into the chrysalis
state [fig. 6], which eventually results in another butterfiy. Seemingly there
are several crops of worms which hatch in one season. Whereas we have no-
ticed these worms and butterflies in moderate numbers for years, yet never be-
fore have they attained the present great numbers.

In the fall of the year 1909, after a severe outbreak in the Imperial
Valley of California during the summer, Mr. J. A. Walton, the
owner of a large ranch in that valley, appealed to the Secretary of
Agriculture for methods of handling the pest. Mr. W. E. Packard,
of the California Experiment Station, reports that the worms are*
often quite numerous during certain years and cause more or less
damage in the Sacramento Valley, and in the irrigated alfalfa
regions of south-central California. Several fields that came under
the writer's observation in 1910 made an entire failure of the third
crop, while many others suffered a 40 to 00' per cent loss in a single
hay crop, so that the damage for the year could be conservatively
estimated at more than $500,000. (See PI. I, fig. 1.) During that
year (1910) there was also considerable damage in the Salt River
Valley of Arizona, but compared with the damage in the Imperial
Valley it was slight. In fact, as is explained in later paragraphs,
injury was rarely as severe in any other locality as in the Imperial
Valley.

During 1911 the bureau was unable to make any studies in the
Imperial Valley, but Mr. Packard, who was continually on the
ground, told the writer in the fall of that year that little damage
was accomplished, the larvse never being present in great numbers.
As noted in a separate paragraph, the destruction of the larvse in-
wholesale numbers the summer before by an apparently contagious
disease had so checked the species that it was unable to make any
headway during that season, and, in fact, as will be seen later, it
required two years to readjust itself to conditions.

Throughout the season of 1911, during the writer's absence, Mr.
E. G. Smyth, in the Salt River Valley, noted that while there was
some damage the species was not numerous enough at any time to
necessitate protective measures against it.

In 1912 the writer was again located in the Salt River Valley, and
that year, although considerable damage was done by the alfalfa
caterpillar, the work of the disease just referred to and of parasites
was able to keep the species pretty well within bounds, so that only
an occasional field was seriously damaged. The following quotations
are from the writer's own field notes :

July 10, 1912: Butterflies are very numerous at this time and in many fields
are actively depositing eggs.

6 BULLETIN 124, U. S. DEPAETMENT OF AGEICULTUEE.

July 22: Butterflies ;ire very numerous now, filling the air everywhere. They
are even flying around over town in great numbers. Over an alfalfa field north
of town they are simply swarming. Millions of them present over the blooming
alfalfa where they are feeding. A field just across the road that had been
recently cut had the alfalfa covered with eggs. These are adults of the third
generation.

Aug. 1 : Eurymus larvse are very abundant now and in a few fields beginning
to do considerable damage. On Mr. Aepli's farm 1 mile south of town the cater-
pillars were exceptionally numerous and damage considerable. However,
Mr. Aepli cut his crop of hay and stopped their work by disking. There were
257 larvae to the square yard counted in this field.

In the Imperial Valley in 1912 the fourth hay crop, about August
1, was nearlj^ one-third lessened by the feeding of the caterpillars,
but the damage, although heavier tlian in the previous year, in no
way compared with that of IDIO or 1913. E>airing July, 1913, Mr.
Walter Packard wrote to the author, telling him of a great outbreak
around El Centro and suggesting that something should be done at
once, as practically all of the third crop had been destroyed. As
the writer was in northern New Mexico, engaged on other work, Mr.
R. N. Wilson was instructed to proceed to Imperial Valley and in-
vestigate the outbreak. Upon his arrival there he found the damage
to be very heavy, but over for the J^ear, as the species had again been
checked by the disease. The conditions are best told in his original
field notes, which follow:

El Centro, July 14, 1913: Some of the fields [alfalfa] were visited this
morning, and it immediately became obvious that if the bacterial disease is as
prevalent in all of the fields in the valley as in those visited this morning
it is now too late to try cultural methods, brush dragging, disking, etc., as
most of the larvte are dead. I am told that last week was very warm during
the entire week and that the humidity was high. This was probably just
the right condition for the disease to spread, and hence the cause of the death
of millions of the larvse. Many of the fields about El Centro have been cut
recently and so show nothing now as to Eurymus conditions ; many are
also being pastured, and in these the caterpillar attack is slight. In some
fields which have not been either pastured or cut the damage is considerable,
but very few healthy larvse or pup?e can be found at present. Butterflies are
numerous everywhere, and in some fields they rise in clouds before the sweep-
net. That the damage from larviie to the present crop is about over is almost
certain. * * * A few farmers cut the crop after it had been stripped by larvte,
and the hay was of such poor quality that it was not even gathered. Much of the
hay that was gathered was of such poor quality and some of it was so foul
with diseased larvse that it was of little value.

On July 16 Mr. Packard said that he noticed the " worms " in some num-
bers in the second crop at cutting time, about the last of May. The real
outbreak came iu July, however, when the third generation of worms began
to eat the third crop of alfalfa. He noticed the bacterial disease in the fields
about the first week in July, when a large amount of damage had already been
done by the larvse, but the disease did not become widespread or really effec-
tive until after the hot, humid weather of last week.

THE ALFALFA CATERPILLAR. 7

During the season of 1913 in Arizona the outbreak was heavier
in the Salt River Valley than it has been for several j^ears — at least
the heaviest since the bureau began its investigations four years ago.
The report of the outbreak for this year is taken from the notes of
Messrs. R. N. and T. Scott Wilson, both of v^hom were located at
Tempe, in the Salt River Valley, this past year. The greatest amount
of damage was done to the fourth crop, although the third crop was
considerably reduced. The species reached destructive numbers in
the eastern part of the valley, especially in the vicinity of Chandler,
earlier than in other parts, so that the third crop was considerably
damaged and in some fields totally destroyed. On July 22 Mr. T.
Scott Wilson reported considerable damage to a field on Mr. Knep-
jDer's ranch, and stated that in large spots, perhaps as large as 50
to 100 yards across, the alfalfa was completely defoliated. On July

29 the same observer states : " Mr. Lang's field, 3 miles north of
Chandler, shows more damage than any other field I have seen this
year. * * * The entire field is damaged, but on spots where the
land is rather poor the alfalfa did not grow as rapidly as in other
places, and after irrigation it came up quickly and at this tender
stage the worms attacked it, completely stripping it of leaves."
Mr. R. N. Wilson had previous to this, on July 25, made a similar
but more general note in which he says : " The butterflies are now
very numerous, and the larvse have stripped large patches in several
fields. * * * The most serious damage began in the central
part of the valley about a week or two weeks later than that de-
scribed in the foregoing notes and was much more severe. On July

30 Mr. T. Scott Wilson reported very serious damage C)| miles south
of Tempe. This field had about 25 to 50 per cent of the alfalfa de-
stroyed." Then, on August 7 : " In Mr. Harmon's field, 1^ miles south
of Tempe, there are a great many pupae and larvse. The alfalfa is
almost completely bare of leaves." And on the same date he noted
that Mr. Olsons's alfalfa in an 80-acre field, 1 mile south of town,
was almost destroyed. Of course he meant the crop then present.
On August 14 he mentions seven different ranches that had almost
the entire fourth crop destroyed by Eurymus. A day later Mr. Wil-
son visited several fields south of Phoenix and found the fourth crop
here completely defoliated. It is thus seen that the damage ran into
thousands of dollars just to this one crop alone. One can hardly
anticipate exactly what would have been the resulting damage had
these caterpillars gone on unmolested and produced another genera-
tion of butterflies. Fortunately, however, the disease already men-
tioned appeared at this time and prevented a large percentage, pos-
sibly 90 to 95 per cent, from ever reaching the pupal stage.

We thus have a history of the several outbreaks during the last few
years in these two larger valleys of southern Arizona and California.

8 BULLETIN 124, U. S. DEPARTMENT OF AGRICULTURE.

There has also been damage in a smaller way, but just as miportant
to the individual farmer, in other valleys of these States. In the
Yuma Valley, near the town by that name, both the writer and Mr.
R. N. Wilson have noted the occurrence of the caterpillars in de-
structive numbers, and in the Buckeye Valley they have made similar
observations. Mr. Long reported serious damage in the Buckeye
Valley, and in 1913, on the Wessex ranch 2 miles Avest of the town
of Buckeye, Eurymus larvae entirely stripped a 2Q-acre field, reduc-
ing the alfalfa to mere stubble. In the Gila River Valley, between
Thatcher and Safford, Ariz., Mr. R. E. L. Wixon, a deputy State
nursery inspector, reports occasional devastation and often entire
fields destroyed.

In California Mr. T. D. Urbahns has at various times during 1913
reported outbreaks and very serious damage at several towns in
the San Joaquin Valley. We quote the following from his notes:
July 9, Corcoran: "Considerable injury where crojDs were left in
field too long." September 13, Tulare : " Farmers generally re-
ported heavy loss to their alfalfa crops from the ' alfalfa worm,'
and on some fields the alfalfa was completely destroyed in July,
then resuming its growth after the pests had subsided from natural
control." September 14. Fresno : " ^\niile out a short distance north
of town I observed fields yellow with butterflies. The leaves were
nearly all badly eaten by the larvse, of which many were still present."
September 15, Dos Palos : " Larvae present in moderate numbers, but
causing much injury." September 16, Merced: "A 10-acre field of
alfalfa south of town literally covered by larvae and adults. Stems
had been stripped of their leaves." September 17, Modesto : " AVest
of toAvn farmers consider the alfalfa worm a serious pest to their
midsummer crops in July and August. Adults and larvae were still
present in large numbers."

At Indio, in the Coachella Valley, Mr. Bruce Drummond, of the
Bureau of Plant Industry, has informed the author that considerable
damage is done by these caterpillars and that at times it becomes
quite severe.

It is thus seen that what was once considered merely a thing of
beauty has now become one of the worst enemies to alfalfa culture,
causing betweeA $500,000 and $1,000,000 of damage annually to this
crop in these southwestern sections alone. That the energetic and
up-to-date farmer can greatly reduce and at times totally eliminate
this damage is to be shown in the following pages.

DESCRIPTION.

All stages of Eurymus mtrytheme have been fully described by
Edwards and Scudder, and since this paper is purely economic in
purpose, no detailed description will be given, but instead a brief

THE ALFALFA CATERPILLAR.

9

Fig. 4. — The alfalfa caterpillar : Male in the
adult, or butterfly, stage. One-half enlarged.
(Author's illustration.)

outline, such as would enable the casual observer to recognize the
different forms.

THE ADULT.

The typical wing color of the adults is an orange-yellow with a
black outer border above, and a lighter yellow color on the under-
side with the black outer
border wanting. There is a
black discal spot in each of
the four wings and a double
discal spot of orange in each
hind wing. The lower sur-
face of the wing is the one
noticed when the butterfly is
at rest. The male (fig. 4.)
may be distinguished from
the female (fig. 1) by the
fact that the outer border of
the wings is solid black in
the former, but broken by a
line of yellow dots in the latter. A white or albino female form is
frequently found with other color markings, the same as in the
yellow form. The wing exj^anse is about 2 inches.

EGG.

The egg (fig. 5) is small, only 0.06 of an inch long, with from 18
to 20 slightly raised longitudinal ridges or ribs broken by cross lines.
It is elongated, white when laid, but turning red-
dish brown after the second day, and is deposited
upright, with the basal end attached usually to the
mt'ii upper surface of the leaf.

LARVA.

Fig. 5.— The alfalfa The newly hatched larva is a tiny, dark brown,
caterpillar: Egg, cylindrical object which soon after feeding takes
^Redrawn from OH a gTceu coloT. Growth is rapid and the larva
Scudder.) (fig_ g), after having shed its skin or molted four
times, is a little more than an inch in length and is of a dark grass-
green color, with a white stripe on each side of the body, through
which runs a crimson line. Beneath this stripe on each segment or
division of the body is a black spot. There is often an intermediate,
narrower, broken, and less distinct white line just above each of
the lateral lines. This may be wanting. In some specimens a
black or dark green median dorsal line is also present.
48305°— Bull. 124—14 2

10

BULLETIN 124, U. S. DEPAETMENT OF AGRICULTURE.

PUPA.

The ]oiipa (fig. 6) is yellowish green, with a conspicuous row of
black dots just within the margin of each wing pad and three black
dots on each side of the abdomen. It is free, having no cocoon, and
is founds head up, attached closely by the posterior end to an alfalfa
stalk or other support, with the anterior end hang-
ing loosely in a threadlike swing which is joined to
the same support.

LIFE HISTORY AND HABITS.

The complete life cycle for this insect averages
about 38 days for all generations, the minimum
length being about 26 days for the third brood and
the maximum 64 daj^s for the first brood. (See
Table III.) The time occupied by the different
stages is as follows: Egg, 6 days; larva, 24 days;
pupa, 7 days, and a resting and feeding period of
1 day following emergence of adults during which
copulation takes place. Males usually complete the
developmental period several days sooner than the
females, and thus pass a longer period between
emergence and copulation. Mr. W. H. Larrimer, working at Nash-
ville, Tenn., made some interesting records on the life-cycle periods,
as shown in Table I. It will be noted that these records were all
made during the months of June and July and correspond with the
tables for Arizona showing records made during weather of medium
temperature.

Table I. — Rearing records for the alfalfa caterpillar, Nashville, Tenn., 1913.

Fig. 6. — The alfalfa
caterpillar : Chrys-
alis, or pupa.
(Author's illustra-
tion.)

Egg laid.

hatched.

Egg
stage.

Larva
pupated.

Larval

stage.

Adult
emerged.

Pupal

stage.

Food plant.

Days.

Days.

Days.

June

41

June 7

3

June 26

19

Julv 2

16

Medicago sativa.

4>

7

3

July 1

24

8

7

Do.

4

7

3

3

26

10

7

Do.

27

30

3

16

16

23

7

Do.

27

30

3

16

16

23

7

Do.

July

21

July .5

3

22

17

29

7

Do.

21

5

3

23

18

29

6

Do.

21

5

3

28

23

Aug. 1

5

Do.

21

5

3

30

25

6

7

Do.

161

19

3

Aug. 2

14

8

6

Trifolium hybridum.

27

30

3

13

14

20

7

Trifolium repens.

27

30

3

14

15

21

6

Do.

27

30

3

11

12

17

6

Vicia sativa.

27

30

3

12

13

17

5

Do.

27

30

3

11

12

17

6

Do.

27

30

3

15

16

21

fi

Pisum sativum.

27

30

3

15

21

21

6

Glycine hispida.

1

4

3

July 28

24

2

6

Trifolium pratense.

' Reared under same conditions of light, moisture, temperature, and food supply.

Days.

Average length of egg stage 3

Average length of larval stage 18

Average length of pupal stage 6^

THE ALFALFA CATEEPILLAR. 11

EGG STAGE.

The egg stage varies under ordinary temperatures from 2 to 15
days, the normal period being about 6 days. The length of the egg
stage as observed for the six generations during the season of 1912
is as follows : First generation, 14rh days ; second generation, 4 days ;
third generation, 3 days; fourth generation, 3^ days; fifth genera-
tion, 3| days; sixth generation, 5 days. In the summer of 1913
Mr. T. Scott Wilson had eggs under observation which hatched in
two days during the month of August, but with an average mean
temperature of 87° F., and this same season Mr. E. H. Gibson, at
Nashville, Tenn., obserA^ed eggs to hatch in an equally short time,
with an average mean, temperature of 76° F. Mr. Gibson gathered
three eggs on June 5 and noted that the time of oviposition was 3
p. m. He placed these in a box, and at 3 p. m., June 7, the larva?
were found emerging from eggshells. Thus the remarkably short
period of 48 hours elapsed from oviposition to hatching.

The eggs are deposited upright, singly, on the upper surface of
fresh, green alfalfa leaves. AVhen first deposited they are white in
color, but change in a few hours to reddish brown. Just before
hatching the upper end becomes light colored or nearly transparent,
and the caterpillar gnaws its wa}^ out.

LARVAL, OR CATERPILLAR, STAGE.

Upon hatching, the larva makes its first meal on the eggshells,
often consuming the whole shell. It then feeds upon the leaf, at
first gnawing out xery small, tiny spots; but rapidly its appetite in-
creases, and it is soon consuming the entire leaf, veins and all. Ob-
servations made by the writer and by Mr. Watts, a former agent of
this bureau, show that one larva consumes about 25 to 30 leaves dur-
ing its lifetime. Its growth increases just as fast as its appetite, and
often within 12 days the larva is full grown, having cast its skin, or
molted, four times and having passed through five instars, or periods
between molts, and increased from less than one-tenth inch to
nearly li inches in length. The duration of these various instars
(see Table II) is influenced greatly by temperature, and during
cold or cool weather they are protracted considerably, so that often
the complete larval period will cover a month or even more, the
general average period for all temperatures being about 24 days.

The larva in feeding stretches itself along an alfalfa stalk and is
often rather hard to find, the green color of its body proving to be
exactly the same shade as the alfalfa upon which it is feeding.

12

BULLETIN 124, U. S. DEPARTMENT OF AGRICULTURE.

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a : :

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co-^coo^c^'-ootn

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COCOCNCNlMCSKNC^

rH C4 CO "^ O O t^ 00 C-

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sg

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tt

THE ALFALFA CATERPILLAR. 13

PUPAL, OR CHRYSALIS, STAGE.

As has been stated before, the pupaj are found hanging, head up,
attached to alfalfa or other stems, and as their color blends with
their environment they are often hard to see and will be overlooked
unless searched for. Often, too, instead of pupating on a bare stem
the larvae will crawl to a leafy stem and pupate there, thus protect-
ing themselves still further from their enemies and from the rays of
the sun. The average length of the pupal period for ordinary field
temperatures is about 7 to 10 days, but varies considerably with the
temperature. Records made by the writer at Tempe, Ariz., from
March to September, 1912, showed a variation of from 5 to 10 days,
and records made at the same place in 1913 showed a variation of
from 5 to 7 days, while Mr. W. H. Larrimer, at Nashville, Tenn.,
secured records during the summer of 1913, from July 2 to August
21, in which the pupal stage varied from 5 to 7 days, averaging for
18 specimens GJ days. There is no doubt that the pupal period
may be lengthened to 12 or 15 days, or even more, if the temperature
is low enough.

ADULT, OR BUTTERFLY, STAGE.

The process of emergence from the pupa is one of short duration
and usually occurs early on a bright morning. The butterfly crawls
up a stalk, soon spreads and dries its wings, and is off looking for
bloom upon which to feed. Copulation often takes place within a
day or sometimes on the same day, and the female begins ovipositing
on the day following. A large number of eggs is usually laid by
one female. In the Southwest the number per individual is greater
during spring and fall than during the extreme hot weather. At
Tempe never more than 200 eggs were recorded for one female, the
number often being as low as 50. At Tempe, also, the total number
was often deposited in a single day, while specimens sent to New
Hampshire deposited as many as 500 during a laying period of 11
days. This shows the relation of temperature to egg production.

The sending of gravid female moths from Tempe, Ariz., to Prof.
John H. Gerould, at Hanover, N. H., a railroad trip of several days,
was a matter of interest and shows well the hardiness of the butter-
flies. The butterflies were placed inside a tin box securely lined with
moist blotting paper, and the box was then wrapped carefully and
mailed. Vigorous specimens were secured and only a few to a box.
While not every attempt was successful, a great many were so.
Through the kindness of Prof. Gerould I quote from a letter written
October 7, 1913:

The third female from Arizona produced from one laying of eggs 214 males
and 206 orange-yellow females. She was mailed at Tempe on June 6 and re-

14 BULLETIN 124, U. S. DEPARTMENT OF AGEICULTUKE.

ceived at Hanover in strong active condition on June 10. She began to lay on
June 11 and continued until June 22. Her 420 adult offspring represent only
a part of her caterpillar progeny, for, besides the loss through disease and acci-
dent, 15 pupte succumbed to excessive cold and other unfavorable conditions
In a refrigerator while undergoing an experiment to determine the effect
of cold upon color. Probably 500 eggs were laid.

The proportion of males to females in Arizona is about 2 to 1,
but Gerould, in New Hampshire, finds them about equal. In the
field at Tempe one will always be impressed with the superabundance
of males. This difference in the proportion of the sexes as between
Arizona and New Hampshire is probably due to the fact that in
Arizona the intestinal disease kills a large number of the larvse ; and
since males develop a few days sooner than females, it is likely
that the majority of the larvse killed would have developed into
females, while those escaping the disease become males. In New
Hampshire Prof. Gerould is often able to rear over 90 per cent from
egg to adult in confinement, while at Tempe it is rare that 25 per
cent of the eggs are reared. In a blooming alfalfa field the per-
centage of males to females is still higher, owing to the fact that fe-
males after feeding and mating leave this older alfalfa to seek new
growth. In searching out this tender growth for egg deposition it
seems as if they knew that if their eggs were laid on the older
alfalfa it might be cut before the larvse could mature. One can tell
at a glance an ovipositing female. She has a hesitating flight and at
intervals will drop down for a moment on an alfalfa leaf and, de-
positing an egg, will flutter on, soon repeating the operation and de-
positing as many as four or five eggs per minute.

Among the yellow butterflies in a field one notices many white or
albino forms. These are of the same species as the yellow ones
and, according to Prof. Gerould,^ are merely color phases, as he has
shown to be the case in Eurymus jjhilodice (Godart).

FEEDING HABITS OF THE BUTTERFLIES.

The butterflies of Eurymus eury theme feed upon nectar from the
blossoms of a great many plants. Over a blooming alfalfa field one
can often see them by the millions, visiting the blossoms and extract-
ing the nectar therefrom. This habit has occasioned many remarks,
farmers quite often being under the impression that these butterflies
were producing some direct results upon the growth of the alfalfa
crop. The b<?e-keeping farmer usually insists that the}^ are robbing
his bees by taking nectar that belongs to them. In Circular 133 of
the Bureau of Entomology, published in 1910, the writer ventured
the remark, since he had witnessed the tripping of the pollen trigger

1 Gerould, J. H. The inheritance of polymorphism and sex in Colias pJiilodice. Amer.
Nat., V. 45, p. 257-283, May, 1911.

THE ALFALFA CATEEPILLAE. 15

of alfalfa bloom by this butterfly, that possibly its feeding habits
might be of some benefit in assisting pollination. As this statement
occasioned some comment, further observations were made upon the
butterflies during three consecutive years, but not another instance
of tripping was noted. It seems, therefore, that in the cases ob-
served, the trippings were effected accidentally by the feet. As
these instances are probably exceptional it is not likely that the but-
terflies exert any material influence on seed production. However,
the relation of bees and alfalfa to butterflies and alfalfa seems to be
a complex one. Hermann Miiller,^ in 1873, came to the conclusion
that butterflies probably effect explosion and cross-fertilization,
while C. V. Piper ,2 in 1909, in his Report of the Committee on Breed-
ing Forage Crops, gives the records from a considerable number of
well-laiown plant breeders, no two of whom seem to agree as to the
exact relation of butterflies to alfalfa pollination, but the majority
of whom think that the butterflies exert no influence.^ Whether the
butterflies rob honeybees of their just food is a question. Prof.
Cockerell* states, in 1899, that * * * "butterflies, sucking the
nectar, but making no honey, must interfere with the success of the
bees, especially when they become very numerous." As mentioned
above, this robbing of the bees by butterflies is a common belief
among beekeepers and has been suggested to the author many times.

NUMBER OF GENERATIONS.

Mr. W. H. Edwards^ reports two broods of this species in the
mountains of northern Colorado, the adults of which appear in
June and again in the latter part of July and in August. In Ne-
braska and Illinois, according to the same author, three broods are
recorded, while in the lowlands of California he reports the insect
as being triple or quadruple brooded. Mr. J. Boll," in 1880, reports
four broods in Texas, and this, too, during a short season, for he

1 Miiller, Hermann. Die Befruchtung der Blumen durch Insekten, Leipzig, 1873, p.
228-229.

- Piper, C. v. Report of the committee for breeding forage crops. Alfalfa and its
improvement by breeding. Amer. Breeders' Assoc, v. 5, 1909, p. 94-115.

2 Since this nianuscript was submitted for publication. Bulletin No. 75 of this depart-
ment, dated Apr. 8, 1914, treating of Alfalfa Seed Production ; Pollination Studios, by
Prof. C. V. Piper and his assistants, has been published.

In this document it is shown that tripping of alfalfa flowers may be automatic as well
as effected by Insects or other external agents. The authors state that this automatic
tripping takes place more frequently in hot sunshine, although humidity is doubtless a
factor. Also the statement is made that this automatic tripping, with consequent self-
pollination, probably results in the setting of as many pods as does tripping by insect
visitors, at least in the West. — F. M. W.

* Cockerell, T. D. A. Some insect pests of Salt River Valley and the remedies for them.
Ariz. Agr. Expt. Sta. Bui. 32, p. 273-295, Dec, 1899.

5 Edwards, W. H. The Butterflies of North America, second series, Boston, 1884,
Colias IV.

"Boll, .1. Ueber Dimorphisnms und Variation einiger Schmetterlinge Nord-Amerikas.
Deut. Ent. Ztschr., Bd. 24, Heft 2, p. 241-248, 1880.

16

BULLETIN 124, U. S. DEPARTMENT OF AGRICULTUEE.

states that the species eestivates during the summer months from
June to November.

In the j^ear 1910, in the Imperial Valley of California, there were
four distinct generations up to July 15. The fourth generation, hoAV-
ever, was almost entirely exterminated by the disease before men-
tioned, and, following this, later generations became so largely con-
fused that it was impossible to separate them, since, unfortunately, no
series of generation cages were then in use for this purpose. The
first generation in 1913 covered the period from INIarch 15 to April
30 ; the second generation from May 1 to May 28 ; the third genera-
tion from May 28 to June 20; and the fourth generation from June
20 to July 15. It seems quite probable that there were at least
three generations during the rest of the season. As shown in Table
III, during the year 1912, at Tempe, Ariz., there were six genera-
tions, adults of hibernating forms appearing in March and adults
of the fifth generation disappearing in October, while a few adults
of the sixth generation appeared during warm periods of the winter
months.

Table III. — Generations of the alfalfa caterpillar, Tempe, Ariz., 1912}

Eggs laid.

Eggs hatched.

O <D

C3
P<

"3
>

3

"3
ft
a
ft .

ft-d
_o o

1

Gen-

1

a=ft

era-
tion.

sl

3
c3

.c-2

"5

4J m

c3

a

s

C3

%

1

1

1

u

fi

;z;

«

!z;

h^

h-1

<

*A

&H

^

<^

1912.

Days.

Bans.

Days.

Days.

°F.

1st. . .

Mar. 24

Many.

/Apr.

7
S

12
31

14\
15f

May

11

34

May 19

8

56

/17 females.
\30 males...

|63.5

2d ...

May 27

36

May

31

36

4

June

IS

IS

Jime 24

0

28

(2 lemales..
tl male

}83.75

3d....

Jiine 25

Many.

Jime

28

Many.

3

July

13

15

July 19

5

23

/3 females..
\2 males". . . .

|S6.5

4th...

Jixly 22

Many.

July

25

Many.

3i

Aug.

12

18

Aug. 19

7

28i

/I female...
\1 male

|S4.5

5th...

Aug. 23

6

Aug.

26

6

3i

Sept.

9

16

Sept. 19

10

29*

/3 remale.s..
\3 males

|-80.0

6th...

Sept. 2S

Many.

Oct.

3

Many.

5

Nov.

IS

45

T

hieseh

ibemated.

64.0

1 The first half of this ta! le does not five duration of time elapsinf; lietween emergence and oviposition.

2 Date hero is the day the last ones issued.

PERIODS AND DURATION OF GENERATIONS.

Days.

First generation, Mar. 24 to May 27 64

Second veneration, May 27 to June 25 29

Third generation, June 25 to July 22 26

Fourth treneration, .lulv 22 to Aug. 23 33

Fifth generation, Aug. 23 to Sept. 28 3Si

Sixth generation. Sept. 2S to pupse in hibernation.

Mr. T. Scott Wilson, working at Tempe, secured records during
the year 1913 of three distinct generations from late March to the
latter part of July, his observations thus corresponding fairly well
with those of the writer during the previous year. The dates of
the three generations were as follows : First brood, March 27 to May
20; second brood, May 20 to June 23; and third brood, June 23 to

THE ALFALFA CATERPILLAR. 17

July 23. Following this the intestinal disease attacked the larvae
so generally that Mr. Wilson found it impossible to continue genera-
tion records. Nevertheless, he states in his field notes that a fourth
generation was out by the latter part of August. We thus see that
there are in the colder sections of the country two generations an-
nually and in the extreme warmer sections at least six and possibly
more generations each year.

FOOD PLANTS.

Alfalfa seems to be the favorite food plant, but there are quite
a number of others. The two buffalo clovers, Trifolium re-flexum
and T. stoloniferum^^ were probably the original native food plants.
For some years the species was thought not to live upon red clover
{T. pratense), but Mr. E. H. Gibson, at Greenwood, ISiiss., and Mr.
W. II. Larrimer, at Nashville, Tenn., proved conclusively that it
does attack red clover. They collected both eggs and larvae from red
clover and reared them to adults. During the summer of 1'913 the
writer collected the larva3 feeding upon few-flowered Psoralea {Psora-
lea tenuiflora) at Koehler, N. Mex., and Mr. Larrimer, at Nashville,
made some interesting experiments, besides those on red clover.
Using larvse that hatched indoors, he reared them from the following
plants that had not already been reported as food plants: Alsike
clover {T. hyhridum)^ soja bean {Glycine hispida), Canadian field
peas {Pisum sativum), and hairy vetch {Vieia sativa). Repeated
attempts to rear them on cowpeas {Vigna sinensis) resulted in fail-
ure. He says : " On hairy vetch they seemed to thrive exceedingly
well and completed their life history in a shorter period than on any
other food plant." In July, 1910, the writer found larvsg feeding
on sweet clover {Melilotus alha), which, strangely enough, they
seemed to prefer to a patch of alfalfa growing close by. Eggs were
observed to be very numerous upon the leaves of the sweet clover
at the same time. Besides alfalfa and the buffalo clovers^ Scudder ^
has recorded Hosackia, ground plum {Astragalus cargacarpus) , and
A. crotalaria' as food plants. The adults visit blooming plants for
nectar, and they have been reported, doubtless erroneously, as feed-
ing upon many of these. The butterfly is known to oviposit on
toothed medicago or bur clover {Medicago hispida). Mr. E. H.
(iribson, at Greenwood, Miss., reported females ovipositing on coffee
weed {Seshan macrocarpa), which they curiously preferred to red
clover growing near by.

1 Scudder, S. H. The Butterflies of the Eastern United States and Canada, v. 2, Cam-
bridge, 1889, p. 1132.

48305°— Bull. 124—14 3

18 BULLETI2SI 124. U. S. DEPAKTMENT OF AGRICULTURE.

HIBERNATION.

According to earlier records by Edwards and those a little later
by Scudder, which treat of the species in its northern rather than
in its sonthem range, the alfalfa caterpillar hibernates as larvfc and
adults, whereas G. H. French,^ in his revised edition of Butterflies
of Eastern United States, reports the species as hibernating as
chrysalids. The writer has observed the species hibernating in all
three forms, if it could really at all times be termed hibernation.
Hibernating chrysalids were found upon weed and alfalfa stems by
the writer at both Tempe, Ariz., and El Centro, Cal., and at Welling-
ton, Kans., Mr, Kelly reported the finding of hibernating pupa3 be-
neath fence rails. Just a few larvae have been collected by sweeping
at various tunes during the winter season at Tempe. During the
last week in January, 1912, a single larva was taken, while in Janu-
ary, 1913, Mr. R. N. Wilson took a third-instar larva less than two
weeks after a very severe cold spell, i. e., severe for the Salt River
Valley, a temperature of 13° F. having been recorded on two suc-
cessive nights. On warm days adults have been observed in flight
several times during the winters when the species was under obser-
vation. In 1910 adults were taken at Tempe early in December, and
Mr. W. E. Packard took them during the third week in December at
El Centro, Cal. In the winter of 1911-12 adults were seen on the
20th of December and again in the middle of January. Larvae have
been collected in January and, pupating within a few weeks, have
issued early in March. Pupse collected in December have issued in
February, but adults have never been noted to deposit eggs during
the month of January. It is thus seen that at times hibernation
amounts to nothing but a prolongation of one of the three stages,
the usual activity for each respective stage being resumed on warm
days that occur during the hibernation period.

According to Boll ^ the species a^stivates in Texas as larvse during
the dry period in summer when the food supply has become ex-
hausted. The writer has never witnessed the aestivation of this spe-
cies in the Southwest. In fact, it has always occurred in most
abundance during the hotest months of the year, notably July and
August. Other bureau records likewise show no report of aestiva-
tion. It seems safe to assume that the change in habit from that
early reported by Boll in Texas is due to recent irrigation of tracts
of land well distributed over the arid regions of the Southwest.
Originally the species had to aestivate during summer when clovers

1 French, G. H. The Butterflies of the Eastern United States. New and rev. ed., Phila-
delphia, 1900, p. 130.

- Boll, J. Ueber Dimorphismus und Variation einiger Schmetterlinge Nord Amerikas.
Deut. Ent. Ztschr., Bd. 24, Heft 2, p. 241-248, 1880.

THE ALFALFA CATERPILLAR. 19

were dried up, but now, in the thrifty-growing alfalfa fields of this
once arid country, it finds a place to continue its activity throughout
the summer, and, as has been mentioned before, it is this very change
that has enabled the species to become the pest that it is to-day.

NATURAL CHECKS TO THE SPECIES.

Were it not for the fact that this species is preyed upon by a great
many natural enemies it would indeed prove a much more serious pest
than it is at the present time. Parasites and predaceous insects,
fungous and bacterial diseases, birds, toads, and even domestic fowls,
all play a large part, toward keeping the species well within bounds
during certain seasons of the year.

In 1889 Scudder ^ said : " Strange to say, not a single parasite
has been reported to attack this common insect." However, the au-
thor and others, during the past three years, have reared as many as
nine parasites from the various stages of this butterfly, and some
of these at times are quite numerous. An example of the extent of
parasitism may be gleaned from the following record of a collection
of 154 pupse made at Tempe, Ariz., on August 26, 1912:

No. of
pupae.

Inf<^sted by chalcid parasites 82

Partially eaten by Heliotliis obsoleta, etc 28

Rotten from intestinal disease 37

Infested by tacbinid parasites 6

Alive and bealtby 1

Total 154

This, of course, was an exceptional collection, but often collec-
tions were made from which as few as 5 per cent of the pupse were
reared to adults. The percentage of parasitism usually reaches the
maximum during the month of August, so that rarely is much dam-
age done by the caterpillar after that time.

PARASITES OF THE EGGS.

Only one egg parasite of Ewrymus eurytheme was found. This is
the very common Tnchogramma mimitum Riley (fig. 7), which is
known as an egg parasite of a great many species of insects. In its
relation to eggs of this species it was first found by Mr. Harry New-
ton, of the Bureau of Entomology, who was working at Tempe,
Ariz., during the summer of 1913. On July 26 he found three eggs
which were very dark in color, and two days later three of the tiny
parasites issued from one of these. Two days previous to Mr. New-
ton's collection Mr. T. Scott Wilson collected 100 eggs. From three

1 Scudder, S. H. The Butterflies of the Eastern United States and Canada, v. 2, Cam-
bridge, 1889, p. 1132.

20

BULLETIN 124, U. S. DEPARTMENT OF AGEICULTURE.

of these parasites issued several days later, or 3 per cent. On July

28 Mr. Newton, encouraged by his first efforts, collected 31 eggs that
appeared to be parasitized. Twenty-six of
these produced, in the course of five days, 76
parasites, or nearly 3 to each egg. Seventeen
freshly laid eggs were exposed to female para-
sites by Mr. Newton on August 1, and on
August 8 eight of these produced 24 adult
parasites, showing the length of the combined
egg, larval, and pupal stages to have been seven
days. Nine failed to be parasitized, and one
produced 5 parasites in six days. On August
16 Mr. Wilson collected 19 eggs, 60 per cent
of which were parasitized.

It is thus seen that this tiny parasite is of
considerable benefit in reducing the numbers of
the alfalfa caterpillar. From the records it
seems that the increase of the parasites from
July to August was quite rapid. The fact that
the life cycle is of so short duration is partially
responsible for this, as it doubtless gives a

chance for two broods of parasites upon the eggs of one generation of

Eurymus.

HYMENOPTEROUS PARASITES OF THE CATERPILLARS AND CHRYSALIDS.

Four species, of hymenopterous parasites of the caterpillars
and chrysalids were found. Specimens of a Limnerium were reared

Fig. 7. — Trie ho gram ma
minutum, a parasite of
the eggs of the alfalfa
butterfly, in act of
oviposition in an egg
of the brown-tail moth
{Euproct is chrysor-
rhwa ). Greatly en-
larged. ( Prom How-
ard and Piske.)

Fig. 8. — Limnerivm n. sp., an icbnenmonid parasite of the alfalfa caterpillar : Adult.
Greatly enlarged. (Original.)

by the author at El Centro, Cal., in 1910, and what is supposedly
the same species was reared in considerable numbers by Mr. L. P.

THE ALFALFA CATERPILLAR,

21

Rockwood at Salt Lake City in the summer of 1913 and has since
been determined by Mr. A. B. Gahan, of this bureau, as Limnenum
n. sp. (fig. 8). Mr. Rockwood found these parasites of material ben-
efit in the suppression of outbreaks in Utah and always reared them
from young and only partially grown larva?. At Salt Lake City,
during the summer of 1913^ he also reared a goodly number of a
small hymenopteron, Apanteles {Protopanteles) ftavicomhe Riley.
This species is gregarious, but was not found to be sufficiently nu-
merous to exert any marked effect upon the abundance of Eurymus.
The common Chalets ovata Say (fig. 9) was first reared from this
species by the writer in 1910, at El Centro. Only one specimen
was secured, but in 1912 the author reared many adults, and in 1913
the Messrs. Wilson reared adults from pupae collected in both Ari-
zona and California.

Pig. 9. — Chalcis ovaia, a parasite of the pupa of the alfalfa caterpillar : a, Pujja ; h, para-
sitized pupa of tussock moth {Hemerocainpa lencostigma) ; c, adult; d, same in profile;
e, pupal exuvium. Enlarged. (From Howard.)

PTEE0MALU8 EURYMI GAHAN.

The three parasites just mentioned are of minor importance, but
the fourth is of great assistance in suppressing outbreaks of the
alfalfa caterpillar. It is a new species, recently described by Mr.
Gahan ^ as Pteromalus eurymi (fig. 10). Mr. H. T. Osborn, at Wel-
lington, Kans., in September, 1910, reared 40 specimens of this spe-
cies from a pupa of Eurymus, but the specimens were put into
alcohol and not determined until November, 1913. When, therefore,
Mr. R. N. Wilson secured a parasitized pupa in December, 1911, and

1 Gahan, A. B. New Hymenoptera from North America. Proc. U. S. Nat. Mus., v. 46,
p. 431-443, 1913. "Pteromalus eurymi, new species," p. 435-436.

22

BULLETIN 124^ U. S. DEPARTMENT OF AGRICULTURE.

reared this parasite, it was believed to be the first rearing record.
During the following summer the parasites were so numerous that
it was hard to understand why they had not been discovered before.
Collections of pupae of Eurymus were made by the writer in August,

Fig. 10. — Pteromalus eurymi, a parasite of piipit> of the alfalfa caterpillar : Adult. Greatly

enlarged. (Ori^nal.)

1912, and showed that 49 per cent were parasitized by this species.
The record follows:

Table IV. — Parasitism of pupw of the alfalfa caterpillar by Pteromalus eurymi.

Date.

Pupae
collected.

Infested
with Per cent
Ptero- infested,
malus.

1912.

Aug. 5

Aug. 14

Aug. 19

Aug. 26

Total and average

65

39

11

154

40
43+
63+
53

49

This insect thus seems to be exerting a larger influence than any
other parasite toward the control of the alfalfa caterpillar.

In 1913 Mr. T. Scott Wilson did not find it nearly so numerous in
the Salt River Valley as was the case the year before. Just why this
was so, it is hard to say. The extremely cold weather during the

THE ALFALFA CATERPILLAR.

23

preceding winter may have killed the hibernating Pteromalus larvse
(fig. 11). In the same year Mr. R. N. Wilson found the species
quite numerous in the Imperial Valley of California. As many as 20
per cent of the Eurymus pupae were parasitized by it.

This parasite seems to be distributed over a considerable area, for,
besides being present in Arizona and California and, as stated, at
Wellington, Kans., it has been reared during the season of 1913 and
found to be quite abundant at Salt Lake City, Utah, by Mr. Rock-
wood, and at Nashville, Tenn., specimens were raised by Mr. Larri-
mer from a single pupa of Eurymus.

It seems almost certain that this parasite winters as a larva with-
in the pupal shell of the host. The first lot collected in a pupa of
the alfalfa caterpillar in December were discovered
as larvae in January and soon thereafter turned to
pupae (fig. 12), issuing as adults in March. The

Fig. 11. — Pteromalus
eurymi: Larva.
Greatly enlarged.
(Original.)

Fig. 12. — Pteromalus
eurymi: Pupa.
Greatly enlarged.
(Original.)

B'IG. 13. — Pteromalus
eurymi: Adults is-
suing from chrys-
alis of alfalfa cat-
erpillar. Enlarged
nearly three diam-
eters. (Original.)

eggs are laid in pupae of Eurymus, from 40 to 114 parasites develop-
ing in one pupa. About 80 to 90 per cent of these are females and
the rest males, and the adults issue from one or more tiny holes in
the pupa of their host. (See fig. 13.)

The combined length of the egg, larval, and pupal stages in the
warmer weather of August is from 12 to 15 days, while the pupal
stage was found to cover 4 days in the month of August and 12
to 15 days in February, the variation being due to differences of
temperature. Thus several generations are possible each season, and
thus, with abundant egg production and high percentage of females,
gives rise to a rapid increase in the number of parasites, so that by
late August the multiplication of the host species is checked.

24

BULLETIN 124, U. S. DEPARTMENT OF AGEICULTUEE.

'^— ^

Fig. 14. — Phorocera claripennis, a parasite of the
alfalfa caterpillar. Adult and enlarged antenna of
same; puparium. Enlarged. (Prom Howard.)

DIPTEROUS PARASITES.

Three tachinid flies, determined by Mr. W. R. Walton, of this
bureau, have been reared from the larvae and pupae of this caterpil-
lar. Phorocera claripennis Macq. (fig. 14) is the most important

of these, its wide dis-
tribution and abundance
of alternate hosts causing
it to be always on hand.
In 1910 at El Centro,
Cal., the writer observed
as many as 15 per cent
of Eurymus larvae with
eggs of this species at-
tached to them ; while in
1913 Mr. T.Scott Wilson,
at Tempe, Ariz., observed
as many as 50 per cent
of larvae with eggs upon
them, and in some cases
there were as many as
five or six to one cater-
pillar. Of course a great many of these eggs are shed in molting,
but a majority of them hatch, and the maggot, entering the Eurymus
larva, kills it in a short time. P. claripennis has been reared from
this species at the following
other places: Salt Lake City,
Utah (E. J. Vosler and L. P.
Rockwood) ; Wellington, Kans.
(H. T. Osborn) ; Greenwood,
Miss. (E. H. Gibson) ; Nash-
ville, Tenn. (W. H. Larrimer).
Three specimens of Frontina
archippivora Will, were reared
from a larva and pupa collected
at El Centro, Cal., by Mr. R. N.
Wilson, and a single specimen of
the same species was reared by
Mr. Rockwood at Salt Lake City,
while at El Centro a single speci-
men of Masicera sp. was reared
by the writer.

Besides these tachinid parasites, another small dipteron was dis-
covered by Mr. T. Scott Wilson to be parasitic upon the pupae. This
Avas a small brown phorid (fig. 15) which has been determined by
Mr. J. R. Malloch as ' Aphiochceta perdita,, a species recently de-

PiG. 15. — AphiochcBta perdita, a phorid
parasite of the pupa of the alfalfa cater-
pillar. Greatly enlarged. (Original.)

THE ALFALFA CATEEPILLAR.

25

scribed by him ^ as new. This is supposedly a new record of habit
for this species, but according to Mr. Wilson it was reared time and
again from pupse which were alive when collected; thus the flies
could not be acting as scavengers, but must have been true parasites.

OTHER INSECT ENEMIES.

Fig. 16. — Bollworm (Heliothis obsoleta), an
enemy of the alfalfa caterpillar. Twice
natural size. (Author's illustration.)

A large green caterpillar, known as the bollworm, Heliothis obso-
leta Fab. (fig. 16), which can be
distinguished from the alfalfa
caterpillar because it is of a
lighter green color, about one-
fourth larger, hairy, and rough
in appearance rather than
smooth, with three black lines
traversing its body lengthwise, is quite prevalent in the Imperial
and Salt River Valleys, and is often mistaken for the alfalfa
caterpillar by many farmers. As observed by the writer, and later
by Mr. T. Scott "Wilson, it was found to do very little damage to al-
falfa, but to be a ravenous enemy of the alfalfa caterpillar, never eat-
ing alfalfa as long as it could find the larvse
or pupse of Eurymus. Messrs. E. O. G. Kelly
and T. H. Parks noted this species at Welling-
ton, Kans., in the summer of 1909, and re-
ported it as being of a predaceous habit.-

The writer observed a bollworm larva to
eat five large larvae of Eurymus during a
single day, and both the writer and Mr. T.
Scott Wilson counted dozens of pupal cases
with the contents eaten out (fig. 17) and
many times with the Heliothis larva still
feeding upon and devouring the pupse. Mr.
Wilson, on July 15, 1913, remarked in his
field notes that " Heliothis was observed in
Fig. 17.— Chrysalis of alfalfa great numbers feeding upon Eurvmus pupse,

caterpillar that has been ^ . ^ '^ ^ i

eaten out by a bollworm. and in a icw mstanccs on Eurymus larvse.
Enlarged about two diam- rpj^g Heliothis makes a hole in the side of

eters. (Original.) i • i

the pupa, through which he puts his head
and eats out the contents of the pupa." The writer has observed the
end of the abdomen eaten off the pupa ; again, an opening would be
made on the side, often the entire side being destroyed.

■1 Malloch, J. R. The insects of the dipterous family Phoridae in the United States
National Museum. Proc. U. S. Nat. Mus., v. 4:j, p. 4.59-400, 1912. "Aphiochwta pcrdita,
new species," p. 459.

- This cannibalistic habit has also bewi observed in Texas by Quaintance ami Rrues.
(U. S. Dept. Agr., Bur. Ent., Bui. 50, p. 79-80, 1905.)

26

BULLETIN 124, U, S. DEPARTMENT OF AGRICULTURE.

The malachiid beetle, Collops vittatus Say (fig. 18), is rather

numerous in the alfalfa fields of Arizona and was suspected of bear-
ing some relation to Eurymus.
Mr. T. Scott Wilson found both
adults and larvae feeding upon
pupse of the alfalfa caterpillar.
He observed as many as 20 beetles
feeding upon as many pupae in a
single day. This beetle seems to
feed upon either live or dead
Eurymus larvae and pupae and does
not appear to have much choice
between the two. It attacks a pupa
or larva and, piercing it, sucks
the juices that exude. In this way
a hole is gradually made in the
host, which, of course, is killed.
Being small, the beetle does not
consume much of its prey, but
wanders off, and the next time it
is hungry it attacks a new pupa or

larva and thus kills many. Larvae were taken in the act of feeding

upon Eurymus pupse, placed in vials, and reared to adult Collops.
Two species of ants, Pogonomyrmex harbatus Smith and Cre-

mastogaster Uneolata Icevius-

cula var. clara Mayr ( ?) were

observed to attack Eurymus

larvae and kill them. Several

species of robber flies have

been observed to catch the

adult butterflies and feed

upon them. The writer took

Prod acanthus milbei'tii

Macq. with a butterfly in its

claws, and Mr. H. E. Smith,

at Koehler, N. Mex., observed

the butterflies being carried

off by Stenopogon pictico7''nis

Loew (fig. 19).

A FUNGOUS ENEMY.

Fig. 18. — Collops vittatus, a beetle that
preys upon the alfalfa caterpillar.
Greatly enlarged. (Original.)

Fig. 19. — Stenopogon picticornis, a robber fly
that preys upon alfalfa butterflies. Not
quite natural size. (From C. N. Ainslie.)

A fungus was found to at-
tack the pupa? in the Salt River Valley in 1912. This is sometimes
quite common, but never abundant, although more prevalent about
August than at other times, probably owing to higher humidity. Dr.

THE ALFALFA CATERPILLAB. 27

Flora W. Patterson, of the Bureau of Plant Industry, has determined
this as a Fusarium. In her letter she says : " The fungus, which bears
strong evidence of being parasitic, has quite filled the body cavity and
is either a Fusarium or Microcera," and states that the majority of
similar fungi are reported upon scale insects. Later she says, " Cul-
tures of the above fungus, parasitic upon Eurynius eurytheme^ have
developed in the most satisfactory manner, and it is probably an
undescribed parasitic Fusarium."

A DISEASE.

As has been mentioned earlier in this paper^ a disease which is
probably bacterial and resembles flacherie of the silkworm is quite
common upon larvae and pupae of Eurymus. At times, evidently
during periods of higher humidity accompanied by warm weather,
as in July and August, it becomes so widespread as to kill a great
majority of a brood and often nearly annihilates it. This disease is
by far the greatest natural check against which the alfalfa cater-
pillar has to contend and is one of the most important factors look-
ing toward its control.

The dead worms, which are nothing but soft decayed masses found
hanging to the alfalfa stalks, are sometimes so numerous as to make
sweeping with an insect net impossible, the net in a few sweeps be-
coming so foul as to> render other insect specimens of little value.
The disease has proved a great detriment to the successful carrying
on of life-history experiments and the rearing of parasites, owing
to the fact that large percentages of larvae taken to the laboratory
and confined often die from it. Frequently, where a hay crop is not
totally destroyed by a brood of caterpillars before they are killed by
this disease, the decayed remains on the hay become so foul as
to render the hay quite unpalatable for horses and hence of low
value.

As has been suggested, the development of the diseased condition
in either larvae or pupae — for it attacks both — depends largely upon
moisture. The disease is present at all times, and a few larvae from
each brood are killed, but it is only when a period of high humidity
accompanied by warm weather occurs that it becomes so prevalent as
to attack the worms in large numbers. It has been found that at
certain times these conditions of moisture may be produced arti-
ficially by irrigation, and, as is discussed in a later paragraph, the
disease, thus fostered, is utilized as a factor in controlling the pest.
That the disease does not at all times keep the caterpillar in check
is doubtless due to the dry climate of these southwestern countries,
and a comparison of the conditions in the Imperial Valley of Cali-
fornia Avith those in the Salt River Valley of Arizona supports this
view. The Imperial Valley is unique in location, being below sea

28 BULLETIN 124, U. S. DEPARTMENT OF AGRICULTURE.

level and having an average annual rainfall of probably less than
2 inches, while the Salt River Valley has an elevation of some 1,200
feet and an annual rainfall of about 8 inches. A study of the out-
breaks of Eurymus in the two valleys shows them to vary inversely
with the rainfall. In the dryer Imperial Valley the outbreaks are
more numerous and severe and the resultant damage is greater than
in the Salt River Valley with its greater rainfall and its longer
period of humid weather during the hot summer months.

The worms when first attacked take on a lighter green color and
become sluggish; but in a few hours they change to a brownish*
black and melt down into a decaying mass. A first sign of the!
breaking down of tissues may often be noted when the worm is still
active, a slight exudation at some small broken place, usually in
front; and the writer has noted specimens with the anterior end
blackened and the posterior end still slightly moving, showing that
life was not yet extinct. The attack upon a pupa is similar, except
that the stronger pupal covering usually prevents the melting down
of the specimen, and later the decayed contents of the interior dry
up, leaving the empty black shell still intact.

BIRDS AND DOMESTIC FOWLS.

Few records are available showing the relation of wild birds to
the alfalfa caterpillar. Several times the writer has observed birds
with larvae in their bills, but he was unable to capture these, not
having the necessary firearms. Domestic fowls, however, play an
important part in the history of this insect. In alfalfa adjoining
farmhouses where chickens or turkeys have the run of the field one
rarely finds alfalfa caterpillars in numbers, whereas fields adjoining
chicken lots inclosed with wire fence, keeping the poultry out of the
alfalfa, suffered severe damage. In Mr. R. N. Wilson's notes for
1912 he reports that " Mr. Carlos Stannard, living 4 miles northeast
of Glendale, Ariz., killed a young rooster and found 24 Eurymus
larvse in the rooster's crop." Mr. T. Scott Wilson was informed by
Mr. Everett, living near Tempe, that he and his wife had found a
dozen larva? in a chicken's crop, the chickens having access to an al-
falfa field growing near the house. By the same observers, turkeys
have been noted feeding greedily upon the larvae, a flock in travel-
ing across an alfalfa field eating hundreds of them. Mr. T. Scott
Wilson, on July 21, 1913, at Chandler, Ariz., made the following
note :

I observed one dozen turkeys in a half acre of alfalfa on the lots of the
United States power house feeding upon Eurymus larvae. The alfalfa
is about 12 inches high and is tender. I find only a few Eurymus feeding
upon this alfalfa, while in a large field just across the fence the alfalfa is
almost destroyed, except that in that portion next to the house where the tur-

THE ALFALFA CATERPILLAR. 29

keys likewise feed tliere are few Eurymus to be found, and consequently no
damage. * * * j jijgQ observed several chickens feeding upon Eurymus
larvae.

From these observations it is seen tlia.t chickens may be utilized
in small fields to keep down the numbers of alfalfa caterpillars, and
that turkeys, because of their roving nature, can be used to advantage
in larger fields. Mr. Charles Springer, of Cimarron, N. Mex., in-
forms the writer that he hires a boy to herd an immense flock of
turkey's on the range, so that they may feed upon the grasshoppers
destroying the grama grass and other range grasses (see PL I, fig.
2, p. 4). It seems that the same method could be employed in out-
breaks of the alfalfa caterpillar.^ There is always a good demand for
fattened turkeys, and with the cheap labor of a Mexican boy for
herding the turkeys, if this additional expense is really necessary, the
caterpillars could be kept within bounds at a very small cost per acre,
or possibly even at a profit.

OTHER ENEMIES.

Quite a few observations have been made upon the food habits of
toads. These batrachians have been found to feed upon both adults
and larvse of Eurymus, as many as 45 adults and 1 larva having been
found in a single stomach on one occasion, while on another 15
Eurymus larvae were found, besides 4 of Heliothis, 3 geometrids,
3 larvae not classified, a cricket, and the remains of a few beetles.
As toads are quite numerous throughout the alfalfa fields of the Salt
River Valley, they must exert a considerable influence toward the
suppression of outbreaks of the alfalfa caterpillar.

THE CONTROL OF THE ALFALFA CATERPILLAR.

PASTURING VERSUS HAYING.

It was first noted by the writer in 1910, during his early study of
the subject, that fields in pasture are never troubled as much by the
alfalfa caterpillar as are haying fields. Since then this has been
clearly verified, not only by the writer but by others connected with
the work. On July 14, 1913, Mr. R. N. Wilson makes the following
note, which bears out this statement:

Many of the fields about El Centro have been cut recently and so show
nothing now as to Eurymus conditions. Many are also being pastured, and
in these the caterpillar attack is slight. In some fields which have not been
either pastured or cut the damage is considerable.

There are several factors which explain this. At first it was
thought to be owing entirely to the lack of bloom for the butter-

1 Of course care should be exercised not to allow the turkeys in the alfalfa after it has
become too high and rank, nor should too great a number be used in any one field, as in
such cases the alfalfa might be badly trampled.

30 BULLETIN 124, U. S. DEPARTMENT OF AGKICULTUEE.

flies to feed upon and to the fact that the greater part of the fields
was kept closely grazed, making the alfalfa less favorable for the
laying and development of the eggs. Under such conditions the
number of eggs deposited in a given field is greatly reduced. Many
of the eggs laid on the young growth under such conditions are
destroyed by the grazing of the stock, and the percentage that de-
velops is kept at a minimum. Later on it was noted that on the
stock ranches visited the disease previously mentioned, which is com-
mon to lepidopterous larvss, was more prevalent in pastured ranches
than in hay ranches. The prevalence of the disease in such fields
is clue to the fact that usually a few days after stock are turned in
the alfalfa becomes trampled. The ground and the alfalfa are very
moist, there being more or less dew every morning, and droppings
from the cattle bring about a foul condition in the field, thus assist-
ing in the retention of moisture, Avhich, in turn, is conducive to the
development of the disease.

If fields can be systematically and carefully pastured, damage from
the caterpillar will accordingly be at a minimum. Cattle should
never be allowed on a field when wet nor for too long a period,
say from 24 to 35 days, and disking or renovating should always
follow so as to loosen the soil and place it in a receptive condition
for future irrigation.

It is on ranches and fields from which successive crops of hay are
taken that the height of the damage is reached. In such fields the
conditions for the development of the species are as nearly ideal as
possible, and here the worms are ordinarily unmolested in their feed-
ing and growth. The period elapsing from the time that one crop is
cut until another is ready for harvesting so nearly coincides with the
length of the period necessary for the develo])ment of any one gen-
eration of the butterfly that the cutting of the hay, as ordinarily
carried on, does not reduce their numbers or disturb their work,
since the worm will likely be in the advanced stage, or, perhaps, have
passed into tlie pupal stage, before the crop is cut.

CONDITIONS AFFECTING INJURY.

As has been pointed out, this insect is ordinarily kept in control
by its natural enemies, such as insect parasites and diseases, and it is
only upon the occnrrence of conditions unfavorable to the development
of these enemies that serious outbreaks occur. It has also been noted
time and again, both by the v;riter and others, that the seriousness
of the damage quite often depends upon the farming methods used
by the individual whose fields are attacked, or upon certain other
conditions, such as character of soil, quantity of water for irrigation,
location of land, etc. The former are conditions that the individual
may remedy by changing his methods, while the latter may be prac-
tically alleviated by proper handling of the farm in question.

THE ALFALFA CATERPILLAR. 31

The damage in some alfalfa fields is quite often apparently cor-
related with the condition of the soil. A field seriously damaged
often reveals a poor soil — at least a soil not well adapted to alfalfa
culture, and consequently producing a slow-growing crop. Of course
not all of the fields damaged were of poor soil ; some of the very best
alfalfa fields were seriously ravaged, but in these cases this was often
attributable to other factors. Sandy loams or light soils are the
best for alfalfa production, and consequently are the least damaged,
owing to the fact that the alfalfa, growing more rapidly, is often
able to recover from insect attacks and be ready for harvest before
any noticeable damage has been done. A heavy soil can be improved
and the growth of the alfalfa increased by deep plowing and thor-
ough preparation of the seed bed at time of seeding the crop and
then by renovating the alfalfa several times a year, either by disking
or by the use of an alfalfa renovator. By such a procedure in irri-
gated regions the soil will more readily take water, and thus plant
growth will be stimulated.

A fanner who attempts to use up-to-date and proper cultural
methods is unfortunate indeed when his alfalfa fields, for which he
is caring properly, are just across the fence from fields that are run
down, and hence are breeders of insects. No matter how careful his
efforts, some damage may be done owing to reinfestation of his fields
from the butterflies supplied by his neighbor's field, Nevertheless
enough may be accomplished through his own efforts to pay many
times.

Again, the amount of water applied is often insufficient, sometimes
because of neglect on the part of the rancher, and sometimes because
of scarcity of supply. The former case is under the rancher's con-
trol; he should use care in applying the water and should eliminate
waste. Sufficient water should be used to provide for the prompt
development of the alfalfa crop, for in this way the farmer can
reap his crop earlier and before the caterpillars have effected much
damage.

Soon after agents of the Bureau of Entomology began observations
and experiments looking toward the control of the species it was
noticed that damage to alfalfa was often, although not always,
associated with careless methods of farming and a lack of appre-
ciation on the part of some ranchers of the benefits to be derived
from carefvi], clean cultural methods. This is sometimes due to the
fact that tlie rancher is trying to cultivate more land than it is
possible for one man to farm successfully with the limited amount
of labor and capital at his disposal. A great many times poor man-
agement is responsible for a failure where other methods would have
meant success.

32 BULLETIN 124, U. S. DEPAETMENT OF AGEICULTUEE.

CLOSE CUTTING AND CLEAN CUTTING.

In harvesting the hay crop ranchers usually have to depend upon
labor tliat, while often the best obtainable, is not by any means of
the best class, and thus cutting is often done in a careless manner,
stubble is left high and ragged, bunches of hay are left uncut at turn-
ing rows or on borders, ditch banks and fence rows are rarely or
never cut, and the field presents the spectacle shown in Plate I, fig-
ure 3, page 4, and Plate II, figure 3. Thus any caterpillars that may
still be present have a considerable amount of alfalfa upon which to
feed and develop, and soon do so, so that the butterflies from these are
ready for the next crop. Such places also afford bloom which attracts
adult butterflies from other fields, and these lay eggs on the new
alfalfa that soon springs up. If such neglected fields are treated as
are those shown in Plate II, figures 1 and 2, there will be no food to
enable any remaining caterpillars to complete their development;
besides this, there will be no protection for them from an early
irrigation or the rays of the hot sun, either one of which will kill
them. Heat of the midday sun, accompanied by prompt irrigation
immediately following such clean cutting, will nearly always kill
Eurymus larvae, especially in the warm Southwest. This is such an
important item that one should not hesitate to go to the necessary
exj)ense in order to secure such a condition of cleanliness. In two
cases in the Imperial Valley in 1910 it became necessary, because
the hay had lodged badly, to remow a field at a cost of from 30 to
50 cents per acre, and in each case the results obtained in the follow^
ing crop more than paid for the cost of the experiment.

EXPERIMENTS AND OBSERVATIONS IN CALIFORNIA.

In California, in 1910, 10 fields were selected in which good cul-
tural conditions were to be created and in which methods were to
be inaugurated that would not further the development of the cater-
pillars. The thing done in these fields was to put them under a sys-
tem that would remedy as far as possible all or part of the defects
recorded on a previous page. During that season (1910) a large
part of the damage was due to the caterpillars of the third and
fourth generations, the first and second not being numerous enough
to assume any serious aspect. The task, then, was to keep their
numbers below the point at which they could do any considerable
damage. The time to start this control work was naturally with
the earlier generations. The 10 fields mentioned (no two of which
had had the same conditions of culture previous to that year, and
which had all suffered more or less damage the year before, namely,
in 1909) were given what might be termed clean culture, or careful
management. Just as soon as possible after removing a crop of hay

3ul. 124, U. S. Dept. of Agriculture.

Plate II.

Fig. 1.— Fence Row Bordering Alfalfa Field, Showing Clean Cutting,
WHICH Helps TO Reduce the Alfalfa Caterpillar as Well as Other
Insect Pests. (Original.)

Fig. 2.— Alfalfa Field Showing Close, Clean Cutting Necessary for
Reducing a Generation of Alfalfa Caterpillars. (Original.)

Fig. 3.— Fence Row and Ditch Bank Showing Neglected Growth of
Alfalfa and Grass, which Offers Protection and Hibernating
Quarters for the Alfalfa Caterpillar and Other Insect Pests.

CLEAN CULTURE AND THE ALFALFA CATERPILLAR.

i

THE ALFALFA CATERPILLAR. 33

the field was irrigated thoroughly, thus starting the growth quickly.
The field was again irrigated as soon as the diy condition of the
crop required, and thus the growth was forced and not allowed to
be checked.

It requires about 28 days to produce a hay crop in the Imperial
Valley — a little longer than this in the spring and fall, and a few
days less in warmer weather. It also takes practically the same
period of time, as has been shown on a previous page, for the butter-
flies to develop from egg to adult. Now, if the crop of hay be forced
by frequent watering, or because of good soil conditions, the worms
will not have gone into the resting stage at time of cutting, but, in-
stead, will still be feeding on the green alfalfa, and when the hay is
cut and removed conditions will be unfavorable for their develop-
ment and their food supply will be reduced. The hay in these fields
was cut just as it was coming into bloom, which is a few days
sooner than it is generally thought advisable to cut it. The advan-
tage of this early cutting is often very important, for if worms are
present in damaging numbers they will take a whole field in a short
time. In this case not only will the hay be saved, but a major portion
of the larvae, if clean cultural methods are used, will find a lack of
the food necessary for their complete development, and this, asso-
ciated with hot weather and irrigation following the removal of the
cured hay, will cause them ultimately to perish.

Of the 10 fields handled according to these methods only 1
was damaged to any considerable extent. The other 9 were not
entirely free from larvae, but the numbers were so reduced as to pre-
clude any chance of noticeable injury to the alfalfa. In the one
exceptional field the damage was due to the fact that irrigation had
been delayed for nearly two weeks after the cutting of the second
crop, owing to a new ditch which was under construction. Being
a thrifty field naturally, the alfalfa had made a start, assisted by
the moisture still present in the ground, and butterflies coming in
from an outside field deposited eggs on this new growth, thus en-
abling the worms to destroy the best of the crop after it was finally
irrigated. As a result almost an entire crop was lost. A field ad-
joining on the south, which had been irrigated immediately after
cutting, was not in the least damaged. This was a lesson in itself,
as it indicated the necessity for prompt work.

These observations in California in 1910 have been further sup-
plemented by observations at Tempe, Ariz., and El Centro, Cal., in
1912. This year (1912) the writer made two trips into the Imperial
Valley. Several ranchers had kept records of their methods of hand-
ling alfalfa, and these records show conclusively the same results as
those of 1910. Two ranchers especially were found who had prac-

34 BULLETIN 124, U. S. DEPARTMENT OF AGRICULTURE.

tically controlled the pest in the last few years, and they have
accomplished it altogether by such methods as have just been de-
scribed. One of these men, Mr. Henry Stroven, whose ranch is
north of Holtville, says that he has had a minimum of damage.
His ranch evidences his careful and systematic cultural methods.
Ditch banks and fence rows are clean, and there is scarcely a
weed noticeable on the entire ranch. Mr, Stroven informed the
writer that he always renovates twice a year and sometimes oftener
and also aims to keep his alfalfa abundantly watered in order to
get a quick, thrifty growth. The other rancher, Mr. "William INIans-
field, of Brawley, practices the same methods in use by Mr. Stroven,
and his ranch also shows this. Neither of these ranchers aims to
allow his alfalfa to stand longer than five years in a certain field.
Instead, he plows it up, raises some other crop for a 3'ear, and then
reseeds to alfalfa, thus bringing into play a system of crop rotation
whicii not only kepps the soil in excellent condition, but prevents
insect increase. Mr. Mansfield told the writer that in 1908 he had
considerable damage when his May cutting was getting a little more
than two-thirds grown. One day he noticed that damage from the
caterpillar was very apparent. The next day the effect was much
more noticeable. So he mowed the alfalfa, taking it up at once, and
irrigating as soon as possible. He thus saved by far the greater part
of the crop infested and, besides, was not troubled again that year.

The following observations, made by Mr. R. N. Wilson in July,
1913, also bear out the foregoing statements:

One farm was examined near JNIeloland, CaL, to-day. This is a dairy farm
belonging to Mr. Cooli. In order tliat the hay may be in the best condition,
Mr. Cook cuts it just as it conies into bloom. He in this way gets two more
cuttings of hay per year than his neighbors, who allow their fields to come to full
bloom before cutting. His crops have never been badly injured by Eurymus,
while his neighbors have more or less injury every year. He also keeps his
alfalfa in a thrifty condition, and the rapid growth is another element in
Eurymus control.

These three examples show the practicability and the success of
the methods proven by observation and experimentation to be means
of controlling outbreaks of the alfalfa caterpillar.

EXPERIMENTS AND OBSERVATIONS IN ARIZONA.

Observations similar to those in California were made in Arizona
by the author in 1912 and in 1913 by Mr. T. Scott Wilson. The same
relation has been noted to exist between clean culture and good farm-
ing methods in general and damage by the alfalfa caterpillar as
existed in California, But in Arizona, as the soil conditions are
somewhat different from those in California, it is necessary for the
application of water to be even more timely. In many parts of the

THE ALFALFA CATEEPILLAK. 35

Salt River Valley there is a layer of subsurface water. This is lack-
ing in the Imperial Valley. Thus when a crop has been removed
in the former place alfalfa soon sprouts, and eggs are laid sooner and
have made some headway when irrigation has finally been accom-
plished. While there is a limit to the promptness with which a crop
can be removed from the ground after being cut, and consequently
a limit to the promptness with which the ground can be irrigated, yet
these measures should always be carried out just as soon as possible,
thus avoiding damage b}^ reason of the difference noted.

In 1912 Mr. Peter Aepli, living a mile south of Tempe, began cul-
tural methods especially meant to control outbreaks of the alfalfa
caterpillar. It is to be noted that even previous to this time Mr.
Aepli had carried on a system of crop culture that would secure the
maximum returns from his land; so that about the only change
in his methods was an addition of factors that take into consideration
the status of the alfalfa caterpillar at the time of each cutting; that
is to sa}', he cuts at a time that will do the most harm to any larvae
that may be present and before any damage is done to the alfalfa.
August 1, 1912, it was found that a considerable number of cater-
pillars were present in Mr. Aepli's field and that he would have to
cut earlier than he had intended in order to save it from serious
damage. On August 3 he cut the hay, doing a fine clean job. On
August 5 he removed the hay from the ground and then followed
this with disking and irrigation. The worms were all killed, the
present crop saved, and no further damage was done to the alfalfa
in that field that year. The effect of these careful and painstaking
methods was also noted in the field the year following. From Mr. T.
Scott Wilson's notes of August 4, 1913, is quoted the following :

An 80-acre field of alfalfa across the fence from Mr. Aepli's is almost com-
pletely destroyed, while Mr. Aepli's is damaged but very little. Mr. Aepli is
cutting his hay to-day. The larvae are not full grown yet, so he is taking their
food from them before they mature. He usually cuts his hay close to the ground
and before it gets too ripe, hence Eurymus do not bother him much.

Another example of the effect a careful system of clean cultural
methods will have upon caterpillar devastations is noted in a 640-
acre ranch just south of Tempe, Ariz. Here the clean-up methods are
accomplished by a combined system of haying and pasturing and are
quite successful. The ranch should really be termed a cattle ranch,
but after the owners' young steers that have been raised on their
range in northern Arizona are fed out in the winter and spring, sev-
eral crops of hay are made, stacked up in the field, and fed the next
winter. The hay from such crops is cut often, not allowed to get
overmatured, and as the owners emplo}^ a large force of men it is
hastily stacked and then, following this, 40 to GO head of steers are
turned in for about three days, during which tune they clean up

S6 BULLETIN" 124, U. S. DEPARTMENT OF AGEICULTTJRE.

every growing sprig in the field. They are then sent to another field,
and so on and on, the owners in this way keeping their alfalfa ahead
of the butterflies, and by the clean-up method few larvae are allowed
to develop to adults. Of course, not everyone can have stock available
at just the right time, but this is another example of what clean-up
methods will do.

IRRIGATION AS A FACTOR IN CONTROL.

As has been stated in a previous paragraph, moisture is conducive
to the development of the disease which plays an important part in
the control of this insect. A number of experiments were therefore
tried by which, with the use of irrigation water, an attempt was
made to supply moisture artificially so that the worms would be-
come diseased. This was found to be quite successful. In fields
where clean methods of cutting are used at haying time and this is
unmediately followed by irrigation, there seems little doubt that a
part of the mortality of the larvse is due to the effect of irrigation.
The beating sun, of course, kills a great many, and then, as has been
shown, under such a procedure the food supply is cut off and the de-
cayed remains of larvfe are found hanging in great numbers to the
alfalfa stubs about two days after such a procedure. This led the
way for other experiments ; accordingly, during the summer of 1913,
Mr. T. Scott Wilson made a number of observations on irrigation of
alfalfa at a time when the worms were beginning to appear numer-
ously, and he found that invariably this gave the disease the neces-
sary moisture and the worms soon died. For a rancher to take ad-
vantage of this would, of course, mean that he must have water
available any time he wants it, which is not the case in all irrigated
regions, as water is usually distributed in turn. However, in cases
where the time for irrigation corresponds with the occurrence of an
outbreak the water can be utilized and the worms killed.

VALUE OF DISKING AND RENOVATION.

It has been suggested before that an alfalfa field should be disked
or renovated annually, or oftener, in order to keep the sod in good
loose condition, so that it will take water readily and be aerated,
and also to kill weeds. If teams are available, the best procedure
would be to renovate several times, or at least twice a year. The
usual method is to renovate once, and this during the winter. Now,
if the alfalfa can be renovated in August, immediately after the
third crop is removed, not only will the ground be placed in an
excellent condition and weeds killed, but any larvae or pupae on the
ground will be killed and future crops protected from damage.
Some ranchers do this already and claim great results for it, and

THE ALFALFA CATERPILLAK. 37

a few even renovate oftener. Mr. Stroven, of Holtville, CaL, reno-
vates just as often as it is possible for hini to do so, and in 1911 this
was four times. Leaving the matter of insects entirely out of con-
sideration, enough benefit is derived from renovation to pay many
times for the cost of the work. If a disk harrow is used, it should not
be set at an angle, as this would be likely to cause injury to the crowns,
but should be- run straight and forced into the ground by weights.

DIRECT METHODS OF CONTROL.

INSECTICIDES.

In dealing with insect pests affecting cereal and forage crops it
has proved possible in only a few instances to control them by the
use of any of the various insecticides or poisons. The reason for this
lack of success lies largely in the fact that such crops are distributed
over a wide area, and the expense of application of any insecticide as a
control measure is necessarily high, while a lack of thoroughness is
likely to arise when one tries to keep the expense of treatment down
to an economical basis.

Since the alfalfa hay is fed to stock, it is not possible to use any of
the arsenical poisons against the caterpillar of the alfalfa butterfly.
A few experiments, however, were tried with pyrethrum, or "buhach."
As this is not a poison, and since its fatal effect upon the larva? of
butterflies is produced externally through their breathing pores,
there would be no danger to stock. Pyrethrum was used in one case
in 1910 in full strength, and in another instance it was diluted with
equal proportions of flour. An application was made by dusting this
substance from a cheesecloth sack, following the primitive method
of applying Paris green to potato vines, at the rate of 3 pounds of
pyrethrum to the half acre, which in the case of diluted material
would make 1^ pounds of pyrethrum to the half acre. This first
test was made on July 8, 1910, and no results were obtained, because
of t)ie fact that just two days later practically all of the worms in
the field where the test was being made were destroyed by the malady
before mentioned. The same experiment was repeated, however,
on September 22, and in this case the results were negative, not a
caterpillar being killed. It would seem, therefore, that the applica-
tion was not sufficiently heavy to kill the worms, and that to have
increased the amount of pjni-ethrum applied might have resulted in
the eradication of the pest ; but as the cost of pyrethrum at the rate
of 3 pounds to the acre is already nearly $2, without considering the
expense of application by hand, this could not be considered from
an economic point of view.

In 1913 some additional experiments were tried with the same
material by Mr. T. Scott Wilson at Tempe, by using it full strength.
This killed about 50 per cent of the larvae, but the cost of application

38

BULLETIN 124, V. S. DEPARTMENT OF AGKICULTUEE.

was again too high, and a large enough number of worms were not
killed to justify the expense incurred.

ROLLING AND BRUSH DRAGGING.

At the time a field is being damaged by the worms the hay that
remains undestroyed can be cut and then either a brush drag or a
roller run over the ground, by which a great many of the larvse will
be destroyed. Some experiments tried along this line by Mr. T.
Scott Wilson were quite successful. On August 15, in a 5-acre patch
a brush drag was used and a great many larvse were killed. This
field was overrun by Bermuda grass, which protected many larvae
that would have been killed. A roller here would doubtless have

Fig. 20. — Brush drag used to crush alfalfa caterpillars in the fields. (Original.)

mashed all larvse. On the 26th of August another test was made,
using the same drag. In this case the larvse were about full grown,
and 55 per cent were killed by the operation. The latter experiment,
however, was carried on in alfalfa of considerable height, and con-
sequently the larvse were afforded much protection and as large a
percentage was not killed as would have been the case had the drag-
ging immediately followed cutting.

A good brush drag and one that is well adapted to dragging
alfalfa is shown in figure 20. The plan for constructing this, as
given by Mr. E. S. G. Titus, in Bulletin No. 110 of the Utah Agricul-
tural Experiment Station, is as follows :

The drag is made by laying the butts of rather short brush, five or six feet
long, in a row on a plank twelve or fourteen feet long, then another row should

THE ALFALFA CATEKPILLAK. 39

be laid upon the first, consisting of longer brush, with the butts trimmed a
little further back so that you will have in effect two brush harrows, one
following the other. Another plank should then be laid on the brush butts
and bolted to the under plank. In weighting this drag, lay an ordinary tooth
harrow, with the teeth down, directly on the brush drag. This makes a very
even weight, at the same time it is so flexible that the drag will work its way
down into the small depressions as well as over the larger elevations of the
fields.

A larva exposed to dust and hot sun soon dies. On September 4
three larvse were placed in a dust}^ spot by Mr. Wilson, and within
a few minutes all were dead. The next day the experiment was
repeated, and all larvae died. In all about 50 larvae were exj^osed to
the dust and sun, and of this number only 1 was able to crawl back
to alfalfa, the rest dying before they had crawled 10 inches on the
dust and dry dirt. The sun was very hot, and the temperature, 4
feet from the ground, was 97° F. These experiments show why so
many larva? die following careful methods of haying. They have
no protection from the hot sim wdien such methods are carried on.

CONCLUSIONS REGARDING CONTROL.

Keep the ranch in the best possible cultural condition. Irrigate
it often and thoroughly and as soon after cutting as the crop of hay
can be removed from the ground.

Renovate every winter and during the month of August, or even
oftener if possible, either by disking or by the use of an alfalfa ren-
ovator, thus disturbing any pupte that may be present, and putting
the land and alfalfa in condition for good growth of succeeding
crops.

Cut the alfalfa close to the ground and clean, especially along the
ditch banks, borders, and turning rows, as well as in the main part
of the field.

Cut the alfalfa earlier than is the general rule. The proper time
is when it is just coming in bloom or is one-tenth in bloom. Watch
for caterpillars in the early spring crop, and if many are observed
about grown, cut the hay a few days before it is in bloom, and thus
save the next and future crops.

A minimum amount of damage occurs in fields that are systemati-
cally pastured all or a part of the time.

A field should never be abandoned because the caterpillars threaten
the destruction of a crop of alfalfa before the hay can possibly ma-
ture. Mow it at once^ cutting it low and clean, thus saving part
of the present crop, and in so doing starve, and allow the heat of the
sun to kill, a great many of this generation of worms. Follow this
by disking and then by either rolling or brush dragging, and
a great majority of any remaining larvae will be killed. The ground

40 BULLETIN 124^ U. S. DEPARTMENT OF AGEICULTURE.

should then be thoroughly irrigated, and by these efforts the coming
crop will be assured.

Turkeys and chickens when allowed the run of a field will keep
the numbers of the caterpillars at a minimum.

The protection of toads should be encouraged, as they eat many of
these insects, as well as other injurious forms.

It has been noted that a carrying out of only part of these recom-
mendations wnll not at all times save one's crop. The best results
come to the one who is thorough in methods.

Cooperation among all farmers is necessary to suppress an insect
attack completely. An occasional outbreak has been known to occur
upon a farm or ranch that is under the best possible condition of
crop culture, but in each case it was noted that the careless methods
of a neighbor were responsible for the reinfestation.

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V

B??ELFEf?9F^r THE

USPEPMlIOFAfflaimi

No. 131

Contribution from the Bureau of Entomology, L. O. Howard, Chief.
September 10, 1914.

REPELLENTS FOR PROTECTING ANIMALS FROM
THE ATTACKS OF FLIES.'

By H. W. Graybill, D. V. M.,'
Assistant Zoologist, Zoological Divmon, Bureau of Animal Industry.

INTRODUCTION.

During the warm season of the year cattle, horses, and mules suffer
a great deal of annoyance and more or less injury as the result of
the attacks of various biting flies, and numerous requests are received
in this department concerning methods of relieving the animals from
these attacks. The flies that cause the greatest annoyance to domes-
tic, animals are the stable fly {Stomoxys calcitrans L.) and the horn-
fly {Lyperosia irritans L.). The horseflies (Tabanidse) are of some
importance and individually their attacks are sanguinary, but they
are not the cause of as much injury as either of the two species of
muscids that have been mentioned. The bot flies (Qilstridge) affect-
ing horses, cattle, and sheep are not biting flies and only visit these
animals to deposit their eggs. The larvae of these flies, however, are
parasitic and are the cause of considerable annoyance and more or
less loss, and for this reason repellents are sometimes applied to ani-
mals to prevent the adults from depositing their eggs. In the case
of the horse and the ox, parasiticides are applied to the skin to
destroy the eggs of bot flies that have already been deposited.

The screw worm {Paralucilia macellana Fab.) likewise is not
parasitic in its adult state, and visits animals only to deposit its eggs
in wounds where the larvse, when they emerge, may find nourishment
and complete their growth. There are also various other species of
flies that may deposit their eggs in wounds and whose larvse become
parasitic.

In the United Kingdom and Holland a bluebottle fly {LuciJia
sericata Meig.) deposits its eggs on the soiled wool about the anus,

1 The investigations reported in this paper were undertaken by the Bureau of Ani-
mal Industry incidentally during the progress of other investigations concerning stock
dips. Although comparatively few repellents were tested, it is believed that the data
obtained concerning substances which may be applied to live stock to protect them
from flies are of interest and value to the live-stock industry.

2 Resigned, April 16, 1914.

51293°— Bull. 131—14 1 1

2 BULLETIN 131, U. S. DEPARTMENT OF AGBICULTURE.

chiefly in yoiinj^ sheep, sometimes in udult sheep when badly kept,
and the larvae hatching from the eggs become parasitic in the skin.
In Australia several species of blowflies {Calliphora oceaniccB Desv.,
C. villosa Desv., and C. ruf fades Desv.) produce a similar condition
in sheep. Recently a cutaneous invasion of sheep with dipterous
larvae occurring at Cobham, Va., was reported to this department,
but the fly responsible for the trouble has not been identified. The
application of repellents and parasiticides is indicated in case sheep
are subject to the attacks of such flies.

The house fly {Muscn domestica L.) commonly visits wounds on
animals to suck up the exudates that occur there. It is the cause of
considerable annoyance to animals in this way; it prevents wounds
from healing and may introduce into a wound agents of infection
adhering to its body. Eepellents are therefore indicated and are
freijuently used on wounds to keep house flies away and also to
keep away such flies as may deposit their eggs in wounds, such, for
example, as the screw-worm fly.

The use of fly repellents is resorted to largely for the purpose of
relieving animals of the torment of biting flies or of preventing
infestation Avith the larvae of flies, without any reference to the con-
trol or eradication of such pests. In the case of such flies as the
stable fly and the hornfly, the use of repellents can be of only sec-
ondary importance as an eradicative measure, since a much more
effective means of getting rid of these pests lies in preventing them
from breeding. This may be done by preventing access of the flies
to materials such as manure, etc., in which they deposit their eggs,
and bv destroying the young stages that may be present in such
materials. However, the eradication of these flies in most instances,
or even a reduction in their numbers in many cases, is out of the
question, so that it is necessary to resort to the use of repellents or
other means to give relief to animals.

In the case of the horseflies, preventing them from biting is
probably as important a factor as can be taken advantage of in
bringing about control, yet it must be admitted that this means
can be of only very little importance. In the case of the bot flies
and the screw-worm flies, the use of repellents against the adults
and of parasiticides against the eggs and larvae is an important
method of eradication as well as a valuable means of protecting
animals.

INJURY CAUSED DOMESTIC ANIMALS BY BITING FLIES.

Aside from the transmission of various animal diseases by biting
flies, a matter of much less importance in this country than in the
Tropics, flies are generally assumed to be responsible for enormous
losses to farmers and stockmen. Because of the great numbers in

REPELLENTS FOR PROTECTING ANIMALS FROM FLIES. 3

which flies occur, the irritation they cause animals, the blood they
abstract, the movements they cause animals to make in fighting them,
and the unfavorable influence they have on the temper of dairy cows,
it is believed by both scientist and layman that flies are responsible
for very great financial losses.

According to Delamare (1908), a German professor named Leh-
mann is stated to have established that the supplementary expendi-
ture of energy corresponding to the agitation caused horses by the
attacks of flies amounts to a pound of oats a head per clay. Moore
(1903), of the SQuth Dakota Agricultural Experiment Station, says:
"\Mien we consider the intimate relationship existing betAveen the
milk yield and the physical comfort of the cow, no question can be
raised as to the benefit obtained by mitigating so far as possible the
annoyances of these pests." Hopkins (1891) states that the hornfly
so annoys cattle by its bite that the cows fail in milk and other cattle
fail in flesh. Garman (1892) says: "The injury done to cattle has
been greatly overestimated in some instances; j^et there can be no
doubt that the yield of milk from cows greatly worried by hornflies is
much reduced, and growing and fattening stock are doubtless re-
tarded by their attacks." Marlatt (1910) states: "During the first
years of the hornfly, when it was a new and little understood n^nace
to cattle, the losses occasioned by it were undoubtedly much exagger-
ated. Nevertheless, the loss when the fly is abundant is still very
considerable, showing in reduced vitality, lack of growth, or less-
ened yield of milk, the production of milk often being cut down
from one-fourth to one-half. In Canada the late Dr. James Fletcher
estimated the loss in Ontario and Quebec at one-half the product of
meat and milk." Bishopp (1913) describes an unusual outbreak of
the stable fly in 1912 in northern Texas and refers to various other
outbreaks that have occurred in the United States. In referring to
the injury due to the fly he states that many horses and cattle became
so weak that they gave up the fight against the pest. In a few cases
in which the animals were not protected they succumbed in a short time.
Texas fever was rekindled in an acute form in cattle that became
weakened as a result of the flies, and in many cases death resulted.
The influence of the flies on the milk production was marked, the
reduction being from 40 to 60 per cent, and in some cases cows were
completely dried up. Horses and mules lost 10 to 15 per cent in
weight during the outbreak. Cattle likewise suffered a great reduc-
tion in weight. It is estimated that in northern Texas over 300 head
of cattle, mules, and horses were killed directly or indirectly as the
result of the fly attack. This loss is estimated at $15,000, and the loss
in the milk production is placed at $10,000, and other losses are stated
to surpass these.

4 BULLETIN 131, U. S. DEPARTMENT OF AGEICULTURE.

Fuller (1913) has described an outbreak of the stable fly along
the east coast of South Africa. All classes of animals are said to
have suffered greatly from worry and anemia. Many cattle were
killed, and horses and cattle stampeded into the sea and into rivers
to obtain relief. The outbreak followed heavy rains.

The experimental evidence with regard to the losses due to flies
that is available in this country does not seem to indicate that they
are as a rule of such serious consequence as the foregoing statements
would lead one to believe. The seriousness of such outbreaks as
Bishopp and Fuller refer to can not be questioned.^ Carlyle (1899),
at the Wisconsin Agricultural Experiment Station, conducted an
experiment relative to injury due to flies in which two lots of seven
cows each were used. Lot No. 1 was kept during the day in a pad-
dock provided with shade trees, while lot No. 2 was protected from
flies by being kept in a screened stable. The cattle in both lots
were kept on the pasture during the night and taken off at 9 o'clock
in the morning. The experiment was continued for a period of
four weeks. The cattle in the lot protected from flies ate 835 pounds
more green corn than those that were unprotected. All the cows
lost in weight, but the protected cows lost nearly three times as
much as the others. In comparing the milk and butter production
of the first two weeks of the experiment with that of the two weeks
just preceding the experiment it was noted that there was a decrease
in both milk and butter. The milk reduction was greater for the
protected animals and the butter reduction was greater for the
unprotected animals. The conclusion reached was that the greater
amount of butter yielded by the protected lot was not sufficient to
pay for the increased trouble and expense entailed in stabling the
cows during the greater part of each day.

Kent (1903), in an experiment at the Oregon Agricultural Col-
lege and Experiment Station, used a proprietary repellent on four
dairy cows. Four untreated cows served as controls. The treated
cows gained a total weight of 265 pounds while the untreated ones
gained 212 pounds. In comparing the milk and butter records of
two cows from each lot that were in about the same st^ge of lacta-
tion with the records of the same cows during the two months just
preceding the experiment it was found that the treated cows lost
about 10 per cent less than the cows not treated.

Beach and Clark (1904), at Storrs Agricultural Experiment Sta-
tion, Conn., tested a proprietary fly repellent which the manufac-
turers claimed would effect a tremendous saving during the fly
season. The experiments covered a period of two seasons and the
cows were sprayed thoroughly once a day. The conclusions reached
by the authors are as follows: "1. The annoyance of cows by flies
seems to be overestimated. 2. Certain proprietary ointments known

REPELLENTS FOE PROTECTING ANIMALS FROM FLIES. 5

as ' fly removers ' will protect the animal to a greater or less extent,
but their use has little or no effect on the milk or butterfat secre-
tion."

Eckles (1905) carried on experiments for two seasons at the Mis-
souri Agricultural Experiment Station with a proprietary repel-
lent for the purpose of determining whether the use of a repellent
on dairy cows would have any influence on the amount of milk and
butter produced. During the first season 16 cows were used and
during the second season 22 cows were used. The fly season was
divided into periods of two weeks, and the herd was sprayed each
morning during alternate periods. A comparison was made be-
tween the sprayed and unsprayed periods. The conclusion reached
by the author was that the use of the fly repellent was fairly effec-
tive in preventing the annoyance from flies if applied every morn-
ing, but that the yield of milk and fat was not appreciably affected
by its use. The onlj'' advantage observed was that the cows stood
more quietly during milking. AVith regard to the shrinkage in
milk production during hot weather, the author has the following
to say: "The rapid shrinkage that occurs in the yield of a cow
during the hottest summer months is a well-established fact, but is
probably not so much on account of flies as to failure to graze suffi-
ciently, if on pasture, on account of the heat."

THE INFLUENCE OF COLOR ON FLIES.

Several years ago Dr. Schroeder, of the Bureau of Animal In-
dustry, called my attention to some pictures of Holstein cattle he
had taken in connection with some tuberculosis work, in which the
flies on the animals were confined almost exclusively to the black-
colored spots. Beach and Clark (1904) state that some animals
suffer more from hornflies than others and that dark-colored animals
suffer more than light-colored ones. Marlatt (1910) states that the
hornfly exhibits a certain preference for red or other dark-colored
cattle, and that such animals are more thickly infested has been
frequently noted. He states, however, that when the flies are abun-
dant this preference is not so strongly marked.

Marre (1908) refers to a discovery which a farmer in the vicinity
of St. Cyr made relative to the influence of color on flies. The
farmer had ITO cows in a number of stables and noted that flies had
a marked aversion for blue. The idea came to him to add blue to
the whitewash with which he coated the walls of his buildings each
year. After doing this the flies left his cattle stables.

The formula used for the wash is as follows :

Water 100 liters (105.6 quarts, or 26.4 gallouB).

Lime (slaked) 5 kilos (11 pounds).

Ultramarine blue 500 grams (1.1 pounds).

6 BULLETIN 131, U. S. DEPARTMENT OF AGRICULTURE.

Two applications, one in June and one in August, are recom-
mended. The present writer is not aware whether this observation
has been corroborated or not.

INTERNAL REMEDIES FOR REPELLING FLIES.

It would hardly seem likely that a drug could be administered to
animals that would prevent flies from making their customary
attacks. However, Ochmann (1911) has recommended potassium
tellurate for this purpose. According to him this chemical does not
affect the general health of animals. The hair, however, becomes
temporarily rougher, paler, and drier. The expired air, the per-
spiration, and the feces take on an intensely offensive garlic odor
which persists for a long time.

Two dogs received on two successive days each 0.25 gram of po-
tassium tellurate. The results appeared on the day of the first ad-
ministration and lasted three to four weeks. The olfactory sense of
one dog suffered considerably. One of the dogs formerly troubled
with ticks was no longer affected. The dogs were protected from
flies.

An ass was given 0.25 gram of the chemical in the feed for three
days. The action w^as negative. Another ass received on three suc-
cessive days 0.25 gram. On the second day the odor appeared in
the breath and disappeared one day after the last dose.

A mule received on three successive days 1.5 grams. The odor
appeared on the day following the first administration and gradu-
ally disappeared in 10 days. There were no unfavorable results. An-
other mule was given on three successive days 0.5 gram. The odor
appeared on the day following the second dose and disappeared one
day after the last dose. A mule received on two successive days 2
grams. An intense odor appeared on the second day and disap-
peared after six days.

The author states that flies lighting on the animals were repelled.

Mayer (1911) conducted experiments for the purpose of verifying
Ochmann's results, and reached quite different conclusions. Ten ex-
periments were carried out, nine on horses and one on a cow. Each
animal received in all 10 grams in single doses of from 1 to 5 grams.
The best method of administering the drug was to dissolve the salt
in drinking water. Subcutaneous administration leads to dry ne-
crosis. The drug was taken unhesitatingly and caused no ill results
except occasionally a staring coat in fine-haired animals. The garlic
odor of methyltellurid appeared in the breath of the cow and was
present for a long time. The odor appeared to a very slight degree
in the breath of three of the horses, but disappeared very soon.

REPELLENTS FOR PROTECTliSTC, ANIMALS FROM FLIES. 7

The author states that the administration of potassium tellurate in
all cases failed to protect animals from flies.

It would therefore seem likely that this internal remedy is not
efficacious. If it or any other internal remedy were found efficacious,
it is doubtful whether it could be administered to dairy cows with-
out imparting an odor to the milk. On the whole, therefore, the use
of internal remedies seems to be an extremely unpromising means of
repelling flies.

EXTERNAL REMEDIES FOR REPELLING FLIES.

There are almost innumerable homemade and proprietary ex-
ternal remedies for repelling flies. They contain various substances
that are distasteful to the insects. Many of them contain strongly
odoriferous ingredients that have a repelling influence on flies. The
qualities to be sought in a satisfactory repellent are: Absence of
toxic and other detrimental properties when applied externally to
animals; a marked repellent action on flies; and a duration of this
action for a reasonable length of time. A common defect of many
otherwise rather good repellents is the very short period during
Avhich they are effective. Some repellents are undoubtedly toxic
and must be used with care,

METHODS OF APPLYING REPELLENTS.

Repellents as a rule are in the form of liquids and may be applied
by means of a dipping vat, a pail spray pump, an atomizer such
as that commonly used in gardens and greenhouses for applying
insecticides to plants, or by means of a rag or a paint brush. The
method employed necessarily depends to a very large extent on the
number of animals to be treated, the physical character and toxicity
of the preparation, its cost, and the individual preference of the
farmer or stoclanan. Some preparations, either because of their
cost or their toxicity, or for some other reason, are not adapted for
use in a dipping vat or for application by means of a spray pump.
Others may be applied by any one of the methods mentioned.

Marlatt (1910) describes a special splash board for vats, devised
by J. D. Mitchell. By means of this board the splash caused when
the animal plunges into the vat is thrown back into the vat in the
form of a spray and many of the flies are wetted and carried down
with the dip. It is said that with vats equipped with such splash
boards from To to 80 per cent of the hornflies are killed.

EFFICACY OF PROPRIETARY REPELLENTS.

Lindsey (1903), at the Massachusetts Agricultural Experiment
Station, tried out 10 proprietary fly repellents. He found that four
were quite satisfactory, four others were less satisfactory, and two

8 BULLETIN 131, U. S. DEPARTMENT OF AGRICULTURE.

were unsatisfactory. The chief defect of the second group seemed
to be that they were not lasting. It is stated that these fly repel-
lents are sold at retail from $1 to $1.50 a gallon.

POWDERS AS REMEDIES.

Smith (1889), of the New Jersey Agricultural Experiment Sta-
tion, found by experiment that two powders were adapted for de-
stroying hornflies and stable flies, namely, pyrethrum powder and
tobacco powder. Pyrethrum acted promptl}^, but was objectionable
from a practical standpoint because of its expense and because it
lost its strength soon after application. Tobacco was found very
much more satisfactory though the killing power was less. He
recommended a proprietary powder having for its base tobacco dust
and containing crude carbolic acid or creosote. The method of pro-
tecting cattle from the hornfly that he suggested was to apply
carbolated fish oil to the bell}^, udder, and those parts of the animal
Avhere powder could not well be used, and to apply tobacco powder
to the base of the horns, the back, and at the root of the tail. The
effect of the oil is to repel and that of the tobacco to kill flies that
attempt to feed.

OILS AS REPELLENTS.

Almost any kind of oil, whether it has a pungent or disagreeable
odor or not, will repel flies to a certain extent. The mere physical
condition of the hair and skin of an animal treated with oil seems
to be repugnant to flies. Oils are used pure or in the form of an
emulsion, or in combinations or mixtures. Crude petroleum, cot-
tonseed oil, fish or train oil, and light coal-tar oil may be used pure.

Crude petroleum may be used in the form of an emulsion. The
formula and method of preparing it so as to make 5 gallons of
80 per cent emulsion are as follows :

Hard soap 1 pound.

Soft water i 1 gallon.

Beaumont crude petroleum 4 gallons.

In preparing the emulsion the soap should be shaved up and
placed in a kettle or caldron containing the required amount of
water. The water should be brought to a boil and stirred until the
soap is entirely dissolved. Enough water should be added to make
up for the lo.ss by evaporation during the process. The soap solu-
tion and the required amount of oil are then placed in a convenient
receptacle and mixed either by stirring or by means of a spray
pump. If properly prepared the stock emulsion will keep indefi-
nitely. When required for use the stock emulsion should be diluted',
one part of the emulsion to three parts of water being used. The
diluted emulsion does not remain uniformly mixed, so if allowed to
stand it should be thoroughly mixed by stirring before using.

REPELLENTS FOR PROTECTING ANIMALS FROM FLIES. 9

Jensen (1909) recommended the following mixture containing
crude petroleum for dairy cows. He states that it remains on cattle
for at least a week.

Commou lauudry soap 1 pound.

Water 4 gallons.

Crude i^etroleuni 1 gallon.

Powdered naphthalin 4 ounces.

Cut the soap into thin shavings and dissolve in water by the aid
of heat; dissolve the naphthalin in the crude oil, mix the two solu-
tions, put them into an old dasher churn, and mix thoroughly for 15
minutes. The mixture should be applied once or twice a week with
a brush. It must be stirred well before being used.

A mixture of cottonseed oil and pine tar in the proportion of two
parts of the former to one part of the latter has been recommended
to relieve cattle of flies.

Fish or train oil is generally rated as one of the best repellents.
Its protective action is said to last from two to six days, depending
on the temperature and humidity. A great many mixtures have
been recommended in which fish oil occurs as an important ingre-
dient. Moore (1903) recommended the following mixture for use
on dairy cows:

Fish oil .__ 100 parts.

Oil of tar 50 parts.

Crude carbolic acid 1 part.

The cost of the mixture was about 35 cents per gallon. The mix-
ture was applied with a small hand spray pump. One application
was effective for two days.

Bishopp (1913) gives the following formula for a mixture that is
said to be very effective in keeping flies from live stock, when applied
lightly :

Fish oil 1 gallon.

Oil of tar 2 ounces.

Oil of pennyroyal-- 2 ounces.

Kerosene I pint.

Parrott (1900), at the Kansas Agricultural College, found that
repellents were not as effective in Kansas as they were said to be in
other States. Fish oil was effective for less than two days.

The following formula is recommended by him as being as effec-
tive as fish oil, and at the same time cheaper and more lasting:

Pulvei'ized resin 2 parts (by measure).

Soap shavings 1 part.

Water i part.

Fish oil 1 part.

Oil of tar 1 part.

Kerosene 1 part.

Water 3 parts.

51293°— Bull. 131—14 2

10 BULLETIN 131, U. S. DEPARTMENT OF AGRICULTURE,

Place the resin, soap shavings, the one-half part of water, and fish
oil together in a receptacle and boil until the resin is dissolved.
Then add the 3 parts of water, following with the oil of tar mixed
with the kerosene. Stir the mixture well and allow it to boil for
15 minutes. When cool the mixture is ready for use and should be
stirred frequently while being applied. Application should be made
with a brush. One-eighth to half a pint is required for each animal.
The cost of the mixture is given as 30 cents a gallon.

The present writer has not made or used the above repellent. Its
formula and method of preparation seem too complex for wide
use. It would appear that great caution should be exercised in boil-
ing the mixture because of the inflammability of some of the in-
gredients.

The same author recommends the following formula for horses.
It is said to be effective for three to four hours and even longer :

Fish oil 2 quarts.

Carbolic acid (crude) 1 pint.

Pennyroyal 1 ounce.

Oil of tar 8 ounces.

Kerosene * li quarts.

The cost is given at about 80 cents a gallon. The mixture must be
applied with an atomizer and not with a brush.

Carlyle (1899), of the Wisconsin Experiment Station, states that
fish oil to which is added a little oil of tar and a little sulphur will
serve to protect cows from hornflies for four to five days if the
weather is fine. He states that none of the remedies seem to be
effective against the stable fly an hour after being applied.

Otis (1904) recommends a repellent worked out by the entomologi-
cal department of the Kansas station. The formula is as follows:

Resin 1^ pounds.

Laundry soap 2 cakes.

Fish oil i pint.

Water enough to make 3 gallons.

Dissolve the resin in a solution of soap and w^ater by heating.
Add the fish oil and the rest of the water. Apply with a brush. If
to be used as a spray, add one-half pint of kerosene. The cost is 7 to
8 cents a gallon.

Fish oil containing a small admixture of carbolic acid has been
used with good success as a repellent.

Lindsey (1903), at the Massachusetts Agricultural Experiment
Station, found light coal-tar oil quite satisfactory. This oil is de-
scribed as the lighter of two oils derived from tar. It is a dark,
thin oil with a strong creosote odor. It was applied as a spray.

1 Or erough to make 1 gallon of mixture.

KEPELLENTS FOE PROTECTING ANIMALS FROM FLIES. 11

Kerosene mixed with cottonseed oil or in the form of an emulsion
may be used for repelling flies. Spencer (1904), at the Virginia
station, used an emulsion of kerosene in a special spraying apparatus
for destroying the hornfly. The formula and method followed in
preparing the emulsion are given below :

Yellow soap i pound.

Soft water 1 gallon.

Kerosene oil 2 gallons.

Shave the soap fine and dissolve in water at boiling temperature.
Place the kerosene in a barrel, add the hot-soap solution, and by
means of a spray pump agitate for 15 to 20 minutes, or until euiulsi-
fication is complete. One gallon of water is added to prevent the
solution becoming thick. This is a stock solution and should be
diluted in the proportion of 1 to 5 of water. The diluted emulsion
tends to separate, so only the amount needed should be diluted each
time.

It is stated that at the Virginia Agricultural Experiment Station
daily sprayings for a period of two weeks reduced the hornflies to
a point of insignificance. The flies were killed in passing through
the spray.

A milk emulsion of kerosene may be made as follows : To 1 part of
milk add 2 parts of kerosene and mix by means of a force pump, or
in some other way. The creamy emulsion that results is to be diluted
with 8 or 10 times the bulk of water.

Mayer (1911) found that laurel oil applied to the skin of cattle and
horses repelled the flies. The oil produced an inflammation of the
skin in some of the tests. The oil applied to bedsores of horses re-
pelled the flies and produced no change in the sores.

Laurel oil and linseed oil in the proportions of 1 to 10 repelled
flies from a bedsore on the foreleg of a horse for five days. The
entire right side of a horse was rubbed with the oil. No flies were
seen on the right side and great numbers were present on the left
side. The action lasted for 12 days. A light application of oil to a~^^
horse was effective for only two days. This mixture Droduced no
inflammation of the skin.

The following mixture was also tested by Mayer: Laurel ^ilj^^l
])art; dilute alcohol, 4 parts; and olive oil, 5 parts. In place of i
dilute alcohol denatured alcohol with water may be used, andini
place of olive oil linseed oil may be used. The mixture was tried on
horses, but the results were not so good, as the mixture did not stick.
The action lasted five days.

Rancid oil should not be used on account of its irritating action.

12 BULLETIN Vn, V. S. DEPARTMENT OF AGRICULTURE.

REPELLENTS FOR APPLICATION TO WOUNDS.

Jensen (1909) gives three formulas of repellents for application
to wounds:

Formula No. 1 :

Oil of tar S ounces.

Cottonseed oil to make 32 ounces.

Formula No. 2:

Powdered napMhalin 2 ounces.

Hydrous wool fat 14 ounces.

Mix into an ointment.
•Formula No. 3:

Coal tar 12 ounces.

Carbon disulphid 4 ounces.

Mix ; keep in ii well-stoppered bottle and aiiiply with a brush.

Mixtures Nos. 2 and 3 are said to adhere to moist surfaces, and No.
3 is said, in addition, to form a coating over raw surfaces and protect
froan the screw-worm fly.

The editor at the close of the article in which the above formulas
are given adds the following formula :

Oil of turpentine 1 dram.

Phenol 1 dram.

Cottonseed oil to make 4 ounces.

Mix and apply freely to wounds.

It is stated that this remedy is highly effective and is used widely
in the South. It is said to induce healthy granulation of wounds.

EXPERIMENTAL TESTS OF VARIOUS SUBSTANCES AND MIXTURE^
FOR REPELLING FLIES.

For the purpose of determining the efficacy of various substances
and mixtures for repelling flies, a number of tests were made by the
present author at the Bureau of Animal Industry Experiment Sta-
tion during the summers of 1912 and 1913. The results of these tests
are given below. In making various mixtures for the purpose of trial
the plan adopted was to combine a pungent or odoriferous substance
with an oil which served mainly as a vehicle.

CRUDE CARBOLIC ACID.'

The following tests were made with 10 per cent crude carbolic acid
in cottonseed oil:

On July 22, 1912, a calf was sprayed with a mixture of 10 per

cent crude carbolic acid in cottonseed oil. About 2 quarts of the

mixture were applied. The calf was discovered down about 7 to 10
t

^A sample of the crude carbolic acid used in these tests was examined in the Bio-
jchemic Division of the Bureau of Animal Industry, and was found to contain 21.8
per cent phenols.

REPELLENTS FOR PROTECTING ANIMALS FROM FLIES. 13

minutes later with symptoms of carbolic-acid poisoning. There was
salivation, dyspnea, trembling, paralysis, inability to rise, rapid
breathing, and rapid and irregular beating of the heart.

Another calf was sprayed on the same date with about 1^ quarts
of the mixture. The calf showed distinct symptoms of carbolic-acid
])oisoning in 6 minutes. It showed a tendency to fall in 8 min-
utes, and fell in 14 minutes. The symptoms in the order in which
they occurred were: Salivation, dyspnea, musculai' tremors, loss of
muscular control, and finally motor paralysis. The breathing was
rapid and shallow.

It was necessary to destroy both of the animals.

July 15, 1913, applied the mixture to a calf by means of a brush.
Used 2f ounces of the mixture. The repellent action was very
marked. July 16, about 18 hours later, the animal was worried as
much by flies as were the controls. Oil was present only along the
l)ack. There was only a very faint odor of carbolic acid. The pro-
tection was practically nothing. There were no symptoms of poi-
soning.

The results obtained with crude carbolic acid may be summarized
as follows: In the case of the first two calves treated it shows that
carbolic acid in cottonseed oil is absorbed through the skin. It is
well known that carbolic acid, when combined with oil, loses its
caustic properties, but its toxic properties still remain, as evidenced
by the above cases of poisoning. It seems certain that in the case of
any such mixture, no matter how small the content of carbolic acid,
a certain amount of the same must be absorbed. The amount ab-
sorbed will depend, other things being equal, on the amount of the
mixture applied. In the third test that was made, the same strength
(10 per cent) mixture was used, but it was applied with a brush and
only to the amount of 2f ounces. There were no symptoms of poison-
ing. It is therefore evident that a 10 per cent mixture of crude car-
bolic acid (21.8 per cent phenols) in cottonseed oil may be used with
safety if the application, is very light. It is undoubtedly true that
a very much weaker mixture of carbolic acid if applied liberally
would produce toxic symptoms.

The repellent action of this mixture, however, does not endure.
Its action was very marked at first, but lasted less than 18 hours.
It would be necessary therefore to apply this mixture every day. In
order to ascertain whether daily applications of the mixture could
be made without danger to the animal, a calf was treated with this
mixture on October 2, 3, 4, 6, 7, 8, 9, 10, 11, and 13. The mixture was
applied with a brush. There were no symptoms of poisoning or other
untoward results.

14 BULLETIN 131, U. S. DEPARTMENT OP AGRICULTURE.

PINE TAR.
TEN FEB CENT PINE TAR IN COTTONSEED OIL.

July 29, 1912, sprayed a cow with 10 per cent of pine tar in cotton-
seed oil. Used 3| quarts of the mixture.

July 30, the cow was looking droopy. The ears were hanging.

July 31, the hair was still oily. There was no odor of tar. The
animal was bright and perfectly normal. No hornflies were observed.
A few stable flies were present on the legs and body. The animal
was not fighting the flies, whereas unsprayed animals were con-
stantly switching their tails.

August 1, some oil was still present. Some stable flies were pres-
ent, especially on the legs. Animal does not fight flies as much as
do the untreated animals.

August 3, oil still present on the back, croup, and thighs. It is
very sticky. There is little or no protective action.

TWENTY PER CENT PINE TAB IN COTrONSEED OIL.'

July 15, 1913, treated a cow with 20 per cent pine tar in cotton-
seed oil. Used 5^ ounces of mixture. It was applied with a brush.
The protection was marked but not quite so effective as either 10 per
cent crude carbolic acid or 10 per cent oil of tar in cottonseed oil.
July 16, about 18 hours later, the cow fought flies as much as did
the controls. There was some oil present on the neck, back, and on
the fore legs. There was no odor of tar. There was little or no pro-
tective action evident at this time. #

A HALF-AND-HALF MIXTURE OF PINE TAB AND COTTONSEED OIL.

July 31, 1912, sprayed a calf with a half-and-half mixture of pine
tar and cottonseed oil. Used about 2 quarts of fluid. The mixture
was too thick to spray well in pump. The animal was sprayed very
unevenly and some spots were not covered. Two types of nozzles
were used, but a satisfactory spray was not developed.

August 1, there was plenty of oil present and also an odor of tar.
Tar was visible here and there on the hair. No flies were observed.

August 3, some oil was still present. There was a slight odor of
tar. A repellent action was still noticeable on the back, croup, and
thighs.

July 31, a second calf was sprayed. Used about 2 quarts, which
was not enough to cover the animal properly.

Augiist 1, there was plenty of oil present, and there was a strong
odor of tar. No flies were observed.

August 3, the oil and tar odor still present. A distinct repellent
action on stable flies was still noticeable.

REPELLENTS FOR PROTECTING ANIMALS FROM PLIES. 15

FIFTY PER CENT PINE TAR IN BEAUMONT OIL.

August 19, a cow was treated with 50 per cent pine tar in Beau-
mont oil. The mixture was applied with a brush.

August 20, the mixture had been rubbed off the sides and abdo-
men. The odor of tar was still present. The hair was rather untidy.
Flies were present only on underside of abdomen.

August 21, the cow was stiff. The mixture was still present on the
back. There was no repellent action.

SUMMARY OF RESULTS WITH PINE TAR.

It is noted from the first test made that a liberal application of
10 per cent pine tar in cottonseed oil caused the animal to look
droopy. It is probable that this was due to a toxic action of the tar.
The odor of the tar had disappeared on the second day following the
treatment. The repellent action lasted for three days. Some oil
was present five days after the treatment.

In the test in which 20 per cent of pine tar was used, the mixture
was applied with a brush and only 5^ ounces were used. The repel-
lent action was marked, but not so great as in the case of 10 per
cent crude carbolic acid or 10 per cent oil of tar. The repellent ac-
tion lasted less than 18 hours. The odor of tar had disappeared at
that time.

In the third test in which a half-and-half mixture of pine tar and
cottonseed oil was used, the mixture was applied liberally by means
of a spray pump. The repellent action lasted more than three days
in the case of both animals treated. The mixture is too thick to be
used in a spray piunp.

In the last test, in which a half-and-half mixture of pine tar and
Beaumont oil was used, the repellent action lasted less than two
days. This mixture had a detrimental effect in that it caused the
animal to become stiff.

There seems to be no danger to animals in applying tar in cotton-
seed oil for the purpose of repelling flies. In the first test there
Avere slight symptoms of poisoning, but the amount of 10 per cent
mixture applied (3^ quarts) was much more than would ever be
applied to an animal to protect it from flies.

It is evident from the second test that when a pine-tar-cottonseed-
oil mixture of moderate strength is applied in quantities such as it
is economical to use, the applications will have to be made every day
in order to provide protection.

16 BULLETIN 131, U. S. DEPARTMENT OF AGRICULTURE.

OIL OF TAR.i
TEN FEB CENT OIL OF TAB IN COTTONSEED OIL.

July 22, 1912, sprayed a calf with 10 per cent oil of tar in cotton-
seed oil. Used about 2 quarts of the mixture.

July 23, the oil was still evident. No hornflies were observed.
Stable flies were seen to light on the hair but left immediately. Some
stable flies were seen on the legs of the animals.

July 25, the odor of the oil of tar had entirely disappeared. The
hair was still oily but flies were seen to light on the oily spots.

July 29, there was no oil present.

Jul}^ 15, 1913, applied 3| ounces of the mixture to a calf by means
of a brush. The repellent action was very marked.

July 16, about 18 hours later, the calf did not fight the flies quite
so much as did the controls. There was no odor of tar. There w^as
a very slight evidence of oil on the sides and back but no repellent
action could be observed.

HALF-AND-HALF MIXTUEE OF OIL OF TAB AND COTTONSEED OIL.

August 22, 1912, sprayed a calf with a half-and-half mixture of oil
of tar and cottonseed oil. Used about 2 quarts of tKfe mixture. The
animal almost immediately began to show signs of sickness. The
eyes were half closed. The skin about the eyes, on the face, and at
the corners of the mouth was wrinkled. There was slight salivation.
These symptoms were followed by a slight swaying in the hind quar-
ters when the animal walked. Finally the gait became staggering
and the animal fell from time to time and arose again only with the
greatest difficulty.

August 26, when the next observation was made, the animal had
entirely recovered. There Avas no repellent action noticeable.

TEN PER CENT OIL OF TAB IN BEAUMONT OIL.

July 22, 1912, sprayed a calf with 10 per cent oil of tar in Beau-
mont oil. Used about 2 quarts of the mixture.

July 23, oil was present on the hair. There were a very few stable
flies on the legs. No hornflies were observed.

July 25, more oil was present on the hair than in the case of a
calf sprayed on the same date with a mixture in which cottonseed
oil served as the base.

July 29, oil was present on the back and rump. No hornflies were
observed.

''■ A sample of the oil of tar used in those exporiiuents was examined in the Biochemic
Division of the Bureau of Animal Industry and was found to contain phenols, volatile
with steam, 14 per cent.

REPELLENTS FOR PROTECTING ANIMALS FROM FLIES. 17

August 7, 1913, a calf was treated with 10 per cent oil of tar in
Beaumont oil. The mixture was applied with a brush. The repel-
lent action was marked.

August 8, no odor of tar was noticeable. The oil was rubbed off the
abdomen, the sides, and outside of the thighs. Some stable flies were
present on the legs. Only a very few hornflies were present.

FIFTY PER CENT OIL OF TAR IN BEAUMONT OIL.

August 19, 1913, a cow was treated with a mixture of 50 per cent
oil of tar in Beaumont oil. The mixture was applied with a brush.
There was a slight salivation, and the cow remained rather quiet fol-
lowing the treatment. It seems certain that there were symptoms
of phenol poisoning.

August 20, the odor of the oil of tar was still present. Only a few
stable flies were present on the legs. Other animals in the same pen
were covered with flies. The mixture had disappeared from the
sides and abdomen.

August 21, the cow was a little stiff. Oil was still present on the
back. The cow was protected very little from the flies.

SUMMARY OF RESULTS WITH OIL OF TAR.

In the first test with 10 per cent oil of tar in cottonseed oil the
mixture was applied with a spray pump. About 2 quarts of the
liquid were applied. The repellent action lasted less than three
days.

In the second test the mixture was applied by means of a brush,
and 3f ounces were used. The repellent action, which was ver}^
marked at first, had nearly disappeared at the end of 18 hours.

In the third test a half-and-half mixture of oil of tar and cotton-
seed oil was applied with a spray pump. About two quarts of the
mixture Avere used. There were symptoms of poisoning. The next
observation was made four days later, at which time there was no
repellent action.

In the fourth test 10 per cent oil of tar in Beaumont oil was
applied with a spray pump. About 2 quarts of the mixture were
used. There were no symptoms of poisoning.

In the fifth test 10 per cent oil of tar in Beaumont oil was applied
with a brush. On the following day the odor of tar had entirely dis-
appeared and the repellent action had almost entirely ceased.

In the last test 50 per cent oil of tar in Beaumont oil was applied
with a brush. The protection lasted about two days. There were
mild symptoms of poisoning and the animal became slightly stiff.

The repellent action of 10 and 50 per cent of oil of tar in cotton-
seed oil or in Beaumont oil is very marked, but when applied in

18 BULLETIN 131, U. S. DEPARTMENT OF AGRICULTURE.

such quantities as it is economical to use the action lasts less than
a day when cottonseed oil is used, and about two days when Beau-
mont oil is used. As shown by the third test, 50 per cent oil of tar
is dangerous when applied in large quantities.

The last test shows that 50 per cent oil of tar in Beaumont oil
when applied in small quantities with a brush is also dangerous.
The increase of the content of oil of tar from 10 to 50 per cent does
not seem to increase the duration of the repellent action materially,
as indicated by tests 1 and 3, but the 50 per cent Beaumont oil mix-
ture protected twice as long as the 10 per cent mixture.

For the purpose of determining whether daily applications of 10
per cent oil of tar in cottonseed oil would produce poisoning or other
imtoward results, a calf was treated with the mixture on October 2,
3, 4, 6, 7, 8, 9, 10, 11, 13, and 14. The mixture was applied with a
paint brush. No symptoms of poisoning resulted, and the skin
remained unaffected.

THE MOORE FORMULA.

October 4, 1912, a calf was sprayed with the following mixture :

Itsh oil 100 parts.

Oil of tar 50 parts.

Crude carbolic acid 1 part.

About three quarts of the mixture were used. The animal appeared
sick after being sprayed. It was restless and there was salivation.

October 7, the animal was very oily. There was present an odor
of tar and fish oil. Flies were still repelled.

July 16, 1913, a bull calf was treated with the above mixture, which
was applied with a brush, and 6 ounces were used. The repellent
action was marked. There were no sj^mptoms of poisoning.

It is noted from the first of the above tests that the application of
the Moore mixture in large quantities is dangerous. Such a liberal
application, however, would never be made in practice. The repel-
lent action was still evident on the third day. In the second test a
small quantity of the mixture was applied to a calf by means of a
brush and no symptoms of poisoning resulted.

TEN PER CENT OIL OF CITRONELLA IN COTTONSEED OIL.

June 19, 1913, a calf was treated with 10 per cent oil of citronella
in cottonseed oil, applied with an atomizer. A few hours later all
protection had ceased.

July 2, 1913, the above calf was again sprayed. An hour or so
later a repellent action was still noticeable. The calf was not trou-
bled much with flies as compared with the untreated animals.

July 3, 1913, a cow was sprayed. Used 1^ ounces. There was a
very marked repellent action, but an hour or so later this had become

REPELLENTS FOR PROTECTING ANIMALS FROM FLIES. 19

greatly reduced. There was a very slight odor of citronella at that
time.

July 10, 1913, applied the mixture to a cow by means of a brush.
ITsed about 6 ounces of oil. July 11, about 22 hours after applica-
tion, oil was present on the neck and along the back. There was
no odor of citronella. There was little or no protection as indicated
by the presence of many hornflies on the underside of the abdomen,
and the presence of many stable flies on the legs.

It is noted from the above tests that the mixture used is a powerful
repellent, but that its effect does not last more than a few hours.

TEN PER CENT OIL OF SASSAFRAS IN COTTONSEED OIL.

June 19, 1913, a mixture of 10 per cent oil of sassafras in cottonseed
oil was applied to a calf by means of an atomizer. There was a pro-
nounced repellent action which, however, had disappeared at the
end of a few hours.

July 2, 1913, the same calf was again treated. An hour or so later
a repellent action was still present. The calf was troubled very
little with flies as compared with the other animals. July 3, there
was no odor or protective action noticeable.

July 3, 1913, treated a cow with the mixture. Used about 3 ounces.
The repellent action was marked. An hour or so later the repellent
action was greatly reduced and there was no odor of sassafras.

July 10, 1913, applied the mixture with a brush to the above cow.
Used about 5^ ounces. July 11, about 22 hours later, a little oil was
present on the neck, withers, and just behind the withers. Many
hornflies were present on the front legs and on the underside of the
abdomen.

The above tests show that the mixture has a marked repellent ac-
tion, but that this only lasts for a few hours.

TEN PER CENT OIL OF CAMPHOR IN COTTONSEED OIL.

June 19, 1913, a mixture of 10 per cent oil of camphor in cotton-
seed oil was applied to a calf by means of an atomizer. A few hours
afterward some protective action was still noticeable.

July 2, 1913, the same calf was again treated. An hour or so later
the calf was still protected from flies.

July 3, 1913, no protection'was noticeable in the case of the above
calf. A cow was sprayed with the mixture. Used 2^ ounces. There
was a marked protective action. An hour or so later the protective
action was greatly reduced. There was no odor of camphor.

July 10, 1913, applied the mixture to the above cow with a brush.
Used 5 ounces. July 11, about 22 hours after application, a little
oil was present on the neck and along the back. There was no odor

20 BULLETIN 131, U. S. DEPAKTMENT OF AGRICULTURE.

of camphor. Some hornfiies were present and many stable flies were
on tlie legs.

The immediate protection rendered by the above mixture is
marked, but its action lasts only for a few hours.

HALF-AND-HALF MIXTURE OF KEROSENE AND COTTONSEED OIL.

August 7, 1913, a cow Avas treated with a half-and-half mixture
of cottonseed oil and kerosene. The mixture was applied with a
brush. The flies were repelled.

August 8, the oil was rubbed off the sides, abdomen, and the out-
side of the thighs. Very few flies were present.

KEROSENE EMULSION.

August 21, 1913, treated a cow with kerosene enmlsion made ac-
cording to the formula on page 11, diluted 1 to 8. The emulsion had
only a very slight repellent action.

BEAUMONT OIL.

August 7, 1913, a calf was treated with Beaumont oil. The oil was
applied Avith a brush. The repellent action was marked. August
S, the oil had been rubbed off the abdomen, the sides, and the outside
of the thighs. Stable flies were present on the legs. There Avas
plenty of oil present on the neck, shoulders, and back. There were
no hornfiies on the animal, although they had been numerous the
day before.

FISH OIL.

July 22, 1912, a calf Avas sprayed with fish oil. About 2 quarts of
the oil Avere used. July 23, the oil Avas present on the hair. Flies
frequently lit on the animal but left almost immediately. A feAv
stable flies were noted on the legs. No hornfiies Avere observed.

July 25, considerable oil was still present. Some flies were seen
to light on and crawl oA'er the greasy hair. There was a A^ery slight
fishy odor.

July 29, oil was present on the back and rump. No hornfiies were
observed. Stable flies were observed on the legs.

August C, rear portion of body very sticky and dirty. There was
a loss of hair in spots on the back and sides.

July 15, 1913, applied fish oil with a brush. The protection was
A'cry marked. July 16, about 20 hours later, there was an abundance
of oil present on the upper half of body, and a repellent action was
noticeable in this region. There was still a very slight amount of oil
on the legs, but it was not sufficient to keep the flies off.

In the first test with fish oil the oil was applied by means of a
spray pump. Two liters were used. The repellent action lasted be-
tween one and three days. The liberal application of the oil caused

REPELLENTS FOE PROTECTING ANIMALS FROM FLIES. 21

the hair to become sticky and dirty in places. There was also a loss
of hair. These unfavorable results were not noted in the second
test, in which a light application of oil was made with a brush.

LAUREL OIL.

June 19, 1913, a calf was rubbed with laurel oil. The protection
was very marked.

July 2, 1913, the oil was applied to a calf with a paint brush.
There was a very marked repellent influence on both the hornflies
and the stable flies. An hour or so later the repellent action was
only very slightly reduced.

July 3, 1913, the same calf was treated. Used about 2 ounces.
The mixture was applied with a paint brush. The repellent action
was marked.

July 10, 1913, applied the oil with a brush to all parts of the body
except the head. Used 5 ounces. July 11, about 22 hours later,
there was an abundance of oil present on body and neck. There
were no flies on the body and neck. Some stable flies were present
on the legs.

July 15, 1913, a severe exfoliation was noted on the shoulders and
neck. There was a slight exfoliation on the head. A similar ex-
foliation was noted on the withers shortly after the first treatment
on June 19.

August 19, 1913, a calf was treated all over with laurel oil. Appli-
cation was made by means of a brush.

August 20, there was an abundance of oil present. It was rubbed
off the abdomen. The repellent action was marked, but the odor of
the oil was not as strong as at first.

August 21, some oil was present on the back and sides. There was
a repellent action still evident.

August 7, 1913, a cow was treated with 10 per cent laurel oil in
cottonseed oil. The mixture was applied with a brush. The repel-
lent action was marked.

August 8, oil was present on the neck, shoulders, and back. It was
rubbed off the sides and abdomen. There was no odor of laurel oil.
Stable flies were present on the legs, Hornflies were present on the
abdomen where the oil had been rubbed off.

Laurel oil has a very marked repellent action on both hornflies and
stable flies. No observations were made to determine the limit of the
duration of the repellent action, but it undoubtedly as a rule con-
tinues for several days. On account of the fact that the oil has a
tendency to produce an exfoliation of the skin it should be applied
very lightly to the hair. As indicated by the last test, in a 10 per
cent mixture of laurel oil and cottonseed oil the laurel oil disappears
by evaporation in less than 24 hours.

22

BULLETIN 131, U. S. DEPARTMENT OP AGRICULTURE.

PYRETHRUM POWDBR.

Jul)'- 25, 1912, a cow was dusted with pyrethrum powder along
the neck and back. Used about 2^ ounces of powder. Flies were
observed to light frequently on the treated portions of the body and
i"emain for a time.

July 26, an attendant reported that there was plenty of powder
still present and that it seemed to repel the flies.

August 9, 1913, pyrethrum powder was applied to the skin of a
cow. The repellent action was^very marked. August 10, only a very
slight protective action was noted.

Pyrethrum powder Avhen applied to the skin of cattle has a very
marked repellent action, but this lasts only for about a day.

SUMMARY OF EXPERIMENTAL TESTS.

The experimental tests are summarized in the following table :

Summary of experimental tests.

Substance nsed.

Duration
of odor.

Duration
of repel-
lent
action.

Duration
of pres-
ence of
sub-
stance.

Method of
application.

Effect on animals.

10 per cent crude carbolic acid in cot-
tonseed oil.

Do

Do

10 per cent pine tar in cottonseed oil . . .
20 per cent pine tar in cottonseed oil . . .
50 per cent pine tar in cottonseed oil . . .

Do

50 per cent pine tar in Beaumont oil. ..
10 per cent oil of tar in cottonseed oil . .

Do

50 per cent oil of tar in cottonseed oil . .
10 per cent oil of tar in Beaumont oil . .

Do

50 per cent oil of tar in Beaumont oil . .

The Moore formula

Do

10 per cent oil of eitronella in cotton-
seed oil.

Do

10 per cent oil of sassafras m cottonseed I
oil.

Do

Do

10 per cent oil of camphor in cottonseed
oil.

Do

Do

50 per cent kerosene in cottonseed oil .

Beaumont oil

Fish oil

Do

Laurel oil

Do

10 per cent laurel oil in cottonseed oil .
Pyrethrum powder •.

Do

1-1-
2-
1-
3-1-
3+
2—
3-
1-

1-

1 +

1-
1-

1 +
3 +

l-h
2-1-
1-

1-

3-1-
1-
3-t-
34-
2-
3-
1 +
4—

1 +

3-t-
1 1'

1-
1-

1-
1-
1-

1-

1-H
1 +
3-

14-
2+
1+
1 +
1-t-

Days.

1+
5-
14-
34-
34-
24-
34-
14-

74-
14-
24-

34-

14-

14-

\ +

14-

24-
14-
14-
1 +

Spray pump.

do

Brush

Spray pump.

Brush

Spray pump.

do

Brush

Spray pump.

Brush

Spray pump.

do

Brush

do

Sprayed..

Brush

Atomizer.

Brush

Atomizer.

do.

Brush . ,

Atomizer

Brush

do

do

Spray pump.

Brush

do

do

do

Phenol poisoning.

Do.
None.

Caused depression.
None.

Do.

Do.
Caused stiffness.
None.

Do.
Phenol poisoning.
None.

Do.
Slight symptoms of
poisoning. On
second day ani-
mal was stiff.
Phenol poLsoning.
None.

Do.

Do.
Do.

Do.
Do.
Do.

Do.

Do.

Do.

Do.
Slight loss of hair.
None.

Severe exfoliation.
None.

Do.

Do.

Do.

EEPELLENTS FOR PROTECTING ANIMALS FROM PLIES. 23

GENERAL SUMMARY.

The biting flies that annoy domestic animals most in this country
are the stable fly, Stomoxys calcitrans, and the hornfly, Lyperosia
irritans. The bot flies are not biting flies, but are a menace to do-
mestic animals because of the parasitic habits of their larvae. This
is also the case with the screw-worm fly, Paralucilia macellaria,,
which deposits its eggs in wounds, and a bluebottle fly, Lucilia seri-
rata., occurring in the United Kingdom and Holland, and certain
species of Calliphora occurring in Australia, the larvae of which
invade the wool and skin of sheep.

Repellents are more or less effective against all of these flies.

Opinions differ with regard to the injury by biting flies. The
common opinion seems to be that these flies are responsible for great
losses. However, a limited amount of experimental evidence relating
to cattle seems to indicate that the losses, when they occur, are not
great.

The repellent action of certain colors has been noted by various
investigators. Light-colored animals suffer less from flies than dark-
colored ones. One author (Marre, 1908) has recorded the observa-
tion of a farmer in France who found that a blue color applied to the
inside of stables repelled flies. This observation seems to have re-
mained uncorroborated.

Potassium tellurate has been recommended by Ochmann (1911)
as an internal remedy for repelling flies. However, Mayer (1911)
failed to obtain results with the remedy, and it seems safe to assume
that internal remedies will never prove practicable in repelling flies.

Liquid repellents may be applied by means of a dipping vat, a
pail spray pump, an atomizer, or by means of a rag or a paint brush.
The method to be employed depends on the individual preference
of the farmer and the nature and cost of the preparation used.

The powder remedies that have been used are pyrethrum powder
and tobacco powder.

Various oils, emulsions of oils, and mixtures of oils are used in
repelling flies. Crude petroleum, cottonseed oil, fish or train oil,
and light coal-tar oil may be used pure. Jensen (1909) recommends
for dairy cows an emulsion of crude petroleum containing an admix-
ture of powdered naphthalin.

Fish oil is rated as one of the best repellents and has been used
alone and in combination with various other substances. Other sub-
stances that have repellent qualities and that have been used in vari-
ous mixtures are pine tar, oil of tar, crude carbolic acid, oil of penny-
royal, and kerosene.

Jensen's formula is said to protect cows for a week. The pro-
tective action of fish oil is stated to range from less than two days

24 BULLETIN 131, U. S. DEPAKTMENT OF AGKICULTURE.

( Parrot t, 1900) to six days. Moore's formula is said to protect for
two days. This mixture is safe when applied lightly with a brush,
but not when applied liberally with a pail spray pump.

Laurel oil is a very effective repellent. Mayer (1911) found that
the protection lasted from 2 to 12 days. The oil when used pure has
an irritating effect unless it is applied lightly. According to Mayer
the irritating effect may be overcome by combining it with linseed
oil in the proportion of 1 to 10. The present author found that
10 per cent of laurel oil in cottonseed oil was active for less than a
day.

A number of formulas for repellents for application to wounds
have been recommended by various authors.

In experimental tests carried out by the present author the follow-
ing results were obtained :

A 10 per cent mixture of crude carbolic acid (21.8 per cent
phenols) in cottonseed oil has a very strong repellent action on
flies, but this lasts less than a day, in consequence of which it is nec-
essary to apply the mixture every day. The mixture should be ap-
plied lightly with a brush, since a heavy application with a spray
pump is likely to cause phenol poisoning.

Mixtures consisting of 10, 20, and 50 per cent of pine tar in cot-
tonseed oil have marked repellent qualities. They should be applied
lightly and it is necessary to apply them every day. A liberal ap-
plication of a 10 per cent mixture is deleterious to animals. This
is also the case with a half-and-half mixture of pine tar and Beau-
mont oil when applied lightly wdth a brush.

A mixture of oil of tar (14 per cent phenols, volatile with steam)
in cottonseed oil and in Beaumont oil has a very marked repellent
action. A 10 per cent mixture of oil of tar in cottonseed oil is safe.
A half-and-half mixture of oil of tar and cottonseed oil when ap-
plied liberally with a spray pump and 50 per cent oil of tar in Beau-
mont oil applied with a brush are not safe. Ten per cent oil of tar
in Beaumont oil is safe. When applied lightly it is necessary to
apply 10 per cent oil of tar in cottonseed oil or 10 per cent oil of tar
in Beaumont oil every day.

Mixtures of 10 per cent of oil of citronella, oil of sassafras, or oil
of camphor in cottonseed oil are powerful repellents, but they are
active for less than a day.

A heavy application of fish oil causes the hair to become sticky
and fall out. A light application did not produce these results.

Pyrethrum powder is an effective repellent, but its action lasts
only for about a day.

REPELLENTS FOR PROTECTING ANIMALS FROM FLIES. 25

LITERATURE CITED.

Beach, O. L., and Clark, A. B.

1904. Protecting cows from flies. Bui. 32, Storrs Agric. Exper. Station,
Storrs, Conn., Dec, 14 p., fig. 15.
BiSHOPP, F. C.

1913. Tlie stable fly. Farmers' Bui. 540, U. S. Dept. Agric, Washington,
July 14, 28 p., figs, 10.
Caeltle, W. L.

1899. Protecting cows from flies. In 16th Ann. Rep. Agric. Exper. Station
Univ. Wisconsin, Madison, p. 92-96.

1904. Protecting cows from flies. [Summary of 1899, pp. 92-96.] In 20th

Ann. Rep. Agric. Exper. Station, Univ. Wisconsin, Madison, p. 105.
Delamare, M.

1908. Destruction des mouches et des moustiques par le formol. In

Archives de med. et de pharm. mil., v. 51, no. 4, April, p. 297-301.

ECKLES, C. H.

1905. Test of a fly repellent. In Bui. 68, Missouri Agric. Exper. Station,

Columbia. July, p. 35-39.
Fuller, Claude.

1913. Fly plagues. An unusual outbreak of Stomoxys calcitrans follow-
ing floods. In Agric. Jour. Union South Africa, Pretoria, v. 5 (6),
June, p. 922-924.
Garman, H.

1892. Some common pests of the farm and garden. Bui. 40, Kentucky
Agric. Exper. Station, Lexington, Mar., 51 p., figs. 28, pis. 2.
Hopkins, A. D.

1891. Department of entomology. In 3d Ann. Rep. West Virginia Agric.
Exper. Station, Charleston, p. 145-180, pis. 12-13. The horn fly,
p. 159.
Jensen, H.

1909. [Fly repellents.] In Missouri A^'alley Vet. Bui., Topeka, Kans., v. 4

(5). Aug., p. 30; note by editor, p. 30-31.
Kent, F. L.

1903. Department of dairying. [Report dated June 30.] In 15th Aim.
Rep. Oregon Agric. College and Exper. Station, [Corvallis], p.
29-33. -

LiNDSEY, J. B.

1903. Dairying and feeding experiments. In 15th Ann. Rep. Hatch Exper.
Station, Massachusetts Agric. College, Boston, Jan., p. 57-68.
Marlatt, C. L. -^

^ 1910. The horn fly (Hcetnatohia serrata Rob.-Desv.). Circular 115, Bureau
Entom., U. S. Dept. Agric, Washington, Apr. 15, 13 p., figs. 6.
[MS. dated Nov. 17, 1909.]
Marbe, Francis.

1908. Les mouches n'aiment pas la couleur bleue. In Jour, d'agric prat.,
Paris, an. 72, n. s., t. 16, sem. 2, no. 33, 13 aoflt, p. 215-216.
Mater, A.

1911. Ueber die Wirkung des tellursauren Kaliums als Fliegenmittel. In
Monatsh. f. prakt. Tierh., Stuttgart, v. 23 (2-3), 25. Nov., p. 49-50.
MooEE, E. L.

1903. Flies. In Bui. 81, South Dakota Agric. Exper. Station, Aberdeen,
June, p. 41-42.

26 BULLETIN 131, U. S. DEPARTMENT 01*' AGiilCULTURE.

OCHMANN.

mil. Kalinin tellnricuni. In Ztsclir. f. VeterinJ4rk., Berlin, v. 28 (4),
Apr., p. 193-105.
Otis, D. H.

1904. Experiuients witk dairy cows. Bui. 125, Kansas Agric. Exper.

StJitiou, Manhattan, May [issued September, 1904], p. 59-161,
pis. 1-59 [i. e., figs. 1-39].

1905. Experiments with hand-fed calves. Bui. 126, Kansas Agric. Exper.

Station, Manhattan (May, 1904), Mar., p. 163-198, figs. 1-14.
Parrott, p. J.

1900. Horsefly remedies. [Letter to editor.] In Wallaces' Farmer.
Des Moines, Iowa, v. 25 (15), Apr. 13, p. 415.
Smith, J. B.

[1889a] The horn fly {HwmatoMa scrrata). Bui. 62, N. Jersey Agric.
Exper. Station, New Brunswick, Nov. 6, 40 p., figs. 11.
Spencer, John.

1904a. The horn fly {UaiiiutoOia scrratu). In Bui. 153, Virginia Agric.
Exper. Station, Blacksburg, v. 13 (4), Dec, p. 71-77, 5 figs.

o

usPEPffiffliorAiiranii

No. 134

Contribution from the Bureau of Entomology, L. O. Howard, Chief
October 7, 1914.

(PROFESSIONAL PAPER.)

CITRUS FRUIT INSECTS IN MEDITERRANEAN
COUNTRIES.

By H. J. QuAYLE.

THE MEDITERRANEAN FRUIT-FLY.''

Ceratitis capitata Wied.

OCCURRENCE.

In the Mediterranean countries the Mediterranean fruit-fly (Ceratitis
caijitata Wied.) was first recorded from Spain in 1842, from Algeria
in 1859, from southern Italy in 1870, from Sicily in 1882, from Tunis
in 1885, from Malta in 1893, from Egypt in 1904, and from France in
1900.^ This chronology, however, does not necessarily represent the
spread of the insect, for it may have occurred in some of the countries
long before any published record appears. In addition to the coun-
tries enumerated it is also said to occur in Asiatic Turkey. In the
Mediterranean vicinity it is recorded from the Azores, Madeira, and
Cape Verde Islands. The writer has taken this insect at Valencia

1 This paper is of immediate value on account of the important information it contains bearing on the
subject of the need of regulating the entry of citrus and other fruits imported from Mediterranean countries to
prevent the entry of the Mediterranean fruit fly into the United States. The investigations embodied
in this paper were made by Prof. Quayle during the summer of 1913 as a collaborator of the Federal Horti-
cultural Board of this Department. Prof. Quayle is an expert on citrus insects and has previously made
important studies in this field in California in connection with the State experiment station. Advantage
was taken of the fact that he was proposing to use his sabbatical year to make a world-wide survey of citrus
insects to commission him to make a much-needed preliminary survey of the citrus and other fruit insects
in Mediterranean countries, more particularly in relation to the export fruit to the United States.

The fruit-fly conditions of the principal Mediterranean citrus districts was the important subject; the
report, however, includes data on other fruit insects which ought to be considered in relation to any pro-
posed regulation of the entry of fruits from countries covered.

As having an important bearing also on the possibility of the entrance of the fruit fly with Mediterranean
fruit, the investigation includes a report on harvesting and marketing conditions of citrus fruit, more par-
ticularly as to methods of picking, sorting, curing, and shipping.

This paper indicates very clearly that there is little danger of fruit-fly introduction from the lemon,
which is the main- citrus importation from Mediterranean countries. That there is some danger from
oranges and certain other fruits at particularly favorable seasons of the year has also been clearly brought
out.— C. L. Marlatt, Chairman Federal Horticultural Board.

2 Italian, Mosca della arance; Spanish, Mosca.

3 For these and other facts, including a full bibliography of Ceratitis capitata, see Quaintance, A . I.. , U. S.
Dept. Agr., Bur. Ent., Circ. no. 160,25p., 1 fig., Oct. 5, 1912.

51981°— Bull. 134—14—1

k

2 BULLETIN 134, U. &„ DEPARTMENT OF AGEICULTUKE.

and Barcelona, Spain (also punctured oranges in tlie London markets
from Murcia, Spain), at Marseille, France, throughout southern
Italy and Sicily, and punctured oranges in the markets of Jerusalem,
Palestine.

FOOD PLANTS AND INJURY.

In Spain, during July, 1913, the Mediterranean j[ruit-fly was found
in peaches and oranges, but in very limited numbers. The extent of
infestation in peaohes, its favorite food, amounted to only a fraction of
1 per cent. It is true that most of the peaches had not yet matured,
and there is no doubt that a heavier infestation occurred later in the
season. Many of the pears, apples, and other fruits were examined,
both in the market and in the field, but none was found infested at that

Fig. 1. — The Mediterranean fruit-fly {Ccratitis capilata): a, Adult fly; 6, head of same from front; c, spatula-
like hair from face of male; d, antenna; c, larva; /, anal segment of same; g, head of same, a, e, Enlarged;
6j J,/, greatly enlarged; c, d, still more enlarged. (From Howard.)

time. Figs, which would probably be infested, were immature, as it<
was then in the period between the first and second crops.

During the month of March an extensive examination of oranges
in the field and in packing houses was made, but at that season
none was infested. It was learned that occasional complaints of in-
fested oranges occur at the close of the shipping season during the
last of Jmie and the first of July, and again in a few of the earlier
ripening fruits in October. When the section was again visited, in
July, all of the crop was harvested, but scattering fruits on the trees
and on the groimd were common. These would be the ones likely to
be infested were the fruit-fly present. After a week's examination in
the groves around Valencia, only four oranges were found with the
larvsB (fig. 1, g) of the fruit-fly. It is probable that the fly was unusu-
ally rare in 1913, because no complaint of infested fruit was recorded

CITKUS FKUIT INSECTS IN MEDITERRANEAN COUNTRIES. 3

from any of the late shipments, and also because of the extreme
scarcity of the fly as found by the writer in other fruits, as well as in
oranges.

In Sicily Ceratitis capitata has been reared by the writer from the
following fruits: Apple, azarole, fig, Indian fig, lemon, mandarin, nec-
tarine, orange (sweet), orange (bitter), peach, pear, and plum. Of
these fruits the peach is the most severely infested. This is particu-
larly true of the late peaches in August and September. In many
places much of the fruit as it approached maturity was attacked. As
a consequence most of the fruit is picked rather green and not so many
of the infested fruits find their way to the markets. In some sections,
however, the fruit-fly was not so abundant in the field, and it was pos-
sible to get a good percentage of sound, mature fruit. Wormy fruit
was supposed not to be sold in the markets of Palermo, and this was
enforced by a few 50-lire iuies. After the first few days following the
hatching of the larvae infested peaches are readily distmguished, and
the writer was able to get all the infested fruit necessary for experi-
mental purposes from the Palermo markets.

All of the peaches met with in Sicily were clings and of a very firm
texture. The preponderance of such a variety may be due to the
fact that such fruits do not break down so readily from the attacks of
the fly. Figs are also more or less infested, but to no such extent as
the peach, and the loss to the figs was very little. Most of the figs are
picked for drying while they are still firm, and few in this condition
contained larvae. Plums and apples were rarely infested, while a few
larvae were found in pears. The pears of Sicily are likemse of soUd,
firm texture, there being no Bartlett or other representatives of our
better varieties. Indian figs, a very common fruit in all parts of Sicily,
were not infested until September, and then only a small percentage.
It was not difficult to find azaroles contammg larvge, but the greater
percentage of them was sound.

Aside from a few localities where considerable injury is done to the
peach, the fruit-fly is not a very destructive pest in Mediterranean
countries and fruit continues to be grown successfully in spite of its
presence. In these countries, too, it should be noted, the growers
have httle knowledge of the insects mfesting their fruit, mth the
exception of one or two species, and they do not, as a rule, practice any
measures for artificial control. The writer knows of r.o case where
the culture of any fruit in these countries has had to be abandoned
because of the destructiveness of the Mediterranean fruit-fly. While
this insect was on two or three occasions, during his sojourn in the
Mediterranean vicinity, served to the writer through peaches at the
table, codhng-moth-infested apples and pears formed a regular part of
the menu in comparison. These statements are made with no pur-
pose of minimizing the importance of the pest.

4 BULLETIN 134, U. S. DEPARTMENT OF AGEICULTURE.

INFESTATION OF ORANGES.

Oranges were not found infested mth the fruit-fly during April and
May. By the end of May oranges are almost entirely off the market
in Sicily. Much orange fruit was examined during April and May,
both on the Island of Sicily and on the mainland, but no infestation
was found. In Calabria and at Messina oranges were seen with fruit-
fly punctures from the previous season, but no larvse were present.
The eggs failed to hatch or the larvae died immediately upon hatching
without getting beyond the egg cavity. Accordijig to Dr. Martelli,
entomologist at Messina, who has given considerable attention to
the fruit-fly, oranges may usually be found infested by the 1st of June,
but none was found with living larvse anywhere, to the writer's knowl-
edge, up to the second week in June of 1913.

When the writer returned to Sicily on the 1st of August such ripe
oranges as were still on the trees or on the ground were heavily
infested with the fruit-fly (PL I, fig. 2). Indeed, no oranges could
be found that were either not infested or did not show punctures.
For some reason unaccounted for, a few oranges among an almost
complete infestation wiU show from two or three to a dozen punc-
tures, yet will remain sound and contain no larvse. One orange taken
late in August contained the remarkable number of 118 larvae. (PI. I,
fig. 5). These were mostly fuU grown, and the orange was below
medium size. The pulp alone did not furnish sufficient food for such
a number, so many of them had retreated to the denser rind, and it
was necessary to cut this into very small pieces to disclose the larvse,
which were concealed in small burrows. This orange, before it was
cut, was firm and undecayed.

The usual number found in oranges varied from 6 or 7 to 15 or 20.
In peaches there were about the same number, but occasionally as
many as 30 or 35. In figs usually from 3 or 4 to 8 or 10 were found,
while in azaroles and plums, which are smaller, from 2 or 3 to 5 or 6
would be the usual numbers.

Both the sweet and bitter oranges were infested. The bitter
orange, therefore, at least as it occurs in Sicily, is not objectionable
as food to the fly. The pomelo, or grapefruit, is very rare in Sicily, as
elsewhere in Europe, so that a fair test of possible infestation was not
presented: A few old grapefruit, however, occurring on three or four
trees that adjoined orange trees on which aU the fruit was infested,
showed no larvae or punctures. Mandarins are, of course, commonly
infested. (PI. I, fig. 4.) Occasional ones, apparently remaining
over from the previous year, were collected as late as August, and
these were in nearly all cases infested.

The first oranges of the crop of 1913 with fruit-fly punctures were
seen about the middle of September. Tliis fruit had begun to turn
yellow over a small area on one side, and the punctures were in this

Bui. 134, U. S. Dept. of Agriculture.

Plate I.

.jiSifumit, <ii««^

vV

Damage to Citrus Fruits by the Mediterranean Fruit Fly.

Fig. 1. — Lemon infested with Ccratitia capitata. Fig. '2. — Orange infested with C. capitata.
Fig. 3. — Lemon infested with C, capitatd. Fig. 4. — Mandarin infested witli C. capitata.
Fig. 5.— 118 larvae of Ceratitis capitata from a single orange. All from Sicily. (Original. )

CITRUS FRUIT INSECTS IN MEDITERRANEAN COUNTRIES. 5

yellow area. The adult flies (fig. i, a) were commonly seen walk-
ing about on the fruit looking for a suitable place for oviposition. By
the last of September the fly was seen in considerable numbers where
the fruit was beginning to ripen. In wSicily up to the last of September
it was but rarely that a tree would be found with any of the fruit show-
ing yellow. An occasional orange would be seen at this time almost
entirely yellow, but these were not mature, for they were still very
sour. Punctures were common on such fruit, as well as on some
others almost entirely green, and as many as a dozen punctures were
often seen in a small yellow area. Possibly the punctures were partly
accountable for the yellowing. The flies were seen more commonly
on the trees during the morning and evening. In the rearing cages
during the hot weather they remained on the ground or out of the
direct sunlight during the middle of the day.

A large number of punctured oranges were examined during the
last of September. Not a single one was actually found infested
with the larvae. Ninety per cent of the punctures examined either
contained no eggs or larvae, or contained eggs that had failed to hatch
or larvae that were dead. The remainder contained eggs but recently
deposited, or young larvae that had just hatched and were still within
the egg cavity. The reason for the absence of eggs in many of the
punctures is probably that the fly, after making the puncture, found
conditions unsuitable for oviposition. The presence of shriveled eggs
or dead larvae, in the egg cavity must be due to the immaturity of the
fruit. In a large majority of cases the eggs had hatched; in fact,
only a few unhatched eggs were found.

In immature oranges there is often a formation of gum about the
puncture. Green oranges were known to have punctures, in some
cases, by the presence of small globules of gum on the surface. When
these oranges were taken from the tree and opened they were found
to contain eggs, or larvae that had just hatched. Very soon a yellow
spot occurs about the point of puncture, and the gum upon harden-
ing is easily removed, and probably soon falls off naturally. A hard,
gummy, granular tissue also forms around the egg cavity, and it is
often possible to remove this ball of brown tissue with the egg cavity
intact. It was at first thought that the formation of this tissue, by
furnishing an impenetrable wall around the egg cavity or by com-
pressing the eggs and larvae within, was the direct cause of the insect's
mortality. But this hard tissue is not- formed to any extent before
the eggs hatch. In practically all cases where living young larvae
were found, which indicated recent, oviposition, the surrounding tissue
was not appreciably hardened, although the brown color began to
show.

The egg cavity is situated in the spongy layer of the rind, just below
the outer covering containing the oil cells. The surrounding wall of

6 BULLETIN 134, U. S. DEPARTMENT OF AGRICULTURE.

gum seems to be formed from the outer layer, but soon extends into
the spongy tissue and entirely surrounds the egg cavity. The number
of larvae found in the punctures in September was always large —
from 20 to 30 or 40. Larvae were seen closely massed together in the
egg cavity, but although appearing perfectly normal they were inac-
tive. In such cases death had occurred recently, for later they be-
came brown and shriveled. Occasionally one or two would be seen
to move slightly. In some cases two or three larvae had made their
way out of the egg cavity and penetrated a short distance into thS
spongy tissue. In no case, however, was the pulp reached. Why the
larvae perished within the egg cavity or soft spongy tissue is not
definitely accounted for. It appears to be because of lack of air or
through the action of some substance in the rind.

A large majority of the punctures in green oranges were seen to be
entirely sealed by gum. The tendency of citrus fruits, or, in fact, any
fruit, to exude gum to repair wounds while they are immature, is well
known. The condition of the larvae in the egg cavity — simply dying
massed together as they hatched, with no evidence of any attempt to
migrate — may indicate suffocation. While many larvae occur in a
single cavity, and the space is well occupied, death can hardly be
accounted for through compression by growth of tissue or gum forma-
tion, because some of them, at least, could work their way out of the
cavity. In cases where living larvae were found, from 30 to 40 were
seen in a single cavity with plenty of opportunity for migration.

That fruit-fly larvae require considerable air was shown in the case
of those that were transferred into a juicy lemon, where the entrance
was completely closed by the posterior tip of the bodies of a half
dozen or more of the larvae. Numerous instances of the death of
full-grown larvae have been noted to take place in the exuding juices
of fruit in glass jars. In peaches and other fruits, also, there are holes
in the outer epidermis, made at first through oviposition and later
enlarged and serving for the entrance of air.

Fruit-fly larvae appear to live largely in decayed tissue; that is, the
decay induced by them seems to precede the progress of the larvae.
It is possible that in green fruit this decay is not so readily induced.
And here, again, the organisms of decay may be kept entirely out
of the fruit if the entrance to the surface is effectually closed.

On September 24, 1913, 25 living young larvae that had just hatched
were taken from an egg cavity of the greenest orange found infested and
placed through a hole in the rind into the pulp of the same orange.
In another orange, also very green, a hole was made connecting the
egg cavity with the pulp without disturbing the young larvae in the
cavity. In both cases openings were left to the surface. Wlien the
fruit was examined on October 3, partly grown larvae were found in
both of the oranges mentioned. Only a small percentage, however,

CITRUS FRUIT INSECTS IN MEDITERRANEAN COUNTRIES. 7

had. lived, although the number was sufficient to indicate that the
pulp of the orange was not too green or too acid to serve as food.
These oranges were perfectly green, there being no yellow whatever
on one and only a slight tinge over a small area on the other. The
inabihty of the larvae to reach the pulp seems, therefore, to be due
to an injurious substance in the rind, to lack of air, to decay, or to
all three combined.

From examination of oranges in Italy, Sicily, and Palestine, as
they are maturmg in the fall, there appears to be no possibility of
infestation until the fruit reaches maturity, even though eggs of the
fruit-fly may be deposited. The practical bearing of tais fact is im-
portant in gi"eatly limiting the season of infestation. And in the
Mediterranean countries visited, cold weather appears by the time
the fruit is mature and susceptible to infestation, so that the season
is very short in the autumn, and most of the fruit is harvested
before the return of warm weather in the spring.

APPEARANCE OF FRUIT-FLY PUNCTURES IN ORANGES.

Immediately after the adult fruit-fly has oviposited in the orange
the puncture is not readily distinguishable, but it soon appears as a
brown or grayish, oval-shaped area about 0.5 mm. long, with a crack
or opening in the center. In green oranges the area immediately
around this may be yellow. Later this area may become brown and
depressed. After some time also the point of pmicture is indicated
by a distinct conical elevation. These elevations are conspicuous on
the surface of the fruit and they may at once be diagnosed as indi-
cating punctures of the Mediterranean fruit-fly. In older fruit these
conical elevations may arise from circular depressions which are of a
brownish or yellowish color. If the outer layer containing the oil
cells be cut away, the egg cavity will be disclosed m the spongy tis-
sue. After some time brown and hard granular tissue usually sur-
romids the egg cavity, so that the whole may be removed from the
surromidmg tissue as a gall. To make sure that punctures are pres-
ent the egg cavity should be exammed for the egg skins, shriveled
eggs, or larvae. If the orange is infested, small burrows may be
traced through the spongy layer to the pulp, and the pulp itself will
be decayed. Typical pmictures are at once distinguished, but their
character and form vary so greatly that sometimes other scars or
abrasions on the fruit may be mistaken for them.^

INFESTATION OF LEMONS.

The only supposed instance recorded of the occurrence of C€r&-
titis caintata in lemons in Sicily is a note by Prof. Inzenga in the
Annali di Agricoltura Siciliana, Volume XIV, 1884, page 101. In

1 Since the foregoing was written the writer has examined fruit-fly conditions in the Hawaiinn Islands,
where they are strikingly different from those in Mediterranean countries. The most evident difference
in appearance of the fruit in Hawaii is the much more copious exudation of gum.

8 BULLETIN 134, U. S, DEPARTMENT OF AGRICULTURE.

this article Prof. Inzenga simply states that a ''small worm" was
observed b}^ Profs. Alfonso and Bonafede to breed in the orange,
lemon, Indian fig, and other varieties of fruit. Prof. De Stefani,^ of
the Universitate di Palermo, questions, and rightly so, the authen-
ticity of the statement, addmg as proof that in all the writings of
Profs. Alfonso and Bonafede no statement occurs to the effect that
Ceratitis capitata breeds in lemons. Prof. De Stefani further calls
attention to the fact that no entomologist (excepting the questionable
case above) has ever observed Ceratitis to breed in lemons in Italy;
and concluded with the statement that "It is excluded absolutely
that Ceratitis capitata lives in the lemons in Sicily." (E. da excludersi
assolutamente che la Ceratitis capitata viva nei lemoni di Sicilia.)

Dr. G. Martelli, who has made careful studies on Ceratitis capitata,
published an article entitled "La Mosca della arance non vive nei
nostri limoni" (The orange fly does not breed in our lemons), in the
Giornale di Agricoltura Meridionali, No. 9, Ann. V, 1913, Messina.
In a paper read before the R. Scuola Superiore di Agricoltm'a at
Portici in January, 1913, Dr. Martelli records experiments in at-
tempting to transfer the eggs of Ceratitis into the lemons. These ex-
periments all resulted negatively, and he concluded that the insect
would not live in lemons.

During April and May an extensive examination in all the sections
of Sicily was made in the field, as well as in numerous field and ex-
porters' packing bouses, with the result that no evidence of infested
lemons was found. This was the season when the heaviest shipments
were being made to the United States, and it was felt that a thor-
ough examination should be made at that time. But at that season
no fruit-fly larvae appeared in any other fruit, and thus negative evi-
dence under such cii-cumstances would be of little value. Conse-
quently it was proposed that the inspection be continued at a later
and more favorable season, and this was at once agreed to by Mr.
Marlatt, chairman of the Federal Horticultural Board. Accordingly
the writer returned to the Island of Sicily, where he remamed through-
out August and September.

As already intimated, ther^ was abundant evidence of the presence
of Ceratitis capitata in other fruits' at that time. Field inspection
was therefore resumed in the lemon groves of Sicily during the fii'st
week in August, and during the second week there was found the
first evidence of the breeding of Ceratitis capitata in lemons. (PL I,
figs. 1, 3.) The infested lemons were large, overripe ones, with more
or less decay, and were found on the ground. The total number
found during the week was four, aU taken in the same grove. Near
by were many old ripe oranges severely infested with the fly. The
week following 10 more infested lemons were found; most of these

1 Intorno ad Alcuni Insetti degli Agrumi del Prof. Teodosio De Stefani, Palermo, p. 6, 1913.

CITRUS FRUIT INSECTS IN MEDITERRANEAN COUNTRIES. 9

were taken in this grove, but four were taken in three other places.
Two out of the 10 taken during the week were on the tree, while the
remainder were on the ground. It should be stated that the two
taken from the tree were also partly decayed on one side. The
decay in most of these lemons appeared not to be due entirely to
the fruit-fly. No puncturas were seen, and it is assumed that the
eggs were deposited in the decayed side, or else the decay which set in
later completely obliterated the punctures. One more lemon with
fruit-fly larvae was found during the fifth week, making a total of
15 infested lemons out of the thousands examined. None was
found during the remaining three weeks of the inspection. None of
the infested lemons would have been considered for shipment, and
with three or four exceptions would not have been taken for the by-
product factory. In some of the lemons, it is true, the larvse were
nearly grown, and the condition of the fruit can not be vouched
for at the time of o^dposition, but in others the larvse were but
partly grown, and thus the fruit had not been long infested.^

EXPERIMENTS WITH THE FRUIT-PLY.

Through the kindness of the Prince of Galati use was had of a
neglected garden within the city of Palermo, and under a tree
here was equipped an improvised laboratory. (PI. X, fig. 5.) Three
series of experiments wore carried on. The first series was to deter-
mine if it is possible to transfer the larvae of Ceratitis from other
fruits into the lemon and bring them to maturity. The idea was
generally held in Italy, even by the entomologists, that the lemon
is too bitter or acid for the fruit-fly. The second series was to
determine the possible extent of oviposition on lemons in confine-
ment, and the third as a check on the second series and for life-
history work, and to determine the extent of breeding in other fruits,
as the apple, pear, peach, and orange, under the same conditions.

To summarize briefly, the first series of experiments resulted in
establishing the fact that it is possible to transfer fruit-fly larvse
from a fine ripe peach to a ripe and also to a perfectly gTeen lemon
and bring them to maturity. The second series, so far as the experi-
ments were conducted in small glass containers, resulted negatively.
The third series resulted in securing oviposition and development
in the peach, pear, and orange.

In the first set of experiments a small plug was cut out of the rind
of the lemon, and a small cavity made in the pulp, just large enough
to contain the larvae. After the larvae were transferred, the plug
of rind was replaced, a small triangular piece first being cut out
of one side of the plug for air. Aseptic methods were employed

> In Hawaii a perfectly sound lemon has been seen with a single specimen of Ceratitis capitata. In Hawaii,
also , Ceratitis punctures in lemons are ^ery common, though actual infestation seems to be rare.

51981°— Bull. 134—14 2

10 BULLETIN 134, U. S. DEPARTMENT OF AGRICULTUEE.

in these operations, although not mth entire success, to prevent
infection from molds, which gave considerable trouble. In 12 experi-
ments 163 larv8B were transferred into lemons, and 108, or 66.2
per cent, changed to pupse and emerged. The time spent in the
lemons varied from 2 to 10 days, with an average maximum of 7.7
days.

The length of the larval period was determined as 10 to 11 days.
On this basis the age of the larvte transferred varied from 1 or 2 to
10 days. It will be noted that not all the larvae developed, 33.8
per cent havipg died from one cause or another. Ths molds in the
fruit were probably the chief factor in the mortality. The exuding
juice drowned a good many that were emerging for pupation, others
were dead in the fruit, and possibly some were injured in the transfer.
Enough, however, emerged to show that the lemon is not an impos-
sible food for the larvae of Ceratitis capitata.

In each of 48 glass jars from 1 to 2 lemons were placed and
from 6 to 22 flies liberated. These were fed with sweetened water,
and lived from 3 to 26 days, the large majority, however, djang
after 6 or 7 days. No infested lemons resulted from these experi-
ments and no punctures were found. Under the same conditions
peaches, pears, and oranges became infested, but with these some
of the experiments also resulted negatively. Apples in three jars
were not infested. In only a few cases were flies seen in copulation,
and it appeared that they were too closely confined and under too
unnatural conditions for free breeding.

In four large breeding boxes, where infested fruit was placed on
the ground and the flies allowed to emerge, a total of 56 lemons in
all stages of ripeness was placed. In 2 of these boxes the fruit
was first punctured with a needle or scalpel, and m the other 2
the lemons were sound. Some of the lemons remamed in these
boxes for 6 weeks. Hundreds of flies emerged in each of the boxes.
The lemons, when examined, were in various stages, many being de-
cayed. No infested fruit was found, and no punctures of the fruit-fl.y
were seen in any of the lemons.

While these experiments were not, of course, extensive and ade-
quate enough to establish any fact on negative evidence alone, they
do show that oviposition in the lemon in Italy is not at all common.

PUPATION.

Ordinarily fruit-fly larvae go into the soil to the depth of about
an inch, or otherwise seclude themselves for pupation; but this is
not at all necessary, and pupation may occur anywhere in the open
and direct light. The side of a packing box or any other container
of fruit is thus suitable for the purpose, and the fruit-fly may be
transported in this manner.

CITRUS FRUIT INSECTS IN MEDITERRANEAN COUNTRIES. 11

LIFE CYCLE.

No extended life-history studies were attempted or possible m the
time available, but such records as were kept indicate that the life
cycle of Ceratitis is completed in 22 or 23 days in Sicily in August.
Out of this total, 2 or 3 days are required for the eggs to hatch, 10
or 11 days for the development of the larvae, and 10 days for the
pupal period. Since these records were made during the warmest
weather they represent the minimum time for development.

OTHER INSECTS IN ORANGES AND LEMONS LIKELY TO BE MISTAKEN
FOR THE MEDITERRANEAN FRUIT-FLY.

The commonest insect occurring in decayed or overripe oranges
and lemons on the ground, and also occasionally on the tree, is a
nitidulid beetle, CarpopJiilus dimidiatus Fab. Larvse and adults of
this beetle often occur in great numbers. Usually decay has already
set in before the fruit is attacked, but if it remains on the ground
for some time the beetles will bore through the rind and they them-
selves cause decay. The appearance of such fruit is very much like
that infested by Ceratitis. The larva of Carpophilus is about the
same length as that of the fruit-fly, but is easily distinguished because
it is beetle-hke and both ends are tipped with brown. Instead of
breaking down, lemons often dry with extremely hard, firm rind,
and they remain in this condition for months. Such lemons occurring
on tho ground are, however, frequently infested mth this beetle. The
beetle enters tho fruit where it rests on the ground by drilling holes
through the firm rind.

Ajiother common ''worm" in decayed oranges and lemons is the
larva of a fly, Lonchaea splendida Loew. This larva is more slender
and of a paler color than that of the fruit-fly, but small specimens
are very likely to be mistaken for fruit-fly larvse; hence they must
be examined closely and identified by the spiracles to make sure of
the species. The adult fly is smaller than Ceratitis and is of a me-
talHc blue color.

Larvae of Drosophila also frequently occur in decayed oranges and
lemons, but, except in possible cases of very small specimens, they
are easily distinguished from the more robust and yellowish white
Ceratitis larvae. Of all the ''worms" infesting oranges and lemons,
Ceratitis larvae are the most sluggish and slow moving, so that
with a little experience they may be distinguished by their move-
ments.

12

BULLETIN 134, U. S. DEPAETMENT OF AGRICULTUKE.

THE BLACK SCALE.^

Saissetia oleae Bern.

DISTRIBUTION AND INJURY.

The black scale is generally distributed throughout the Mediter-
ranean citrus sections. (Fig. 2.) It varies in numbers from an occa-
sional scale to numerous specimens forming a complete incrustation on
the twngs and branches, and in injury from an insect of no commer-
cial importance to one doing much damage through the quantity of
sooty-mold fungus found on the trees and fruit.

In the most important orange section of the Mediterranean
countries, that of Valencia, Spain, the black scale is, according to our
standards of judging, entitled to rank first among the citrus fruit pests.
This statement is at least true for the years 1912 and 1913. In all of
the scores of packing houses visited during the month of March, 1913,

X /?epresen^s f/?e mons /mpor/eynf
cZ/rc/s sec f /ens of^ //le fi^e^//erra/?earj Pe^/or?

Fig. 2.— Distribution of insect enemies of citrus fruits in Mediterranean countries. (Original.)

from a half dozen to 15 or 20 women were seen washing fruit to remove
the sooty-mold fungus occurring as a result of black-scale infestation.
In some cases the sooty mold was due to the mealy bug {Pseudococcus
citri), but infection from this source would amount to only a small
percentage of the total. During July, 1913, when the section was
again visited, numerous young were seen on the leaves, which, barring
a heavy mortality later, would furnish the same conditions for the
season following. In numerous groves around Burriana, Spain, the
sooty-mold fungus was seen to form a complete coating over all the
upper surface of the leaves, branches, and fruit, and such a severe
incrustation of scales occurred as actually to kill many of the smaller
twigs, and in some cases even the larger branches.

The greatest injury from the black scale was seen in the ** Plana,"
or level district opening to the sea north of Valencia, and centering
around Burriana. The conditions here are much the same as in the

' Spanish, Escania negra; Italian, Cocciniglia dell' olivo.

Bui. 134, U. S. Dept. of Agriculture.

Plate II.

Fig. 1.— The Black Scale iSaissetia oleae) on Lemon Twig, Sicily. (Original.)

Fig. 2.— a Common Citrus Scale (Parlatoria zizyphus) on a Lemon Leaf, Sicily

(Original.)

SOME SCALE INSECT ENEMIES OF CITRUS FRUITS IN SICILY.

CITRUS FEUIT INSECTS IN MEDITERRANEAN COUNTRIES. 13

coast counties in southern California, where the same scale is most
important as a pest. The "Ribera," or section south of Valencia, is
Lilly and rolling and is separated from the sea by hills and mountains.
The direct sea influence is, therefore, not so pronounced, and the
black scale is .not so generally injurious. The influence of the sea
consists m moderating the effect of the summer heat, which, if too
intense, results in a wholesale mortality of the young scales, in which
stage the scale is largely found durmg the summer months.

The black scale is also more or less abundant in localities farther
south, as Murcia, Malaga, and Seville. But in these sections, which
are still farther removed from the sea, the black scale is not so im-
portant a pest as is Crysomphalus dictyospermi.

The washing of oranges in Spain consists in rubbing each individual
fruit, first in wet, and then in dry sawdust, the latter both to hasten
the drying and to complete the cleaning. It is not a bad system so far
as results are concerned, and, with the low price of labor (20 cents a
day for women), the expense is no greater and probably much less
than with the use of macliinery as with us. The sawdust method,
however, leaves more traces of the mold in the smaU depressions of
the fruit than does our machine with brushes. When attention was
called by the wi'iter to the absence of any aseptic agent in the water
used in dampening the sawdust — and it is used over and over again —
the reply was evoked that there is no better disinfecting agent than
ordinary sea water. But the wi'iter was not sure that sea water was
being used, and he was very certain it was not in many places. The
amount of fruit receiving the sawdust treatment varied from 25 per
cent to more than 90 per cent in most of the packing houses visited.

The washing of the fruit, according to Spanish standards, is
regarded simply as one of the regular practices of the paclring house,
and is not an expense generally attributed to the black scale or any
other insect. In fact, no one was seen in Spain who considered that
the sooty-mold fungus - was in any way related to the black scale.
It was for this reason that the statement appears at the beginning of
this discussion that the black scale is considered by the writer to be
the most important pest in the Valencia section, "according to our
standards." According to Spanish standards it is no pest at all,
chiefly because the insect and its important effect, the sooty-mold
fungus, are not generally considered as in any way related.

But the injury by the black scale in the Valencia section is not
due entirely to the presence of mold on the fruit. Wlien such severe
infestations occur as were frequently seen, the tree itself suffers.
Small twigs are killed, and the coating of mold over the leaf, brar.ch,
and fruit not only interferes with the functions of the tree, but the
fruit itself is deficient in sweetness and flavor.

1 Spanish, Neyrilla.

14 BULLETIN 134, U. S. DEPARTMENT OF AGEICULTURE.

In Sicily the black scale was seen in great abundance in several
places, but these places usually consisted of but a small area, or even
but a few trees. (PI. II, fig. 1.) It is found in scattering numbers
throughout the citrus area, but with the exception of a few cases of
dirty fruit which have been seen, coming from limited areas, as noted
above, the black scale is not a serious pest in this, the most important
lemon section of the Mediterranean. It is the writer's opinion that,
above all other factors, the absence of the scale in serious numbere in
Sicilj^ is due to the sirocco, which frequently prevails there during the
summer and fall. This is a burning hot, dry Avind from the African
deserts. It is only necessary to experience one of these siroccos,
which usually lasts about three days, to conclude what effect it would
have on insects not well adapted to withstand heat and dryness.
Opportunity was afforded for judging the effects of a sirocco on
young black scale in Sicily, with the result that between 95 and 100
per cent were seen to be killed. The same effect of hot weather has
been observed by Mr. C. L. Marlatt,^ Mr. R. S. Woglum,^ and the
writer ^ in Cahfornia.

SEASONAL HISTORY.

So far as could be observed the black scale has very much the same
life and seasonal history in Mediterranean countries as it has in Cali-
fornia. The majority of the young appear in June and July. These
settle almost entirely upon the leaves or on the tender twigs. It is
during this period that high temperatures are likely to cause a heavy
mortality. Later in the fall the young that still survive migrate to
their permanent abode on the t\vigs and branches, and pass the
winter as partly grown insects. During this season growth is very
slow, but with the resumption of warm weather in the spring it pro-
ceeds rapidly. By May and June oviposition occurs, and from 2,000
to 3,000 eggs are deposited by a single female during a period of
from 30 to 60 days. Wliile the majority thus mature in the spring
and require 8 or 10 months for development, othei*s, that have all the
heat of summer, mil mature in 4 or 5 months, and thus some scales
will be found in all stages at all seasons.

NATURAL ENEMIES.

The most important natural enemy of the black scale in most
sections where it occure is Scutellista cyanea Motch. It was a sur-
prise, however, to find that this parasite occurred in less numbers in

1 Marlatt, C. L. Insect control in California. U. S. Dept. Agr. Yearbook for 1S96, p. 217-236, PI. V,
1897. See p. 218.

2 Woglum, R. S. Fumigation inve.stigations in California. I'. S. Dept. Agr., Bur. Ent., Bui. 79, 73 p.,
28 figs., June 11, 1909. See p. 12.

3 Quayle, 11. J. The black scale. Cal. Univ. Coll. Agr. Expt. Sta. Bui. 223, p. 151-200, 24 figs., 8 pi.,
July, 1911. See p. 165.

CITRUS FEUIT INSECTS IN MEDITERRANEAN COUNTRIES. 15

many of the Mediterranean countries than it does in CaUfornia. In
those countries where no artificial control is practiced it was thought
that all natural enemies would be more abundant. On the other hand,
no place was seen where the numbers equaled those of the Cahfornia
citrus belt, mth a possible exception in the case of Ceroplastes rusci L.
on the fig, in a few places in Sicily. In Spain, where the black scale
was so abundant on citrus trees, very few were attacked by Scutel-
lista. Wliere counts were made the maximum did not exceed 20 per
cent, while hundreds of scales were examined in many places with no
evidence at all of parasitism. Scutellista, hke most insects, has its
periods of increase and decrease, and the year 1913 may have been
at the end of a depression. But during years when it occurs in
fewest numbers in southern California it is much more abundant
than it was observed to be in Spain in 1913. In Sicily, also, Scutel-
lista was not seen in large numbers anywhere on the black scale on
citrus trees.

Aside from Scutelhsta the only other enemies of any importance
noted were two coccinellids, CTiilocorus hipustulatus L. and Exochomus
4-pustulatus L. These, however, are general feeders, and were seen to
occur more abundantly on trees infested with CTirysoraphalus dictyo-
spermi, Parlatoria zizyphus, and LepidosapTies heckii than on those
infested by the black scale. Rhizohius ventralis Er., the most im-
portant coccinellid on the black scale in California, was not seen in
Spain or Italy.

CHRYSOMPHALUS DICTYOSPERMI Morg.'

DISTRIBUTION AND INJURY.

CJirysompJialus dictyospermi is found in most of the citrus sections
of Spain. It was commonly observed at Malaga, Seville, Murcia,
and Valencia. In the Valencia section it was most injurious at
Piaporto, Picana, and Piug. At each of these places fumigation,
introduced by Mr. R. S. Woglum, of this bureau, was seen in prac-
tice. Hero the scale occasioned severe injury to the trees, mostly
through the dropping of the leaves. Wliile it was observed in scattering
numbers around Burriana, nowhere was it seen to do any important
injury. Why it does not occur there in greater numbers is not
known. It was thought that parasites must be at work, but prac-
tically no evidence of parasites was seen, so far as examination
was raade during the month of March. That this scale was not
recently introduced in the Burriana district appears to be indi-
cated from the fact that it occurs there over such a large area. This
scale was also seen occasionally around Alcira in the ''Ribera."

I Spanish, Piojo rojo; Valenciana, Poll roig; in Murcia and provinces of Andalucia, Cochinella rojo; Italian,
Cocciniglia bianco-rosso: Sicilian, Bianca-russa.

16 BULLETIN 134, U. S. DEPARTMENT OF AGRICULTURE.

If this scale occurred widely over the Valencia section in such
numbers as at Piaporto, Picana, and Piug, it would, of course, out-
rank the black scale in destructiveness. At the points mentioned
it is the most serious of all the scales because of its damage to the
tree, as well as its effect on the market value of the fruit. It occurs
also in injurious numbers farther south, as at Murcia, Malaga, and
Seville. It is very commonly seen on the fruit in the markets in
these sections, and the trees in many places show the effect of the
scales. Even in the famous Patio de los Naranjos (Court of Oranges)
of the mosque at Cordova and of the cathedral at Seville the trees
are having a hard struggle to exist on account of the severe infesta-
tion by this scale. Taking the entire citrus area of Spam this scale
may be the most important, but in the important commercial section
of Valencia, where 90 per cent of the crop is produced, it is first only
in a few small areas.

In the citrus belt along the French and Itahan Riviera this species
was seen at San Remo and Porto Maurizio; at the former place in
destructive numbers on a few small trees. In Sicily it occure at
Catania, Messina, and Palermo. (PL III, fig. 4; PI. IV, figs. 1 and 2.)
At Messina it is found in several places around the city and does
considerable injury. Its first recorded appearance on the island,
four or five years ago, was at this place. At Catania it is more or
less widely distributed, while at Palermo it is still limited to a few
small areas, but it is destructive as far as its spread has occurred.

LIFE HISTORY AND HABITS.

This species, somewhat like the yellow scale {CTirysomiiihalus
aurantii Mask., var. citrinus Coq.), attacks the leaves and fruit
largely. These wiU be found heavily infested and often there wiU
be but a few on the twigs and branches. This habit of avoiding the
twigs and branches is not so complete as with the yellow scale, but
is distinctly more pronounced than with the Cahfornia red scale
(Ohrysomplialus aurantii Mask.). In severe infestations, of course,
and where the leaves have fallen, C. dictyospermi will be found in
considerable numbers on the twigs. Because the twigs and branches
are not so severely infested the injury is neither so great nor so rapid
as is the case with C. aurantii. But the dropping of the leaves
greatly injures the tree temporarily and new leaves scarcely grow
out until they in turn are attacked.

Wliilo the life history of this species has not been worked out in
detail, it is probably very similar to that of C. aurantii. The latter
species requires two and one-half to four months for its develop-
ment. There would thus be between three and four, possibly four,
full generations in a year.

jl. 134, U. S. Dept. of AgriculTure

Plate III.

Some Scale Insect Enemies to Citrus Fruits in Spain and Italy.

Fig. 1. — LeniDii distortt-d by the oleaiidi-r scale, Afpi'liatiix lidlirac; Italy. Fig. 2. — Xn orange

infested witli a coinmDn citrus scale, Puiiatnn'n zizi/plnis; Spain. Fig. 3. — Lemon incriisted

witli Ai<{tirli(jtn.f liidcrw; Sicily. Fig. 4. — Lemcin inlcsted with Chri/goiiiphalus dictyogpenni;

Sicily. Fig. 5. — I'uiintoria zizmihus on lemon twigs, Sicily, (t)riginal')

Bui 134, U. S. Dept. of Agriculture.

Plate IV.

Chrysomphalus dictyospermi on Orange
Leaf, Sicily. (Original.)

Lemon Tree Partially Killed by
Chrysomphalus dictyospermi.
(Original.)

Scars Resulting From Feeding of Thrips, Probably Heliothrips fasciatus.

(Original.)

INSECT ENEMIES OF CITRUS FRUITS IN SICILY.

CITRUS FEUIT INSECTS IN MEDITERRANEAN COUNTRIES. 17

NATURAL ENEMIES.

The most abundant parasite of this scale is a species of Aphelinus.*

Two or three species of Coccinellidse have also been seen feeding on

the scale. These are the same species as those already given for the

black scale.

THE PURPLE SCALE.2

Lepidosaphes heckii Newm.

DISTRIBUTION AND INJURY.

The purple scale was seen in most of the citrus sections of Spain and
Italy. It is found very generally in the Valencia orange section and
in the Sicilian lemon section. Not infrequently the numbers are
sufficient to do injury to the trees. This consists of the killing of a
few branches, or a portion of one side of the tree. (PI. V, fig. 1 .) The
scale is also more or less common on the fruit. It occurs in many
places in Sicily in. only scattering numbers, and in small areas, or, on
a few trees, in large numbers. This is about the status of the scale in
California and Florida and the Valencia section of Spain, but on the
island of Sicily it is less injurious than in any of these three localities,

LIFE HISTORY.

The purjDle scale deposits from 40 to 80 eggs, which are well inclosed
by the scale covering above and a lighter, cottony covering beneath.
The eggs hatch in 15 to 20 days in summer. Most eggs and young will
be found in the spring — ^May and June — and another large batch in
August and September. At all other seasons eggs will be found, but
usually in less numbers. The period of development from hatching
to egg-laying ranges from one and one-half months in summer to
three months in winter.

NATURAL ENEMIES.

The purple scale has been considered a pest of little economic
importance in Mediterranean countries, and this has been accounted
for through the efficient work of parasites. The writer takes excep-
tion to both of these counts. Just as severe injury has been seen from,
this scale in Spain as in California or Florida. And further, what
natural enemies are keeping it in check ? Hitherto, so far as known,
no internal parasite has been reported from the purple scale in Sicily,
Dr. Martelli was informed by the writer that he had seen evidence of
Aspidiotiphagus citrinus attacking the purple scale, but the observa-
tion was questioned on the ground that the scale was Lepidosaphes
ulmi and not L. heckii. Of course, the parasitized scales were not
positively identified at the time. Later Aspidiotiphagus citrinus

1 This species appears to be ^ . diaspidis, but its identity, according to Prof. Silvestri, of Portici, is somo-
what questionable.

2 Spanish, Serpeta; Italian, Pidocchio a virgola; Sicilian, Pidocchiu.

51981°— Bull. 134—14 3

18 BULLETIN 134, U. S. DEPARTMENT OF AGRICULTUEE.

Craw was reared from scales on citrus trees, and those scales from
which they emerged were positively identified, as was expected, as
L. heckii. The record, therefore, stands. Dr. Leonard!, of Portici,
a specialist on the Coccidae, stated that he had seen some evidence of
a parasite on the pui"ple scale, but he had not as yet studied it and did
not know the species. WTien the entomologists of Italy know so little
about the parasite, and when it was only very rarely found by the
writer, it certainly can not be counted as very effective in checking
the scale. The only other enemies of this scale seen in Sicily and
Spain were coccinellid beetles, and while these are more effective than
A. citrinus, they have not been seen in large numbers, and are not
accountable for keeping the scale in check.

Places have been seen in Sicily which were very free from the
purple scale, but according to the growers the scale had been present
there in considerable numbers several years ago, and disappeared.
Because of the meager knowledge of scales and the confusion of names
by most Sicilian growers, the foregoing may or may not be true. It
is, however, altogether probable. (For a discussion of climatic influ-
ences, see under Meteorological data, pp. 34-35.)

THE LONG SCALE.i

Lepidosaphes gloverii Pack.

DISTRIBUTION AND INJURY.

The long scale, so far as observed by the writer, is limited to Spain.
In that country it is particularly destructive in some sections. It is
frequently associated, with the i)urple scale, as in the Valencia section.
In some cases it was more abundant than the purple. Trees most
injured by this scale were seen near Burriana. (PL V, fig. 1.) The
long scale also occurs in Florida, from which place it was first described.
It has been reported from two counties in Cahfornia, though it has
never spread and is of no consequence as a pest there. It is dis-
tinguished from the purple scale in being -much more slender, and the
pygidial differences are also distinct.

PARLATORIA ZIZYPHUS Lucas.2

DISTRIBUTION AND INJLIRY.

Parlatoria zizyphus is the commonest of all the scales occurring on
the lemon tree in Sicily. (PI. II, fig. 2; PI. Ill, fig. 5.) It is also
found in most of the orange sections of Spain. (PI. Ill, fig. 2.) In
the Valencia section it was most abundant in the ''Ribera" in the
vicinity of Alcira. This scale ranges in abundance from a few scatter-
ing scales to a heavy incrustation on the leaves, twigs, and fruit. It

1 Spanish, Serpcta larga.

i Italian common name, FidocMo nero: Sicilian, Pidocchiu niuru: Spanish (Valenciana), Poll ncgre.

CITRUS FRUIT INSECTS IN MEDITERRANEAN COUNTRIES. 19

has been noted in several instances to cause a heavy dropping of the
leaves, and it is one of the commonest scales occurring on the fruit in
the markets. This may be partly because it adheres so firmly to the
fruit and is not easily removed by rubbing. While it occurs abun-
dantly in Sicily it is not extremely injurious to the tree, nor does it dis-
tort the fruit as does Aspidiotus hederae.

NATURAL ENEMIES.

This scale is especially free from parasites. On one occasion
Aspidiotiphagus citrinus was obtained from material infested by
zizyphus, but it can not be positively stated that there were not a few
purple scales among the material, so the record remains doubtful.

THE OLEANDER SCALE.

Aspidiotus hederae Vail.'
DISTRIBUTION AND INJURY.

The cosmopolitan and omnivorous oleander scale is found through-
out Spain and Italy and is an important pest on ripe lemons in the
latter country during the spring and early summer. (PI. Ill, figs.
1 and 2.) It was also observed on oranges in Spain, but is less injuri-
ous on oranges there than on lemons in Italy. In Cahfornia the same
scale occurs occasionally on old over-ripe oranges and lemons, but is
of no commercial importance. In May and June it is really a pest of
much economic importance in Italy. If such infestation occurred in
Cahfornia, it would certainly mean fumigation. As much as 90 per
cent of the fruit in some of the by-product factories has been seen
infested with this scale. Most of such fruit was brought there because
of it.

The oleander scale very seriously distorts the growth of the lemon
hi Italy. (PI. Ill, fig. 1.) Where the scale occurs there will be a
depression, so that the fruit has a rough and uneven appearance and
when numerous it becomes badly misshapen and distorted. The scale
also delays the coloring of the lemon, and such fruit can be distin-
guished at a long distance by its blotches of yellow and green. \Miile
the inferior fruit caused by the scale is considerable in Italy, it is
not a complete loss because it is acceptable for the by-product fac-
tory. On the Amalfi coast, where fruit of the finest texture is pro-
duced, it would seem that spraying, at a time when the yomig first
appear, would in many cases be profitable.

NATURAL ENEMIES.

A species of Aphelinus is the commonest parasite on this scale hi
Italy. On host plants other than Citrus this parasite was some-
times seen in very large numbei's. Aspidiotiphagus citrinus has also
been taken from A. hederae.

1 Italian, Bianca; Sicilian, Bianca o rugna.

20 BULLETIN 134, U. S. DEPAETMENT OF AGEICULTUBE.

THE COTTONY CUSHION SCALE.

leery a purchasi Mask.

DISTRIBUTION AND INJURY.

The cottony cushion scale was observed at Acireale, Messina, and
Bagheria in Sicily. It was not seen elsewhere in Italy, except at
Portici, and was not observed anywhere in Spain. It is of recent
introduction in Sicily (five or six years ago) and is supposed to have
come from North America or Portugal. A severe infestation occurred
at the places mentioned in Sicily as observed in April. Several trees
were killed and cut down afc Bagheria. (PI. V, fig. 2.) Novius
cardinalis was seen at work at Messina and Acireale, but after per-
sistent search none could be found at Bagheria despite the fact that
the beetle had been liberated by Dr. Savastano in February. Dr.
Savastano was informed of this fact, and another colony was promptly
liberated. When the place was again visited in August it was
gratifying to see that apparently the entii-e infestation was com-
pletely checked by the work of the beetle. The owner of the grove,
who in May despaired of saving any of the trees, in August was
elated and believed it little short of mii'aculous that he could be
freed of the pest in such a short time. This infestation was so com-
pletely cleaned up that Novius had disappeared for lack of food, and
no trace of the beetles could be found in August. These same con-
ditions have been observed in California; the beetles, upon eating
all of the scales by midsummer, would themselves disappear, reap-
pearing, however, in the following spring. The few young scales
that escaped the beetle the year previous would multiply to such an
extent that a heav^^ infestation occurred by the following sprmg and
would thus fm-nish food for the returning beetles wherever they
came from. These circumstances were observed for four successive
seasons in a particular grove in California, where the trees were
finally cut back. It is hoped that these same circumstances will not
prevail at Bagheria.

LIFE HISTORY.

From 500 to 800 eggs are deposited in the large fluted cottony
mass which is secreted for this purpose. The eggs hatch in from 10
days to 3 weeks, depending upon the temperature. The young
larvae settle on the leaves and tender twigs largely, but later nearly
all those on the leaves migrate to the twigs and branches, adults
being found even on the tree trunk. The time required for develop-
ment varies considerably mider the same conditions and may range
from three to four or five months. The great majority of eggs and
yoimg appear during May and June.

Bui. 134, U. S. Dept. of Agriculture.

Plate V.

Fig. 1 .—Orange Trees Partially Killed by the Purple Scale (Lepidosaphes qloveri)
AND the Long Scale (Lepidosaphes beckii) at Burriana, Spain. (Original.)

hi^i^M:^-^

Fig. 2.— Lemon Trees Killed by the Cottony Cushion Scale (Icerya purchasi) at
Bagheria, Sicily. (Original.)

SCALE INSECT ENEMIES OF CITRUS FRUITS IN THE MEDITERRANEAN.

3ul. 1 34, U. S. Dept. of Agricultur

Plate VI.

Fig. 1.— The Mealy Bug (Pseudococcus citri) on Oranges, Sicily. (Original.)

Fig. 2.— Lemons with Severe Infestation of Mealy Bug (P. citrp, Acireale, Sicily.

(Original.)

DAMAGE TO CITRUS FRUITS BY THE MEALY BUG.

CITRUS FRUIT INSECTS IN MEDITERRANEAN COUNTRIES. 21

NATURAL ENEMIES.

The one important natural enemy of this scale in Italy, as elsewhere,
is the Australian ladybird, Novius cardinalis Muls. This beetle, as
already intimated, has been introduced into all the known colonies of
the scale in Sicily. The beetle has also been distributed with success
in Palestine.

Cryptochaetum icerya Will., a dipterous parasite, is the second most
important enemy of the cottony cushion scale in some of the countries
where it occurs, but it was not taken by the writer in Sicily. It is a
small fly of a metallic green color, the larva of which lives within the
scale.

THE CITRUS MEALY BUG.'

Pseudococcus citri Risso.
DISTRIBUTION AND INJURY.

The citrus mealy bug is found in greater or less numbers in nearly
all parts of the citrus sections of Spain and Italy. It frequently
occurs in serious numbers, and masses of the insects, with their cottony
secretion and also much sooty-mold fungus, wiU be found on the
leaves and fruit. In Sicily during the season of 1913 the writer
unhesitatingly places the mealy bug at the head of all the citrus insect
pests. Clirysomphalus dictyospermi is serious enough in several
places, but the area involved is small as compared with that seriously
infested with the mealy bug. The scale is also more amenable to
treatment. The worst infestations of the mealy bug occurred along
the east coast at Catania, Acireale, and Messina, and several interme-
diate points, though bad infestations were also seen at several points
on the north coast. In many places the numbers were so great that
the masses of cotton extended for an inch or two below the fruit.
(PI. VI, figs. 1 and 2.) Many of the lemons fell from the trees, others
were stunted in growth, and a heavy dropping of the leaves occurred.
The fallen fruit and leaves, with the insects and cotton still on them,
gave the ground a distinctly whitish appearance.

Infestations of the mealy bug in Sicily in 1913 were just as severe
and much more extensive than were those in the Ventura and San
Diego sections in California a few years ago. Even outside of these
extremely severe infestations, the insect was generally distributed
and much more abundant throughout the entire citrus area in Sicily
than was ever seen in Cahf ornia outside of the two sections mentioned.^

■Spanish (Valenciana), Cotonet; Italian, Cocciniglia farinosa degli agrumi; Sicilian, Cuttunedda.

2 The writer may be pardoned for making frequent comparisons between the Mediterranean citrus sec-
tions and that of California, but this is done for three reasons: First, people can best judge of conditions iu
foreign countries in terms of their own conditions; second, California is most like the Mediterranean citrus
region; third, the writer is acquainted with citrus conditions in California.

22 BULLETIN L34, U. S. DEPARTMENT OF AGRICULTURE.

It was stated by many people that the mealy bug was unusually
abundant on the island in 1913.

LIFE HISTORY.

The mealy bug lays 300 or 400 eggs in the cottony mass that is
secreted for the purpose, and these hatch in from 10 days to three
weeks, according to the season. The development ranges from one
month in summer to three in winter.

NATURAL ENEMIES.

The natural enemies of P. citri in Sicily are varied and numerous.
The writer has found feeding on or attacking this insect one species of
Hemiptera, two of Neuroptera, two of Coleoptera, two of Diptera,
and six or seven of Hymenoptera. Of these, probably the most
important is one of the species of Diptera. Two or three species of
Hymenoptera were also very common, as well as one of the cocci-
nellids.^

In spite of all these enemies the mealy bug was the worst citrus
pest in Sicily in 1913. The increase and decrease of this insect there,
however, may be very greatly influenced by the attacks of all these
enemies.

PRAYS CITRI MiUier.2

DISTRIBUTION AND INJURY.

Prays citri is the name of a small moth the larva of which often
does serious mjury to the blossoms of the orange and lemon. It is
found in Sicily, in the Provinces of Calabria and Campania, and
probably in other less important citnis sections of Italy. It was seen
to be particularly abundant in the vicinity of Messina in August,
1913, and a large percentage of the blossoms and newly formed fruit
was destroyed. It occurs from April to November, but is especially
destructive to the blossoms of the forced verdelli crop, which occurs
in midsummer. The injury is caused by the larvae eating into all the
flower organs — stamens, pistils, petals, and ovule.

LIFE HISTORY.

The eggs are deposited apparently upon the cahces or peduncle of
the flower, usually just prior to opening. The larvse upon hatch-
mg bore through the inclosing parts to the organs within. Flowers
thus attacked will have holes in the calyx, parts eaten out of the
stamen, or burrows made into the pistil and ovule. Pupation usually
occurs within the flower, but also in protected places on the leaves
or forks of the twigs and branches.

' These different species of parasitic and predaceous enemies of the mealy bug in Sicily may be treated in
more detail in a later paper.
2 Italian common name, Tignola degJi agrumi.

CITRUS FRUIT INSECTS IN MEDITERRANEAN COUNTRIES. 28

RED SPIDERS.

One species of red spider was seen in all the citrus sections of
Spain and Italy. With a few exceptions, however, the numbers
were not sufficient to do any great injury. Over small areas, par-
ticularly along the roadside where there was considerable dust on
the trees, many of the leaves had the characteristic light-colored
mitehke areas. Not infi-equently, too, the lemons would be scarred
around the depression formed by the nipple at the calyx end, this
situation being the most favorable feeding place on the fruit.

This species is identified by the Italian entomologists as TetranycJius
telarius. Wliat we have been calling telarius in this country has
recently been made spionymous with T. himaculatus Harv. The
habits of himaculatus in the citrus belt of California are very different
from those of telarius m Spam and Italy. Bimaculatus has been
observed to infest severely other food plants growing in the midst
of citrus trees, both in California and Florida, without attacking the
citrus trees at all. Bimaculatus on beans, violets, and a long list of
other plants, feeds generally over the entire surface. Telarius in
Spain and Italy feeds in restricted areas precisely as does T. sex-
maculatus Riley on citrus trees. But red forms of telarius •are com-
mon in Mediterranean countries, while m California all that have
been observed of sexmaculatus are pale colored. The writer is not,
however, necessarily assuming that sexmaculatus and telarius are
synonyms, though their feeding habits are smiilar. He is, however,
of the opmion that, judging from their difference in feedmg habits,
our himaculatus and the European telarius are not synonymous if the
Mediterranean citrus species is properly identified as telarius.

Another species which is flat and scalelike, probably a species of
Tenuipalpus, was occasionally met with on citrus foliage in Sicily.

THRIPS.

A species of thrips, said to be Heliothrips fasciatus Perg., occasionally
does some injury to the orange as shown by the marred fruit. (PI.
IV, fig. 3.) But thrips scars on the fruit in Spain and Italy are
rare, so that the insect is of little economic importance. Around
Jaffa, however, a species of thrips sometimes does considerable
injury, and spraying has been necessary.

THE CONTROL OF CITRUS FRUIT INSECTS IN MEDITERRANEAN

COUNTRIES.

With the exception of a little fumigation in Spain for the control
of OJirysomphalus dictyospermi, and limited spraying in Sicily for the
same insect, practically no remedial measures are employed for the
control of citrus fruit insects in the countries bordering on the Medi-
terranean. This fact might be taken to mean that the pests there are

24 BULLETIN 134, U. S. DEPARTMENT OF AGRICULTURE.

of little economic importance because of their natural enemies, or
for some other reason. But the lackx)f preventive measures in those
countries as compared with California and Florida is largely a ques-
tion of standards.

The black scale is as serious a pest in Spain as it is in California.
A large share of the milhon dollars a year spent in Cahfornia for the
control of citrus pests is counted against this insect. The black scale
is not, however, as serious a pest in Sicily as it is in California and
Spain. The purple scale injures trees and mars fruit in wSpain and
Italy as it does in California and Florida. The long scale is more
injurious in Spain than it is in Florida, so far as the writer's observa-
tions have extended in Florida. This scale is not reported from
Italy. While it is recorded from one or two small sections in Cali-
fornia, it is of no consequence as a pest. Parlatoria zizyplius not
infrequently causes a heavy dropping of the leaves, and also attacks
the fruit both in Spain and Italy, It is not a general pest in the
groves of Cahfornia or Florida. It is often taken, however, on lemons
in the markets of the eastern States, having been imported from
Italy. Aspidiotus liederae is a more serious pest on ripe lemons in Italy
than it is anywhere in the United States, The mealy bug, Pseudococcus
citri, ranks just as high, if not higher, as a pest in Spain and
Sicil}^ than it does in California. The citrus white-fly, the most
serious of the Florida citrus pests, does not occur in the Mediter-
ranean region.

Nothing in the way of artificial control is practiced against any
of the foregoing insects in any of the Mediterranean countries. One
or two cases were met with in Spain where the grower had tried
some patent concoctions on a few trees. Pruning, however, may come
in the category of control for insects in those countries more than it
does with us, as the following dialogue may illustrate : " WTiat do you
do for the scales when they actually kill the twigs and branches as
seen on the trees before us ?" "We cut out the twigs and branches."
Cutting out dead twigs and branches is, of course, a part of the prun-
ing process, and not infrequently these dead parts are due to one of
the foregoing insects. If the fruit is infested with the sooty-mold
fungus, it is washed in sawdust, but the cause is not taken into con-
sideration. If scales are present on the fruit, such fruit is placed
in an inferior grade, or it is consigned to the by-product factory.

In the case of ChrysompTialtts dictyospermi, however, a start in
control work is really being made both in Spain and in Italy. This
is no doubt due to the fact that this scale causes more complete
injury to the trees— indeed, practically kills them. As before stated,
fumigation was seen practiced in Spain last year at Piaporto, Picana,
and Piug in the Valencia section. Possibly it is practiced also in other
places, but evidence was not seen elsewhere at the time of the writer's

CITRUS FRUIT INSECTS IN MEDITERRANEAN COUNTRIES. 25

visit. Mr. R. S. Woglum, of this bureau, introduced fumigation in
Spain in 1910, and it is being carried on in accordance with modern
California methods. (PI. X, fig. 4.) The cost as figured from a
definite number of trees amounted to 1.10 pesetas, or about 20 cents
per tree. In actual practice gi-owers state that the cost averages
from 25 to 30 cents a tree, which is about tlie same as that of Cali-
fornia for trees of the same size. There are no large trees in the
Valencia section and there are no seedlings.

Advocated by Dr. L. Savastano,^ the well-known pathologist,
director of the experiment station at Acireale, the use of lime-sulphur
is becoming popular for the control of C. dictyospermi in Sicily.
Fumigation is out of the question in most parts of Italy where citrus
trees are planted solidly because of the nearness of the trees. Spray-
ing, therefore, is the only artificial measure that may be employed.
The lime-sulphur spray is intended to kill the young largely. It is
applied in June and again in August or the first part of September.
The strength used is 5 per cent of lime-sulphur of 1.25 gravity (29°
Baume). This is for summer use when high temperatures may cause
burning if used stronger. During the winter it is used at a strength of
8 per cent and, if the infestation is severe and many of the leaves off,
as high as 10 per cent. Lime-sulphur at the strength mentioned will
probably kill most of the young that are hit, and if the application is
repeated two or three times the numbers of the pest will be consider-
ably lessened. Two or three sprayings are recommended at first to
clean the trees, and then only one spraying annually thereafter. The
same spray is recommended by Dr. Savastano with good results
against Aspidiotus Jiederae and Lepidosaphes heckii.

The spray as used in the groves of Sicily is applied by means of a
hand pump mounted on a wheelbarrow truck. This is about as large
an outfit as may be used under the trees. No horses ever enter most
of the Italian citrus groves, all the work of cultivation, etc., being
done by hand labor. From the writer's observations a very great
improvement resulted from the applications of lime-sulphur. Not
all the insects were, of course, killed, but the numbers were greatly
lessened, and a marked improvement in the trees resulted. This
spray has the advantage, also, of checking many of the possible
fungous troubles as well as stimulating the growth of the tree.

Aside from the control measures mentioned. Dr. G. Brigante ^
states that the worm, Prays citri, of the blossoms may, if necessary,
be handled by a 1 per cent solution of lead arsenate. But poison
sprays are in bad repute in Italy.'' Prof. Ampola and Dr.

1 Savastano, L. Le conclusioni pratiche per la poltiglia solfocalcica (formo a della Stazione). R. Staz.
Sper. di Agr. e fruitti coltura, Acireale, Sicily. Bol. no. 11, 11 p., April, 1913.

2 La coltivazione degli agrumi in Provincia di Salerno, Dott. G. Brigante, Direttore Cattedra Ambiilante
di Agricoltura per la Provincia di Salerno, 1912.

3 Insetti damnosi e composti arsenicali, Teodosio De Stefani, Gazetta Commerciale, Palermo, p. 5-10,
1912. •

26 BULLETIN 134, U. S. DEPARTMENT OF AGRICULTUEE.

Tomasi, of the Station Chimico-Agraria Sperimentale di Roma,
strongly recommended the prohibition of arsenical s for general
agricultural purposes. They conclude that their use is injurious to
all sorts of plants and animals, but the most potent of their reasons
is that the farmers, instead of poisoning their insect foes, might
destroy human life. In addition to these control measures practiced
in Spain and Italy, a small amount of spraying has been done around
Jaffa in Palestine for a species of thrips on the orange. From the
little evidence of thrips work that was seen at Jaffa the species occur-
ring there is not Euihrips citri, as was supposed.

MEDITERRANEAN CITRUS FRUIT INSECTS THAT DO NOT OCCUR IN
THE UNITED STATES AND THE POSSIBILITY OF THEIR INTRO-
DUCTION.

Of the citrus insects discussed in the foregoing pages, two do not
occur in the United States, namely, Ceratitis capitata and Prays citri.
Two others, Chrysomphalus dictyospermi and Parlatoria zizypTius, while
occurring in the United States, do not appear to be established as
important pests, as is the case in the Mediterranean region. Con-
cerning the distribution of these two scales, Mr. C. L. Marlatt, under
date of March 5, 1914, writes as follows:

Chrysomphalus dictyospermi is frequently found on palms and quite a number of
other plants which are probably imported, and has a wide distribution in greenhouses.
Out of doors it does not seem to thrive very well on this continent, and I think we
have very few outdoor records of it, and these naturally from southern points. It hag
been so often brought into this country that its failure to establish a foothold in citrus
orchards apparently indicates unfavorable conditions for this insect, but it is, of course,
possible that this may have resulted, after all, from lack of favorable opportunity.
Parlatoria zizyphus, as you know, is brought to this country all the time on Italian
lemons, and has been found in the open market wherever these lemons are sold, in-
cluding well-established citrus districts such as those of Florida and Louisiana.

In case these two scales did become established in our citrus groves
our present control methods, at least fumigation, would handle them
successfully. This fact, however, should be no exccuse for not quar-
antining against them. On the other hand, the other two, Ceratitis
capitata and Prays citri, would not only be serious pests but would
not be controlled by any of our methods now in use for citrus trees.
Ceratitis, moreover, is not limited as a pest to citrus fruits; indeed,
citrus fruits are by no means its favorite food, but it attacks a long
list of deciduous fruits. The scope of this paper has to do, however,
chiefly VAth citrus fruits.

The first shipments of oranges are made from Spain as early as
October, and a few of the mature fruits at this time may contain
larvffi of Ceratitis. But with the approach of cold weather in Novem-
ber and December the fly disappears. The time when infested fruits
might be received from Spain is at the beginning of the shipping sea-

CITRUS FRUIT INSECTS IN MEDITERRANEAN COUNTRIES. 27

son in October and November, and again during the final shipments,
the last of June and first of July. The reason more infested oranges
do not occur in Spain is not, as has been suggested, because the fruit
is picked too green, but because practically all the fruit matures and
is harvested at a season when the fly is not active or breeding. This
applies to practically all semitropical countries where citrus fruits
are grown commercially. Plenty of oranges were seen in Spain that
were fully mature in March, but which were not harvested until
May or June. The heavy shipments do not begin in Spain until
November, and by May the season is virtually ended.

What has been said regarding oranges in Spain applies to all the
Mediterranean citrus sections. Up to the middle of October in Pal-
estine the oranges were still too green to be infested with Ceratitis.
Even though the fly may be present and actually deposit eggs in the
fruit, there is no danger of the larvae developing if the fruit is imma-
ture. In spite of numerous punctures and eggs in the fruit which
were seen in Sicily up to October 1 and in Palestine up to October 15,
no larvae succeeded in developing or getting beyond the egg cavity,
but there perished.

The lemon is an unusual and rare host for Ceratitis, at least in the
gi-eat lemon-producing section of Sicily. It was only very rarely,
and, it must be admitted, more or less accidentally, and after much
persistent searching, that lemons were found infested in Sicily. Out
of numbers running into hundreds of thousands only 15 were found
infested. And all of these infested lemons were so badly broken
down by decay that they would not only be rejected for shipping,
but, with three or four exceptions, would be rejected for the by-
product factory. So far as one season's experience in Sicily warrants
the conclusion, therefore, there is only the remotest possibihty of the
entrance of Ceratitis into this country through the importation of
lemons from Italy.

In the case of most other fresh mature fruits, which are harvested
between May and November, inclusive, and coming from the Medi-
terranean -countries, the possibility of Ceratitis introduction can be
removed only through a strict embargo against such fruits or a
subjection to a rigid inspection.

THE OLIVE FLY.

Dacus oleae Rossi.

Since the olive is usually grown in the same countries as citrus
trees, it may be pertinent in this place to mention the olive fly.
This insect, Dacus oleae, is one of the most serious pests of the Medi-
terranean countries. In fact it is the opinion of the writer that it far
outranks Ceratitis capitata. A heavy infestation of the olive fly has
been seen in different places, but particularly in Sicily and southern

28 BULLETIN 134, U. S. DEPARTMENT OF AGBICULTURE.

Italy. Most of the olives attacked fall to the ground before reaching
maturity. In the case of the oHve fly, mature fruit is not at all
necessary for infestation. Because of the economical use made of
aU the inferior fruit in these countries — something we have yet to
practice — infested olives are not a complete loss, for they are used
for oil, most of which is used in the manufacture of soap. The
striking difference in habits between the ohve fly and the Medi-
terranean fruit-fly is that, with the former, pupation occurs within
the fruit, instead of in the ground or otherwise out of the fruit as is
the case with Ceratitis.

Infested olives may be distinguished by a circular area on the
surface that is of a Hght gray color. Before entering the pupal stage
the larva eats out a channel to the surface of the fruit, leaving only
the thin epidermis. It is this, with the tissue eaten away below,
that forms the characteristic gray area that indicates infestation.
It is much the same as that made in the case of the pea and bean
weevils. Having completed the burrow to the surface, the larva
retreats a short distance and transforms to the pupa, enclosed in the
characteristic puparium, that looks much like that of Ceratitis.
Upon emerging the adult fly breaks through the epidermis, which
has been left for protection, by means of its ptilinum.

Fortimately ohves are not transported unless pickled, and thus
the danger of introduction is not great. But a sharp lookout should
be kept for any olives that might possibly be imported fresh from
these comitries, since the egg, larval, and pupal stages are all passed
within the fruit.

THE MEDITERRANEAN CITRUS FRUIT INDUSTRY. ^

LOCATION.

The most important citrus section of Spain, where 90 per cent of
the crop is produced, consists of a narrow strip, 10 or 15 miles wide
and 150 miles long, extending from Denia in the Province of Alicante
northward as far as Vinaroz in the Province of Castellon. This is
the so-called ''Valencia section," the city of Valencia being situated
somewhere near the center of the strip. In this section are recog-
nized two distinct districts, the "Ribera" and the "Plana." The
"Ribera" lies to the south of Valencia and centers chiefly about the
towns of Alcira and Carcagente. This district is more or lessroUing
and hilly and is separated from the sea, which is 15 or 20 miles
distant, by hills and mountains. The "Plana" hes north of the
City of Valencia and centers about the town of Burriana. This is a
perfectly flat plain and borders directly on the sea. Around the

1 In this account of the Mediterranean citrus industry only such phases are presented as are necessary
to a better knowledge of the insects discussed in the earlier pages of this paper.

Bui. 1 34, U, S. Dept. of Agriculture.

Plate VII.

«^'#£k%f

•*^ i^?-^

Fig. 1.— Interior of Packing House at Alcira, Spain. (Original.)

Fig. 2.— The Railroad Packing House at Carcagente, Spain. (Original.)
SORTING AND SHIPPING CITRUS FRUITS IN SPAIN.

Bui. 1 34, U. S. Dept. of Agriculture.

Plate VIM.

Fig. 1.— Hauling Oranges to the Boat Landing at Burriana, Spain. (Original.)

Fig. 2.— Loading Oranges in Small Boats to be Transported to Steamer, Burriana,

Spain. (Original.)

ORANGES IN TRANSIT IN SPAIN.

CITRUS FEUIT INSECTS IN MEDITEEKANEAN COUNTRIES. 29

city of Valencia itself in the "Heurte de Valencia" there are few
oranges grown, excepting at Piaporto and Picana and to the west-
ward of these villages.

Going farther southward the next important orange section is at
Murcia, and then at Malaga, with a few scattering groves between.
In the Malaga section probably the most important center is at
Alora, some distance back from the sea, and in a mountainous
country. The next important section of Andalusian Spain is in the
vicinity of Seville. Here, however., practically all of the crop is of
the bitter variety and is shipped to Great Britain and made into
marmalade.

METHODS OF HANDLING CROP.

The harvesting season in Spain extends from October to July, with
the heaviest shipments occurring from November 15 to December 1.
The oranges are picked in small baskets and from these are dumped
into larger baskets along the roadside or edge of the grove, thence
being carried, by means of carts, to the packing house. They are
here spread on the floor to a depth of about 2 feet, the floor and sides
for a couple of feet being first covered with a layer of rice straw.
Women sit around the edge of these piles of fruit which, if infested
with sooty-mold fungus, is rubbed first in wet and then in dry saw-
dust to remove the mold. Other women then sort out the fruit in
thi'ee different sizes, entirely by sight, and also discard the culls.
The fruit is then wrapped in paper by other women and packed in
the boxes.

The three sizes of fruit are represented by the cases containing
respectively 420, 714, and 1,064, and which weigh 165 pounds each,
or about twice that of the American box. There is absolutely no
machinery in a Spanish packing house, all the processes of hancUing,
grading, washing, and box making being done by hand. The packing
house itself is, therefore, simple, consisting of four walls and a roof,
the earth forming the floor. (PI. VII, fig. 1.) The appurtenances
consist of the shipping cases, a good supply of shallow wicker baskets,
and plenty of women to do the work. The time the fruit remains
in the packing house depends largely on the departure of the steamer
and varies from a day or two to more than a week.

After the fruit is packed in cases it is hauled, in carts, without
springs,, to the boat landing. Here the cases are unloaded along
the shore and later placed in small boats and finally transferred to
the steamer. At Burriana, the port of the ''Plana" district, from
which 2,000,000 cases are shipped annually, there is no pier, and the
small boats are pulled up on the gravelly beach by oxen. (PI. VIII,
fig. 2.) The town, which is about 2 miles inland, and in v/hich
there are upwards of 100 packing houses, is not connected with the

30 BULLETIN 134, U. S. DEPARTMENT OF AGRICULTURE,

beach by any railroad, and all of the 2,000,000 cases arc hauled in
carts each year, over a very bad road. (PI. VIII, fig. 1.)

The foregoing description applies to the fruit sent by sea. A very
small amount of the crop that is sent by railroad is also packed in
boxes and handled in the way described. But nearly all of the fruit
shipped by railroad is simply conveyed in loose carload lots. From
10,000 to 15,000 tons are exported from the Valencia district in tliis
manner, wliile 400,000 to 450,000 tons are shipped by sea. Where
the fruit is to be shipped by railroad in loose carload lots, the packing
house occurs alongside the railroad. These packing houses are even
simpler than those already described, for they consist simply of a
roof, the sides being left open. The earth is graded up to the height
of the floor of the car to facilitate the transfer of the fruit. The floor
of this open-air packing house is covered with rice straw, as are also
the floor and sides of the car. The cars are usually of the pattern
of our stock care, with lattice work on the sides to allow for plenty
of ventilation. (PL VII, fig. 2.)

The oranges are brought from the field directly to the railroad
packing house, where they are piled on the floor. Women here give
the fruit the sawdust treatment, if needed, and the culls are discarded.
It is now ready for the car, where it is carried in baskets and filled
to the depth of a couple of feet. Such fruit goes mostly into France,
or to other parts of Spain.

PRODUCTION AND EXPORT.

From figures kindly furnished by Mr. Claude I. Dawson, American
consul at Valencia, the total production of oranges for the season
1912-13 amounted to nearly 7,000,000 cases of 165 pounds each.
This amounts to about 38,500 California carloads or 45,117 Florida
carloads. Of this amount 5,573,627 cases were shipped by sea, as
follows :

Cases.

Great Britain 2, 253, 076

Germany , 1, 374, 829

Holland 501, 645

Norway and Sweden . : 84, 374

Austria'^Hungary 18, 1 10

Denmark , 17, 103

France 6, 033

Russia 1, 000

The overland shipments to France approximated 1,200,000 cases,
and the remainder of the crop was consumed in Spain.

According to the figures of the United States Bureau of Statistics
there were slupped into the United States from Spain in 1912, 9,000
pounds of oranges and lemons (not separately listed), valued at S204.
The only records the writer was able to obtain in Spain of orange sliip-

CITRUS FEUIT INSECTS IN MEDITERRANEAN COUNTRIES. 31

merits to the United States were of a few small shipments during the
last two or three years from Seville. Tli.e use made of these ship-
ments was not known, but was no doubt for the manufacture of
marmalade, as is the case with all the bitter orange product of Seville.
One hundred and fifty thousand cases are exported annually from
Seville, mostly of the sour or bitter orange, and practically all are
sent to Great Britain for the manufacture of marmalade.

LOCATION.

The important citrus fruit areas of Italy are on the Island of Sicily,
in the Provinces of Calabria and Campania, and along the Biviera
di Ponente and the Riviera Levante.

The most extensive section, particularly for lemons, is in Sicily.
The area extends along practically the entire north and east coasts.
There are, of course, breaks in this strip, as where the mountains
extend abruptly to the sea, or where grapes largely occupy the ter-
ritory, as at Milazzo, Cairuba, and Riposta, or on the plain south of
Catania, where various other crops are grown. The limits of this
area are the Gulf of Castellammare on the north and Avola, below
Syracuse, on the east coast. Even within these limits lemons do not
occur solidly because of the irregularity of the land, lack of water,
and unsuitable soil. Most of the lemons are grown in close proximity
to the coast, but occasionally they extend inward for several miles,
as at Monreale, Alcantara, and Floridia. Occasionally citrus trees
will be found in the interior valleys, but here it is largely oranges,
probably because of the greater likelihood of frost.

In the Province of Calabria there is a considerable area of citrus
fruit along the coast from Reggio to Rosarno and farther northward
and inland at Cantanzaro and Cosenza. The Campania section is
situated principally along the coast from Salerno through Majori and
Amalfi to Positano. Here the trees are grown on terraces (PL IX,
fig. 1), formed on the very abrupt slopes extending upward from the
sea. Unlike other sections, also, the trees are covered with trellis,
on which, during the winter for protection against frost and wind,
is placed straw and brush. The Riviera section consists of a narrow
and much broken strip extending from VentimigUa on the French
border to Spezia.

METHODS OF HANDLING CROP.

Lemons in Sicily are harvested practically every month in the
year, the heaviest shipments occurring in the spring and early summer,
while the fewest shipments occur during the month of August. The
number of pickings in any particular grove is from four to six. Tlie
lemons are broken from the tree by hand, leaving two or three inches

32 BITLLETTN 134, V. S. UKPARTMRNT OF ACRICITLTURE.

of stems with the fruit. These are placed in small baskets, supported
in the tree or carried on the arm, and when filled are carried to the
men who ciip off the extra stem, leaving the usual button. In the
case of verdeUis, green lemons, during the summer, these are some-
times broken from the tree by means of a forked bamboo rod. This
rod is long enough to reach to all parts of the tree from the ground,
and the fruit is simply allowed to fall ^s it is twisted off. Wlaen asked
about the effects of bruising by such a method, it was stated that the
fall does not hurt the green fruit. Such a method is rapid, since the
lemons are quickly twisted off and allowed to fall, and are picked up,
usually by small boys, but it is not practiced by the best growers.

The fruit with the small buttons is placed in baskets and carried
thus to the field packing house (PI. X, fig. 3). Here it is roughly
graded, and the culls are separated for consignment to the by-product
factory. It is placed in the regular shipping boxes (PI. X, figs. 1,2),
but thrown in loosely, with paper around the inside of the box.
Sometimes with the better grades, and in the case of long hauls,,
each lemon is wrapped separately. In these shipping boxes the fruit
is carried in carts to the town or exporter's packing house, where it is
regraded, sorted, and packed back in the same boxes, when it is
carried in carts to the fighter, and thence to the steamer for final
shipment. (PI. IX, fig. 2.)

The time the fruit remains in the field packing house may vary
from 1 to 3 or 4 days, or longer; in the exporters' packing houses,
from a day or two to a week or two. The average time of transit from
Palermo to New York is 12 or 15 days. The time between the picking
and the landing of the fruit in New York may thus range from 18
days to 30 or 40 days.

A large percentage of the fruit that is harvested dming the spring
and early summer is what is called in Cafifornia tree-ripe fruit,
while that harvested in midsummer and fall is mostly green fruit, or
verdeUis. VerdeUis, of course, occur with the yellow fruit, and they
are packed separately and so consigned. The large proportion of
verdeUis which occur in midsummer are artifically produced. During
the previous summer water was withheld from the trees for about six
weeks, and then two or three irrigations were applied in quick suc-
cession. This procedure causes the trees to throw out an unusual
amount of blossoms which mature mto fruit the foUowing summer.
This fact of a very large preponderance of green fruit during the
summer and fall has an important practical bearing in comiection
with the possible infestation of the Mediterranean fruit-fiy. It is
during the summer and fall that the fly is most actively breeding.
Very little yeUow fruit appears before November, but from that time
until the following July it is nearly all yellow fruit. No place was
seen in Sicily where lemons are subjected to forced curing, as they are
in Cafifornia.

j|. 1 34, U S. Dept. of Agriculture.

Plate IX.

>i-

'-:p\

V*-

m
^[-^k.

fix*

.v/.

•^^.;

Fig. 1.— The Famous Terraced Lemon Groves on
THE Amalfi Coast of Italy. (Original.)

Fig. 2.— Lighters of the Felluca Type Carrying Lemons to the Steamer, Palermo.

LEMONS IN ITALY.

Bui. 134, U. S. Dept. of Agriculture.

Plate X.

Fig. 1 .—Transporting Lemons in the Hilly Section of Sicily, where the Roads

ARE Poor. (Original.)
Fig. 2.— Open Gars (No Roofs) Loaded with Boxed Lemons for Transportation

from the Smaller Towns to the Seaport, Sicily. (Original.)
Fig. 3.— a "Field" Packing House and Cart with Baskets of Lemons from the

Near-by Groves, Sicily. (Original.)
Fig. 4. -A Fumigating Tent, in Position, Spain. Modeled After the Outfits Originat-
ing in Galifornia. (Original.)

Fig. 5.— a Laboratory at Palermo; These are the Pepper Trees. (Original.

TRANSPORTING LEMONS IN SIGILY. FUMIGATION OF GITRUS TREES

IN SPAIN.

CITRUS FRUIT INSECTS IN MEDITERRANEAN COUNTRIES. 33

PRODUCTION AND EXPORT.

The total acreage exclusively in citrus fruits in Italy in 1909,
according to Powell/ was 108,400 acres, and 170,000 acres on which
other crops were grown. A total of 85,252 acres were grown in
Sicily, out of which 4,102 acres were in mixed cultivation; 13,890
acres entirely in citrus fruits were in the Province of Calabria and
9,385 acres in the Province of Campania.

The total production of lemons in Italy, includmg that converted
into by-products and that used in home consumption, in 1911 was
1,192,701,829 pounds, or 47,785 of our carloads, basing this calculation
on the size of the CaUfornia box of lemons, which is estimated to
weigh 80 pounds, and on the number of these boxes, namely, 312,
loaded in the California cars. The exports of lemons alone were
570,306,431 pounds, or 22,841 of our carloads. The United States
during the past 10 years has received about 35 per cent of the total
exports. In 1910 the distribution among the principal countries
was as follows:

Per cent.

United States 31. 5

Austria Hungary 19. 8

United Kingdom 19. 5

Germany 11. 3

Russia 8

In 1911, 96 per cent of our Itahan lemons came from Sicily, of
which 86.4 per cent were from Palermo, 9.8 per cent from Messina,
and 3.8 per cent from Naples, including the Amalfi Coast district.
The Itahan box contains about 73 pounds of fruit, which is chiefly
in 300 and 360 per box sizes. About hah of the total imports arrive
here in May, June, afid July; 85 to 90 per cent are received in New
York, about 5 per cent in Boston, and smaller quantities in New Or-
leans, Philadelphia, Baltimore, and a few other places.

According to the United States Bureau of Statistics, the total
imports of lemons from Italy in 1912 were 145,275,122 pounds,
valued at S3,359,115; of oranges, 401,161 pounds, valued at $9,319.

FRANCE AND ALGERIA.

No extended observations were made in tlie citrus sections of
France and Algeria. In France the area appears to be limited to a
short and much broken strip along the Mediterranean Coast, the
French Riviera, extending from Cannes to Menton on the Italian
border. In northern Africa the most extensive production of oranges
is in Algeria. But the output there is not large, for Algeria and
France together do not produce nearly enough for home consumntion
in France, as evidenced by the large imports from Spain.

1 The figures here given are from Powell, Harold C, and Wallschlaeger, F. O. The Italian lemon indus-
try. In Citrus protective league of California, Bui. 10, 58 p., Jan., 1913.

34 BULLETIN 134, U. S. DEPAETMENT OF AGRICULTURE.

PALESTINE AND EGYPT.

1

In the eastern Mediterranean countries the most important citrus-
producing sections arc in Palestine and Syiia. The largest and most
important district is in the neighborhood of Jaffa, the home of the
well-known Jaffa orange; 1,600,000 boxes (same size as ours) were
shipped from Jaffa alone last year. Most of these were sent to the
Liverpool market, with smaller amounts, and of poorer grade, to
Turkey, Egypt, and other near-by countries. In all the earlier
plantings around Jaffa the trees are very close together — 9 to 12
feet. In the later plantings, however, and particularly in the Jewish
colonies, where all the best groves are located, they are from 14 to
18 feet apart. Irrigation is by the basin system, and the source is
from wells, from which the water is pumped, in the Jewish colonies,
by gasoline engines. On account of the sandy soil largely, water is
applied every 8 or 10 days. The methods of packing and shipping
are much the same as in Italy and Spain. Mr. A. Bril, a prominent
grower and manager of the Jewish colonies around Jaffa, who visited
the United States last year, has adopted California methods, and the
fruit so handled and packed brought 25 cents a box more than other
fruit.

Aside from Jaffa there is another small section around Acre,
farther to the north and also along the Palestine coast. Still farther
north in Syria there are citrus sections at Saida and Tripoli, there
being a considerable lemon acreage in the latter place.

In Egypt citrus culture is limited to scattering groves, most of
which are poorly cared for, and from which the production is limited
to local consumption.

METEOROLOGICAL DATA FOR VALENCIA, SPAIN, AND PALERMO, ITALY.

Since meteorological conditions may have a very great influence
on many msects, as has been specifically pointed out in the case of
the black scale, the following data are given for the most important
orange and lemon centers, respectively, of the 'Mediterranean
countries.

It will be noted from the following tables that, exceptmg 1910,
higher temperatures prevailed at Palermo than at Valencia. High
temperatures at Palermo, moreover, are accompanied by extreme
dryness, and usually much wind. This combination of heat and very
great evaporation is sufficient to account for the scarcity of the black
scale in Sicily, as compared with Valencia, Spain. The writer is also
inclined to attribute the scarcity of the purple scale in Sicily to this
same cause. In the United States the purple scale thrives best in
Florida and the coast counties of southern California. While rather
high temperatures prevail in Florida, there is also much humidity.
The distribution of the purple scale at present in the United States is,

CITRUS FRUIT INSECTS IN MEDITERRANEAN COUNTRIES.

35

therefore, limited to sections of more or less moisture. In this re-
spect it is like the black scale, but the black scale does not thrive so
well in high temperatures, even if accompanied by much moisture.
The purple scale does not yet occur in the interior counties of southern
California or m the great valleys of that State. Of course this may
be due to the close quarantine that has prevailed in those sections in
recent years against the purple scale. But judging entirely from
its present distribution, the purple scale appears to be restricted to
regions of more or less moisture, or at least to those in which the
combination of high temperatures and low humidity does not prevail.

Temperatures at Valencia, Spain, and Palermo, Italy, Janxiary, 1910, to August, 1913,

inclusive.^

Valencia, Spain.

Maxi-
mum.

Mini-
mum.

Mean.

Palermo, Italy.

Maxi-
mum.

Mini-
mum.

Mean.

January

February. .

March

April

May

June

July

August

September.

October

November .
December. .

January

February . .

March

April

May

June

July

August

September .

October

November.
December. .

January

February . .

March

April

May

June

July

August

September.

October

November .
December. .

January. . ,
February .

March

April

May

June

July

August

1910.

1913.

72
79
70
83
S4
95
102
99
84
81
79
72

71
77
84
75
94
86
97
100
96
86
79
70

92
93
105
93
80
70

70
71
73
79
93
87
106
92
83
79
74

65
67

' 84
79
85
88
95

107

1 In converting centigrade into Fahrenheit, fractions have been discarded.

WASHINGTON : GOVEKNMENT PRINTING OFFICE : 1914

ADDITIONAL COPIES

OF THIS PUBLICATION MAT BE PROCURED FROM

THE SUPERINTENDENT OF DOCUMENTS

GOVERNMENT PRINTING OFFICE

WASHINGTON, D. C.

AT

■ 15 CENTS PER COPY

BULLETIN OF THE

No. 156

Contribution from the Bureau of Entomology, L. O. Howard, Cfiief.
January 27, 1915.

(PROFESSIONAL PAPER.)

WIREWORMS ATTACKING CEREAL AND FORAGE

CROPS.

By J. A. Hyslop,

Untiinioloyical Assistant, Cereal and Foviuk Insect Inrcstif/ations.

INTRODUCTION.

Wireworms are the larvae of several kinds of hard-shelled beetles
belonging to the family Elateridae. The beetles are known collo-
(|uia]lv as " click-beetles," " skip-jacks," snapping beetles, etc.^
These names are all derived from the beetles' unique habit of snap-
ping the forepart of the body when placed upon their backs or held
between the fingers. This habit is undoubtedly of use to the beetles
in righting themselves when accidently overturned, and rv y also be
a means of escape from their predatory natural enemies.

Wireworms are elongate, more or less cylindrical, having a very
highly chitinized cuticle, and measuring, according to the species,
from one-half inch to over 3 inches in length. They have three pairs
of short legs near the anterior end of the body. The color is usually
yellow or reddish-brown. The cotton and corn wireworm is an
exception to this description.

The false wireworms (fig. 1, a) will also answer to the above
description, but can easily be distinguished by their ability to move
very rapidly and by the clavate last joint of the antennse; the t*ue
wireworms, though able to move rapidly in the soil, are not ve?y
agile wdien placed on the surface of the ground, and their antennae
never have clavate terminal joints. The term " wjrewQrm " is also,
though erroneously, applied to these false wireworm^, which are.
how^ever, the larvae of another group of beetles, the darkling beetles
(Tenebrionidae). These beetles can not snaj^ the forepart of the
body. One species of darkling beetle (Tenehrio molitor L., fig. I,?;)
is common throughout the United States, and its larva, the meal-

■ : TTT^

1 The Cherokee Indians recognize the larse-eyed elater (Aioi/s sp.) by tU«, i\«me
" tulskuwa," which means " one that snaps with his head." This interesting note was
made by Dr. .7. W. Fewkes and communicated to the writer by Mr. F. M. Webster.
01121°— Bull. 1.56—15 1

BULLETIN 156, U. S, DEPARTMENT OF AGEICULTUEE.

worm, is found in granaries and warehouses, -where it feeds upon
stored products. Another genus (Eleodes) is found only in the ter-
ritory west of the Mississippi Eiver, and attacks cereal crops in the
field. The name " wireworm " is also incorrectly applied to several
species of millipedes {Julus spp., fig. 1, c).

The true wireworms, from an economic standpoint, are among the
five worst pests to Indian corn and among the twelve worst pests to
wheat and oats. They are also important pests to many other crops.
Since 1841, when Dr. Thaddeus Harris first published an account of
these insects,^ the literature of economic entomology has been replete
with references to their depredations, and from the standpoint of the

entomologist, as to the diffi-
^^ culty of combating them,
they probably rank second
only to the white grubs
{Lachn osterna spp. ) .

In view of the recently
enacted Federal quarantine
bill these insects assume an
added interest, inasmuch as
they can easily be introduced
in the larval condition with-
in fleshy roots, bulbs, and
tubers. Mr. E. R. Sasscer,
of the Federal Horticultural
Board, recently intercepted
an elaterid larva in the root
of Aral! a cor data from Ja-
pan; the larva was in good
condition and is still alive
in our laboratory (October,
1914). The writer has often
seen the larva? of zigriotes
mancus Say within potato tubers that had been in a root cellar all
winter.

These insects are destructive to cereal and forage crops in the
larval stage only, although the adults of certain species {Lhnonius
discoideus Lee, etc.) do considerable damage to the blossoms of fruit
trees in the Pacific NorthAvest. and Fletcher reports- similar depre-
dations of the adults of two other species {Corymhites caricinus
Germ, and C. tarsal^ Melsh.). The forms attacking cereal and

7>j7r

Fio. 1. — Larv:r likely to be mistaken for wire-
worms : a, False wireworm ; h, mealworm ;
c, Julus sp. All enlarged. (Original.)

1 Ilarri*!, T. W. Report on the Insects of Massachusetts Injurious to Vegetation,
p. 40-50. Cambridge, 1841.

- Fletcher, James. Report of the Entomologist and Botanist, Central Experiment Farm,
Canada, for 1892, p. 4. Ottawa, 1892.

WIEEWORMS ATTACKIIsrG CEREAL AND FORAGE CROPS. 3

forage crops confine their attention to the seed, roots, and under-
ground stems and are exchrsively subterranean, with the single excep-
tion recorded by Mr. E. O. G. Kelly, of this office, wherein he mentions
finding a sjjecies {Monocrepidius vespertinus Fab.) damaging wheat
at Wellington, Kans., by boring in the hollow of the wheat stems
and not among the roots.

Their depredations are first to be noticed, w4th the exception of
the cotton and corn wireworm, immediately after seeding, when they
attack the seed, eating out the inside and leaving only the hull.
When they are very numerous they often consume all the seed, mak-
ing reseeding necessary, and in severe outbreaks a second reseeding
is sometimes made before a stand is obtained. Aside from the extra
labor and cost of the seed, this delays the planting of the crop, and
if it be corn, in the Northern States the season is too short to ma-
ture so late-planted a crop and, except for the fodder, it is a failure.
Where wireworms are present, even in very small numbers, corn
will make a poor stand, which will necessitate the planting-in of
missing hills. In some regions where these insects are quite numer-
ous it is customary to sow three or four times the amount of seed
that would normally be necessary in order to get a good stand.

KINDS OF WIREWORMS.

Several hundred species of Elaterida? occur in North America.
They vary enormously in their habits, some forms living in dead and
rotten wood (Alaus, Elater, Adelocera, etc.). Alaus has also been
recorded as boring in solid wood, though the writer is inclined to
discredit this observation, and other species live under moss (Seri-
cosomus). A number of species abound in heavy moist soil filled
with humus (Melanotus, Agi'iotes, etc.), while some prefer well-
drained soils (Corymbites), and still others (Horistonotus) are most
destructive on high sand}^ land which is very poor in humus. ^Nfany
wireworms have been recorded as predaceous (Alaus, Hemirhipus,
Adelocera, etc.). I am told by Mr. T. H. Jones, recently associated
Avith the Eio Piedras Sugar Planters' Experiment Station, that the
large luminous elaterid [Pyrophorus luminosus Illiger) of the West
Indies is a decidedly beneficial insect, as it feeds on the Lachnosterna
larv;o in the sugar-cane fields. Through the kindness of Mr. G. N.
Wolcott and Mr. R. H. Van Zwalenburg I now have (October, 1914) a
Pyrophorus larva from Cuba, one from Jamaica, and several from
Ma3^aguez. P. P. All of these larva^ are living and apparently thriv-
ing on the larvae of our native Lachnosternas. That this insect may
some day be introduced into the southern Ignited States as a natural
enemy of Lachnosterna is not at all improbable. At least one instance

BULLETIN 150, U. S. DEPARTMENT OF AGRICULTURE.

has been noted ^ in which a wireworm [Lacon {Agrypnus) mu7'inus
L,] lived in the stomach of a child. Most of our common species lay
their eggs on sod or A-ery weedy land, but the wireworms {Corymbites
spp.) of the dry-farming country of the Pacific Northwest are severe
pests on land that has been seeded to wheat, by the summer fallow
method, for the past 15 years, and, as this land was originally sage-
brush prairie, it probably never was in sod.

Several distinct kinds of true wireworms are destructive to cereal
and forage crops in the United States: and since, as has already been

stated, the different kinds vary more
or less in their life histories, there is
consequently a variation in the method
of control as recommended in the fol-
lowing pages of this bulletin. It is
therefoi-e quite necessary to determine
the identity of the wireworm. and to
meet this necessity the many species
of importance as pests to cereal and
forage crops are treated separately.

THE WHEAT WIREWORM.

(Apriotes maiicuf< (Say), fij;. 2.)

Fig. 2. — The wheat wireworm
(Aijriotes mancus) : a, Adult bee-
tle ; h, larva ; c, side view of last
segment of larva. All enlarged.
(From Chittenden.)

The adult of the wheat wireworm is
a small brown beetle a little over one-
fourth of an inch in length, quite
robust, and moderately covered with
XQvy short, fine hair. The larva is
pale yellow in color, very evenly cylin-
drical, and very highly polished.
When full grown the larva measures
about an inch in length and is about
as thick as the lead in a lead pencil. These wireworms will be
readily recognized by the singly pointed ninth abdominal segment
and the two black spots on the upper side of this segment near its
base.

This is one of the most common wireworms of the northeastern and
middle western United States. A report of this species as a pest in
the dry-farming regions of Washington State- is undoubtedly a

^ Sandberg, G. El tilfalde af Coleopterlarvers tilhold i tarmkanalen hos et Menneske.
Ill Entomologisk Tidskrift. v. 11. p. 77-80. 1800.

= Scobey, J. O'B. Wireworms. Washington Experiment Station. (State Agrieultural
College and School of Science.) Bulletin 4, p. 75-80, 3 figs., Ma.v, 1892.

WIREWORMS ATTACKING CEREAL AND FORAGE CROPS. 5

misidentification, the insect probably being C orymhites sp. The
wheat wireworm is normally a grass feeder, living on the roots of
sod, and with the abundance of its natural food supply producing
no appreciable disturbance in the meadows, but when the sod land
is broken these wireworms concentrate in the drill rows or hills of
corn, the usual crop to follow sod in the eastern United States, and
often cause absolute failure of the crop by destroying the seed
and eating off the roots of such plants as may germinate. This
species is usually more destructive, therefore, on land recently broken
from sod. Last year (1913) the writer investigated an outbreak in
northern New^ York and located as many as 10 wireworms to the hill
in cornfields, rendering the crop, so far as grain was concerned, an
absolute failure. This year (1914) the same field was again planted
in corn, and again the wireworms destroyed most of the crop.

The larva? spend three years in the soil before transforming to
beetles, so that the depredations of this pest may be looked for during
the second season as well as the first following the breaking of sod.

l.IFK HISTORY.

The beetles are in evidence early in the spring, and at this
time can be swept from wheat and, in fact, from any vegetation
around the fields, or they may be found under boards and rub-
bish. Mating occurs during April and May, and immediately egg-
laying begins. The eggs are deposited in grasslands exclusively, so
far as our observations go, the female burrowing into the ground or
under rubbish to oviposit. The young larvae feed during the ensuing
summer, and, hibernating when about half grown, resmne feeding
the following spring. They continue to feed during the second
summer and hibernate the second winter as full grown or mature
larvtie. The third' spring they resume feeding and continue it until
early in July, Avhen they leave the plants and form small earthen
pupal cells in tlie soil.

In 1913 Agriotes started to pupate about July 15 in northern New
York. The writer found many mature larva^ and pupjB in the fields
at Bridgeport, N. Y., on the shore of Lake Oneida, on July 17, while
investigating a severe outbreak of this pest on the farm of Mr. C. J.
Fisher. Other larvw collected at Bridgeport pupated as late as
August 12. In 1911 several hundred larvie were reared in the
Hagerstown laboratory. All that became adult this year pupated
between the middle and the end of July. The pupal stage varied
in duration from 15 to 21 days.

Specimens collected by ]Mr. J. J. Davis, of this bureau, at Water-
town, Wis., pupated on August 8. Mr. Pettit found the pupa? in

6 BULLETIN 156, U. S. DEPARTMENT OF AGRICULTURE.

the rearing cages on August 26 and adults emerged as late as the
middle of September at Grimsby, Ontario, Canada.^

The pupal stage usually lasts from 15 to 19 days. One specimen
collected at Watertown, Wis., by Mr. Davis pupated on August 8
and the adult emerged August 19. A specimen collected at Bridge-
port, N. Y., pupated on August 12 and emerged September 1. Other
specimens collected July 25 at the latter place became adult Au-
gust 12.

The pupal chamber consists of an oval cell, the long axis of which
is perpendicular, located at a uniform depth of about 5 inches be-
low the surface of the soil. The dust mulch in the case under dis-
cussion was 4 inches deep and the pupal cells were about 1 inch
deeper than cultivation in the moist, firm soil. The pupa stands
erect in the cell with the head upward, the larval exuvium being
at the Ijottom of the cell.

The adult evidently passes the remainder of the summer in the
pupal cell, in which it also later hibernates. Matured adults were
found in these cells in the fields at Bridgeport, N. Y., as late as
September 15, and in our rearing cages adults passed the winter
without feeding or drinking.

Three distinct generations of larvae were collected in the field in
the summer of 1913 — full-groAvn larvae about to pupate, half-grown
larva?, and larva? about one-fourth inch long — actively feeding on
the corn. We have now in the laborator}^, subject to outdoor tem-
perature, two distinct generations of larva? collected in the summer
of 1913. The first generation — that is, the largest larvje collected — all
transformed to adults during August. Mr. Pettit and several others
have made similar observations, and there is no doubt that this
species, at least in the northeastern United States, spends three years
as a larva.

FOOD PLANTS.

Agr totes 7nancus was observed at Bridgeport, N. Y., feeding upon
corn seed and roots, potato tubers, Avheat roots, carrots, and the un-
derground stems of string beans; a single specimen was also found
within the stem of the common field mushroom {Agaricus campes-
tris). Other writers have found it attacking the cucumber, turnip,
and cabbage. Mr. Theo. Pergande, of this bureau, records - a larva
of this species feeding on the larva of a lamellicorn beetle in one of
his rearing cages. The writer is of the opinion, however, that nor-
mally this species is not predaceous.

^ Pottit, J. Description of the wlioat wireworm {Agriotes manendi Say>. In Canad.
Ent, V. 4, No. 1, p. 3-6, fig. 1, January, 1872.

- U. S. Dept. Agr., Div. Ent., Notes, v. 4, No. 2795, Oct. 5, 1882.

WIEEWORMS ATTACKING CEEEAL AND FOEAGE CEOPS. 7

REMEDIAL MEASURES.

iWe recommend plowing sod land immediately after the first
hay cutting, usually early in July, Avhen the land is intended for
corn the following year. This land should be cultivated deeply
throughout the remainder of the summer. Land that is in corn
and badly infested should be deeply cultivated even at the risk
of slightly "root-pruning" the corn. This cultivation should be
continued as long as the corn can be cultivated, and as soon as the
crop is removed the field should be very thoroughly cultivated before
sowing to wheat. In regions where wheat is seeded down for hay
any treatment of infested wdieat fields is precluded. Where wheat is
not followed by seeding, the field should be ploughed as soon as the
wheat is harvested.

Thorough preparation of the corn seed bed and a liberal use of barn-
yard manure or other fertilizer will often give a fair stand of corn in
spite of the wireworms, a vigorous plant often being able to produce
]"oots enough to withstand the depredations of several wireworms.

Though we realize that usually this is not practicable, the inter-
posing of a crop not severely attacked by wireworms, such as field
peas and buckwheat, between sod and corn would materially reduce
the number of wireworms in the soil when the corn was planted.

THE CORN AND COTTON WIREWORM.

(Iloristonotiis uhlcril Horn, fig. 3.)

The adults of the corn and cotton wireworm are small, slender,
and dusky brown; the largest is a trifle over three-sixteenths of
an inch in length and can easily be distinguished from other forms
infesting cereal crops by the heart-shaped scutellum. The wire-
worms of this tribe (Cardiophorini) are very unlike any of the other
wireworms. They are not hard and wiry, l)ut soft, membranous, and
elongate. The body, which is usually white, appears to be composed
of 26 segments, every third segment being swollen. The last segment
is simply pointed. The head, which is yellow, is long and slender,
with a pair of A^ery prominent dark-brown jaws. AMien full grown
these wireAA'orms measure about an inch in length and are but little
thicker than j^ack thread.

Unlike most of the eastern wireworms, which are usually most de-
structive in damp, low-lying fields, these insects seem to be far more
numerous on the higher parts of the fields in light sancl}^ soil.

These wireworms are among the most troublesome species of the
southern United States. Mr. W. A. Thomas records ^ one species of

1 Thomas, W. A. Corn and Cotton Wireworm {Horistonotus ouriatus Say). So. Car.
Agr. Exp. Sta., Bui. 1.55, 10 p., figs. [i. c.., pis.] 6, March, 1911. I have since been
informed by Mr Conradi that this is a misldentification and that the species in question
is H. uhlcrli.

8

BULLETIN 156, U. S. DEPARTMENT OF AGRICULTURE.

this genus {II orktonotus curiatus Say) as one of the worst pests in
South Carolina.

Mr. Vernon King, of this office, is at present investigating a very
serious outbreak of Iloristonotus uhlerii in Missouri and has pre-
pared the following preliminary account of this species :

Iloristonotus iitilerii Horu is a serious pest
to corn iu so iitli eastern Missouri, and to
corn, cotton, and cowpeas in northeastern
Arkansas, and has been reported from the
Carolinas and Illinois.

The larvae may be found about the roots
of their host plants in large numbers, nearly
50 having been taken from one hill of corn.
Adults, pupje, and larvse can be seen iu June,
all beneath the surface of the soil, and later
the adults' will be found above the ground,
resting on the plants. The eggs are probably
laid about the end of June in the soil, on or
about the roots of corn and cowpeas, for
minute larvjB have been taken early in .July.
In May and June the larvte are most plenti-
ful, but as the season advances they become
scarce, and finally disappear by the time
winter sets in. By the third week in August
the adults can no longer be found. Under
laboratory conditions the larvae pass the
winter partly grown, and no doubt in nature
they hibernate in the same form, but in
what location is not yet known.

Although corn, cowpeas, and cotton are
the main hosts of this insect, the larvte feed
on the roots of Johnson grass {Sorghum
halepcnsc) and have been reported as feed-
ing on crab grass.

Infested corn plants become wilted and
stunted, with leaves of a bluish shade, and
brown at the tips, standing out from the
stalk stiffly instead of bending over grace-
fully as in a healthy plant. Deprived of
most of the roots through the work of the
larviB, the plant can be inilled up with little
effort. Weak individuals soon succumb, leaving gaps in the rows, but the
more vigorous plants put forth new roots in abnormal numbers. These are
matted together and distorted, and although the plants survive, only nubbins
are produced. Tall and apparently healthy plants may have larvce among the
roots without damaging the corn materially. The infestation, therefore, is
not confined to the impoverished areas.

In cowpeas the fibrous roots suffer most, the thicker roots being perforated,
so that the plants become yellow and dwarfed and fail to vine.

Cotton is injured in the early stages by tlie larvjTe boring into the seed and
injuring the very young plants, checking the growth so much that the plant
dies or struggles along only to produce little or no cotton.

Fig. 3. — The corn and cotton wire-
worm (Horiaionoius uhlerii) : a.
Adult beetle; h, larva. Enlarged.
(Orisinal. i

WIREWOEMS ATTACKING CEREAL AND FORAGE CROPS. 9

Rolling laud infested by tliis insect presents a patchy appearance, the sandy
knolls standing out distinct and bare, being overgrown later with weeds, par-
ticularly crab grass, briers, and morning-glory.

The infestation seems to be worst after a crop of cowpeas, but the
exact significance of this crop in relation to wireworm injury has yet to
be determined. Applications of barnyard manure and of wood ashes have had
no effect in checking this pest. On account of the susceptibility of the larvae
and pupae to exposure, plowing the soil in the heat of the sun would un-
doubtedly destroy many of the wireworms. The objection to this method,
however, would be that the planter is occupied with other farm operations at
that time, and also there would be difficulty in getting at these areas, which
are often scattered, irregular, and isolated. From the data thus far gathered
we can not say what effect fall plowing would have on this insect. Further
investigation, however, will in all probability give a clue to remedial measures.

WIREWORMS OF THE GENUS CORYMBITES.

In the literature of American economic entomology there is no ref-
erence to beetles of the genus Corymbites as pests to cereal and forage
crops. In the Pacific Northwest two species (C. infatus Say and C.
noxious Hyslop) are among the worst pests to cereal crops. The
habits of the two ^^ecies are quite distinct and will be treated sepa-
rately. The occurrence of Corymhites cylindriformis Hbst. in enor-
mous numbers in alfalfa and wheat fields about Hagerstown, Md.,
this spring (1914), and the finding of Corymbites larvee in these
fields at various times, might indicate that the genus is represented
among the cereal and forage pests in this region also.

In Europe the habits of several species of this genus have been
recorded by Schiodte and Perris. C. pectinicornis L., C. castaneus
L., and C. sjlandicus Miill. are found living in woody meadows and
C. ceneus Fal. is found in fields.^

C. latus Fab. is recorded - as living " in the ground like other insect
larvae, feeding on roots * * *^ They cause great damage to car-
nations in flower gardens." Following is a note by Mr. Pergande
from the Bureau of Entomology files : ^ " Elaterid larva in apple tree,
received from B. C. Hawkins, Horse Cove, Macon County, N. C. A
larva of an elaterid found in a boring in trunk of apple with a dead
larva of Saperda hirittata.''''

This note, though the correctness of the determination of the wire-
worm is not certain, is interesting, inasmuch as it seems to indicate
that some species of Elateridse now classified as Corymbites are

1 Schiodte, J. C. Dc metamorphosi eleutheratorum observationes, pt. 5, p. 520-522, pi.
8, fig. 9-10, pi. 10, fig. 4, 1871.

- Perris, fidouard. Larves des ColSoptferes, p. 179. Paris, 1877. " Cette larve vit dans
la terree soit d"autres larves ou inseetes, soit de racines. M. de Bonvouloir, en m'en en-
voyant des echantillons, me I'a signalee comme causant de grands degats aux celllets de
son parterre."

= U. S. Dept. Agr., Div. Ent., Notes, v. 8. No. G187, .Vpr. .3, 1894.

61121°— Bull. 156—15 2

10 BULLETIN 156, U. S, DEPARTMENT OF AGRICULTURE.

predaceoiis, while other forms also in this genus are known to be
exclusivel}- vegetable feeders.

During the spring of 1909 a reconnoissance was made to determine
the extent and nature of the damage being done by these insects.
Circular letters with blank forms inclosed were sent to the agents of
the warehouse and elevator companies at most of the large grain-
shipping points in the Pacific Northw^est. These men are very inti-
mately in touch with the farmers and usually know of any serious
depredations that are likely to a^ect the production of grain. From
their replies we found that corn was being seriously damaged at
Spokane, Pullman, Kiona, Johnson, and Colville, in Washington,
and Latah and Mineral in Idaho ; oats were being almost completely
destroyed at Ritzville, Dow^ns, Espanola, Govan, and Vancouver, in
Washington, and Moscow and Latah in Idaho ; and that wheat was
being damaged at Wilbur, Connell, and Govan in Washington. The
fact that damage to wheat w^as not reported from more localities
does not signify that wheat is less susceptible to the attacks of these
insects. The buyers wall not report any damage to wheat for fear
of starting a scare among the farmers and thereby abnormally rais-
ing the price asked when the bujdng opens in the* fall.

THE INFLATED WIREWORM.

[ConjiiiJ)itvK hiftitlus Say.)

The inflated wireworm occurs throughout most of the northern
United States, but is limited as a pest to cereal crops, so far as our
observations now record, to the regions of eastern Washington and
Oregon and western Idaho, known as the semiarid Transition Zone
and characterized, when not under cultivation, by the presence of
bunch grass {Agropyron spicaturn) and June grass {Poa sand-
hergii) and by the absence of sagebrush. This region is only partly
summer fallowed, crops often being grown on the same land for
several consecutive years.

The beetle is robust, but little more than one-fourth of an inch
in length, and of a slate-gra}' color, sometimes being almost black.
The wireworm is about one-half inch long, depressed, with a pair of
backwardly directed spurs on the ninth abdominal segment, and pale
yellow.

In the spring of 1909 Mr. George I. Eeeves, of this bureau, re-
corded finding the larvae of the inflated wireworm damaging seed corn
at Pullman, Wash. His observations were carried on principally in
the cornfield of a Mr. Curtis, north of the town. On this farm he
found from 4 to 10 larva^" to the hill Avhen he first investigated the out-
break, on May 24, 1909. The wireworms were in various stages of

WIEEWORMS ATTACKING CEREAL AND FORAGE CROPS. H

development and were feedino- on the seed, which had l)eeu phmted
on May 10 and IT, eating out the kernels and leaving onl_y empty
hulls. Usually the roots of such plants as had escaped were not
damaged. The particular field under observation had been in oats
in 1908 and in wheat in 1907. On June 1 Mr. Reeves again ex-
amined this field and then found the stand very poor, and the wire-
worms seemed to be more numerous than when he first examined it,
as from 18 to 20 were to be found in nearly every hill. At this point
the investigations were turned over to the writer.

On June 20 the entire field was harrowed and reseeded, the first
seeding being absolutely destroyed by these wireworms. The second
seeding started very well and looked as though it would succeed.
Many wireworms were still present, however, and by July 8 the
second seeding was about half destroyed and had to be planted in by
hand. The season was then so well advanced that the crop was
practically a failure.

LIFE HISTORY.

Early in May the beetles emerge from the pupal cells in which
they pass the winter, a number of beetles having been caught at
Pullman, Wash., by Mr. Eeeves as early as May 5, 1908. They
are about in enormous numbers during late May and early June.
On May 28, 1910, the writer collected over a hundred of these
beetles in a few minutes from some rosebushes in a fence row along
the side of a last year's wheat field. The beetles continue abundant
until early July, and by the middle of this month they have all dis-
appeared but a few^ stragglers. During June the beetles mate and
lay their eggs. The larva? feed during this summer and pass their
first winter about half grown. They resume feeding the following
spring and continue to feed during the second summer, passing the
second winter as nearly mature larvae. The larval life is completed
early the third spring, w^hen they transform to pupae during late
June and early July. The last transformation takes place in late
July and early August, and the adult beetles remain in the pupal
cells from that time until early the fourth spring. Thus the wire-
worm, as such, is in the gi-ound during the growing season of three
years.

FOOO PLANTS.

The beetles of this species were observed in large numbers during
May, 1910, at Pullman, Wash., on wild rosebushes, where they were
apparently eating the petals of the unopened rosebuds, as many as
10 beetles having been counted on a single bud and the buds beins

12

BULLETIN 156, U. S. DEPARTMENT OF AGRICULTURE.

badly riddled with holes. In a rearing cage the beetles were ob-
served eating into kernels of wheat which were exposed on the sur-
face of the ground. The beetles are also to be collected in large num-
bers in clover fields. The larva^, so far as our records show, attack
corn, wheat, and potatoes. They also undoubtedly attack oats and
barley.

THE DRY-LAND WIREWORM.

( Cory in bites noxius Hyslop/ fig. 4. )

The dry-land wireworm, so far as we at present know, is confined
to the Upper Sonoran Zone of Washington State, though it will un-
doul)tedly be found in the Upper Sonoran of Oregon. This zone is

Fig. 4. — The dry-land wireworm {Corytribitcs noxius) : a, Adult ; h, larva : c, iiudcr sur-
face of head of larva ; d, side of last segment of larva, a, h, enlarjjod : c, <}, more
enlarged. (Original.)

characterized by the presence of sagebrush and occupies that part of
Washington lying south of the Columbia River, east of the Cascade
Mountains, and west of the semiarid Transition Zone, extending up
the Snake River into Idaho and across the Columbia River into
Oregon. This region is almost exclusively dry-farming country,
summer fallowing being necessary to obtain enough moisture to
mature Avheat and other cereals.

1 llyslop, J. A. Description of a new species of Corymbites from the Sonoran Zone of
Washington State (Coleoptera, Elateridse). In Proc. Biol. Soc. Wash., v. 27, p. 69-70,
Mar. 20, 1914.

WIREWORMS ATTACKING CEREAL AND FORAGE CROPS. 13

The beetle of this species is about one-half inch long, quite slender,
and jet black in color. The wireworm is very similar to the inflated
wireworm.

Early in April, 1910, our attention was called to a series of severe
wireworm outbreaks in the region above outlined. On the 5tli of the
month the farm of a Mr. Dunnigan, at Connell, Wash., was visited. He
was at that time reseeding 1,800 acres of wheat which had been killed
out by these wireworms. From Connell we proceeded to Govan, Wash.,
and here we found the wireworms also doing considerable damage.
In a fallow field that had been ruined by wireworms when in oats in
1909 we found them in enormous numbers. These wireworms when
in the field are usually to be found between the dust mulch and the
moister earth below. This species is more or less destructive tlirough-
out its range. During 1910 reports of severe outbreaks were received
from eight wheat-receiving stations in the States of Washington and
Idaho.

LIFE HISTORY.

This beetle is about during June and July, at which time it
deposits its eggs in wheat fields, weedy fallow fields, and volunteer
wheat on fallow land. The eggs are undoubtedly laid underground
by the female burrowing into the soft earth, as many adults were col-
lected in the fields at a depth of from 5 to 8 inches below the surface
which were not in pupal cells. Mr. J. E. Graf, of the Bureau of
Entomology, has found this to be the case with the sugar-beet wire-
worm.- The young larva3 are to be found in the soil during August
and the remainder of the summer, but their depredations are not
noticeable at this time, as, in the region where the species occurs,
wheat is the only extensively grown crop. The young wireworms
pass their first winter in the soil at a depth of from 12 to 20 inches
below the surface. The following spring and summer they spend in
the summer fallow and are not noticed. Their second winter they
again hibernate as wireworms, and in the spring of their third year,
the field being now planted to wheat, they turn their attention to the
seed and young plants, and it is at this time that their depredations
are so startlingly noticeable. They feed during late March, April,
and May, and early in June burrow to from 1 to 8 inches below the
surface, making small oval cells, in which the very fat larvae lie in
an inactive condition during June, Jul}^, and early August, when
they pupate and the adults emerge from the pupal skins the middle
of that month, but remain in the pupal cells the remainder of that
summer and the ensuing winter, not emerging from the ground until
the fourth spring from that in which the eggs were laid.

- Graf, .John E. .V PreUminary Report on the Sugar-Beet Wireworm. U. S. Dept..
Agr., Bur. Ent., Bui. 123, p. 18, Feb. 28, 1914.

14 BULLETIN Llf), U. S. DEPAETMENT OF AGRICULTURE.

In the s[)rino; of 15)10 ;i large number of these larvae Avere col-
lected in the wheat fields at Govan and Wilbur, in Washington State,
and confined in a root cage made by sinking a molasses barrel to the
level of the earth surface in a field at Govan and closing the top with
a short cylinder of sheet iron covered with wire gauze. The barrel
was filled with earth and wheat planted therein. The larva' could
easily be separated into three distinct groups, according to size,
which indicated a ?> years' life cycle. Later observations on the mate-
rial in the rearing cage proved this to be actually the case.

Two lots of larvge were confined in this cage — one on April 14
and the other on April 30, 1910, so that all must have hatched from
eggs laid in 1909 or previous to that year. On June 21 the cage was
examined and a nimiber of the larva? were found to be at from 4 to
8 inches below the surface, resting quietly in oval cells. They were
very fat at this time. The cage was not examined again until No-
vember 4, and at this time 3 adults, evidently of the 1907 genera-
tion, Avere found at about the same depth as the larva? observed in
June. They were still in the pupal cells, as was evident from the
last larval skins and the pupal skins found with them. The fol-
lowing spring (1911) the cage was examined on March 29, Several
larv^ were found at this time. They were now moving actively
about in the soil and almost immediately attacked some seed wheat
sown in the cage on this date. An adult still in the pupal cell was
also found at this time. The cage was next examined on July 4,
at which time an adult was found on the surface of the ground.
Several full-groAvn larvpe were also foinid on this date in their cells
at the usual depth of from 4 to 8 inches below the surface. These
were evidently the larva? hatched from eggs laid in 1908. On Au-
gust 17 the cage was examined and at about 5 inches below the sur-
face a pupa and an adult were found. The latter had evidently
just transformed, as it had not yet become quite black and was still
very soft. The following day the cage was entirely emptied and at
between 18 and 20 inches below the surface 10 larval' and an adult
were found in soil that was very hard, and very slightly moistened,
in fact merely moist enough to prevent its being absolutely dry.
The larvae seemed to be full grown and had evidently just completed
a molt, as they were quite soft. These were evidently of the 1909
generation.

RKMKDIAI. MKASURKS.

As will be seen from the life histories of these two species, the
generations about to become adult are inactive larvte from June
to August and very delicate pupae during the early part of the
latter month. These resting larvae and pupa? are usually at a
depth of from 4 to 8 inches below the surface, and any disturb-

WIEEWORMS ATTACKING CEREAL AND FORAGE CROPS. 15

ance of the soil to that (lei)th at this time woiihl undoubtedly de-
stroy them. At this time of the year the ground is very hot and
the air exceedingly dry in this region, and even the resting larvge
and pupa? that were not actually crushed by the cultivation would
soon succumb to drying when their cells were broken open. The writer
had considerable trouble in bringing pup» in from the field to his
rearing cages and was forced to resort to tightly closed tin boxes
which were fitted in the bottom with moistened blotters.

The usual farm practice in the region where the drj^-land wireworm
is troublesome may be roughly outlined as follows: Immediately
after seeding the wheat in early spring the fallow land is plowed to
a depth of from 4 to 7 inches. This is usually in April, but if
horses and help can be spared from seeding, the summer fallow is
plowed as early in the spring as the land can be worked. The next
operation on the fallow land is disking it late in June or early in
July to maintain the dust mulch and kill out the weeds and volun-
teer wheat. Many of the more progressive farmers now advocate,
and a few practice, fall plowing of stubble and only disking the
fallow land in the spring. The year following the summer fallow-
ing the field is disk harrowed early in the spring if the land has run
together during the winter and is caked; otherwise the land is har-
rowed with a drag or spike-tooth harrow. It is then seeded and
dragged and receives no further treatment until harvest. The seeder
is usually set to sow at a depth of about 3 inches, though if the
moisture is high enough 1 inch is sufficient. Wheat hay is used
extensively in this country and is cut while the wheat is in the
-dough, which is usually from July 4 to 15. The wheat crop is har-
vested from the 1st of August until the 1st of September.

We recommend altering this practice in order to destroy wire-
worms in the following manner:

(1) Dish or drag harroiv the summer fallow as early as possible
in the spring^ in order to produce a dust mulch and thereby con-
serve the accumulated winter's moisture: (2) continue dishing as
often as is necessary to maintain the dust mulch and keep down the
weeds; (3) plow the summer fallow in July or early in August,
and immediately drag; (4) plow the stubhle as soon as the crop
is off.

As these worms are of three different ages in most infested fields,
and as only about one-third of these will be in the pupal stage each
year, it is evident that the first year of this practice will not show
startling results. However, if the practice is continued for a couple
of years it will undoubtedly reduce the number of these pests very
considerably. Aside from its beneficial results in killing insects, this
method of handling the land will materially reduce the weeds. The
■early disking merely softens up the soil and allows all the weed

16

BULLETIN 156, U. S. DEPARTMENT OP AGRICULTURE.

seed present to sprout, and the entire crop of weeds is subsequently
destroyed by the summer plowing. By the present method of farming
the Aveed seeds are turned down to such a depth that many can not
germinate, but lie dormant and sprout Avhenever they happen to be
brought to the surface b}^ subsequent cultivation. One crop of weed
seed is in this manner often a pest for several succeeding years.

A slight variation of these suggestions will readily adapt them
to the more humid sections inhabited by the inflated wireworm.

THE CORN WIREWORMS.

Several species of beetles belonging to the genus Melanotus are
recorded as pests to cereal and forage crops in the United States.

The beetles usually range from
medium-sized to large forms
measuring from one-half to
three-fourths inch in length.
They varj^ in color from light
reddish-brown to almost black.
The beetles of this genus can
always be distinguished with
a low-power lens by the comb-
like chiAvs on the last tarsal seg-
ment.

The wireworms are reddish-
brown in color, about IJ inches
long, cylindrical in shape, and
always with the last joint of
the body ending in three incon-
spicuous lobes.

Many species of this genus in-
habit decaying logs, and several
writers record them as predaceous.^ A note in the Bureau of Ento-
mology^ files,^ by Mr. Pergande, records a larva of this genus as feed-
ing on the eggs of a locust, or grasshopper. A similar record,^ dated
September 19, 1884, is. made by the same observer, wherein a Me-
lanotus larva w^as found with locust eggs and reared to the adult con-
dition by feeding on potato and dead beetle (lamellicorn) larva^.

These wireworms are a pest to cereal and forage crops in the Mid-
dle Atlantic States, the New Enghmd States, and in the Mississippi
Valley from Kansas northward. Forbes places Melanotus comniunis

Fig. 5. — One of the corn wireworms (Mela-
notus communis) : a, Adult ; h, larva ;
c, last segments of same ; d, pupa. All
enlarged. (Prom Chittenden.)

1 Ferris, Edouard. Ilistoire des insectes du pin maritime. In Ann. Soc. Ent. Prance,
ser. 3, T. 2, p. 139 (seances du 13. Avril, 1853).

2 U. S. Dept. Agr., Div. Ent, Notes, v. 4, No. 2883, Oct. 9, 1882.

3 U. S. Dept. .\gr., Div. Ent, Notes, v. 4, No. 2884, Sept. 19, 1884.

WIREWOEMS ATTACKING CEEEAL AND FORAGE CROPS. 17

Gyll. (fig. 5) and M. fssilis (Say) as among the important corn pests
of Illinois. Webster found M. communis a very serious pest in
Indiana and Ohio; Comstock and Slingerhmd consider M. communis
one of the worst wireworms in New York State ; and Swenlv records
serious depredations of M. ci^ibulosus Lee, M. communis^ and M.
fissills in Nebraska.

In 1907 Mr. E. O. G. Kelly found a species of Melanotus attacking
corn in North Dakota. In 1910 Mr. W. W. Yothers, of this bureau,
investigated a very severe outbreak of these wireworms at Corry, Pa.
At the time he visited the fields as many as 7 to 15 larva? were to be
found in nearly every hill. This field had been broken from sod in
1908. In 1912 Mr. Kelly found the larva? of Melanotus communis
so numerous at Wellington, Kans., that they entirely destroyed his
experimental corn plantings. He also found the larva? of this species
attacking kafir seed at Mulvane, Kans., in the spring of 1912. In
places they had completely eaten out the seed for spaces of from
4 to 6 feet in the drill rows. In 1911 we received reports of damage
by wireworms belonging to the genus Melanotus from seven localities
in Indiana, seven in Wisconsin, six in Maryland, three in Michigan,
three in Iowa, and one each in Alabama, Ohio, Virginia, Kentucky,
North Dakota, Vermont, and West Virginia.

Several species occur on the west coast, and M. communis is re-
ported as a pest to wheat in Garfield County, Wash.,^ but the writer
is inclined to believe that the pest in this case was either a false wire-
worm or a species of Corymbites.

Mr. Pergande records- this species as attacking lettuce roots,
wheat, and potatoes.

LIFE HISTORY.

The adults of these wireworms are flying about in late April,
May, and June, when they undoubtedly deposit their eggs in the
grasslands. The larvse spend two to five years in the soil. That any
have so short a life-cycle period as two years is not at all certain.
We have, however, in our outdoor insectary, larvae received from
Inman, Nebr., April 19, 1912, subject to very nearly natural con-
ditions. These larvae were well grown when received and were at
least of the 1911 generation. At the date of this writing (October,
1914) they are larvae. They have passed the summers of 1911, 1912,
1913, and 1914 in the soil, and if they pupate next summer (1915)
the adults will, without doubt, remain in the pupal cells until the
spring of 1916, making, in this case, five full years from egg to egg.
These beetles pupate during July and early August.

1 Scobey, J. 0"B. Wireworms. Wash. Exp. Sta. (State Agr. Coll. and School of Sci.),
Bull. 4, p. 75, May, 1892.

2 U. S. Dept. Agr., Div. Ent., Notes, v. 4, No. 2884.

61121°— Bull. 156—15 3

18 BULLETIN 156, U. S. DEPARTMEXT OF AGEICULTUEE.

Mr. Webster found pupso in the ground August 19, 1885, at La
Fayette. Ind.

At the Hagerstown Laboratory over 100 larvae of this genus are
under observation. Those that emerged as adults this year pupated
between the end of July and the middle of August. The pupal
stage varied in duration from 12 to 22 days.

The adults do not leave the pupal cells, however, until the follow-
ing spring. Mr. Webster found adults of M. communis in jnipal
cells on March IT, 1894, at Wooster, Ohio, and the writer found
an adult in a wheat field at Hagerstown, Md., on November 22, 1912.
This adult was in a cell with its pupal and last larval exuvia. The
cell was 1 inch below the surface, in the drill row in which several
consecutive plants had been killed.

KKMEDI AL M KASURES.

The larvfie of the genus Melanotus^ so far as our observations go,
are confined to poorly drained and usually to heavy, sour soil. In
making a survey of Birch Creek and Eel Creek bottoms in Clay
County, Ind., we were informed by nearly all of the farmers that up
to within the past four years wireworms caused very large annual
losses to corn growers, while for the past three years this pest has
been quite unknown to them. Coincident with the disappearance of
the wireworms we find that the land was tile-drained on most of the
farms. That the tile drainage of the land was actually responsible
for the disappearance of the wireworms is more than we are prepared
to say. However, the coincidence is very suggestive.

WIREWORMS OF MINOR IMPORTANCE.

The following species, though not serious pests to cereal and for-
age crops over extensive areas, are, during certain seasons, very
destructive in restricted localities.

The wireworms belonging to the genus Limonius are among the
most important of this group. In 1909 the writer received report of
serious damage being done to corn and potatoes at Spokane, Wash.
The outbreak was investigated and proved to be very severe, but at
the time no larva3 were reared. This year (1914), through the kind-
ness of Mr. William Tews, of Spokane, the writer received a large
number of these wireworms with the report of another serious out-
break. From this material we succeeded in rearing adults which
are Limonius (species undetermined). The confused wireworm
{Linionius confuKus Lee.) has made its appearance in Illinois^
within the last few years, and although its principal damage was
confined to potatoes, it w^as also destructive to corn. The beetle is

ipnvis, J. .1. rrelimi7iary roport on tbe more important insects of the truck gardens
of Illinois. In 111. I'armrrs' Tn*;t. 16th Ann. Rpt., p. 21fi-263, 42 flgs. Springfield, 1911.
W^irew'orms. Limonius confusus Lee, p. 251, flgs. R6--7.

WIREWOEMS ATTACKING CEREAL AND FORAGE CROPS. 19

about three-sixteenths of an inch long, reddish-brown in color, and
moderately hairy. The wireworm is about three-fourths of an inch
in length and is depressed, with a shallow emargination in the ter-
minal segment; the color, as in the beetle, is reddish-brown.

The species is recorded as attacking corn, potatoes, tomatoes,
onions, cabbage, radishes, turnips, horseradish, and spinach. It l)ur-
rows into the underground parts of the plants, quite ruining them for
market purposes, and in the case of corn, tomatoes, cabbage, and
onions often kills the plant. This species does not seem to attack
beans, peas, cucumbers, melons, rhubarb, lettuce, and peppers, and
these croiis might be of value in clearing a badly infested field prior
to seeding it to grain.

The sugar-beet wireworm {Limonius calif ornieus Mann.) is a
very serious pest to alfalfa and corn over restricted areas m Cali-
fornia.^ Alfalfa is so badly infested in certain localities that it
has to be plowed out and reseedecl every three or four years. This
species lays its eggs during late April. The eggs hatch during late
May and the larvae spend the remainder of that season and the whole
of the two succeeding seasons in the ground. They pupate during
July and August of their third summer, the adults remaining in the
pupal cells until the spring of the fourth year. Alfalfa fields badly
infested with this wireworm should be plowed out immediately after
the first crop is harvested and harrowed several times before re-
seeding. Land intended for corn should be plowed in late July or
August of the year preceding cropping. Land in corn should be
deepl}' cultivated during August.

The abbreviated wireworm {Cryptohypnus ahhreviatus (Say)) oc-
curs over the entire northern part of the United States, being quite
common in New England and New York, and is recorded from New
Jersey by Smith.'^ In the upper Mississippi Valley this species is
also a pest and specimens have been collected in Utah and Wash-
ington.

The beetles of this species are very small, being little over three-
sixteenths inch in length and quite broad and flattened. The color
is very dark brown to almost black and the forepart of the body is
very shiny. An obscure yellowish spot ornaments each wing cover
near the tip. The legs are also obscure reddish-yellow.

The wireworm is about one-half inch long, flattened, with a pair of
backwardly directed prongs on the ninth abdominal segment, and is
pale yellow in color.

Owing to the confusion of this wireworm with Drasterius elegans
Fab., the literature relative to either of these insects is very unre-

1 Graf, John E. A rVoliminary Rt'port of the Sugar-Bect Wireworm. T". S. Dept. Ag:r.,
Bur. Ent., Bui. 123, 68 p., 9 figs., 2.'5 pi., Fob. 28, 1914.

2 Smith, .1. B. Catalogue of the Insects Found in New Jersey, p. l."J9. Trenton, 1.S90.

20 BULLETIN 156, U. S. DEPARTMENT OF AGEICULTURE.

liable. The best account of the species of which we are cognizant is
that of Comstock and Slingerland.^

On March 13, 1912, Mr. J. J. Davis received a communication report-
ing a very bad outbreak of wireworms on corn at Watertown, Wis., in
1911. The fields attacked were low-lying peaty muck-lands that had
been reclaimed by tile draining. The correspondent said that he
" plowed up a strip of land early last spring and turned up these
insects by the millions, so that some of the furrows looked real
white." Larvae were inclosed with this communication and proved
to be of this beetle. In June, 1913, Mr. Davis visited this locality
and collected a number of the larvae and sent them to the writer
alive. They were confined in rearing cages on June 6, August 5 a
pupa was found, and on August 14 the adult emerged from the
pupa. Another larva pupated on September 2 and the adult emerged
on September 11. These two records limit the pupal stage to nine
days.

For this species we recommend plowing sodland, intended for corn
the succeeding year, during late August. Cultivate corn as late as
possible, and plow small-grain stubble during August, if possible.

Another genus of importance in this group is Monocrepidius. The
two species of this genus recorded as attacking cereal and forage
crops in the United States are quite distinct. One {Mo7ioc7'ep'idlus
limdus DeG.) is a large species over one-half inch in length, of a dull,
even brown color. It is shaped very much like a Melanotus, but can
easily be distinguished from that genus by the simple tarsal claws.
The other species {Monocrepidius vespertinus Fab.) is a small
elongate beetle, a little over one-fourth inch long. The body is prettily
marked with yellow and dark brown. Both of these species are more
or less southern in distribution, M. lividus DeG. being distributed
over the entire southern part of the United States from Florida to
Texas and northward to northern New Jersey, scattering specimens
being collected as far north as Massachusetts, while M. vesperti/iius
covers the same territory, but is more generally distributed north-
ward.

A third species, Monocrepidius hellus Say, is a very small form,
the beetle being hardly three-sixteenths of an inch long. This species
is quite often taken in cornfields during the summer and under stones
in pastures during the winter about Hagerstown, Md. Dr. F. H.
Chittenden^ records this species as having been reared from larvae
feeding on the roots of creeping bent (Agrostis stolonifera) on the
deparfment grounds at Washington.

1 Comstock, J. n., and Slingerland, M. V. Wireworms. Cornell I'niv. Agr. Exp. Sta.,
Bui. 33, p. 270, Nov., 1S91.

= U. S. Dept. Agr., Div. Ent., Notes, v. 10, No. 7472.

WIREWOKMS ATTACKING CEREAL AND FORAGE CROPS. 21

Monocrepidius auritus Hbst. is also quite common about Hagers-
town, adults being often found hibernating with Drasterlus amahlUs
Lee. under stones. Mr. C. M. Packard, of the Hagerstown laboratory,
collected a pupa of this species in the insectary garden on August 11,
1913. The adult emerged from this pupa on August 16. This year
(1914) Mr. J. J. Davis sent the writer a large number of larvae of
this sjDecies from Indiana. The last two species will probably eventu-
ally be found to attack crops.

The largest, and in the southwest the most important, species of
this genus is Monocrepidius lividus DeG. In the bureau files is a
note made by Mr. Pergande, dated June 6, 1881.^ Larva? were found
in hills of recently seeded sorghum. No locality accompanies this
note. On July 4 one of the larvae transformed to a pupa, and on July
11 the adult issued, making the pupal period just a week.

Mr. Kelly collected an adult in a hay pile March 21, 1911, and also
a larva of this species burrowing in a young corn plant at Welling-
ton, Kans., on June 11, 1910. This larva pupated on September 8,
but was not reared to an adult. He also collected an adult in an
alfalfa field on May 10 of that year. Another larva, supposed to be
this species, was collected June 12 and was kept alive in a rearing
cage until November 25, indicating that the species hibernates, in
the larval state. The particular specimen, however, died during the
winter.

During July, 1911, Mr. G. G. Ainslie found the adults of this spe-
cies on the fresh silk on the corn ears down in the tip of the husk.
He found them in the act of eating the corn silk and also the pollen.

The writer, while investigating an outbreak of the " curlew bug "
{Sphenophorus callosus Oliv.) at Hartford, N. C, found several of
these wireworms in a cornfield. These larvae were collected on No-
vember 4, 1911, and by December of that year one of the larva? had
eaten all his comrades and had gone into hibernation in the rearing
cage in the office at Washington. The data relative to the life history
of this individual can not be relied upon as of value in determining
the normal life history, as the office was subjected to great extremes
of temperature that winter, often freezing at night and being over
80° F. by noon. However, this larva transformed to a pupa and
emerged as an adult between May 21 and June 7, 1912. This beetle
lived in the rearing cage without food until July 24 of that year.
Mr. G. G. Ainslie collected a larva of this species on March 25, 1914,
in sod land at Orlando, Fla.

Undoubtedly second in importance, and in parts of the South
probably first, is the southern corn wireworm {Monocrepidius ves-
pertinus (Fab.) , fig. 6) . Mr. Kelly has found the larvae of this species

1 U. S. Dept. Agi-., Div. Ent., Notes, v. 2, No. 857, June 6, 1881.

22

BULLETIN 156, U. S. DEPARTMENT OF AGRICULTURE.

doing considerable damage to wheat at Wellington, Kans. These
lar\iv attaek the wheat in a very unicjue manner for wireworms.
They do not seem to attack the roots, bnt bore into the cavity of the
Avheat stem and feed on its inner wall. In some fields as many
as one-eighth of 1 per cent of the wheat stems were infested. A
large number of these larva? were placed in a rearing cage on
May (). 1910, and on June 24 four adults were found in the cage.
Mr. Kellv found the adult beetles of this species numerous on corn
plants in the field from July 3 to August 23. Early in March, 1910,
an adult of this species was found in a clump of grass {Andropogon
scoparhvs). In 1911 Mr. Kelly succeeded in rearing an adult from
a pupa collected among the roots of corn. This adult emerged on
July 19. Mr. T. H. Parks, at that time with this office, found the
beetles very numerous on young corn at Winfield, Ivans., and Okla-
homa City, Okla., in
June, 1910, and Mr.
E. A. Vickery, also of
this office, found the
beetles very numerous
on corn at Browns-
ville, Tex., in June.
Mr. Pergande records^
the injury to these bee-
tles to cotton at We-
tumpka, Ala., and Dr.
J. B. Smith found the

Fiii. (). — The southern coiu wircworm (Monociepidius larVSe injuring beanS
re.pert»r«.-) . « Ski., view of larv^ ^^ jy^ q^^^^^^ ^^ j_2

larva; c, adult beetle; tl, pupa. All enlarged. (After

cinttenden.) Mr. W. R. McConnell,

of this office, found the
larva^ of these beetles very numerous in alfalfa fields at Carlsbad,
N. Mex.

Owing to the superficial resemblance of the larva of Drasterius
to those of Cryptohypnus, the notes in the files of the Bureau of
Entomology relative to these two genera are very unreliable. Web-
ster records" Drasterius elegans Fab. as a serious pest to corn and
wheat in Indiana, and Forbes records finding larvse attacking corn
in Illinois.

Prdsferhis elegans is found throughout the northern half of
the United States. Drasterius amabiUs Lee. is common in the
Middle Atlantic States and has also been collected in New England
and the Mississippi Valley. All of the beetles in this genus are

lU. S. Dept. Agr., Div. Ent., Notes, v. 11, No. 8668, July 11, 1899.

- Smith, J. B. Annual Report of the New Jersey State Museum. Including a Report of
the Insects of New Jersey, p. 2S5. Trenton. 1009.

^ Webster, F. M. Report of observations upon insects affecting grains. In U. S. Dept.
Agr., Div. Ent., I'.ul. mid Ser. ) 22, p. 52, 1890.

WIREWOEMS ATTACKING CEREAL AND FORAGE CROPS. 23

small, about one-fourth of an inch in length. They are yelloAv or
reddish yellow in color, with more or less black marking. The wire-
worms are about one-half of an inch long when full grown. They
are depressed forms with two prongs on the ninth abdominal seg-
ment and are yellowish colored, except the head and first joint, which
are brownish.

In the general bureau note files, as well as those of the branch of
Cereal and Forage Insect Investigations, are many notes referring
to Drasterius eJegans as predaceous, and also many other notes
referring to this species as a pest to crops. None of these notes is
at all conclusive, however, and in many cases it is very probable
that the form attacking corn and wheat is really the abbreviated
wireworm {C ry ptohy pnus abhreviatus (Say) ) , and it may be that the
predaceous form is DrasteriuH amahilis^ which the writer finds in
many collections under the name D. elegans.

Mr. Theodore Pergande. of this bureau, received several larvse of
Drasterius amahiUs from Manhattan, Kans.. on May 3, 1877.^ He
says that these larva> were found preying on the eggs of Melanoplus
spretus. On June 20 some of them were killed and eaten by mites, so
that nothing but the shell was left. June 25 the other larvae were
completely covered with small mites, so that they could scarcely
move, and he believed that probably they would die, also.

These mites to which Mr. Pergande refers were evidently the
hypopial stage of some tyroglyphid. In all probability the Drasterius
larva^ ate one another, as this is a common occurrence when these
larvae are placed together in a rearing cage. He goes on to say :

May 31, 1878. another larva of this species about half grown was placed with
an Epicanta lurv.-i. It has eaten the Epicauta larva. June IS pui)iited. July
9 issued.

This note gives a considerably longer pupal period than that ob-
served by the writer at Hagerstown. In another note under the same
number there is a record of the finding of a larva of this species with-
in a potato stalk which was infested with Trichoharis trlnotata Say,
and it was probably feeding on these larvae.

The writer found a very young Drasterius amahilis larva eating a
pupa of Meromyza americana Fitch on July 9, 1912, at Hagerstown,
Md. Mr. George Dimmock says that " this species {D. amahilis)
devours locust eggs." -

Drasterins amahilis is very common in w^estern Maryland, where
the adults can be found under stones or rubbish from the middle
of September until early in the spring.

1 U. S. Dept. Agr., Div. Ent., Mem. XII, Note 762P, May 3~.Iuno •2T^. 1S77.

2 Standard Natural Hi.story, edited by J. S. Kingsloy, v. 2, p. :;g1. r.i.st.ni, l.s,s4.
" * * * a few of those larva' are carnivorous, the larviE of Drasterius <iiii<ihilis, in tlie
United States, being known to devour locusts' eggs."

24 BULLETIN 156, U. S. DEPARTMENT OF AGKICULTUEE.

A larva was collected at the roots of a corn plant, which, however,
it did not seem to be damaging, at Hagerstown, Md., in June. This
larva pupated on July G, and the adult emerged July 15. The
beetle remained alive without feeding until September 12 of that
year. On April 30 a large number of beetles were placed in a small
root cage in which corn had been planted. On May G all the adults
were removed. On July 31 the cage Avas examined and three full-
grown larva^ and one pupa were found. This cage was again examined
September 8, and two adults, which, judging from the color and
hardness of the integument, were at least a week old, were found.

Pupae collected in the field emerged July 28, and two larvae col-
lected July 8 pupated August 10, and one of the beetles emerged
August 21, the other August 23,

From the foregoing data it is evident that the life cycle is com-
pleted within one season, a very exceptional condition in this group of
beetles. The beetles leave their hibernating quarters in early spring
and deposit their eggs early in May. The wireworms feed during
May and June, and sometimes even throughout July. They start to
pupate in early July, continuing pupation throughout July and
early August. The pupal stage lasts from 8 to 13 days. The adults
emerge from the ground in late summer and in the fall seek hiber-
nating quartei-s under stones, boards, and rubbish.

Forbes records^ a species of wireAvorm {Asaphes decoloratus
(Say) ) as attacking clover in Illinois. This species is also recorded^
as a pest in XeAv York State.

Mr. Kelly is now investigating an outbreak of a wireworm {Lacon
rectangularis (Say) ) in Kansas. This species has not heretofore been
recorded as a wheat pest, but in a recent letter to the writer Mr.
Kelly says:

In one wheat field at Argonis, Kans., in the spring of 1912, as many as 27
per cent of the phints had been boretl into and ruined in some spots, with an
average of about IS per cent for the field. Later, however, the damage was
miich greater, and it was a question whether the grain was worth cutting.

The collared wireAvorm {Cebrio hicolor Fab., fig. 7) has not as yet
been recorded as an actual pest to any crops, but as several notes
wherein this species has been recorded as feeding on cultivated plants
have come to the notice of the writer, and as one of these plants is a
cereal, we believe it pertinent to make a short note of this species, that
it may be readily recognized should it ever become a serious pest.

The beetles of this species are not now considered as belonging to
the same family as the true wireworms, but they are so intimately

1 Forbes, S. A. Insect Injuries to the Seed and Root of Indian Corn. 111. Apr. Exp.
Sta.. Bui. 44, p. 226, May, 1S90.

" ("omstoclj, J. H., and Slingerland, M. V. Wireworms. N. Y. Coi-nell Agr. Exp. Sta.,
Bui. 33, p. 258-262, Nov., 1891.

WIREWORMS ATTACKING CEREAL AND FORAGE CROPS.

25

related to these insects and the hirvse are so very wireworm-like
that they can be treated, from an economic standpoint, as wireworms.
The beetle is about three-fourths of an inch long, rather slender, with
very prominent scythe-like jaws; the color is broAvn. The wireworm
is cylindrical. The first joint of the body is very large and extends
forward under the head, so that the head is partly inserted within it;
the last joint is long and thimble-shaped. The wireworm when full
grown measures 1^ inches in length and is nearly an eighth of an inch
thick. The color is reddish brown.

The genus is recorded by Sehiodte ^ as living in moist earth in
Europe. In the bureau files is a note - by C. V. Riley which records
the finding of a pupa at
the roots of a grapevine in
July, 1874. No locality ac-
companies the note, which
is with other notes made at
St. Louis, Mo. On July 11
an adult emerged. In the
same files another note^
records this wdreworm as
injuring peach and other
deciduous tree roots near
Fairmont, Cal. In April,
1911, Mr. G. G. Ainslic
sent a larva of this species
to the writer, stating that
he found it feeding on oat
plants near Jackson, Miss.
He sent two other larva? of
this insect to the writer
from Orlando, Fla., where
they were found in black,
sandy soil.

Another interesting record of a wireworm {Ludius Jiepaticus
Germ.) of decidedly minor importance is found in the bureau files.*
Four larva? of this species were found attacking cruciferous plants
at Georgiana, Fla. Our only other record of this genus is one in
which adults were actually reared from larvae of Ludius attenuatus
(Say) found in rotten Avood; these larva? were predaceous.

NATURAL ENEMIES.

Probably the most important factor in keej)ing wireworms in
check are the birds. The following list of birds known, by examina-

1 Sehiodte, J. C. De metamoiphosi eleiitheratorum observationes, pt. 5, p. 530, 1871.
2U. S. Dept. Agr., Div. Ent, Mem. VII, No. 350X, July 11, 1874.
^ U. S. Dept. Agr., Div. Ent., Notes, v. 5, No. 3681, June 24, 1885.
* U. S. Dept. Agr., Div. Ent., Notes, v. 4, No. 3570, Feb. 23, 1882.

Fi<;. 7. — The collared wireworm {Cebrio hicolor)
a, Ijarva ; b, beetle. Enlarged. (Original.

26

BULLETIN 156, U. S. DEPAETMENT OF AGRICULTUEE.

tion of the crops and stomachs, to feed on Elaterida^, either as larvae
or as adult beetles, is compiled from the records of the Biological
Survey of the United States Department of Agricidture:

flycatcher (Muscivora

Franklin gull (Larus franklini).
Herring gull (L. argcntatus).
American black tern {Hydrochelidon

n. surinai)icnsis).
Wilson snipe {GaUbntyo (lelicota).
Woodcock (riiilolichi minor).
Upland plover ( Bart rain ia longicauda).
Killdeer (Oxprchii.s roclfcrux).
Bobwliite ( Colin its virgin id n h.s- ) .
California quail {Lopliortyx calif or-

nica ) .
Ruffed grouse {Bonasa umhcllus).
Mourning dove {Zenaidura tnacroiira

caroUnensis).
Ked-shouUlered liavs'k iButcolincatus).
Red-tailed hawk {ButCo horralix).
Broad-winged hawk (Biitai platiiytc-

rus).

Yellow-billed cuckoo {Coccyzus aineri-

caniis).
Black-billed cuckoo {Coccyzus ery-

throyhthalmuii).
Red-cockaded woodpecker (Dryohates

borealis).
Downy woodpecker (Dryohates puhes-

cens ) .
Hairy woodpecker {Dryohates vil-

losus).
Arctic three-toed woodi>ecker (Picoi-

des arcticus).
Yellow-bellied sapsucker (Sphyrapicus

uarius).
Pileated woodpecker (Plilootoinu/i

pileatus).
Red-headed woodpecker {Melanerpcs

erytli rocephalus ) .
Red -bellied woodpecker (Cent urns

caroliniis).
P'licker (Colaptes an rat us luteus).
Whippoorwill {Antrostomiis vocife-

rus ) .
Nighthawk ( Cliordeilcs Virginian us).
Texan nighthawk (Chordeiles a. tex-

cnsis ) .
Ash -throated flycatcher {Myiurchus

cinerasccns ) .
Crested flycatcher {Myiarchus crini-

tas).

Scissor- tailed

forficata).
Kingbird (Tyranniis tyrunnus).
Arkansas kingbird (Tyrannus vertir

calis).
Cassin's kingbird (Tyrannus vocife-

rans).
Phoebe {^ayornis pltochc).
Black phoebe (Sayoriiis nigricans).
Say's phoebe (Sayornis saya).
Wood pewee (Myiochancs vircns).
Western wood pewee (Myiochanes

richardsonii) .
Olive-sided flycatcher (Nuttallornis

horcalis).
Western flycatcher {Einpidonax diffi-

cilis. )
Least flycatcher (Eni.pldonax mini-

m us ) .
Traill's flycatcher (Empidonax trailU).
Yellow-bellied flycatcher (Empidonax

flavivcntris).
Acadian flycatcher (Empidonax rires-

ccns ) .
Horned lark (Otocoris alpcstris).
Blue jay (Cyanocitta cristata).
Steller's jay (Cyanocitta stclleri).
California jay i Aplnlocoma cati-

fornica).
Crow (Cori'US hraclnirhynchos) .
Bobolink (Doliclionyx oryzirorus).
Cowbird (Molotlirus atcr).
Yellow - headed blackoird (Xanthoce-

phalus xantltoccphalus ) .
Bicolored red-wing (Agclaiiis gnhcrna-

tor calif orniciis).
Red-winged blackbird. (Agelaius phcc-

niccus).
Meadowlark (HturncUa magna).
Baltimore oriole (Icterus galhula).
Bullock's oriole (Icterus hullucki).
Orchard oriole (Icterus spurius).
Rusty blackbird (Euphagus carolinus).
Brewer's blackbird (Euphagus cyano-

cephalus) .
Pvirple grackle (Quiscalus q. quis-

cula).
(Jreat-tailed grackle (Mcgaquiscalus

major).

W IKEWORMS ATTACKING CEREAL AND FORAGE CROPS.

27

Field sparrow (SpizcUa punilla).
Cbippins^ sp;irro\v (^inzclhi passcritui).
Junco (J unco liyemalis).
Lincoln's sparrow (Mclospha lincolni).
Song sparrow (Melospiza mcloclia).
Fox sparrow {PassercUa iliaca).
Cbewink ( Pipilo crythrophthaJmuii ) .
California towbee { Pipilo f. crisi^aliN).
Spurred towhee (Pipilo in. niontanns).
Cardinal (CardinaJi-s eanJinalis).
Rose - breasted jirosbeak (Zamchxlid

liidoviclana).
Black - beaded grosbeak {Zamclodia

melanoccphala) .
Blue grosbeak {Guiraca ca'rulca).
Indigo bunting (Passcrina cyanca).
Lazuli bunting {Passcrina amccna).
I'ainted bunting (Passcrina ciris).
D i ckci ssel ( »*?/) isa, americana ) .

Englisb sparrow (Passer domcsticiis).
Vesper sparrow (Powcctcs gramincus) .
Ilenslow's sparrow (Passerhcrhiilus

liensloici).
Sbarp-tailed sparrow (PasserJicrhuIus

caiidacutiis) .
Sandwich spari'ow (Passcrculus sand-

loichcnsis ) .
Ipswicb sparrow (Passcrculus prin-

ceps ) .
Grasshopper sparrow (Amniodranius

s. australis).
Lark sparrow (Chondcstcs gramma-

cus ) .
Wbite-throated sparrow (Zonotrichia

albicoUis).
White-crowned sparrow (Zonotrichia

Iciicoplirys).

In the desert regions of the Northwest a small lizard {Ph7'ynosoma
doncjlasil douglasii, fig. 8), locally called the "sand toad," eats the
adult Elateridse in large numbers. A pair of these small lizards
kept in the insectary Avould eat ('orymhltes infatus beetles as fast
as these coidd be fed to them. That this is a large part of their
natural food is evidenced b}^ the contents of the stomachs of three of
these lizards collected at Govan, Wash., on April 24, 1910. In the
stomach of lizard Xo. 1, GO per cent of the food was ants, 8 per cent
click-beetles, and 30 per cent other beetles; in lizard No. 2, 90 pei-
cent was click-beetles and 10 per cent ants; and in lizard No. 3, 75 per
cent ants, 15 per cent click-beetles, and 10 per cent other beetles.
Several other kinds of these lizards inhabit the more southern desert
lands of the West and are usually called " horned toads " in these
sections.

In rearing cages wireworms are often infested with small mites
(Tyrogl^q^hidae). The writer received a shipment of Melanotus
iarva^ from Inman, Nebr., in April, 1912. This material when re-
ceived was apparently free from any vermin. When examined again,
on June 17 of that year, some of the larvae were found to be badly
infested with these mites in the hypopial stage. The mites were so
close together on the last two segments of the Avireworms' bodies that
they gave the impression of an incrustation. On June 24 all the
\\ ireworms were infested Avith these mites. Mr. Pergande also found
tliese mites on larvte of Melanotus communis in his cages at Wash-
ington, D. C, in March, 1900.^ Mr. Banks is of the opinion that
these mites are not attacking the wireworms, but merely make use of
insects as a ready means of dispersal. He is evidently correct in

1 U. S. Dept. Agr., Div. Ent., Notes, v. 4, No. 2SS4, Oct. 9, 1882.

28

BULLETIN 156, U. S. DEPARTMENT OF AGRICULTURE.

this opinion, as the larvie in question from Inman, Nebr., are alive

at the present writing (October, 1914).

A gamasid Avas found attached to the body of an adult of Alaus

oculatus at St. Louis, Mo., by Mr. E. E. Fisher. This mite was

under the wing covers.' Another mite {Chelifer alaus) is recorded -

as a parasite of the adult Alaus oculatus.

The writer has published ^ a record of a fly {There oa egressa Coq.)

the larva of which actually attacks and feeds upon wirew^orms. The

larva was found in a wheat field
near Pullman, Wash., and when
found had its head and first
four anterior joints within the
body of a wireworm and was
eating out the insides. This
larva was brought into the
insectary and fed upon wire-
w^orms, of which it ate usually
two a day. On June 10 it
pupated, and on June 21- the
adult fly emerged. Two other
species of Therevidse {Psilo-
cephala aldrichii Coq. and P.
munda Coq.) were reared by
the writer from larvae taken
in the field, associated with
wireworms, in the Pacific
Northwest. These flies in
their larval stages are prob-
ably predaceous on elaterid
larvae. Forbes mentions*
rearing a parasitic fly from an
elaterid larva. A Procto-
trupes has been reared from
an elaterid larva in England
In the same work Curtis refers to a similar record bv

Fig. 8. — A horned toad {Phri/nosonta dou(jla>sii
douglasii), an enemy of the western wire-
worms. (Original.)

by Curtis.^
Bierkander,

1 U. S. Dcpt. Agr., Div. Ent., Note 165R, July 21, 1880.

- Leidy, J. Remarks on the .seventeen-year locust, the Hessian fly, and a Chelifer. In
Proc. Acad. Nat. Sci. Phila. [v. 29], 1877, p. 260-261, .Tune 19, 1877.

8 Ilyslop, J. A. Therera egressa. In Proc. Ent. Soc. Wash., v. 12, No. 2, p. 98, June
15, 1910.

* Forbes, S. A. Insects Insects to the Seed and Koot of Indian Corn. Univ. of 111.
Agr. Exp. Sta., Bui. 44, p. 228, May, 1896.

^ Curtis. John. Farm Insects, p. 181. London, 1860.

WIEEWORMS ATTACKIN(4 CEREAL AND FORAGE CROPS. 29

Bierkaiider obtained through a con-espondent a Filaria from a
wireworm/ The author found a skin of a Mehinotus hirva firmly
attached to the pupa case of a hymenopteron from which the parasite
had emerged. The case was very simihir to that of Typhia sp.

Several records have been made of elaterid larvae being attacked
by fungous diseases. An interesting note is made by Girard - in
which he records Cordyceps attacking wireworms in Trinidad. A
note in the files of this office ^ records a larva of Agriotes sp. received
from Halifax, Nova Scotia, and placed in a rearing cage in the in-
soctary at Washington, as being found later dead and filled with the
mycelium of a fungus which Dr. Flora W. Patterson, of the Bureau
of Plant Industry, determined as Penicillium anlsoplim Viull. This
fungus is known as a parasitic disease of other insects and without
doubt killed the larva in question. Comstock records* larva? in his
rearing cages being killed by M etarrhizium anisoplim.

The writer found a larva of Corymbites infatus in a rearing
cage at the laboratory in Pullman, Wash., which had evidently been
killed by a parasitic fungus. It was filled with white mycelium, which
distended the body and even grew out between the segments. The
specimen was sent in to Washington, but was received in too poor
condition for determination.

Early in June, 1913, a large amount of the culture of the white-
grub fungus {M etarrhiz'min anisoplioi) was sent to the writer by
Mr. J. J. Davis. This material Avas introduced into a field at Nisbet.
Pa. On revisiting the inoculated field on July 14 of that year, a
larva of Melanotus was found dead and completely covered with a
green fungus. This specimen was sent to Mr. Davis, who tentativelv
determined the fungus as M. anlsopllw. From this culture material
the insectary room at the Hagerstown Laboratory became infected,
and during the past summer, despite all precautions, at least one-
half of the Elateridsp in our rearing cages were killed by this disease,

REMEDIAL MEASURES.

Remedial measures haAe been given with each of the more impor-
tant wireworms ti'eated in this paper. Here we wish to report on a
number of measures that have been suggested fi'om time to time as
efficient in combating these insects. We have actually tried most
of these measures, and to prevent repetition of these moi-e or less
costly experiments we publish here the results.

^Gardner's Chronicle, London [v. 3], p. 4o.", .June 24, 184.1.

-Girard, A. Uue nouvelle csp&ce d'Entomophyte. Cordi/ceps hunti, n. si>. (("'ham-
pignon), parasite d'une larve d'Elateride. In Ann. Soc. Ent. Prance, Rtil. des seances,

1895, p. CLXXXI-CLXXXII.

2 U. S. Dept. Agr.. Bur. Ent.. Webster Note No. 4751.

^ Comstock, J. H., and Slingerland, M. V. Wireworms. N. Y. Cornell T'niv. .\iii-. Exp.
Sta., Bui. .33, p. 211, November, 1891.

30 BULLETIN 156, U. S. DEPARTMENT OF AGEICULTURE.

Remedial measures may be classified under three headings: (1)
Seed treatment to prevent insects eating the seed; (2) introduction
of poisonous or noxious substances into the soil; and (3) cultural
methods.

TREATMENT OF SEED.

Under the first head many substances have been used and reported
as more or less efficient, among which might be mentioned Paris
green and coal tar, gas tar, coal oil, tar, Paris green, and arsenate of
lead. In 1884 Webster used kerosene as a treatment of seed corn to
protect seed from wireworms. Although his experiment did not
apparently impair the vitality of the seed, a farmer who attempted
to appl}' the recommendation claimed that the vitality of the seed
was destroyed thereby. In 1888 Forbes treated corn seed with Paris
green, and though wireworms fed on corn so thoroughly coated as to
be quite green they seemed to experience no ill effects. He also ex-
perimented with alcoholic solutions of arsenic and water solutions
of strychnine and potassium cyanid.

In the spring of 1911 wireworms were very numerous on the wheat
land at Wilbur, Wash., and the writer carried on a series of very
extensive experiments to determine the value of some of these sub-
stances and also added a few which, to his knowledge, had not been
tried before.

Three sacks of wheat (6 bushels) were treated on March 24 with
arsenate of lead. Six pounds of insecticide were used for the batch.
The arsenate was thinned to the consistency of thick whitewash,
with Avater, and thoroughly mixed into the seed in a large box.
The seed, when dry, was very white and Avell coated. On the same
date two sacks (4 bushels) Avere treated with coal tar. The tar was
applied Avith a paddle, the paddle being first dii)ped into the tar and
then stirred around in the wheat until the seed was well coated.
The seed was then mixed with sand and allowed to dry. One sack
of wheat Avas treated Avith strychnine, 2 ounces of this poison being
used to 2 bushels of Avheat. The strychnine Avas dissolved in 2 quarts
of hot water and 1 pound of sugar Avas added as an adhesive. The
seed was then soaked in this liquid and alloAved to dry. On March

31 all of these treated batches of seed Avere soAvn. The soAvings
were made in plats Avhich were about half a mile long. They Avere
made in an 11-foot Avheat seeder, and were arranged as follows:

2 seeder widths of seed treated with strychnine.
2 seeder widths without treatment, as a check.

2 seeder widths of seed treated with coal tar.

4 seeder widths checlv.

5 seeder widths of seed treated with lead arsenate.
f) seeder widths olieck.

3 seeder widths of seed treated witli coal tar.
9 seeder widths check.

4 seeder widths of seed treated with arstMiate of lead.

WIEE WORMS ATTACKING CEEEAL AND FORAGE CROPS.

31

These plats were carefully staked and examined from time to time,
but at no time could any appreciable difference be noted as to their
appearance. Wireworms were as numerous in all the treated plats
as in the checks. Wheat was very generally attacked and no dead
wireworms were found.

A number of wireworms were confined in a large tin cage with
wheat treated with strychnine as their only food. After two months
these larvae were still alive and apparently unaffected by the poison,
though they ate the poisoned grain.

While these experiments were going on at Wilbur a more intensive
series was being carried on at Spokane. Here, instead of wheat,
sweet corn was used. These experiments were carried on in a field
recently cleared of timber. The soil was quite heavy and very
moist. Wireworms were very numerous and apparently quite gen-
erally distributed.

On April 5, seed corn was treated in the following manner:

Lot 1. Coal tar was applied vevy heavily and Paris green dusted onto it
until it was quite green.

Lot 2 was treated by soaking for a few minutes in copper sulphate and then
drying rapidly in the sun. Several potatoes also were soaked, cut into small
pieces, in a saturated solution of strychnine.

This field was all in corn in 1909 and was badly infested with
wireworms. In 1910 it was half in wheat on fall plowing and half
in potatoes on spring plowing, and was also badly infested this year
with wireworms. A plat of each treatment with a check row be-
tween each plat was planted on each half of the field. Seventy hills
of corn were in each plat. All the plantings were made on April
24. The coal-tar treatment prevented about 90 per cent of the seed
so treated from germinating, so this precludes the use, at least as
applied to this experiment, of this seed treatment. On May 2 the
hills were dug out and the wireworms in each hill counted. Wher-
ever wireworms were present they Avere attacking the seed. The
results of this count appear in Table I :

Table I. — Results of exprrinicnts (u/aUist icireirornis iritJi treated seed.

Row.

Treatment.

Number

of hills

examined.

Number of

wireworms

found.

Number of

wireworms

per hill

''average).

Total aver-
age number

of wire-
worms per
hill for each
treatment.

1

Copper sulphate

10
24
24
24
3
24
24
13
24

40
138

4

5.75

11

. .do

4 87

5

Coal tar and Paris green

do

2

Check ...

4

.. .do

35
40
22
93

1.458
1.667
1.692
3.875

6

do

8

do

do

10

1.758

32 BULLETIN 156, U. S. DEPARTMENT OF AGRICULTURE.

From the last experiment we conclude that the use of coal tar and
Paris green is not a remedial measure to be recommended. However^
Dr. H. T. Fernald has published ^ an account of a series of experi-
ments that seem to reach quite the opposite conclusion, and it is
very probable that gas tar will not prevent germination as did the
coal tar of our experiments.

The copper-sulphate plat was more severely infested than the
check plats, so this treatment is quite useless as an insecticide for
wireworms. The potato bait poisoned with strychnine was a fail-
ure because the potatoes were allowed to dry up before being placed
in the ground.

Mr. G. I. Reeves carried on an experiment at Pullman, Wash.,
using a commercial tobacco extract applied to the seed corn as a re-
pellent. This experiment was carried on in a root cage. On May 27,
1909, he treated 15 kernels of seed corn by soaking for 24 hours in a
solution of commercial tobacco extract. 1 part to 16 parts of water.
The seed was dried before planting and was sown with alternate
untreated seeds as a check. Wireworms were introduced at the time
of seeding and also on June 2. The experiment w^as discontinued
on June 10, and all the seed carefully examined. Of the treated
seeds, eight were eaten into by wirew^orms, wdiile nine of the un-
treated seeds were destroyed. It is very evident from this experi-
ment that tobacco solution as a repellent is quite useless, at least for
wareworms.

Soaking the seed in formalin has been suggested as a means of
repelling w^irew^orms. This measure is quite useless. In the re-
gions of the Pacific Northwest where the author was studying
severe wireworm outbreaks nearly all the seed w'heat had been
treated with formalin as a means of preventing the development
of smut fungus.

Mr. O. A. Johannsen and Miss Edith M. Patch have published -
the results of a series of experiments carried on in Maine. They
treated seed corn Avith tar and Paris green, and with arsenate of lead,
and found both of these treatments inefficient.

SOIL TREATMENT.

The second group of remedial measures — soil treatment — has re-
ceived considerable attention. Experiments with soil fumigants are
now being carried on by the writer, but as the methods have not as yet
been placed on a practical basis this matter will not be treated herein.

1 Fernald, H. T. A new treatment for winworms. In Jour. Econ. Ent., v. 2, Xo. 4.
p. 279-280. August, 1000.

2 Johannsen, O. A., and Tatch, Edith M. Insect Notes for 1911. Maine Agr. Exp. Sta.,
BuL 195, p. 229-248, December, 1911.

WIREWORMS ATTACKING CEREAL AND FORAGE CROPS. 33

Webster carried on experiments at Cedarville, Ohio, in 1894
to determine the effectiveness of kainit as an insecticide. The fer-
tilizer was applied at the rate of 500 pounds to the acre without
any effect whatever. He also carried on a series of experiments at
La Fayette, Ind., in 1889, to test the efficiency of an often-recom-
mended substance — table salt. Pots were used in these experiments,
and table salt applied to the surface and washed in with water.
Three dosages were used at the rate of about 500 pounds, 1,000
pounds, and 25,000 pounds per acre, respectively, and in no case were
wireworms killed by the application.

The Maine experiment station has tried a patented preparation
composed largely of slaked lime, a "" soil fungicide," and tobacco
dust, applied to the hills in cornfields infested with wii-eworms, and
has found all of these treatments quite useless. Experiments ' with
chlorid of lime, gas lime, chlorate of potash, bisulphid of carbon,
crude petroleum, kerosene, and emulsions of crude petroleum and
kerosene, applied to the soil, have demonstrated that none of these
substances is of practical value in destroying wireworms. However,
the use of petroleum products as soil sterilizers is suggestive, and will
be further investigated.

Mr. J. J. Davis - has found that a soil f umigant highly recom-
mended by some English entomologists is quite useless in combating
Limonius confusus.

CULTURAL METHODS.

The third group of remedial measures — cultural methods — is the
only one which so far has been actually proved to be of practical
value.

Flooding land where irrigation is practiced would be of little
avail unless long continued, as we have records of severe outbreaks
of wirew^orms on land in Indiana that is annually overflowed by
the rivers. Fall plowing is of but little use in combating these
insects. The cornfields so severely attacked by the wdieat wire-
worm at Bridgeport last year had been plowed in the spring. The
garden patch, however, was fall plowed, and potatoes on this patch
were absolutely destroyed by wireworms. Another piece of fall-
plowed land on another part of the farm planted to corn was
practically free from worms, which illustrates how easily faulty
conclusions can be arrived at, w4tli insufficient data. Mr. O. A.
Johannsen and Miss Edith Patch record observations made at Mon-
mouth, Me., in 1911, wherein a field was plowed after the ground

1 Comstock, J. H., and Slingerland, M. V. Wireworms. N. Y. Cornell Univ. -Vgr. Exp.
Sta.. Bui. .'?.'?, November, 1891.

- Davis, J. J. Insect notes from Illinois for 1901». In Jour. Econ. lOnt, v. 3, No. 2,
p. 182, April, 1910.

34 BULLETIN 156, U. S. DEPARTMENT OF AGRICULTURE.

had been stiffened b}^ frost in the fall, and which was so badly in-
fested the following spring that the crops Avere absolutelj^ destroyed.
The fatality to the beetles caused by the destruction of the pupal
cell in the fall has been apparently somewhat overdrawn. In our
cages at the field station at Hagerstown, Md., we had, in March, 1914,
many adults of Agriotes mancus alive in cages wherein they were
subjected to outdoor weather conditions. These adults were removed
from their pupal cells during September, 1913.

Two other remedial measures have been suggested from time to
time, the first of which is trapping the larvse in potato and other
vegetable baits and hand killing; the second is killing the adults
with poisoned bait of several kinds — clover, sweetened liquids, bran
mash, potatoes and other vegetables, and rape cake. Miss Ormerod
found a true rape-seed cake quite useless, but reports ^ " Kurrachee
cake," made from mustard seed, as killing the larva? Avhich fed
upon it. These methods have been found very inefficient, and even
were they successful in killing the insects they would be impractical
so far as the extensive cereal and forage crops are concerned.

1 Proc. Ent. Soc. London, 1882, p. xix.

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BULLETIN OF THE

I)

No. 160

Contribution from the Bureau of Entomology, L. O. Howard, Chief
January 22, 1915.

(PROFESSIONAL PAPER.)

CACTUS SOLUTION AS AN ADHESIVE IN ARSENICAL
SPRAYS FOR INSECTS.^

By M. M. High,
Entomological Assistant, Truck Crop and Stored Product Insect Investigations.

INTRODUCTION.

In the application of arsenical sprays against insects with biting
mouth parts the object in view is, of course, to protect the plant or
plants from insect ravages by poisoning the foliage, so that the insects
will, in feeding, take into their system enough of the poison to pro-
duce death. Some arsenicals, because they possess a higher percentage
of free arsenic, act more quickly in this direction than others, but
these are, as a rule, injurious to most plant foliage,' unless mixed Avith
some agent that will counteract the free arsenic and produce a more
uniform distribution on the plants sprayed. Arsenicals containing
a high percentage of arsenious oxid generally possess only slight ad-
hesive powers and after a heavy dew or light rain are washed from
the foliage.

Certain crops demand very prompt protection from the ravages
of biting insects; otherwise severe losses are almost certain to be
incurred, and to insure the preservation of the crop concerned it is
highly important that a poison with some lasting qualities, as well
as one quick in action, be applied. Thus it follows that an arsenical
must adhere to the foliage if the most favorable results are to be
realized.

In 1913 and 1914 some experiments were conducted for the
purpose of discoA^ering a good adhesive which could be obtained
easily and at little expense to the grower. This adhesive has been
found in a cactus that flourishes in the Southwest. The variety
which was most extensively used in the following experiments, and

' This bulletin describes the use of cactus solution as an adhesive in the application of
arsenical sprays against the belted cucumber beetle. It is applicable to regions where
prickly pear is easily obtainable and for the treatment of insects of related habits, such
as the striped and twelve-spotted cucumber beetles, etc.
65966° — Bull. 160 — 15 1

2 BULLETIN 160, U. S. DEPARTMENT OF AGRICULTURE.

one of the most abundant of the many species to be found in the
lower Rio Grande Valle}^, is Opuntla Undheimeri Engehn., com-
monly known as the "prickly pear." This plant produces a fruit
that is available about one month in each year and one of which
the natives are especially fond. Further, the plants themselves
furnish food to many domestic animals and, it is claimed, prevent
many cattle from dying during severe droughts because of their
highly watery composition. Many ranchmen protect their cacti
during a wet season and save them against the time of drought. A
gasoline torch, manufactured especially for the purpose, is used to
burn off the spines, and as soon as this burner is put into operation
cattle, recognizing the peculiar noise, come at once to obtain the
food thus rendered available.

The prickly pear, besides being high in fluid content, is very
mucilaginous and is invariably used by Mexicans in the manufac-
ture of whitewash, to promote adhesiveness. The cactus is sliced the
evening previous to the application and placed in the water or in
the lime mixture, where it remains for several hours. The white-
wash is then ready for use. The utilization of cactus in whitewash
thus suggested to the writer its availability as a factor in promoting
adhesion in poisonous sprays.

EXPERIMENTAL WORK WITH CACTUS.

EXPERIMENTS WITH ZINC ARSENITE.

On March 23, 1913, 20 pounds of cactus were sliced lengthwise and
immersed overnight in 50 gallons of water. The next morning 2
j)Ounds of zinc arsenite in paste form were added, and after a thor-
ough mixing spraying was commenced on sugar beets which were
being injured by the belted cucumber beetle {Diahrotica halteata
Lec.).i

A previous experiment demonstrated that cactus yields a higher
percentage of mucilaginous matter if sliced at right angles to the
spines, and, moreover, the time required for preparation is materially
shortened by this method. It is best, however, to cut the larger pads
both ways, since, owing to the cellular structure of the pads, this
method insures a more copious and rapid flow of the juices. The
result obtained from the use of the spray, at the rate of 20 pounds
of prepared cactus to 50 gallons of water, was gratifying; the spray
not only adhered to the foliage better, but spread more uniformly
over the surface of the leaves. The quantity of cactus required to

1 Accounts of this species, by Dr. F. II. Chittenden and Mr. II. O. Marsh, have been pub-
lished in Bulletin No. 82, Part VI, Bureau of Entomology, U. S. Departemnt of Agricul-
ture, pages 69-71 and 76-82, December 8, 1910. These include illustrations of the stages,
notes on life history, lists of food plants, and technical descriptions of the different

CACTUS SOLUTION AS AN ADHESIVE. 3

make 20 pounds is comparatively small. The results of this spray-
ing operation were favorable, as the number of beetles present four
days later did not exceed 30 per cent of the original number, and a
majority of these had just arrived from near-by breeding quarters.

In the next experiment 10 pounds of cactus were used in combina-
tion with 3 pounds of zinc arsenite and 50 gallons of water. As before,
the cactus was sliced and placed in water the evening previous to
spraying, and the following morning the solid particles were- thrown
out before the poison was added. This spraying operation, with
but 10 pounds of cactus, gave good residts, but the spreading (luality
of the material was not as good as in the first experiment, in Avhich
20 pounds of cactus were employed.

In the next experiment, on April 3, 15 pounds of cactus were used
with 3 pounds of zinc arsenite and 50 gallons of water. In this
case the poison appeared to adhere and spread as well as when 20
pounds of the cactus were used. It thus appeared that 15 pounds
of the cactus Avith spines ^ would be about the proper proportion to
use with 50 gallons of water in future work.

The following table shows the mortality of Dlabrotica halteata
placed on an encaged sugar-beet plant spraj^ed with zinc arsenite
at the rate of 3 pounds to 50 gallons of water plus 15 pounds of
prepared cactus:

Table I.

-Experiment No. 10. — Cactus as au adhesive in coinhination ivith
arsenite of zinc, Broivnsville, Tex., 1913.

Date.

Beetles
present.

Living.

Dead.

Feeding.

Not feed-
ing.

Mar. 17

5
5
5
5
5

4
3
3
1
0

1
2
2
4
5

4
3
3

1
0

1

Mar. 18

2

Mar. 19

2

Mar. 21

4

Mar. 22

5

The beetles were placed on the sprayed plant at 6.30 p. m., March
15, but during several cool days which followed they were quite in-
active and probably fed but little. Cactus was tested in* the insectary
as an adhesive before experiments were conducted in the iield, to
insure the absence of any inopportune chemical reaction that might
injure the plants. This experiment demonstrated that in approxi-
mately six days after spraying 99 per cent of the beetles succumbed
to the poison. Simultaneously with the foregoing experiment another

^ Cactus with spines is preferable to the spineless varieties ; in fact, the spiny variety
appears to be nearly one-third richer in gluten. The Dairy Division of the Bureau of
Animal Industry has been conducting some cactus-feeding experiments for dairy cows the
past two years, and has made several analyses of both the spined and spineless varieties
of cactus.

4 BULLETIN 160, U. S, DEPARTMENT OF AGRICULTURE.

pot experiment was made, discarding cactus and using the same
amount of arsenite of zinc. The following results were obtained :

Table II. — Expcrmient No. 11. — Arsenite of zinc without cactus as an adhesive,

Brownsville, Tex., 1913.

Date.

Beetles
present.

Living.

Dead.

Feeding.

Not feed-
ing.

Mar 17

7
7
7
7
7

6
4
4
3
3

1
3
3

4
4

6
4
2
3
1

1

Mar 18

3

Mar. 19 .

5

Mar 21

4

Mar. 22

6

It will be noticed here that at the end of the sixth day the mor-
tality was much under that of experiment No. 10. The plants in both
experiments were spraj^ed thoroughly, but the latter spray did not
spread as well as the former. In the next experiment cactus was
again used at the rate of 20 pounds to 50 gallons of water. The same
amount of zinc arsenite was used in this experiment, or 3 pounds to
50 gallons of water. Table III shows the number of deaths on
each date.

Table III. — Experiment No. 12. — Cactus as an adhesive in combination with
arsenite of zinc, Brownsville, Tex., 1913.

Date.

Beetles
present .

Living.

Dead.

Feeding.

Not feed-
ing.

Mar. 17

14
14
14
14

8
3
3
0
0

6
11
11
14

6
2
1
0
0

8

Mar. 18

12

Mar. 19

13

Mar. 21

14

Mar. 22

The beetles were placed on the poisoned sugar beet at 6 p. m.,
March 15, and in 36 hours nearly all of them were dead.

EXPERIMENT WITH PARIS GREEN AND LIME.

In the next pot experiment Paris green was used in place of zinc
arsenite and at the rate of one-half pound to 50 gallons of water plus
2 pounds of lime. The plant was sprayed on March 17, and as soon
as the poison was dry on the sugar beet the beetles were liberated
inside the cage. Table IV sums up the results.

Table IV. — Experiment No. 13. — Cactus as an adhesive tvith Paris green and
lime, Brownsville, Tex., 1913.

Date.

Beetles
present.

Living.

Dead.

Feeding.

Not feed-
ing.

Mar. 18

10
10
10
10

10
2
0
0

0
8
10
10

6
2

0
0

4

Mar. 19

8

Mar. 21

10

Mar. 22

10

CACTUS SOLUTION AS AN" ADHESIVE. 5

The cucumber beetle appeared, as will be seen from the foregoing
table, to succumb more readily to the Paris-green spray than to any
one of the former sprays of zinc arsenite. In the field experiments
there was not much difference, though the zinc arsenite gave more
favorable results in that it lasted longer. The dews in the lower Rio
Grande Valley are usually heavy ones, which would naturally reduce
the effectiveness of the Paris-green application. But, as already
shown, in the pot experiment the results appeared much more quickly
than with the other sprays.

UNSATISFACTORY RESULTS WITH LEAD ARSENATE.

Since the experiments with cactus as an adhesive and a spreader
for zinc arsenite and for Paris green and lime had resulted so favor-
ably, not only in increasing the adhesiveness of the spray, but also in
the destruction of the beetle, it was decided to try it in combination
with lead arsenate. The cactus was placed in a barrel of water about
12 hours before the arsenate of lead was added. A few minutes after
adding the lead arsenate the formation of a precipitate was observed.
In an hour's time a cottony scum had formed on the surface and
appeared fairly well distributed throughout the mixture. In the
meantime spraying had been going on, but with little success, as this
semiliquid matter clogged the nozzles. In about two hours' time the
precipitation was more complete and the solution was discarded, since
its consistency rendered it useless for spraying purposes. Alkalinity
of the water was at first suspected, and rain water was substituted,
but with the same results, so that no further attempt was made to use
the cactus with lead arsenate. The lead arsenate employed was air-
dried, having been formerly paste which had dried out in an open
keg ; but no doubt even with fresh arsenate of lead the same precipi-
tation would have taken place, as the air-dried arsenical had been
used successfully without the cactus and had remained in solution,
although it did not adhere well.

In experiment No. 14 (Table V) arsenate of lead was employed at
the rate of 3 pounds to 50 gallons of water. As the potted plant was
quite small, there was not sufficient foliage to support a great number
of beetles, and on April 4, at 6 p. m., six belted cucumber beetles were
placed on the plant.

Table V

-Er per uncut Xo. IJf. — Cactus as an adhesive with arsenate of lead,
Brotvnsville, Tex., 1913.

Date.

Beetles
present.

Li^Tiig.

Dead.

Feeding.

Not feed-
ing.

Apr. 6.
Apr. 7,
Apr. 8.
Apr. 9.
Apr. 11

BULLETIN 160, U. S. DEPARTMENT OF AGRICULTURE.

The time required to kill all of the beetles placed on the sprayed
plant Avas approximately six days, provided all specimens began
feeding immediately after being placed on the poisoned plant.

In the next experiment 2^ pounds of arsenate of lead were used to
50 gallons of water. The host i)lant was spinach that had been grow-
ing in the pot for some time. The spraying was done during the
morning of April 14, and at 4 p. m. on the same date, after the poison
had dried, 10 belted cucumber beetles were placed inside the cage and
on the plant where possible. Table VI shows the mortality :

Table VI. — Experiment No. 15. — Cactus as an adhesive with arsenate of lead,

Brownsville, Tex., 1913.

Date.

Apr. 10
Apr. 17
Apr. 24

Beetles
present.

Living.

Dead.

Not feed-
ing.

The spray here used was not so effective as in experiment No. 14,
the mortality being only 80 per cent at the end of nine days. The
plant died from some cause about the 24th of April, and probably
Aery little feeding Avas done during the last few days the plant lived
after being sprayed.

FURTHER EXPERIMENTS.

The results obtained in the foregoing experiments had been so
favorable that further experiments on a larger scale Avere commenced.
Several thousand pounds of the prickly pear Avere used in the Avork,
and as the regular "pear burner," or torch, was employed to singe
the spines from the pads, they could now be handled with some com-
fort. The work has been conducted in a small way and on a large
scale Avith about the same degree of success. It requires only a short
time to burn the spines from enough cactus to make a sufficient
amount of adhesive material for several thousand gallons of spray
mixture.

The list of insecticides that have been employed in combination
with cactus as an adhesive includes Paris green, lead chromate, zinc
arsenite (in both paste and poAvder forms), lead arsenate, ferrous
arsenate, and iron arsenite. The preceding pages giAe an account
of experiments with zinc arsenite in the paste form, Paris green, and
lead arsenate in the paste form, AAdiile the experiments that follow
Avill include zinc arsenite in the powder form, lead arsenate in paste
form, ferrous arsenate, and iron arsenite, the last two used in the
poAvder. The poAvdered zinc arsenite gave excellent results in every
instance Avhen used in combination Avith cactus Avater, and the mor-
tality Avas in some cases higher than when three times the Aveight in

CACTUS SOLUTION AS AN ADHESIVE. 7

])aste form uas used. Very favorable results were obtained with
ferrous arsenate in most cases, while the results with iron arsenite
were not quite so good. The following tables give results of the
experiments conducted in the insectary with each of the arsenicals
hei'e mentioned.

On March 1, 1914, a cabbage plant was sprayed with ferrous arsen-
ate at the rate of 1 pound to 40 gallons of water, and as soon as the
poison had dried on the leaves, or at 6 o'clock p. m. the same date,
four Diahrotica halteata were encaged on the plant.

Table VII. — Experiment No. 16. — Cactus n-s an adhesive with ferrous arsenate,

Brownsrille, Tex., 101. 'f.

Date.

Beetles
present.

Living.

Dead.

Feeding.

Not feed-
ing.

Mar. 2

0
0
0
0
0
0
0
0
1

1

0
3
3

3,

Mar. 3

Mar. 4

1
1

Mar. 5

Mar. 6

Mar. 7

2 "^

Mar. 8

3
2
1

1

2

Mar. 9

Mar. 10

\

It will be seen from the foregoing table that the mortality was
much too low to pay for applying the poison. It was observed that
the feeding was light for four or five days after confinement. The
solution did not adhere and distribute itself well enough to make a
good spray.

About the same time that spraying was done on experiment No.
16 a second solution was made up, using the same amount of fer-
rous arsenate or 1 pound to 40 gallons of water. Eighty per cent
of the w^ater used was taken from a tank where two days previous
IJ pounds of cactus to the gallon of water had been placed. This
made an exceedingly glutinous solution which caused the liquid to
spread uniformly as well as to adhere. On March 2 seven Diabrotica
halteata Avere placed on the plant.

Table VIII. — Experiment No. 17. — Cactus «s an adhesive with ferrous arsenate,

Brownsville, Tex., IDlJf.

Date.

Beetles
present.

Livini;.

Dead.

Feed ilia;.

Not feed-
ing.

Mar. 3

7
7
7
7
7
7
7
7
7

6
6
6
6
6
6
6
5
5

0

3
6
6
4
5
4
3
1
4

4

Mar. 4

1

Mar. 5

1

Mar. fi

3

Mar. 7

2

Mar. 8

3

Mar. 9

4

Mar. 13

6

Mar. 14

3

8

BULLETIN 160, U. S. DEPARTMENT OF AGRICULTURE.

The death rate in this experiment was very low, which is ac-
counted for to a certain clegree by a decrease in the voracious ap-
petite of the beetles, which were encaged on a cabbage plant. Feed-
ing appeared to be more from the underside of the leaves, and usually
the epidermis was left intact.

In the next experiment with potted plants spinach was substituted
for cabbage, since it seemed preferable to the beetles, particularly as
the cabbage plants had been growing for some time in the pots and
had become more or less stunted and tough. In this experiment fer-
rous arsenate was used at the rate of 1 pound to 40 gallons of water,
in which 40 pounds of cactus had been placed 72 hours previous.
Table IX shows results and mortality. The plant was sprayed April
2, and on April 4 five beetles were liberated on the plant and cov-
ered with a lantern globe.

STABLE IX.-

-Eaiperiment No. 18. — Cactus as an adhesive with ferrous arsenate,
Brownsville, Tex., 1914.

Apr. 4
Apr. 5
Apr. 6
Apr. 7
Apr. 8
Apr. 9

Beetles
present.

Living.

Dead.

Feeding.

Not feed-
ing.

The results here were much better than in experiments Nos. 16 and
17, and the beetles appeared to succumb more readilj^, since they fed
more rapidly.

On April 6 a spray was made up of ferrous arsenate, using 1 pound
to 12 gallons of w-ater in which 10 pounds of sliced cactus had been
placed 48 hours previous to spraying, insuring thorough glutinous
consistency in the spray mixture. Some spinach plants in pots were
sprayed previous to spraying plats in the field. On April 13, or one
week from date of spraying, six beetles were encaged on a plant and
observed for 10 days. Table X shows the number of beetles that
succumbed.

Table X. — Experiment No. 18. — Cactus as an adhesive irith ferrous arsenate,

Broivnsville, Tex., lOlJf.

Beetles
present.

Living.

Dead.

Feeding.

6

6

0

3

6

4

2

4

6

4

2

4

6

4

3

3

6

4

2

1

6

3

3

2

6

3

3

1

6

3

3

0

Not feed-
ing.

Apr. 13.
Apr. 14.
Apr. 15.
Apr. 16.
Apr. 18.
Apr. 20.
Apr. 21 .
Apr. 23.

CACTUS SOLUTION AS AN ADHESIVE. 9

This plant began to wilt and appeal* blighted on April 18, little
feeding being done from that date, even though the poison had been •
on the plant for nearly two weeks. It is thought that a higher mor-
tality would have occurred had the plant remained green and living.

An arsenate of lead spray was made, using the paste form at the
rate of 4 poimds to 60 gallons of water. In this solution no cactus
was used. On April 11 five beetles Avere placed on an encaged cab-
bage plant in the insectary that had been spraj^ed five days before.
Table XI gives the final results.

Table XI. — Experiment No. 20.

-Arsenate of lead without cactus, Bnnanj^rillc,
Tex., 191Ji.

Date.

Apr. 13
Apr. 14
Apr. 16
Apr. 18

Beetles
present.

Living.

Dead.

Feeding.

s

5

0

4

4

3

1

1

4

3

1

1

4

2

2

1

Not feed-
ing.

This spray did not adhere to the cabbage foliage as well as when
cactus was used, and the beetles fed very slowly after the first two
days of confinement. Better results were obtained in the field, as
the beetles began feeding just after spraying, and where a partial
uniform coating was secured the poison was effective. If the poison
could be made to combine or mix with cactus water the results would
undoubtedly be much better.

April 2 a solution was made up of iron arsenite, using 1 pound
to 40 gallons of water. Some difficulty was experienced in bringing
the poison into suspension, as it settled quite rapidly to the bottom
of the barrel. April 4 another solution was prepared, using the
same amount of poison to a given quantity of water, with the pre-
A'ious addition of cactus at the rate of 1^ pounds to each gallon of
water, in which salicylic acid had been used as a preservative to
prevent fermentation of the cactus juice. As a check some potted
cabbage plants were sprayed. On April 11 ten belted cucumber
beetles were encaged on one of the cabbage plants that was sprayed
April 4. Table XII gives the results.

Table XII.-

-Experiment No. 21. — Cactus as an adhesive with iron arsenite,
Brotcnsville, Tex., JOlJf.

Date.

Apr. 13

Apr. 14

Apr. 15

Apr. 16

Apr. 18

65966°— Btill. 160—1

Beetles
present.

Living.

Dead.

Feeding.

Not feed-
ing.

10

BULLETIN too, U. S. DEPARTMENT OF AGRICULTURE.

It is apparent that although the application had been made for
more than a w6ek, a sufficient amount of the arsenical remained to
have some effect on the feeding of the beetles. A later experi-
ment with iron arsenite showed the mortality of the beetles when
they feed on the plant immediately after spraying has been done.

Wliile spraying a plat of sugar beets at the South Texas Gardens
on April 15 the writer also sprayed some plants in the insectary,
using zinc arsenite in the powdered form. The cactus was used at
the rate of 1.8 pounds to the gallon of water and the zinc arsenite
at the rate of 1 pound to 64 gallons. The plants were sprayed on the
morning of the 15th, and on April 16 eleven beetles were liberated
inside the cage surrounding the plants.

Tahi.k XIII.

-Fjxperiincnt No. 22. — Cnctus as an adhesive with zlne arsenite,
BrrncnsriUc. Tex., 19Vi.

Apr. 16
Apr. 17
Apr. 18
Apr. 20
Apr. 21
Apr. 23

Beetles
present.

Living.

Dead.

Feeding.

11

0

8

10

I

9

10

1

9

4

7

4

4

7

3

1

10

0

Not feed-
ing.

This spray adhered and spread exceedingly well, although much
less cactus could have been used with equal results. However, no
precipitation was observed when the cactus was used at this strength.

In experiment No. 23 a potted sugar beet was sprayed April 11
with zinc arsenite (powdered) at the rate of 1 pound to 35 gallons
of water, using three-fourths of a pound of cactus to each gallon of
water, the cactus having been placed in the water four days before.
Fermentation was prevented by the use of copper sulphate. On
April 15 ten belted cucumber beetles were encaged on the plant.

Table XIV.-

-Experiment No. 23. — Vactus as an adhesive with zinc arsenite,
Brownsville, Tex., 1914.

Dale.

Apr. 16
Apr. 17
Apr. 20
Apr. 21
Apr. 23

Beetles
present.

Living.

Dead.

Feeding.

Not feed-
ing.

It will be observed that in this experiment less than half the quan-
tity of cactus was used than was added in experiment No. 22, but
the zinc arsenite was increased to nearly twice the amount used in
the preceding experiment, and there was only a 10 per cent difference

CACTUS SOLUTION AS AN ADHESIVE.

11

in the mortality. The phmts used were both sugar beets. The result
of this exi>eriment shows that by the use of cactus the lasting qualities
of the poison on the plants may be greatly increased.

The spraying in experiment No. 24 was done at the same time as in
experiment No. 22, 1 pound of zinc arsenite being used to 64 gallons
of water but only one-third of a pound of cactus to each gallon, the
glutinous matter having been extracted by soaking the cactus for four
days in water. Salicylic acid was added as a preservative. The
sugar beet was sprayed on April 15, and on April 16 five beetles were
placed on the plant. April 17 one beetle was found dead and four
still feeding. April 18 three had died from the effect of the poison
and two were yet feeding. On April 20 all were dead. During the
foui" days the beetles were encaged they appeared to feed very rap-
idly, as they had been confined for several days without food. This
proves that 1 pound of powdered zinc arsenite with cactus to make it
adhere is more effective than 2 pounds in the paste form and just as
effective as 3 pounds in the paste form.

The plant in experiment No. 25 was sprayed with 1 pound of zinc
arsenite to 35 gallons of water and at the same time as No. 23, on
April 11, with the same quantity of cactus, but the beetles were not
placed on the plant for six days after spraying. On Aj)ril 17 three
beetles were encaged, and by the 22d all were dead.

On April 5, after spraying a field plat of cabbage with ferrous
arsenate, several plants were treated in the insectary. The strength
used was 1 pound to 12 gallons of water. One pound of cactus was
used to each gallon of water, the cactus water having been made 26
days when used. It was prepared on March 16 and sodium benzoate
added as a preservative. On April 11 six beetles were placed on a
cabbage plant covered by a lantern globe. Table XV gives the
number of beetles that succumbed in a given period.

Table XV.

-Experiment No. 26. — Cactus as an adhesive with ferrous arsenate.
Brotcnsville, Tex., JVl^.

Date.

Beetles
present.

Living.

Dead.

Feeding.

6

6

0

4

6

6

0

5

6

6

0

5

6

6

0

1

6

3

3

2

5

1

4

1

5

1

4

1

5

0

5

0

Not feed-
ing.

Apr. 13
Apr. 14
Apr. 15
Apr. 16
Apr. 17
Apr. 18
Apr. 20
Apr. 21

The beetles from some cause fed very sparingly the whole time they
were encaged. Whether the poison was distasteful or the plant had
become tough, could not be ascertained.

12

BULLETIN 160, U. S. DEPARTMENT OF AGEICULTUEE.

On April 4 a small plat of cabbage was sprayed with iron arsenite
at the rate of 1 pound to 40 gallons of water. Two pounds of cactus
were added to each gallon and the decoction was prepared on March
14 and 15. It was preserved with salicylic acid at the rate of ^
joound to 50 gallons. It was quite difficult to bring the arsenite of
iron into suspension. Thorough agitation was required to prevent it
settling to the bottom of the tank. With a hand sprayer it is impos-
sible to secure uniformity in the spray. Table XVI gives results with
10 beetles on one cabbage plant sprayed on April 4, the beetles being
liberated on the plant April 11.

Table XVI. — Experirnent No. 21. — Cactus as an adhesive tcith iron arsenite,

Broicnsville, Tew., 1914-

Date.

Beetles
present.

Living.

Dead.

Feeding.

10

10

0

10

10

9

1

8

10

9

1

6

10

9

1

6

10

8

2

7

10

8

2

4

9

6

3

6

9

5

4

5

Not feed-
ing.

Apr. 13
Apr. 14
Apr. 16
Apr. 17
Apr. IS
Apr. 20
Apr. 21
Apr. 23

Feeding was very heavy on this plant, which had been growing
for some time in the pot and had been seriously attacked by aphides
on two occasions. Iron arsenite has some value as an insecticide, but
not as much as ferrous arsenate, even when properly made up, and
unless an effort is made to apply it in uniform coating on the foliage
it has little value as an insect destroyer.

CACTUS COMPARED WITH WHALE-OIL SOAP AS AN ADHESIVE.

On Februaiy 20, 1914, while conducting spraying experiments
against the belted cucumber beetle and cabbage looper {Autographa
hrassicce Riley) on cabbage on the farm of Mr. George Federhoff, near
Brownsville, Tex,, it was decided to make a comparison of whale-oil
soap and cactus as adhesives, without considering the cost of the
two products. One acre of cabbage was sprayed with 1 pound of
zinc arsenite (in powdered form) to 60 gallons of water, with the
addition of 35 pounds of cactus. The cactus was sliced and put in
the water on February 19, and had given up its glutinous matter
to the solution by the time spraying was begun the following
day. This mixture spread and adhered exceedingly well. The
next acre was sprayed with the same amount of poison, but whale-
oil soap was substituted for cactus. This was done both for a
comparison of adhesive qualities and to observe the effect of the
soap on the cabbage aphis {Aphis hrassicce L.), as in several spots

CACTUS SOLUTION AS AN ADHESIVE. 13

in this acre the aphis was making its appearance. The soap was
used at the rate of 3 pounds to 60 gallons of water. Very careful
notes were made on the sticking qualities of the soap, and it was
found that when compared at close range with the cactus spray the
soap equalled the cactus in spreading power, although lacking in
adherence. This information was obtained by observing sprayed
plants Avith and without a lens. It was soon seen that the cactus
spray adhered and dried on the foliage better than the soap spray.
This favored the cactus, since the heavy dews in the Rio Grande
Valley will wash poison having but slight adhesive qualities from the
foliage in a short time.

COPPER SULPHATE AS A PRESERVATIVE FOR THE CACTUS.

On April 6, 1914, 50 pounds of cactus were cut into small pieces and
placed in a barrel with 21 gallons of water, and on April 7, 1 pound
of copper sulphate was dissolved in 4 gallons of water and added to
the barrel which was numbered lot 6.

The solid portion of the cactus or prickly pear was removed before
adding the copper sulphate. This made 28 gallons in solution.
No chemical action was observed. The solution kept perfectly for
about four weeks, when it had to be discarded to make room for
other experiments. The temperature during this time averaged
about 70° F.

COPPER SULPHATE USED WITH ZINC ARSENITE.

After using the copper sulphate as a preservative for the juice
extracted from the prickly pear, the possibility of a chemical reac-
tion upon the addition of the arsenical to the solution was tested.
Upon the addition of powdered zinc arsenite at the rate of 1 pound
to 60 gallons of water a slight chemical reaction was noticed, evi-
dentl}^ the copper changing places with the zinc to a small degree. A
slight precipitate was formed, but not enough to cause any trouble
when a good pressure was maintained in the tank of the sprayer.
The precipitate was not increased after the mixture was allowed to
stand for three hours. No difference was observed in the effective-
ness of the arsenical, either with or without the addition of the
copper sulphate.

COPPER SULPHATE USED WITH LEAD ARSENATE.

The use of lead arsenate in combination with prickly pear with-
out the addition of some other chemical has never been a success. A
precipitate is always formed which makes it impossible to use the
mixture to advantage as a spray. The same proportion of cactus and
copper sulphate utilized in the zinc arsenite spray was here em-

14 BULLETIN 160, U. S. DEPARTMENT OF AGEICULTUEE.

ployed. On April 13, 1914, 1 pound of lead arsenate in the paste form
was placed in 20 gallons of cactus water which contained copper
sulphate in the amount of 1 pound to 28 gallons of water. It was
at once noticed that the copper sulphate retarded the precipitation
of the lead arsenate, so much so that the solution could be used as
a spray with some success, at a normal pressure Avith a hand pump.
This was encouraging, as it had been impossible to use lead arsenate
alone in combination with cactus as an adhesive. The writer would
recommend, however, that the foregoing combination be used on
a large scale onl}^ when a strong pressure can be maintained through-
out the oi^eration, or the results will be unsatisfactory.

The mortality in the expei-iments was practically the same as
when the arsenical was used alone. Had more experiments been
made in the field, in all probability a higher mortality would have
been observed in the end.

COPPER SULPHATE AND FERROUS ARSENATE.

The use of copper sulphate as a preservative for the cactus, com-
bined with ferrous arsenate to form a spray, did not appear to pro-
duce any chemical changes, no noticeable precipitate being found
that would prevent the use of the solution as a spray. It had been
expected that more of an action would take place when the ferrous
arsenate was added to the cactus water containing copper sulphate.
The ferrous arsenate was not altered in insecticidal value when mixed
with sulphate of copper.

EXPERIMENTS WITH OTHER PRESERVATIVES.

SALICYLIC ACID.

On March 13, 1914, 45 pounds of cactus were sliced and placed in
32 gallons of water, and in another lot 30 pounds were added to 24
gallons of water. The following day the solid portion of the cactus
was removed from the two lots and the water poured from both into
another receptacle. This made 56 gallons of the liquid to be pre-
served. One-fourth of a pound of salicylic acid was dissolved and
added to the cactus water, and the mixture was allowed to stand
exposed to the air. On April 1 the mixture was found to be in per-
fect condition. A bluish-white scum was noticed to have formed on
the surface shortly after the acid was dissolved in the water. To
dissolve salicylic acid a certain amount of alcohol is necessary. At
first the acid was dissolved in a 10 per cent solution of alcohol, but
it was later found that cactus water served equally well for this
purpose after fermentation was well under way, although action
was somewhat delayed.

CACTUS SOLUTION AS AN ADHESIV^E. 15

SODIUM BENZOATE.

Sodium benzoate was used in a limited way as a preservative for
the cactus solution. On March 14 one-fourth of a pound was dis-
solved in a small quantity of alcohol and added to a barrel contain-
ing 40 gallons of water in which 50 pounds of cactus had been placed
March 13, after removing the solid portion of the pear. The mixture
Avas stirred vigorously for five minutes and later covered. On April
2 an examination was made and the liquid used as a spray with zinc
arsenite. Only slight fermentation had taken place, and no diffi-
culty was encountered in applying the spray.

The first disadvantage in using sodium benzoate for such a purpose
is its cost. It is somewhat more expensive than other chemicals
of this class, and the element of cost is a primary consideration.
Another feature is that it is not easily dissolved, and unless it is
thoroughl}^ dissolved its powers as a preservative are considerably
lessened.

On April 2 sodium benzoate Avas again used in the proportion of
1 pound to 200 pounds of cactus in 100 gallons of Avater. This Avas
quite a concentrated mixture, but it kept in perfect condition for tAvo
Aveeks, at the end of Avhich time it Avas used up. The average temper-
ature a part of the time v^s 80° F.

THE COMMON PRICKLY PEAR CACTI AND THEIR CHEMICAL

COMPOSITION.

The common cactus or prickly pear of southern Texas is a A^ariety
known as " nopal " or " nopal azul " {Platopuntla Undhei'men
Engelm.). This is the variety with fiat, rounded leaves and growing
about 4 or 5 feet high, and it is found Avell distributed over southern
Texas. It is a native species Avhich A^aries considerably in coloration
of spines as well as in its general habit of growth. The fruit is
purplish throughout, more so than the more spiny variet}^, Plato-
puntla engehnarmll Salm., which is very similar in habit of groAvth,
but usually occurs farther west than the region occupied by this
species. The large spineless cactus frequently cultivated, but ordi-
narily not occurring abundantly in the cactus plains of southern
Texas, is a species Avhich has been called Platopuntia tuna Will.
It groAvs much taller than the common "nopal" and is knoAvn in
California as " mission pear " and in Texas as " Nopal de castilla."
It frequently groAvs 10 to 15 feet in height, with the trunk 12 inches
in diameter, and the joints in sha]:)e are more elliptical than rounded.
The fruit is considerably larger than that o.f the common "nooal"
and greenish throughout.

16

BULLETIN IGO, U. S. DEPARTMENT OF AGEICULTUEE.

The chemical analj^ses of these plants, taken from Bulletin No.
60 of the New Mexico Agricultural Experiment Station,^ are as
follows :

Table X-VII. — Chemical analysis of Platopuntia Hndheimeri.

Green.

Air dry.

Sample No

Spines

Water

Ash

Crude prot ein

Crude fat

Nitrogen free extract

Crude fiber

Organic matter

Per cent.
0.10

87.36
2.82
.60
.26
7.54
1.42
9.82

79.88
4.98
.45
.20
9.55
4.94
15.14

Per cent.
0.42

84.82

2.27

.96

.30

9.84

1.81

12.91

Per cent.

0.72

5.65

21.05

4.49

1.95

56.26

10.50

73.30

7516

Per cent.

5.20
23.45

2.12

.95

44.98

23. 30

71.35

7567

Per cent.
•2.60
6.55
13.95
5.92
1.82
60.61
11.15
79.50

ANALYSIS OF THE ASH.

[Sample No. 7515.]

Carbon per cent. . 0. 14

Sand do 29

Per cent in pure ash:

Soluble silica (SiO) 43

Iron (Fe) ' 20

Aluminum ( Al) OO

Manganese (Mg) 49

Potassium ( K) 14. 22

Sodium (Na) 35

Phosphoric acid radicle ( POO 1. 11

Sulphuric acid radicle (SOO •. 1. 15

Chlorine 2. 15

Carbonic acid radicle (CO3) 49. 12

Table XVIII. — Chemical annlyHs of PlafopunVia ciigelmannii.

Green.

Air dry.

65621

6575

7810

78411

65621

6575

7810

78411

P.ct.

P.ct.

0.32

91.07

2.00

.32

.12

4.95

1.54

6.93

P.ct.

0.04

89.41

1.60

.35

.23

7.21

1.20

8.99

P.ct.

P.ct.

P.ct.

3.33

7.33

20.80

3.29

1.20

51.43

15.95

71.87

P.ct.
0.33
6.83
14.05
3.07
2.00
63.48
10.57
79.12

P.ct.

Water

89.09

.91

.48

.33

7.31

1.88

10.00

85.41
.77
.46
.33

10.03
3.00

13.82

6.20

7.80

4.16

2.85

62.84

16.15

86.00

3.97

Ash

5.07

Crude protein

3.06

Crude fat

2.20

Nitrogen free extract

72.58

Crude fiber

13.12

Organic matter . .

90.96

Table XIX. — Chemical analysis of Platopuntia tuna.

Green.

Air dry.

Sample No

Spines

Water

Ash

Crude protein

Crude fat

Nitrogen free extract

Crude fiber

Organic matter

7519 7577

Per cent.

0.36

81.86

4.29

1.32

.28

8.88

4.07

14.55

Per cent.

92. 25
1.75
.63
.16
4.02
1.19
6.00

7519

Per cent.

1.82

5.1s

21.60

6.68

1.40

44.56

20. 53

73.17

Per cent.

8.12
20.80
7.53
1.85
47.60
14.10
71.08

iCJrifflths, David, and Hare, R'. F. Prickly pear and other cacti as food for stock, II.
N. Mex. Agr. ExtJt. Sta. Bui. 60, 134 p., 7 pi., November, 1906.

CACTUS SOLUTION AS AN ADHESIVE. 17

SUPERIORITY OF CACTUS FROM DRY LAND.

It has been found that cactus growing near resacas and in low
wet places yields less glutinous matter to the gross pound than it
does Avhen grooving on high dry soil. Thus time is saved in making
up a spraying solution if the cacti are collected from the higher re-
gions, and not in or near standing water.

On April 13, 1914, 75 pounds of cactus were placed in 40 gallons of
water. Twenty-four hours later the cactus was removed and al-
lowed to drain for about one-half hour. It weighed 85.5 pounds,
or 10^ pounds more than when placed in the water. Another lot of
110 pounds was increased in weight to 124 pounds by leaving it
in water 24 hours. However, when the cactus is sliced and allowed
to remain in water until fermentation is well under wa}^, there will
be a slight decrease in weight. This will not happen where a pre-
servative is used.

ADVANTAGES IN THE USE OF CACTUS AS AN ADHESIVE.

By the use of cactus as an adhesive not only do the arsenicals
give better and more lasting results, but considerable expense may
be saved in another way. In the Southwest, where all insecticide
material must be shipped in from a great distance, the expense of
transporting this material is often more than the cost of the in-
secticide itself, so that material of a poor quality is often used in-
stead. For some years arsenicals in the paste form have been exten-
sively used by fruit and truck growers on account of their better
adherence and lasting qualities, but where a good adhesive is used
the writer much prefers arsenicals in the powder form. In conduct-
ing experiments in the insectary and in the field at no time have
the powdered arsenicals proved less effective, and at times the mor-
tality would be considerably above that shown in another experiment
conducted at the same time with arsenicals in the paste form. Better
results have been obtained in using 1 pound of zinc arsenite in pow-
der form with cactus than by the use of 3 pounds in the paste form
to the same amount of water. Thus equal results may be obtained,
with a reduction of G6 per cent in express and freight charges paid
in securing arsenicals from a distance.

QUANTITY OF CACTUS TO USE.

The amount of cactus that may be used with good results varies
with the environment under which the plants have been gi'owing.
If the plants have been growing in or near water it will be neces-
sary to increase the quantity of cactus used to each gallon of water.
In general, the correct proportion will range from i pound to 1

18 BULLETIN 160, U. S. DEPARTMENT OF AGEICULTUEE.

pound to e\'eiy gallon of water used in making up the spraying
mixture. These proportions have given the most favorable results
in all experiments conducted so far. When amounts in excess of 1
pound to each gallon of water are used the adhesive powers do not
appear to be increased to any great extent, and on the other hand
difficulty is experienced in applying the spray, particularly'- where
very fine nozzles are employed.

ZINC ARSENITE AS AN INSECTICIDE.

Zinc arsenite has been used both in the paste and powder forms with
much success for the belted cucumber beetle, as well as for some other
insects of this class. It has proved to be one of the most effective
sjDrays for use in humid climates, as it appears to last longer. No
other arsenical has given better results, and in the majority of cases
the mortality has been higher than with any other arsenical spray.
The powder when used with cactus to make it adhere is to be pre-
ferred for general use over any arsenical now on the market. This
spray in the writer's opinion surpasses in lasting qualities any of the
arsenicals and at the same time gives a higher mortality. In action
it is somewhat slower than Paris green, but it gives better results in
the end. The writer would not recommend, however, that zinc arse-
nite be used on plants that are nearly ready for market, for the
poison does not wash off easily,

FERROUS ARSENATE AS AN INSECTICIDE.

Ferrous arsenate has given very good results in combination with
cactus to increase its adhesive powers. No serious effects from its use
on the most delicate foliage have been observed. The cost of the
product at the present time places it beyond general use as an insecti-
cide. The ferrous arsenate in the powder form is very easily brought
into suspension, requiring less time than some of the other arsenicals
now more extensively used to destroy biting insects. Another feature
in the use of this arsenical is that it remains in suspension exceed-
ingly well and settles very slowly to the bottom of the tank. This
makes it a most desirable poison for use with small sprayers not
equipped with agitators,

IRON ARSENITE AS AN INSECTICIDE.

Iron arsenite was given a trial against the belted cucumber beetle
only, and was found to give varying results. The powder was made
into a spray and applied both with cactus as an adhesive and without
the cactus. The iron arsenite is quite hard to bring into suspension
and soon settles to the bottom of the spray tank unless constantly

CACTUS SOLUTION AS AN ADHESIVE. 19

agitated. Its effectiveness as an insecticide was disappointing; in
fact, it is so low that it is doubtful that this arsenical can ever come
into general use as a spray. Much difficulty was experienced in ob-
taining uniform distribution over the surfaces sprayed, even when
used with cactus. The cactus increased its adherence and sprajdng
qualities, but not sufficiently to remedy matters completely. The
foregoing experiments show its effectiveness as compared with fer-
rous arsenate, zinc arsenite, lead arsenate, and Paris green.

FINAL RESULTS FROM SPRAYING.

The pot experiments carried on in the insectary for the belted
cucumber beetle and the other species concerned were undertaken
to assist in checking up results in the field. They served for more
than this, however, for in a short time it was possible to accumulate
much data as to the effectiveness of each spray that otherwise could
not have been secured in nearly so short a time, while the estimates
as to mortality in each of the experiments made would have been
much less conservative.

It was found that the beetles could be best controlled by spraying
with zinc arsenite or with Paris green. The other arsenicals em-
ployed, while effecting a control in most cases, did not give as high
mortality as the two arsenicals mentioned. The number of appli-
cations rendered necessary varied with the location of the sugar
beets, i. e., their distance from crops where the beetles were breeding
in large numbers. One plat of sugar beets was sprayed only once,
while on the other hand several plats of beets, spinach, and cabbage
were sprayed from two to four times in order to prevent the crop
from being badly stunted in growth. The greatest damage is done
from the time the beets begin coming up until the leaves have reached
a height of 10 inches. Attention should be given the crop from the
time the seeds are planted, in order that no serious damage may be
done before remedial measures can be put to practice.

RECOMMENDATIONS FOR CONTROL.

The control of such pests as the belted cucumber beetle does not
require the attention necessitated by some of the noxious caterpillars
and sucking insects. But to keep the injury down to the minimum
frequent observation should be made while the plants are small, as
this is the time when the beetles are capable of doing the greatest
amount of damage.

If the beetles are present in sufficient numbers partially to defoliate
a few plants, it is time to begin spraying. It may be necessary to
spray only once in order to effect control, but this will depend upon
the surrounding vegetation as well as upon the weather conditions.

20 BULLETIN 160, U. S. DEPARTMENT OF AGEICULTURE.

Any of the ursenicals may be used in the form of a spray to control
this beetle. If arsenite of zinc in paste form is to be used, the writer
will recommend 3 pounds to 50 gallons of water, in combination
where possible with some adhesive, in order that best results may be
obtained. In the Southwest the prickly pear serves the purpose best,
because better results have been obtained where it was used than
with any one of several other adhesives. From an economic stand-
point, also, it has first rank as an adhesive and spreader. It has been
ascertained that zinc arsenite in the powder form in the proportion
of 1 pound to 50 gallons of water in combination with cactus gives
a little higher mortality than 3 pounds in the paste form, and a more
extensive use of this powdered form is to be recommended, particu-
larly in the cactus-growing region or where the glutinous matter of
this plant can be had for use in the spray.

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1915

BULLETIN OF THE

No. 161

Contribution from the Bureau of Entomology, L. O. Howard, Chief,
December 18, 1914.

THE MEDITERRANEAN FRUIT FLY IN BERMUDA.

By E. A. Back,

Entomological Assistant, Mediterranean Fruit-Fly Investigations.

INTRODUCTION.

This paper is the result of an investigation of the fruit-fly situa-
tion in Bermuda, made by the writer during December, 1913, at the
request of Mr. C. L. Marlatt, Assistant Chief of the Bureau of Ento-
mology and chairman of the Federal Horticultural Board, in order to
gain at first hand information that might be of value to the Horticul-
tural Board in framing its quarantine regulations against this pest.

HISTORY OF THE FRUIT FLY IN BERMUDA.

The Mediterranean fruit fly, Ceratitis capitata Wied., was not
recorded in literature from Bermuda until 1890, when Riley and
Howard * report receiving specimens of infested peaches from St.
George. However, it had been known as a pest in Bermuda many
years before this date, as Mr. Claude W. McCallan, who forwarded
these specimens to Washington, stated in his accompanying letter
of April of that year that peaches had been subjected to its ravages
during the 25 years previous. About the year 1865 a vessel carrying
a cargo of fruit from the IVIediterranean regions, bound for New York,
was forced by severe storms to discharge her catgo in Bermuda, and
it is the general belief that at that time the pest gained its foothold
in this English possession. But whatever the source of infestation,
it is a well-laiown fact that for nearly 50 years the peach industry of
these islands has been a ruined one, and that at the present time the
fruit fly is generally distributed over the islands ready to infest all
host fruits coming to maturity.

LIFE HISTORY.

Those wishing a detailed description and life history of the Mediter-
ranean fruit fly should refer to the publication of Quaintance,^ pub-
lished by the Department of Agriculture.

1 TJiloy, C. v., and Howard, L. O. The peach post in Bermuda. {Ceratitis capitata Wied.) Order
Diptera: Family Tryijetidae. In U. S. Dept. Agr., Div. Ent., Insect life, v. 3, no. 1, p. 5-8, 2 figs., August,
1890.

2 Quaintance, A. L. The Mediterranean fruit fly. U. S. Dept. Agr., Bur. Ent. Circ. no. 160, 25 p.,
Ifig., Oct. 5, 1912.

Note.— This bulletin discusses the liistory of the fruit fly in Bermuda, the life history of the insect, and
the possibility of eradicating it from Bermuda; the bulletin is of interest to entomologLsts.
66697°— 14

2 BULLETIN 161, U. S. DEPARTMENT OF AGRICULTURE.

EGG. LARVA, AND PUPA.

Col. W. R. Winter, in his bulletin entitled "The Fruit Fly," pub-
lished by the Bermuda Department of Agriculture in 1913,^ gives the
only data secured in Bermuda on this pest up to that date. He
states that he has found that to pass through the egg, larval, and
pupal stages the fly requires from 17 days, during the heat of August,
when the monthly mean temperature averages about 81° F., to 6
weeks in winter, when the mean temperature averages about 63.2° F.

With the assistance of Mr. E. J. Wortley, Director of Agriculture
of the Bermuda Department of Agriculture, the writer found that the
pupal stage alone in Bermuda, when the daily mean temperatures
ranged between 62.5° and about 64.8° F., might be lengthened to
about 31 days under normal conditions.

Back and Pemberton have found that a temperature varying from
r)8° to 62° F. increases pupal life to from 29 to 31 days. They have
likewise found that while eggs hatch in from 2 to 3 days in Hawaii
at a mean temperature of about 79° F., hatching may be delayed
until 6 days after deposition when the mean temperature drops to
about 71° F., or until 7 to 14 days when the temperatm-e ranges
from 54° to 57° F. It has also been found m Hawaii that while the
larval stage may require a minimum of 5 to 6 days at a mean tempera-
ture averaging about 79° F., it requires from 36 to 53 days in apples
at temperatures ranging from 56° to 57° F.

These data are given to substantiate the belief of the writer that
the duration of life from the egg to the adult in Bermuda where the
winter mean averages -about 63° F. is somewhat over two months, and
may even be three months under unfavorable circumstances.

THE ADULT.

In the Hawaiian Islands, where the summers are somewhat cooler
and the winters slightly warmer than in Bermuda, adult flies have
been kept alive over five months. Wliile the majority do not live
this long, the belief has been expressed that a few flies may live to be
over six months of age, especially during such cool weather as ob-
tains in Bermuda during the winter. Both sexes are sexually im-
mature when they emerge from the pupa. At temperatures varying
from 76° to 78° F., the sexes mate when 5 to 8 days old, though not
until 2 weelvs old at 61° to 64° F. One prolific female deposited on
an average of about 4.5 eggs per day during the fij*st 18 weeks of
her life, and had not then reached her egg-laying capacity. As
many as 25 eggs have been laid by a single female in one day. Female
flies do not lay a large number of eggs at one time and then die, as
many believe, but lay quite regularly a few eggs nearly every day
throughout life.

> Winter, W. R. The fruit fly. Bermuda, 1913. 14 p. (Bermuda Dept. Agr., E. J. Wortley, director.)

MEDITERRANEAN FRUIT FLY IN BERMUDA.

HOST FRUITS IN BERMUDA.

Col. W. R. Wintor, in the bulletin previously mentioned, lists 47
fruits subject to attack. To this list for Bermuda should be added
the ball kamani (CalopJiyllum inopJiyllum) , the prickly pear (Opuntia
sp.), and tho acordia. While the list of host fruits given is so large
that one receives the impression that the fruit fly has an abundance
of fruit in which to develop, conditions are quite the opposite in
Bermuda. After having carried on a clean-culture campaign against
this pest in the Hawaiian Islands, where there exists a very gi-eat
abundance of many host fruits, the writer was surprised at the scarcity
of host fruits in Bermuda. In Table I is recorded the vegetation
found growing in portions of the city of Hamilton.

Table I. — Vegetation in Hamilton, Bermuda, with reference to host fruits/or the Mediter-
ranean fruit fly. ^

Kind of tree.

Number of diflferent trees on various properties.^

1

2

3

4

5

6

7

8

9

10

u

12

13

14

A pple

1
6
2

I

24
23

8

1

1

1

10

Anona

Aracaria

1

Avocado

"i'

1

2
75
2
2

ii

Banana

'1

1

1
1

6S

Cedars

1

Chinaberry

15

Citrus

Coifee

Crap3 myrtle

1
1

1

1
"i'

3
6
2
9

Croton

....".:

10

Eugenia

Fiddlewood

3

Guava

Hibijcus

^

12
1

1
12

6

Kamani, winged

1
1

22

10

Mango

Mulberry

1

Oleander

1

1

2
1
3

8

Pandanus

1

"i"

1

1

12
10
2

1

97

Peach

Piseonberry

1

2

Poinoiana

1

Roses ."

Rubber tree

1

1

1

Sapodilla

1

Thcvetia

1 All trees and shrubs were recorded except the following nonhost plants: Bamboo 5, buttonwood 5,
Dracaena 3, elder 1, Lautana 3, Mimosa 2, pomegranate 1, privet 2, Australian pino 2. tamarind 1, sea grape
2, coconut palm 1, palmetto 8, date palm 8, sago palm 3, Poiasetta 2, Euphorbia 7, Althea 1. Host plants
of the Moditerraiiean fruit (ly are in italics.

2 No3 1 to 11 represent private premises; Nos. 12 to II, city blocks.

The number of trees and slirubs in Bermuda which bear fruit
subject to attack is very small. Out of 9,828 acres of land only 2,636
acres were recorded under cultivation in 1901, and this acreage lias
but slightly increased. The principal products raised for expert,
potatoes, onions, arrowroot, lily bulbs, and garden vegetables, except
peppers, are not subject to attack. On the uncultivated areas the
host fruits are mainly conspicuous by their absence. In such areas

4 BULLETIN 161, U. S. DEPARTMENT OF AGEICULTURE.

the escaped Surinam cherry {Eugenia micheli) and a small species of
prickly pear (Opuntia) are to be found in varying numbers. In the
Tuckerstown district the former is quite abundant, while the latter
is plentiful in sandy locations, as noted especially in Southampton
Parish along the south shore. The soil of Bermuda, being very shal-
low, does not support dense vegetation. Cedar trees are so generally
distributed over the islands that the landscape, as viewed frcm a
tower, appears blackened by them. One can often walk among them
long distances, as distances go in Bermuda, without seeing a single
tree bearing fruit subject to attack. Often the cedar,' fiddlewood
(CitJiarexylum quadrangulare) , the oleander {Nerium oleander), the
Lantana (Lantana odorata and L. crocea), the life plant (Bryophyllum
calycinum), grasses, and a few weeds are all that one sees. Some of
the small islands of the group were found to support nothing subject
to attack. In and about Tuckerstown and the adjoining limestone
region the vegetation is more dense, and progress through the woods
is made difficult by the presence of rocks and vines. In this region
are to be found many neglected bittersweet oranges, whose fruits,
according to Col. W. R. Winter, are quite eagerly gathered for
marmalade, although often the trees are difficult of access.

It was found that the principal fruits supporting the fruit fly in
Bermuda were:

(1) The loquat or Malta plum {Eriohotrya japonica), which ripens
during January, February, and March.

(2) Peaches, which ripen during late March, April, May, June, and
early July.

(3) Surinam cherries (Eugenia micheli), the first crop of which
ripens during May and the second crop throughout summer and early
fall.

Director of Agriculture Wortley informed the writer that the cul-
tivated bell pepper was also a source of food for the fruit fly during
the summer months.

AMOUNT OF FRUIT.

No large amount of fruit subject to infestation by the fruit fly is
to be had in Bermuda at any season of the year unless it be during the
time when Surinam cherries are in season. It would not be just to
Bermuda horticulturists for one visiting these charming islands for
so short a time during the winter to state that many of the more
tropical fruit trees appeared stunted and grown only with great care
in favored gardens; yet it so seemed to the writer. It would be very
easy to count the number of apple, guava, mango, and bestill trees
(Thevetia) in the islands. One common guava was pointed out in a
beautiful garden as a curiosity. Only one winged kamani, one sweet
almond (Terminalia) and one apple tree were seen. The avocado,
citrus, papaya, and peach trees were more numerous, tho\igh by no

MEDITERRANEAN FRUIT FLY IN BERMUDA. g

means plentiful. The loquat seemed to be the most abundant culti-
vated fruit, but few of the trees were as large or as well developed
as those in Florida or Hawaii, and their ripening fruit was, at the
time of the writer's visit, everywhere generally infested. Experi-
menters wishing to rear flies in large numbers for scientific purposes
would be forced, in the opinion of the writer, to depend upon imported
fruits, such as apples, in order to have a constant and satisfactory
supply.

POSSIBILITY OF ERADICATION.

From the experience of the writer with clean cultural methods
covering nearly two years in the city of Honolulu, Hawaiian Islands,
he beUeves that the Mediterranean fruit fly can be eradicated from
Bermuda within three years at the longest without the expenditure
of a prohibitive amount of money. If the fruit flies were not capable
of living so long in the adult stage, it is probable that the work of
eradication could be accomplished in less time. There is probably no
country in the world where the fruit fly exists in which the work of
eradication could be undertaken with such assurance of success, pro-
vided the work were placed in the hands of a persistent, weU-inf ormed,
intelligent person who could carry on an uninterrupted campaign au-
thorized by adequate legislation. The fruits infested at the present
time are such that no citizen would be forced to bear any real finan-
cial loss as the result of such a campaign. The peach and loquat
fruits are practically all destroyed yearly by the fly, and the Surinam
cherries are of no commercial value. By the judicious use of axe and
saw and by thorough cutting of flowers or young fruit on those few
trees that can not for various reasons be either cut down or prevented
temporarily from bearing by severe pruning, the host fruits could be
eliminated. It has already been shown that oranges and grapefruit
act more as traps for the fruit fly than as hosts if allowed to remain
on the tree until sufficiently ripe for table purposes, and such trees
of value need not be destroyed provided the fruit be gathered before
it becomes overripe.

The Bermuda agricultural authorities had already secured the
passage of legislation against this pest and started clean cultural
work as early as March, 1907, when the board of agricultiu-e, as
stated by Col. Winter in a letter to the writer under date of February
20, 1914, was given the power to ''prohibit the growing of any fruit
or vegetable, to clear off fruit, cut back or destroy as necessary any
trees or vegetables, and to clean up the ground beneath them."
The inspection work was akeady yielding good results when the fruit
fly destruction act of 1907, under which it was being carried on,
lapsed on December 31, 1910. No work was done during 1911 and
1912, although a new act was passed in June of the latter year. Dur-
ing 1913 inspections were again started, but apparently had accom-

6 BULLETIN 161, U. S. DEPARTMENT OF AGRICULTURE.

plished little in controlling the fruit fly, as evidenced by the general
infestation noted by the writer in ripe loquats and Thevetia in Decem-
ber of that year.

In other words, the money appropriated in Bermuda for inspection
work against the fruit fly has not yielded practical results. The
small amount of fruit grown in the islands does not warrant the
expenditure of money except with the object of extermmation in
view. It is only by extermination that fruit growers in Bermuda
can hope to produce those fruits which her climate makes possible
without maintaining a system of inspection that at best will yield but
temporary results and at the same time be a source of perpetual
expense amounting to more than the fruits now grown are worth.
The work carried on by the Federal Government in Hawaii has
clearly demonstrated the fact that no clean cultural method will lead
to any lasting beneflcial result unless the person in charge of such
work be given the power, either personally or through able inspectors,
to plan the destruction of all fruit before it begins to ripen, either by
the destruction or severe pruning of host trees or the gathering of
fruit before it is sufficiently developed to become infested. Just so
long as notices are served on residents demanding them to destroy
fruits on their properties already known to the inspector to be infested
with the fruit fly, just so long will failure attend clean-culture work.
The director of a clean-culture campaign must have full power to
destroy fruit whenever he knows that the facts demand it. Human
nature is the same the world over. Lack of interest on the part of a
few citizens when the destruction of fruit is left in their hands can
defeat and has defeated the plans of the most able directors. These
statements regarding clean-culture work are based upon the results
following the expenditure of many thousand dollars in similar work
in the Hawaiian Islands and elsewhere.

BERMUDA AS A SOURCE OF DANGER TO THE UNITED STATES.

If Bermuda were in direct communication with the southern
Atlantic ports of the United States, to which she is so closely situ-
ated, she would be a source of great danger to the fruit interests of
the Southern States. However, her only regular and direct commu-
nication is by means of vessels plying between Hamilton and New
York, a distance of about 701 miles, for the passage of which about
two days is required. Another line of steamers, equipped with
hmited passenger accommodations and running about every four
weeks, connects London and Hamilton. The vessels of this last
company usually continue on to Cuban ports, and thence to a south-
ern port of the United States for freight before returning to England,
Such small quantities of fruit are brought to maturity in an edible
condition in Bermuda that there is very shght probability of any

MEDITERRANEAN FRUIT FLY IN BERMUDA. 7

being carried to the United States. Native-grown fruit is scarce
and a luxury even for the few who are able to grow it. Practically
all the fruit consumed in Bermuda and on the ships plying between
Hamilton and New York is grown in the United States. Further-
more, the climatic conditions in and about New York are known to
be decidedly against the establishment of the fruit fly, even if it
should be accidentally introduced. The fact that ships have been
plying between New York and Bermuda for many years wdthout the
pest having become established on the mainland is an argument in
itself. Practically all agricultural produce grown in Bermuda can
not be marketed profitably in New York, where it is for the most
part consumed, unless it is placed on the market before that grown
in the Southern States is shipped north. Thus the bulk of Bermuda-
grown vegetables, whether subject to infestation or not, arrives in
New York at a season when the climate is too cold for the pest to
survive. With the addition at the present time of the strict quar-
antine regulations against all Bermuda-grown fruits or vegetables
subject to attack, to the restrictions already placed by nature and
the market, it would appear that Bermuda is a source of very little
danger to the United States from the fruit-fly standpoint.

CONCLUSION.

The Mediterranean fruit fly, Ceratitis capitata Wied., was intro-
duced into the Bermuda Islands probably about 1865, when fruit
supposedly infested by this pest was unloaded there from a storm-
tossed vessel from the Mediterranean region. Since that time the
fruit fly has spread over the entire 19^ square miles of roUing coun-
try of which these islands are ^composed, and long since has ruined
the excellent peach industry enjoyed by Bermuda in the early days
and has caused such discouragement among prospective fruit grow-
ers that at the present time native-grown fruit in Bermuda is a
luxury.

While Bermuda is probably at present a source of comparatively
small danger to the United States as a source of infestation by the
Mediterranean fruit fly, both on account of her trade relations and
the climatic conditions surrounding New York, the extermination of
the pest in these islands wiU be decidedly to the advantage of both
Bermuda and the United States. All parts of Bermuda are easy of
access. The topography is cut up by harbors, lakes, and roads into
small areas that can be easily inspected; the trees and shi'ubs, the
fruits of which are subject to infestation, are surprisingly few numeri-
cally, and a large portion of the uncultivated lands supports little
that is subject to attack.

Experience in all countries where clean cultural work has been
undertaken, but especially in the city of Honolulu, has shown that

8 BULLETlJSr IGl, U. S. DEPARTMENT OF AGRICULTUKE.

no lasting beneficial results will foUow such work as has been carried
on in Bermuda unless extermination is the object in view. The value
of the fruit grown in Bermuda is not sufficient to warrant work being
carried on with any other object. In no country where the fly now
exists could work of extermination be undertaken with such assur-
ances of success as in Bermuda. If clean cultural work were supported
continuously by adequate legislation and undertaken by a person suf-
ficiently conversant with the problem and eager to make a unique
record in the entomological world, the Mediterranean fruit fly could
be exterminated from Bermuda within three years, without the ex-
penditure of a prohibitive amount of money.

WASHIWCTON : GOVERNMENT FEINTING OFFICII : 1914

BULLETIN OF THE

No. 165

Contribution from the Bureau of Entomology, L. O, Howard, Chief
December 31, 1914.

(PROFESSIONAL PAPER.)

QUASSIIN AS A CONTACT INSECTICIDE.

By William B. Parker,

Entomological Assistant, Bureau of Entomology.^

INTRODUCTION.

Quassia chips, the active principle of which is quassihi, have been
employed for many years in the preparation of spray solutions for the
control of the hop aphis (Phorodon Jiumuli Schr.). Several formulas
have been followed, and there are several methods of preparation
accordmg to these formulas. Several factors have brought about the
variations m the formulas, (1) instabihty m the percentage of quassiin
in the chips, (2) the total amount of available quassiin in the chips
probably not extracted, due to the method of preparation, and (3)
the fact that there appeared to be no fundamental data accumulated
on this subject. The writer accordingly commenced the investiga-
tion, which has been taken up from an insecticidal standpoint, and
any chemistry that is mentioned other than veiy simple matters is
taken from the various sources. Acknowledgments are due to Prof.
George P. Grey, of Berkeley, Cal., and Mr. G. H. P. Leichthardt, of
Sacramento, Cal., for valuable suggestions, and to Mr. R. E. Camp-
bell, of the Bureau of Entomology, who ably assisted the writer in
determhiing the efficiency of the several formulas.

During the investigation of the life history and control of the hop
aphis ^ it was observed that there were several formulas for the use
of quassia chips. These all appeared to give satisfactory results
when carefully prepared and appUed, but it will be observed from
the following formulas that if the weaker one kiUed the aphides, the
use of the stronger one resulted in a waste of material and extra
expense.

1 Resigned August 31, 1914.

2 Parker, Wm. B., The Hop Aphis in the Pacific Region. U. S. Dept. Agr., Bur. Ent. B\i\. Ill, 39 p.,
S fig., 10 pi., May 6, 1913.

Note. — The results of an investigation to determine the mo.st suit alile solul ion of qua.ssiin for u.se as a spray
for the control of the hop aphis are discussed in this bulletin.
67215°— 14

2 BULLETIN 165, U. S. DEPARTMENT OF AGRICCLTURE,

The following formulas are t}^ical examples of the variation in
tlie amount of ingredients and the cost per 100 gallons:

Xo. 1.

No. 2.

No. 3.

oounds. .

2.8
1.6
100
31

S

6

100

69

9

Whale-oil soap

:..do....

6

gallons..

100

Cost per 100 gallons

pents

74.2

These formulas are concocted differently by different growers.

Some soak the chips 24 hours in a barrel of water and then boil them

for 2 hours. Some boil them for 2 hours without previous soaking,

and others boil them with the whale-oil soap. The several formulas

and methods of preparation all have their advocates among the hop

growers.

CHEMICAL LITERATURE ON QUASSIIN.

The quassia chips commonly used in preparing spray solutions are
the wood of the Jamaica quassia (Picrasma excelsa Swz.). The
literature on the chemical nature of quassiin, the active principle of
quassia wood, was found to be very limited, but the few important
references that the writer was able to obtain are discussed below.

The wood of Picrasma excelsa (Swz.) Plancli. {Quassia e Swz.; Q. polijgama Lind-
eay; Piceaena e Lindl.; Simaruba eD. C.) or of Quassia amara L. (Fam. Simarubacese).

Description. — Jamaica qiu^ssia. Occurring in various forms, usually chips, raspings,
or billets, yellowish white or pale yellow, and of rather coarse texture; odor slight;
taste intensely bitter; medullary rays containing tetragonal prisms or small, arrow-
fihaped crystals of calcium oxylate. Billets of Jamaica quassia are usually 12.5 cm.
or more in diameter; in tangential section the medullary rays are mostly 3 to 5 rows
of cells in width.

Surinam quassia. Occurring usually in billets not exceeding 7.5 cm. in diameter;
the wood is heavier, harder, and more deeply colored than that of Jamaica quassia,
and the medullary rays in tangential section are mostly 1 or 2 rows of cells in width.

Constituents. — Although Jamaica quassia is said to contain traces of a yellowish
alkaloid, giving a fine blue fluorescence with acidulated alcohol, the important bitter
principle is a neutral, crystalline substance, commonly known as quassiin, but deter-
mined by Massute to be a mixture of two crystalline bodies, which he denominated
a- and ^- picrasmin.

Quassiin is extracted by neutralizing the aqueous infusion with soda, ])recipitating
with tannin and decomposing the precipitate with lead oxide or lime. It is commonly
said to exist to the extent of only 0.05 to 0.15 per cent, but really exists in much larger
amoimt, Wiggers says 0.75 per cent. This discrepancy is probably due to the fact that
it is difficult to procure in the pure state, and that the purification processes involve
considerable loss. Quassiin crystallizes in needles or prisms, and is soluble in alcohol
and in chloroform and in 1,200 parts of cold water. Its bitterness is most intense. The
a-picrasmin (C35H4eOio) melts at 204° C. The /?-picrasmin (C36H4SO10) at 209° to
212° C. (408.2°-413.6° F.). The bitter principle of Surinam quassia is closely related
and of similar action, but not identical.^ To it the name quassin is commonly
applied.

1 Hare, H. A., Caspari, C, and Rusby, H. H. National Standard Dispensatory, ed. 2, revised and
enlarged, p. 1334, Philadelphia, 1909.

QUASsmsr as a contact insecticide. 3

Quassine, the active principle of Quassia, amara, is amorphous or crystalline. It has
been isolated by Winkler. It is colorless, inodorous, opaque, and inalterable in the
air, slightly soluble in water, much more soluble in water charged with salt or organic
acids, and in alcohol.

Action on plants: Plants are not injurovl by spraying with aqueous extracts of
quassia.'

Quassia. — Constit.: Wood: Picrasmin, C;;5H460io: quassin, CjoIIisOa (or, C;j2H420io
[?]); quassol, C^qH^oO — HjO; alkaloid; resin; mucilage; pectin. — Bark: Quassin;
alkaloid; resin; pectin. (Quassia amara contains 4 bitter principles; Picrxna excelsa
contains only 2): quassol, — -^

"Quassiin (CgoH^jOio) may be obtained in a fairly pure state by exhausting quassia-
wood with hot water, precipitating the solution with neutral lead acetate, removing
the excess of lead from the filtrate by sulphuretted hydrogen and shaking the filtered
liquid with chloroform. On evaporation, the quassiin is obtained nearly colorless,
and, with some difficulty, in a distinctly crystalline condition. Quassiin has an in-
tensely and very persistent bitter taste. It is s^jaringly soluble in cold water, more
readily in hot water, and is easily soluble in alcohol. Its best solvent is chloroform,
which extracts quassiin readily from acidulated solutions.

An aqueous solution of quassiin does not reduce Fehling's solution cr an ammonio-
nitrate of silver. The solid substance gives no coloration (or merely yellow) when
treated with strong suli:;huric acid, or with nitric acid ]-25 sp. gr. ; nor is any color
produced on warming. * * *

A solution of quassiin gives a white precipitate with tannin. The reaction is used
by Christensen, Oliveri, and others, to isolate quassiin from its solutions, and by
Enders to separate it from picrotoxin. In the author's hands the reaction has not
proved satisfactory. The liquid is very difficult to filter, and the filtrate still retains
an intensely bitter taste, showing that the precipitation is very incomplete. As an
analytical method the reaction is useless, but it is of some value as a qualitative test.
The test must be made in cold solution. Possibly a more complete precipitation of
quassiin by tannic acid might be effected in an alcoholic solution.

Quassiin gives a brown coloration with ferric chloride. The reaction is best observed
by moistening a quassiin residue in porcelain with a few drops of a weak alcoholic
solution of ferric chloride, and applying a gentle heat. A fine mahogany-brown
coloration is produced." ^

The quassiin used in the follo^ving experiments was extracted
accordmg to directions given by AUen.^ It was further found
thut when boiled in alcohol a precipitate formed. This was fil-
tered off, the filtrate evaporated to dryness over a water bath, and
the resultmg dark resinous material extracted with boihng water.
When extraction was complete a dark brown crusty material
remained. The resulting extract was light yellow and perfectly
clear. It was found to be intensely bitter.

"When cool this aqueous solution was extracted with cliloroform,
evaporated over a water l)ath, and weighed and made into a per-
centage solution.

1 Bourcart, E., Insecticides, Fungicides and Weedkillers, p. 376. London, 1913.

2 Merkes 1907 Index, ed. 3, p. 366. New York, 1907.

2Allen, A. H., Commercial Or£;anic Analysis, ed. 2 revised and enlarged, V. 3, pt. 3, p. 187-188, Phila-
delphia, 1890.
* Except the solution was not acidulated before extraction with acid.

BULLETIN 165, U. S. DEPARTMENT OF AGEICULTURE.

In stud}iiig the use of quassiiii as a contact insecticide it became
desirable to determine in what solvents and solutions this com-
pound was soluble. Table I gives the results of the experiments
which were carried out with this purpose in view.

Table I. — Results of solubility tests for quassiin.

No.

Material.

Action.

1

2
3
4
5
0
7
8
9
10
11

Readily soluble.
Not soluble.
Readily soluble.

Do.

Do.
Sparingly soluble 1-1,200.
Not soluble.

Do.

Do.

Do.
Possibly soluble.

Ether

Ethyl alcohol

Gasoline

Carbon tetrachlorid . .

RESULTS OF TESTS WITH SOLUTIONS.

Potassium hydroxid

Sodium hydroxid

Calcium hydroxid

Potassium cy anid

Sodium carbonate

Hydrocyanic acid

Ammoniimi h j-drate

Whale-oil .soap (alkaline).

Sodium chlorid

Hydrochloric acid

Siilphuric acid

Nitric acid

Acetic acid

Readily soluble, solution vellow.

Do.

Do.

Do.

Do.

Do.

Do.

Do.
Apparently uisoluble.

Do.

Do.

Do.

Do.

The foregoing table represents the results of experiments which
were conducted with quassiin in an attempt to determine some cheap
solvent or solution, other than hot water, b}' which it could be
extracted from the wood.

EXTRACTION OF QUASSIIN FROM SOLUTIONS.

It was found that when the solutions of potassium hydroxid, sodium
hydroxid, sodium carbonate, etc., with quassiin, were acidulated
with sulphuric acid, the quassiin could be readily removed in chloro-
form. This process v/ould apply when testing the percentage of
quassiiii in such solutions.

DETERMINATION OF PURITY OF QUASSIIN USED.

Since the purity of the quassiin used in spraying experiments is
an important factor in figuring proportions, an attempt was made to
determine the amounts of material other than quassiin which might
be present in the stock solution.

Following a suggestion in Allen, tannin was added to an aqueous
solution of quassiin taken from the stock solution. A fine precipitate
appeared, but unfortunately it passed through an ordinary filter
paper.

QUASSIIN AS A CONTACT INSECTICIDE. 5

It being observed that tannin is not extracted from an aqueous
solution by chloroform, an attempt was made to collect the chloroform-
soluble material which was not precipitated by the tannin. The
solution was accordingly shaken with chloroform, and the chloroform
separated in a separating fujmel. A^^len replaced in a(|ueous solu-

Fig. 1.— Compressed-air spray machine used in applying
quassiin solution. (Original.)

tion, the extracted material was found to be intensely bitter and gave
all the appearance of being quassiin. It is evident that aU of the
quassiin is not precipitated by tannin.

Because the material used proved effective as an insecticide at
dilutions of 0.4 grams to 1,500, 1,800, and 2,000 cubic centimeters,
the writer believes that it was comparatively pure quassiin.

INSECTICIDAL VALUE OF QUASSIIN.

The determination of the insecticidal value of cjuassiin is the main
object of this investigation. In accomplishuig this object an attempt
is made to compare the action of quassiin to the action of a standard
contact insecticide. Nicotine sulphate is taken as the standard,

6 BULLETIN 1G5, U. S, DEPARTMENT OF AGEICULTUEE.

and in these experiments is used at the rate of 1-2,000. The nico-
tine sulphate used was stajidardized to 40 per cent and the solution
of quassiin was used so that it would correspond with the 40 per cent
solution of nicotine sulphate. For instance, instead of using 1 gi-am
of quassiiji to 2,000 cubic centimeters of water, 0.4 gram Avas used
to 2,000 cubic centimeters of water.

During the early part (^f the work it was discovered that the whale-
oil soap, even when used at the greatest dilution at which it had any
spreading effect (1 pound to 100 gallons), Idlled a certain percentage
of the aphides. Since a spreader is necessary, experiments wore
inaugurated to find one that would have no effect upon the insects
treated. It was found that the soap bark solution which was being
used iji some other work was an excellent spreader and did not affect
the insects in the least. In all of the following experiments a water
decoction of this material was used at the rate of 2 pounds of soap
bark to 100 gallons of water.

In applying the solutions, a compressed-air spiay machine (fig.
1) which maintained 50 pounds pressure and handled as small an
amount as 200 cubic centimeters was used. A fine mist nozzle was
so adjusted to this pressure of 50 pounds that a washing rather than
a mist spray was produced.

In conducting the experiments detailed in Table II prune twigs
infested by the hop aphis (Pliorodon liunmli Schrank) and the prune
aphis (Hyalopterus prinii Fab.) were brought from the field and,
after being sprayed with the solutions, were set in moist sand.
By placing the pots of sand containing the sprayed twigs on sheets
of paper the percentage of the insects that were killed by the solu-
tions were readily obtained. Check twigs were kept to make sure
that there was not a marked mortality from some other cause.

Table II gives the results of the spraying experiments with quassiin
in aqueous solution and also i_n solutions of certain alkaline sub-
stances.

Table 11. — Results of experiments with quassiin as a contact iywecticide .

SERIES NO. 1. WITH SOAP BARK IN LABORATORY.

Formula.

0.4 prams to 3,000 cp
0.4 1,'rams to 2,000 cc

Number of
aphides
sprayed .

904

S, OGO

0.4 grams to 1,800 cc ! •• ^5!'

0.4 Krams to l.-'iOO cc , '••'-"

0.4 grams to 1,000 cc L 'SSI

Per cent of
aphides'
iillod.

8.5.1
9.3. 02
94.6
93.9

99.7

SERIES NO. 2. WITH WHALE-OIL SOAP IN FIELD.

0.4 jrrams to 2,000 cc.
0.4!'rams to 1,800 cc.
0.4 grams to l,.50O cc.

99.4
99.8
99.8

•

QUASSIIN AS A CONTACT INSECTICIDE.

Table II.— Results of experiments with quassiin as a contact insecticide — ("ontinued.
SERIES NO. 3. WITH SOAP BARK ON PRUNE APHIS IN FIELD.

Formula.

Number of
aphides
sprayed.

Per cent of
aphides
killed.

0.4 prams to 2,000 (*c .*

1,92.'5
721

97 5

0.4 grams to 1,800 ce

CHECK SERIES.

Whale-oil soap, 3 poiinds to 100 gallons

1,030

1,202

930

1 2S4 6

Soap bark, 2 pounds to 100 gallons

1 '>i

Nicotine sulphate, 0.4 grams to 2,000 cc. , wth soap bark, 2 pounds to 100 gallons . .

96.9

1 These were the largest percentages obtained for the check materials.

2 In field.

From the foregoing table it w411 be readily seen that quassiin used
at the rate of 0.4 grams to 2,000 cubic centimeters, or 6^ ounces of
40 per cent solution to 100 gallons, was almost as effective against the
hop aphis and the prune aphis as nicotine sulphate, 0.4 grams to
2,000 cubic centimeters, or 6^ ounces to 100 gallons. The difference
is approximately 3 per cent, while quassim, 0.4 grams to 1,000 cubic
centimeters, is fully as effective.

The writer has not so far tested this material upon insects other
than those mentioned, but believes that it will jjrove effective else-
where if used in proportions corresponding to the amounts of nicotine
sulphate that are known to be effective.

CONCLUSION.

Picrasma excdsa Swz. (quassia wood) is a native of Jamaica, and,
according to data obtained, is available in considerable quantities.

The percentage of quassiin in the quassia wood varies somewhat,
and does not appear to be definitely knowai. Supposing it to be 0.75
per cent, as given by one author, to use the quassim at an effective
rate of 0.4 grams to 2,000 cubic centimeters, it would take only 1^
pounds of the chips to 100 gallons of spray. To be on the safe side,
double the amount of chips calculated to be necessary, and we have
the following formula ^ and cost per 100 gallons of spray:

Quassia chips, 0.75 per cent quassiin, 3 pounds, at $0.04 $0. 12

Whale-oil soap, 3 pounds, at ?0.04 12

Total cost of materials per 100 gallons 24

Quassiin can be readily extracted from quassia wood, Picrasma
^'xceZso. Swz., in a comparatively pure form. (See p. 3.) It probably
could be more cheaply extracted in an impure water-soluble form b}-
using sodium carbonate solution. The percentage of quassim could
be determined and the material evaporated until a standardized solu-
tion was made. Such a material could be diluted and used with

1 This formula corresponds very closely to formula No. 1, page 2.

8 BULLETIN 165, U. S. DE 'ARTMENT OF AGRICULTURE.

whale-oil soap, or some other spreader, as in the case of nicotine sul-
phate. The writer believes that quassiin has possibilities as a com-
mercial insecticide and that it could be cheaply prepared and
possibly sold at a lower price uhan some of. the materials that are
now on the market.

The foregoing data were o])tained under conditions existing at
Sacramento, Cal., and may not hold for a more humid chmate. The
efficiency of the quassiin should be determined for some other locality
before a commercial recommendation is made.

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OF THIS PUBLICATION MAY BE PROCURED FROM

THE SUPERINTENDENT OF DOCUMENTS

GOVERNMENT PRINTING OFFICE

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V

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1914

BULLETIN OF THE

D

No. 167

Contribution from the Bureau of Entomology, L. O. Howard, Chief.
February 10, 1915.

(PROFESSIONAL PAPER.)

PARA-DICHLOROBENZENE AS AN INSECT
FUMIGANT.

By A. B. DucKETT,
Scientific Assistant, Truck Crop and Stored Product Insect Investigations.

INTRODUCTION.

The purpose of the following pages is to determine the insecticidal
value of para-dichlorobenzene as a fumigant, as well as to ascertain
the injury, if any, to cloth fabrics and the effects of the vapors on
plant life as well as upon the germination of seeds.

Para-dichlorobenzene is a definite chemical compound, known for
many years, but only recently used as an insecticide. It is a color-
less, crystalline substance which volatiHzes very readily as a colorless
vapor with a peculiar ether-like odor. The vapor is harmless to
human beings and domestic animals under ordinary conditions, but
in many instances it is a specific poison for insects. It has an addi-
tional advantage over the many other fumigants in that the odor
does not cUng to fabrics, etc., the characteristic ether-hke smeU
rapidly disappearing upon exposure of the fumigated substances
to the open air. Probably the greatest advantages that para-
dichlorobenzene possesses over other fumigants are its absolute
noninflammability and its comparatively low cost of purchase and
application in proportion to the result obtained.

EFFECTS OF INHALATION OF THE VAPOR.

As stated, para-dichlorobenzene possesses only a weak ether-like
smell, which, owing to the volatile nature of the substance, will pass
off in a few hours if exposed to the air. Dr. Curschman, at the
Greppin Works in Germany, concludes from a series of experiments
that para-dichlorobenzene, when used as an exterminator for moths,
etc., is virtually harmless to human beings, perhaps even superior
to naphthalene in this respect. He goes further by stating that
poisoning by para-dichlorobenzene to human beings through contact
with the skin is impossible and that inhalation of the vapors of this
product is perfectly harmless. According to liim, para-dichloro-

71117°— BuU. 167— 15

2 BULLETIN 167, U. S. DEPARTMENT OP' AGRICULTURE.

benzene is harmful to human beings only in cases of internal applica-
tion of large quantil ,s, say from 30 to 40 grains.

It is not advisable for sensitive persons to remain for a long time
in a closed room where para-dichlorobenzene is freely exposed, as the
odor may cause annoyance. On the other hand, para-dichloro-
benzene can be used in closed or occasionally opened cupboards and
even in sitting rooms without causing any inconvenience whatsoever.

PARA-DICHLOROBENZENE AS AN INSECTICIDE.

Experiments were conducted by the writer with para-dichloro-
benzene to ascertain the practicability of its use and its insecticidal
value' against various insects. Para-dichlorobenzene as an insec-
ticide is applicable to a large variety of insects, but under certain
conditions depending on the variations in life history and environ-
ment, and therefore necessitating specific methods of appUcation.

In a general way para-dichlorobenzene is effective only where its
vapors can be closely confined, and when used in a higher tempera-
ture than 74° F.; furthermore, it is recommended only where poison
bait and contact sprays are either impractical or undesirable. The
vapor is diffused through the air very rapidly and must, therefore;
be closely confuied in order to maintain a sufficient proportion in the
air to prove fatal to insect Ufe.

The amount of material required, under ordinary conditions, to
bring about the desired effect is about 12 ounces of paia-dichloro-
benzene to every 100 cubic feet of space. The v/riter, liowever,
suggests the use of a larger amount, 1 pound to 100 cubic feet, which
will take effect more quickly and diminish the chances of revival,
although revival is aberrent. At temperatures between 75° and 85°
F. an exposure of at least 36 hours is necessary for best results.
Temperatures above 85° F. require only 24 hours exposure, due to the
fact that heat facilitates the diffusion of the vapors.

Most warehouses and repositories contain several species of insects
which possess very great tenacity of Ufe, either in the adult or larval
stages. In view of the fact that unless para-dichlorobenzene is used
in enormous quantities or is permitted to remain in the respository
over 48 hours, it does not injure plant hfe or render fruit, etc., inedible,
we should, by preference, use as large a dose as possible for the com-
plete eradication of the insects in the shortest possible time. As
generally employed, the time would vary inversely to the amount of
para-dichlorobenzene used. Since this substance is comparatively
cheap and all unvolatilized material can be kept indefinitely, with
very slight deterioration if the proper precautions are exercised, the
additional amount of material required for a larger dose would be an
insignificant item. Para-dichlorobenzene is insoluble in water and
does not deliquesce when exposed to the air, but completely volatil-
izes, and should therefore be kept in an air tight can or glass jar.

PARA-DICHLOROBEXZENE AS AN INSECT FUMIGANT, 3

DIFFUSION OF THE VAPOR.

Para-dichlorobenzene is very volatile and tbi^^apor is extremely
heavy, being more than five times that of an equal volume of air and
more than twice as heavy as carbon bisulphid vapor. Although it
diffuses quite rapidly through the air, as evidenced by the perception
of its odor, the vapors will, like carbon bisulphid, tend to work
rapidly downward, outward, and eventually upward. From the fore-
going fact it is ascertained that the greater density of vapor is at the
lower levels. This property is obviously very beneficial when para-
dichlorobenzene is used as a fumigant for bags of grain, stored
products, carpets, and rugs, and in all cases where it is desirable to use
a gas that will penetrate the lowest levels and force its way into
cracks and crevices in floors, walls, and similar locations.

DIRECTIONS FOR USING.

Para-dichlorobenzene is applied in most instances in the same
manner as camphor and naphthalene. It is not, however, necessary
to sprinkle it around in corners or over rugs and other material, as is
often the case wdth camphor and naphthalene, but merely to expose a
sufficient quantity in one or two open or partially open receptacles,
placed over, or higher, than the infested cases, goods, and material
which require fumigation.

HOW PUT UP AND COST.

Para-dichlorobenzene at the present time is sold in 5, 10, 25, 50,
and 100 pound iind barrel lots, the prices for which are as follows:

23 cents per pound, in 5, 10, and 25 pound lots.
18 cents per pound, in 50-pound lots.
17 cents per pound, in 100-pound lots.
15 cents per pound, in barrel lots.

If any considerable quantity is to be used, it is much better to
purchase of some wholesale druggist or direct from the manufacturers.

APPLICABILITY TO VARIOUS INSECTS.

Para-dichlorobenzene is applicable to many insect pests living
under various conditions and environment, and therefore requires
specific methods of application, and, unlike carbon bisulphid, it is at
the present time used only indoors and in other places where its
vapors can be closely confined. As there is a great variation in the
tenacity of Ufe among insects, the existing conditions should be care-
fully noted before para-dichlorobenzene is applied.

Beetles, such as the rice weevil (Calandra oryza L.), granary weevil

(Calandra granaria L.), the confused flour beetle (Triholium con-

fusurn Duv.), the cadelle {Tcnehvides mauritanicus L.), the yellow

4 BULLETIN 167, U. S. DEPARTMENT OF AGRICULTURE.

mealworm (Tenehrio molitor L.), and a few others less common are
particularly hard to kill when in the adult stage. The larvae of the
mealworms, Tenehrio molitor h., Tenebrio ohscurus L., and closely
alhed species, are likewise found by experiment to possess great
tenacity of life. It is therefore recommended that a proportionately
larger amount of para-dichlorobenzene be used when combating these
species. Moths, fhes, roaches, ants, and aphides are readily killed
by para-dichlorobenzene when used in the ordinary strength recom-
mended under the heading "Para-dichlorobenzene as an insecticide."

The action of para-dichlorobenzene on insects is primarily upon
their nervous systems. This property is readily manifested when a
moth is exposed to the vapors for a few seconds. It first displays
great excitement and uneasiness, followed closely by spasmodic con-
vulsions, and finally turns ever on its back. \Miile in this position
violent nervous and muscular reflex action is noticed until life is
extinct.

The moths on which this gas has been tested include the Angoumois
grain moth (Sitotroga ceredlella Oliv.), Mediterranean flour moth
(Ephestia Jcuehniella ZelL), Indian meal moth (Plodia interpunctella
Hbn.), meal snout moth (Py rails farinalis L.), and the case-bearing
clothes-moth (Tinea pellionella L.).

EXPERIMENTS WITH PARA-DICHLOROBENZENE AS A FUMIGANT.

During the spring of 1914, while stationed at Washington, D. C,
the writer, working under the direction of Dr. F. H. Chittenden, per-
formed a series of experiments with para-dichlorobenzene as a fumi-
gant for stored-product insects. The chemical was first used on a smaU
scale, and results were afterwards checked up in a specially con-
structed air-tight fumigatmg box having a capacity of 100 cubic feet
(PI. I.) The average temperature was comptited from the records of
a thermograph placed in the box, and the para-dichlorobenzene
exposed in shallow -piepans or the tops of 5-gallon lard cans, since
these shallow receptacles present a much larger surface of the chemical
for evaporation. These pans were placed about 4 feet above the
material to be fumigated, which was contained in muslin bags of
variable capacity (see PI. II) and which had previously been ascer-
tamed to be free from live insects. Into this material, consisting of
wheat, cornmeal, flour, rice, and other cereals, were then introduced
living uisects, the number and species of each being recorded on an
attached tag.

The respective amounts of })ara-dichlorobenzene used in each
experiment and the tabulated results follow.

Bui. 167, U. S. Dept. of Agriculture.

Plate I.

mmmfmm^mmfmu^^

FUMIGATI

NG BUA U6b0 IN EXPERIMENTS WITH PARA-DICHLOROBENZENE. (ORIGINAL.,

Bui. 1 67, U. S. Dept. of Agriculture.

Plate II.

Bags Containing InfestedGrain Ready to be Fumigated with PARA-oicHLORObENZENE.

(Original.)

PARA-DICHLOKOBENZENE AS AN INSECT FUMIGANT. $

Experiments with para-dichlorobemene as afumigant.

Experiment
No. and date.

Insects introduced.

Aver-
age
temper-
ature.

Length
expo-
sure.

Date
exam-
ined.

Para-
dichloro-
benzene

used.

Per

cent

killed.

Remarks.

°F.

Hours.

No. 1, Mar. 25,

Tribolium confusum

52

72

Apr. 1

1 ounce .

None.

All revived. I're-

1914.

Duv.; T.ferrugineum
Fab. ; Calandra oryza

lin»inary ttest.
Temperature
too low. Va-

L.; C. granaria L.;

Silvunus surinamen-

pors diffused

sisL.; Rhizopertha

very slowly.

dominica Fab.;

Eggs, larvae,

Laemophloeus m i-

pupa;, and

nutus 01iy.;Tenebrio

adults used in

molitor L. ; Sitotroga

the case of

cerealella Oliy.; Plo-

Ephestia kueh-

dia ijiterpunctella

niella and Plo-

Hbn.; E phes t ia

dia interpimo-

kuehniella Zell.

tella. Capacity
of fumigating
box used, T
cubic feet.

No. 2, Apr. 7,

Same as in experiment

59

96

Apr. 13

8" ounces.

None.

All revived. Pre-

1914.

No. 1.

liminary test.
Temperatura
too low. Fumi-
gating box
used, 7 cubic
feet.

No. 3, Apr. 18,

Same as in experiment

65

96

Apr. 25

8 ounces.

20

Unsatisfactory.

1914.

No. 1.

Preliminary
test. Fumigat-
ing box used, T
cubic feet

No. 4, Apr. 28,

Tribolium confusum

81

24

May 5

2 poimds

100

IpO cubic feet

1914.

Duy.; T.ferrugineum
Fab. ; Calandra oryza
L.; C. granaria L.;
Silvanus surinamen-
sis L.; Rhizopertha
dominica Fab. ; Sit(>
troga cerealella Oliv.;
Plodia Interpimc-
tellaHbn.; Ephestia
kuehniella Zell.;
(Bruchus) Pachy-
merus 4-maculatus
Fab.

fumigating box
used for this
experiment.

No. 5, Apr. 29,
1914.

Roaches

80

24

May 2

2 ounces.

100

5 cubic feet fumi-

gating jar used.

No. 6, May 1,

Mites on corn

78

28

May 5

2 ounces.

100

5 cubic feet fumi-

1914.

gating jar used.

No. 7, May 4,

Slugs, snails, sowbugs.

82

36

May 9

2 poimds

100

100 cubic feet fu-

1914.

millipedes, ants.

migating box
used.
100 cubic feet

No. 8, May 11,

Tribolium confusum

86

24

May 1(1

2 poimds

100

1914.

Duv.; Calandra ory-

fumigating box
used in this

za L.; Silvanus sur-

inamensis h.; Sito-

experiment.

troga cerealella Oliv. ;

Four bricks

Plodia interpunc-

were heated to

tella Hbn.; Ephestia

a high temper-

kuehniella Zell.;

at ure and

Laemophloeus minu-

placed in box

tus Oliv.; Tenebrio

in order to ol>-

molitor L.

tain higher
temperature.
Unsatisfactory.

No. 9, May 14,

Same as in experiment

73

24

May 20

2 pounds

70

1914.

No. 8.

Tempera t u r o
too low.

No. 10, May 15,
1914.

Flies

81

20

May 16

8 ounces.

100

100 cubic feet

space.

No. 11, May 18,

Aphides

80

■ 20

May 19

8 ounces.

100

100 cubio feet

1914.

space.

No. 12. May 19, 1914, 4 ounces of finely ground para-dichlorobenzene were sprinkled over pieces of
woolen cloth and placed in a 100-cubic-foot fumigating box for a period of 24 hours, at an average tempera-
ture of 76° F. Upon examination it was discovered that the fine crystals adhered to the lint of the wool
but were readily brushed off with a whisk broom. After two hours' exposure in the open air the odor of
para-dichlorobenzene was barely perceptible.

No. 13. May 20, 1914, a test on the germination of seed was made. One pint of Argentine com. about
half of which had previously sprouted, was put in a 7-inch flower pot containing 4 inches of molsi fertile
soil. The pot was then introduced into a 100-cubic-foot fumigating box and exposed to the vapors of par»-

6 BULLETIN 167, U. S. DEPARTMENT OF AGRICULTURE,

dichlorobenzene for 24 hours at an average temperature of 79° F. Two days later the seed was examined
and showed no material injury from the experiment, sprouting about as usual.

Note. — Preliminary experiments with para-dichlorobenzene have been conducted along the following
lines: 1. Para-dichlorobenzene introduced into insect collection boxes for the eradication of museum pests.
2. Para-dichlorobenzene in combination with formaldehyde and potassium permanganate as an insecticide
and germicide. 3. Para-dichlorobenzene made into a paste by adding parainn and resin in the presence
of heat, as a substitute for grafting wax. The above paste to be applied in the burrows of borers in shade
trees. 4. Further experiments on the effect of para-dichlorobenzene, if any, on tender plants. 5. The
effects, if any, of para-dichlorobenzene on animals, when taken internally in small doses. In these experi-
ments green food, such as kale, cabbage, and clover, were put in a jar heavily charged with para-dichloro-
Ijenzene vapors and fed twice daily to herbivorous animals, such as rabbits and guinea-pius. In these
expcHments the writer has not as yet reached any definite conclusions, and therefore reserves their pub-
lication until further experiments along these lines are completed.

CONCLUSION.

From the foregoing observations and experiments the writer
concludes that para-dichlorobenzene, used as directed in the preceding
pages, acts as an excellent fundgant against the following insects:

(1) Stored-product insects.

(2) Case-bearing clothes moths.

(3) Roaches and ants. ^

(4) Museum pests.

(5) Miscellaneous house insects, including flies, carpet beetles or buffalo

moths, book lice, silverfish, mosquitoes, centipedes, and miscellaneous
larder insects.

It is also an effective substitute for potassium cyanid in collecting
bottles.

CHEMICAL AND PHYSICAL PROPERTIES OF PARA-DICHLOROBENZENE.

At the request of Dr. Chittenden the following data were kindly
furnished by the Insecticide and Fungicide I^aboratory, Miscella-
neous Division, Bureau of Chemistry:

We have made an examination of the sample of dichlorobenzene submitted by you
for examination on December 22, 1913, and find that this product is practically pure
para-dichlorobenzene (CgH4Cl2). We have looked up some references in the litera-
ture in regard to this substance and give you the following information based thereon:

Dichlorobenzene is a product derived from benzene by the replacement of two of
the hydrogen atoms by chlorine. There are three dichlorobenzenes, designated
«rtbo, meta, and para, the structural formulas of which are:

.,0^ -5t

^'

.-^

.,^

H H Cl

ORTHO META PARA

All three have the empirical formula C6H4CI2. Ortho and meta dichlorobenzenes
are liquids, the former boiling at 179° C. and the latter at 172° C.

Beilstein, in his Handbuch der organischen Chemie, III Auflage, 1896, Band II,
page 44, gives three methods for the preparation of para-dichlorobenzene (in the
German, p-dichlorbenzol): -*

PAKA-DICHLOROBEXZENE A.S AN INSECT FUMKiANT. 7

(1) By the action of rhloriue on benzene (CoTIe) in tlie presence of iodine. A littl«
ortho-dichlorobenzene is also formed in this reaction.

(2) By the action of phosphorus pentachlorid on para-chlorophenol.

(3) By the action of phosphorus pentachlorid on para-phenolsulphonic acid.

He gives the melting point of this compound as 53° C. (127.4° F.) and its boiling
point as 172° C. (341.6° F.), but quotes Mills (Phil. Mag. (5) 14, 27) as giving 52.72° C.
for the melting point.

Para-dichlorobenzene crystallizes from alcohol in monoclinic leaves, it sublimes, at
ordinary temperatures, is soluble in hot alcohol in all proportions, and is easily solu-
ble in ether, benzene, carbon bisulphid, etc.

In regard to physiological properties, Francis and Fortescue-Brickdale ' state:

The benzene halogen derivatives have a slight odor, are insoluble in water, vola-
tilize without decomposition, and are very stable. * * * Corresponding to their
stability it is found that the halogen is not split off in the organism, and that they
do not show hypnotic properties. With the entrance of chlorine the antiseptic prop-
erties increase * * * Chlorbenzene acts on the spinal cord to a greater extent
than benzene.

The following figures in regard to para-dichlorobenzene are from calculations made
by R. C. Roark:

Molecular weight 146.952

Density of the vapor 4.592 if oxygen equals 1.

72.892 if •hydrogen equals 1.
5.1025 if air equals 1, assuming the mo-
lecular weight of air to be 28.8.

In other words, assuming no dissociation or association, a given volume of para-
dichlorobenzene in the form of a vapor would be 5.1025 times as hea^^ as an equal
volume of air at the same temperature and at the same barometric pressure.

The vapor of para-dichlorobenzene will flash at about 70° C. (158° F.), but even
when held in a very hot flame and ignited the substance will not continue to burn
after the flame is removed. Thus the substance is not combustible, biit is decora-
posed by heat into substances which partially burn vnih copious deposition of soot
when directly in a flame.

As the vapor pressure of para-dichlorobenzene has never been determined, it ia
impossible to state how much of its vapor air at any temperature short of 172° C.
(341.6° F., its boiling point) would take up. At 172° C. (341.6° F.), barometer 760
mm., 1 liter of para-dichlorobenzene gas would weigh 4.0257 grams, or 1 cubic foot
would weigh 4.0208 avoirdupois ounces.

' Francis, Francis, and Fortescue-Brickdale, J. M. The Chemical Basis of Pharmacology, p. 99,
London, 190S.

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OF THIS PUBLICATION M.VT BE PROCrRED FROM

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BULLETIN ^'

'THE

Contribution from the Bureau of Entomology, L. O. Howard, Chief.
February 9, 1915.

THE EUROPEAN PINESHOOT MOTH; A SERIOUS
MENACE TO PINE TIMBER IN AMERICA.

By August Busck,
Entomological Assistant, Forest Insect Investigations.

INTRODUCTION.

One of the most injurious insects to pine forests in Europe is a
small orange-red moth, the larva of which eats out the new buds
and kills or deforms the young twigs of pine trees, so as seriously'
and permanently to lower their timber value. This European pine-
shoot moth, which is known under the scientific name Evetria huoliana
Schiffermiller, has within very recent years been accidently intro-
duced into America on imported European pine seedlings and has.
unfortunately become established in several widely separated locali-
ties in the eastern and middle western States.

Early last summer (1914), a correspondent of the Bureau of
Entomology complained of a serious insect injury to European pines
under his surveillance on Long Island, and sent examples of the
injury and of the larva? causing it; the latter could not be identified
as those of any of our known American pine pests, and the writer
was therefore authorized to visit the affected localities in order ta
ascertain the extent of the injury and to obtain sufficient live ma-
terial for study and rearing. From this material a large number of
moths emerged during the latter part of June and these were at once
recognized as the famous European pine-shoot moth.

Subsequent surveys, undertaken by the bureau through Mr. Carl
Heinrich and the writer, established the fact that the species has been
repeatedly introduced on European nursery stock, and that it has be-
come established in nurseries and parks in several localities scattered
over nine States.

In view of the experience with other introduced European insects,
and considering the very serious financial loss caused abroad annually
by this insect, its introduction into this country gives just cause for
alarm, because incalculable injury may result to the vast American
forest interests if this insect is permitted to become generally estab-
lished on our native pines.

71551°— 15

2 BULLETIN 170, U. S. DEPARTMENT OF AGRICULTUEE.

Some idea of the extent and permanent character of the injury
which this insect is capable of inflicting may be gained from the
illustration (PI. I) of a European pine forest which has been infested
by it for several years in succession, with the result that a majority
of the tree trunks are so twisted and crooked that their value as tim-
ber is materially lessened.

HISTORY OF THE SPECIES IN EUROPE.

The species is a constant menace to pine forests in Europe and an-
nually causes serious depredations, especially to young plantations
of pine, in spite of continual preventive work against it. It has been
the subject of much study and of an extensive literature from the
time it was first described by Schiffermiller in 1776 to the present
day. The species was named in honor of a Vienna entomologist,
Baron Buol, who studied its injurious work during the latter part of
the eighteenth century ; since then numerous accounts have appeared
of particularly severe outbreaks in many parts of Europe, from
England to Russia, and from Scandinavia to southern France. It
also occurs in Siberia.

One such outbreak in Denmark, in 1805-1807, is recorded by Nie-
mann (1809).^ This was so serious as nearly to cause pine culture to
be abandoned in that country as hopeless. It is interesting to note
that at that time the same preventive means were resorted to as are
now employed against the insect, namely, the wholesale pruning and
burning of all infested twigs.

The German forest entomologist, Eatzeburg, counted Evetria
huoliana one of the most injurious forest insects and gave a detailed
account (1840) of the life history, structure, and economic impor-
tance of the species. He mentioned especially an unusual outbreak in
1836-1838, which covered many parts of Europe. In the province of
Furstenau the Rochesberg Mountain, which was covered with pines,
became so seriously infested that it was under consideration by the
authorities to burn it off and plant new trees. Other localities were
only saved by strenuous systematic collecting of the infested twigs;
thus, in the small province of Kesternich alone, 150,000 larvae were
gathered and destroyed.

Judeich and Nitsche (1895) state that the injury caused by Evetria
huoliana is often fatal to the pine plantations. To quote from these
authors, " If the attack is slight, it results in the branching of the
tree, but if the attack is more severe and continued for several years,
as we have seen it, then hardly any bud is spared and the pines
become stunted into miserable small bushes from which numerous

^ Dates in parentheses refer to " Literature," pp. 10-11.

THE EUROPEAN PIKE-SHOOT MOTH, 3

branched shoots and large needle tufts stick out." These authors
record many severe outbreaks and mention especially one in 1883-
1885, in the Royal Forest Eeserve, Pillnitz in Saxony, where nearly
75 acres of young pines planted in 1878 became infested to such an
extent that hardly a shoot was spared, and in 1884 the entire planta-
tion presented a pitiful, crippled appearance.

J. E. V. Boas (1898), who has made original investigations of the
insect in Denmark, considers it one of the most injurious insects
affecting forest trees. Among other outbreaks he mentions one in
Jutland, Denmark, extending through several years around 1870,
which " threatened the total destruction of the pine plantations."

The Belgian authority on forest insects, G. Severin (1901), regards
Ei'etria huolicma as the most Injurious insect to pines in Europe, and
emphasizes the lasting injury to the timber resulting from even
slight attacks of this insect.

All other European handbooks on entomology or on forestry con-
tain similar accounts of this insect and express the same opinion as
to its destructiveness to pine.

FOOD PLANTS.

Evetrla huoliana is confined to pine and does not attack other
coniferous trees, as spruce or larch, even though these grow along-
side of the infested pines. While the species is most often men-
tioned on the yellow pine, or Scotch pine,^ in Europe, because this is
preeminently the forest tree of importance there, it attacks all species
of Pinus indiscriminately, according to Eatzeburg and other authori-
ties, and the American infestations have come in on European seed-
lings of the Austrian pine - and on mughus pine ^ quite as often as on
Scotch pine.

According to Eatzeburg and Severin, it also attacks and is equally
injurious to American white pine,* which is cultivated in Europe;
and Mr. Carl Heinrich found the species on a small lot of another
native American pine,"' which was growing immediately surrounded
by infested European pine seedlings.

These latter records are particularly significant, as they prove be-
yond question that the pest will spread to our native American pines
if not prevented.

The species attacks mainly young trees between 6 and 15 years of
age, but it is often excessively destructive to younger plantings and
seedlings and injurious also to older trees, though trees of 30 years
or older are rarely seriously affected.

1 Pinus sylvestris. * Pinus strobus.

"Pinus laricis var. austriaca. ^ Pinus resinosa.

^ Pinus montana var. mughus.

4 BULLETIN 170, U. S. DEPARTMENT OF AGEICULTURE,

INTRODUCTION AND DISTRIBUTION IN AMERICA.

American nurseries have imported many thousands of pine seed-
lings annually from Europe, especially from France, Belgium, Hol-
land, Germany, and England. Importations normally take place
in the fall, winter, and early spring. At this time of the year the
yoimg larvae of the pine moth lie dormant within the buds, so that
an infestation is easily overlooked. It is evident that the pest has
been present in a number of shipments of late years and that it thus
has been introduced repeatedly into American nurseries. In a great
majority of these cases, however, the species has been unable to estab-
lish itself and has died out during the first year. Many of the
larvae die from overheating en route, or from various other unfavor-
able circumstances incident to the handling and transplanting of the
seedlings under different climatic conditions. Only by a combina-
tion of favorable conditions would the few surviving larvse have been
able to develop into moths and succeed in establishing the species in
this country. This is probably the reason why the species as yet has
become established in comparatively few American localities. It
appears that such established infestation has taken place only in very
recent years and especially within the last two years, or since the
demand for European pines has become general.

Up to the present time the European pine moth has been dis-
covered in only 32 nurseries and private estates, representing 20
localities in 9 States, namely :

I

state.

Locality.

Discovered in-

Illinois

Chicago

Private grounds.
One nursery.
Do.

Do

Do

Dundee

Do

Do.

Do

Deerfleld

Do.

Do

Kenilworth

Two private grounds.

Do

One nursery.'
Do.

Ohio

Tippecanoe City

Elm Grove

Do.

ppnnsylvflTiia

Pittsburgh

Private grounds.
One nursery.

Do

Somerville

New Yorli

Long Island..

Do

Tarrytown

One nursery and one estate.

Do

Massachusetts..

Dedham .

One nursery.
Do.

Do

Do

Worcester

Do.

Connecticut. .

New Canaan

Do.

Rhode Island

Newport

Two nurseries and one estate.

In none of these localities, except on Long Island, has the species
existed for more than the last two years, and in most of them it has
become established only within the last year.

But the survey for this insect has so far covered only about 60
localities, which could be reasonably suspected to harbor the pest
because it was known that importations of European seedlings had

Bui. 170, U. S. Dept. of Agriculture.

Plate I.

Work of the European Pine-Shoot Moth vEvetuia bjc

)L1ANA).

Section of European pine forest showing- deformations in the trunk of Pinus t^ijlfcstris
resulting from several consecutive years' injury. (After G. Severin.)

Bui. 170, U. S. Dept. of Agriculture.

Plate II.

Stages of the European Pine-Shoot Moth.

Moth and full-grown Inrva; both greatly enlarged. (Original.')
[Drawing.s by Miss Mary Carmody.]

j|. 170, U. S. Dept. of Agricultur

Plate III.

Bui. 170, U. S. Dept. of Agriculture

Plate IV.

Work of the European Pine-Shoot Moth.

Malformations in pine resulting from injury by this pest. (Original.)

3ul. 170, U. S. Dept. of Agriculture.

Plate V.

CO g

z ^

o ;j

Bu

, 170, U. S. Dept. of Agr

culture.

_

^m^^^m

Plate VI.

14

^H&^V,:^

yWS^^

25*

; ^«^'i

'^' ^9H

-^^g^

^2^^^

..4

^^rJ

*f;^

-^fc

w^

m

^"V^"*

^

^

!. ■

a. X >

Q- !>. £

§ S' ^

THE EUEOPEAN PUSTE-SHOOT MOTH. 5

taken place, and the indications are very strong that the pest has be-
come established in several other widely distributed localities, either
by direct importation from Europe or by distribution from infested
American nurseries. This is particularly to be suspected of locali-
ties where large importations and plantings of European pines have
been made.

As yet the pest has been found only in nurseries and private parks
supplied by these infested nurseries. In no case has it yet been
found on forest trees in America. The species is therefore at present
mainly a nursery problem in this country and consequently may yet
be controlled and possibly even eliminated by proper measures under
Federal and State supervision. That this condition can not long
endure and that the pest,, if not checked, will soon multiply and
spread to native pines outside of nurseries and pass beyond the pos-
sibility of elimination is clearly indicated by all the evidence on

hand.

LIFE HISTORY.

In Europe the moths (PI. II, upper figure) issue in July, some-
times as early as the end of June, and in the warm evenings they
swarm around the pines in large numbers. During the clay they sit
quietly on the branches, as can be ascertained by giving the tree a
sharp jolt, which will cause the moths to fly out. When the insect sits
still on the food plant it is not easily discovered, for the apparently
striking orange-red color blends well with the natural surroundings
and therefore must be classed as a protective coloration. Early in
August the eggs are laid singly on the new buds for next year's
growth, the terminal cluster of buds being nearly always chosen for
oviposition. The young larva soon hatches and eats its way into the
bud, making itself a roomy cell by devouring the live inside part. It
attains a length of only a few millimeters during the fall months, and
overwinters within the hollow bud. At this stage its presence is
easily overlooked, though a trained eye will discover a small exuda-
tion of pitch over the entrance hole differing from the normal exuda-
tion of the buds. (See PI. III.)

In May, as soon as the sap begins to rise in the trees, the larva
the buds. (See PL III.)

leaves its winter quarters and bores into the bud next thereto, in
turn destroying this and as many others as it needs for food. As
the remaining buds adjoining begin to grow into young shoots the
larva attacks them. It eats the entire inside of the youngest shoots
and these consequently die. The more developed shoots are injured
only on one side, and these sometimes continue to grow, but are bent
downward at the injured spot. The larva (PL II, lower figure) feeds
only on the soft growth on which the needles have not yet appeared,
and by the time the needles have developed all, or nearly all, of the
shoots in the infested cluster have become dead or injured. The

6 BULLETIN 110, U. S. DEPARTMENT OF AGRICULTURE.

larva then makes a silk-lined chamber within one of the hollow
shoots and here it pupates. After about three weeks the spiny pupa
pushes itself half way out through the dry wall of its chamber and
the moth, or adult, issues.

The full life history of the species in America has not been ascer-
tained, because a full year has not elapsed since it was first dis-
covered here. "\^'liile in the main it is the same as in Europe, a very
distinct difference has already been noticed, due to the longer and
warmer summer and fall in this country. In Europe the young larva
attacks only one bud and attains very little growth before it enters
the dormant winter season, but in the warmer climate of America
the larva eats out two, three, or more buds and attains nearly half
of its growth before winter. This, of coiu^se, tends to make the
species even more injurious here than it is in Europe.

Wliile it is altogether probable that the species has here only one
generation annually, as in Europe, the possibility is not absolutely
excluded that on account of the longer season it may eventually de-
velop two generations annually like the allied native species. This,
of course, would greatly increase its power for injury.

CHARACTER OF INJURY.

During the entire spring the infested twigs are very noticeable by
reason of the dead and inj ured buds and young shoots, and the empty
pupa skin sticking out of the destroyed shoot is also a familiar and
easily noticed sight during the summer months ; but the extent of the
injury caused by this insect is only realized later in the season,
when the new growth is found to be either quite destroyed or perma-
nently injured.

As may be gathered from the foregoing account of the life history,
each one of these insects does very considerable damage, not only by
destroying a large number of buds and young shoots but by injuring
the adjoining shoots which remain and which normally should sup-
plant the destroyed leaders ; thus the trees are permanently disfigured.
These injured shoots bend dowmvard and outward and afterwards
grow upward again in a curve, in the attempt to continue the normal
upward growth of the tree. This results in a characteristic malfor-
mation (Pis. IV, V, VI), so familiar in European pine forests that it
has a popular name in each country — as " posthorn" and " waldhorn "
in Germany and Holland and " baionnette " in France, while the few
examples which have so far occurred in America have suggested the
name " Dutch pipe " to those who have noticed it. This injury does
straighten out somewhat during the successive years' growth, but
never can be fully remedied and will always be noticeable and a seri-
ous detriment to the timber (PI. I). Injury of this character is the
result even when the Species is present in only small numbers, the

THE EUKOPEAN PINE-SHOOT MOTH. 7

repeated infestation of the leading twigs during several consecutive
seasons producing additional malformations which result in a much
distorted tree of little commercial value. If the pest becomes more
abundant, then the trees are transformed by the effect of the injury
into unsightly crippled bushes with no commercial value.

DESCRIPTION.

, THE ADULT.

(PI. II, upper figure.)

The European pine-shoot moth is a small, gayly colored moth,
about one-half inch long and measuring about three-fourths of an
inch across wdth the wings extended. The head and its appendages
and the thorax are light orange-yellow, and the abdomen is dark gray.
The forewings are bright ferruginous orange, suffused with dark
red, especially toward the tips, and with several irregular, forked
anastomizing, silvery crosslines and costal strigulse; the hindwings
are dark blackish brown. The legs are whitish, the anterior ones
reddish in front.

THE EGG.

The egg is very small, flat, whitish in color, and is laid singly at
the base of a bud. Dissection of a female abdomen proves that
upwards of a hundred eggs are laid by each female; this is a rather
greater fecundity than is normal in this group of insects.

THE LARVA.

(PI. II, lower figure.)

The young larva is dark brown with deep black head and thoracic
shield, the latter divided by a narrow central line. The body of
the older larva becomes somewhat lighter, but is still much darker
than the larva of any of our allied native species. The full-grown
larva is two-thirds of an inch long.

THE PUPA.

The pupa is stout, robust, light chestnut brown with darker head
and back. The wing covers reach to the end of the fourth abdominal
segment. The abdominal segments are armed with rings of short,
sharp, blackish-brown spines.

ALLIED AMERICAN SPECIES.

There are in this country several indigenous species closely allied
to Evetria huoliana^ and like it confined to pine. Some of these
already constitute a serious problem and periodically do considerable

8 BULLETIISr 170, U. S. DEPARTMENT OF AGRICULTUEE.

damage to pine forests and more often to pine nurseries. They are
the more capable of injury because there are two generations an-
nually and they thus have two chances each year to accomplish their
damaging work. None of these native species can, however, even
with this advantage, be compared in destructiveness to the European
species just introduced. This is partly due to the larger size of the
introduced species and to the greater voracity of the larva, but is
mainh^ due to the difference in the attack, which causes a different
reaction of the tree.

The larva of the native species of the genus confines itself to a
single twig and finds its food within this or within a single bud, or at
most a few buds. This bud or twig dies, but the tree responds with
the natural growth of the next set of buds and very often recovers
from the injury without permanent disfigurement. The resulting
injury to the trees is serious only when these native species are- present
in unusually large numbers. Moreover, each of the native American
species is more or less confined to a single or a few species of Pinus,
but the European pine-moth thrives indiscriminately on all species
of Pinus and has consequently a greater chance to become excessively
abundant., While several of the native species are continually of
some economic importance and periodically become a serious menace
even to larger trees, it is mainly when they occur in large numbers in
nurseries that they become really troublesome. Large trees become
checked in their growth by the loss of terminal twigs, but are not
necessarily seriously deformed in their future growth, although an
undesirable forking of the tree top is a quite common result.

On the other hand, the larva of the European pine-shoot moth is
very voracious and not only destroys a number of buds and young
sprouting shoots by eating their interior, but it invariably damages
the remaining shoots in the cluster by nibbling their bases on the
inner side. The subsequent growth of these injured shoots, in the
effort to supplant the destroyed leader, causes greater permanent
injury to the value of the tree than if they were entirely removed.

NATURAL ENEMIES.

Evetria huoliana in Europe is, to some extent, kept in check by a
large number of parasitic enemies. As early as 1838 Hartig'
recorded 14 ichneumonid wasps and 1 tachinid fly - which he had
reared from pupa? of the pine-shoot moth. It has since been ascer-
tained that there are several other parasites ; among the ichneumonids
Ratzeburg considered the following three, which he himself had
reared, as the more important: Prlstomerus vulnerator Panz., Cre-
mastus interrui')toT Grav., and Orgilus ohscurator Hald.

1 See " Literature," p. 10. - Actia pinipennis Fallen.

THE EUEOPEAN PINE-SHOOT MOTH. 9

To promote the good work of these parasites specially constructed
rearing houses have been erected in Europe during bad outbreaks
of the pine moth. The infested twigs are collected in these small
houses, which permit the escape of the parasites but not of the
moths.

It is reasonable to suppose that some of the native parasites on
some of the native species of Evetria will in time also attack Evetria
huoliana in this country — in fact, parasitized larvse have already
been observed — but these native parasites can not be relied upon to
keep in check their natural hosts, the American pine moths, which
sporadically become very abundant and injurious in spite of the
parasites, and presumably will be less effective in controlling the
newly introduced host.

METHOD OF CONTROL.

The larva of the European pine-moth is so effectively protected
within the buds that it can not be reached by any insecticide, and the
onh^ method of combating it is that used in Europe for more than
a hundred years, namely, the pruning and destruction of the in-
fested buds and twigs together with the larvae they contain. Such
hand picking is practiced every year in the government-controlled
forest reserves of Europe.

This pruning must be done while the insect is within the twigs,
and while it may be done throughout the entire year, except during
the midsummer months when the insect is in the adult stage, it can
be most profitably done in the fall and winter months while the
young larva3 are yet within the undeveloped buds, because the prun-
ing at this time will enable the secondary set of buds to develop in
the spring without delay. The only drawback to the collecting of
the larvae in the fall and winter is that tlie infested buds are then
less noticeable than in the spring when the injury is further devel-
oped. A little practice, however, soon enables instant recognition
of the infested buds, even by an unskilled laborer ; the slight exuda-
tion of pitch at the base of the bud covering the entrance hole of
the larva (PL III) is very characteristic and easily recognized when
once known.

In the spring, when the buds develop into young shoots, the in-
jury is very much more apparent, and anybody can then distinguish
the infested twigs at a glance. For this reason it is advisable to have
the trees gone over again in the spring, so as to remove any infesta-
tion which has been overlooked in the fall. In America the work of
the larva in the fall (September, October, and November) has jDro-
gressed far more and is much more easily discovered than is the case
in Europe, where the larvae have attained very small proportions and

10 BULLETIN 170, U. S. DEPARTMENT OF AGEICULTUEE.

haA^e attacked onl}^ one or two buds before the winter resting period
intervenes.

The fact that this species is stationary during the greater part of
the 3^ear and only found within definite parts of certain kinds of
trees, namely, in the next year's buds of pines, makes effective con-
trol work much easier than is the case with insect pests wdiich
are general feeders and which are not confined to definite parts
of the food plant, as, for example, the gipsy moth or the brown-
tail moth. While the European pine-shoot moth is confined to
nurseries and private parks and has not spread to the native pines,
it should prove a comparatively easy task to eradicate the species
absolutely within any limited area. At the present time it would
even seem possible completely to stamp out this dangerous pest in
America, and forestall the infestation of our native pine forests,
provided that the danger of new infestation is removed. But when
once the species has multiplied sufficiently to become generally dis-
tributed on the native pines the possibility of eradication w^ill be
past.

SYNONYMY OF EVETRIA BUOLIANA SCHIFFERMILLER.

Tortrix buoliana Scliiffermiller, Syst. Yerz. cl. Schmett., p. 128, 1776.
Coccyx buoliana Treitschke, Schmetterlinge von Europa, a'oI. S, p. 140, 1830.
Tortrix {Coccyx) buoliana Ratzeburg, Die Forst-Insecten, vol. 2, p. 202, 1840.
Retinia buoliana Guenee, Europaeoriim Microlepidopterorum index methodicus,

p. 46, 1845.
Coccyx buoliana Herrich-Scliaffer. Bearb. d. Sclimetterlinge von Europa, vol. 4,

p. 221, 1849.
Evetria buoliana Meyrick, Handbook of British Lepidoptera, p. 470, 1895.
Evefria buoliana Rebel, Catalog der Lepidoptereu des palaearctischen Faunen-

gebietes, T. II, No. 1851, 1901.

LITERATURE.'

1776. Schiff^rruiller, I. Systematiscbes Verzeicbniss der Schmetterlinge der
Wiener Gegend. Wien.

Original description of Evetria huoViana.
1809. Niemann, E. Forststastistik der Danischen Staaten, Altona.

Describes outbreali in Denmark in 1S05-1807, and tlie collecting of larvae in
the effort to control the species. .

1838. Havtig, T. Tortrix buoliana. In Jabresberichte liber die Fortschritte
der Forstwissenscbaft und forstlicben Naturkunde, Jahrg. 1, Heft 2,
p. 207-268, Berlin.

Kocords the rearing of 15 species of parasites from Evetria buoliana.

1840. Ratzeburg, J. T. C. Die Forst-Insecteu, T. 2, p. 202-207, Taf. XIV, fig. 4.

Berlin.

Detailed account with illustrations of the life history, work, economic im-
portance, remedies, natural enemies, and litei'ature of the species, with
notes of severe outbreaks in Germany, 1835-1838.

^ This is not intended to be a complete bibliography of Evetria huoliana; a large num-
ber of special articles have appeared in various publications in Europe, and every hand-
book on insects or forestry contains more or less exhaustive accounts of this pest.

THE EUEOPEAN PINE-SHOOT MOTH. H

1895. Judeich, J. F., and Nitsclie, H. Lehrbucli der mitteleuropaischen Forst-
insektenkunde, Bd. 2, p. 1004-1008. Wieu.

Condensed (5 pages), life-history and economic importance with original
figure of the injury done by the species.

1897. Lovink, H. J., and Ritzema Bos, J. Scliade in jonge dennen bosschen
teweeg gebracbt door rupseu uit het bladrollergeslacbt Retinia Gn.
(" dennenknoprups " " deuuenlotrups " " barsbuilrups " ) . In Tijdscbr.
Plantenziekten, Jabrg. 3, Afl. 4, p. 83-133, figs. 6, pis. V-VII, Oct.
, Detailed account of the species and its injury, with colored plates.

1897. Severin, G. Insectes. Extrait du Catalogue detaille et lllustre du Pa-

vilion des eaux et forets a I'Exposition Internationale de Bruxelles-
Tervueren, p. 46-49, pi. X. Bruxelles.

Contains short illustrated account of Tortrix (Retinia) buoliana Schiflfer-
miller and its injury : Plate I of the present paper has been copied from
this article.

1898. Boas, J. E. V. Dansk Forstzoologi. Copenbageu.

Condensed life history, injury, and references, with original observations and
figures.

1898. Hess, R. A. Der Forstschutz, ed. 3 eul., v. 1, p. 492-494, figs. 174-175.

Leipzig.

Condensed handbook information on Tortrix {Retinia) buoliana Schifif.
1901. Severin, G. Le genre Retinia, Pyrale des pommes, des bourgeons, de la

resine. In Bui. Soc. Cent. Forest. Belg., t. 8, p. 598-605, 674-685, 2 pis.,

7 figs.

Monographic account of the three most important injurious species of the
genus Evetria in Europe, with text figure and colored plate of Evetria
buoliana. It should be noted that the larva figured under and credited to
Evetria buoliana belongs to Evetria resinella, figured on the next colored
plate, and vice versa.

1912. Gillanders, A. D. Forest Entomology, ed. 2. Edinburgh and London.

Condensed handbook information.

1913. Nusslin, O. Leitfaden der Forstinsektenkunde, 2. ueubearb. und verm.

Aufl., p. 417-418, figs. 350, 352. Berlin.

Condensed handbook information on Grapliolitha (Evetria) buoliana SchiflC.

1914. Busck, August. A destructive pine-moth introduced from Europe {Eve-

tria buoliana Scbifi'ermiller). In Jour. Econ. Ent., v. 7, no. 4. p. 340-
341, pi. IX, August.

First notice of the pest in America.

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^^

UNITED STATES DEPARTMENT OF AGRICULTURE
BULLETIN No. 173

Contribation from the Boreaa of Entomologjr
L. O. HOWARD, Chief

Washington, D. C.

PROFESSIONAL PAPER

April 13, 1915

THE LIFE HISTORY AND HABITS OF

THE PEAR THRIPS IN

CALIFORNIA

By

S. W. FOSTER and P. R. JONES, Entomological Assistants
Deciduous Fruit Insect Investigations

CONTENTS

Page

Introduction 1

History 3

Economic Importance 7

Character of Injury 11

Description 20

Page
Systematic PosiUon ........ 22

Anatomy 23

Life History and Habits 25

Natural Enemies 61

WASHINGTON

GOVERNMENT PRINTING OFFICE

191S

BULLETIN OF THE

u.

No. 173

Contribution from the Bureau of Entomology, L. O, Howard, Chief.
April 13, 1915.

(PROFESSIONAL PAPER.)

THE LIFE HISTORY AND HABITS OF THE PEAR
THRIPS IN CALIFORNIA.

By S. W. Foster ' and P. R. Jones,- Entomological Assistants, Deciduous Fruit

Insect Investigations.

INTRODUCTION.^

The so-called pear thrips, {EutJirips) Txniothrips pyri Daniel, first
attracted attention during the spring of 1902 in a prune orcliard
near San Jose, Cal. Its injuries rapidly increased in the Santa
Clara Valley, and the insect spread to other orchard sections in the
San Francisco Bay region. Its increasing destructiveness and
spread led to the establishment by the Bureau of Entomology of a
laboratory in the Santa Clara VaUey to determine the life history
and habits of the pest and to determine, if possible, measures for its
control in orchards. The laboratory thus started durmg the summer
of 1907 was continued to the fall of 1912.

Mr. Dudley Moulton, an agent of this bureau, who, as Santa Clara
County entomologist, had previously had experience with the insect,
was placed in immediate charge of the work, in which position he
contmued until September, 1909. During his period of service
Mr. Moulton was assisted m the Santa Clara Valley at one time or
another by Messrs. C. T. Paine, S. W. Foster, and P. R. Jones.

In the fall of 1908 owing to the rapid dissemination of the pear
thrips to the northward an additional laboratory was estabhshed in
Contra Costa County, with headquarters at Wahiut Creek. This
work was placed under the immediate dhection of Mr. S. W. Foster,
who also had charge of operations in the infested counties to the north.
During the spraying season of 1909 Mr. Fred Johnson collaborated
with Mr. Foster in experimental and demonstration sprajmig in

1 Resigned Oct. 10, 1912.

2 Resigned S?pt. 30, 1912.

'■> By A. L. Quaintanoe, In Charge of Deciduous Fruit Insect Investigations.

73390°— Bull. 173— lo 1

2 BULLETIN 173, U. S. DEPARTMENT OF AGRICULTURE.

orchards, and in July of the same year Mr. E. J. Hoddy was assigned
to the Wahiut Creek laboratory and assisted in certain cultivation
experiments at Suisun in the fall of 1909, and with Mr. R. W. Braucher
assisted in the demonstration spraying operations at Suisun and
Courtland during the spring of 1910. During the spraying season
of 1911 Mr. Foster was assisted by Messrs. E. L. Jenne and R. L.
Nougaret.

Upon the resignation of Mr. Dudley Moulton Mr. P. R. Jones was
placed in charge of operations in the Santa Clara Valley and was
assisted during the spraying season of 1910 by Mr. E. L. Jenne and
during the spraying season of 1911 by Messrs. A. G. Hammar and
W. M. Davidson.

During the spraying season of 1912, owing to the absence from
California of Mr. Foster, Mr. Jones was charged with all of the pear-
thrips operations in California and was assisted in the work by Messrs.
W. M. Davidson and L. L. Scott, located at Courtland, by Mr. R. L.
Nougaret at Suisun, and by Mr. E. L. Jenne at Walnut Creek.

The manuscript for the present report has been prepared as fol-
lows: All of the data relating to Contra Costa County and counties
to the northward have been prepared by Mr. Foster, the senior author.
Report of operations in the Santa Clara Valley, as w^ell as much of
the life-history matter, has been prepared by Mr. Jones. The re-
maining chapters were written jointly by Messrs. Foster and Jones.

Especial acknowledgment is due to the supervisors of Contra Costa
County and Santa Clara County for their assistance in furnishing
facilities for work during the season of 1909, and for supplementing
the bureau's funds before the special appropriation from Congress
was available. The bureau desires also to acknowledge its obliga-
tions to many orchardists in the thrips-infested territory, who placed
at the disposal of the Department of Agriculture their orchards and
facilities for experimental and demonstration purposes. The suc-
cess which many orchardists have obtained in the control of the
pear thrips by the adoption of the recommendations of the bureau,
as well as the large-scale spraying demonstrations which the bureau
has conducted, has fully demonstrated the effectiveness and practi-
cability of the methods recommended. Especial acknowledgment
is made also to Mr. W. S. BaUard, of the Bureau of Plant Industry of
the United States Department of Agriculture, for much valuable
assistance and numerous courtesies rendered during the course of
the work at Suisun.

The present paper deals with the life history and habits of the
pear thrips, the results of experiments and demonstrations with
sprays and other remedial operations having been given in Circular
No. 131 of the Bureau of Entomology.

THE PEAK THKIPS IN CALIFOENIA. 3

HISTORY.

LITERATURE.

The first reference in literature to the pear thrips is the original
description of the insect by Miss M. Daniels in Entomological News
for November, 1904.^ The type specimens were taken on pear near
San Leandro, in Alameda County, Cal., for which reason it was given
the common name ''pear thrips."

Dudley Moulton,' in 1905, published the first account dealing with
the economic importance of this species. He described its different
stages and the nature and extent of injury caused by it, and included a
discussion of its life history. No advice was given as to remedial
measures, except that early winter plowing was advocated.

The third reference to the pear thrips in literature was by the same
author in Bulletin 68, Part I, of the Bureau of Entomology.^ This
contained practically all that was included in the former pubhcation,
with additional information accumulated, makmg a more complete
account of the pest. It was illustrated with appropriate figures of all
stages, including the eggs and pupa, which had not theretofore been
figured. No successful remedial measures, however, had been de-
termined.

The next publication was also by Moulton, and was issued as Bul-
letm 80, Part IV, of this bureau.* It gave an extended account of
the life history of the pear thrips, with recommendations for early
fall plowmg and cross-plowing, to be followed by spraying in the
spring for the adult and an application against the larvae after the
falling of the petals. Tables were given showing the actual number
of thrips killed in the plowed as compared with the unplowed areas.

The next account was published as Circular 131 of the Bureau of
Entomology,^ and is a concise abstract of the present paper.

The Journal of the South-Eastern Agricultural College, Wye,
Kent County, England, No. 19, for 1910 (published in 1911), con-
tains an article by F. V. Theobald® dealing with thrips in general, in
which this species receives considerable prominence.

1 Daniel, S. M. New California Thysanoptera. In Entomological News, v. 15, no. 9, p. 294-295, No-
vember, 1904.

2 Moulton, Dudley. The Pear Thrips {Euthrips pyri). California State Horticultural Commission,
Publication, Sacramento, 1905. 17 p., 8 figs.

3 Moulton, Dudley. The Pear Thrips. {Euthrips pyri Daniel.) U. S. Dept. Agr., Bur. Ent., Bui. 68,
pt. 1, 16 p., 8 figs., 2 pis., June 10, 1907.

4 Moulton, Dudley. The Pear Thrips and its Control. {Euthrips pyri Daniel.) U. S. Dept. Agr., Bur.
Ent., Bui. 80, pt. 4, p. 51-66, figs. 13-17, pis. 4-6, Sept. 4, 1909.

6 Foster, S. W., and Jones, P. R. How to Control the Pear Thrips. U. S. Dept. Agr., Bur. Ent., Circ.
131, 24 p., 14 figs., Jan. 9, 1911.

s Theobald, Fred. V. Report on economic zoology for year ending Sept. 31, 1910, p. 57-67, fig. 5,
Pis. XXV-XXVni. In Jour. Southeast. Agr. Col., Wye, no. 19, 1911.

4 BULLETIN 173, U. S. DEPAETMENT OF AGRICULTURE.

Also in 1911 Mr. P. J. Parrott ^ published an account of the appear-
ance of this species in New York State, and in January, 1912, he
issued a more extended account of the pear thrips iu New York.^

fflSTORY IN ORCHARDS AND DISTRIBUTION.

The first reported injury caused by tlie pear thrips was noticed in
the year 1902, in an orchard owned by Judge S. F. Leib and Mr. G. M.
Bowman. This orchard was situated in the Berryessa district of
the Santa Clara Valley, near vSan Jose, and consisted chiefly of the
Imperial variety of prunes. The injury was noticed at first on about
20 or 30 acres of the 200 acres of orchard, and the cause of the trouble
at that time was unknown. In the spring of 1904 every other row
of this orchard was top-worked with sugar prunes, chiefly to secure
better cross-pollination with the Imperial variety of prunes, the lack
of w^hich was supposed to have been the cause of failure of the crops
in the past. During a drive through 100 acres of this orchard the
fruit buds were observed to be just beginning to show the white tips
of the petals, and the prospects seemed excellent for a good crop.
When revisiting the place five days later, the owner found to his
utter astonishment that the whole orchard had the appearance of
having been scorched with fire and that there was not an average of
a dozen blossoms to the tree.

The thrips were discovered this same year (1904) in the orchard
of Mr. R. K. Thomas, on Cypress Avenue, near Stevens Creek Road,
about 7 miles distant in an air line from the Leib orchard. From
these two orchards infestation has, with the exception of a few acres,
spread all over the Santa Clara Valley and into other valleys sur-
rounding the San Francisco Bay.

No exact information is available as to the first appearance of the
thrips in other counties, but many orchardists claim that it has been
in Contra Costa County since 1904 and in Solano County at least
since 1906. In addition to these centers of infestation in Santa
Clara, Contra Costa, and Solano Counties, the insect is now present
in considerable numbers in Alameda, Sacramento, Yolo, Napa,
Sonoma, San Joaquin, and San Benito Counties. The general area
of infestation in California is indicated in the accompanying map

(fig. 1).

There have been several reported outbreaks of this species in other
parts of the wState, notably from the Sierra Nevada foothills near
Newcastle and Auburn, near Red Bluff and Anderson in the Sacra-
mento Valley, and from the fruit districts of Tulare and Fresno
Counties in the San Joaquin Valley. The species in question, how-

'Parrott, P. J. Occurrence of Euthrips pyri Daniel in New York State. In Science, n. s., v. 34, no. 864,
p. 94, July 21, 1911.

2 Parrott, P. J. The Pear Thrips. N. Y. Agr. Exp. Sta., Geneva, N. Y., Bui. 343, p. 341-366, 4 figs.,
pis. 30-33 and 1 col. pi., Jan., 1912.

THE PEAR THEIPS IN CALIFORNIA.

ever, were found to bo (Eathrips) Frankliniella occidentalis Pergande
and (Euthrips) Frankliniella tritici Fitch, neither of which is particu-
hirly injurious to deciduous fruits. Reports of injury supposed to
have been caused by this species were received from the Rogue River
Valley hi Oregon, but a critical examination, in 1909, showed no
signs of the work of the pear thrips. In the spring of 1910 many
larviB of (Euthrips) FranHinie.lla tritici were
found, but none of the species under consid-
eration could be obtained.

Not until the year 1911 was tlje pear thrips
positively known to be present in the United
States outside of the infested districts of Cali-
fornia. However, in the spring of 1911 Mr.
P. J. Parrott found it in considerable numbers
around Germantown and other points
along the Hudson River in New York.^
Later in the year specimens of
(Euthrips) Tseniothrips pyri
were found among some Thy-
sanoptera which had been col-
lected in the spring
by IVIr. Parrott in the
vicinitv of Geneva,
N. Y. "

In May, 1912, Mr.
A. L. Quaintance sent
the authors a number
of specimens of thrips
collected in pear blos-
soms from six differ-
ent orchards by ]Mr.
Fred Johnson at North East, Pa. All proved to be tlie pear thrips,
(Euthrips) Tseniothrips pyri.

In 1909 Bagnall - reported that numerous examples of this very
injurious species, taken in phmi blossoms at Evesham, England, had
been sent to him by Mr. Walter Collinge. So far as we know, this
and the previously mentioned account by Theobald are the only
published reports of the occurrence of this species outside of the
United States.

Two other species of Thysanoptera (Thrips plnjsapus L. and T. flam
Schrank) are mentioned by Carpenter as the "pear-blossom thrips"

1 Parrott, P. J. Occurrence of Euthrips pyri Daniel in New York State In Science, n s., v. 34, no. 864,
p. 94, July 21, 1911.

2 Batcnall, Richard S. A contribution to our knowledge of the British Thysanoptera (Terebrantia), with
notes on injurious species. In Jour. Econ. Biol., v. 4, no. 2, p. 33-41, July 7, 1909.

Fig. 1.— Map showing general area of infestation by the pear thrips
in California. (Authors' illustration.)

6 BULLETIN 173, U. S. DEPARTMENT OF AGEICULTUEE.

in his report before the Royal Dublin Society for 1900/ and as the
"pear thrips" in his report to the same society for 1901.- In the
report for 1900 he states that these two species were found feeding
in unopened pear blossoms near Dublin, and he attributes the failure
of the fruit that season to the work of these insects. The report for
1901 states that a Dr. Barton tried a dressing of kainit around the
trees, with very satisfactoiy results.

In December, 1914, Mr. W. M. Scott ^ reported the occurrence of
the pear thrips m a Kieffer pear orchard near Baltimore, Md. The
insect was so abundant as completely to destroy the crop of fruit.

THEORIES AS TO ORIGINAL HOME.

Various ideas have been advanced as to the original home of the
pear thrips. Dr. Pietro Buff a, a well-known student of Thysanoptera,
in private correspondence under date of April 17, 1909, suggested that
while it is a good species it should be put only in the genus Physopus,
and expressed the belief that it was not a European species. Prof,
Silvestri suggested that it was introduced from China or was of other
oriental habitat. Several leading fruit growers have expressed the
belief that the insect was introduced into this country from France
or England, giving as the reason its apparent partiality to prunes,
which are varieties of European plums.

The occurrence of the pear thrips in England lends some weight to
the theory that it is of European origin. It may be that natural
conditions hold it in check in England and that its advent into Cali-
fornia under conditions more suitable for its rapid increase explains
its presence there in such enormous numbers. Now, however, that
its presence is definitely established in the eastern United States, it
is probable that the insect had been in this country for years before
it was discovered.

It may be possible that the pear thrips is native to the Santa Cruz
Mountains, with some wild rosaceous plant as its original food plant.
Upon this supposition it is probable that it has been present in the
Santa Clara Valley for many years, and that it first became notori-
ously destructive with the advent of favorable conditions. While
this species has been taken upon a great variety of plants and has
been found to be able to subsist on many of them, it is distinctly an
enemy of deciduous fruits, to which it shows a decided preference.

COMMON NAMES.

Many common names have been assigned to this insect, as ''pear
thrips," ''prune thrips," "cherry thrips," etc. The first mentioned,

1 Carpenter, G. H. Report on economic entomology for the year 1900, p. 96-97. Reprinted from the
Report of the Council of the Royal Dublin Society for 1900.

2 Carpenter, G . II. Injurious insects observed in Ireland during the year 1901, p. 153-154. In The Econ-
omic Proceedings of the Royal Dublin Society, v. 1, pt. 3, no. 5, July, 1902.

3 Jour. Econ. Ent., v. 7, No. 6, p. 47S-479, Dec, 1914.

THE PEAE THKIPS IN CALIFOKNIA. 7

namely, ''pear thrips/' has been more extensively used, following
the original designation of the insect, because the species was first
described from specimens taken upon pear trees. The word "thrips"
is a general term for the species of the order Thysanoptera and is
sometimes erroneously applied to certain other insects, as the grape
leafhopper (Typhlocyha comes Say). The word ''thrips" is both
singular and plural.

ECONOMIC IMPORTANCE.

DESTRUCTIVENESS.

This minute insect, which until 1904 was unknown to science, is at
present one of the most important insect pests with which the growers
of deciduous fruits in the San Francisco Bay region and adjoining
counties have to contend. The rapidity with which the insect
spreads, its suddenness of attack and complete blasting in a few days
of all prospects for a crop of fruit, and the difficulty experienced in its
control, combine to make its subjugation a matter of considerable
difficulty. Moreover, as the insect is each year developing an ability
to subsist on other and new food plants, its capabilities for dissemi-
nation become correspondingly increased. There is no reason to
beheve that the thrips will disappear in a few years, and it should be at
once realized that only the most careful attention each year to neces-
sary control measures will make it possible to continue the profitable
culture of fruit in regions where this insect is present in any con-
siderable numbers.

In the Santa Clara Valley this insect has been worse some years
than others, notably in 1905, 1907, 1908, 1909, and 1910, but it is
safe to say that from now on the maximum prune crop possible for
this valley will never again be reached unless every orchardist does
the utmost in his power to control the thrips. Wliiie it may be pos-
sible for unfavorable weather conditions to reduce the possibility of
a good crop of 100,000,000 pounds of dried prunes for this valley to
something hke 40,000,000 or 50,000,000 pounds, the thrips, in a
great measure, has been responsible for the small crops since 1907,
and will continue to be so, first, by killing the fruit buds before they
bloom; secondly, by depositing the eggs in the fruit stems, and,
thirdly, by the feeding of the larvse on the fruit, causing it either to
drop prematurely or to develop misshapen and scarred on the trees.
While the thrips is doing much serious work in the Santa Clara
Valley to cherries and pears and the damage done to different varie-
ties of peaches is increasing, yet on account of the small acreage of
these fruits the chief loss from a commercial standpoint is to the
prune industry. Some idea of the destruction caused by the pear
thrips during the previously mentioned bad years may be gained
from the following figures, giving the approximate yield of prunes in
pounds each year for the years 1900 to 1912, inclusive.

BULLETIN 173, U. S. DEPAKTMENT OF AGRICULTURE.
Table I. — Yield of prunes for the Santa Clara Valley, 1900~iyu, inclusive.

Season.

Yield of dried

fruit.

Season.

Yield of dried
fruit.

1900

Pounds.
120, 000, 000

35, 000, 000
120,000,000

9(1,(100,(100
1(1(1, (1(1(1, 111 10

50. 000.000

1907

Pounds.
50, 000, 000
40, 000, 000
85, 000, 0(J0
( 35,000,000
\ 40,000,000
100, 000, 000
t)5, 000, 000

19011

1902

1903

1908

1909

1910

1911.

1904

1905

1906 120.000.000

1912

' Severe frost.

In 1911 the pear thrips probably caused a heavy loss in spite of
the fact that there were not more than one-half as many thrips
present in this valley as in 1910. The good prune crop in the Santa
Clara Valley in 1911 was due to light thrips injury and the very
heavy rainfall. The amount of rainfall, which was about 8 inches
more than the normal, not only placed the trees in excellent shape
to bear a heavy crop, but, coupled with other climatic conditions
during the early part of 1911 and latter part of 1910, lessened the
work of the thrips very materially. Notwithstanding a favorable
fruit year from a weather point of view, thrips in some places caused
a great amount of damage. The thrips damage in the Santa Clara
Valley for 1910 was caused principally by the adults, with very
little larval work, while for 1911 it was just the reverse, the adults
doing comparatively little injury because of less numbers and strong
fruit buds as a result of the heavy winter rains. The scarcity of
adult thrips in 1911 may have been due to several causes. Two
heavy rains during the early part of April of the previous year
knocked off many young larvae before they were sufficiently mature
for transformation. In addition the season for pupating, June to
December, 1910, was abnormally dry, showing a deficiency in rain-
fall of 5.28 inches, while the emergence period in the spring of 1911
was unusually wet and cold. All of these conditions caused a higher
mortality than would be the case under normal conditions. However,
in orchards which showed comparatively few adults the larvae were
sufficiently abundant to riddle the foliage and cause much of the
young fruit to drop. The heavy rains during the emergence period
also checked to some extent the work of the adults.

In estimating the economic loss to the fruit industr}^ of California
caused by the pear thrips it is necessary to begin with the year 1904,
when it was first known that the insect was doing commercial damage,
and continue down to the present time. An attempt will be made
to give a fair estimate of the amount of damage done yearly to the
prune industry alone in the Santa Clara Valley for the years 1904
to 191 1, inclusive.

THE PEAR THRTPS IN CALIFORNIA. 9

The average size of prunes grown in the Santa Chara Valley is
60-70; that is, dried prunes requiring from 60 to 70 to make a pound.
The price paid for prunes during the years fi-om 1904 to 1911, inclu-
sive, was variable, but would average close to a ;^-cent basis;
that is, 3 cents per j^ound for dried prunes running 80 prunes to the
pound. In order to be conservative, the average sizC; 60-70, is
disregarded, and the loss is figured on the regular 80-to-the-pound
basis. In 1904 the loss was estimated at 500 tons, or 1,000,000
pounds (dried prunes), which, at 3 cents per pound, amounts to
$30,000. For the year 1905 it was placed at 10,000,000 pounds and
the damage at $300,000; in 1906 at 5,000,000 pounds, worth $150,000;
in 1907, 15,000,000 pounds, worth $450,000; in 1908, 20,000,000
pounds, worth $600,000: in 1909, 30,000,000 pounds, worth $900,000;
in 1910, 40,000,000 pounds, worth $1,200,000; and in 1911, 20,000,000
pounds, worth $600,000. The total of all of these years would be
141,000,000 pounds, valued at $4,230,000.^ The estimates for some
years probably have been close to the actual damage done, but more
frequently the loss has undoubtedly been underestimated. In 1904
all the fruit of one orchard, comprising 100 acres of Imperial prunes,
was totally destroyed, and this alone at an average crop of 5 tons of
green prunes per acre, on a 3-cent basis for dried prunes, would have
been valued at close to $30,000, because of the large size of this
variety of prune, only from 30 to 40 of which make a pound.

In estimating this loss no account is taken of the great deprecia-
tion in value of the crop caused by scabbing. The entire yield each
year has been counted as merchantable fruit, and estimates of damage
made solely from orchards showing total loss or a marked reduction
in tonnage produced.

To explain more fully the commercial quotation of a 3-cent basis,
it is meant that 3 cents per pound will be paid for dried prunes
averaging 80 prunes to the pound. For prunes which are larger
and free from scab or defects the price is usually $1 per ton more for
each point in size, and for smaller prunes the price decreases corres-
pondingly.

As to the extent of the damage the pear thrips will cause in tliis
county if left unchecked, it is difficult to estimate, but the fact that
thrips were twice as numerous in 1910 as in 1909 shows their ability
to double the damage performed in any preceding year. The cause
for the notably light prune crop in 1910 is not attributed altogether
to the work of the pear thrips, but partly to unfavorable weather
conditions, which pervented man}^ of the blossoms from setting fruit.
However, all the large producing prune districts of the Santa Clara
Valley were very seriously injured by the pear thrips, and hundreds

I These estimates are based on fuller and more complete reports than could be obtained in time for
Circular 131 of the Bureau of Entomology, and these figures more nearly represent the actual loss.
73390°— Bull. 173—15 2

10 BULLETIN 173, U. S. DEPARTMENT OF AGBICULTURE.

of acres in these districts were prevented from })looming — a fact not
attributable to unfavorable weather conditions but solely to ravages
of the thrips. Other orchards, under same weather conditions but
with little or no thrips injury, produced a full crop of blossoms.

During the year 1911 another type of injury that was different
from previous years, which may be called cumulative injury, was
noticeable in many orchards. Barring the three heavy frosts in
April, the blooming and fruithig season hi 1911 was exceedingly
favorable in so far as climatic conditions were concerned. Never-
theless about the 1st of May the trees -in many orchards turned a
sickly yellow owmg to the work of the thrips in 1911 and from devas-
tations by this insect in previous years. Some orchards which were
out of the frost belt and which were not severely injured by thrips in
1911 showed this condition noticeably. It is possible that much of
this was due to neglect of the orchards by fruit growers who did not
obtain crops of fruit during the preceding four years because of the
injury of the thrips to the buds, blossoms, and young fruit.

As mentioned before, practically all of the Santa Clara Valley
came into full bloom in 1911 and gave promise of a record crop, but
larval injury was very heavy over the entire valley. This, with the
result of injury in previous years, apparently greatly weakened the
trees and caused much of the fruit to fall at the first unfavorable
weather.

Injury to pears in the Santa Clara Valley has never risen to great
proportions from a financial point of view, for the reason that most
of the acreage of this kind of fruit is set out near Santa Clara and
Alviso, sections of this valley where the thrips has not yet become
dangerously numerous. However, during the season of 1911 a num-
ber of orchards in these localities became badly infested. The amount
of damage done to cherries in this valley has not been determined
on account of the scattered acreage planted to cherries in the infested
area.

The distinctly severe years for thrips injury in Contra Costa County
in pear orchards were 1908 and 1910, when the crops were practically
annihilated. Also there was great loss the two previous years,
1906 and 1907. The prune orchards suffered in these years and in
the year 1909, producing less than one-third of a normal crop any
one year. The fruit crop has been seriously menaced each year
since 1905, the area increasing yearly, and in 1911 it aggregated a
total loss to the county of between $1,000,000 and $1,250,000.

Solano County has in some ways been more fortunate, as the thrips
has been loiown to cause serious injury only since 1907, but even
in that time the thrips has spread rapidly and caused great damage
on large areas; the damage in 1911 was very extensive and the total

THE PEAR THRIPS IN CALIFORNIA. H

loss to the county attributable to the work of the pear thrips amounted
to at least $750,000.

The damage in Sacramento County was noticeable only in a com-
paratively limited area in 1909, hicreasing considerably both in area
and destructiveness during 1910 and 1911, and the total loss to that
county probably amounted to at least $250,000.

No accurate figures are available for the damage caused in Alameda
County, but a considerable area has been infested for several years
and many conservative estimates put the total loss to, but not includ-
ing, 1912, as more than $150,000.

The pear thrips has more recently been found in slightly injurious
numbers in Yolo and Napa Counties, in the eastern part of Sonoma
County, in the northwestern part of San Joaquin County, and in
some parts of San Benito County.

Including the infested areas in Santa Clara, Contra Costa, Solano,
Sacramento, Alameda, Yolo, Napa, and Sonoma Counties, it is safe
to say that the thrips, in absence of treatment, would cause an average
yearly loss of over $2,000,000. With each additional year an addi-
tional loss of several hundred thousand dollars, due to the increase of
the area infested and the increased losses in the areas previously
infested, is to be expected. The total damage to the fruit industry
of the State of California since the first appearance of the insect
aggregates, it is believed, at least $6,630,000 up to but not including
1912.

FOOD PLANTS.

While the pear thrips is distinctly a deciduous-fruit insect and
practically all of its damage is confined to this class of plants, it has
been found upon a great variety of plants the list of which is increas-
ing each year. The fact of its wide range of food plants makes
extermination practically impossible, whereas control can be readily
practiced. It has been taken upon the following plants and could
probably subsist upon a number of them long enough to make it a
constant menance to the fruit industry of California: Apricots,
apples, almonds, cherries, figs, grapes, pears, plums, prunes, walnuts,
madroiia {Arbutus menziesii), wild California lilac (Ceanothus thyrsi-
Jiorus) , poison oak (Rhus diversiloba) , dogwood (Cornus sp.), acacia,
willow (Salix sp.), laurel (Umhellularia calif ornica), mustard (Bras-
sica nigra), live oak (Quercus wislizeni), miner's lettuce (Montia
perfoliata), and various grasses and weeds.

CHARACTER OF INJURY.

MANNER OF FEEDING AND TYPE OF MOUTHPARTS.

Injury to plants by the pear thrips is caused directly by the feeding
of the adults and larvjB upon the various portions of the fruit, buds,
flowers, and leaves, and also by the deposition of eggs in the leaf
surfaces, fruit stems, and newly formed fruit.

12 BULLETIN 173, U. S. DEPARTMENT OF AGKICULTUEE.

The mouthparts of the Tliysauoptera present many difRculties for
study and are not thoroughly understood. They are so modified
that various writers have disagreed regarding their homologies.
They appear, however, to belong chiefly to the suctorial type, and
they show many traces of a transition from the mandibulate type to
the suctorial. (See PI. I, fig. 7.) Viewed as a whole, the mouthparts
appear as a broad and jointed cone attached to the posterior edge of
the underside of the head and resting for a large part under the
pronotum. The apex of the cone is quite sharp, but not so slender
and drawn out as in the Hemiptera. The mouthparts as a whole
are strikingly unsymmetrical. The most evident marks of this are
the forms of the labrum and the left mandible. The first, which
makes the front wall of the cone, is unsymmetrical in the whole
order, but especially so in the Terebrantia. It is irregularly triangular
in form and is attached by its broad base to the clypeus. It becomes
narrower as it approaches the tip and is usually rounded in the
Terebrantia but more variable in the Tubulifera, where it is pointed
in some species and broadly rounded in others. The maxillae are
broad and flat and constitute the side walls of the mouth cone. They
also taper toward their tips. The labium forms a hiiid wall of the
mouth cone and is usually considerably broader at the tip than at
the other parts. Within this hollow cone lie che piercing organs,
which are three in number. First, there is a single large mandible
lying on the left side of the mouth cavity, whereas the right side has
no corresponding member.^ The other two organs are the maxillary
lobes. These are more slender and longer than the mandibles and are
developed alike on each side. All of the mouthparts are strongly
chitinized at the tip, being more so in the adults than in the larvsB
although the mouthparts of the latter are otherwise closely similar
to the former.

The members of this order are thought to use the mandibles for
piercing the exterior portion t)f the plants, while the maxillary lobes,
which are longer, are used to penetrate deeper into the tissues, and
are moved with a rasping motion, causing the juices of the plant to
flow, so that they may be sucked up into the alimentary canal. In
feeding, as observed by aid of a hand lens, both adults and larvge
exhibit an up-and-down motion of the head combined with a forward
motion which might be properly termed rooting. Most of the species
under the writers' observation prefer to enlarge a wound into the
plant tissues where the juices flow more readily rather than to select
new areas for feeding. This continual macerating of the fruit by
the pear thrips for a period of several days causes on deciduous
fruits what is known as the characteristic pear- thrips scab, which

I The mandible in the Tubulifera is shorter and more bent than in the Terebrantia.

Jl. 1 73, U. S. Dept. ot Agriculture.

The Pear Thrips (Taeniothrips pyri Daniel

Fig. 1.— Adult. Fig. 2.— Egg.s. Fig. 3.— First-stage larva. Fig. 4.— Full-grown larva. Fig. 5.—
Pupa, first stage. Fig. 6.— Pupa, last stage. Fjg. 7.— Side view of head sliowing mouth parts.
All greatly enlarged. (Original.)

Bui. 173, U. S. Dept of Agriculture.

Plate II.

Fig. 1.— Mature Pear Showing Injury Resulting from Feeding of Larv/e of the
Pear Thrips. (Original.)

Fig. 2.— Tomato-Shaped Pears Resulting from Feeding by Adult Pear Thrips in
the Fruit Buds Before Blooming. (Original.)

INJURY TO PEARS BY THE PEAR THRIPS.

THE PEAR T?TRIPS IN CALIFORNIA. 13

is very noticeable when the fruit is picked in the fall. Although at
this time the insects in question have been in the ground three or
four months, the injuiy becomes more apparent with the maturity
of the fruit, and the scabbing or scarring shows as the result of the
early spring feeding by this species.

The most serious injury to deciduous fruits by the pear thrips is
caused, first, by the feeding of the adults; secondly, by the feeding
of the larvae, and thirdly, by the deposition of eggs in the plant tissue
by the adults. The effect of this last injury is more apparent upon
the fruits of prunes and cherries than upon the other deciduous
fruits. Numerous cases have been observed by the writers in both
prune and cherry orchards where the trees blossomed heavily and
there was promise of the setting of a good crop of fruit, but where
practically all the fruit dropped, solely from the effect of having too
many eggs deposited in the fruit stems, thus weakening the tissues,
and because the larvae, feeding directly on the fruit and foliage, so
weakened the tree that it would not support a heavy crop of fruit.
Perhaps the chief injury to cherries is caused by the deposition of
eggs in the fruit stems. The long and tender stem of the cherry
presents a most favorable place for the deposition of a great number
of eggs.

Injuiy to the various fruits by adults and larvne is different, but,
classed in regard to bud structure, those fruits in which only a single
blossom is produced in a fruit bud, such as the almond, apricot, and
peach, seem to be less liable to severe injury than are the fruits which
which form a cluster of blossoms amd later produce a cluster of
fruits, such as pear, prune, cherry, and apple. If the thrips had
their choice of food plants, pears would probably be attacked first
in the spring and destroyed; also, other things being equal, a given
number of thrips would do more injury no doubt in a pear orchard
than in a cherry or ])rune orcliard.

INJURY TO PEARS.

The greater injury to pears is caused by the feeding of the adults
in the bud clusters before blooming. Coming out of the ground in
great numbers in the spring as the fruit buds are swelling, the thrips
soon work their way underneath the bud scales and there attack the
individual buds. The feeding is not a biting and chewing process,
but the thrips, by rasping the tender surfaces in the developing buds
with their hardened or chitinous mouthparts, rupture the skin, and
the exudation of sap begins. If only a few thrips are present this
injury may be slight and the buds may develop and bloom, producing
fruit of normal size, although sometimes short-stemmed, or scarred
and misshapen. (See PI. II, fig. 1.) Plate II, figure 2, shows two
Bartlett pears which grew from a cluster that was badly iujured l)ut

14

BULLETIN 173, V. S. DEPARTMENT OF AGRICULTURE.

not entirely destroyed. Plate III, figure 1, shows a mature Bartlett
pear the one-sid(xl appearance of which was caused partly by adults
and partly by larvse. When thrips are more numerous a greater
amount of the bud surface is injured, consequently there is a greater
loss of sap. If this loss is sufficient to cause the cluster buds to
''bleed" (sap to drop from the end), fermentation quickly sets in
and the entire cluster is soon destroyed. • (See fig. 3, in comparison
with fig. 2, which shows the cluster buds developing normally.) In
many cases blue molds gain a foothold in this fermenting sap and

greatly accelerate the injury,
causing complete destruction
of all fruit buds. The dead
clusters later dry up without
opening. (See PI. Ill, fig. 1,
and compare it with PI. Ill,
fig. 2, which is from a photo-
graph of the sprayed portion
of the same orchard, taken on
the same day.) These dead
buds may remain on the trees
for months unless washed off
by rain or blown by winds.
The writers have seen many
orchards so severely injured
that it was difficult to find a
single healthy blossom, and
the entire orchard from a dis-
tance presented at blossoming
time a brownish color and
dead appearance, due to these
blasted buds.

Weather conditions influ-
ence to a great extent the de-
struction following the injury
caused by the thrips. For
instance, the weather of 1909
in the interior valleys during late February and the first 20 days
of March was open and comparatively dry, with more or less
wind blowing, giving quick evaporation throughout the day. Many
clusters of buds that were kept under observation thi-oughout the
season, wdth from 10 to 20 thrips in the cluster, developed many of
their buds and produced fruit, a large percentage of which was first
class. During tliis period for 1910 there was considerable rain and the
atmosphere was warm and humid with very light evaporation. From
many observations in Contra Costa and Solano Counties it was shown
conclusively that in every case where as many as 10 to 15 thrips

Fig.

2. — Cluster buds of Bartlett pears developing
normally. (Original.)

THE PEAR THRIPS IN CALIFORNIA.

15

gained entrance into the bud duster early in the season, and were left
unmolested, the entire cluster was sufficiently injured to prevent the
api^earance of a single blossom. In 1909 there was greater evapora-
tion, comparatively little of the characteristic bleeding showed at the
tips of the buds, and far less of the blue molds appeared in anyplace.
Also the thrips came out of the ground more slowly than in 191 0. The
latter year thrips were held back to a slight extent by cold wet weather,
but once the emergence from the ground commenced, thrips came very
rapidly. Then, too, they were more
numerous throughout the entire
section in 1910 than they were the
previous year.

The serious nature of this insect
can be understood when it is re-
alized that in a badly infested pear
orchard it is far more usual to find
from 75 to 150 and often as high as
200 thrips to the cluster than only
10 to 15. Any spraying to be effec-
tive must be done before these thrips
have remained long, m numbers,
inside the bud clusters. A delay
of four or five days in spraymg the
badly infested orchards in the spring
of 1910 meant the loss of the entire
crop, and in many cases a delay
of two to three days for the first
application meant a loss of more
than half the crop.

In the ability completely to de-
stroy the crop the adult is of more
importance than the larva, and in
many large orchards the destruction
of the developing fruit buds by the
adults has been so complete that
by the time the trees would normally come into bloom there was left
no possibility for a crop of fruit. The larva, together with the
injury which has been caused by the deposition of the eggs by the
adult, can lessen the prospects of a good crop of fi'uit after it has appar-
ently set. To secure the best results it is always desirable first to
apply efficient treatment against the adult in order to reduce the
early injury to a minimum so that the trees may bloom, and later,
to make additional treatment against the larvae. This will usually
result in increasing the value of the crop from 10 to 25 per cent for

Fig.

3.— Work of the pear thrips on pear at San
Jose, Cal. (Original.)

16 BULLETIN 173, U. S. DEPARTMENT OF AGEICULTURE.

pears Jind 40 to 50 per cent for ]:)runes. If remedial measures are not
successfully used against the adult but only against the larvae, it is
not to be expected that 50 per cent of a crop will be saved; but the
additional treatment against the larvae after the adult treatments
have been applied will cause from 10 per cent to 50 per cent more
of the crop to remain on the trees. Without taking into account
the after effects of migration, good results can be had in pear
orchards by spraying against adults alone, if thorough work is done
at the proper time.

INJURY TO PRUNES.

Next to the pear, thrips injure prunes most severely; and, as the
larger fruit area in the Santa Clara Valley is devoted to this kind of
fruit, and since the pear thrips has caused the failure over large areas
of the prune crop for several years, growers in the Santa Clara Valley
have commonly called this particular species the prune thrips. The
large acreage of prunes and the general distribution of the pear thrips
over the valley, together with the fact that the majority of the thrips
are out before many of the buds of the French prunes have started
to spread, make it very evident that these little insects, which are
waiting on the outside of the twigs in enormous numbers, will at the
first sign of life of the prune buds bury themselves into the very heart
of the tenderest parts, and rapidly carry on their work of destruction.
The numbers that will get inside of a prune cluster is really aston-
ishing. Many times the writers have, from a single cluster, taken
more than a hundred of these little insects feeding upon the tender
blossom stems, the tips of the petals, and the stigma and style of the
blossoms when they have opened. These parts mentioned seem to
be the choice bits for the adults when feeding upon the prunes. The
rapidity with which the thrips can destroy the whole year's crop is
astonishing. ]\Iany a time orchardists have gone into their prune
orchards at the time the buds were about ready to spread, and, with
only casual observation, have failed to see these minute, dark-colored
insects crawling around or at rest upon the twigs and buds. Upon
inspecting the orchard four or five days later, expecting it to be in
full bloom, they have been astounded to find practically all the buds
destroyed, leaving no hope for a crop that year, the entire orchard
presenting a brown, burnt appearance, with only a stray blossom
now and then, a sight which is well known now to the majority of
the prune growers of the Santa Clara Valley. Anyone who has ever
seen one of these prune orchards with the burned, browned, and
blasted appearance beside another of snowy whiteness will never
forget the contrast. (See PI. IV, comparing fig. 1 with fig. 2.) Again
there may be a very severe larval injury on prunes, such as was the
case in 1911. Very few adult thrips occurred in comparison with

Bui 173, U. S Dept. of Agriculture.

Plate III.

Fig. 1.— Untreated Portion of Pear Orchard, Showing Loss of Pear Blossoms
Resulting from Attack of the Pear Thrips. (Original.)

Fig. 2.— Sprayed Portion of Same Orchard, Showing Trees in Blossom. (Original.)
INJURY TO PEAR ORCHARDS BY THE PEAR THRIPS.

Bui. 173, U. S. Dept. of Agriculture.

Plate IV.

Fig. 1.— Unsprayed Portion of Prune Orchard in which Blossoms are Com-
pletely Destroyed by the Pear Thrips. (Original.)

Fig. 2.— Sprayed Portion of the Same Orchard, Showing Trees in Full
Blossom. (Original.)

INJURY TO PRUNE ORCHARD BY THE PEAR THRIPS.

Bui. 173, U. S. Dept. of Agriculture

Fig. 1.— Prunes Scabbed as a Result of Feeding by Pear Thrips Larv/e, (Original)

Fig. 2.— Normal Fruit, Uninjured by the Pear Thrips. (Original.)
PRUNES INJURED AND UNINJURED BY PEAR THRIPS LARV/€.

THE PEAR THEIPS IN CALIFORNIA.

17

1910, and they did not accomplish much injury in the Santa Clara
Valley, but larvae were present in large numbers everywhere and
riddled the foliage (fig. 4) and weakened the fruit stems, making the
financial loss amount to about half as much as in 1910.

In regard to varieties, Imperial prunes seem to be attacked first
and injured, on the whole, more severely than French prunes in the
Santa Clara Vallc}^. This may be explained in several ways: For
one thing, the acreage of this variety in the Santa Clara Valley is
much less than that of the French prunes and the blossoming period
is usually about a week or more earlier; then, too, the small develop-

FiG. 4.— Prime foliage riddled by pear thrips larvae. (Original.)

ing fruit stems of the Imperial prunes seem to be more tender and
not so able to withstand the attacks of the thrips as are those of the
French prunes. Sugar prunes, which blossom at a period interme-
diate between the blossoming periods of Imperial and French prunes,
are, from a financial standpoint, not injured so greatly as are either
of the other varieties. This is partly due to the fact that this variety
sets an unusually large amount of fruit and is therefore able to with-
stand the loss of a considerable portion of it and still produce a fair
crop. The scabbing of the prunes on this variety, however, is often
so deep as to cause a large exudation of gum and to render a large

73390°— Bull. 173—15 3

18 BULLETIN 173^ U. S. DEPARTMENT OF AGRICULTURE.

portion of the fruit unmarketable. Plate V, figures 1 and 2, shows
photographs of sprayed and unsprayed prunes, the prunes having
been picked from trees when full growai. Robe de Sargent prunes
blossom about the same time as French prunes, and are injured to
the same extent as that variety.

INJURY TO CHERRIES.

Cherries, as a whole, arc not injured so severely by the feeding of a
given number of adults as would be the case for the same number of
thrips upon pears and prunes, but certain varieties, especially the
black cherries, suffer comparatively as much from a monetary stand-
point as either pears or prunes. Probably the worst damage accom-
plished on cherries is by the deposition of eggs in the long fruit stems
and in the leaves, and by the feeding of the larvae upon the foliage.
The deposition of eggs in the fruit stems has at times caused a large
percentage of the cherry crop to drop, and it is a common sight to
sec the foliage entirely riddled by the larvae, thus greatly weakening
the trees. Many other instances are on record where the adults
have injured the fruit buds to such an extent that only a few blos-
soms appeared. Late varieties of cherries, such as the Royal Anne,
escape serious injury more than the earlier blooming black varieties.
Fortunately the manner of bud growth and blossoming of cherries
permits effective penetration of different spray solutions more ad-
vantageously than is the case with either pears or prunes.

INJURY TO APPLES.

While there are not many instances of great commercial injury to
apples, yet individual cases have been known where the adult thrips
have killed all of the buds in the cluster except the central one. This
was especially noticeable in an orchard of the Newtown Pippin variety
in the vicinity of San Jose in 1910. Some small orchards in Sacra-
mento County were rather seriously injured during the same year.

INJURY TO PEACHES.

Follow^ing the apple, peaches come next in importance as regards
possibility of dangerous injury, the early varieties suffering the greater
loss. The more seriously injured varieties are the Muir, Nicol-cling,
Cra\^^ford, Foster, and Lovel, in order of damage done, injury being
more severe on the first two varieties mentioned. On account of the
hairy pubescence on the young peach fruits, the thrips prefer to feed
upon the nectary glands and the inside of the calyx cups ; this pre-
vents proper pollination, and the young fruits drop to the ground a
few weeks after the blossoming period. Where the injury has been
severe, peaches are sometimes prevented from blooming, and the larvae
feeding upon the tender leaves cause them to curl and become dis-

THE PEAR THEIPS IN CALIFORNIA. 19

torted somewhat iii the same maiiner as does peach k>af-curl. Some-
times the larvaB feed on the young fruit, but rarely to the extent of
causing any great loss.

INJURY TO APRICOTS.

Apricots have not, as a rule, been injured commercially except
in cases where there are a few young trees around home grounds or
near an infested pear or prune orchard. They are sometimes injured
to about the same degree as peaches, and in some cases isolated trees
have been observed which failed to bloom as a result of the work of
the thrips. Larval injury to the young fruit is usually more exten-
sive than is the case with peaches and may at times be serious. How-
ever, apricots are apparently not favorite breeding places for thrips.

INJURY TO ALMONDS.

Ahnonds are injured less by the thrips than any ot the foregoing
fruits. On account of the early blossoming of the trees and the rela-
tively greater amount of exposed leaf surface at the time the thrips
are out in numbers, together with the character of the blossom, which
is similar to that of the peach, feeding by the thrips very rarely causes
much commercial loss in almond orchards.

DESCRIPTION.

EGG.

The egg when first deposited is bean-shaped, translucent white, measuring on the
average about 0.416 mm. in length and about 0.166 mm. at its widest part in the
middle. (PL I, fig. 2.)

Just before hatching it decreases in length, appears swollen, has a slight brownish
tint, and is faintly striated longitudinally where the antennae and legs are folded to-
gether. The dark brown spots, the eyes of the young larva, are apparent at one end.

FIRST STiVGE ( LARVA 1 DAY OLD).

Length 0.646 mm.; width of head 0.166 mm.; width of mesothorax 0.183 mm.;
width of abdomen 0.15 mm. ; lengtn of antennae 0.2 mm. ; length of antennal segments:
I 20/1, II 40ju, III 45ju, IV WOpL. General color translucent white. General shape fusi-
form. Antennae, head, and legs large in proportion to the rest of the body, and unwieldy.
Antennae distinctly four-segmented, first segment short, cylindrical; second segment
about twice as long as first, oval cylindrical; third segment slightly longer than second,
urn-shaped; fourth about aslongasrestof joints together, acutely conical. Afewvery
fine incon.spicuous hairs present on all joints, more prominent on segment 4; Head
subquadrate; eyes reddisn brown. Thorax about as long as abdomen, slightly wider.
Abdomen gradually tapering, 10-segmented, first eight segments subequal, IX and X
longer and more abruptly tapering, with a fringe of long, white, nearly inconspicuous
hairs. Legs stout; femora and tibiae nearly equal in length; tarsi one-jointed, ending
in a single black claw. (PL I, fig. 3.)

20 BULLETIN 173, U. S. DEPARTMENT OF AGEICULTUKE.

SECOND STAGE (fULL-GROWN LARVA).

Total length 1.833 mm.; length of head 0.15 mm., width 0.1083 nun.; length of
prothorax 0.1833 mm., width 0.2166 mm.; length of mesothorax 0.1833 mm., width
0.466 mm. Length of antennae 0.2833 mm.; segment I 26/t, II 50/(, III 76/(, IV 66/i,
V 14/i, VI 16//, VII 33/i. Antennae: Segment I short cylindrical; II obtuse spindle-
shaped; III spindle-shaped, about as long as I and II together; IV nearly as long as
III, broader than the rest, subcorneal; V short, narrow cylindrical ; VI slightly nar-
rower and longer than V; VII twice as long as VI, narrower and cylindrical. All
joints transversely striated and with a few inconspicuous white hairs. General color
faintly yellowish wh ite, obtusely fusiform in shape. Body longitudinally and laterally
faintly striated. Head quadrate; eyes prominent, dark reddish brown, situated a
little in advance of the middle; mouth cone broadly rounded, nearly as long as
the head, extending to the middle of the prosternum. Prothorax large, slightly
wider than long, diverging posteriorly. Mesothorax and metathorax short and broad,
twice as wide as long, subequal, in length about as long as prothorax. Abdomen
broad, gently rounded, 10-segment«d, broadest at segments V and VI; first eight
segments subequal; segment IX distinctly longer, tapering to apex, the posterior
edge armed with a circle of strong, short, thick wedge-shaped spines, the two medio-
dorsal and medioventral ones shorter and smaller; segment X slightly tapering, not
quite as long as segment IX. Lateral edges of abdomen finely serrated, also with
a few long inconspicuous white hairs which are more prominent on segment X. Legs
strong; femora and tibiae about equal; tarsi one-jointed, ending in a single black claw.
(PI. I, fig. 4.)

NUMBER OF MOLTS; DEVELOPMENT.

When first hatched the larvae are active and start feedmg imme-
diately and soon become more robust. At the end of about seven to
eight days they molt into second-stage larvae, where (see description)
they are still more robust and show also other difTerences. The total
time required for the development of the larvae is about three weeks,
although this period is shorter during warm weather.

PUPA.

PREPUPA (first stage).

Total length 1.333 mm.; length of head 0.1 mm., width 0.116 mm.; length of pro-
thorax 0.183 mm. , width 0.266 mm. ; width of mesothorax 0.35 ram. ; length of abdomen
0.666 mm., width 0.383 mm. Shape similar to adult; color translucent white, deeply
tinted with brown. Head subquadrate, about as broad as long, eyes dark reddish
brown. Mouth-cone broadly rounded, extending to about one-half length of the pro-
sternum. Antenmi? extending backward on each side of head, apparently four-jointed;
first three segments nearly subequal in length, about as broad as long, thick and
unwieldy; segment IV about as long as remaining joints, club like, and tapering to
an obtuse point. Antennae with a few inconspicuous white hairs. Prothorax nearly
twice as long as the head, broadly rounded posteriorly. Mesothorax broader; wing
pads short, those of first pair of wings extending to distal edge of third abdominal
segment. Abdomen 10-segmented, widest at III and IV, segments gradually tapering
from there posteriorly. First eight segments subequal, IX and X longer, distal end
of IX with broad spines somewhat similar to those of second-stage larvte but shorter
and smaller. Legs stout, similar to those of full-grown larva, whole body with sparse,
light-colored, inconspicuous hairs. (PL I, fig. 5.)

THE PEAR THRIPS IN CALIFORNIA. 21

PUPA (second staok).

Total length 1.416 mm.; length of head 0.183 mm., width, 0.160 mm.; length of
prothorax 0.166 mm., width 0.25 mm.; width of mesothorax 0.35 mm.; length of
abdomen 0.783 mm., width 0.416 mm. Shape similar to adult, which is visible
beneath the thin transparent shell. Apparently brownish in color, caused by adult
within. Head broader than long; eyes large, dark brown; mouth-cone of adult
within extending to posterior edge of prothorax. Antennae large, cumbersome, laid
back on the head and extending past middle of prothorax, four-jointed; I short; II
elbowed, about twice as long as I; III short, cylindrical; IV longer than III, sides
uneven as knotted club gently tapering to obtuse apex. Joint I of adult is in joint I
of pupa, joint II of adult in joint II of pupa, and III of adult within III of pupa;
remaining joints of adult within IV of pupa; 3 or 4 white, inconspicuous hairs pro-
jecting cephalad from elbow on joint II. Prothorax broader than long. Mesothorax
about one and one-half times as broad as prothorax. Wing-pads extending to distal
margin of eighth abdominal segment, fore pair not quite so far. Abdomen widest at
third and fourth segments, tapering from there to obtuse apex. Posterior edge on
ventral side of segment IX with four strong spines resembling a meat fork. This is
apparently the cremaster. Legs stout. Entire body with numerous inconspicuous
white hairs. (PI. I, fig. 6.)

Length of head 0.13 mm., width 0.15 mm.; length of prothorax 0.13 mm., width
0.2 mm.; width of mesothorax 0.28 mm.; width of abdomen 0.31 mm.; total length
1.26 mm. Length of antennal segments: I 33ju, II 45;j, III 63/z, IV 54/*, V 33^!!,
VI 66//, VII 9fi, VIII 12/z, total 0.31 mm. Color dark brown; tarsi light brown to
yellow. Head slightly wider than long, cheeks arched, anterior margin angular, back
of head transversely striate and bearing a few minute spines and a pair of very long
prominent spines between posterior ocelli. Eyes prominent, oval in outline, black
with light borders, coarsely faceted and pilose. Ocelli approximate, yellow, margined
inwardly with orange-lirown crescents, the posterior ones approximate to, but not
contiguous with, light inner borders of eyes. Mouth-cone pointed, tipped with
black; maxillary palpi three-segmented; labial palpi two-segmented, basal segment
very short. Antennse eight-segmented, al^out two and one-half times as long as head,
uniform brown except segment III, which is light ])rown; spines pale; a forked sense-
cone on dorsal side of segment III, with a similar one on ventral side of segment IV.
Prothorax about as long but wider than head ; a weak spine at each anterior and two
large, strong ones on each posterior angle; other spines not conspicuous. Mesothorax
with sides evenly convex, angles rounded; metanotal plate with four spines near front
edge, inner pair largest. The mesonotal and metanotal plates are faintly striate.
Legs moderately long, uniform brown except tibiae and tarsi, which are yellow.
Spines on tip of fore and middle tibiae weak; several strong spines on hind tibiae.
Wings present, extending l)eyond tip of abdomen, about twelve times as long as
wide, pointed at tips; costa of forewings thickly set with from 29 to 33 quite long
spines; fore vein with 12 to 15 arranged in two gi-oups of 3 and 6, respectively, on
basal half of wing and a few scattering ones on distal part; hind vein with 15 or 16
regularly placed spines; costal fringe on fore wing about twice as long as costal spines.
Abdomen subovate, tapering abruptly toward the tip from the eighth segment;
longest spines on segments 9 and 10; abdomen uniform brown, connective tissue
yellow. (PI. I, lig. 1.)

I

22 BULLETIN 17.3, U. S. DEPAETMENT OF AGRICULTURE.

SYSTEMATIC POSITION.

The pear tliri])s belongs to that suborder of the Thysanoptera
called Terebrantia, which differs from the other suborder, the
Tubulifera, in the possession by the female of a sawlike ovipositor;
also, the terminal segments of the abdomen are conical and the wings
are not equal in structure, the fore pair being the stronger. The mem-
brane of the wings, also, has microscopic hairs. This species is placed
in the family Thripidse and is separated from the vEolothripidse
in that the antennse usually have from 6 to 8 segments, the wings
usually are narrow and pointed at the tips, and the ovipositor is
dowmcurved. It is placed in the genus Tseniothrips of this family
because the body is free from reticulation and the abdomen not closely
pubescent; the head nearly or quite as long as wide, with a pair of
long bristles between the anterior and posterior ocelli; the cheeks
swollen, curving abruptly to the strongly protruding eyes; the
antennse eight-segmented, with the last two segments (the style)
shorter than the sixth; the maxillary palpi three-segmented, the
prothorax very slightly, if at all, shorter than the head, with two
long bristles at each posterior angle; the fore tibiae unarmed; the
bristles on the veins of the forewings not equidistant, and the last
abdominal segment of the female conical and without a pair of short,
stout bristles on the dorsal surface.

Until recently this species was placed in the genus Euthrips Tar-
gioni-Tozzetti, which most American autl).ors had used in the sense
of Physothrips and Odontothrips, Tseniothrips and Frankliniella.
Hood ^ has recently shown that the name Euthrips Targioni-Tozzetti
(1881) was first used in a subgeneric sense as a substitute for the name
Thrips, which had been used for a subgenus of Thrips Linne (1758),
and that it is consequently a synonym of that genus. The pear
thrips he places in the genus Tseniothrips Amyot and Serville, the
orange thrips in Scirtothrips Shull, and, partly following Karny,^
the various other species formerly assigned to Euthrips in the genera
Physothrips, Odontothrips, and Frankliniella.

ANATOMY.3

OVIPOSITOR.

Tlie ovipositor is attached to the ventral side of the eighth and
ninth abdominal segments and is composed of four distinct plates,
the under pair attached to the eighth segment and the upper or
posterior pair to the ninth abdominal segment. The ovipositor in

1 Hood, J. Douglas. On the proper generic names for certain Thysanoptera of economic importance.
In Proc. Ent. Soc. Wash., v. 14, no. 1, p. 34-44, 1914.

2 Kamy, H. Revision der von Serville aufgestellten Thysanoptera Genera. In Zooloirische Annalen,
Bd. 4, Heft 4, p. 322-344, 1912.

3 For a description of the mouthparts see discussion under "Manner of feeding and type of mouth-
parts," p. 11-13.

THE PEAR THRIPS IN CALIFORNIA, 23

the pear thrips is curved downward. The passageway between the
plates is grooved so that the eggs can pass through readily. The
upper edge (of the upper plates) is fitted with sharp sawhke teeth,
while the lower plates have similar teeth for most of the way but
also bear a number of broad cutting teeth. The end of the ovi-
l)ositor is sharp and pointed. When this is inserted into the plant
tissues, the slit or opening is enlarged by the action of the hard ser-
rate edges of the ovipositor as it is worked up and down by the
rather powerful muscles of the abdomen. The ovipositor when not
in use is i)rotected in a sheath along the ventral side of the last two
seoinents of the abdomen.

The wings are long and slender, membranous, with a fringe of
fine hair u])on both the anterior and posterior margins, and are never
folded. Both pairs of wings are quite similar and when at rest are
laid back flat upon the abdomen, the pairs lying parallel in the Tere-
brantia. The wings of the family Thripid^e, to which the pear
thrips belongs, are slender, and taper from the base to the tip, which
is pointed; they bear a general resemblance to sabers. The veins
in the family Thri])idae are not so prominent as in the family ^olo-
thripidte, and only one or two longitudinal veins are present, the
cross-veins being very obscure.

The legs and feet of thrips form one of the chief characteristics
which separate this order from the various other orders of insects.
They are composed of the usual parts of an insect leg, namely, coxa,
trochanter, femur, tibia, and tarsus. There is nothing unusual in
the formation of the first four parts, the femur and tibia usually
being quite long and somewhat cylindrical. The tarsus is the most
pecuhar structure on the leg, and may be either simple or of two
segments, and usually ends in one or two claws. In the family
Thripidse, they belong to the former type. The remarkable bladder-
like structure, which for many years gave the name Physopoda to
this order, is protrusile from the end of the last tarsal segment. It
is i)resent in both adults and larvae. The end of the tarsus is cup-
shaped, and into this cup the dehcate membranous bladder is
attached. When the foot is at rest the bladder is invisible and is
withdraA\m into the end segment. The bladder is protruded and
brought into action when the adult is resting on some surface or
walldng around. The mechanism of the bladder has been partially
worked out by Jordon and Uzel, but as it is somewhat intricate it
will not be described here. If a swollen bladder is pricked or rup-
tured, the blood pours out and the bladder collapses quickly. The

24 BULLETIN 173, U. S. DEPARTMENT OF AGRICULTURE.

blood is probably what causes the protrusion of the bladder. Vari-
ous agencies have been used in ex])eriments to hinder the thrips
in walking about on the surfaces of the plants they are attacking,
with the view that if in some way the mechanism of the bladder was
affected, either by causticity or by absorption, the bladder would
not be able to perform its function, and the insects would fall from
any surfaces that were so treated. This has not been successful
from the writers' experience, as they have observed on numerous
instances thrips crawling around on sticky surfaces, even on tangle-
foot, which was to all appearances and to the touch very sticky.
This bladderlike formation is probably so deUcate that surfaces
which appear smooth or sticky or caustic to the naked eye and human
touch are rough and uneven to the thrips and are neither adhesive
nor caustic. The writers have never seen thrips stuck to any sur-
face by the ends of their tarsi, but only by their bodies, legs, or
wings. It is apparent that they are able to walk on practically
every kind of surface, especially after this treated surface has been
exposed to the atmosphere for a few hours.

LIFE HISTORY AND HABITS.

ADULTS IN SPRING.

EMERGENCE FROM GROUND.

The first form of the pear thrips to be seen by the orchardists durmg
the growing season is the adult (PI. I, fig. 1), which emerges from the
ground during the last winter months and the early spring. The
period in which they first appear upon the trees in Santa Clara,
Contra Costa, Solano, and Sacramento Counties is variable. Certain
sections in each territory are earlier than others and some orchards
are in advance of others in regard to blossoming conditions.

In the Santa Clara Valley during the year 1909 the first acKilt
thrips were collected February 15. (See Table IV.) By February
18 they were quite numerous in one of the orchards under observa-
tion and were common in all orchards by February 25. Maximum
emergence began about February 19 and lasted until March 18.
They continued to emerge until the first three days in April. In
Contra Costa County first thrips were out at the laboratory February
12 and in the field February 16, emerging in numbers by February
20. Maximum emergence was over by March 15 and aU were out by
March 27. During the season of 1910 the first thrips taken in the
field in Santa Clara County were observed on February 7, while the
first in emergence cages appeared on February 9. They were common
in the field from P'ebruary 15 on. Thrips appeared in maximum
numbers from the cages (see fig. 5) beginning February 22 and
ending March 10, with the last stragglers coming out as late as
March 20. The emergelice season for 1911 at first gave promise

THE PEAR THRTPS IN CALIFORNIA.

25

of being very early, as the first thrips were found in the field on
January 29 and in the emergence cages February 1 ; but the heavy
rains following in February and March caused it to be very back-
ward, so that thrips were not common in the field until March 14,
which was about the time of the true maximum emergence.

In Contra Costa County during the season of 1909 the maximum
number of thrips emerged in cages, which were put in the ground
in the yard at the laboratory, from February 23 to March 4. (See

Fig. 5. — Type of soil cage used for soil samples in obtaining emergence records
of the pear thrips at San Jose, Cal. (Original.)

Table VI and fig. 7.) In cages placed under trees (see fig. 6) in the
field the thrips emerged in maximum numbers from February 26
to March 12 (see Table V and fig. 8). During the spring of 1910 the
first thrips found to emerge in the cages at the laboratory were out
on February 18 (see Table VI and fig. 9) and in the field cages on
February 21, reaching a greater daily emergence by March 1, and
contmuing to emerge in considerable numbers until March 15, the
maximum emergence being March 7 (see Table V and fig. 10). By
comparing figures 7 and 8, which show the emergence records for

73390°— Bull. 173—1.5 4

26

BULLETIN 173, U. S. DEPARTMENT OF AGRICULTURE.

1909, with figures 9 and 10, showing the record for 1910, it will be
seen that the time of emergence in any considerable numbers was
much shorter in 1910 than was the case in 1909. No actual daily
emergence records were kept in 1911, but no thrips were found in.
the field untU February 18 and then only very few in one early
almond orchard. On February 24 a few scattering specimens were
found in two pear orchards. Not until March 12 were they appearing
in any noticeable numbers, but the emergence was very rapid after
this, reaching the maximum between March 15 and 20. The emer-
gence of adults was mostly over by March 30.

Fig. G.— Type of wooden cage used for' field emergence records of the pear thrips in orchards at
Walnut Creek, Suisun, and Courtland, Cal., 1909-10. (Original.)

Emergence records and field observations in the Suisun Valley of
Solano County (see Table VII and fig. 11) show that for the season
of 1910 thrips came out of the ground in numbers on about the same
dates as for Contra Costa County. They were out in numbers in the
Courtland district of Sacramento County from two to four days
earlier. Further observations in 1911 showed the emergence in
these two sections to be about the same tune as for Contra Costa
County.

Records of the emergence for the years 1909, 1910, and 1911 are
summarized in Table IV. From this table it will be seen that in
Santa Clara County in 1909 most thrips appeared on March 3 while
in 1910 March 4 yielded the highest number, with March 3 and 2

THE PEAE THRIPS IN CALIFOENIA.

27

following close behind. The increase in emergence during the season
1909 (fig. 12) and the tapering off in the same year was more gradual

300

275

1

2SO

225

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200

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Fig. 7.-Curve illustrating emergence of adult pear thrips at laboratory, Walnut Creek, Cal., 1909.

(Original.)

than during the season 1910 (fig. 13). This difference was most
probably mfluenced during the latter season by the temperature.

/^ /6 /& 20 22 34 26 28

^ ^ 6 G /O /2 /4 /e /& 20 22 24 26 28'

Fig. 8.-Curve showing emergence of pear thrips in cages under trees in held at Wahiut Creek, Cal.,

1909. (Origmal.)

RELATIO.V OP EMERGENCE TO TEMPERATURE AND RAINFALL.

The average mean temperature for February and March, 1911, or
the two months when practicaUy aU of the thrips emerged, was

28

BULLETIN 173, U. S. DEPAKTMENT OF AGRICULTURE.

50.7° F., or about the same as in 1909, and the emergence probably
would have been very similar to the emergence for that year but
for the abnormal precipitation in February and March, especially
in the latter month.

1000
950
900

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750
700
650
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350
300
?50
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Fig. 9.— Curve showing emergence of adult thrips at laboratory, Walnut Creek, Cal., 1909.

(Original.)

Table U.—Mean temperatures for the months of February and March, 1909, 1910, and

1911.

"F.

Mean maximum temperature for month of February, 1909 59. 2

Mean minimum temperatiu-e for month of February, 1909 42. 2

Average mean temperature for month of February, 1909 51. 0

Mean maximum temperature for month of March, 1909 60. 0

Mean minimum temperature for month of March, 1909 40. 0

Average mean temperature for month of March, 1909 50. 0

Mean maximum temperature for month of February, 1910 58. 8

Mean minimum temperature for month of February, 1910 38. 5

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THE PEAR THRIPS IN CALIFORNIA.

29

Average mean temperature for month of February, 1910 49. 0

Mean maximum temperature for month of March, 1910 66. 2

Mean minimum temperature for month of March, 1910 44. 5

Average mean temperature for month of March, 1910 55. 0

Mean maximum temperature for month of February, 191 1 56. 5

Mean minimum temperature for month of February, 1911 37. .3

Average mean temperature for month of February, 1911 46. 9

Mean maximum temperature for month of March, 1911 63. 3

Mean minimum temperature for month of March, 1911 46. 0

Average mean temperature for month of March, 1911 54. 6

2200
Z/OO
2000
/900

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700

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300
200

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Fig. 10.— Curve showing emergence of adult pear thrips in cages under trees in field, at Walnut Creek,

Cal., 1910. (Original.)

It will be seen from the temperature records (Table II) that while
February, 1909, had 2 degrees higher average mean temperature
than February of 1910, March of 1909 had 5 degrees less average
mean temperature than March of 1910, making the average mean
temperature for the months in which most of the adults emerged
50.5° F. in the year 1909 and 52° F. in the year 1910. Another factor
which held back the emergence greatly the former year was the

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30

BULLETIN 173, U. S. DEPARTMENT OF AGEICULTUKE.

greater rainfall, the month of February, 1909, havmg 4.87 inches
precipitation while February of 1910 had only 0.83 of an inch.

A comparison of the amount of precipitation for the three years
1909, 1910, and 1911 (see Table 111) shows a large amount for 1909,

650

550
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300
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S /e 20 22 24 2€ 2'& 2 ■^ 6 & /O /2 /4 /6 /& 20 22 24 26 2e

Fig. 11. — Curve showing emergence of pear thrips at Suisun, Cal., 1910. (Original.)

which with the low average mean temperature for the two emergence
months caused the emergence to be drawn out. The season 1911
was very abnormal in the large amount of precipitation, especially

/300

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\

^

/O /Z /4 /€ /a 20 22 2-* 26 Z

/='£rB/?u^^y

e 2 4 6 e /O /2 /t /6 /e 20 2

2 2-

42

62

9 S.

±

'^A

1

Fig. 12. — Curve showing emergence of pear thrips at San Jose, Cal., 1909. (Original.)

during the latter part of February and early March, causing a late
blossoming season, and holding the thrips back to such an extent
that comparatively little injury was caused by the adults.

THE PEAR THRTPS IN CALIFORNIA.

31

Table III. — Total precipitation for the years 1909, 1910, and 1911 at San Jose, Cal.,

labor ator II .

Month.

Precipitation in inches.

1909

1910

1911

February

Marcli

4.87
2.77

0.83

2.84

2.03
6.26

One curious fact about the emergence for 1911 was the double
maximum, one the latter part of February, from the 18th to the 26th,
and another from the 8th to the 15th of March. (See Table IV and

4ZOO

^lOOO

1

3800

A

3600

3^00

li

3200

"

3000

^

2300

2€00

Z400

ZZOO

2000

/ffOO
/600

1

JZOO
fOOO
ffOO
600

200

o

I

I

I

)

I

i

/

\

A

J

)

L

^

•^y

•^

/

V

^

^^

/o /z /^ /6 /a 20 22 2^ ze 2'e 2 ^ e e /o /z i^ /e /a zo zz 24 26 za

Fig. 13.— Curve showing emergence of pear thrips at San Jose, Cal., 1910. (Original.)

fig. 14.) From February 26 to March 11, inclusive, it rained every
day from 0.02 of an inch to as much as 2.45 inches. Probably a
number of the thrips which emerged in February were killed by the
heavy rains in early ]\Iarch, or at least were not permitted to cause
much injury. The pear thrips emerges from the ground during rainy
weather, but not in such great numbers as during warm, sunshiny
days, which was the case during the latter part of February and the
early part of March of the year 1910. Whether the soil is clean or
covered with weeds and grass at this time of year influences the time

32

BULLETIN 173, U. S, DEPARTMENT OF AGEICULTUEE.

of emerji:en.cc ])y soiiio two or three days. This was particularly
noticeable in pear orchards used in cultivation experiments in Contra
Costa and Solano Counties. In the plowed portions which were free
from weeds, the surface dried out and warmed up more rapidly and
thrips came out in numbers and into the trees tliree days earlier than
on the unplowed part of the orchard, which was covered with a rank
growth of vegetation. The shading of the soil by the vegetation
seems to result hi holding the thrips within the ground several days
later, or else they spend some time on bhis succulent growth before
going into the trees.

The following tables give the emergence records for the years 1 909
1910, 1911, and 1912 for Santa Clara County (San Jose, Table IV);

ZOO
/SO
/So
fVO
/€0
/SO
/40
/30
/20
//O

/oo

90

ao

70

eo
so

40

3o
zo
/o

\

\

1

\

I

\

\

i

\

/

\

^

1

s

/

\

y^

\

1

s

\

1

\

"^

^

\

_^

--

^

/o

/^ /8 22 26

ysj.

/O /4 /ff 22 26 30,

Fig. 14. — Curve showing emergence of pear thrips at San Jose, Cal., 1911. (Original.)

y

for 1909 and 1910 in Contra Costa County (Wahiut Creek, Tables V
and VI), and for 1910 in Solano County (Suisun, Table VII). These
tables show the total number of thrips emerging on the given dates
from soil in the cages. For the San Jose records, all the cages con-
taining soil samples from infested prune orchards were placed in the
ground at the laboratory. For the records in Contra Costa and
Solano Counties, part of the cages were brought to the laboratory
and buried in the ground and part were left in the ground under the
trees in infested orchards. (See fig. 6 for type of cage used for the
field emergence records in the northern counties.) It was not pos-
sible to take the emergence every day, but, so far as possible, counts
were made at regular intervals.

THE PEAR THRIPS IN CALIFORNIA.

33

Table IV. — Total emergence of pear thrips from all the cages kept at the laboratory at
San Jose, Santa Clara County, Cal., during 1909, 19 W, 1911, and 1912.

Number

Number

Number

Number

Number

Number

Number

Number

of thrips

of thrips

of thrips

of thrips

of thrips

of thrips

of tlirips

of thrips

Date

emerging

emerging

emerging

emerging

Date.

emerging

emerging

emerging

emerging

in 1909

in 1910

in 1911

in 1912

in 1909

in 1910

in 1911

in 1912

from 18

from 18

from 4

from 4

from 18

from 18

from 4

from 4

cages.

cages.

cages.

cages.

cages.

cages.

cages.

cages.

Feb. 1

0

0

2

1

Mar. 9

776

144

1

366

2

0

0

7

1

10

497

100

32

442

3

0

0

0

0

11

498

73

54

81

4

0

0

0

0

12

338

179

71

83

5

0

0

0

1

13

313

45

56

161

6

0

0

1

5

14

248

20

22

313

7

0

0

28

3

15

279

7

17

433

S

0

0

5

6

16

259

4

9

239

9

0

25

1

9

17

152

20

2

158

10

0

18

4

9

18

42

7

4

596

U

0

16

1

9

19

61

2

0

209

12

0

16

22

21

20

28

2

0

144

13

0

4

"o

15

21

2

0

3

106

U

0

88

0

33

22

6

0

6

114

15

18

22

11

37

23

13

0

1

103

16

0

27

5

65

24

3

0

1

68

17

52

34

2

104

25

2

0

0

52

18

192

33

17

242

26

3

0

1

39

19

192

14

62

490

27

7

0

1

38

20

169

23

41

384

28

7

0

0

61

21

75

62

32

325

29

0

0

0

17

22

119

129

33

440

30

2

0

0

14

23

135

375

25

422

31

0

0

0

14

24

552

272

26

515

Apr. 1

3

0

0

28

25

459

297

18

800

2

0

0

0

19

26

444

455

8

504

3

1

0

0

9

27

414

574

0

762

4

0

0

0

7

28

781

657

0

1,694

5

0

0

0

4

29

1,169

6

0

0

0

4

Mar. 1

7si"

"'i,'975"

6""

1,721

7

0

0

0

26

2

535

3,592

0

276

8

0

0

0

5

3

1,299

3,011

2

284

9

0

0

0

3

4

714

4,217

4

399

10

0

0

0

1

5

508

1,402

0

400

11

0

0

0

1

6

362

1,595

0

585

12

0

0

0

0

7
8

438
219

539
275

1
21

1,227
1,052

Total..

11,998

20, 350

660

17,968

Table V. — Emergence of pear thrips from cages placed in ground under trees in pear and
prune orchards. Walnut Creek, Contra Costa County, Cal.

Number of

Number of

Date.

thrips

Date.

thrips

emergmg.

emerging.

1909.

1910.

Feb. 13

0

Feb. 21

1

16

20

23

4

19

37

25

23

22

30

27

36

26

110

Mar. 1

56

Mar. 2

615

3

237

5

679

5

1,170

10

752

7

2,110

12

273

9

892

16

65

11

1,773

20

33

13

557

22

4

15

198

27

11

17

71

19

3

21

6

27

0

34

BULLETIN 173, U. S. DEPAKTMENT OF AGRICULTUKE.

Table VI. — Emergence of pear thrips/rom soil samples taken from orchards in December
and January and kept i)i cages at laboratory, Walnut Creek, Contra Costa County, Cal.

Number of

Number of

Date.

thrips

Date.

thrips

emerging.

emerging.

1909.

1910.

Feb. 12

3

Feb. 18

11

15

42

20

16

It)

56

22

0

17

38

24

12

18

66

26

30

20

89

28

75

23

125

Mar. 2

377

25

185

4

918

27

246

6

937

Mar. 1

196

8

165

4

237

10

114

7

51

12

47

10

52

14

0

14

13

16

4

19

0

22

0

Table VII. — Emergence records of pear thrips for Suisun, Solano County, Cal., 1910.

Emergence of thrips

Emergence of thrips
from cages placed
in ground under
trees in orchards,
Suisun, Cal.

from soil samples
talven from or-
chards in Decem-
ber and January
and liept in cages
at laboratory, Sui-

sun, Cal.

Number of

Number of

Date.

thrips

Date.

■ thrips

emerguig.

emergmg.

Feb. 17

3

Feb. 16

1

19

0

17

3

21

0

18

2

23

0

19

6

25

1

20

1

27

20

21

1

Mar. 1

47

22

4

3

121

23

2

10

484

24

5

16

1

25

11

26

11

27

14

28

41

Mar. 1

105

2

247

3

243

7

612

12

357

16

82

19

8

The latest dates on which adult thrips wore collected in the field
were about the same for the years 1909 and 1910, the last ones being
found from April 15 to April 25. In 1911 living adults were found
as late as the middle of May. They were very scarce, however, after
May. The number of living adults as a rule decreases rapidly after
April 1 .

The time adults will feed before they begin ovipositing varies.
Those individuals which emerge early and which do not have a suit-

THE PEAK THRIPS IN CALIFOENIA. 35

able place for ovipositing will feed from 15 to 20 days before placing
any eggs, while individuals which emerge at a later date, as, for in-
stance, from March 5 to 20, do not as a rule feed more than one or
two days before depositing eggs. Individuals which were taken from
emergence cages and placed in mica chimneys were observed ovi-
positing the day following their emergence. It is possible that in
the field thrips begin depositing eggs more quickly on certain varie-
ties of fruits than on others. This would be governed very largely
by the presence or absence of available tissue suitable for oviposition.
For this reason on the early blooming varieties of cherries thrips prob-
ably feed for a shorter time before oviposition commences than is the
case with other fruits.

PERIOD OF EGG LAYING FOR INDIVIDUALS.

The egg-laying period for individuals does not usually last for
more than three weeks. Individual thrips confined in mica chimneys
on March 5, 1910, did not deposit any eggs after the latter part of
March. The full period of egg laying for the entire brood throughout
all the infested areas extends from about February 20 until near
April 10, or a period of six to seven weeks.

LENGTH OF LIFE OF ADULTS.

Adult thrips confined in vials without food lived on an average
tliree days, while those confined in vials with food lived about two
weeks. Adult thrips confined on the trees within mica chimneys
lived from three weeks to one month. The length of life of individuals
in the field has not been observed accurately, but probably ranges in
duration from three weeks to one month and a half.

RELATION OF EMERGENCE TO BLOSSOMING OF TREES.

The emergence period extends from early February to early April
and is closely associated with the blossoming periods for the different
varieties of fruits. Budding and blossoming of the different fruits
is as follows: Almond buds begin to swell during the latter part of
January and early February, and this variety of fruit is in iidl bloom
between Februar}^ 8 and 24. Apricots show first blossoms from Feb-
ruary 12 to 23, and most varieties are in full bloom by from March 3
to 10. Peaches show first blossoms about February 23 and many
varieties are in full bloom from March 8 to March 17. Black Tar-
tarian cherries reach full bloom by March 15 to 20, while the Royal
Anne variety has not at that time opened its buds. French prune
buds are beginning to swell between March 8 and 1 1 and first blos-
soms appear by March 20. They are usually in full bloom between

36 BULLETIN 173, U. S. DEPAKTMENT OF AGRICULTURE.

March 26 and April S. The Sugar and Imperial varieties precede the
French by about one week. Bartlett pear buds begin to swell the
last of February or the first of March, the first clusters usually spread-
ing from March 10 to 15 and arc in full bloom for quite an indefinite
period between March 20 and April 10. Pears, prunes, and cherries,
which are spreading their bud clusters j ust after the maximum numbers
of tlirips are coming from the ground, are the fruits most seriously
injured by the pear thrips.

MIGRATORY HABITS.

Evidences of the migratory habits of the pear thrips have been
noticed at times during the last three or four years. However, no
definite observations concerning their migration had been made until
the year 1910. Hitherto it had been noted that in some orchards
the adults were very numerous early in the season and doing extensive
damage. Later observations at an interval of four or five days
showed very few adults present, and the entire orchard had the
characteristic browned and burnt appearance. It was quite evident
that after destroying aU the fruit buds the thrips had migrated to
other orchards in search of food.

It was possible to obtain more definite Imowledge regarding
migration in the year 1910 than had heretofore been known, for the
reason that the thrips were unusually numerous throughout all the
infested areas that year and weather conditions were such that
practically the entire brood emerged from the ground in a few days.
Also, following their emergence in great numbers, the weather was
sufficiently warm that the destruction of the fruit buds in the various
orchards was accomplished in much shorter time than is usually the
case. Observations so far indicate that thrips migrate in swarms
only on bright , warm days. Numerous instances of supposed migration
were mentioned to the writers at various times during the season, the
reports stating that the pear thrips were flying in swarms, but most
of the cases reported lacked authentic evidence to bear them out,
such as the saving of specimens. However, in the afternoon of March
28, 1910, the junior author drove out from San Jose toward Saratoga
and had great difficulty in keeping both hands on the reins on account
of the great numbers of thrips which, flying through the air, filled his
eyes and covered his clothes. The prevailuig direction of the wind
on this day was not observed; no distinct migration or swarm was
noted, however, although individuals were numerous flying across the
road and could be readily seen when the observer looked toward the
sun. They were more numerous on roads running north and south,
and extended over a territory of 4 or 5 miles ; they were the most numer-

THE PEAR THRIPS IN CALIFORNIA. 3t

ous at the west end of Hamilton Avenue and alon<^ the San Tomas and
Santa Clara and Los Gatos Roads.

On March 30, 1910, still more definite information was gained, and
this is probably the most unique record of thrips migration which has
yet been taken. The day was bright and rather warm and ended
with the evening warm and a gentle breeze blowmg from the south.
Mr. E. L. Fellows, who was in Santa Clara on this day, started home
about 5 o'clock in the afternoon. About 5.15 p. m., out on the
Saratoga Road, he noticed a number of small, black insects which
covered his face and hands, his hat and clothes, and got into his eyes.
When he was one-fourth of a mile north of Meridian Corners he met
the thickest part of the swarm, which appeared literally like a black,
glistening, seething mass moving up and down like heat waves.
From this place the insects became less numerous as he went toward
home, which he reached about 6 p. m. He thought the swarm to be
about 8 miles long and 4 miles wide, from 4 to 15 feet high, moving
at the rate of about 10 miles per hour northward toward vSan Fran-
cisco Bay. As he was not sure concerning the identity of this insect,
he gathered several hundred specimens in a paper bag and submitted
them to the junior author for identification. They were found to
be the pear thrips, Tseniothrvps pyri. This same swarm was noticed
by the junior author and by several fruit growers, but they did not
have the opportunity to view the whole swarm as did Mr. Fellows.

Continued observations during the season of 1910 showed that the
usual time for migration was from 3 to 6 p. m. on bright, warm days
during the latter part of the period of maximum oviposition, which
was also about the time many orchards have been so badly injined
that the trees will not bloom.

This migratory habit is undoubtedly influenced chiefly by a desire
for a new supply of food, better places for deposition of eggs, and
suitable weather conditions, especially the temperature. The
direction in which thr'ps will migrate depends upon the direction the
wind is blowing, and the distance at which suitable feeding places
are found.

No distinct migration of the whole brood has ever been observed,
such as is the case with some species of Orthoptera. The migra-
tion from certain badly infested orchard locahties has been in-
fluenced, without doubt, ])y the early destruction of the fruit buds
in these orchards. Many instances are known where thrips are
numerous and their injury severe in an orchard one year and not
very numerous the succeeding year, but they are usually higlily
injurious again the third year. This phenomenon is more noticeable
in pear than in prune orchards, due probably to the fact that a pear

38 BULLETIISr 113, U. S, DEPARTMENT OF AGKICULTTJEE.

orchiird in which all fruit buds have been destroyed is poor feed-
ing ground for both adults and larvae and reproduction is at the
minimum under such conditions. This reappearance in damaging
numbers the third year makes it evident that the orchardists should
not allow their orchards to go untreated. It should be noted that the
years 1907 and 1910 were the only seasons in which the pear thrips
migrated to any great extent. No migration was known in the
season of 1911, although it was watched for.

MANNER OF REACHINO TREE TOPS FROM GROUND.

Most of the adults when emerging probably crawl around for a
while on the ground until their wings get sufficiently dry and then
fly up into the tree. Some, however, must undoubtedly crawl up the
trunk, as a few have been caught by tanglefoot bands. This, however,
can not be used as a method of control, since very few go up this way;
moreover, the thrips would not be caught unless the bands were
renewed every day or so, because the bands do not remain sufficiently
sticky after a short exposure to the atmosphere.

REPRODUCTION.

According to Bagnall ^ an example of the male pear thrips was found
by him among some specimens of this species taken from plum
blossoms at Evesham, England, and submitted to him by Mr. Col-
linge, director of the Cooper Research Laboratory at Berkhamstead.
His only description is that "It is much smaller than the female and
the wings considerably overreach the tip of the abdomen." This is
the first report of the existence of the male of this species, and
in Cahfornia very extensive observations by the writers and other
workers have failed to show a single male, and the only type of
reproduction known is by parthenogenesis. In aU of the hfe-history
experiments to secure data upon the length of the egg stage indi-
vidual females were taken directly from the emergence cages and
isolated. It is highly probable that practically all of the eggs
which are deposited hatch, as no sterile eggs have ever been found.

OVIPOSITION.

Moulton 2 states that he has observed the adult in ovipositing
to make first a hole in the epidermis of the plant tissue with the
mouth before depositing the egg. Repeated observations by the
writers of a large series of adults during oviposition have failed to

1 Bagiiall, Richard S. A contribution to our knowledge of the British Thysanoptera (Terebrantia), with
notes on mjurious species. In Jour. Econ. Biol., v. 4, no. 2, p. 33-41, July 7, 1909. See p. 39.

2 Moulton, Dudley. The Pear Thrips (Euthrips pyri Daniel). U. S. Dept. Agr., Bur. Ent., Bui. 68,
pt. 1, rev., p. 7, Sept. 20, 1909.

THE PEAR THRTPS IN CALIFORNIA. 39

show a single one going througii this procedure. The usual method
as shown by observations during the season of 1910 is as follows:
The female starts the ovipositor into the tissue by working the
abdomen up and down, gradually forcing the ovipositor its full length
into the tissue. After this is done the thrips remains c[uiet for a
short interval while the egg is passing out between the plates of
the ovipositor. When finished, the female vibrates her antennae and
jerks out the ovipositor. Tlie prevaihng posture durmg the whole
period of oviposition is with the abdomen arched and the legs spread
apart wider than when in walking. The average time required for the
operation by a number of individuals observed during the season of
1910 ranged from three to five minutes. After depositing an egg the
female usually resumes feeding for a short interval, but some indi-
viduals have been observed to deposit two and three eggs in suc-
cession without any feeding between times. The number of eggs
that a female can deposit in a day is probably not over seven or eight,
as the abdominal cavity is not large enough to hold more at one time.

EGGS.

PLACE OF DEPOSITION.

The eggs are always placed in the tenderest portions of the plant
tissue, such as exposed blossoms, fruit stems, leaf stems, ribs of the
leaves (preferably the midribs), and the leaf edges. Still others are
placed in the young fruits. The pear thrips apparently prefers to
oviposit upon cherries if a cherry tree is at hand, as the fruit and leaf
stems, on account of their length and tenderness, offer excellent places
for oviposition without making it necessary for the thrips to move
over a large area. However, the small prunes and the stems, as also
the stems and midribs of the young leaves of both prunes and pears,
are well suited for oviposition by this species. The counts in Table
VIII were taken upon leaf stems and fruit stems of French prunes and
show the comparative percentage of eggs deposited in each; they also
show the inabihty of the different spray mixtures to kill the eggs
within the plant tissues, as these stems in question had been sprayed
two days previously with a combination of tobacco extract and dis-
tillate emulsion.

40

BULLETIN IT.i, U. S. DEPARTMENT OF AGEICULTURE.

Table VIII. — Comparative percentage of eggs deposited in fruit steins and leaf stems of
French prunes, San Jose, Cal., season of 1910.

No. of ob-
servation.

Number
of eggs in
leaf stems.

Number

of eggs in

fruit

stems.

No. of ob-
servation.

Number
of eggs in
leafstems.

Number

ofegsrsiii

fruit

stems.

1

2

7

44

1

12

2

1

10

45

0

11

3

5

5

46

7

s

4

0

12

47

3

s

5

2

13

48

7

9

6

1

6

49

5

11

7

3

8

50

2

9

8

0

S

51

12

9

9

0

8

52

10

11

10

1

9

53

2

9

11

1

8

54

3

10

12

2

10

55

7

12

13

2

4

56

0

6

14

5

6

57

9

10

15

3

10

58

5

11)

16

2

U

59

12

4

17

0

5

60

5

11

18

3

12

61

0

17

19

3

10

62

6

9

20

1

S

63-

2

13

21

0

6

64

4

9

22

0

3

65

5

12

23

3

10

66

8

6

24

1

9

67

0

7

25

1

r,

68

11

8

26

2

13

69

8

9

27

1

10

70

5

16

28

1

5

71

9

7

29

1

9

72

3

S

30

2

8

73

2

9

31

0

16

74

2

7

32

2

8

75

9

11

33

2

4

76

17

S

34

1

15

77

6

10

35

0

9

78

11

4

36

0

11

79

12

S

37

1

7

80

9

14

38

4

19

81

8

9

39

7

16

82

2

S

40

2

13

83

1

11

41

5

7

84

0

11

42

3

12

43

3

9

Total...

299

786

It will be seen from this table, that the average number of eggs
placed within fruit stems of prunes is more than twice the number
placed in the leaf stems. In pears a very large proportion of eggs is
placed in ribs and veins of leaves and a comparatively smaller per-
centage in the fruit stems.

FIRST EGGS.

The first eggs that were noticed in the vicinity of San Jose and in
Contra Costa County were placed about March 10 for the season of
1909, while most eggs were being placed about March 15 to 25, and
the last eggs in early April. The first eggs were deposited in 1910 in
the field about March 9, while maximum oviposition was from March
IS until about April 2. The last eggs were observed to be placed in
the field toward the middle of April. In the interior counties, espe-
cially Sacramento and Solano Counties, eggs were being deposited in
large numbers by March 15, and continued to be deposited in num-
bers until the latter part of March, a few being found in early April.

THE PEAR THRIPS IN CALIFORNIA.

41

LENGTH OP E<i(; STAGE.

Moulton ^ records the length of the egg stage to bo approximately
four days, but detailed observations during the season of 1910 at San
Jose show it to be considerably longer. The length of the egg stage
was first ascertained by inclosing twigs with paper bags before thrips
emerged so as to get no outside infestation. Later, when thrips were
ovipositing in the field, a considerable number of adults were placed
in mica chimneys which had been specially constructed to fit over the
twigs in such a manner as to give them as nearly natural conditions
as possible, and to permit the eggs to remain in hving plant tissue
because they usually dried out when the twigs were removed from the
tree. These chimneys were made by sewing pieces of strong white
cloth in the shape of tubes about 5 or 6 inches long and gluing one
end of a cloth tube thus made to each end of the mica chimney.
Wlien placed upon the tree, ends of the cloth were tied securely
around the twig so that no insects could get in from the outside.
The thrips kept for oviposition remained in the cages over night and
were removed the next day. To make sure that none would remain
in to continue ovipositing, new cages were placed on the twigs in each
case. Table IX shows the length of the egg stage.

Table IX. — Length of egg stage of the pear thrips, San Jose, Cal., 1910.

Cage
No.

Date de-
posited.

Date
hatched.

Niiinber

of eggs

hatched.

Length
of egg
stage.

Average
mean

tempera-
ture.

Prevailing
weather.

Days.

° F.

I

Mar. 10

Mar. 16

25

6

56

Cloudv.

17

6

7

57

Do."

18

9

8

58

Do.

19

8

9

57

Do.

20

3

10

57

Do.

22

10

12

52

Do.

23

3

13

52

Do.

24

1

14

52

Do.

a

Mar. 10

Mar. 16

13

6

56

Cloudy.

17

27

7

57

Do.

18

30

8

58

Do.

19

3.5

9

57

Do.

20

8

10

57

Do.

III

Mar. 10

Mar. 16

27

6

56

Cloudy.

17

4

7

57

Do.

18

9

8

58

Do.

19

14

9

57

Do.

20

10

10

57

Do.

22

4

12

52

Do.

23

1

13

52

Do.

24

1

14

52

Do.

TV

Apr. 7

Apr. 14

3

7

55

Clear.

V

Mar. 29

Apr. 5

1

7

56

Clear.

8

1

10

56

Do.

10

1

12

56

Do.

VI

Mar. 29

Apr. 7

2

9

56

Clear.

^

9

4

11

56

Do.

10

1

12

56

Do.

12

1

14

55

Do.

I Op. eit., p. 8.

42 BULLETIN 173, U. S. DEPARTMENT OF AGRICULTURE.

Table IX. — Length of egg stage of the pear thrips, San Jose, Cul., 1910 — Continued.

Cage
No-

Date de-
posited.

Date
hatched.

Number

of eggs

hatched.

Length
of egg
stage.

Average
mean

tempera-
ture.

Prevailuig
weather.

VII
VIII

IX

X
XI
XII

Mar. 29
Mar. 29

Mar. 29

Apr. 6
Apr. 6
Apr. 6

Apr. 3

8

Apr. 7
8
9
10

Apr. 2
6
7
8
10
14

Apr. 12

Apr. 13

Apr. 13

2

Days.
5
10

9
10
11

12

4
8
9

10
12
16

6

7

7

° F.
56
56

56
56
56
56

57
56
56
56
56
55

54

54

54

Clear.
Do.

Clear.
Do.
Do.
Do.

Clear.
Do.
Do.
Do.
Do.
Do.

Cloudy.

Cloudy.

Cloudy.

SUMMARY.

Number eggs deposited.

Time
required for
incubation.

Number eggs deposited.

Time
required for
incubation.

1

Days.

4
5
6
7
8
9

34

Days.

10
11
12
13
14
16

1 . -..

7

66

24

44

4

49

4

61

1

For the 296 eggs under observation, the maximum length of the
egg stage was 16 days, and the minimum 4 days, making 8.3 days
the average time required for incubation.

The eggs of the pear thrips are undoubtedly affected by tempera-
ture conditions, but rainy weather as compared with clear weather
seems to make no difference when the mean temperature is the same,
as all eggs are embedded in the moist plant tissue and do not require
additional moisture from the atmosphere.

It is evident that all of the eggs are not in the same stage of develop-
ment at the time they leave the abdomen of the female, since eggs
deposited upon the same day ranged from 4 to 16 days in the length
of the egg stage. An examination of the average mean temperature
for the various cages shows usually several degrees less mean tem-
perature for a long egg stage in comparison with a short egg stage.

The maximum and minimum temperatures influencing the different
lots of eggs are given in Table X.

THE PEAR THRIPS IN CALIFORNIA.

43

Table X. — Maximum and minimum temperatures during -period of incubation for eggs
of the pear thrips, San Jose, Cal., 1910.

Date.

Mar. 10
11
12
13
14
15
K)
17
IS
19
20
21
22
23
24
25
26

Maxi-

Mini-

mum

mum

temper-

temper-

ature.

ature.

° F.

° F.

73

44

72

48

57

48

71

44

68

49

70

44

70

53

69

54

62

50

61

48

60

51

57

47

61

46

57

39

60

37

59

44

57

44

51

42

Dale.

Mar. 28
29
30
31

Apr. 1 .
2.
3.
4.
5.
6.
7.
8.
9.
10
11
12
13
14

Maxi-

Mini-

mum

mum

temper-

temper-

ature.

ature.

° F.

° F.

64

40

69

40

76

41

78

43

70

45

63

43

66

46

75

41

67

46

65

46

64

40

66

45

66

47

61

51

56

47

66

46

72

41

74

41

NUMBER OP EGGS DEPOSITED BY A SINGLE FEMALE.

Up to the season of 1910 only conjectures had been maae as to the
number of eggs a single female would (leposit, but by taking indi-
viduals as soon as they emerged and placmg them separately upon
twigs in the mica cages described under the heading "Length of egg
stage," the total progeny of a single female was ascertained — approxi-
mately, therefore, the total number of eggs possible for one individual
to deposit. Each indivichial was allowed to remain undisturbed on
the twigs inside the cage. After the eggs hatched the larvse were
removed and counted, yielding the following total number: Cage 1,
155 larvae; cage 2, 146 larvae; cage 3, 142 larvae; cage 4, 99 larvae;
cage 5, 117 larvae. The maximum number of eggs laid is 155,
the minimum 99, and the average 131.8. This is probably close to
the average number of eggs that would be deposited by a single female
out in the field, although some few long-lived individuals would
perhaps exceed 200 eggs.

DEPTH EGGS ARE DEPOSITED IN TISSUE.

The eggs are deposited within the plant tissue immediately under-
neath the outer epidermis and are inclosed by the tissue. The places
where they have been deposited can readily be found with the aid of
a hand lens because of the little swelhngs on the stems and by the scars
left whore the ovipositor had been inserted into the plant.

LARV^.

FIRST APPEARANCE.

The very first larvae appear on almonds, apricots, and the early
plums, usually about the 1st of March. Larvae begin to hatch on
prmies and pears the middle of March and usually are in maximum

44 BULLETIN 173, IT. S. DEPARTMENT OF AGRICULTURE.

numbers in the interior valleys of Contra Costa, Sacramento, and
Solano Counties the last of March and the first 10 days of April, while
tlie maximum number in Santa Clara County appear the first 15 days
of April and the last ones in all the infested ref>;ions are found some
time in early May.

TIME SPKNT IN FEEDINC.

The time spent in feeding, or the period required for the larvae to
obtain their growth, is from two to three weeks, for individuals. For
the whole brood — that is, from the time the first larvae are found on
any variety of fruit to the time the last ones are found in the trees —
a period of about two months and a half is spent, from the latter part
of February to the early part of May.

After the larvae have hatched and fed for some seven or eight days
they shed their skins, becoming more robust, and ovoid in shape, and
in this form they continue until they molt again into the prepupal
stage while in the ground. After the larvae have molted the first
time they remain upon the tree from ten days to two weeks before
becoming full grown and dropping to the ground. The total time
spent upon the tree is from two to three weeks.

LEAVING TREES AND ENTERING GROUND.

On leaving the trees the larvae do not crawl down but either fall or
are knocked off by rains or shaken off by winds. A large number
fall with the dropping calyces. Numerous instances were recorded
in the year 1910 in which heavy rains knocked off large numbers of
larvae, some of which reached their full growth by feeding upon
miner's lettuce, which was at the time the only vegetation growing in
this orchard; but many of these immature larvae were quite small and
failed to reach full growth, which is partly responsible for the smaller
number of adults in some sections the following year, 1911. The
young and only partially grown larvae that fall off the trees and do
not come in contact with any weed or grass in the orchard mostly
perish. Only the full-grown larv^ that fall to the ground in culti-
vated orchards work their way into soil Larvae that fall off normally
do not ascend the trees again, but in some cases in cherry orchards
where foliage was near the ground on the trunks of the trees many of
the larvae were noted to crawl back to lower foliage. This would not
be likely to occur on pears or prunes, where there is little or no
foliage near the ground.

THE PEAR THRIPS IN CALIFORNIA. 45

HABITS OF LARVyK IN THE GROUND.

After the larvse have pentrated, the soil to a sufficient depth they
hollow out for themselves a small oblong cell, the inner surface of
which is a hard, smooth wall, the cell proper being about one-half
inch long. These cells are made for safe places in which the larvae
may pupate or transform to adults. It is here they spend most of
the year.

DEPTH TO WHICH LARV.E GO IN THE GROUND.

The depth that larvae will penetrate the ground depends largely
upon the type of soil. Practically all of the larvae go below the 3
or 4 inches of a loose topsoil mulch and establish themselves at
various depths in the harder soil below. The depths at which larvae
are found in soils vary from 1 to 26 inches. Both of these are extremes
and very rarely contain many thrips. In Contra Costa, Solano, and
Santa Clara Counties from 50 to 95 per cent of the tlmps do not go
below 9 to 10 inches, the gravelly soil having the highest percentage
of the larvae nearest the surface. Some of the sedimentary soils
along the Sacramento River are very open and porous — a recent
alluvial containing a great deal of decaying vegetable matter. The
larvae in such soil may go much deeper, and in many cases they were
found in numbers 24 to 26 inches below the surface when none could
be found above this depth. Li other cases where these light soils
have a good heavy sod, thrips have been found in large numbers from
1 to 3 inches below the surface in the cells constructed among the
grass roots.

DEPTH TO WHICH LARV^ GO IN DIFFERENT SOILS.

An absolutely definite statement as to how deep larvae will go in
the various soils, such as gravelly, sandy, sandy loam, sediment loam,
and adobe, can not be made, and only comparisons can be given from
samples taken from these various soils. On account of the local
character of tlu"ips infestation it is important, when one is tiynng
to ascertain the depth of most of the larvae in an orchard, that several
samples be taken, to insure accuracy. The samples should come not
only from different parts of the orchard but also from various distances
and locations in the vicinity of the same trees. Soil samples for
determining the number of tlirips per square foot and the depth to
which the larvae go in the soil should be taken at about 2 to 4 feet
from the base of the tree.

The samples from which the records given in Table XI were made were
taken by sinking galvanized-iron cages into the soil and removing them
to the laboratory. The cages had a sliding fourth side which could be
be removed so that each layer could be examined by cutting off the
desired thickness and sifting the dirt upon a piece of black i^aper. The

46 BULLETIN 173, U. S. DEPARTMENT OP AGEICULTTJRE.

average depth to which larvae will penetrate m gravelly and sandy
loam soils is usually less than in heavy sedimentary loam. In those
soils which inchne toward the adobe type and in the distinctly adobe
soil the larvae usually go deeper. On account of the cracking of this
latter type of soil as it dries out in the spring, and the texture, which
is such as to prevent the making of a perfect soil mulch, suitable
places for niakmg the cell are not found so near the surface. In soils
which can be worked readily except in cases of silt deposits or an
abnormal amount of vegetable matter below the surface, very few
larvae, as a rule, penetrate to an unusual depth below the surface;
for this reason practically all the soils in the Santa Clara Valley that
are badly infested by tlu'ips are such as render possible the obtaming of
practicable results from early fall plowing. Table XI shows the com-
parative depth of larvae in a number of samples of soil taken from 10
orchards in Santa Clara County. While no sandy soil is present, these
samples represent fairly well the different types of soil of the Santa
Clara Valley.

THE PEAR THEIPS IN CALIFORNIA.

47

X

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0 o3
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35.34
57.19
72. 13
91.72
9S.26
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99.89
100. 00

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48

BULLETIN 173, U. S. DEPARTMENT OF AGEICULTURE.

In Contra Costa County the greater portion of the orchard area
is on the distinctively adobe soiJ. It is a noticeable fact that the
lan^fe penetrate this soil to a greater depth than they do the hard
gravelly soils, probably owing to the greater prevalence of cracks.
An examination of Table XII, which is the record of the results of
soil examinations from five pear orchards and one prune orchard
during the winter of 1908-09, shows that all of the larvae in the hard
gravelly soils were within 8 inches of the surface, while in the adobe
soil only 79 per cent were found at this depth, the other 21 per cent
being between 8 and 13 inches below the surface.

Tablk XII. — Comparative depth of larvse of the pear thrips in various soils near Walnut
Creek, Contra Costa County, Cal.

Pear and prune orchards.

Anderson, F. A. Bancroft, and Whit-
man (pear), and Jones (prune) orch-
ards. Heavy loam to adobe.

WescottandH. H.
Bancroft (pear)
orchards. Hard,
sandy, gravelly
soil.

Number
of layer.

Depth.

24 samples.

12 samples.

Number
of thrips.

Per cent
above.

Number
of thrips.

Per cent
above.

2

3

4

5

6

7

8 . .

9

10

11

12

13

Total n

Inches.

1- 2

2- 3

3- 4

4- 5

5- 6

6- 7

7- 8

8- 9
9-10

10-11
11-12
12-13

limber of

0

0

0

76

276

152

82

48

32

42

24

4

3
3

9
18
33
IS
6
0
0
0
0
0

3.33
6.66
14.44
36.66
73.33
93.33
100. 00

10.33
47.83
68.70
79.98
86.23
90.57
96.28
99. 55
100. 00

730
123

90
30

Average
of la
square

number
'vpe per
foot

AREA AROUND DIFFERENT TREES IN WHICH THRIPS ARE MOST NUMEROUS.

The area around trees in which thrips are most numerous would
usually be within a radius of 6 to 8 feet of the base in prune orchards
where the trees are from 22 to 24 feet apart. Under prune trees
which are from 18 to 20 feet apart, and where the branches overlap,
the area infested will be more uniform, and more thi'ips will be
present midway between the rows than nearer the base, as such trees,
growing close together, usually do not have so many smaller limbs
in the center of the tree as nearer the end of the branches. Pear
trees are more upright and compact in growth; hence the greater
percentage of the larvse are near the trunk of the tree, and in the

THE PEAR THRIPS IN CALIFORNIA. 49

average Bartlett pear orchard most of the larvae in the ground are
within a radius of 2 to 3 feet of the base of the tree.

TIME SPENT AS LARV^ IN GROUND.

The time spent by larvae in the ground before pupating varies.
The minimum time is about 2 months, with a maximum of about 8
months, while most of the larvse will spend about 5 to 6 months
within the soil before pupating. Of many examinations of soil
samples in Contra Costa and Solano Counties no larvae were found
after November 29; all had i^upated prior to this time.

As soon as the white larva gets ready for transformation it sheds
its skin and develops into what is called the prepupa, which is also
white and resembles somewhat the full-grown larva, although also
having some features of the adult. In this stage the legs resemble
shghtly the legs of the adult and the short wing pads extend to
about the end of the third or fourth abdominal segment. The
antennfe in this stage do not project over the back, as in the case of
the pupa or second stage, but project latero-caudad. The exact
length of time spent in this prepupal stage has not been ascertained,
but from observations made upon other Thysanoptera by the writers
this stage is usually very short and in the pear thrips probably does
not last more than a week or 10 days before the prepupal skin is
shed and the insect passes into the second pupal stage or real pupa,

TIME OP FIRST, MAXIMUM, AND LAST PUPATION.

The earliest pupae are found during the month of May, and these
are very rare. It is possible that these will form late-emerging
adults, but more than hkely they are premature larvae that are
sickly or mfected with some fungous organism which causes them
to develop prematurely. All of these early pupae probably die and
fail to reach the adult form. A few pupae can be found the latter
part of July, and there is a gradual increase in numbers through
August and September. During the month of October, however,
pupation reaches its maximum and may continue through Novem-
ber and into December, by which time it has practically ceased.

Samples taken from orchards in July and August show some
pupae, while sometimes large numbers of samples taken from the
same orchards in September fail to show the presence of any. Table
XIII shows the relative number of early pupae and of larva? found
in the Santa Clara Valley during the summer of 1909. Two samples
of soil were taken from each orchard for each examination.

50

BULLETIN" 173, U. S. DEPARTMENT OF AGEICULTURE.

Table XIII. — Comparative number of pupae and larvse of the pear thrips found in the
soil during July and August, 1909, San Jose, Cal.

Landon and Cottle prane orchards.

Sample

Nos.

Date ex-
amined.

Larvse.

Pupa;.

Number.

Per cent.

Number.

Per cent.

30-33...
34-37. . .

38-41...
42^5...
46-49. . .
50^3...

51-57...
58-61...

1909.

July 15
20
28

Aug. 3
17
17
23
23

556
127
67
44
22
165
65
93

99
100
86
94
100
87
80
82

66

1

11
4

14
6

22
13
18

13

:o

19

The time of pupation varies considerably with different orchards;
for mstance, in orchards where irrigation is practiced in the early fall,
pupation probably starts at an earlier date than in orchards where
this custom is not followed. Furthermore, from a number of exami-
nations made the past two years it seems evident that pupation
begins earlier in those orchards having a heavy sedimentary soil
than in orchards which have a light, gravelly soil. Fall plowing
would necessarily be more effective upon orchards which have a
gravelly soil on account of this habit of late pupation, which would
enable the owners to wait until the fall rains have started before
plowing, and also because a larger number of thrips are near the
surface.

EFFECT OF WEATHER CONDITIONS UPON PUPATION.

It is hardly probable that temperature conditions affect the length
of the pupal stage of the pear thrips very greatly, since the ground
does not freeze in the winter, except in the Eastern States, and the
mean temperature at 6 to 9 inches below the surface for the year
around is probably more even than it is above the ground. An early,
wet fall would probably cause the thrips to pupate earlier than would
be the case in a dry season.

The time spent in the pupal stage varies from one to four months,
while the normal time for most of the pupse is about two months.

ADULTS IN WINTER.

The first adults appear in the ground in late October, the number
mcreasing gradually until December to early January, by which time
practically all pupae have transformed to adults. The time spent in
the ground as adults before emerging and appearing on the trees
varies from a minimum of one month to a possible maximum of five
months, averaging, however, about three months.

THE PEAR THRIPS IN CALIFORNIA. 51

SEASONAL HISTORY.

Adult thrips first appear in early February upon the fruit buds
and continue to emerge until in the early part of April, appearing in
maximum numbers from February 22 to March 10, thus covermg the
entire period of swellmg of buds and blossoming of trees. By the
time the fruit buds have swollen sufficiently to separate slightly the
bud scales at the tip the adults force their way within, feeding upon
the tenderest parts of the buds. Egg laying usually begins when the
first leaf surface or fruit stems are exposed, depending somewhat upon
the variety of fruit attacked. First oviposition usually occurs the
latter part of February and the last toward the middle of April, while
maximum oviposition occurs from about March 10 to April 1. The
majority of eggs are deposited in the fruit stems, young fruit, and leaf
stems, and require from 4 to 16 days to hatch, averaging about 8 days.

By the time Bartlett pear and French prune trees are breaking
into full bloom the adult thrips have done practically all of the injury
they are able to accomplish. Injury by adult thrips is distinctly
associated with the fruit buds before blossoming.

Larvfe first appear in numbers toward the latter part of March and
can be found upon the trees up to the middle of May. They appear
in maximum numbers from April 1 to April 15.

The larvae feed upon the foliage and young fruit, causing on the
latter the well-known thrips scab, and individuals remain on the
trees for two to three weeks in attaining their growth, the entire
brood of larvae requiring 8 to 10 weeks from the first-appearing to the
last-disappearing individuals.

All of the larvae have dropped from the trees by the middle of May
and penetrated the soil to a depth of from 1 to 26 inches, depending
upon the type and condition of same, in most cases the majority
being within 8 to 9 inches of the surface.

Sometimes in July a few larvae transform into the tender pupae,
and by October the pupae are in maximum numbers, the last larvae
pupating in November. The pupal stage lasts from one to four
months, the usual time being about two months.

Early in February adults, which, in some instances, have remained
as such for several months in the ground, appear upon the trees and
wait for the first opening of buds, when they begin the work of
destruction.

NATURAL ENEMIES.

Probably no single order of insects of such great economic impor-
tance has so few effective natural enemies as the Thysanoptera.
This is partly due to the small size of the insects belonging to this
order, their manner of working, their great activity, their unique life
history, and the fact that not more than six or seven species in the
order have ever accomplished any great economic damage. Practi-

52 BULLETIN 173, U. S. DEPARTMENT OF AGRICULTURE.

cally all the attempts to control the tlirips by artilicial means have
been within the United States. Of the. few natural enemies of Thy-
sanoptera that do exist, the most important seems to be TrvpJdeps
insidiosus Say, which feeds upon thrips by impaling them upon its
beak and sucking out the juices. Megilla maculata De G., chrysopid
larv[ie, and syrphid larvse have also been found feeding upon thrips.
Uzel • has found Triphleps niinutus L. preying on thrips and credits
Heeger with the finding of Scymnus ater Kug., Gyropliaena manca Er.,
and some fly larvse feeding in the same manner. Hinds ^ mentions
having found some small scarlet acarid attached to the membranous
area of the body of Anaphothrips striatus Osborn. Uzel ^ and Quaint-
ance ^ have both found eggs of nematode worms within the bodies of
adult thrips. J. C. Crawford* in December, 1911, gives a short account
of Thripoctenus russelli Crawford, a new internal parasite of Thy-
sanoptera and later RusselP publishes a more complete account of the
life history and habits of this parasite. The first recorded host of T.
russelli was Heliothrips fasciatus Pergande, but it has been reared from
Thrips tahaci Lind. and Frankliniella tritici Fitch. Its oviposition
has been observed in Heliotlirips femoralis Renter and H. haemor-
rhoidalis Bouche. Great hopes were entertained by Mr. Russell for
its colonization among related injurious Thysanoptera.

Of plant parasites, Thaxter ^ has taken an Empusa fungus destroy-
ing a species of thrips in the larval, adult, and pupal stages, and
Petit '^ and Hinds ^ have found a fungus which they thought was
causing some of the species of thrips to di6.

No effective natural enemy has been found preying upon the
pear thrips. Moulton ^ mentions some raphidians feeding upon the
younger forms of this species and has also found a species of ant
killing individuals. He mentions ^° a fungus which he regarded as
parasitic during the season of 1905 and 1906, but the last three or
four years have failed to show that any appreciable amount of
benefit has been derived from it. Very little of the fungus has been
observed during the years 1908, 1909, and 1910.

1 Uzel, Heinrich. Monofcraphie der Ordnung Thj'sanoptera. Koniggriitz, 1895, 472 p. 10 pi. See p. 362.

2 Hinds, W. E. Contriljution to a Monograph of the Insects of the Order Thysanoptera Inhabiting
North America. In Proc. U. S. N. Mns., vol. 26, p. 119, 1902.

3 Quaintance, A. L. The Strawberry Thrips and the Onion Thrips. Fla. Agr. Exp. Sta., Bui. 46,
p. 79-114, 12 figs. July, 1898.

4 Crawford, J. C. Two new Hymenoptera. In Proc. Ent. Soc. Wash., v. 13, no. 4, p. 233-234, 1911.

6 Russell, H. M. An Internal Parasite of Thysanoptera [ Thripoctenus russelli]. U. S. Dept. Agr.,
Bur. Ent., Tech. Ser. no. 23, pt. 2, p. 25-52, figs. 11, Apr. 27, 1912.

6 Thaxter, Roland. The Entomophthoreae of the United States. In Mem. Boston Soc. Nat. Hist.,
V. 4, no. 6, p. 134-201, pis. 14-21, Apr., 1888. See p. 151, 172, 174, pi. xvii, figs. 200-219.

' Pettit, RufusH. Some Insects of the Year 1898. Mich. State Agr. Coll. Exp. Sta., Bui. 175, p. 341-373,
20 flgs, July, 1899. See p. 343-345, figs. 1, 2.

s Loc. cit.

9 Moulton, Dudley. The Pear Thrips {EiUhripn pijri Daniel). V. S. Dept. Agr., Bur. Ent., Bui. 68,
pt. 1, rev., p. 14, Sept. 20, 1909.

"> Op. cit., p. 15.

o

82U-><-^

BULLETIN OF THE

u

No. 184

Contribution from the Bureau of Entomology, L. O. Howard, Chief
Aprils, 1915.

(PROFESSIONAL PAPER.)

THE HUISACHE GIRDLER/

By M. M. High,
Entomological Assistant, Truck Crop and Stored Product Insect Investigations.

INTRODUCTORY.

The huisache tree is one of a variety of trees and shrubs horti-
culturally called " wattles " and is probably a native of Texas,
although it occurs in Asia, Australia, and to a certain extent in
Africa. The flowers furnish the perfume laiown as frangipanni
and the plant is cultivated in southern Europe for the manufacture
of perfume. The pods are valuable in tanning and dyeing and
the plant is used as an ornamental for the formation of hedges and
for shade throughout the Tropics. The bright yellow flowers which
are produced in abundance and are large in comparison with those
of other acacias render it one of the most beautiful of flowering
shrubs of this type. The tree reaches a maximum height of about
35 feet, with a trunk diameter of about 1 foot when properly trained.
The trunk is short, the branches somewhat drooping and wide-
spreading, forming a beautiful roundheaded tree with light-green
feathery foliage.

The huisache tree {Acacia farnesiana) of the Southwest has a
number of insect enemies, but none is so injurious as a girdler
which often damages young trees in such a way as to eradicate them
for a time, completely severing them a few inches above ground.

During the summer of 1910, while the writer was engaged, under
the direction of Dr. F. H. Chittenden, in the investigation of in-
sects that attack the pecan, this insect, which may be called the
huisache girdler, first came under observation. It seemed advisable
to keep the species under surveillance in its attacks on the huisache,
since it was not known but that pecan trees in the vicinity might
become a center of attack at any time, for the reason that two
near relatives, Oncideres cingulata Say and Oncideres texana Horn,

1 Oncideres putator Thorn., a beetle of the family Cerambycidse.
Note. — This bulletin contains a technical description of an insect infesting the huisache
tree of the Southwest. The form of injui-y is discussed and methods of control are given.
75718°— 15

2 BULLETIN 184, U, S. DEPARTMENT OF AGEICULTUEE.

were laiown to injure the pecan. In any case, the huisache was of
sufficient vahie to warrant a thorough investigation of the girdler,
as it holds front rank as a shade tree in the newly developed
country in the lower Rio Grande Valley. When the girdlers were
first found and observed at work they were exceedingly abun-
dant, and there was no difficulty in collecting a large number in
a very short time. A shipment was immediately made to Wash-
ington, where Dr. Chittenden identified the insect as Oncideres
futatoi^ and later Mr. E. A. Schwarz confirmed this determination.
Since the girdler was first observed, its work has become more con-
spicuous each successive season. In 1913, over the infested area as a
whole, the beetles appeared in lesser numbers, but in places they
were more abundant and the damage was greater than at any time
during the four years previous. This would indicate that climatic
conditions were not altogether responsible for the decrease, as some
of the infested areas were near and in close proximity to one another.
It is believed that natural enemies were responsible in part, if not
wholly, for the lack of uniformity in distribution in 1913.

The beetles (PI. I) possess powerful mandibles and saw with ease
branches If inches in diameter, completely severing them from the
main body of the tree. The eggs, as with other twig girdlers, are
deposited in the severed portion of the branch, and never below
where it is girdled. The writer has observed as many as 63 girdled
branches from one tree, some of which measured 40 millimeters in
diameter, the average ranging from 22 to 35 millimeters. (See PI.
II. ) No other girdler has been observed to prune branches of this di-
ameter, and all near relatives with which we are acquainted prune
or girdle much smaller branches. Oncideres putator, unlike some
girdlers, does not work so much in pairs, but is often found in colo-
nies as well. The girdling is usually begun a few inches from the
base of the branch selected for oviposition or just above where it
joins the body of the tree or larger branch, though cases have been
observed where the attack was directed to the middle of the branch.
At times after the sawing has been begun by one female beetle others
will begin depositing eggs before the girdling is very far advanced,
apparently with little fear that the branch will not be completely
girdled in due time. Young trees are often girdled only a few inches
above ground, but where large trees are adjacent the beetles seem
to prefer attacking the branches instead. (Pis. Ill, IV.)

In view of the fact that in the lower Rio Grande Valley and other
parts of the Southwest where much development in farm lands is in
progress, and where the huisache is oftentimes the only shade tree
found upon a farmer's premises, it is thought advisable to present
here for publication the life history, food plants, and habits of this
girdler, with suggestions for control.

THE HUISACHE GIEDLER. 3

DESCRIPTION.

The beetle belongs to the family Cerambycidse, subfamily Lamiinse,
tribe Onciderini. One of the chief characteristics of the tribe is
that the front coxal cavities are angulated on the outer side and
closed behind; the antennae of the male are much longer than the
body, and those of the female are as long as the body.

THE BEETLE.

With this species the antennae of both sexes are longer than the
body, and there is little difference in the antennal length in each sex.
The beetles (PI. I) are brownish gray in color, and measure in length
from 18 to 24 millimeters, the average length being 22 to 23 milli-
meters. The mesothorax is wider than in some other species of this
genus and measures on an average from 7 to 9 millimeters. In a
short time after emerging from the pupal case the beetles lose more
or less of their brownish-gray appearance, as the hairs covering their
blackish elytra or wing covers are rubbed off, causing them to ap-
pear darker in color. This species, like its near relatives, has about
one-third of its wing covers more grayish than the remaining two-
thirds. The posterior margin of this densely clothed grayish band
extends slightly behind the meson. The head and thorax are clothed
with brownish hairs a little more densely than the wing-covers when
the beetle first emerges, but it gradually loses this brownish tinge
for a darker one. Ordinarily there seems to be little difference in
size between the males and females. While the writer has found
specimens of each sex at times smaller than those of the other, it is
evident that the size depends upon the nourishment afforded the
larva during its growth, as this in all probability has a bearing on
the size of the adult beetle.

After making a large number of measurements it was found that
about 60 per cent of the females were from 1 to 1-| millimeters longer
than the males, so we may say that the body of the female is slightly
larger than that of the male, although this will not be noticed by the
collector without the use of a lens. On the other hand, the collector
may differentiate the sexes by observing the distal joint or segment
of the antennae; in the males this segment is about twice as long as
that of the female. The length of this segment in the males runs
from 4 to (U millimeters, while in the females the average will be
from 2 to 3 millimeters. This method of distinguishing the sexes
does not require the use of a lens, but one should be careful to see
that the distal joint has not been broken off, in the male particu-
larly, for then the specimen will not be very different to the unaided
eye from the female. The antennae of both sexes are quite easily
broken, and during the latter part of the mating season it is difficult
to find a perfect specimen.

4 BULLETIN 184, U. S. DEPARTMENT OF AGRICULTURE.

THE EGG.

The egg is of a cream-white color when first deposited and from
2.5 to 3 millimeters long, with a diameter about one-third the length.
It is elliptical ovate in shape, with one end slightly more pointed
than the other. Just before hatching the color changes to yellowish
white, when, with the aid of a lens, the embryonic larva is visible.

THE LARVA.

The newly hatched larva, after consuming enough of the eggshell
to liberate itself therefrom, measures about 2.8 millimeters in length
and is of a pale white color, with the exception of the head, which is
light brown, with the mandibles darker.

THE PUPA.

The pupa is white and ranges from 18 to 22 millimeters in length.
Later the color changes to light brown, and just before transforma-
tion takes place to chocolate brown. When observing the pupa with
a lens the dark-colored spines on each segment are very pronounced,
particularly on the dorsum.

DISTRIBUTION AND HISTORY.

Oncideres putator has been recorded from the States of Arizona,
New Mexico, and Texas, and from Mexico. The species is probably
more injurious in Mexico than in this country, as it appears very
susceptible to cold, and since breeding takes place during the fall
and winter months it apparently could never become a serious pest
in localities were the temperature drops much below freezing.

The following note was published in 1912 ^ at the meeting of the
American Entomological Society, October 24, 1912 :

Dr. Skinner exhibited specimens of Oncideres putator and said that the species
was probably rare in collections. If there is a single brood, this might be ac-
counted for by their late appearance. The specimens were taken by Rehn and
Hebard in Sycamore Canyon, Baboquivari Mountains, Pima County, Ariz.,
October 6, 9, 1910 ; Palo Alto ranch, Altar Valley, Pima County, Ariz., October
6, 10, 1910; Tucson, Ariz., October 3, 4, 1910; and Snyders Hill, Pima County,
Ariz., October 11, 1910.

Exact localities have also been recorded by Bates : " Orizaba and
Jalapa, Mexico; Belize, Honduras; San Juan, Guatemala; Bugaba,
Panama. Mr. Schwarz records the species from Arizona, New Mexico,
and western Texas, and the Avriter has taken it in southern Texas and
at Matamoras, Mexico. The species is native to Central America and
has come into the United States from Mexico. There are very few
data to be found on Oncideres fidator^ while a considerable amount

1 Ent. News, v. 23, no. 10, p. 484, Dec, 1912.

- Bates, H. W. Longicornla. In Biol. Cent. Amer. Insecta, Coleoptera, v. 5, p. 125,
Aug., 1880, and Supplement, p. 367, July, 1885.

Bui. 1 84, U. S. Dept. of Agriculture.

Plate

The Huisache Girdler (Oncideres putator). (Original.)

Bui. 184, U. S. Dept. of Agriculture.

Plate II.

-iTzr^-n

Work of the Huisache Girdler.

Portions of Huisache brandies showing method of cutting off by the girdier (Oncideres putator) at
top; also showing places where skin has been ruptured. Small holes made by secondary
borers. Reduced. (Original.)

Bui. 184, U. S. Dept. of Agriculture.

Plate III

Fig. 1.— Work of the Huisache Girdler Early in the Season. Twenty Beetles
Counted on this Tree. (Original.)

Fig. 2.— Trees Which Have not Been Seriously Injured by the Girdler. but no
Dead Branches Allowed to Remain on or near Trees. (Original.)

WORK OF THE HUISACHE GIRDLER.

Bui. 184, U. S. Dept. of Agriculture.

Plate IV.

Fig. 1.— Row of Huisache Trees only Slightly Damaged by the Huisache Girdler.

(Original.)

Fig. 2.— Street Scene in Which Huisache Trees Have Been Damaged by the
Huisache Girdler. (Original.)

WORK OF THE HUISACHE GIRDLER.

THE HUISACHE GIRDLER. 5

of information has been placed on record of Oncideres cingulata
Say. It appears that some of the early writers on the Onciderini
mentioned only the genus Oncideres in writing of the depredations
of the insects concerned.

The first information received by the Bureau of Entomology in
regard to the injurious appearance of Oncideres putator in this coun-
try was in 1899 at Calabasas, Ariz. The report came from Mr.
Morgan R. "Wise, who sent specimens of mesquite {Prosopis juli-
-fiora) which had been girdled by the beetle, together with the state-
ment that this tree was much injured by the girdler. The previous
year the beetles had accomplished much damage, so that this year
the girdled dead twigs snapped off. It was the opinion of the cor-
respondent that, if this condition was continued, ultimately the
mesquite tree would be exterminated by being so badly crippled as to
preclude the possibility of its bearing fruit. Mr. Schwarz says that
the beetles damage mesquite in western Texas and New Mexico, as
well as in Arizona.

The genus Oncideres has been discussed by a number of authors,
but the writer has been unable to find, in literature on this group,
any memoranda on the biology of the species in question. Dr. W.
MuUer* discusses the habits of Oncideres in South America, but
mentions no specific characteristics, nor does he mention the occur-
rence of Oncideres pufator. He states, however, that the species
which occur in Brazil frequently sever branches of a diameter of 2
inches or more.

Leng and Hamilton^ state that Oncideres putator is probably
synonymous with 0. cingulata Say.

The species was originally described by Thomas,'' but no biological
notes are included in the description.

FOOD PLANTS.

So far as the writer has been able to observe, the species has in
southern Texas five food plants, but the huisache appears to be pre-
ferred and the other trees have never been found to be injured in any
way comparable with the huisache. The following is a list of the
plants or trees on which the species has been foimd feeding, as well
as depositing:

Huisache {Acacia famesiana), mesquite (Prosopis glandulosa)^
huajilla {Acacia herlandier'i) ^ ratama {Parhinsonia aculeata)^ and
Mimosa lindheimeri. The host plants are here given in the order
of preference by the insect, and no great amount of injury has been

^ Miiller, W. (Jber die gewohnheiten einiger Oncideres-Arten. In Kosmos, Zeitschrift
fiir die gesamte Entwicklugslehre, v. 3 9, p. 36-38, 1886. Stuttgart. '

- Leng, C. W., and Hamilton, Jolin. The Lamiinre of North America. In Trans. Amer.
Ent. Soc, V. 2.3, p. 101-178, March, 1890. Oncideres, p. 140-141.

^ Thomson, .Tamos. Physis, v. 2. no. .T. Pari.'?, Aug., 1868. Revision des groupes des
Oncid^rites, p. 41-92. Oncideres pufator, p. 81.

6 BULLETIN 184, U. S. DEPARTMENT OF AGEICULTUEE.

observed to the last three when there was sufficient huisache in close
proximity to the emerging beetles. In fact, the greatest amount of
damage to "huajilla" and "ratama" was noticed when collections
of huisache branches containing larvce were left near ratama and
huajilla trees.

LIFE HISTORY.

The beetles begin to appear early in September and continue to
emerge from their j)upal cavities until the latter part of November,
though most of the brood issues during the month of October. In
the laboratory most of the material encaged developed adult beetles by
October 12. The adults remain for several days in their pupal cells
after they have emerged from the pupal cases before attempting to cut
their way out of the pupal cavities through the bark of the branch.
Just as soon as they have partaken of a little food, which consists
of bark from the branch, and the wing covers are sufficiently hard-
ened, copulation begins. Of specimens observed in the laboratory
none began copulating or showed activity before two days after
their emergence in the adult stage. This species of Oncideres, un-
like its near relatives, Oncideres cingulata and 0. texana, does not
so frequently work in pairs. The M^riter has found the beetles work-
ing in pairs, but during midseason they occur to a greater or less
extent in colonies. The writer has observed as many as 24 on one
small tree, and two-thirds of them at times would be females. The
males go from one female to another, and do not seem to possess the
monogamous instinct.

Wliile making observations on the species during October, 1910,
it was decided to see how long a period was required for one unas-
sisted female to prepare the egg cavity and deposit an ^gg. The first
one tried deposited in 1 minute and 35 seconds, another in 4 minutes
and 50 seconds, and the next in 4 minutes and 40 seconds. Observa-
tions made later show that from 1 to 5 minutes is ordinarily required
for the female beetle to deposit. This, however, does not include pre-
paring the cavity to receive the ^gg^ for it generally requires about 10
minutes to prepare the cavity. The beetle begins this cavity by insert-
ing both mandibles as deeply as possible into the bark of the branch
that is to be girdled. After forcing the mandibles deep into the
bark the beetle draws them together as nearly as she can. Then one
is removed and the other worked deeply into the puncture. It is
then removed and the other mandible is inserted in the same manner.
Later both mandibles are inserted and a tiny chip removed. Then
the work begins again with one mandible at a time, until the
cavity is prepared to receive the egg. The beetle then reverses its
position and forces the ovipositor into the cavity as deeply as pos-
sible. Shortly the egg can be seen leaving the body of the beetle.
After the egg is inserted the beetle frees herself by withdrawing the

THE HUISACHE GIRDLEK. 7

ovipositor, one side at ca time, and then she searches for another suit-
able location. The eggs are ordinarily placed between the layers
of bark, and it may here be stated that this species does not deposit
particularly about buds or at the base of smaller branches, but may
lay her eggs anywhere along the branch girdled. It also might be
added that, unlike some, this species of Oncideres does not make
transverse incisions in the bark, presumably to prevent the growth
of the branch from crushing the egg.

There is, in addition, a difference from Oncideres dngulata and
O. texana in the way this species leaves the egg after deposition, in
that only a very slight gluey excretion is made in sealing the
opening to the egg cavity, and at times there is none at all. This
waxy secretion is very conspicuous with the work of the two smaller
species.

The larva feeds along gradually, leaving in its burrow behind
excrement and castings well packed, which may prevent attack of an
enemy from the rear. It has been observed that when a branch not
completely severed remained in the top of the tree the yoimg larvse
would often perish, presumably for lack of moisture. On the other
hand, the writer has noticed branches that remained several feet above
ground all season and which developed beetles during October. It
thus appears that it will depend upon the amount of rainfall and cli-
matic conditions generally as to whether the mortality of the larvae is
high in the suspended branches — well up in the tops of the trees. If
there should be a moderate rainfall during the winter and spring
months, it is thought that the mortality in these suspended branches
would be very low", but on the other hand if it should be dry, the mor-
tality would be high. While the larva will stand a very dry atmosphere
for several months, its growth will not be as rapid as where there is
sufficient moisture to permit constant feeding. Larvse that have been
checked in growth from lack of moisture develop very rapidly when
placed in more humid surroundings and appear to obtain their growth
just as soon as when left under normal conditions. They could not
well do otherwise and thrive in the climate where they have been
found most numerous. There is a limit, how^ever, to the amount of
moisture the larvae can stand, for in one instance in the laboratory
the mortality was about 70 per cent, and it could be attributed to no
other cause than an excess of water. The duration of the larval
period is approximately 42 weeks under ordinary conditions, though
under the most favorable conditions they may develop in 39 or 40
weeks. Before transforming to pupa the larva prepares a pupal
cavity or cell by drawing about it all castings and thus surrounding
itself with more or less of a wall that would be difficult for any insect
enemy to penetrate. The larva then cuts a hole into the bark and
transforms to the pupa. During the growth of the larvae in the brancli

8 BULLETIN 184, V. S, DEPARTMENT OF AGRICULTURE.

they produce a grinding noise that can be heard several feet away,
and when the branch is disturbed this noise is more pronounced.
The pupae in turn make a somewhat similar noise when disturbed,
and for this reason one must raise the bark covering in order to
know just when transformation takes place.

Before the pupal stage of this species could be had the writer was
transferred to Indiana, and the material was taken there in order
to obtain the pupae. The branches were examined frequently during
the months of June and July, but no pupae were observed until
August, and the first adult beetle emerged September 15, The dura-
tion of the pupal stage is approximately four weeks, with an average
mean temperature of 72.5° F.

There is only one generation of this beetle each year, approximately
12 months being required for the life cycle from egg to adult.

LONGEVITY.

The beetles that emerged in the laboratory were kept in confine-
ment without fresh food and lived from 4 to 12 days, while those
that were captured, confined in the insectary, and furnished proper
food lived from 10 to 21 days, the males dying from 1 to 5 days in
advance of the females.

NATURAL ENEMIES.

There are several species of parasites that attack the eggs and
larvae of Oncideres putator^ one species in particular attacking both
Qgg and larva. The following were reared February 3, 1915, at
Brownsville, Tex.: Chryseida inopinota Br., Eurytoma sp. (Chttn.
No. 1921), Caenophanes sp. (Chttn. No. 1922), a pteromalid (Chttn.
No. 1923), and Meteonis sp. (Chttn. No. 1924). It is thought that
the larvae have one or more predaceous enemies, but none has been
observed to this writing. It is believed that the southern downy
woodpecker {Dryohates puhescens) and probably also the Texas
woodpecker {Dryohates scalaris hairdi) attack the larvae. While
neither of these birds has been found with larvae, they have been
observed at work on branches that contained numerous larvae of this
insect and have left empty chambers behind.

Table I shows something of the mortality early in the season.

Table I. — Mortality of the huisache girdler, based on examinations made Janu-
ary 8, 1913.

Number of branch.

Diameter
of branch
(milli-
meters).

Number of

eggs.

Number of
live larvae.

Number of
dead
larva?.

I

26
30
35
28
32
37

n

0
19
0
0

7

0
58
153
197
173
52

0

II

3

Ill

2

IV

14

V

17

VI

0

THE HUISACHE GIRDLER.

9

On January 13, 1913, four prunings of huisache were stripped of
bark, and the following table made :

Table II. — Infestation of the huisache girdler by parasites, based on examinations

made January 13, 1913.

Number of branch.

Diameter

of branch

(miUi-

meters).

Number of
eggs.

Number of
living
larvae.

Number of
larvae par-
asitized.

I

36
30
25
38

0
0
0
59

363
104
79
135

11

11

5

Ill

6

IV

0

These tables give the degree of infestation to a single branch and
the mortality of the larvae at a very early date. The parasites of the
larvae are more numerous a little later in the season, although the
egg parasite appears even as early as December 1. This parasite is
more effective against the larvae before they approach a size more
than two-fifths of an inch in length; although it attacks the larvae
throughout the season it does not appear in as large number then
as it does early in the season.

METHOD OF CONTROL.

Since this insect spends at least 10 months in the severed branch
during the egg, larval, and pupal stages, its control is only a matter
of collecting the pruned branches and destroying them by burning.
This would not be a laborious task, as the girdled branches are so
large that it is not difficult to locate them, and as the species does not
appear to migrate very rapidly to new territory, this method would
nearly eradicate the species in isolated localities, at least, in one or
two seasons' time, taking it for granted that a few branches might go
unnoticed. (See PI. Ill, fig. 2.) The work of burning the branches
could best be done from the first week of January to the first of Au-
gust, as the writer has not observed the laying of any eggs as late as
January 1. As the huisache wood burns readily, it should be com-
paratively easy to collect and destroy pruned branches from a large
number of trees in a comparatively short time. In addition to this
measure, the beetles might be collected by hand wiiere one has only a
small number of trees to guard against this girdler, and in this way
the trees could be protected before any damage had been done.

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1916

ADDITIONAL COPIES

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^ ,_it;oTa.

BULLETIN OF THE

No. 186

Contribution from the Bureau of Entomology, L. O. Howard, Chief, and the
Bureau of Plant Industry, Wm. A. Taylor, Chief.
February 27, 1915.

A METHOD OF FUMIGATING SEED.^

By E. R. Sasscer, Chief Inspector, Federal HorticuUural Board, and Lon A. Hawkins,
Plant Physiologist, Plant Physiological and Fermentation Investigations.

INTRODUCTION.

A perfectly reliable method of destroying insects present in seeds
imported into this country, without injury to the seed, is much
needed. The exclusion of insects by a careful selection of apparently
uninfested seeds at the port of export is impracticable, because many
injurious insects pass their larval and pupal stages and a portion of the
adult stage inclosed within the seed and on this account might easih^
escape notice when the seeds were inspected. Furthermore, seeds are
frequently received from localities where injurious insects are not well
recognized, and, also, insects wdiich are only slightly injurious in their
native habitats occasionally become destructive pests when estab-
lished in this country.

The ordinary methods of destroying insects in stored seeds, such
as subjecting them to heat (with or without moisture), carbon
bisulphid, and hydrocj^anic acid in the presence of air, have been
tried and found unsatisfactory for this purpose.

It occurred to the waiters to create a partial vacuum in the con-
tainer in wliich the seeds had been placed and fill the chamber with
some gaseous insecticide, such as carbon bisulphid or hydrocyanic
acid, in the belief that a much larger amount of gas might thus be
forced into the crevices of the seeds and into the insect galleries than
would be possible if the entrance of the gas were dependent upon
diffusion under normal atmospheric pressure. This method was suc-
cessfully used with a number of different kinds of seeds and insects,
and a convenient chamber, described later, was devised for fumigation
under reduced pressure.

iThis work was carried on in cooperation betrween the Federal Horticultural Board and the Office of
Plant Physiological and Fermentation Investigations, Bureau of I'lant Industry, U. S. Department of
Agriculture.

75871°— Bull. 18(5—15

BULLETIN 186, V. S. DEPARTMEXT OP AGRICULTURE.

FUMIGATION CHAMBER.

The fumig-ation chamber (fig. 1 and fig. 2, h) is of iron tubing, 36
inches long by 12 inches in diameter. One end of this cylinder is per-
manejitly closed with a heavy iron cap (fig. 1, a). The other end is
fitted with a flange and can be closed with a brass plate (fig. I, h),
which is held ii^ place by clamps. One face of the plate is ground to
fit the flange, wliich is also ground. A wide rubber gasket is phiced
b(>tween the two faces when the plate is clamped in position. The
chamber is designed to lie with its longest axis in a horizontal position.
On the side of the chamber intended to lie uppermost three openings
are made, one being in the center and one at each end. The openhxg

CZ

w

■^wwwwwwwwwww

jjssssssss^

/

.^^^^^■v^^^^^^^'vv^^^^v^^'^^^^^^'^^^■^'.^^^^^^^^«^v.^^^^^^^^^^^.^^^^^^^

ML

Fig. I. — Diagram of fumigation chamber: a, Iron cap; b, brass plate clamped on end of chamber; c, gas
cock for attachmg suction hose; d, vacuum gauge; e, dropping funnel, by means of which the sulphuric
acid is introduced into the chamber: /, beaker to contain cyanid.

near the capped end is fitted with a gas cock (fig. 1, c), so that the
suction hose of a vacuum pump can be readily attached. A vacuum
gauge, registering the decrease in })rcssure in units equivalent to inches
of mercury, is placed in the center opening (fig. 1, d), wliile a tubula-
ture is placed in the opening near the flange. The tubulature is
closed with a perforated rubber stop})er bearing a dropping funnel
(fig. 1, e) so arranged that the bulb and stopcock are outside the
chamber, while the tube extends down inside the chamber nearly to
the bottom. The rubber stopper and dropping funnel can be readily
removed when seeds or other material to be fumigated are placed in the
chamber. An air pump, driven by a motor and capable of reducing
th? air pressure to the ecjuivaleiit of about 0.05 of a millimeter of mer-
cury, is used to secure an almost complete vacuum (fig. 2, a).

A METHOD OF FUMIGATING SEED. 3

When this apparatus is used for fumigation, the seeds, contained
in cither a cloth bag or an open vessel, are placed in the chamber, and
the requisite amount of socUum or potassium cyanid in a small
beaker is so arranged that the neck of the dropping funnel extends
down into the beaker (fig. 1 , /) . The cover is then clamped on and
the chamber exhausted. In extracting the air from the chamber, the
suction is continued until the gauge registers 30 inches or more —
that is, the air in the chamber is exhausted until the pressure is the
equivalent of some fraction of an inch of mercury. The suction
is then cut off by means of the gas cock, and the required quantity
of diluted acid, which has been previously placed in the bulb of the

Fig. 2. — Air pump (a) and fumigation uhamber (6) used in the experiments described in this bulletin.

dropping funnel, is allowed to flow slowly upon the cyanid in the
beaker witliin the chamber. The hydrocyanic acid is thus prepared
in the chamber and no trace can get out. After the seeds are exposed
to the gas for the required time, the stopcock of the dropping fun-
nel is opened to let the air into the chamber. As the discharge
pipe of the air pump extends outside the building, the mixture
of hydrocyanic acid and air can not escape into the room. As
soon as convenient, the stopper and funnel are removed and, by
means of the air pump, air is sucked through the chamber, thus
washing the hydrocyanic acid out of the chamber before the cover
is taken ofl' and the seeds removed. In the experiments described

4 BULLETIN 186^ U. S. DEPARTMENT OF AGRICULTURE.

here the seeds were examined carefully at several different times
to see whether aU insects were killed. The \T.ability of the seeds
was then tested.

Part of the germination tests recorded in tliis ]>a]>er were made l)y
Mr. W. R. Lucas, of the Office of Foreign Seed and Plant Intro-
duction, ])ut in most cases tests with treated and untreated seeds
were carried out by Mr. W. L. Goss, of the Seed Ija])()ratory of the
Bureau of Plant Industry.

In these experiments the duration of the exposure and the con-
centration of hydrocyanic acid were varied in order to determine
the minimum exposure and concentration of hydrocyanic acid which
would insure the death of all the infesting insects. It was also con-
sidered of interest to determine whether the seeds would be unin-
jured if exposed longer and with a liigher concentration of the hydro-
cyanic acid than that necessary to kill the insects. The duration of
the exposure and the amounts of sodium or potassium cyanid are
given in the description of the experiments. The 1-1-2 formula
was used for potassiimi cyanid and the l-H-2 formula for sodium
cyanid.

The iron fumigation chamber already described was used in most
of the experiments. In some of the preUminary work, however,
desiccators or beU jars were used instead. The essentials of the
method were the same in either case, and no description of these
pieces of apparatus seems necessary.

EXPERIMENTS.

The summarized results of these experiments are here given in
tabular form for com])arison (Table I) .

Tablk I. — Summary of experiments in fumigating against insects.

Material.

Infested with —

Kind of cyanid

and amount

used.

Time

of
expo-
sure.

Result .

• ierminationtest.

-Vvocado:
26 seeds.

29 seeds.

One adult avocado
weevil ( Heilipus
lauri).

Sodium cyanid,
J gra., in des-
iccator.

.... do

Hrs.
1

i
h

6
12

Insect dead

22 out of 26 seeds gerrai-
nated.

20 out of 29 seeds germi-
nated; 21 out of 25
germinated in con-
trol test.

Seed cut up to deter-
mine mortality of in-
sects and not" plant-
ed.

No germination.
Do.

.5 seeds. .
20 seeds.

Larvae of avocado wee-
vil (inclosed in a cot-
ton - plugged vial)
and broad - nosed
grain weevil (Caul-
opmlus latinasus).

do

do

All stages dead

do

Do...

do

do

6 seeds. .

Larvae of Conotrache-
lus sp. and broad-
nosed grain weevil,
all stages.

do

Sodium cyanid,
4gms.

do

1
-

do

All seeds germinated.
Do.

10 seeds.

No insects alive
out of 50 exam-
ined of all stages.

A METHOD OF FUMIGATING SEED. 5

Table I.— Summary of experiments in fumigating against insects — Continued.

Material.

Avocado:
7 seeds.

6 seeds. .
10 seeds.

Do.

S o r g h um
seed.

Do.

Do.
Do.

Do.

Bulbs .

Cottonseed.

Cleditsia si-
nensis in
seed pods.

Do

Phase olus
vulgaris.

Pineapples .

T u s s 0 1
mot
(Heme
campa
costig
500 ^,,
masses

k

h

ro-

leu-

'')■
egg

gma

250 egg
masses.-

Infested with-

Larvae of Conotraehe-
lus sp. and broad-
nosed grain weevil,
all stages.

4 with all stages of

broad-nosed grain

weevil; 2 uninfested.

Scolvtid

Kind of cyanid

and amount

used.

Sodium cyanid
2 gms.

..do.

.do.

.do.

Bruchus sp.

Bnichus sp. and rice
weevil (Calandra
oryza).

do

Rice weevil and ca-
delle ( Tenebroides
mauritanicus).

-do.

Rice weevil.

Bulb mite (RMzogly-
phus hyacinthi).

Adultsof the red grain
beetle (Cathartus ge-
mellatus).

Bruchus sp. (adults)..

do

Bnichus sp .

Pseudococcus sp.

Sodium cyanid

4 &ms.
Sodium cyanid

2 gms.

Sodium cyanid
4 gms.

do

Sodium cyanid
|gm., in des-
iccator.

.do.

Potassium cy-
anid, 2 gms.

Sodium cyanid,
J gm., in des-
iccator.

Sodium cyanid,
IJ gms.

Sodium cyanid,
2 gms.

Sodium cyanid
4 gms.

Sodium cyanid,
i gm., in des-
iccator.

.do.

Sodium cyanid,
2 gms.

Sodium cyanid,
4 gms.

J Out of several hun-
dred specimens
1 live adult was
' foiuid.
h I All stages dead

Insects alive.

All stages dead....

do

do

.do.

.•Vll mites dead . ,
.\11 insects dead.

All insects dead,
both in and out
of seed pods.

.Vll in.seets dead..

.do.

Somelarvse
hatched several
days after expo-
sure.

No hatching

Germination test.

Not i)lanted.

3 seeds planted and all
germinated.

Not planted.

Do.

75.5 per cent germina-
tion; seed badly in-
fested.

71 per cent germina-
tion; seed badly
eaten.

83 per cent germina-
tion.

Of four grades fumi-
gated, the percentage
of germination was
as follows: 7S.5; 86.5;
88; 83.

Germination of fumi-
gated seed superior
to that of untreated
seed.

Seed thoroughly in-
fested with insects
previous to fumigat-
ing and only 15 per
cent germinated.

Bulbs thoroughly in-
fested and unfit for
planting.

Not planted.

Percentage of germina-
tion approximately
the same with both
fumigated and un-
treated seed.
Do.

Germination of fumi-
gated seed superior
to that of untreated
seed.

Not planted.

The results given in Table I indicate that the fumigation of seeds
by the introduction of hydrocyanic acid into an air-tight chamber,
from which the air has been practically exhausted, is effective,
provided the exposure is not less than haK an hour. An exposure
of one-fourth hour is effective with the apparatus employed in these
experiments if four or more grams of cyanid are used.

6 BULLETIN 186, U. S. DEPARTMENT OF AGKICULTUKE.

SUMMARY.

Fumigation by the method described in this bulletin was found to
kill insects without injury to the seed and with a considerably shorter
exjjosure than is necessary in the usual method of seed fumigation.
Further experiments will be conducted with special reference to the
use of carbon bisulphid, which is not consi(h>red in this paper.

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rNSEOT8.

UNITED STATES DEPARTMENT OF AGRICULTURE
BULLETIN No. 189

Contribntion from the Bureau of Entomology
L. O. HOWARD, Chief

Washington, D. C.

April 12, 1915

STUDIES OF THE CODLING MOTH IN

THE CENTRAL APPALACHIAN

REGION

By

F. E. BROOKS and E. B. BLAKESLEE, Entomological Assistants
Deciduous Fruit Insect Investigations

CONTENTS

Introduction

Localities in Which Investigations Were

Made

Nature and Extent of the Investiga

tions

Esplanatioh of the Use of Terms . .
Investigations at Charlottesville, Va.
Investigations at Greenwood, Va. .
Investigations at Hagerstown, Md. .
Investigations at Winchester, Va. .
Investigations at Fishersville, Va. .
Investigations at French Creek, W. Va.
Investigations at Picliens, W. Va. .
ResumS of Rearing Experiments in

Maryland, Virginia, and West Virginia

Page
1

Page

Number of First-Brood Larvn Trans-
forming First Season ...... 42

Effect of Differences in Altitude and
Latitude Upon the Development of the
Codling Moth 42

Relative Numbers of Larve Ascending
and Descending the Trees ....

Seasonal Effect of Weather Conditions
on the Different Stages of the Codling
Moth

Cannibalism Among Codling - Moth
Larvte

Natural Enemies 46

Summary 48

44

45

45

WASHINGTON

GOVERNMENT PRINTING OFnCE

1915

BULLETIN OF THE

I

No. 189

Gjntribution from the Bureau of ELntomology.L. O. Howard, Chief
April 12, 1 91 5.

STUDIES OF THE CODLING MOTH IN THE CENTRAL
APPALACHLVN REGION.

By F. E. Brooks and E. B. Blakeslee,
Entomological Assistants, Deciduous Fruit Insect Investigations, Bureau of Entomology.

CONTENTS.

Page.

Introduction 1

Localities in which investigations were made . 2

Nature and extent of the investigations 2

Explanation of the use of terms 3

Investigations at Charlottes ville, Va 4

Investigations at Greenwood, Va 11

Investigations at Hagerstown, Md 13

Investigations at Winchester, Va 21

Investigations at Fishers ville, Va 28

Investigations at French Creek, W. Va 32

Investigations at Pickens, W. Va 37

E&umd of rearing experiments in Maryland,

Virginia, and West Virginia 40

Niunber of first-brood larvae transforming

first season 42

Effect of difierences in altitude and latitude

upon the development of the codling moth. 42
Relative numbers of larvae ascending and

descending the trees 44

Seasonal effect of weather conditions on the

different stages of the codling moth 45

Cannibalism among codling-moth larvae 45

Natural enemies 46

Summary 48

INTRODUCTION.

In many localities throughout the central Appalachian region the
recent rapid development of the apple-growing industry has made
the control of the codhng moth (Oarpocaj^sa pomoneUa L.) a subject
of special and increasing interest. The hilly or mountainous nature
of the land has led to the location of orchards at elevations ranging
from a few hundred feet to more than 4,000 feet above the level of
the sea. The great diversity of temperature that occurs between the
lower and the more elevated orchards has a marked eJOfect on the
time of transformation of the different stages of the codhng moth,
and consequently has direct bearing on the relative number and the
destructiveness of second-brood larvae.

In the spring of 1911 the Bureau of Entomology began a study of
the codhng moth in the region just mentioned, as a part of its inves-

77013°— Bull. 189—15 1

2 BULLETIN 189^ U. S. DEPARTMENT OF AGEICULTURE.

tigations of this insect throughout the United States, giving particular
attention to time of appearance of the different broods at various
altitudes and latitudes. The work was conducted by or under the
immediate direction of the authors of this paper and was continued
for tliree consecutive years at several points located in Virginia, West
Virginia, and Maryland.

The writers are greatly indebted to the large number of fruit growers
in the various localities where the investigations were carried on for
the free use of orchards in which to obtain banding records, for build-
ings to shelter rearing jars, and for other courtesies. During the
progress of the work many essential suggestions were made by
Prof. A. L, Quaintance, in charge of Deciduous Fruit Insect Investi-
gations, under whose direction the studies were made.

LOCALITIES IN WHICH INVESTIGATIONS WERE MADE.

The studies described herein were conducted at Charlottesville,
Fishersville, Greenwood, and Winchester, Va. ; Keyser, French Creek,
and Pickens, W. Va. ; and Hagerstown, Smithsburg, and Hancock, Md.
The senior author had charge of the investigations in West Virginia
and the junior author had charge in Virginia and Maryland. At
several of the points mentioned only partial or incomplete records
were obtained. The similarity of conditions at Smithsburg and
Hancock, Md., and Keyser, W. Va., to other locaUties where records
were being kept, together with a shortage of the fruit crop and the
difficulty of visiting so many places at sufficiently frequent intervals,
led to the discontinuance of operations at these points after the
first year.

NATURE AND EXTENT OF THE INVESTIGATIONS.

The work was conducted by selecting, for banding, from 10 to 15
unsprayed bearing apple trees of late ripening varieties in each
locafity. Wherever it was possible medium-sized trees with smooth
bark were chosen. In some cases such trees could not be found and
old trees with rough bark were used. The rough scales of bark were
scraped from the trunks and from the bases of the larger branches of
these old trees, but even then they were much less desirable for the
purpose than the younger, smooth-barked trees.

In the spring, before the first-brood codling-moth larvse had com-
menced to leave the fruit, burlap bauds were tied around the trunks
of the trees 2 or 3 feet above the ground, and in some cases additional
bands of the same material were placed around the bases of the larger
branches. The trees were all tagged and aa individual account kept
as to the number of larvae going under the bands to "spin up." The
bands were removed and examined at frequent intervals and the

CODLING MOTH IN CENTEAL APPALACHIAN REGION. 3

larva3 taken from them were comited and placed iu rearing jars. In
1911 the larvse were collected and the rearing jars examined every
10 or 12 days, and in 1912 and 1913 the examinations were made
every 3 or 4 days. During the course of the work more than 20,000
larvse were collected and placed in the jars for rearing.

The jars containing the larvae were supplied with small devices
made of thin pieces of wood bound together, with openings between
into which the larvae entered to "spin up." It was found that strips
cut from sheets of transparent celluloid could be used under the wood
to advantage, as this permitted the wood covering to be removed for
the purpose of examining the larvae or pupae without tearing or dis-
arranging the cocoon. The jars were covered with cheesecloth and
were placed under shelter, usually in open sheds, where they had
out-of-door temperature. These sheds were always located near the
orchard in which the larv« had been collected. The jars were exam-
ined on the same dates as the bands, and the moths that had issued
at each examination were counted and destroyed. Larvae that win-
tered were preserved and records were made of the date they issued
as moths the spring following. So far as possible the band records
were checked and supplemented by observations on the condition of
the insect in the orchard.

EXPLANATION OF THE USE OF TERMS.

The terminology of this paper is made to conform as nearly as
possible with that of previous papers on the codling moth issued by
the bureau. The term ''generation" applies to the moth in all its
stages from the egg to the adult, regardless of whether the life cycle
is completed in one season or whether the insect winters during its
development, in which case the life cycle would occupy parts of two
seasons. The term "brood" is used to designate the msect in any
of its four stages. Broods of eggs, larvae, pupae, and imagos occur
normally, with more or less seasonal regularity, in the orchards of
any given locality, and the term "brood" usually refers to the individ-
uals in the aggTegate of any particular stage of a given generation.

In the Appalachian section a fii'st brood and a partial, or prac-
tically full, second brood of larvae occur annually. In some southern
localities a small thk-d brood is possible. Some of the larvae of the
fost brood and practically all those of the second brood winter in
the cocoon. These are all spoken of as "wintermg larvae." In the
sprmg these wintermg larvae transform to "spring pupae," which in
turn develop into "spring moths." The spring-brood moths produce
"fixst-brood eggs," from which hatch "first-brood larvae." The indi-
viduals of this generation that complete their transformation during
the first season are known in their successive stages as *'fixst-brood

4 BULLETIN 189^ U. S. DEPAETMENT OF AGEIOULTUEE.

pupae" and "first-brood moths." These moths in turn produce
''second-brood eggs" and "second-brood larvae." Where "second-
brood pupae" and "second-brood moths" occur they may produce
"third-brood eggs" and "third-brood larvae."

INVESTIGATIONS AT CHARLOTTESVILLE, VA.

DESCRIPTION OF LOCALITY.

Charlottesville is situated at the foot of the eastern slope of the
Blue Ridge Mountains, at an elevation of 400 to 500 feet above sea
level. In the immediate vicinity of the city there are several large
and profitable bearmg apple orchards, as well as a considerable acre-
age of young orchards planted within the last four or five years. Its
own interests, therefore, as weU as its proximity to the large orchards
of the Blue Ridge section, make Charlottesville of considerable im-
portance as a commercial apple-growing center. Investigations of
the seasonal life history of the codling moth were carried on in this
section in 1911, 1912, and 1913. Only the work of the last two years,
however, was considered of sufficient value to be included in this
report.

INVESTIGATIONS IN 1912.

SPRING-BROOD MOTHS.

A large proportion of the larvae collected in the orchard in the fall
of 1911 succumbed to cold or disease the following winter, and the
rearmg material available for moth emergence was consequently
rather limited. On account of the small number of insects reared
and some irregularity in the observations the records are not in-
cluded in detail. Moths were fii'st observed in the rearmg cages at
Charlottesville on May 7, and at Greenwood, where conditions are not
far from those at Charlottesville, adults began appearing about May 8.
Also the sununer brood of moths emerged in the rearing cages at Char-
lottesville 45 days later (June 20), which is about the interval that
must elapse between the two broods of adults in that latitude. There-
fore we may safely assume that in 1912 the emergence of spring-brood
moths began in the orchards at Charlottesville soon after May 1 .

PIRST-BROOD MOTHS.

Table I gives the time of emergence of 247 moths that issued from
band-collected material at Charlottesville in 1912. Beginning on
June 20, emergence continued through the rest of June, the whole of
July, and about half of August. One moth emerged as late as
September 2.

CODLIlSrG MOTH IN CENTRAL APPALACHIAN REGION. 5

Table I. — Emergence of first-hrood moths of the codling moth at Charlottesville Va in

1912. (See fig. 1.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

June 20

1

5
32

1
42

6
22
15
23
12
12

5

10

30

20

7

3

0

0

1

24

28

9

July 2

13

5

17

10

21

13

25.

17

29

21

Sept. 2

25

Total

29

247

BAND COLLECTIONS.

It would be difficult to fmd a more satisfactory orchard in which
to conduct band-record experiments than the one used at Charlottes-
ville in the summer of 1912. The trees used were part of an orchard

r— ^5

^0
Co

25

k
^ ao

QQ JO

Is

i:

J

1

A

/

1

K

i

\

/

\

I

P

\

]

r

\

-\

f

\

J

f

>

/

V

LW

(\\\

nil

„

nil

nil

nil

nil

inn

nil

nil

nil

>

nil

iiN

JUJi

■JtW.

Jill

nil

JUNE JULY y^UGUS

r

- in o »o

SEPT

Fig. 1.— Diagram to illustrate emergence of fii'st-brood moths of the codling moth ( Carpocapsa pomon-
■ ella) at Charlottesville, Va., in 1912.

that had not been sprayed for a number of years. Those banded
were of the Winesap variety, about 18 years old, and carried a heavj^
crop of fruit throughout the season. In Table II are given the
collections of the season and the summarized results of the rearing
experiments.

6 BULLETIN 189^ U. S. DEPAETMENT OF AGRICULTURE.

Table II. — Number of larvae of the codling moth taken from the hands and reared at
Charlottesville, Va., in the summer of 1912 and the spring of 1913. (See fig. 2.)

Date of collecting larvae.

Number of

larvas
collected.

Number of
dead from
handling,
cannibal-
ism, etc.

Number of
moths

emerging,
1912.

Number

over-
wintering.

Number
winter-
killed.

Niunber of

moths

emerging,

1913.

June 12

12
48
49
26
34
33
26
20
20
34
27
12
20
23
26
27
37
30
45
61
60
52
80
53
32
14
2
2

12

34

38

18

21

23

17

17

19

22

15

4

5

1

17

14

11

8

11

10

9

2

1

12

11

22

26

July 1

2

2

^ 5

9

13

1

1

17

21

25

i

8
15
21
23
27
26
30
35
54
54
43
60
51
29
10

2

I

Aug. 1

2

Q

15

10

1
3

2
3

19

13

20

17

27

21

10

1

16
15
15
28
13

10

25

15

29

10
7
6
9

20
2
3
4

20

26

41

10

43

14

5
19
13

4

55

18

32

25

16

29

6

Oct. 2

2

5

-'

•Total

Percent

905
100

164
18.12

247
27.29

494
64.59

139
15.36

335
39 23

as
so

75

65
60

35
30
25
20
/5

I

I

I

r

\

\

'

\

\

1-

n

\

/

\

/

\

f

^

/

\

'

r*"

V

\

/

\

\

V

\

\

\

k

^

J

\

j'

\

1

\

y

\

/

\

[/

\

/

r//?s

T

e/t

o

OD

/

3t

■c

ON

D

B

RO

oc

>

\

MM

MM

nil

nil

III!

nil

III!

III!

III!

nil

inn

nil

nil

nil

nil

nil

inn

nil

nil

nil

nil

nil

nil

T1>U

nil

>.^f\i(\jc>) -s-NCVjCXif^ >«v(vif\it») -~-^tV|(\j(>) ■^>.

JUNE. JULY AUGUST SEPTEMBER OCT.

Fig. 2.— Diagram to illustrate band collections of larvae of the codlmg moth at Charlottesville, Va., in

1912.

Unfortunately examinations were not begun until June 12, while
larvse were doubtless leaving the fruit as early as June 5-6. Codling-

CODLING MOTH IN CENTEAL APPALACHIAN EEGION. 7

moth larvae appeared under the bands in considerable number
throughout June and July, most of those collected previous to August
1 transforming to adults the same season. After August 1 the num-
ber of larvse collected again increased considerably, the greater part
of those taken after this date spinning up and wintering. Since
summer-brood moths appeared June 20, it is reasonable to suppose
that second-brood larvae were beginning to enter the apples about
July 1. If we allow a slightly longer time than has been found by
other observers to be the minimum feeding period of the second brood,
we might expect second-brood larvae to be leaving the fruit by the
last of July to the fu-st of August. The fruit was picked shortly after
October 5 and the records discontinued, although a few of the second
brood had not finished feeding by that time.

Table II gives the results of the rearing experiments carried on
with the 905 larvae taken in the orchard in the summer of 1912. Due
to handling, cannibalism, disease, etc., 18.12 per cent were lost in the
rearing jars; 27.29 per cent emerged as moths that season; 54.59 per
cent wintered; 15.36 per cent were winter-killed; and 39.23 per cent
passed the winter and emerged as moths in the spring of 1913.

SUMMARY FOR SEASON OF 1912.

At Charlottesville in 1912 the spring-brood moths began emerging
m the early part of May. First-brood larvae began leaving the fruit
the early part of June. First-brood moths began emerging June 20,
allowmg 10 days for egg-laying and incubation; second-brood larvae
began feeding by July 1. After August 1 most of the larvae taken
under the bands belonged to the second brood.

INVESTIGATIONS EM 1913.

SPRING-BROOD MOTHS.

The emergence records of 355 moths of the spring brood at Char-
lottesville in 1913 are given in Table III.

Table III. — Emergence of spring-brood moths of the codling moth at
Charlottesville, Va., in 1913. (See fig. 3.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

Apr 18

2
2
2
7

18
78
27
42
17
55
24

May 21

21

21
11
10

8
8

1
1

21

24

24

27

27

30

30

June 2

May 3

5

6 .

8

9

11

12

Total

15 . ..

355

18

8

BULLETIN 189, U. S. DEPAETMENT OF AGRICULTUEE.

It will be remembered tliat the work of 1912 did not include a
detailed account of the appearance of the spring brood. There was,
however, very good evidence that spring-brood emergence began
that season shortly after May 1. On the whole the seasonal condi-
tions of the spring of 1913 were shghtly in advance of those of 1912,
and spring-brood moth emergence seems to have occurred about 10
days earher in the former year. Moths began appearing in numbers
on April 27-30, and maximum emergence was reached on May 3.
Moths continued to issue in jars through May and part of June,
emergence ceasing June 11. It is probable that first-brood larvae
began feeding by May 1, or 12 days after the first moth appeared in
the rearing cages.

FIRST-BROOD MOTHS.

In 1913 the first of the first brood or summer brood of moths issued
on June 14, from material taken under the bands in the orchard on
June 5. However, emergence occurred in numbers on June 23 and
reached its maximum on July 8. On the whole the graph in figure 3
probably represents fairly well the time of appearance in the orchard
of the two broods of moths at Charlottesville in 1913. An occasional
second-brood larva may have begun feeding by June 25, but it is
probable that the insects were not entering the fruit in numbers
before July 1.

Table IV. — Emergence of first-hrood moths of the codling moth at
Charlottesville, Va., in 191S. (See fig. 3.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

1
3
5
18
11
24
26
26
40
21
28
10
11

July 23

7
7
16
7
2
2
0
3
1
0
1

17

20

26

29

23

Aug. 1

26

4

30

7

July 2

10

5

13

8 .

16

11

19

14

22

17

Total

20

270

BAND COLLECTIONS.

At Charlottesville, as in the other parts of the central Appalachian
section, the short crop of fruit during the season of 1913 seriously
interfered with the work. After the dropping, which normally fol-
lows the feeding of the first brood, not enough fruit remained to
furnish food for the second-brood larvae, and the unusually small
numbers of larvae that appeared under the bands in the latter part
of the summer throw out of line completely the proportions of trans-
forming and wintering insects. The relatively small number of over-
wintering larvae given in Table V must be considered as unusual and
not as evidence of what occurs under nonnal conditions.

CODLING MOTH IN CENTRAL APPALACHIAN REGION.

, — 80
7S

70

65

60

%SS

k SO

o

\-^

30
XZS
Q) so
\ IS
l>0

1

—

1

— 1

-A

,

/

1

A

/

1

r

r

I

' A

y

>

■

/

V

K

\

A

/

/

\

r

/

I

A

J SPRING

BROOL

5^

V

^r/R3T BROoi^

/

Mn

U

iiiiliiiiliiii nil

nil iniliinilini

U

Uf

III!

iiiiniii nil nil iiu.JJiiuJi

inn

HH

^

au

ML

10 O 10 O 10
^ <VJ <Vl (^
jAPRIL

O lo o <o r>

^ >» (\1 f\| P3

June: uuly

10 O «0 O Ifl
•^ *» tU (Vj
AUGUST

Fig. 3. — Diagram to illustrate emergence of spring-brood and first-brood moths of the codliag moth at

Charlottesville, Va., in 1913.

Table V.

-Number of larvae of the codling moth taken from bands and reared at Char-
lottesville, Va., in 1913. (See fig. 4.)

Date of collecting larvae.

Number of

larvae
collected.

Number of
dead from
handling,
caimibal-
ism, etc.

Number of

moths

emerging,

1913.

Number of

larvse

over-
wintering.

6
20
33
18
35
90
37
54
85
19
23
15
10

8
10

3

1

t

2
13
3
1
8
3
6
3
2
9
1
1
5
2

2

7

11

5

19

32

10

27

52

8

3

7

4

3

3

2

4

13

22

13

16

57

27

25

31

9

20

8

5

4

7

1

1

5

1

8 .. .

11 ..

14

17

20

1

23

26

2

30

2

July 2... .

2

5

8

11 . - - »

1

14

1

17.

20..

23

26

29...

Aug. 1.. . .

1
10

1

4

3

7

3

10 . .

1
3
1
1
1

13

1

4

16

2

19. .

5

22

2

25

2

28 .

5

4

Sept. 1

1

3 .

1

6

1

4

9

2

12 .

15

10

4

6

Total :

542
100

223
41.14

270
49.82

49

9.04

77013°— BuU. 189—15-

10

BULLETIN 189, U. S. DEPAETMENT OF AGEICULTUEE.

First-brood larvae were taken from the bands on June 5, and con-
tinued to appear in increasing numbers througli the remainder of Jime
and most of July, the largest collection of the season occurring on
June 20. Since moths of the summer or first brood appeared in the
rearing cages on June 14 and m numbers by June 20, second-brood
larvae were probably entering the fruit in the field June 25-30, and,
allowing a normal feeding period, must have begun to appear under
the bands in the last of July to the first of August. A few larvae were
collected up to September 15, when the remaining fruit was picked
and the records discontinued. Figure 4 represents graphically the
numbers and time of collection of the larvae taken from the bands
during the season. In all, 542 larvae were taken from the bands, 223,

/OS

90

^ -^

-» €0

^ 30
^, /S

\

1

I

1

K

1/

1

1

\

'

I

\

J

1 r/RST BROOD^

nil Mil III! nil nil iin iiii

IIII

inr

fi¥f

?^

H

SECOND BROOD

1

kooioQ>ooioO»ooio ;;;iooioOio --looioo

■^^(\i(VjO) >*-vC\jC\j^ ~^"^f\l(\jO) >.-v(\j

JUNE JULY AUGUST SEPT.

Fig. 4.— Diagram to illustrate band collections of larvae of the codling moth at Charlottesville, Va., in

1913.

or 41.14 per cent, of which perished in the rearmg cages; 49.82 per
cent emerged as moths the same season, while 9,14 per cent spun up
and wintered. As has already been explained, the comparative
numbers of wintering and transformmg larvae given in Table V must
not be considered usual. At Charlottesville in an ordinary season a
large proportion of the first brood transfonns, giving lise to a rela-
tively large second brood, and with a fair crop of fruit the larvae of
the second brood taken under the bands should far exceed the first
in numbers.

SUMMARY FOR SEASON OP 1913.

Spring-brood moths began emergmg at Charlottesville on April 18.
First-brood larvae might be expected to have entered the fruit by
April 28-30, though not in any number until several days later.

CODLING MOTH IN CENTEAL APPALACHIAN EEGION.

11

First-brood larvae were taken under the bands Jime 5, and by August
1 probably most of them had left the fruit. First-brood moths
ai:)peared m the rearing cages on June 14, and m numbers June 23.
Second-brood larvae must have been entering fruit June 25-30, and
were leaving by the last of July to the first of August.

INVESTIGATIONS AT GREENWOOD, VA.

DESCRIPTION OF LOCALITY.

Greenwood is situated about 18 miles west of Charlottesville, in
a section of the Blue Ridge Mountains where commercial apple
growing has been well established for yeai-s. In a mountain orchard
section, such as this, there is considerable variation in the elevation
of orchard sites. The orchard in which band-record experiments
were conducted was at an altitude of about 900 feet above sea
level. The work m this section for the season of 1912 is given in part
only, the moth emergence of that summer being considered of suffi-
cient importance to find a place in this report.

INVESTIGATIONS IN 1912.

SPRING-BROOD MOTHS.

Table VI contains the emergence records of 180 moths as they
occurred in the rearing cages at Greenwood in 1912. The first visit
of the season to Greenwood was made on May 8, and the table
shows that thi'ee moths were found in the jar of wintering larvae at
that time; while these may have emerged two or three days pre-
viously, from the number appearing two days later (May 10) it can
be assumed that moth emergence was just beginning on May 8.

Table VI. — Emergence of spring-brood moths of the codling moth at
Greenwood, Va., in 1912. (See fig. 5.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

Maj' 8.

3

11
18
28
20
46

May 30

34
15
5

10

June 3. .

14

7

18

Total

22

180

26 .

Some time was spent in the orchard in an unsuccessful search for
eggs and young larvae, and their absence indicates that moths had
at least not been appearing in the field in numbers up to that time.
Maximum emergence did not occur until May 26, although moths
were appearing in some numbers during all of the period from May
10 to June 3. None emerged in the rearing cages after June 7,
although, had more insects been under observation, an occasional
adult would probably have appeared later.

12

BULLETIN 189, U. S. DEPARTMENT OF AGRICULTURE.

FIRST-BROOD MOTHS.

The first collection of larvae in 1912 was delayed until June 12,
though as none of those taken under the bands at the time had
pupated, the beginning of first-brood moth emergence was not seri-
ously affected thereby. In all 639 moths appeared in the rearing
cages between June 23 and August 28. (See Table VII.)

■80
75
70
65
GO
55
SO
^5
^O
35
30
35
20
15
10
5

i

/

f

\

\

\

\

\

\

\

\

V

\

A

/

^

\

1

(^

s/

\

\

'

\

\

1

5

PF

}IN

(?^

Bf

?o

OL

)

1

/="//?5

T i

e/?

oc

■)D

\

\

\

J

\

L

1

nil

nil

nil

mil

nil

nib

Jill

III li

fill

nil

nil

nil

nil

nil

nil

inn

nil

nil

nil

nil

nil

iW

tt++

Jin

A^AV

JUNE

JULY

AUGUST

Fig. 5. — Diagram to illustrate emergence of spruig-brood and first-brood moths of the codling moth at

Greenwood, Va., in 1912.

Table VII. — Emergence of first-hrood moths of the codling moth at
Greenwood, Va., in 1912. (See fig. 5.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

June 2.3

6
4

17
62
71
67
29
27
65
30

41
40
24
75
53
IS
9
0

27

5

July 1

9

5

13

10

17

13

21

17

24

21

28

Total

29

639

The seasonal appearance of the two broods of moths is given in
figm'e 5.

Work at Greenwood was discontinued in 1913, the transformations
of the codling moth bemg apparently so nearly the same as at Char-
lottesville that almost daily observation would be necessary to
distinguish any variation at all, and according to the plan of work
followed it was impossible to take records oftener than every three
or four days.

CODLING MOTH IN CENTRAL APPALACHIAN REGION.

13

INVESTIGATIONS AT HAGERSTOWN, MD,

DESCRIPTION OF LOCALITY.

Hagerstown, McL, is situated on a comparatively level portion
of the lower Cumberland Valley. The coxmtry is more or less roll-
ing, but the relative
differences in altitude
are not great, the ac-
tual elevation above
sea level of most
of this section being
from 500 to 600 feet.
There are a few large
orchards in the vi-
cinity, but fruit grow-
ing in a commercial
way has not received
much attention un-
til recently. How-
ever, Hagerstown is
not far from some
very important fruit-
growing districts on
the east, the west,
the north, and the
south. Band-record experiments were carried on in this section
for 1911, 1912, and 1913.

INVESTIGATIONS IN 1911.

FIRST-BROOD MOTHS.

The long intervals between observations in 1911 (10 to 12 days)
make the records of that year of rather doubtful value, and while
they are included for Hagerstown and Pickens, it must not be under-
stood that they are comparable in any but a general way to the data
obtained in the two following years' work in these sections.

Table VIII. — Emergence of first-brood moths of the codling moth at
Hagerstown, Md., in 1911. (See fig. 6.)

— /eo
/so

/4-0

130

IZO

% IIO

\^ioo
o

^ 90

ao

60

Q: so

^ 30
JO

~""

—

—

—

—

A

\

1

\

\

/

\

/

\

/

\

\

\

1

V

•

1

\

s.

ill

III!

nil

nil

III]

mil

nil

nil

nil

ml

:;>

+HW

uu.

nil

nil

OULY ^UGU3T SEPT.

Fig. 6. — Diagram to illustrate emergence of first-brood moths of the
codling moth at Hagerstown, Md., in 1911.

Date of obser-
vation.

Number
of moths
emerging.

July 12. . .

82

151

46

16

3

22

Aug. 3

14

Aug. 25

Total

298

14

BULLETIN 189, U. S. DEPARTMENT OF AGRICULTURE.

The collection of larvae from the bands, and the summer-brood
moth emergence given in Table VIII, can be better appreciated by
reference to figures 6 and 7, and it is doubtful if much could be added
bv a detailed discussion of the season's work.

INVESTIGATIONS IN 1912.

SPRING-BROOD MOTHS.

It will be noted that the records for spring-brood moth emergence
given in Table IX were obtained at Smithsburg, Md., and therefore
do not represent accurately what took place at Hagerstown. The
Smithsburg section is 9 miles east of Hagerstown, at the foot of the
Blue Ridge Mountains, and at a considerably higher elevation, and

-seo

4^30

§ 4-20

^ 350

uj 2/0
70

CV|(\jCO ^■vtViOj^) ^^C\j(\jP) ^">CVjt\j03 ^^

y

^

~

n

f

>

\

'

>

vl

V

s

N

\

y

V

i

/^/

ffS

T

i3/

?o

00

\

y

r

\

SE

C<

ON

D

a

RC

>OL

?

\

s

N

i

iUi

iUi

JUi

ilii

liii

im

mil

iiU

ilLL

Liii

iilL

ill!

III!!

III!

nil

nil

nil

nil

III!

^

TTTT

■mi

JULY

AUGUST SEPTEMBER OCT.

Pig. 7. — Diagramtoillustratebandcollectiousof larva; ofthe codling moth at Hagerstown, Md., in 1911.

the seasonal conditions at Hagerstown are somewhat in advance of
those at Smithsbm-g. However, no satisfactory record of moth
emergence was obtained at Hagerstown in the spring of 1912, and
as this was practically the only record of any value secured at Smiths-
burg, it is included in the report of the work in the former section.

Table IX. — Emergence of spring-brood moths of the codling moth at
Smithsburg, Md., in 1912. (See fig. 8.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

May 30

2
9

17
23
20

June 19

10
4

June 3

• 23 .

7

Total

11

85

15

CODLING MOTH IN CENTEAL APPALACHIAN REGION.

15

It will be seen from figure 8 that emergence began on May 30, and
reached its maximum on June 11, after which time the moths de-
creased in numbers, ceasing to appear altogether after June 23.
It would probably be safe to say that the first-brood larvae were
entering fruit by June 1, or very soon thereafter.

FIRST-BROOD MOTHS.

The emergence records of 148 moths given in Table X were obtained
from the material collected in the orchard at Hagerstown and repre-
sent fairly well the occurrence of the summer or first brood of moths
in the field. The 148 moths accounted for in tliis table comprise all
that transformed during that season of the 1,706 larvae reared, a fact

35

30

CO

K
O

5 SO
O /5

to

— 1

1

■

1

J

^

i|

\

/

I

\

\

I

/

\

\y

\

y

\

/•

/>/

?/A

,}

C

/?<

?o

D

V

\

ii/i nil

UN

nil

Mil

\

nil

b

Uii

mjt.

I

nil nil mil iiii iiii iiii niilm

rfffi^

Wll

nil

My^Y

JUNE UULV

^

"*• "^ (M <\j P> ^
AUGUST

Fig. 8.— Diagram to illustrate emergence of spring-brood moths of the codling moth at Smithsburg,
Md., and fh-st-brood moths at Hagerstown, Md., in 1912.

which probably accounts for the relatively small number of second-

l)rood larvae that appeared under the bands later in the smnmer (see

fig. 9).

Table X. — Emergence of first-hrood moths of the codling moth at
Hagerstown, Md., in 1912. (See fig. 8.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

July 13

3

36
11
13
28
10
11

5

Aug. 13

20
9

17

^ 17

21

21

25

25

29

29

2

Total

148

9

16

BULLETIN 189, U. S. DEPARTMENT OF AGRICULTURE.

First-brood moths began to emerge on July 13, and emergence
continued throughout the remainder of July and the fore part of
August. Two adults appeared as late as August 29, though emer-
gence had practically ceased August 17. The codling moth is very
sensitive to weather conditions, its development being especially
retarded by cold, and the irregularity in the emergence curve of
first-brood moths in figure 8 is due, in part at least, to extreme tem-
perature variations of the season.

Second-brood larvae probably began entering fi-uit at Hagerstown
in 1912, about July 23 to 27.

BAND COLLECTIONS.

Altogether 1,706 larvae were taken from the bands at Hagerstown
in 1912. (See Table XI.) The trees used were of the York
Imperial variety, about 15 years old, smooth bodied and loaded with
fruit. Bands were placed in the fore part of June and examinations
made every three or four days, beginning June 15.

Table XI. — Number of larvae of the codling moth taken from the bands and reared at
Hagerstown, Md., during the summer of 1912 and the spring of 1913. (See fig. 9.)

Date of collecting lar\'ae.

Number of
larvae col-
lected.

Number of
dead from
handling,
cannibal-
ism, etc.

Number

emerged,

1912.

Number
overwinter-
ing.

Number
winter-
kiUed.

Number

emerged,

1913.

June 29

11

4

7

July 1

5

58

55

144

240

183

207

228

117

97

59

35

30

15

60

30

48

16

21

16

28

8

42
28
42
15

2
10

2

16

3

75

172

137

136

151

95

79

47

30

28

5

29

22

26

7

14

12

20

6

7
3
24
109
137
100
112
40
25
36
23
11

9

9

24

27

53

44

61

75

22

18

12

5

2

10

31

8

22

9

7

4

8

2

13

51

17

63

21

25

36

29

39

55

54

9

11

13

7

17

17

21

5

25

19
2
19

7
7
8
13

4

10

30

20

Sept. 2

7

6

10

7

14

4

18..

7

22

2

Total

1,706
100

448
26.26

148

8.68

1,110
65.06

706
41.38

404

Per cent

23.68

From figure 9 it will be seen that the first larvae appeared under the
bands on June 29, the numbers gradually increasing through July.
From August 1 to 21 the collections decreased, increasing again
slightly after the latter date, and it is probable that second-brood
larvae were beginning to leave the apples about this time. Only
8.68 per cent of the first-brood larvae transformed to moths, which
explains the relatively small second brood of larvae shown in figure 9.

CODLING MOTH IN CENTEAL APPALACHIAN REGION.

17

Comparison of figures 7 and 9 would suggest that, in the relative num-
bers of the two broods of larvae appearing under the bands, the sea-
sons of 1911 and 1912 were very similar.

As has already been said, only 8.68 per cent of the 1,706 lai-vae
taken under the bands at Hagerstown in 1912 transformed to moths
that summer. The percentage of 26.26 that died in the rearing
cages from handling, cannibalism, disease, immaturity, and other
causes compares closely with that observed at other points, and
the rearing work was evidently done with as much care and under
as favorable conditions as in the locaUties where a much larger pro-
portion of the first brood transformed; 65.06 per cent wintered,
41 .38 per cent were wmter-killed, and 23.68 per cent emerged as moths

210

180
V 'SO
>J 120

30

UJ SO

30

■

A

A

'^

^

\

I

\

/

ST

B

RO

OL

\

V

/

\

\

.s

EC

O

NC

i

3/?

oc

D

nil

Kff

J\\\

III!

III!

nil

nil

inn

lUi

iUi

iiii.

UiL

/

iUi

mil

im

iUI

iUIUlL

iife

jiii

ilU

iUi

liU

iiii

iiii

OioOlnOloOlO
<U OJ P) >. V (VI (\|

JUNE JULY

AUGUST SEPTEMBER OCTOBER

Fig. 9. — Diagram to illustrato band collections of larva of the codling moth at Hagerstown, Md., in 1912.

in the spring of 1913. The percentage of winter-killed larvae at
Hagerstown was much larger than in other localities that year.

SUMMARY FOR SEASON OF 1912.

Spring-brood moths began emerging in rearmg cages at Smiths-
burg, Md., on May 30 (probably several days later than at Hagers-
towm). First-brood larvae were probably entering fruit 10 to 12
days later (soon after June 1, at Hagerstown). First-brood larvae
were leaving apples in the field from June 25 to 29 to August 17
to 21.

First-brood moths began emerging from field-collected material on
July 13. Second-brood larvae probably began feeding soon after
July 23, and were leaving the fruit in numbers soon after August 21.

77013"— BuU. 189—15 3

18

BULLETIN 189^ U. S. DEPARTMENT OF AGRICULTURE.

INVESTIGATIONS IN 1913.

SPRING-BROOD MOTHS.

Table XII gives the emergence of moths of the spring brood at
Hagerstown in 1913.

Table XII. — Emergence of spring-brood moths of the codling moth at
Hagerstoitn, Md., in 191S. (See fig. 10.)

Date of obser-
vation.

Number
of moths
emerging.

Dateof ob.se r-
vation.

Number
of moths
emerging.

May 15 2

45
22
25
81

^ 18

6

8

21

12
9

38

77
87

11

24

27

27

Total

30 '.'.

404

June 2

The first moths appeared in the rearing cages on May 15, but
maximum emergence did not occur until May 30 to June 2. Careful

90

O 60

30

IS

\

\

«

\

i

\

i

s

IN

6 •

\^

-/?

oo

D

i

N

\

IW'

llil

MM

mil

nil

nil

Mil

III!

nil

ii'iv

im,

tfff

/

nil

nil

inn iiiiliiii

BROOD

ii>rUiil1\Ami.

nil

O U) p 10 r;

U) O 10 O lO O lo
*> ^ (\J (\| Oj

JUNE.

i lo o lo r- to
s >: c\j (\j P)

JULY

Q 10 O 10 "^
"^ -^ <\J C\j P)

y^ UGU3T

Fig. 10. — Diagram to illustrate emergence of spring-brood and first-brood moths of the codling moth at

Hagerstown, Md., in 1913.

records were taken every three days up to and including June 11,
but fi'om June 11 to June 27 observations were discontinued, as indi-
cated by the dotted line in figure 10. However, of 404 moths
accounted for in Table XII, all but 81 had emerged by June 11,
and the break from then until June 27 does not seriously affect the
value of the records. Allowing 10 to 12 days for egg laying and
incubation, first-brood larvae were evidently beginning to feed by
May 25 to 27.

FIRST-BROOD MOTHS.

The relation of the two broods of moths emerging at Hagerstown
in 1913 is clearly illustrated in figure 10. Adults appeared in the
rearing jars with more or less regularity from July 8 to August 10.
Emergence ceased altogether on August 28. (See also Table XIII.)

CODLING MOTH IN CENTKAL APPALACHIAN REGION.

19

Table XIII.- — Emergence of first-brood moths of the codling moth at
Hagerstown, Md., in 191S. (See fig. 10.)

Date of obser-
vation.

Number
of moths
emerging.

Pate of obser-
vation.

Number
of moths
emerging.

July 8.

2
2
11
8
13
10
29
23
53
31

20

I
1
0
6
0
2

11

10

14

13

17

16

21

19

23

22

26

25

29

28

Total

4 ...

222

Probably a few second-brood larvse were entering fruit in the field
by July 20 to 25.

BAND COLLECTIONS.

In Table XIV are given the records of the collections and rearings
of 2,756 larvse taken under the bands at Hagerstown in the summer
of 1913.

Table XIX . — Number of larvx of the codling moth taken from hands and reared at
Hagerstown, Md., during the summer of WIS. (See fig. 11.)

Date of collecting larv;p.

Number of

larvffi
collected.

Number of
dead from
handling,
carmibal-
ism, etc.

Number of

moths

emerging,

1913.

Number
overwin-
tering.

27

3

12

38

30

78

86

136

95

181

116

150

108

105

73

109

108

101

148

121

110

26

128

92

203

HI

127

42

32

14

18

9

17

9

5

5

6

2

1

1

1

4

12

6

19

31

38

22

53

22

77

44

40

11

36

27

11

49

41

28

6

1104

16

48

34

61

8

12

4

8

5

1

3

2

8

17

18

24

34

41

24

28

14

7

4

30

July

2

9

5

6

8

35

11

21

14

57

17

49

21

100

23 .

80

26

66

29

60

Aug.

1 . .

65

4

1
3

1

61

7

70

10

80

13 .

90

16

1

98

19

80

22 .

82

25

20

28

24

31

76

Sept.

3

155

6

77

9

66

Vi . . . . ..

34

15

20

18

10

21

10

25

4

27

in

30

0

Oct.

3 ...

5

6

1

4

9

G

12

15

1

18

1

Total

2, 756
100

883
32.04

227
8.24

1,646

Per cent . . . .

59.72

1 Eaten bv mice.

20

BULLETIN 189, U. S. DEPARTMENT OF AGRICULTURE.

LarvsB began to appear on June 27, and were taken under the
bands in numbei-s through the remainder of June, all of July, and
part of August. It will be noticed that on August 25 (fig. 11) there
was a sharp decrease in the number of insects collected. Considering
the time first-brood moths began appearing in the rearing cages at
Hagerstown, and correlating with what was taking place at Win-
chester and elsewhere, second-brood larvae very likely began appear-

1 — 210

195.

180

i65

"if SO

^,35

X ISO

•^JOS

k 90

^ 7S

\ 60

i 30

n

1

;i

\

K

V

\

;

\

.

/

\

p"

J

S

I\

V

\

r

SI

I

1 1

^

V

I

1

/

\

1

1

/

1

1

ys

^ F

//?

ST

B

RO

OL

■)

\S£

Cl

ON

^K

^BROOD

1

\

<*»,

Iff^

nil

nil

nil

nil

nil

Mill

nil

Mil

nil

nil

nil

inn

nil

nil

nil

nil

nil

nil

frrt

1TTT

mi.

m

ioou)Oiooio ^■loo'oo^o -^looiooioouioioo

<\1(>) ^'^(MCVj'v '^"^(\i(\j03 "^"^(VitMt*) ^^(Vi
JUNE yJULY AUGUST SEPTEMBER OCT.

Fig. 11. — Diagram to illustrate band collections of larvae of the codling moth at Hagerstovm, Md., in

1913.

ing under the bands soon after August 25, though an unusual over-
lapping of the two broods of larvae is apparent in the collections.
Records were discontinued about October 25, though no larvae
appeared under the bands later than October 18.

The 8.24 per cent of transforming larvae taken under the bands at
Hagerstown m 1913 compares closely with the 8.68 per cent that
transfoimed in 1912. The 32.04 per cent of larvae that died from
handling, cannibalism, etc., in 1913 is much higher than has usually
been observed, due in part to the fact that one jar of larvae was
devoured by mice, and discarding consideration of this cage the loss
is brought down to 29.37 per cent. The 59.72 per cent of wintering
larvae is only slightly less than the 65.06 per cent obtained in 1912.

SUMMARY FOR SEASON OF 1913.

Spring-brood moth emergence began May 15 and closed June 27.
Allowing 10 to 12 days from emergence to hatching of first eggs, we
might expect that first-brood larvae began entering the apples May
25 to 27. First-brood larvae appeared under the bands on June 27.
First-brood moths began to emerge in the rearing cages on July 8,

CODLING MOTH IN CENTRAL APPALACHIAN REGION.

21

though not in numbers until July 1 1 to 14. Second-brood larvae were
probably beginning to enter the fruit about July 20 to 25 and were
leaving in numbers after August 25.

INVESTIGATIONS AT WINCHESTER, VA.

DESCRIPTION OF LOCALITY.

Winchester, the county seat of Frederick County, Va., is one of the
principal shipping points for a large and well-developed apple-pro-
ducing territory in the northern part of the Shenandoah Valley. The
altitude of most of the country immediately surrounding Winchester
varies from 650 to 800 feet above sea level; thus the relative variations
in elevation are not great and the seasonal conditions are fairly uni-
form for the whole section. The life-history studies of the codling
moth in this section for the seasons of 1912 and 1913 follow.

In Table XV are mcluded the emergence records of 94 moths that
issued at Winchester in the spring of 1912.

INVESTIGATIONS IN 1912.

SPRING-BROOD MOTHS.

Table XV. — Emergence of spring-brood moths of the codling moth at
Winchester, Va., in 1912. (See fig. 12.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

May 22

2

June 11

1

1

26

4

19
26
26

15

30

19

23

7

27

Total

94

The first moth appeared in the laboratory rearing cages between
May 18 and 22, though observations indicate that moths emerged
several days earher in the field. On the 24th of May eggs were rather
common in the orchard, and two newly hatched larvae were found
just entering apples. Certainly moths were emerging in the field, in
1912, not later than May 15. By May 30 first-brood larvae were ob-
served entering fruit in the orchard in considerable numbers. The
last spring-brood moth emerged Juno 27.

The fruit was unusually large when attacked by the codling moth
in 1912, and it is of some interest to note that curculio cuts and rough
spots on the apples were more frequently used by the first-brood
larvae as points of entrance than was the calyx end of the fruit.

The first of the 1912 summer or first-brood moths emerged on July 9,
Eggs were laid by moths in confinement on July 13, by moths emerg-
ing during the period from July 9 to 13, but since one moth issued

22

BULLETIN 189, U. S. DEPARTMENT OF AGRICULTURE.

July 9 it is possible oviposition began two or three days earlier in the
field. Moths emerged in the rearing cages until August 21. (See
Table XVI.)

riRST-BROOD MOTHS.

Table X.YI.— Emergence of first-brood moths of the codling moth at
Winchester, Va., in 1912. (See fig. 12.)

Dale of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

July 9

1
20
25
27
27
33

Aug. 2

25
8
. 23
18
13
8

13

6 .

17

10

20

25

14

18...

29

21

Total

228

The relation of the two broods of moths can be better understood
by reference to figure 12, where their seasonal appearance is repre-
sented graphically.

BAND COLLECTIONS.

x\ii old unsprayed orchard located about a mile south of Winchester
was used for the band-record experiments of 1912. The trees

-35

30
5:

so

k
o
/s

00 w

A

r

■I

/

r

J

f

\

1

»

L

\

f

\

\

/

\

•

f

PR

iN

\

a*

RO

Ol

?

/

/■/

/?i

T i

1

0(

^O

)

\

llkf

k

/

mil

Mil

nil

\

III!

).

III!

T>H

iUi

*ffl nil

nil

nil

mil

nil

nil

nil

nil

\

inn

A^>l y JUNE

JULY ^AUGUST

Fig. 12. — Diagram to illustrate emergence of spring-brood and first-brood moths of the codling moth at

Winchester, Va., in 1912.

were of late fall and winter varieties well laden with fruit, and
the infestation was very extensive, practically every apple being
attacked by one or more codling-moth larvae at some time during the
season.

CODLING MOTH IN CENTRAL APPALACHIAN REGION.

23

One liirra was taken under the bands on June 19. The number
collected increased throughout the remainder of June and the first
half of July. By referring to figure 13 it will be noticed that during
the fore part of August there occurred a series of very small collec-
tions, and about this time evidently most of the first-brood larvai
had left the fruit, while those of the second brood were still feeding.
On July 15 newly hatched larvae were observed entering fruit in the
field in sufficient numbers to exclude the probability of their belong-
ing to the first brood, especially since the last of the spring-brood
moths appeared on June 27. The second-brood larvae did not
hatch hi the laboratory until July 19, but this was probably three or
four days behhid field conditions. Allowing for a normal feeding

75

70
65
60

^-

^f

^40
k 35

0:25

5

"A

^

^

\

/

V

I

/

\

V

i

/

V

•^

\

/

/

\

y

\

/

»

1

/

\

/

V

^ F

IR

ST

B

R(.

?o

o\

1

St

-.c

ON

D

B

ROOL

A

1

^

y

V

ILU-

A

nil

nil

III!

nil

nil

III!

mil

nil

nil

nil

nil

III!

inn

nil

III!

nil

nil

nil

V

nil

^

t^

;;rr

TTi>

illl

u

oomoiooiooio ;;riooiooio -^looiooiooioovooin

^(\l<\Jf*) '-■^(\j«Vl'^ '~"^CVi(\jP5 ^^(Vi«\iC>) ~~"^<\iC\j
JUNE JULY AUGUST SEPTEMBER OCTOBER

Fig. 13.— Diagram to illustrate band collections of larvse of the codling moth at Winchester, Va., in 1912.

period, some of the second-brood larvoB should have been leaving
the apples about August 9 to 13. The collections increased through
the latter part of August and the first half of September. No larA'-SR
appeared under the bands after October 18.

During the season of 1912 at Winchester 798 larvse were takf^ii
from the bands and reared. Of these 27.19 per cent were killed hi
handling or were devoured by their fellows after being placed in
the rearing cages; 28.57 per cent emerged as moths of the first brood;
1.38 per cent were parasitized; 42.86 per cent of the larvae collected
wintered, and 15.04 per cent were winter killed; 27.44 per cent passed
the winter successfully and emerged the foUowhig season, while
0.38 per cent represents the proportion of parasites that issued iu
the sprhig of 1913. (See Table XVII.)

24

BULLETIN 189, U. S. DEPARTMENT OF AGRICULTURE.

Table XVII. — Number of larvae of the codling moth taken from the bands and reared at
Winchester, Va., during the summer of 1912 and the spring of 1913. (See fig. 13.)

Number
of larvse
collected.

Number
of dead
from
handling,
cannibal-
ism, etc.

Emerged, 1912.

Number
of larvse
overwin-
tering.

Number
of larv£e
winter-
killed.

Emerged, 1913.

Date of collection,
1912.

Moths.

Parasites.

Moths.

Parasites.

1

3

20

23

56

71

70

56

37

33

14

8

8

7

9

19

37

56

59

32

22

44

34

32

18

11

5

1

2

5

2

3

1
3
14
23
36
42
37
31
19
11
6
4
1

23

27

5

1

1

Julv 1

■ 5

16
24
31
16
11
17
2
1

3

4
1
3

1

1

1

6

7

5

6

3

7

6

8

14

30

52

56

18

16

27

31

26

8

5

3

1

1

1

1

1

: : : ::::i::::::::::

9

1
1

4
6
4
6
3

I

8

10

21

33

27

10

9

12

17

16

8

5

3

1

1

1

13

17

2
1
1

21

25

29 . .

9

1
1
5
7
4
3

14
6

17
3
6

10
6
2

2

13 ; .- ..

17

4
8
19
29
6
7
15
14
10

21

1

24

29

Sept 2

2

6

10

14

18

21 .

25

28

Oct. 2

5

1
4
1
3

10

15

18-

i 1 1

Total

798
100

217
27.19

228

28.57

11
1.38

342
42.86

120
15.04

219

27.44

3

Percent

0.38

SUMMARY FOR SEASON OF 1912.

Spring-brood moths began emerging in the laboratory May 18 to
22, and probably two or three days earlier in the field. First-brood
larvae began entering the fruit in the field May 24. First-brood larvse
began leaving the apples Jmie 19. First-brood moths began emerg-
ing July 9; second-brood larvse were observed entermg fruit in. the
field on July 15, and a few had finished feeding by August 9 to 13.

INVESTIGATIONS IN 1913.

SPRING-BROOD AND FIRST-BROOD MOTHS.

The seasonal conditions of the sprmg of 1913 were considerably
in advance of those of 1912, and the appearance of the spring-brood
moths was correspondingly earlier. Moths appeared in numbers on
May 6 and maximum emergence occurred tlu'ee days later.

CODLING MOTH IN CENTRAL APPALACHIAN EEGION.

25

Table XVIII. — Emergence of spring-brood moths of the codling moth at
Winchester, Va., in 1913. (See fig. 14.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

May 6

18
38

6
16
30
29

8
16
14

June 2

14
10
6
3

7
3

1

9

5

12

8

15

11

18..

14

21

17

24

20

27

Total

30

219f

Moths continued to issue in the rearing cages until Jane 20. The
iiTegularity of the emergence curve in figure 14 is due in most cases

— 65

60

55

<f) 50

Us
%4-o

^35
K30

Q. 20

1'"

1

"— *

"—

—

1

I

1

I

J

'

1

/

r

^

J

1

/

SPRIt

SG

BR

DO

D

r/R'sr\BRooo

I

/

t'^

^

I

1

V

\

ys

\

/-

1

1

nil

III!

nil

nil

Hill

nil

nil

/

nil

Ml>4iil

ilU-

4+<r

nil

MM

nn

nil

mil

nil

nil

III!

>r

jr<

iiTl>

4UJ

My^Y JUNE UULY /AUGUST

Fig. 14.— Diagram to illustrate emergence of spring-brood and first-brood moths of the codling moth
at Winchester, Va., in 1913.

to fluctuations in temperature. The first moth emergence in con-
finement occurred 16 days earlier in 1913 than in 1912, but since
adults were probably appearing m the field in 1912 not later than
May 15, we may assume that spring-brood emergence began in the
field only 10 to 12 days earlier in 1913.

The seasonal appearance of the two broods of moths can perhaps
be best appreciated by referrmg to figure 14. The emergence of 326
moths of the first brood are given in Table XIX. The fii-st adults
of this brood appeared in the laboratory in 1913 on Jmie 30, nine
days earlier than in 1912. However, not until July 5 to 8 did adults
appear in any numbers, and in reality the difference in the time of
appearance of summer, or first-brood, moths in the two seasons is

77013°— BuU. 189 15 4

26

BULLETIN 189, U. S. DEPARTMENT OP AGEICULTURE.

very slight. Maximum emergence was not attained mitil one month
later, or about August 1. The last of the first-brood moths emerged
in the rearing cages on September 1.

Table XIX. — Emergence of first-brood moths of the codling moth at
Winchester, Va., in 1913. (See fig. 14.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

June 30

1

1

3

19

10

5

9

10

16

33

45

62

Aug. 4.

28
28
37
3
5
2
2
4
2
1

July 2

7

10

8

13

11

16...

14

19

17

22

20

25..

23

29

26

Sept. 1

29

Total

Aug. 1

326

BAND COLLECTIONS.

In 1913 bands were placed on 12 old apple trees in an orchard
located about 2 miles south of Winchester, The rough bark was

75
70
6S

(t SO
^^5
^^0
^35
30
<t 35

5 fS

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L

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I

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rJ

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/

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/

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f

\

i

/

V

J

V

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57-

BROOD

SECOND^ BROOO

\

\

IIIL

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nil Mill

nil

nil nil nil nil

inn

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nnliniliinliiiiliiiiniinliiiiliiii

III!

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nil

\m

TTTt

TTH

JH*

4UI

<

^^M(Uro >sv(\j<\j<v ~^'^f\i(Vl'^ ^^(\l(Vl03 -^.^.tvi
JUA/E JULY AUGUST SEPTEMBER OCT.

Pig. 15.— Diagram to illustrate band collections of larvae of the codling moth at Winchester, Va., in 1913.

scraped down and other hiding places of the insect destroyed, and
on the whole probably most of the larvae that left the fruit durmg
the season found their way under the bands. The record of collec-
tions is given m Table XX.

CODLING MOTH IN CENTRAL APPALACHIAN REGION.

27

Table XX — Record of codling-moth larvse taken from the bands and reared at Winchester,
Va., in 1913. (See fig. 15.)

Number of
larvae col-
lected.

Number of
dead from
handling,
cannibal-
ism, etc.

Emerged, 1913.

Number

Date of collection.

Moths.

Parasites.

overwm-
tering.

2

5

22

25

27

15

38

68

60

59

43

57

84

63

38

14

23

36

26

11

19

24

IS

14

8

27

26

38

30

13

9

6

3

8

5

2

1

2

2

2

14

16

15

9

15

40

47

31

24

31

38

22

8

3

3

3

2

1

3
4
9
5
6

23

14
8

19
8
6
9
3

14
7
6

11
9
6
9
9
9
5
2

16

7

23

4

OR

29

^

8

13

1

5

14

2
5
8
11
12
3

7

17

6

20

12

23

26

26

26

29

13

4

14

7

22

15

13

4

10

15

'>2

9

9

6

11

4

19

31

11

30

13

17

9

6

23

3

8

29

5

2

1

2

1
1

1

16

1

1

Total

971
100

234
24.10

326 1 65

346

33.57

6.70

35.63

Careful examination of the bands was made, beginning about
June 1, but no larvas were taken until June 17, only two days earlier
than in 1912, m spite of the fact that the first of the sprmg -brood
moths were probably 10 to 15 days earlier than m the former season.
From June 17 the collections increased until about August 1, when the
numbers of insects collected decreased slightly, the proportion of
those wintering increasing, and probably by August 7 to 10 most of
the larvae taken were of the second brood. The fact that the second
brood did not equal the first in numbers and were somewhat irregular
in their appearance under the bands is explained by the short fruit
crop of the year.

Altogether 971 larvse were collected and reared. Of this number
24.10 per cent were killed by handling, cannibalism, etc., the loss
from this source being about the same as the 27.19 per cent that died
from similar causes in 1912; 33.57 per cent were transformed to first-

28

BULLETIN 189^ V. S. DEPARTMENT OF AGRICULTURE.

brood moths and 6.70 per cent were parasitized. The light fruit crop
already noted reduced the number of wintering lai'vse to 35.63 per
cent.

SUMMARY FOR SEASON OF 1913.

Spring-brood moths began to emei-ge May 6, and a few fii-st-brood
larvae were probably entering the fruit by May 16. First-brood
larvae began to appear under the bands in the orchard June 17, and
from these larvae a few first-brood moths emerged in the laboratory
on June 30. Second-brood larvae were probably entering fruit in
numbei*s by Jidy 15; they began leaving fruit about August 13.

INVESTIGATIONS AT FISHERSVILLE, VA.

DESCRIPTION OF LOCALITY.

Fishei-sville is the shipping point for a part of the Shenandoah Val-
ley, in which commercial fruit growing has for yeai-s been of consider-
able importance. While in approximately the same latitude as Char-
lottesville, the seasonal conditions of this section are decidedly differ-
ent chiefly on accoimt of the much higher altitude; in fact, there is a
much greater similarity of conditions between Fishersville and Win-
chester, both of which are in the Shenaadoah Valley, than between
Fishersville and Charlottesville, between which two points the Blue
Ridge Mountains intervene. Differences in humidity and other cli-
matic conditions occur between these two regions that may effect the
development of the codling moth and that may not be entirely
accounted for by differences in altitude. The band-record experi-
ments were carried on in locations 1,400 to 1,500 feet above sea level,
which is probably about the average elevation of orchards in this
section.

INVESTIGATIONS IN 1912.

SPRING-BROOD MOTHS.

In a limited way the emergence dates of 119 moths given in Table
XXI probably represent fairly well the occurrence of the spring brood
at Fishei-sville in 1912. The rearing material was collected from the
bands in the fall of 1911.

Table XXI. — Emergence of spring-brood moths of the codling moth at
Fishersville, Va., in 1912. (See fig. 16.)

Date of obser-
vation.

May 18
22
26
30

June 3

7

11

Number
of moths
emerging.

Dare of obser-
vation.

Number
of moths
emerging.

,TllnA 1 .'i

1

19

23

27

1

Total

119

CODLING MOTH IN CENTRAL APPALACHIAN EEGION.

29

Emergence began on May 18 and reached its highest numbers on
May 30, 12 days later. However, since first-brood larvae appeared
under the bands on June 11, it is probable that moths emerged in the
field several days prior to May 18. The moths continued to emerge
through the remainder of May and in lessemng number through the
most of June, ceasing to appear altogether after June 27.

The records of the appearance of 273 moths of the first brood that;
issued from band-collected material at Fishersville in the summer of
1912 are given in Table XXII.

FIRST-BROOD MOTHS.

Table XXII. — Emergence of first-brood moths of the codling moth at
Fishersville, Va., in 1912. (See fig. 16.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

July 2

5

5
7
35
30
55
35
31
26

Aug. 1

15
13
16
1
3
1

5

9

9

13

17

13

17

21 :

25

21..

Total

29

273

The work at FishersviUe in 1912 was carried on under very ideal
conditions, and July 2, the time when the first-brood moths began
emerging in the rearing cages, represents field conditions as nearly
as is possible with band-collected rearing material. The time of first
appearance for the fu"st-brood moths was seven days in advance of
Winchester, while between the first emergence of spring-brood moths
there was a four-day difference in the two sections.

Moths appeared in numbers through July and the first half of
August, attaining their maximum on July 17. The last moth ap-
peared in the rearing cages on August 21. The relative time of
appearance of the two broods of moths at Fishersville in 1912 is
shown in figure 16.

BAND COLLECTIONS.

About 12 smooth-bodied yomig York Imperial and Ben Davis
apple trees were banded at Fishersville in 1912. On the whole the
records given in Table XXIII and figure 17 represent fairly well
the time the two broods of larvae were leaving the fruit that season.
Three larvse were taken under the bands on July 1 1 and the number
increased in the succeeding collections until about July 1, when the
number gradually decreased until the fore part of August. By
August 1 a large part of the first brood had left the fnut, as is evi-
denced in the band-record curve of figure 17.

30

BULLETIN 189, U. S. DEPARTMENT OF AGEICULTUKE.

Since fii*st-brood moths emerged in the rearing cages on July 2,
larvae hatching from eggs laid by these moths might reasonably be
expected to begin feeding by July 12 to 15. After August 9 the

r—eo
ss

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U, 30
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A

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\

\

\

/

\

I

r

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1

X,

^1

J

SA

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^g]/

V

3/^OOD

J F/RST BROOD

\

IIIU

fill

Mil

Mill

nil

nil

M>

mi rill iud.

ill! nil II

nil II 1 nil

\

tiTT

Ml

inn

My4-y^ UUNE: UULY y^UGUST

Fig. 16. — Diagram to illustrate emergence of spring-brood and flrst-brood moths of the codling moth

at Fishersville, Va., in 1912.

collections increased to the middle of September. Second-brood
larvae continued to appear under the bands until November 1, when
the fruit was picked and the records discontinued.

135

ISO

105

5 90

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5 30
15

;

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D

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RO

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A

s-

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N

i

nil

III!

nil

nil

III!

nil

nil

\

^11!

nil

nil

nil

nil

nil

inn

nil

nil

nil

nil

nil

iiii

nil

nil

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'^(V|(\lP) •v^.cycvi'^ ^^(\jf\|to ~--v(V4(vi(>) -^-^AlCVjf*) "^
JUNE. JULY y^UGUST SEPTEMBER OCTOBER

Fig. 17. — Diagram to illustrate band collections of larvae of the codling moth at Fishersville, Va.,

in 1912.

In Table XXIII are recorded the numbers of larvae taken in the
orchard at different dates through the season. Altogether 1,418
larvae were collected and reared, of which 12.90 per cent were IdUed

CODLING MOTH IN CENTRAL APPALACHIAN REGION.

31

by handling or devoured by their fellows in the rearing cages; 19.96
per cent emerged as adults during the summer of 1912; 67.14 per
cent wintered and 24.19 per cent were winter killed; and 42.95 per
cent emerged as moths in the spring of 1913.

Table XXIII. — Number of larvae of the codling moth taken from the bands and reared at
Fishersville, Va., during the summer of 1912 and the spring of 1913. (See fig. 17.)

Date of collecting larvse.

Number of

larvse
collected.

Number of
dead from
eamiibal-
ism, etc.

Number of

moths

emerging,

1912.

Number of
larvse
over-
wintering.

Number of
larvse
winter
killed.

Number of

moths

emerging,

1913.

Jime 11

3

12

43

64

61

48

32

35

34

29

22

1

9

9

14

11

13

36

101

100

109

120

127

86

88

61

37

19

16

18

22

17

8

5

6

1
3
13
41
11
14
5

2

9

30

23

50

34

27

28

28

23

16

1

2

5

4

1

15

19

21

27

July 1

" .5

9

7
3
6
4

7

13

3

3

17

6

21

2

4

25

29

1

6
4

10

9

11

36

99

83

95

97

112

80

86

59

37

19

IG

18

19

16

8

5

5

6

Aug. 1

2

2

^ 5.

10

9

r

9

13

9
12
46
43
44
34
39
28
37
32
11

2

17

24

21

2

17

14

23

15

6

2

2

53

25

40

28

51

Sept. 1

63

73

9

52

13

49

17

27
26

21

25

19

28

3

13

Opt. 2

18

5

3
1

19

9

3

13

14

g

18

5

22

1

5

27

Nov. 1

2

2

2

Total

1,418
100

183
12.90

2S3
19.96

952
67.14

343
24.19

609
42.95

Per cent

SUMMARY FOR SEASON OF 1912.

Spring-brood moths began emerging in the laboratory May 18 and
probably several days earlier in the field. Ten to 12 days latei first-
brood larvae were probably beginning to enter fruit. First-brood
larvae began leaving the fruit Jmie 11. First-brood moths emerged
July 2 to August 21, and second-brood larvae probably were entering
fruit by July 12. Soon after August 5 to 9 the number of larvse
appearing under the bands increased, and most of the larvae taken
after this date may be considered to be of the second brood.

32

BULLETIN 189, U. S. DEPARTMENT OF AGEICULTUEE.

INVESTIGATIONS IN 1913.

SPRING-BEOOD MOTHS.

Figure 18 represents the occurience of 608 moths of the spring
brood that appeared in the rearing cages at Fishersvdlle in 1913.
Moths emerged first on May 3, but maximum emergence was delayed
until May 30, the emergence curve in figure 18 for Fishersville being
very different in this respect from the spring-brood cm've at Win-
chester, as it appears in figure 14. Adults continued to emerge until
June 27. (See also Table XXIV.)

Table XXIV. — Emergence of spring-brood moths of the codling moth at
Fishersville, Va., in 1913. (See fig. 18.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

May 3

6

1

3

9

11

53

28

94

91

124

81

June 5

44
10
9

22
10
7
3

2

6

8

9

11

12

14

15

17

18

20

21

24

24

27

27

Total

30 . ..

608

June 2

First-brood larvae were probably entering the fruit in the field by
May 10 to 13, from eggs laid by moths emerging May 1 to 3.

On account of the light crop of fruit in 1913 the records at Fishers-
ville for the remainder of the season are of little value and are not
included in this report

INVESTIGATIONS AT FRENCH CREEK, W. VA.

DESCRIPTION OF LOCALITY.

French Creek is located near the lower border of the Transition
Life Zone in a hilly region not far from the center of West Virginia.
Commercial apple growing is just beginning to attract attention, and
several orchards of considerable size are being planted in that general
locaUty. Bearing orchards of from 5 to 25 acres are not uncommon.
The orchards from which banding records were obtained are located
at an approximate elevation of 1,600 feet above the level of the sea.

INVESTIGATIONS IN 1911.

On June 19, 1911, 15 suitable apple trees in an orchard that had
never been sprayed were banded, but it was found that the bands
were placed too late in the season to obtain a complete record of the
time of emergence from the fruit of the first-brood larvae. The bands

CODLING MOTH IN CENTRAL APPALACHIAN REGION.

33

furnished a supply of wintering larvse to be used for emergence records
of the spring brood of moths in 1912.

Predaceous and parasitic enemies of the codhng moth were possibly
more abundant here than in any other orchard in which banding
records were made during the investigation. The second-brood
larvae were very ex-
tensively parasitized
by hairworms {Mer-
mis sp.). Of the lar-
vae of this brood, 71
out of 159, or nearly
50 per cent, died from
this cause.

The first-brood
moths began to ap-
pear in the jars on
July 5, when five were
found. The maxi-
mum was reached on
July 8, and from that
time the numbers
gradually diminished
until September 13,
when the last two of , . x, . .^ ,.t.

Fig. 18.— Diagram to Illustrate emergence of sprmg-brood moths of tne
the season appeared. codling moth at FlshersvUle, Va., in 1913.

INVESTIGATIONS IN 1912.
SPRING-BROOD MOTHS.

On account of the high mortality, due to parasites and other causes,
only about 50 wintering larvae were alive to pupate in the spring.
Pupation took place from April 22 to 28.

Table XXV. — Emergence of spring-brood moths of the codling moth at
French Creek, W. Va., in 1912. (See fig. 19.)

/30
/20

no
<ofOo
^ so
2 ao

It, 60
^ SO

X <f-o
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—

j|

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V

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W

nil

III!

nil

nil!

nil

MM

III!

V
III!

?m

m.

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

May 13

1
2
3

8

May 25

16
4
2

14

29

16

Jxmel

21

Total

36

Table XXV shows that the first moths of this brood issued on May
13, the last on June 1, and the greatest number on May 25. The
last petals were dropping from apple on May 10, so that the first moth

34

BULLETIN 189, U. S. DEPARTMENT OF AGRICULTURE.

appeared 3 days after the blossoms were off and the maximum moth
emergence occurred from 10 to 12 days later.

FIRST-BROOD MOTHS.

As indicated in Table XXVI, first-brood moths made their appear-
ance in the jars on July 20, when seven were found. The number
increased up to July 28, and from that date until August 17 maximum

r(o SO

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nil

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Siik

TKI

1 $!5^l^^'^5i2^J5^'«5i2^i2^''5^g;(];;5'^5!2

A^^y JUNE JULY AUGUST SEPT

Fig. 19.— Diagram to illustrate emergence of spring-brood and first-brood moths of the codling moth
at French Creek, W. Va., in 1912.

numbers appeared. After the latter date the numbei's decreased
until September 11, when the last one issued.

Table XXVI. — Emergence of first-brood moths of the codling moth at
French Creek, W. Va., in 1912. (See fig. 19.)

Date of obser-
vation.

Number
of moths
emerging.

emergmg.

July 20

7

7

16

11

Aug. 24 7

28 2

31..

24

28

Aug. 1

Sept. 4 2

5

9

13

17

12
4
13

11 1

Total 82

21

BAND COLLECTIONS.

About the middle of June, 12 apple trees were banded in an old
orchard that had never been sprayed. The bands were examined
twice each week. This year the larvae were later by at least a week
in beginning to leave the fruit than in 1911. The extent and dates
of the collections are set forth in Table XXVII and figure 20.

CODLING MOTH IN CENTRAL APPALACHIAN REGION,

35

Table XX\'II. — Record of codling-moth larvse collected under bands at
French Creek, W. Va., during the season of 1912. (See fig. 20.)

Date of
collection.

1
Number of
larvaj.

Date of
collection.

Number of
larvse.

Date of
collection.

Number of
larvse.

June 24..

26..

29..

July 3...

6...

10...

13...

17...

20...

24...

28...

July 31....

2
0
2

S
7
19
12
16
10
16
13
5

Aug. 5 . . .
9...

13...

17.. .

21...

24...

28...

31...
Sept. 4....

7....

11...

14...

7
8
10
12
12
6
7
5

17
11
10
11

Sept. 18...
21...
25...
28...
Oct. 2....
5....
9....
12....
16....

Total .

20
22
24
13
8
14
8
5
2

339

The fii-st two larvse were found on June 24. After June 26 the
numbers increased with each collection until July 10. From that

30

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\

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V

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/

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V

/

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\

/

y

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V

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nil

nil

SI

ll!l

- £

nil

Jill

■)OD

mil nil

M

mi

nii

mi

mil

5

Jill

iUl

o

Jill

NL

nil

nil

9/r

lllJ

0(.

nil

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oiootooiooix) X: U) o<ooio X'lcOiooiooioO'oo

(\j(\40) ^^(\j(\j^ ^^t\j(\jn ^^(\J(Vj« "^^(Vj

'UNE JULY AUGUST SEPTEMBER OCT.

Fig. 20.

-Diagram to illustrate band collections of codling moth larvae at French Creek, AV. A^'a., in

1912.

date until July 28 the size of the collections remained fairly constant.
Collections were smaller from July 31 to August 13, after which time
they increased until September 25, decreasing thereafter until Octo-
ber 16, when the last two were taken.

INVESTIGATIONS IN 1913.

SPRING-BROOD MOTHS.

The details of the spring-brood moth emergence are set forth m
Table XXVIII and are also shown graphically in figure 21.

36

BULLETIN 189, U. S. DEPARTMENT OF AGBICULTURE.

Table XXVIII. — Emergence of spring-brood moths of the codling moth at
French Creek, W. Va., in 1913. (See fig. 21.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

May 6

1
11

4
18
25

4
11

9
19

11
0
8
6
5
2

10

10. ..

13

14

17

17

20

21.

24

24

27

31 . .

Total

134

June 3

30

BROOD

O 10 Q ^
-V -^ C\j (\J

A^A Y

«*)

OloOU)OloO'0
(Vj (\j Pj V ^ (\j (\|

JUNE JULY

0)

U)

VO

y^ UG

Fig. 21. — Diagram to illustrate emergence of spring-brood and first-brood moths of the codling moth
at French Creek, W. Va., in 1913.

The first moth was found in the jars on May &, the maximum num-
bers from May 17 to June 7, and the last on June 24. A freeze
occurring on the night of April 20 caught the apple trees just coming
into full bloom, practically destrojdng the entire crop of blossoms.
The first moth appeared 16 days after the date of the freeze, and the
maximum emergence was a little more than four weelcs after the
freeze.

FIRST-BROOD MOTHS.

Owing to the light crop of apples only a few larvae were obtained,
and the number . of first-brood moths emerging was insignificant.
Table XXIX shows the number that were obtained.

CODLING MOTH IN CENTRAL APPALACHIAN EEGION.

Table XXIX. — Emergence of first-brood moths of the codling moth at
French Creeh, W. Va., in 1913. (See fig. 21.)

37

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

July 23

2

6

20

2

Aug. 6

6
5

26.

9 .

30

Total

Aug. 2

41

It will be seen from this table that only 41 first-brood moths were
obtained. Of these the first emerged on July 23, the maximum num-
ber on July 30, and the last on August 9.

BAND COLLECTIONS.

A period of cold, occurrmg April 20 and 21, when the temperature
dropped to 20° F.^ followed by another drop to 25° F. on the night
of May 10, destroyed practically aU the apple crop in the locality.
One old orchard containing a few bearing trees that were not sprayed
was found and eight of the trees were banded on July 1. Table XXX
shows the number of larvae collected under these bands.

Table XXX. — Record of codling-moth larvse collected under hands at French Creeh,

W. Va.^ in 1913.

Date of collection.

Number
of larvse.

Date of collection.

Number
of larvse.

Date of collection.

Number
of larvse.

July 5

6
17
19
18
5
8
10
3
1

Aug. 6

6

4
7
6
7
6
4
4
2

Sept 6

4
1
2
2
0
1

9

12

9

10

13

13

16

15.

17

19

20

20

23

23

24

26

27

Total

30

30

Sept. 3

143

Aug. 2.

This table shows that the first larvae were found under the bands
on July 5, the greatest number, which was 19, on July 12, and the
last on September 24. The second-brood larvae were few in number,
the collections being nearly uniform from August 6 to 23, after which
time they decreased until the last was found.

INVESTIGATIONS AT PICKENS, W. VA.

DESCRIPTION OF LOCAUTY.

The orchard at Pickens in which banding records were obtained in
1911 and 1912 is located in a mountainous region at an elevation of
3,500 feet above the level of the sea. The native flora and famia of
the immediate locahty indicate the junction of the Transition and

38

BULLETIN 189, U. S. DEPAKTMENT OF AGRICULTURE.

Canadian Life Zones. Fruit growing is not extensively engaged in,
although a considerable quantity of apples is produced and disposed
of in lumber camps and other local markets.

The codhng moth was less abimdant here than in other localities
where banding records were made. This was probably due to the
higher elevation and the consequently shorter breeding season. Data
were collected only in 1911 and 1912, the apple crop bemg an entire
failure in 1913.

INVESTIGATIONS IN 1911.

On the 22d of Jmie, 18 apple trees were banded in the orchard of
Mr. Lewis Wunchner, 4 miles southeast of the village of Pickens. -

The orchard had
never been sprayed
and most of the trees
banded were bearing
heavy crops of fruit.

BAND COLLECTIONS.

The first larvae were
foimd under the bands
on July 7, on which
date 27 were collected.
The maximum num-
ber were f oimd on July
19. The last were
found on September
29, at which time the
fi-uit was gathered
from the trees by the
owner of the orchard.
The number of larvae found had dropped from 75, on September 11,
to 17 on September 29, and it is probable that only a few more indi-
viduals would have gone imder the bands had the fruit remained on
the trees longer. The details of the band collections are shown more
fully in Table XXXI.

Table XXXI. — Record of codling-moth larvae and pupss collected under bands
at Pickens, W. Va., in 1911.

1 — 2S

15

K

to

05 S

5

/

/

\

1

^

\

/

\

iui

L

\

nil

Till

III!

III!

Mil

I

TTH

Jill

mil

^ u

JUNE JULY

Fig. 22. — Diagram to illustrate emergence of spring-brood, moths of
the codling moth at Pickens, W. Va., In 1912.

Date of collection.

July

7

19

29

Aug.

8

18

28

Sept

11

29

Total number collected.

Number
of larvffi.

Number
of pupae.

Total.

27
118
43
29
61
29
75
17

Number

of larvffl

wintering.

Per cent

of larvse

wintering.

3.5
13.9
51.7
77
79.3

100

100

CODLING MOTH IN CENTEAL APPALACHIAN EEGION.

39

FIRST-BROOD MOTHS.

Table XXXII shows that of the 59 first-brood moths reared the
fii-st were found in the breeding jars on July 29, the maximum num-
bers from August 8 to 28, and the last on September 11.

Table XXXII. — Emergence of first-hrood moths of the codling moth at
Pickens, W. Va., during the season of 1911.

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

July 29

Aug. 8

14
20
19

Aug. 28

Sept. 11

5

1

18

Total

59

INVESTIGATIONS IN 1912.

In 1912 the same orchard was used for the banding records as in
1911, although in most cases different trees were banded. Twelve
trees were used.

SPRING-BROOD MOTHS.

Table XXXIII indicates the numbers and dates of emergence of
this brood of moths at Pickens.

Table XXXIII. — Emergence of spring-brood codling moths at Pickens,
W. Va., during the season of 1912. (See fig. 22.)

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Number
of moths
emerging.

June 13

17

21

25

5
3

1

15
21

July 3

17
8
1
1

8

12

17

Total

29

72

Moths from the larvae that had wintered in the rearing jars did not
begin to emerge until nearly the middle of June, as is shown in the
table. The first were found in the jars on Jime 13, the greatest num-
bers from June 25 to July 3, and the last on July 17.

BAND COLLECTIONS.

Larvae were exceedingly scarce, as is shown in Table XXXIV, only
47 being taken under the bands during the entire season. The first
was found on July 24 and the last on October 5. The numbers are
so few that no distinct line can be drawn between the first and second
broods.

40

BULLETIN 189, U. S. DEPARTMENT OF AGEICULTURE.

Table XXXIV. — Record of codling-moth larvse collected under bands at
Pickens, W. Va., during the season of 1912.

Date of
collection.

Number
of larvse.

Date of
collection.

Number
of larvae.

Date of
collection.

Number
of larvse.

July 24..
30.-

1
2

Aug. 24..

28..

31..
Sept. 4..
7

11..

14..

2
1
4
3
2
5
1

Sept. 18..

21..

25..

28..
Oct. 5..

Total..

7
1
5
5
2

10..
14..
17..

21..

2
1

1
2

47

INVESTIGATIONS IN 1913.

SPRINO-BROOD MOTHS.

Of the 47 larvse collected in 1912, 28 wintered and transformed
to moths in 1913. Table XXXV shows the time of emergence.

Table XXXV. — Emergence of spring-brood codling moths at Pickens,
W. Va., during the season of 1913.

Date of obser-
vation.

Number
of moths
emerging.

Date of obser-
vation.

Nimiber
of moths
emerging.

June 21

0

8
8

July 1

8
4
0

24

5

8

28

Total

28

The jars in which the larvse had wintered were examined twice a
week and on June 24 eight moths, which were the first of the season,
were found. The same number were found on June 28, and also on
July 1. The last were found on July 5.

RESUME OF REARING EXPERIMENTS IN MARYLAND, VIRGINIA, AND

WEST VIRGINIA.

Tables XXXVI and XXXVII summarize the rearing experiments
of 1912 and 1913 in the different localities.

Table XXXVI. — Resume of rearing experiments on the codling moth at five points in
Virginia, West Virginia, and Maryland in 1912.

Observation.

Hagers-
town, Md.

Winches-
ter, Va.

Fishers-
ville, Va.

Charlottes-
ville, Va.

French
Creek,
W. Va.

Total.

Num-
ber.

Per

cent.

Num-
ber.

Per
cent.

Num-
ber.

Per

cent.

Num-
ber.

Per
cent.

Num-
ber.

Per
cent.

Num-
ber.

Per

cent.

Larvae collected

1,706

448
148

404

1,110

706

100.00

26.26

8.68

23.68
65.06
41.38

798

217
228

219

342

120

14

100.00

27.19

28.57

27.44

42.86

15.04

1.76

1,418

183
283

609
952
343

100.00

12.90
19.96

42.95
67.14
24.19

905

164

247

355
494
139

100.00

18.12
27.29

39.23
64.59
15.36

339

80
82

134

172

38

5

100.00

23.60
24.19

39.53

50.74

11.21

1.47

5,166

1,092

988

1,721

3,070

1,346

19

100.00

Larvse dying from hand-
ling, caimibalism, etc

Moths reared same season . .

Moths reared following sea-
son

21.12
19.12

33.31

Wintermg larvse

59.42

Winter-killed larvse

26.06
.36

CODLING MOTH IN CENTBAL APPALACHIAN KEGION.

41

Table XXXVII. — Risume of rearing experiments on the codling moth at four j)oints in
Virginia, West Virginia, and Maryland in 1913.

Observation.

Hagers-
town, Md.

Num-
ber.

Per
cent.

Winches-
ter, Va.

Num-
ber.

Per
cent.

Charlottes-
ville, Va.

Num-
ber.

Per
cent.

French
Creek,
W. Va.

Num-
ber.

Per
cent.

Total.

Num-
ber.

Per

cent.

Lan'se collected

Larvae dying from handling, cannibal-
ism, etc

Moths emerging same season

Wintering larvae

Parasitized larvae

S83

227

1,646

32.04
8.24
59.72

971

234

326

346

65

100.00

24.10

33.57

35.63

6.70

542

223
270

49

100.00

41.14
49.82
9.04

100.00

33.58

28.67

35.66

2.09

4,412

1,388

864

2,092

100.00

31.46

19.58

47.38

1.55

It will be noted that the proportion of larvae dying in the rearing
cages, due to handling, cannibalism, disease, etc., varied from 12.90
per cent to 41.14 per cent. The latter figure, however, is unduly
high, the average loss from this source being 21.12 per cent in 1912
and 31.46 per cent in 1913. The proportion of larvae transforming
the same season as that in which they were collected varied from
8.24 per cent at Hagerstown to 49.82 per cent at Charlottesville,
with an average of 19.12 per cent in 1912 and 19.58 per cent in 1913.
For 1912 from 42.86 j^er cent to 67.14 per cent of all larvae collected
spun up and wintered, the average for all points being 59.42 per
cent. The proportion of win term^ larvae in 1913 was abnormally
small on account of the light fruit crop of that year. Loss from
winter killing amounted to from 11.21 per cent to 41.38 per cent,
the average for all points being 26.06 per cent. Observations on
parasitism were made only at Winchester and French Creek, the
highest recorded being 6.70 per cent at Winchester in 1913. It must
be remembered, however, that the foregoing facts are taken from
observations of insects kept m confinement, and only in a limited
way indicate what occurs under normal out-of-door conditions.

Table XXXVIII gives the numbers of codling-moth larvae col-
lected and reared in the course of the work in the different localities.

Table XXXVIII. — Number of codling -moth larvx collected and reared in the different
localities in Virginia, Maryland, and West Virginia during 1911, 1912, and 1913.

Locality.

Year.

Number of
larvae col-
lected and
reared.

Locality.

Year.

Number of
larvae col-
lected and
reared.

1911
1912
1913
1911
1912
1911
1912
1911
1912
1913

1,218

905

542

1,979

1,862

910

1,418

2,079

798

971

19U
1912
1913
1911
1912
1913
1911
1912

1,761

French Creek, W. Va

1,706

2,756

633

Fishersville, Va

Pickens, W. Va

339
143

399

Winchester, Va

Total

47

20, 466

42 BULLETIN 189, U. S. DEPARTMENT OF AGRICULTURE.

NUMBER OF FIRST-BROOD LARV^ TRANSFORMING FIRST SEASON.

Table XXXIX shows the numbers of transforming and wintering
band-collected larvae of the first brood for several localities. These
data are tabulated for their value in determining the relative size of
the second brood of larvae.

Table XXXIX. — Number of first-brood larvse of the codling moth transforming to moths

the first season.

Locality.

Year

Number of
first-brood

larvse
living to
transform.

Number of
first-brood

larvae
transform-
ing first
season.

Per cent
transform-
ing first
season.

Number of
first-brood

larvae
wintering.

1912
1913
1912
1913
1912
1912
1913
1911
1911
1912
1911

259
278
1,122
1,356
308
206
476
226
202
93
154

247
269
147
227
278
228
325
221
201
81
59

95.37
96.76
13.19
16.74
90.26
85.71
68.28
97.78
99.50
87.10
38.31

12

Do

9

974

Do

1,129

Fishersville, Va

30

38

Do

151

5

French Creek, W. Va

1

Do

12

Pickens, W. Va

95

Total

4,740

2,284

48.19

2,456

Since an indeterminate number of larvae always die in the jars on
account of artificial conditions,* only those that hved to emerge as
moths are considered in this table. It will be seen that there is a great
variation in the percentage of the larvae wintering in the different
locahties, and that in no case did all the first-brood larvae transform
to moths the first season. At Charlottesville, Fishersville, Keyser,
and French Creek the proportion transforming the first season was so
great as to insure nearly a full second brood of larvae, while at Hagers-
town and Pickens the large proportion wintering would indicate only
a partial or scant second brood.

Where the banded orchards were bearing a full crop of fruit and
other conditions were favorable for normal development of the larvae,
the relative sizes of the first-brood and second-brood band collections
support the conclusions to be drawn from the data given in the table.

EFFECT OF DIFFERENCES IN ALTITUDE AND LATITUDE UPON THE DE-
VELOPMENT OF THE CODLING MOTH.

The stations at which the codUng-moth rearing work reported in
this paper was conducted comprise a range in altitude of 3,100 feet and
in latitude of practically 1° 40', or about 115 statute miles. In
correlating the data from the various stations an effort has been made
to determine whether or not definite differences in altitude and
latitude have a corresponding and constant effect on the time of
metamorpliic changes in this species of insect. The results indicate

CODLING MOTH IN CENTKAL APPALACHIAN KEGION.

43

that the codUng moth in its development is so responsive to transient
weather conditions and other local cUsturbing factors that the time of
appearance of a certain brood in one locality can not be determined
with certainty by any mathematical calculation based on the known
time of appearance of the same brood in another locality of a known
difference in altitude or latitude. It is probable that local differences
in humidity, susceptibiUty to sudden changes in temperature as
effected by topography, and, possibly, soil conditions, are more or
less direct factors influencing the time of developmental changes in
the insect.

In Table XL the results of these observations are given. In this
table use is made of the law laid down some years ago by Dr. A. D.
Hopldns that in phenological phenomena a fourth of a degree of lati-
tude, or 100 feet in altitude, is equal to one day of time. The table
shows that in this particular case the law does not apply. Charlottes-
ville, being at the lowest altitude and the most southerly of thestations,
is taken as a base and the other points considered in their relation
thereto. In considering this table it should be borne in mind that
data were collected but twice a week and that the dates given for the
first appearance of the insect in its various stages may be from one to
three days later than the actual occurrence. Differences in latitude
that are equivalent to less than half a day are not considered; those
equivalent to more than half a day are counted as full days.

Table XL.- — Effect of differences in altitude and latitude on the time of appearance of
spring-hrood and first-hrood codling moths and first-brood larvse.

Locality.

Year.

Date of
emer-
gence of

first
spring-
brood
motlis.

Date of

first

larvae

collected

under

bands.

Date of
emer-
gence of
first-
brood
moths.

Elevation

above sea

level.

Elevation
above

Charlottes-
ville.

Charlottesville, Va...

Greenwood, Va

Hagerstown, Md

Winchester, Va

Fishersville, Va

French Creek, W. Va
Pickens, W. Va

1912
1913
1912
1913
1912
1913
1912
1913
1912
1913
1912
1913
1912
1913

May 7
Apr. 18

May 8

June 6
June 5
June G

June 20
June 14
June 23

Feet.

400
400
900

May 30
May 15
May 22
May 6
May 18
May 3
May 13
May 6
June 13
June 24

June 29
June 27
June 19
June 17
June 11
June 14
June 24
July 5
July 31

July 13

July 8

July 9

June 30

July 2

July 20
July 23
Aug. 20

500

550

750

750

1,500

1,500

1,600

1,600

3,500

Feet.

500

100

150

350

350

1,100

1,100

1,200

1,200

3,100

44

BULLETIN 189, U. S. DEPARTMENT OF AGEICULTURE.

Table XL. — Effect of differences in altitude and latitude on the time of appearance of
spring-brood and first-brood codling moths and first-brood larvx — Continued.

Locality.

Charlottesville, Va

Greenwood, Va

Hagerstown, Md

Winchester, Va

Fishersville, Va

French Creek, W. Va
Pickens, W. Va

Year.

1912
1913
1912
1913
1912
1913
1912
1913
1912
1913
1912
1913
1912
1913

Distance north of
Charlottesville.

Degrees

and
minutes.

Miles.

0

4

5

1

40

115

1

10

80

0

4

5

0

50

60

0

40

45

Number
of days
later
than
Char-
lottes-
ville
accord-
ing to
law of
latitude

and
altitude.

Actual number of days later
than Charlottesville.

First
spring-
brood
moths.

7

23

7

27

8

15

8

18

11

11

11

15

15

6

15

18

34

37

34

67

First
larvoe
imder
bands.

Same day

First

summer-

l)rood

moths.

RELATIVE NUMBERS OF LARV^ ASCENDING AND DESCENDING THE

TREES.

In 1911 several trees in a number of orchards were banded around
the trunks and also around the bases of the larger branches. The
lower bands were used to secure larvae that had dropped with the
infested fniit and ascended the trunk to spin up, and the upper
bands were used for those that left the fruit before it dropped and
descended toward the trunk for the same purpose. The following
table shows the relative number of larvae secured under the two sets
of bands in the six orchards. In considering Table XLI due allow-
ance should be made for an unknown number of larvae that crawled
across the bands or that spun up under the bark before reaching the
bands.

Table XLI. — Relative numbers of codling-moth larvx collected from bands around the
trunks and bases of branches, seaso7i of 1911.

Locality.

Number of larvae collected.

On trunk.

On
branches.

Total.

Per cent.

On trunk.

On
branches.

Hagerstown, Md

Smithsburg, Md

Hancockj Md

Fishersville, Va ,

French Creek, W. Va
Pickens, W. Va

Total ,

543
179
75
96
146
29

602
619
91
68
96
30

1,145
798
166
164
242
59

47.42
22.44
45.18
58.54
60.33
49.15

52.58
77.56
54.82
41.46
39.67
50.85

1,068

1,506

2,574

41.49

58.51

CODLING MOTH IN CENTRAL APPALACHIAN EEGION. 45

SEASONAL EFFECT OF WEATHER CONDITIONS ON THE DIFFERENT
STAGES OF THE CODLING MOTH.

The beginning of emergence of the spring-brood codhng moths
varies greatly from season to season, depending in any given year
upon the temperature conditions that prevail during March, April,
and May.

It will be noted, however, that in spite of the wide variation in the
time of emergence of the spring-brood moths in 1912 and 1913 there
was a tendency for the later stages of the insect to appear at more
nearly the same periods both years. This is probably due to an
equahzation of midsummer weather conditions subjecting the later
stages of the insect to the influences of a more constant seasonal
temperature factor. At Winchester, where the codling moth was
under closer observation than at other points, we find that while
spring-brood moths emerged at least 10 days later in 1912 than in
1913, the second-brood larvae began entering the fruit at practically
the same time both years.

Hammar,^ in his report on the codhng moth in Pennsylvania, gives
the following in his general summary:

The time of the emergence of the spring brood of the moths is variable under differ-
ent seasonal conditions and depends largely upon the relative lateness of the spring.

The time of emergence of the summer brood, or first brood, of moths is fairly constant
and generally commences about the 1st of August.

From the results of the band records and rearing work of 1912 and
1913 it would seem, therefore, that in all except very unusual seasons
we may expect the feeding of second-brood larvae to begin in the
different sections about as follows: Charlottesville, Va., July 1;
Fishersville, Va., July 10; Winchester, Va., July 15; Hagerstown,
Md., July 25.

CANNIBALISM AMONG CODLING-MOTH LARV^.

During the progress of these studies it was noticed frequently that
when a collection of codUng-moth larvae was confined m a rearing j ar
a considerable loss m their nmnbers from cannibahsm was likely to
occur. This habit, of the stronger larvae devouring their weaker
fellows, has been commented on by Hammar.^ He states that can-
nibahsm among the larvae probably takes place also imder normal
conditions. In the jars the loss from this cause during the present
investigations was frequently sufficient to amount to a considerable
factor in influencing the number of moths to appear later.

1 Hammar, A. G. The codling moth in northwestern Pennsylvania. U. S. Dept. Agr., Bur. Ent., Bui.
80, Pt. VI, p. Ill, 1910.

2 Hammar, A. G. Life-history studies on the codling moth in Michigan. U. S. Dept. Agr., Biu'. Ent.,
Bui. 115, Pt. I, p. 1-86, 1912. See p. 83.

46 BULLETIN 189, U. S. DEPARTMENT OF AGKICULTUEE.

NATURAL ENEMIES.

PREDACEOUS INSECTS.

It seems probable that many codling-moth larvae, after leaving the
fruit, are caught and destroyed by ants. A small red ant (Solenopsis
molesta Say) was frequently met with on the bark of apple trees and
under the bands engaged in killing and devourmg the larvae. Colonies
of these ants that had their homes in the vicinity of banded trees
seemed to form a habit of visiting the bands to obtam food. The
collections of larvae from trees in several locahties were very consid-
erably reduced in numbers from this cause. Lasius niger L. var.
americana Emery, a species less abundant about the trees than the
other, was also found killing the larvae. These ants were determined
by Prof. W. M. Wheeler.

Several species of beetles were found to be predatory on the larvae
and pupae at the various stations. The most abundant of these was
Tenehroides corticalis Melsh., both the larvae and adults of which were
frequently fomid under the bands devouring the larvae and pupae.
Another beetle, Hololepta lucidaljec. (PI. I, fig. 2), was found at Win-
chester with a codling-moth lai'va in its jaws. Two species of carabid
beetles {Cdlanthus opaculus Lee. and Platynus angustatus Dej.) were
common under the bands but were not observed to be feeding on the
codling-moth larvae. These beetles were determined by Mr. E. A.
Schwarz, of the Bureau of Entomology. A coleopterous larva, which
was determmed as a species of Telephorus by Mr. H. S. Barber, was
observed in the act of eating a codling-moth larva at Hancock in 1911.

HYMENOPTEBOUS AND DIPTEROUS PARASITES.

Six species of hymenopterous parasites were reared from the cod-
ling-moth larvae in the jars. Of these, Ascogaster carpocapsx Vier.
(PI. I, fig. 1) Was found at Winchester, Hagerstown, Smithsburg,
Keyser, and French Creek, and outnumbered all others. An undeter-
mined secondary parasite was found to be destroying this species in
considerable numbers at Keyser m 1 91 1 . Itopledis marginatus (Prov.)
(fig. 23) occurred at Greenwood, Ilagerstown, Winchester, and French
Creek. A female of this species was observed on the trunk of an apple
tree at French Creek ovipositing in a larva that had spun up under a
scale of bark. Macrocentrus sp.^ was reared at Greenwood in July,
1911; Meteorus sp.,^ at French Creek m July, 1913 ; ( Microdus) Bassus,
n. sp. (PL I, fig. 4), at Smithsburg m July, 1911; and Phanerotoma
tibialis Hald. at Charlottesville m 1911. The last species was deter-
mmed by Mr. H. L. Viereck and the others by Mr. R. A. Cushman,
of the Bureau of Entomology.

1 Quaintance No. 7457. 2 Quaintance No. 7569.

CODLIISTG MOTH IN" CENTRAL APPALACHIAN EEGION.

47

A dipterous parasite, reared from codling-moth larvae at Keyser in
1911, was determined by Mr. W. E. Walton, of the Bureau of Ento-
mology, as (Hypostena) TachinopJiyto variabilis Coq. (PL I, fig. 3).
Only a few specimens of this species were obtained.

HAIRWORM PARASITES.^

Hairworm parasites of the codling moth (PL I, figs. 5, 6) were found
at Greenwood, Keyser, and French Creek, being abundant m the
second-brood larvae at the latter place m 1911. These parasites were
within the bodies of the codling-moth larvae at the time collections

Fig. 23. — Itopledis marginatus, a parasite of the codling moth. Enlarged. (Original.)

were made from the bands and usually issued from their hosts 10 days
or 2 weeks after the larvae were placed in the rearing j ars. Occasionally
dead larvae, surrounded by a mass of dead hairworms, were found under
the bands, and in a few cases the hairworms were found within apples
borne by the banded trees. It was evident that mfestation occurred
at an early stage in the larval development and that all infested indi-
viduals died as full-grown larvae. Most of the parasitized larvae died
within 10 days after being placed in the rearing jars.

The hairworms v»^ere from 2J to 5 inches in length, and three or
four were frequently observed to inhabit one larva. In leaving the
host they passed through the anal opening or broke through the

3 Mcrmis sp. Material was referred to Dr. B. H. Ransom, of the Bureau of Animal Industry, Init as
the specimens were all immature, they could not be determined specifically.

48

BULLETIN 189, V. S. DEPARTMENT OF AGRICULTURE.

skin at some other point. After freeing themselves from the host,
all that were observed wiithed about actively for a few minutes
and then died. Many of the hairworms did not escape from the
codling-moth cocoons, but were found, at the time of the regular
examinations of the jars, knotted together and dead, beside the
flattened and shriveled larval remains. Table XLII shows the
extent of parasitization at French Creek in 1911.

Table XLII.- — Extent of parasitization of codling-moth larvse by hairworms at French

Creek, W. Va., in 1911.

Date larvEe were collected.

June 26

Julys

July 14....
July 24...-

Aug. 4

Aug. 15

Aug. 23...-

Sept. 2

Sept. 13

Sept. 19.--
Oct. 3

Total

Number
of larvae
collected.

139
68
48
24
14
51
34
36
43
23
22

Number

of larvse

parasitized.

Per cent
parasitized.

12.50
4.17
21.43
13.72.
32. 35
63.90
48.84
43.48
27.27

17.53

SUMMARY.

The foregoing account of the codUng moth is based upon band-
record studies conducted in 1911, 1912, and 1913 in several different
localities of Virginia, West Virginia, and Maryland.

The stations at which the investigations were conducted comprise
a difference in latitude of about 1° 40' and in altitude of about
3,100 feet. The most southerly and least elevated station was at
Charlottesville, Va., the most northerly at Hagerstown, Md., and
the one at highest elevation at Pickens, W. Va.

The chief features of the investigations consisted of banding
suitable apple trees with strips of burlap, collecting at regular periods
the larvae that went beneath the bands to spin up, and rearing these
larvse in jars kept in, the locahties where the larvse were collected.
Examinations of the bands and rearing jars were made every week
or ten days in 1911 and twice a week in 1912 and 1913. No detailed
life-history studies were attempted.

During a single year the codling moth, in the region covered by
the present studies, produces one fuU brood of larvse and a partial
second brood, the size of the second brood depending more or less
on the latitude and altitude of the locality.

The studies show a marked difference in the time of appearance of
the different broods in different localities. Charlottesville gave the
earliest records for practically all broods and Pickens the latest.

Plate

Natural Enemies of the Codling Moth (Carpocapsa pomonella).

Fig. 'i.—Aseof/astrr carpncapsae. Fig. 2.—JIolol(j>ta lucidd devonring codling-moth larva.
Fig. 3.— {Ili/pot-Uixi) Tarhinophyio variabilis. Vig. ■l.—i.Uicrailti.'i) Bafsus n. sp. Fig. 5.—
Codling-moth larvte killed in cocoons by hairworms (.l/( )■»//*■ sp.). Fig. 6. — Mass of hair-
worms {Mcrinis sp.) taken from rearing jar, French Creek, VV. Va. (Original.)

CODLING MOTH IN CENTKAL APPALACHIAN EEGION. 49

There seems, however, to be no constant rate of difference between
the earher and later locaUties. This seems to be largely due to the
responsiveness of the species during its metamorphic changes to
local and transient weather conditions.

During the time of the investigation the first-brood larvae began
entering the fruit at Charlottesville from April 28 to May 15, and
second-brood larvae from June 25 to July 1. At Pickens first-brood
larvae began entering the fruit from June 20 to July 1, and second-
brood larvae about August 10. Between these two localities there
is a greater difference in the time of the regular periodical changes
of the insect that occur late in the season than of those that occur
early in the season. This is probably due to the cumulative retard-
ing effect of the more frequent unfavorable weather conditions at
the higher point.

For any given locality the variation in the time of appearance of
spring broods in different years is greater than that of correspond-
ing summer and fall broods of the same years.

Records of the numbers of larvae collected from trees on which
bands were placed around the trunks and also aromid the bases of
the larger branches indicate that 41.49 per cent drop to the ground
and then ascend the trunk to pupate and 58.51 per cent crawl down
the branches from the infested fruit to pupate.

Where a collection of larvae is confined in one jar there is apt to be
a considerable loss due to cannibalism. It is probable that the weaker
larvae are sometimes devoured by their fellows under normal con-
ditions.

Two specimens of ants (Solenopsis molesta Say and Lasius niger
L. var. americana Emery) were found in several locaUties devouring
codhng-moth larvae. Larvae and adults of the beetle Tenebroides
corticalis Melsh. were found frequently feeding on codUng-moth
larvae and pupae. Six species of hymenopterous and one of dip-
terous parasites were reared in the jars. Of these the most de-
structive to the codUng moth were Ascogaster carpocapsse. Vier. and
Itoplectis marginatus Pro v. Hairworm parasites (Mermis sp.) were
abundant in one locaUty and very materially reduced the number
of wintering larvae in the year 1911.

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BULLETIN OF THE

USPEPfflMIOFA^mil

No. 192

Contribution from the Bureau of Entomology, L. O. Howard, Chief.
Aprils, 1915.

(PROFESSIONAL PAPER.)

INSECTS AFFECTING VEGETABLE CROPS IN
PORTO RICO.^

By Thomas H. Jones,
Entomological Assistant, Truck Croj) and Stored Product Insect Investigations.

INTRODUCTION.

The following article can not be considered to include references to
all the many insects which attack vegetable crops in Porto Kico.
Undoubtedly there are many other insect species which are pests on
plants, commonly classed as vegetables, that are grown on the
island. Nevertheless it seems well to present the data available —
data which have been obtained from references already published
and from observations made by the writer since November, 1911,
while a member of the staff of the experiment station of the Porto
Rico Sugar Producers' Association. Especially does it seem timely
to publish this paper because of the effort being made by the United
States Department of Agriculture to obtain information upon the
obnoxious insects liable to introduction into the United States, and
because of the steps that are being taken to prevent them from being
introduced. While it will be noted that many of the species men-
tioned in the following pages already occur in the United States,
several are not known to be present on the mainland.

The determinations of the insects mentioned as having been ob-
served by the wi'iter have been made, with few exceptions, by spe-
ciahsts of the Bureau of Entomology, United States Department of
Agriculture. The names of several of the wild host plants and
of the fungi have been suppUed by Mr. J. R. Johnston, pathologist
of the experiment station of the Porto Rico Sugar Producers'
Association.

It may be said in general that vegetables suffer severe injury in
Porto Rico from insects. The vegetables grown are, for the most
part, the same as those of the markets of the United States, although

iThe observations on which this paper was founded were conducted by the author while a collaborator
in Porto Rico.

Note. — This bulletin enumerates the more common insects attacking vegetable crops in Porto Rico;
of interest to entomologists.
78774°— Bull. 192—15

2 BULLETIN 192, U. S. DEPARTMENT OF AGRICULTURE.

there arc some with which the visitor from the North is not familiar.
Among these may be mentioned a cucurbit, the "chayotc" {SecJiium
edule); the ''lleren" {Calathea allouya), a canna-like plant with edible
tubei-s; and the various members of the genera Xanthosoma
Colocasia, known as "yautias," the latter known also as the
"dasheen" in the southern United States.

The following figures, taken from the Summary of Transactions in
the United States Customs District of Porto Rico, show the value
of the vegetables brought into Porto Rico during the fiscal year
ended June 30, 1912:

Vegetables, dried, canned, and pickled, imported by Porto Rico during fiscal year ended

June 30, 1912.

Commodity.

Domestic merchan-
dise from United
States.

Merchandise im-
ported from for-
eign countries.

Quantity.

Value.

Quantity.

Value.

Bushels.

179, 131

16,446

141,797

1543,577

25,624

164,410

43,083

15, 427

Bushels.

7,315

42,574

51,960

821,020
33, 224

Onions

Potatoes

48,682
12,571
82,703

All others (canned) . . . !

792, 121

198 200

These figures indicate that the cultivation of vegetables could well
be extended by those who have sufficient land at their disposal, and
further study of the various vegetable insects, especially as regards
control measures, would be of great importance in encouraging such
cultivation.

THYSANOPTERA AND HEMIPTERA, OR SUCKING INSECTS.

Thrips tabaci Lind.

This well-known species, the onion thrips, has been found attacking

onions.

Peregrinus maidis Ashm.

Where it occurs in abundance down among the unrolling leaves of
corn, as it often does in Porto Rico, this "leafhopper" injures the
leaves so that they have the appearance of having been scorched by
fire. The presence of the ''honeydew" which they secrete is respon-
sible for the attendance of various ants and fhes.

Jassid^.

''Agallia tenella Ball," presumably Eutettix tenella Baker, was men-
tioned by Mr. Barrett in 1904 ^ as having "injured beans and other
small crops," and in the same year this species was mentioned on

> Barrett, O. W. Report of . . . entomologist and botanist. In Porto Rico Agr. Expt. Sta. Ann. Rpt.
for 1903 [U. S. D. A. Office Expt. Stas. Rpt. 1903], p. 448, 1904.

INSECTS AFFECTING VEGETABLE CROPS IN PORTO RICO. 3

page 84 of Bulletin No. 44 of the Division of Entomology, United
States Department of Agriculture, as having been sent from Porto
Rico by Mr. Barrett, with the statement that it damaged the leaves
of beans, cowpeas, and other plants,

Mr. Barrett also mentioned Empoasca mali LeB., the currant leaf-
hopper, in his 1903 report, above referred to (p. 448), as the "severest
insect enemy of beans and cowpeas."

The writer has found Empoasca mali causmg acute injury to
garden beans, the leaves being badly curled and distorted.

ApHIDIDjB.

Though several species of aphides, or plant Hce, attack vegetables,
the well-known "melon aphis," Aphis gossypii Glov., is apparently
the only one specifically recorded from the island. Mr. Barrett men-
tioned it in 1905/ and in 1906 Mr. Henricksen,^ in discussing the
cultivation of watermelons, stated that it " often infests the imdersides
of the leaves."

Aphis gossypii has been observed in abundance on cucumber, while
other aphides have been found attacking corn, okra, and mustard.
In his report for 1903 (p. 447) Mr. Barrett also stated that "a black
aphid was found on a plant purchased as Alocasia marshallii, but
behoved to be a Xanthosoma" (yautia), and that "the malanga
(Colocasia antiquorum esculentum) is occasionally attacked by an aphid
which is usually parasitized by a whitish fungus and a hymenopter."

In the article in Bulletin No. 44 of the Division of Entomology the
statement is made, on page 84, that, according to Mr. Barrett, an
unknown species of Aphis seriously affects squashes.

Mr. Henricksen has mentioned, in the previously cited bulletin on
vegetable growing (p. 38), an "eggplant aphis, a small light gray, mealy
looking insect," which "appears on the underside of the leaves."

Aphis gossypii and other aphides found on okra are attacked by
an internal parasite, perhaps Aphidius testaceipes Cress. A fungus,
AcrostaJagmus alhus Preuss, attacks various species, and at least five
species of ladybird beetles which feed upon aphides are present in
Porto Rico. These are: Cycloneda sanguinea L., Megilla innotata
Vauls., Scymnus roseicollis Muls., Scymnus loewii Muls., and Hyper-
aspis apicalis Muls. Syrphid flies are also common.

Aleyrodes sp.

Mr. Tower ^ in 1908 stated that "a white fly (Aleyrodes sp.) ap-
peared in great numbers on the peppers and tomatoes" at the experi-
ment station at Mayaguez, P. R. He further mentions that "there

1 Barrett, O. W. Report of . . . entomologist and botanist. In Porto Rico Agr. Expt. Sta. for 1904
[U. S. D. A. Office Expt. Stas. Rpt. 1904], p. 39<), 1905.

2 Henricksen, H. C. Vegetable growing in Porto Rico. Porto Rico Agr. Expt. Sta. Bui. 7, p. 58, 1900.

3 Tower, W. V. Report of the Entomologist and Plant Pathologist. Porto Rico Agr. Expt. Sta. Ann.
Rpt. for 1907, p. 36.

4 BULLETIN 192, U. S. DEPAETMENT OF AGRICULTURE.

appears to be a great number of parasites." Two species of syrphid
flies were reared and a parasitic fungus was observed.

COCCID^.

The following scale insects have been taken on truck crops : Saissetia
Jiemisphserica Targ. (PI. I, fig. 1) and Hemicliionaspis minor Mask, on
eggplant, and Diaspis pentagona Targ. on okra and pepper.

A mealybug has been found at the roots of celery and corn which
has been determined as Pseudococcus sp. near citri Risso. It was
abundant on the crowns of plants growing in rather dry soil, and was
in many cases attended by the "fire ant," Solenopsis geminata Fab.

Spartocera batatas Fab.

Adults (PI. I, fig. 2) and nymphs of Spartocera batatas have been ob-
served in great abundance on sweet potato, their beaks embedded in
the stalks and leaf petioles of the plants.

CoRYTHucA GOssYPn Fab.

The tingitid GorytJiuca gossypii, which breeds on the undersides of
yautia leaves, also occurs in the same situation on the sword bean
(Ganavalia ensiformis) and the castor bean (Ricinus communis).

Phthia picta Drury.

This coreid bug (PI. I, fig. 3) attacks tomato and Solanum nigrum
var. americanum at Rio Piedras, and both adults and nymphs have
been observed by the writer inserting their beaks into the fruit of
both host plants.

CORYTHAICA MONACHA Stal.

Nymphs and adults of Corythaica monacha have been observed to
be so abundant on the undersides of the leaves of eggplant that aU
the foliage withered, turned brown, and fell from the plant. Although
this was an unusual instance, this tingitid is an important enemy of
the eggplant. Plants of a common solanaceous weed, Solanum
torvum, are also often attacked.

ORTHOPTERA.

SCAPTERISCUS DIDACTYLUS Latr.

Probably the most notorious of Porto Rico insects is the "mole
cricket," or "changa" {Scapteriscus didactylus), which injures many
vegetables by cutting off the plants at or just below the surface of
the soil.

In the most complete article on this sj^ecies so far published in
English^ it is stated that "among the small crops the tomato, egg-

1 Barrett, O. W. The changa or mole cricket {Scapteriscus didactylus Latr.) in Porto Rico. Porto Rico
Agr. Exp. Sta. Bui. 2, 19 p., 1 fig., 1902.

Bui. 192, U. S. Dept. of Agriculture.

Plate I.

Insect Enemies of Vegetable Crops in Porto Rico.

^'h^J,;^'''^'^^'??^'^^'"^'''?^' ^'^'i'^'^ (Sais^rlia hinu.'<ijh:rrica) on eggplant. Fig 2 -Suartocfra
batatas: Adult. Greatly enlarged Fig. i.-Pldhia picta: Adult malef Much enlarged

Bui. 192, U. S. Dept. of Agriculture.

Plate II.

Fig. 1.— Pieris monuste: Male Butterfly. Much Enlarged.
(Original.)

Fig. 2.— Nacoleia indicata: Male Moth. Enlarged. (Original.)
LEPIDOPTERA INJURIOUS TO VEGETABLES IN PORTO RICO.

INSECTS AFFECTING VEGETABLE CROPS IN POETO RICO. 5

plant, turnip, and cabbage are most affected," and that the water-
melon, bean, sweet potato, and yautia are seldom or never attacked.

COLEOPTERA.

DiABROTiCA BiviTTATA Fab. and D. innuba Fab.

These two chrysomelid beetles occur in abundance on cucumber,
squash, and melon, especially on the flowers. They quite closely
resemble Diahrotica vittata Fab. in appearance and habits, and those
authors who have referred to vittata as being present on the island
have apparently failed to differentiate between the species.

Diabrotica graminea Bal.

This chrysomelid beetle is very common in Porto Rico. Mr. Van
Drue has reported the adults as feeding on the leaves of sugar cane
to a slight extent.^

The beetles are bluish-green in color and about one-fourth of an
inch in length. So far as the writer has observed, the injury is most
severe on corn and okra, which are, in fact, the only two plants of
this group upon which the writer is certain that they feed, although
they have been observed feeding on the flowers of cowj)eas, the fruit
of Solanum nigrum var. americanum, and the foliage of ''jobo"
(Spondias lutea) and "bledo" (Amaranthus spinosus).

The injury to corn is apparently confined to the silk of the ear and
the blossom spike. On these parts of the plant the beetles congregate
in great numbers, and the results of their feedmg are very apparent,
especially on that portion of the silk which, ordinarily projecting
from the tip of the husk, is completely destroyed. On okra they feed
upon the blossoms and the young leaves.

An assassin bug, Zelus ruhidus Stal., has been taken with a beetle
of this species impaled upon its beak.

Cerotoma denticornis Oliv.

In appearance this beetle resembles the bean leaf-bettle {Cerotoma
trifurcata Forst.), which also occurs in the United States, and, as is
the case with the latter species, there is a marked difference in the
markings on the wing-covers. This difference is shown in figures 4
and 5 of Plate I.

Adults of CerotoTua denticornis have been found feeding upon garden
beans and cowpeas, plants which have been reported on the main-
land as food plants of trifurcata. The habits of the two species are
quite similar. Mr, Barrett, in his 1903 report (p. 448), mentioned
denticornis as being common.

1 Van Dine, D. L. Report of the Entomologist. Sugar Producers' Association of Porto Rico. Ann.
Rpt. 3, p. 34, 1913.

6 BULLETIN 192, U. S. DEPARTMENT OP AGRICULTURE.

Epitrix cucumeris Harr.

Flea-beetles have been taken on eggplant and tomato, which agree
with those taken in company with Epiirix parvula Melsh. on a weed
(Physalis sp.). Those taken on the latter plant were said by Mr, E.
A. Schwarz to be ''properly not different from the U. S. cucumber
flea-beetle, Epitrix cucumeris." ■ On the eggplant the beetles were
causing the familiar ''flea-beetle injury" to the leaves.

Ch^tocnema apricaria Suffr.

This insect injures sweet potato leaves in much the same manner as
does Chsetocnema confinis Lee. in the United States, searing them
with short, continuous, curved Hnes. The beetle is of a dark metal-
lic-green color and has been observed in abundance at certain seasons
on a common weed, related to the sweet potato.

CoPTOCYCLA signifera Herbst.

An adult of this "tortoise beetle" has been taken on the leaves of
sweet potato. In the United States the species is known as an enemy
of this crop.

Cryptorhynchus batata Waterh.

The writer is able to record this enemy of the sweet potato through
the kindness of Mr. R. H. Van Zwaluwenburg, Entomologist of the
Porto Rico Agricultural Experiment Station. Mr. Van Zwaluwenburg
has found it attacking sweet potato tubers at Mayaguez. The species
has been mentioned as an enemy of the sweet potato in the Lesser
Antilles, where it seems to be a more important pest than Cylasformi-
carius.

Cyclas formicarius Oliv.

The "sweet-potato root-borer" is present in Porto Rico, it having
been observed working in the tuberous root of a wild convolvulaceous
plant.

LEPIDOPTERA.

PlERIS MONUSTE L.

The "southern cabbage worm" was mentioned by Mr. Tower in
his 1907 report (pp. 35 and 36) as feeding on cabbage, radish, turnip,
kale, and mustard. The male butterfly is shown in Plate II, figure 1.

The larvae have also been found feeding on horseradish and an un-
cultivated plant, Cleome spinosa, of the family Capparidaceae. This
weed is evidently an important wild food plant of P. monuste in Porto
Rico and is commonly found, especially on the lower lands, near the
rivers. Prof. Ignatius Urban gives it the local Spanish common
name of "jasmin del rio" in his Flora Portoricensis.

INSECTS AFFECTING VEGETABLE CROPS IN POETO RICO. 7

EUDAMUS PROTEUS L.

This liesperid, the so-called "bean leaf -roller," feeds upon garden
beans, cowpeas, and a related weed, Phaseolus latliyroides.

Eggs that probably belonged to this species, found on the leaves of
the last-mentioned plant, were parasitized by Trichogramma minutum
Riley.

Phlegethontius sexta Joh.

Mr. Barrett reported this species, under the name of Protoparce
Carolina, in his 1903 report (p. 448) as occurring commoidy on
tomato and tobacco throughout the island, and made the interesting
note that the larvae were usually killed by a thrust of a knife made
from a "maya" (Bromelia pinguin) leaf. The larva also feeds upon
the common "berengena cimarrona" (Solanum torvum), and Mr.
Tower has stated m his 1907 report (p. 36) that the parasite Teleno-
mus monilicornis held in check the "tobacco hornworm" (probably
this species), eggs of which were found on tomato and pepper.

Phlegethontius convolvuli L.

Adults of this species, which is known elsewhere as a sweet potato
pest, have been collected at Rio Piedras, P. R,

Laph^sgma frugiperda S. & A.

Although corn and onions are the only vegetables so far observed "
to be attacked by the larvae of Laphygma frugiperda, or "grass worm,"
the hst of such plants upon which they feed is undoubtedly much
larger.

In addition to the enemies previously recorded by the writer,^
namely, the three tachinid fhes, Frontina archippivora Will., Gonia
crassicornis Fab., and ArcJiytas piliventris V. d W., the larvae are
attacked by two fungi, Botrytis rileyi Farlon and Empusa sp., and by
an assassin bug, Zelus rubidus Stal. An interesting parasite, CJielonus
insularis Cress. ( ?), the egg of which is laid in the Laphygma egg, the
parasite issuing from and killing the host larva when the latter is
about one-half inch in length, has also been observed.

A carabid beetle, Calosoma alternans Fab., is predaceous upon the
larvae, and another carabid, Cymindis marginalis Dej., probably has
the same habit.

Heliothis obsoleta Fab.

The corn ear-worm attacks corn in Porto Rico and is to be con-
sidered an important pest to this crop. Mr. Barrett mentioned it in
his 1903 report (pp. 443 and 444).

1 Some notes on Laphygma frugiperda S. «fe A. in Porto Rico. Jour. Econ. Ent., v. 6, no. 2, p. 235,
April, 1913.

8 BULLETIN 192, U. S. DEPARTMENT OF AGRICULTUKE.

Other Noctuid/e.

Three other noctuid moths, that have been reared from larvae,
belong to the species known to injure truck crops iji the United States.
Xylomyges eridania Cram., the larvae of which occurred oji Amaranthus
sp., has been mentioned by Messrs. Chittenden and Russell under the
name of Prodenia eridania Cram.^ as attacking Irish potatoes, egg-
plant, pepper, okra, and sweet potato in Florida, and they give, on
another's authority, beets, cabbage, and carrots as food plants.

Prodenia ornithogalli Guen., the cotton cutworm, reared from larvae
found feeding on a weed of the family Convolvulacese, is stated by
Dr. Chittenden to be an enemy of several vegetable crops.^

The larvae of Feltia annexa Treits., which species has been reared
from larvae found in an area where "grass worms" (LapJiygma frugi-
perda S. & A. and Remigia repanda Fab.) were abundant, is known
as a cutworm on the mainland.

DiAPHANIA HYALINATA L.

Cucumbers and squashes are frequently severely attacked by the
larvae of this species, the melon caterpillar. Mr. Barrett mentioned
the species in his 1903 report (p. 448).

Pachyzancla bipunctalis Fab.

The "southern beet webworm" has been found feeding on garden
beans, sword bean (Canavalia ensiformis), and weeds belonging to
the genus Amaranthus. Upon the garden bean and Amaranthus it
was feeding on the leaves, which it webs together, forming for itself
a shelter, as is commonly done by pyralid larvae. The leaf or leaves
of which the shelter is formed are skeletonized and the pupae are
sometimes found in the shelters, but more often in earthen cells just
below the soil surface. The larvae found on sword bean were feeding
within the green pods.

Exorista pyste Walk., a tachinid parasite of the larvae, has been
observed.

In connection with Pachyzancla hipunctalis it may be mentioned
that another pyraHd, Hymenia (ZincJcenia) fascialis Cramer, occurs
in Porto Rico. It has been observed under conditions that would
indicate that the larvae feed upon Amaranthus spp. Mr. H. O. Marsh
has studied this species in the Hawaiian Islands, and in Bulletin 109,
Part I, of the Bureau of Entomology, states that various beets and
several species of Amaranthus are among the plants which suffer
from its attack there.

1 Chittenden, F. H., and Russell, H. M. The semitropical army worm. (Prodenia eridania Cram.).
U. S. D. A., Bur. Ent., Bui. 66, pt. 5, p. 53-70, figs. 8-11, Jan. 28, 1909.

2 Chittenden, F. H. Some insects injurious to the violet, rose, and other ornamental plants. U. S.
D. A., Div. Ent., new ser. Bui. 27, rev., p. 64, 68, 69, 70, 1901.

Bui. 192, U. S. Dept. of Agriculture.

Plate III.

Fig. 1.— Work of the Larva of Pachyzancla periusalis on
solanum torvum. (original.)

Fig. 2.— Pilocrocis tripunctata: Moth. Enlarged. (Original.)
LEPIDOPTERA INJURIOUS TO VEGETABLES IN PORTO RICO.

Bui. 192, U. S. Dept. of Agrlculturp.

Plate IV.

Mustard Leaf Showing Injury by the Diamond-Back
Moth (Plutella maculipennis). (Original.)

INSECTS AFFECTING VEGETABLE CROPS IN POKTO RICO. 9

Pachyzancla periusalis Walk.

Larvas of this pyralid moth feed upon the leaves of eggplant and
Solanum torvum. The young larvae live at first as miners in the
leaves, but later web the leaves together. (See PL III, fig. 1.) The
shelter is usually formed near the edge of the leaf, a portion of which
is folded in toward the midvein and held in place by silken threads.
Sometimes, however, parts of two or more leaves form the shelter.
Tlie larvae feed from within these areas and are often common on
both plants mentioned as hosts.

The moth has a wing expanse of three-fourths to seven-eighths of
an inch and is gray in color. The wings are glistening and marked
above with three darker, wavy, transverse Unes, the two inner ones
extending across both wings, while the outer one extends from the
costal margin to a point near the middle of the front wing.

Nacoleia indicata Fab.

The larva feeds upon the leaves of garden bean, webbing together
parts of the same leaf or separate leaves. It also occurs on cowpea.

The adult, Plate II, figure 2, is golden yellow, the wings marked
with black along the outer margin, and above with three black
wavy lines extending across them, much as do the dark lines on the
wings of Pachyzancla periusalis.

PiLOCROCIS TRIPUNCTATA Fab.

Sweet-potato leaves have been found webbed together and injured
by the larvae.

The moth, shown in .Plate III, figure 2, is light yellow, the wings
being marked with black and brown, and having an expanse of about
an inch.

Plutella maculipennis Curtis.

Larvae of the "diamond-back moth" are at times very abundant
on and destructive to the leaves of cabbage. Mr. Barrett mentioned
the species in his 1903 report (p. 448) and Mr. Tower, in his 1907
report (p. 35), Usted cabbage, kale, mustard, and turnips as food
plants, briefly summarized its hfe history, made note of a parasite,
and mentioned remedies to be apphed. A mustard leaf which has
been severely injured by the larvae is show;i in Plate TV.

HYMENOPTERA.

SOLENOPSIS GEMINATA Fab.

The "file ant," or "hormiga brava," has been found injuring okra
plants by cutting away parts of the flowers and portions of the
younger growth.

10

BULLETIN 192, U. S. DEPAETMENT OF AGKICULTUKE.

It is often stated in Porto Rico that ants destroy certain vegetable
seeds after they have been planted in the soil. The writer has been
told on good authority that ants, which from the description were
apparently the "hormiga loca" or "crazy ant," Prenolepis longicornis
Latr., were seen to dig small holes along the rows in a propagating
box in which lettuce had been planted, remove the seeds, and carry
them away.

DIPTERA.

Agromyza parvicornis Loew.

The ''corn-leaf blotch miner," which has been recently made the
subject of a paper ^ by Mr. W.'J. PhiUips, is present in Porto Rico,
adults having been reared from larvae found working in leaves of
corn at Rio Piedras.

SUMMARY.

The following summary, arranged alphabetically according to
host plants, indicates the insects known to attack the various vege-
table crops grown in Porto Rico. The "changa" (Scaj^eriscus
didadylus Latr.) is credited in this list as injuring only those plants
which, according to Mr. Barrett, are most affected, though in reality
the hst of plants attacked by it is not so limited.

Beans:

Eutellix tenella Baker. (?)
Eudamus pToteus L.
Empoasca malt Le B.
Cerotoma denticornis Oliv.
Nacoleia indicata Fab.

Beets:

Pachyzancla bipunctalis Fab.

Cabbage:

Scapteriscus didadylus Latr,
Plutella viaculipennis Curtis.
Pieris monuste L.

Celery:

Pseudococcus sp. near citri Risso.

Com:

Peregrinus maidis Ashm.
Pseudococcus sp. near, citri Bisso.
Diabrotica graminea Baly.
Laphygma frugiperda S. & A.
Heliothis obsoleta Fab.
Agroviyza parvicornis Loew.

Cucumber:

Aphis gossypii Glov.

Diabrotica bivittata Fab.
1 Phillips, W. J. Corn-leaf blotch miner [Agromyza
V. 2, no. 1, p. 15-31, 6 figs., 5. pi., Apr. 15, 1914.

Cucumber — Continued .

Diabrotica innuba Fab.

Diaphania hyalinata L.
Eggplant:

Saissetia hemisphxnca Targ.

Heviichionaspis minor Mask.

Corythaica monacha Stal.

Scapteriscus didactylus Latr.

Epitrix cucumeris Harris (?).

Pachyzancla periusalis Walk.
Horse-radish :

Pieris monuste L.
Kale:

Pieris monuste L.

Plutella maculipennis Curtis.
Melon:

Aphis gossypii Glov.

Diabrotica bivittata Fab.

Diabrotica innuba Fab.
Mustard:

Pieris monuste L.

Plutella maculipennis Curtis.
Okra:

Diaspis pentagona Targ.

Diabrotica graminea Baly.

Solenopsis geminata Fab.
parvicornis Loew]. In U. S. Jour. Agr. Research,

INSECTS AFFECTING VEGETABLE CROPS IN PORTO RICO.

11

Onion :

Thrips tabad Lind.

Laphygma frugiperda S. & A.
Pepper:

Aleyrodes sp.

Diaspis pentagona Targ.
Radish :

Pieris monuste L.
Squash :

Diabrotica bivittata Fab.

Diabrotica innuba Fab.

Diaphania hyalinata L.
Sweet potato:

Spartocera batatas Fab.

Chsetocnema apricaria Suffr.

Pilocrocis tripunctata Fab.

Cryptorhynchus batatas Waterh.

Sweet potato — Continued.

Other insects, known as sweet-
potato pests in the United States,
are also present, namely —
Coptocycla signifera Herbst.
Cylas formicarius Oliv.
Phlegethontius convolvuli L.
Tomato:

Scapteriscus didactylus Latr.
Phlegethontius sexta Joh .
Aleyrodes sp.
Turnip:

Scapteriscus didactylus Latr.
Pieris monuste L.
Plutella maculipennis Curtis.
Yautia:

Corythuca gossypii Fab.

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WASHINGTON : GOVERNMENT PRINTING OFFICE : 1915

DI7,. INSECTS-
BULLETIN OF THE

No. 197

Contribution from the Bureau of Elntomology, L. O. Howard, Chief.
March 31, 1915.

HOMEMADE LIME-SULPHUR CONCENTRATE.

By E. W. Scott,
Entomological Assistant, Deciduous-Fruit Insect Investigations.

During the past few years mucli attention has been given by
investigators to the home preparation of lime-sulphur concentrate
and also to an inquiry into the chemical reactions involved, as affect-
ing the conditions under which the work should be done. These
investigations have had for their purpose the encouragement of
orchardists in the preparation of concentrates for their own use, or
for the use of the neighborhood. The success of these efforts is shown
by the fact that many fruit growers now prepare their own lime-
sulphur concentrates, thus effecting a material saving over the cost
of the commercial article.

Orchardists, as a rule, are not able consistently to obtain a product
of uniform density, even though the same formula be employed and
the work be accomplished as nearly as possible in an identical manner
for the different batches. This defect, however, is really of little
importance, since it is easy to test the density of the concentrate and
make dilutions in conformity with the purpose for which it is to be
used.

During the past few years the Bureau of Entomology has given
attention to the making of lime-sulphur concentrates in connection
with work in deciduous-fruit insect investigations. No particular
chemical study was planned in connection with these cooking tests,
as it was merely desired to know the degree of density and percentage
of the ''sludge" which would result by the employment of different
formulas. The cooking tests for the most part were made at lime-
sulphur plants operated by orchardists, or by individuals who sup-
plied the concentrate to orchardists in the immediate territory.

EXPERIMENTS AT BERRYVILLE, VA.

Six experiments were conducted at a small plant at Berryville,
Va. This plant consisted of a 12-horsepower boiler and two 150-
gallon cooking vessels. The cooking was done by steam which was

Note.— Describes experiments in making lime-sulphur concentrates and gives the most satisfactory
formulas. Of interest to all practicing spraying in insecticida work.
81647 •—Bull. 197—16

2

BULLETIN 197^ U. S. DEPARTMENT OF AGRICULTURE.

ejected through perforated coils in the bottom of the tanks. There
was no mechanical agitator, the mixture being agitated by hand by
the use of a long wooden paddle. The mixture was allowed to cook
50 minutes, when, after taking samples for testing purposes, the
remainder was drained into a storage tank. The results of these
tests are given in Table I. '

Table I. — Results of cooking different lots of lime and sulphur in preparation of lime-
sulphur wash, Berryville, Va., 1912.

Experi-
ment No.

Formula.

Percentage
in volume
of sludge.

Degrees
Baum6.

Lime.

Sulphur.

Water.

1

2
3

4
5
6

Pounds.
50
50
50
50
45
55

Pounds.
100
100
100
100
100
100

Gallons.
50
50
50
50
50
50

39.0
50.0
35.0
41.5
41.0
44.0

28.5
30.0
29.5
30.5
29.0
28.0

The 50-100-50 fonnula was used in the first four of these experi-
ments. The Baume test of the cooked wash varied from 28.5° to
30.5°, and the percentage in volume of sludge, after standing 24 hours,
varied from 35 to 50. The preparation of the wash in experiments 1
and 3 was as nearly the same as was possible, the lime being added
jBrst and the sulphur immediately afterwards. In experiment 2 the
sulphur was added first.

In experiment 4 the mixture was not stirred after the steam was
turned on, the steam being depended upon for agitation. Otherwise
the treatment was the same as in experiment 1.

In experiments 5 and 6 the quantity of lime was decreased and in-
creased 5 pounds, respectively, from the amount previously used.
This was done to determine, if possible, whether more or less of this
particular brand of lime should be used. In every other respect the
treatment was the same as in experiment 1. The only points con-
sidered in this experiment were the Baume test and the percentage in
volume of sludge.

EXPERIMENTS AT WINCHESTER, VA.

A lime-sulphur cooking plant located at Winchester, Va., also was
visited. This plant, which has a capacity of 500 gallons per day,
consists of a 150-gallon rectangular sheet-iron tank embedded in a
brick furnace in which wood is burned to furnish the heat. This
plant supplies a number of the surrounding fruit growers with lime-
sulphur solution. As soon as the cooking has been completed, the
solution is piped directly through a 20-mesh strainer into 50-gallon
barrels and is delivered to the growers without being filtered. The
strainer, of course, takes out only the coarser particles; therefore it is
necessary for the grower thoroughly to shake the barrel each time

HOMEMADE LIME-SULPHUR CONCENTRATE. 3

any of the solution is taken out in order to get an even distribution
of the sludge. The following data were obtained, which show the
variation in density of the different batches. Four batches in which
the 50-100-50 formula was used tested 25°, 26°, 28°, and 29° Baume,
respectively. Seven batches in which the 55-1 1 0-50 formula was used
tested 28°, 29°, 29°, 30°, 30°, 30°, and 31° Baum6, respectively. It
will be noted that there was considerable variation in degrees Baume
for the different batches, although each was cooked as nearly as possi-
ble in the same way.

Similar variations in density were observed at a steam-cooking
plant at Chewsville, Md.

EXPERIMENTS AT HAGERSTOWN, MD.

A new lime-sulphur cooking plant at Hagerstown, Md., was visited.
The cooking vessels, two in number, consisted of the hulls of two large
boilers standing on end. Each held about 1,500 gallons. The cook-
ing is done by steam. A few experiments were conducted at this
plant to determine, if possible, what formula should be used under
these conditions of manufacture to obtain a higlily concentrated
solution. The results of these trials are given in Table II.

Table IT. — Results of cooking different lots of lime and sulphur in preparation of lime-
sulphur wash, Hagerstown, Md., 1912.

Experi-

Formula.

Percentage
in volume
of sludge
(estimate).

Degrees

ment No.

Lime.

Sulphur.

Water.

Baum^.

1
2
3

4

Pounds.
800
800
750

200
1,000

Pounds.
1,600
1,600
1,500

400
2,000

Gallons.

800
800

285 gallons sludge, 715 gallons water

Added to above 1,000 gallons of 23°
Baum^ material

35.0
35.0
40.0

45.0
45.0

25.5
26.0
23.0

27.0

5

280 gallons sludge, 620 gallons water

32.6

In Experiments 1 and 2 800 gallons of solution were cooked at a
time. The 50-100-50 formula was used in each of the two experi-
ments with a result of 25.5° and 26° Baume test solution respec-
tively. In each case there was about 35 per cent in volume of sludge.
The solution in Experiment 1 was allowed to remain in the vessel
24 hours, then the clear solution was drawn off and 285 gallons of
sludge remained in the tank. In order to see what effect this sludge
would have on the solution by cooking it over with the next batch
(Experiment 3), 715 gallons of water were added to it, making 1,000
gallons in all; 750 pounds of lime and 1,500 pounds of sulphur were
added to this and the mixture was cooked for one hour. After
allowing the solution to settle 24 hours the clear liquid tested 23°
Baume and there was 40 per cent in volume of sludge. An attempt
was made to raise the test of this solution (Experiment 4) by adding

•4 BULLETIN" 197, U. S. DEPAETMENT OF AGETCULTURE.

to it 200 pounds of lime and 400 pounds of sulphur. After coc^king'
this for an hour and allowiag it to settle there was 45 per cent in
volume of sludge and the clear solution tested 27° Baume. In an
attempt to make a high-test solution by using a reduced quantity
of water mixed with sludge Experiment 5 was conducted. To the~
280 gallons of sludge remaining in the cooking ressel from Experiment
2 there were added 620 gallons of water, making a total of 900 gallons..
To this was added 1,000 pounds of lime and 2,000 pounds of sulphur;.
This was cooked for one hour, and after allowing it to settle for 24i
hours there was 45 per cent in volume of sludge, and the clear solu--
tion tested 32.5° Baume. It will be seen that a high-test solution-
was obtained by reducing the quantity of water, but the percentage
of sludge was also considerably increased.

EXPERIMENTS AT VIENNA, VA.

A few lime-sulphur cooking experiments were ©onducted at
Vienna, Va., in the spring of 1911. A large iron pot placed over- a
wood fire was used as a cooking vessel. In four of these experiments
the 50-100-50 formula was used. The time of cooking was from: 45-
minutes to one hour. The results, whick show variation in Baum^'
test and a high percentage in volume of sludge, are gjven in Table:
III.

Table III.-

\

-Results of cooking different lots of linie and s^ilphur in yn-parationLofTlim^.^
sulphur wash, Vienna, Va., 1911.

Experi-
ment No.

Formula.

Percentage
in volume
ofeludge.

Degrees
Baume.

Lime.

Sulphur.

Water.

8
9
10
11

Pounds.

8

40

40

40

Pounds.
16
80
SO
80

SuUons.

8

40

40

40

40.9'
33.0.
40jO
5(J..O

30; 6

28.8.
28.7
27,0,

1

EXPERIMENTS AT BENTON HARBOR, MKH.

Some experiments were cond\icted at Benton Harbor, Mich., in th^
fall of 1912 for the purpose of making high-test solutions. The cook-
ing plant consists of a 12-horsepower boiler from which steam is;
conducted into two 50-gaUon barrels. There are no coils im the bot-
tom of the barrels, the steam simply being emitted througb, the open
' end of a straight pipe extending to within a few inches of the bottom
of the barrel.

Small batches amounting to 25 gallons of the finisli^d product were

cooked at a time. About 20 gallons of water were put into the barrel^

then the steam was turned on and the water brought to boiling. Tlie

. lime was then put in and after it had begun Ico slake the sulphi^r- ^a^

HOMEMADE LIME-SULPHUB CONCENTKATE. 5

added. The mixture was stirred thoroughly throughout the time of
cooking, which lasted 1 hour. It was allowed to settle about 12 hours,
and then the clear solution was siphoned off. The sludge was put into
a cider press and the clear solution pressed out, using 10-ounce canvas
cloth for filter. A good grade of stone lime was used in experiments
1 to 5. Hydrated lime was tried in experiments 6 and 7. Commer-
cial ground sulphur was used in all the experiments. The results are
given in Table IV.

Table IV.

-Results of cooking different lots of lime and sulphur in preparation of linu-
sulphur wash, Benton Harbor, Mich., 1912.

Formula.

Experi-
ment No.

Degrees
Baumd.

Lime.

Sulphur.

Water.

Sediment.

Pounds.

Pounds.

Gallons.

Pounds.

1

25

50

25

32

27.0

2

25

50

25

36

27.0

3

40

SO

25

80

34.0

4

40

SO

25

90

35.5

5

•10

SO

25

85

32.5

6

100

80

25

110

30.0

7

100

SO

25

100

31.5

1 Hydrated.

In Experiments 1 and 2 the 50-100-50 formula was used, with a
result of 27° Baume test solution in each case and 32 pounds of
skidge in Experiment 1 and 36 pounds in Experiment 2. In Experi-
ments 3, 4, and 5 the same proportion of lime and sulphur as above
stated was used, but the amount of water was reduced, the formula
being 40 pounds of lime and 80 pounds of sulphur and water to make
25 gallons of concentrate. The Baume tests of these three batches
varied from 32.5° to 35.5°, and the amount of sludge varied from
80 to 90 pounds. The sludge, after it had been run through the
cider press, was in the form of a thick paste, so the number of pounds
given does not nearly represent the number of pounds of dry sediment.

The formula used in the last two experiments was 60 pounds of
hydrated lime and 80 pounds of sulphur with water to make 25 gal-
lons of concentrate. Where the hydrated lime was used the solution
did not test so high and there was considerably more sludge.

DIRECTIONS FOR PREPARATION OF LIME-SULPHUR CONCENTRATE.

The 50-100-50 formula has been generally recommended for the
preparation of home-boiled concentrated lime-sulphur solution.
The method of preparation is to boil together for 50 minutes to 1
hour 50 pounds of lime, 100 pounds of sulphur, and water to make
50 gallons of the concentrated solution. A good grade of fresh
stone lime containing not less than 90 per cent of calcium oxid is
necessary for the best results. Hydrated lime is sometimes used.

6 BULLETIN 197, U. S. DEPARTMENT OP AGEICULTUEE.

but it is necessary to use a good grade and at least 20 per cent more of
this form of lime, as it contains a high percentage of moisture.

Place enough water in the cooking vessel to finish with 50 gallons
of the solution. Bring the water to the boiling point, start the
agitator, if the plant is equipped with one, then put in the lime
and immediately add the sulphur. The mixture should be stirred
vigorously either mechanically or by hand until the lime is slaked.
Agitation should be continued throughout the time of cooking, which
should not exceed one hour. If the solution is to be barreled without
filtering, it should be drawn off immediately and allowed to run
through a 30-mesh strainer into the barrels. The agitation should
continue until all the solution is drawn off, so that there will be an
equal distribution of the sludge in the different barrels. _

PREPARATION OF HIGHLY CONCENTRATED LIME-SULPHUR SOLUTION.

From the experiments above reported, it is evident that a higlily
concentrated lime-sulphur solution may be made by using the lime
and sulphur at the ratio of 1 to 2 as is usually recommended, but
with reduced quantities of water. The formula used in the com-
mercial hme-sulphur manufacturing plants visited and also in the
foregoing experiments is as follows:

Fresh stone-lime pounds. . 80

Commercial ground sulphur do 160

Water to make the finished product gallons. . 50

While there is about 50 per cent in volume of sludge after allowing
this solution to settle for 24 hours, there is only about 5 to 10 per cent
in volume of insoluble materials. These consist of sulphites, free
hme, free sulphur, magnesium compounds, etc., varying with the
kind of lime used and other conditions. Solutions prepared by this
formula should test on an average 33° to 34° Baume.

RELATIVE COST.

Commercial ground sulphur can be bought in car lots for about
$1.50 per hundred pounds, and lime at about 60 cents per barrel. At
these prices the higlily concentrated solution can be made at the
following cost per barrel:

80 pounds lime at 60 cents per barrel |0. 20

160 pounds sulphur at $1 .50 per hundredweight 2. 40

Labor and fuel, estimated 70

Total cost per barrel of 50 gallons 3. 30

This does not include interest and wear on outfit, and cost of
containers for storing. At the foregoing prices of ingredients the
high-test concentrate would cost about 98 cents more per barrel than
the lower-test concentrate made by the 50-100-50 formula.

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1915

P^J^'i/vircijs

BULLETIN OF THE

u.

No. 200

Contribution from the Bureau of Entomology, L. O. Howard, Chief
May 4, 1915.

A MAGGOT TRAP IN PRACTICAL USE; AN
EXPERIMENT IN HOUSE-FLY CONTROL.

By iw. ix. Hutchison, Scientific Assistant.
INTRODUCTION.

During the season of 1913 experiments were carried out independ-
ently by Levy and Tuck at Ricliniond, Va., by C. G. Hewitt at
Ottawa, Canada, and by the wTiter at Arhngton, Va., and New
Orleans, La., all of which agreed in demonstrating a most pro-
nounced migratory habit in house-fly larvae just before pupa-
tion. It was found very easy to trap them at this particular stage
of their development, and experiments with small maggot traps
showed that as high as 98 or 99 per cent of the larvae could be caught.
At the suggestion of Mi'. W. D. Hunter the writer has made an
attempt during the past season to apply the principles of the maggot
trap to practical use and to test its efficiency when used to destroy
the maggots in large masses of manure. In this article are reported
the results obtained from experimental work along this line, con-
ducted at the Maryland Agricultural College at College Park, Md.
Dr. H. J. Patterson, president of the coUege and director of the
experiment station, has been most generous in his cooperation in
this work, and tlu'ough him the materials and labor for the con-
struction of the trap were supplied. The writer wishes also to
acknowledge the helpful suggestions of Profs. T. B. vSymons and E. N.
Cory, of the college.

LOCAL CONDITIONS WITH REGARD TO FLY PREVALENCE AND BREED-
ING PLACES.

Th- 4uilege was selected as a suitable place for conducting the ex-
permient, partly because the conditions with regard to breeding
places for flies seemed such that it would be easy to determine,
whether or not the maggot trap was effective. The college is some-

NuTE.— This bulletin describes the operations of a maggot trap based on the migratory habit of
house-fly maggots just before pupation. It will be of interest to all farmers and to those industries in
which the accumulation of refuse may encourage the propagation of the house fly.
82252°— Bull. 200—15

2 BULLETIN NO. 200^ U. S. DEPARTMENT OF AGRICULTURE.

what isolated by its position on a liUl and separated a considerable
distance from any near-by stables. On the accompanying map
(fig. 1), which has been adapted from a map of the Geological Survey,
is shown the topography of the surrounding section. The location of
only two of the coUege buildings is given, viz, the college kitchen
(K) and the stable (S) . The college kitchen, by reason of odors from
cooking and the presence of large quantities of garbage kept in iron
pails just outside the door, attracted extremely large numbers of
flies. One could not approach these garbage pails without stirring
up a noisy swarm which had congregated there. However, no fhes
were breeding out from this garbage, for the reason that it was

Fig. 1. — Map of vicinity of tho Maryland Agricultural College showing the location of the college kitchen
(£■), the stable (S), and the proximity of other breeding places of flies (,A,B, C, D, etc.) (Original.)

entirely removed every two or three days and taken to a near-by
farm, where it was fed to hogs.

The breeding ground nearest to the kitchen was the pile of manure
Eeaped just outside the college stable. This is nearly 200 yards
northwest of the kitchen. It is probable that a large majority of
the flies at the kitchen came from this source. Upon examination at
various times during June and July the fresher portions of this heap
were always found heavily infested with larvae. Puparia were also
found in great abundance in the loose soil and in the manure at the
periphery of the pile. Three horses were kept in this stable, and
two of them were standmg in the stalls durmg the greater part of
each day. Flies were also very numerous in and about the stable,
and during the day the horses were continuously tormented by them.

A MAGGOT TRAP IX PRACTICAL USE. 3

With the exception of the college stable, there were no breeding
places for flies within 400 yards of the kitchen. The stable, indicated
by the letter C on the map, is approximately 400 yards from the
kitchen and about 200 yards from the college stable. Other stables
are located some 400 to 500 yards west of the college stable, the dis-
tance from the kitchen being about 100 yards greater.

Another extensive breeding place was found in the large collec-
tions of manure at the barns of the experiment station, located
about 700 yards northeast of the college. This is indicated on the
map by the letter A.

PLAN OF EXPERIMENT.

With these conditions prevailing, it was planned to construct a
maggot trap large enough to take care of the entire manure produc-
tion at the college barn, with the idea that if the trap proved effective
there should appear a marked decrease in the prevalence of flies, not
only at the barn but at the college kitchen. To determine whether
or not the trap was effective the following three lines of observation
were undertaken: (1) By collection and careful estimate of the
larvae caught by the trap and subsequent search for puparia in the
manure, to get some idea of the percentage destroyed; (2) by making
numerous fly counts during the season to find out whether the
prevalence of flies at the kitchen and stable was decreased; and (3)
to determine whether any of the flies at the college came from near-
by breeding grounds (A, B, C, etc.) other than the manure heap at
the coUege stable.

THE MAGGOT TRAP.

The maggot trap used in this experiment was designed and con-
structed as follows. First, a concrete floor was prepared 22 feet long
and 12 feet wide. Around this floor was a rim or wall of concrete 4
inches high and 4 inches thick. An outlet pipe 4 inches in diameter
was fitted in one corner toward which the floor sloped a little so that
water would run out easily. Water was retained in the concrete
floor by stopping the pipe outlet with a plug of soft wood. The pipe
outlet led to a small cistern 5 feet square and 4 feet deep, the waUs
and floor of which were made of concrete. Standing on the floor of
the concrete basin was constructed a wooden platform 20 feet long
and 10 feet wide, supported on legs 1 foot high. The framework
of the platform was made of 2 by 4-inch studding. There were 6 of
these pieces running lengthwise 2 feet apart, and one fastened across
each end. Each of the long pieces was supported on four legs set at
intervals of nearly 7 feet. Across the top of the framework were
nailed strips 10 feet long by 1|^ inches thick and 1 inch wide. These
strips were nailed 1 inch apart. Plate I shows most of the details

4 BULLETIN NO. 200, U. S. DEPARTMENT OF AGEICULTURE.

of construction. Plate II gives another view, including also the
outlet pipe (in this case consisting of 4-inch terra cotta) and the pump
in place over the cistern. On account of various obstructions it was
necessary to place the cistern some distance away from the trap,
although, as wiU be pointed out later, it is desirable to have the cistern
close to the trap and the pump so arranged as to return the contents
of the cistern to the manure heap on the platform.

THE METHOD ADOPTED IN USING THE MAGGOT TRAP.

The maggot trap was put into operation on July 25. On this date
the manure pile which had accumulated in front of the barn during
June and July was hauled away and spread on the fields, so that,
beyond the hatching out of the pupae and larvae already present, it
ceased to exist as a breeding ground for flies. On and after July 25
each day's production of manure was heaped on the platform.
Beginning at the end farthest from the barn door, the manure was
piled up to a height of from 3^ to 4 feet. The heap was maintained
at about this height, and with the daily additions it kept increasing
in length. Plates I and II show the appearance of the heap after a
little more than four weeks' accumulation. The platform was found
large enough to hold a little more than two months' production of
manure from three horses and could easily have been made to hold
the total production for three months by making the pile higher.
Each day, after the addition of manure and litter from the stable,
the manure on the platform was sprinkled with enough water to
moisten it thoroughly without causing any leaching. Water was
run into the concrete basin below the platform, so that the floor
beneath the manure was covered to a depth of J inch in the shallowest
part. Larvae migrating from the manure dropped into the water
below and were drowned.

At least once a week, and sometimes oftener, the water was drawn
off from the basin into the cistern and the floor was washed clean by a
strong stream of water from a hose. The larvae which had fallen into
the water, together with the debris which had sifted through the
platform or fallen from the sides, were collected at the cistern end
of the outlet pipe in a strainer. The matter thus retained in the
strainer was then spread out on a smooth concrete surface near by,
and the number of larvae present was carefully estimated. The
outlet was then plugged, and the basin again partly filled with water
by pumping back what had run into the cistern.

THE PERCENTAGE OF MAGGOTS DESTROYED.

Without going into details of the weekly or biweekly counts, it
will be enough to state that during the period from July 25 to October
1 a total of about 112,000 dead larvae were collected in this way.

A MAGGOT TRAP IN PRACTICAL USE, 5

But this number does not represent all that dropped out of the manure
mto the water below. A flock of young turkeys roamed at large
during the summer over the college grounds and adjoining fields.
Having once found the maggot trap they made frequent visits and
were seen to devour the larvae with great avidity, sometimes com-
pletely clearing the floor except where the water was more than 2 or 3
inches deep or when it was so badly discolored as to conceal the larvae.
Sparrows also were seen frequently on this floor, but one could never
get close enough to see whether they actually devoured any larvae or
not. It is more than likely that they did. The actual number of
larvae which were destroyed by the maggot trap was undoubtedly
much greater than 112,000.

After October 1 the writer and an assistant examined all the manure
on this platform in search of puparia. The manure was thrown off,
a few bushels at a time, onto a smooth concrete surface near by and
very carefully examined, all straw being shaken out and all sohd
parts being finely broken up. In a very literal sense this wa'S like
looking for a needle in a haystack. A few scattered puparia were
seen in various parts of the heap, but in only two spots were they to
be found in the characteristic clusters or "nests" which can be found
so readily at the edges of manure piles on the ground. These two nests
were found at the end of the platform where the most recent additions
had been made. The manure at this end had not been sprinkled
with water after the day it was put on. Failure to keep this moist
as long as larvae were present is, in the writer's opinion, the explana-
tion of the pupation in this part. One nest contained about 400,
and the second about 700 puparia. Allowing for some that may have
escaped notice, the number of puparia may be given in round numbers
as 1,500. No larvae whatever were found in any part of this heap, the
oldest part of wliich had been on the platform for two months, and
even the freshest portion of which had been standing for at least 10
days before it was examined. If, then, 1,500 represents the total
number wliich pupated in the manure and 112,000 the number
which was destroyed by drowning, it shows a percentage destruction
of about 98.5 per cent of the possible total. This is illustrated in
figure 2, above. Taking into account the larva3 devoured by
turkeys, etc., it is probable that the effectiveness of the trap could be
rated as above 99 per cent.

In a former bulletin the claim was made that manure will be prac-
tically free from maggots after standing 10 or 12 days. Special
attention was given to this point during the course of the experiment,
and all observations tended to support the claim. Moreover, there
was no evidence that larvae ever migrated from the fresher portions
of the manure to the older parts to pupate. That old manure
does not serve as a breeding place for fhes is a point that deserves

6 BULLETIN NO. 200, U. S. DEPAETMENT OF AGEICULTUEE.

some emphasis entirely aside from its bearing on the practical use
of the maggot trap. The explanation is probably to be found in
the changes wliich take place in the manure heap during storage. As
the pile stands it settles considerably, with a consequent decrease of
air spaces, and, especially if watered, air does not penetrate far below
the surface. Deherain and Dupont (1900) have shown that in manure
well heaped so that air can not penetrate readily, the confined gases
consist largely of carbon dioxid and methane, and that oxygen is
not found except near the surface. It may well be that the lack of
oxygen and the abundance of carbon dioxid render old manure
unfavorable for the breeding of flies. It may also be that the com-
position of the gases in the manure is one of the factors which in-
fluence migration and the choice of a place for pupation.

%/soo

/ AV£PA6£ or /O COC/A/rS ^T K/rc/-/£/V BeF-OfPS AUGC/Sr /o

Ai/£RACe OF /O COUA/TS AT f</TC/-t£fJ ArT£R AUGUST /O

Ai/£RAG£ OrS COUNTS AT STABL£ B£FO/r'E /AUGUST /O-

■£RAa£ OrS COUA/TS AT £TAiBL£ /iPr£ff AUGC/ST /O.

Fig. 2. — Graphical representation of the ATork of the maggot trap and its effect on the prevalence
of flies. (Original.)

EFFECT ON THE FLY PREVALENCE AT THE STABLE AND KITCHEN.

Turning now to the second hue of observation, it will be of interest
to determine to what extent the maggot trap influenced the number
of flies at the stable and kitchen. An answer to this is to be found in
the series of fly counts made during the season, both before and after
the trap was started. In taking these counts " ta,ngief oot " sticky
fly paper was used. The papers were exposed for 24-hour intervals
and counted immediately at the end of that period. Figure 3 is a
graphic representation of these series of counts at the stable and
kitchen. In each case the number given is the total caught on two
papers exposed at the same time. At the kitchen the two papers
were always exposed in the same way on top of the garbage pails,
and at the stable one paper was put on the floor just outside the

A MAGGOT TRAP IN PEACTICAL USE. 7

door and the second just inside the door, which faces the east. On
several occasions papers were exposed, but the counts are not given
in the diagram for the reason that a shower of rain or a strong wind
spoiled some of the papers. The numbers which are plotted are those
obtained on clear, warm days, on which the climatological conditions
were nearly the same except for the direction of the wind. This will
account for the irregular time intervals between the successive counts.
It is recognized that this method is not all that could be desired as
an accurate index of fly prevalence. The use of a small number of fly
papers in this way is nothing more than a method of sampling, but
since the papers were exposed always in the same places and under
nearly the same climatological conditions, the method may be con-
sidered as reliable as any method of sampling used in other lines of

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Fig. 3.— The broken line connects series of fly counts at the garbage pails near kitchen; the solid
line, those at the stable. (Original.)

work. The use of a few fly papers in this way would not of itself
have any appreciable effect on fly prevalence. It was thought that
the use of fly traps would comphcate the situation in that any appar-
ent reduction in the number of flies might be ascribed to their use
rather than to the maggot trap.

A study of the fly counts shown in figure 3 reveals that there was a
decided drop in the number of flies both at the kitchen and stable very
shortly after the maggot trap was put into operation. Assummg that
all the flies at the stable and kitchen at the time the experiment began
(July 25) were freshly emerged and that they would aU die off wdthin
three weeks (there is some evidence that flies seldom live longer than
this in midsummer), one wovdd expect to find a reduction in the
number of flies about August 10 or 12. As a matter of fact this is
what occurred. Although the counts fluctuate considerably after

8 BULLETIN NO, 200, U. S. DEPARTMENT OF AGRICULTURE.

this date, in no case do the highest counts rise to the level of the
lowest counts made before August 10.

In one respect these counts hardly give a fair indication of the
effect of the maggot trap, this for the reason that the college kitchen
was closed from August 7 to September 7. It wiU be seen that flies
almost completely disappeared from the kitchen during the latter
part of August, but as soon as the garbage pails were again in use the
fly counts go up fairly high, although not as high as the lowest count
at this place before the experiment started. It is interesting to note
that while the kitchen was closed the fly counts at the stable were
somewhat increased and that after the kitchen reopened the flies
almost disappeared from the stable. Taking the counts at the
kitchen, we find that the average of the 10 counts before August 10 is
2,131, while the average of the 10 counts after August 10 is 692, an
average reduction of 67.5 per cent. At the stable the average of 9
counts before August 10 is 1,038, and the average of 12 counts after
August 10 is 248, an average reduction of 76 per cent.

The behavior of the horses standing in the stalls was also a fairly
good index of fly prevalence in the stable. As noted above, the
horses were constantly tormented during June and July. During the
day the stamping of feet and switching of tails was incessant. After
the maggot trap had been in operation for some time there was a
noticeable change. The horses stood much more quietly, and their
efforts to get rid of flies were less continuous. Several men at the
college observed this and volunteered the information.

INFLUENCE OF OTHER BREEDING PLACES ON THE NUMBER OF FLIES

AT THE COLLEGE.

If the maggot trap was really destroying 98 per cent of the flies
breeding in the manure at the college stable, why is there not a corre-
sponding reduction in the number of adult flies instead of an average
reduction of from 67 to 76 per cent ? The third series of observations
points to a probable explanation of this. As indicated on the map,
there are several breeding places within 700 yards of the college,
and 700 yards is well within the range of flight of flies, a fact which
has been proved by several workers. A few flight experiments with
marked flies were carried out during the season, not with the idea of
determining the range of flight, but merely to make sure whether or
not flies from these various breeding places found their way to the
coUege stable and kitchen.

First, about 600 recently emerged flies were thoroughly dusted with
finely powdered red crayon and liberated on August 31 at a point
near the stable indicated by the letter B (fig. 1). The point of
liberation was about 400 yards west of the college stable and perhaps
500 yards from the kitchen. In spite of the presence of several houses

Bui. 200, U. S. Dept. of Agriculture.

Plate I.

Bui. 200, U. S. Dept. of Agriculture.

Plate II.

Bui. 200, U. S. Dept. of Agriculture.

Plate III.

A MAGGOT TRAP IN" PRACTICAL USE. 9

and stables in the immediate vicinity, some of these marked flies
found their way to the college barn. Here two of this lot were
recovered within the first 24 hours, and a third one during the third
24-hour period. That no flies were recovered at the kitchen is to be
explained by the fact that the kitchen was closed and there was
nothing there to attract flies.

A second lot of about 500 flies, sprayed with rosolic acid, were liber-
ated at the dairy barn (A) of the experiment station, 700 yards due
east from the college stable. The distance from the kitchen is shghtly
less. They were liberated at 3.30 p. m. September 1. On September
3 two marked flies were found on papers exposed at the dairy barn,
but none was recovered at the college stable or kitchen. A strong
southwest wind was blowing at this time and may have had some
influence on the result. It is hardly to be doubted that when the
kitchen is in use numbers of flies from this source are attracted to it.
The manure pile back of the dairy barn was found to be heavily
infested at all times during the summer, and flies bred out here by the
thousands.

In a third experiment about 800 flies marked with powdered red
crayon were liberated on September 15 at the stable marked by
the letter C (fig. 1). Within the first 24 hours 11 marked flies were
recovered on fly papers at the garbage pails, and two more during
the second 24-hour period after liberation. No marked flies were
recovered at the college stable in this experiment. The kitchen was
in use at this time, and it must be considered significant that the
flies were recovered only at the kitchen, although they had to pass
right by the stable. This indicates the sharp rise in fly counts at
the kitchen when it reopened in September.

The same thing happened on September 22. A lot of about 600
flies sprayed with rosolic acid had been liberated on September 21
near the stable marked on the map by the letter D (fig. 1). None of
these were recovered at the college stable, but three were found within
the first 24 hours on papers exposed on the garbage pails at the
kitchen.

These few experiments indicate that a large number of the flies
which congregate at the college kitchen and stable come from near-by
breeding grounds other than the manure pile at the college barn.
And it may be said that a reduction of from 67 to 76 per cent in the
average number of flies, in spite of the proximity of these other
breeding places, speaks well for the efficiency of the maggot trap.

SOME DEFECTS OF THE MAGGOT TRAP.

The experience during the past season with the platform maggot
trap has directed attention to certain defects in its practical working.
These defects, however, are not of such a serious nature that they

10 BULLETIN NO. 200, V. S. DEPAETMENT OF AGEICULTUEE.

can not be overcome. In the first place, some trouble resulted from
smaller particles of manure sifting through between the cross strips
and accumulating in the water below. This was especially the case
when sawdust and shavings were used for bedding instead of straw.
If this material were allowed to accumulate there would fiinally be
enough of it to provide a breeding place on the concrete floor, where
the maggots should be kiUed by drowning. Much of this sifting
could be prevented by placing the cross strips closer together, so that
only ^-inch or even j-inch spaces were afforded. It is not at all
likely that J-inch spaces would interfere with migration; but in spite
of such improvement there would be, even with the most careful
handling, a certain amount of straw or small particles of manure
which would fall from the sides of the heap or from the fork at the
time it was put on the platform. It will always be necessary to clean
out the concrete floor more or less regularly, and for this purpose a
long-handled stable broom will be satisfactory when the water sup-
ply does not permit the use of a strong stream from a hose. To facili-
tate the cleaning of the floor the platform should not be less than
1 foot high nor more than 10 or 12 feet wide. The solid matter which
happens to be washed into the cistern will decompose in time and be
pumped back with the liquid onto the manure heap.

In dry weather evaporation of the water on the concrete floor wiU
leave large areas of floor surface dry. Larvae falling from the manure
above onto the dry floor wiU crawl away and can crawl up the vertical
sides of the surrounding rim ; in fact, they could crawl up this surface
even if it were as smooth as glass. To insure that all larvae are
drowned it is necessary to keep this in mind, and every day, when the
manure is added to the heap, more water can be supplied if necessary.
This operation will consume very little time.

The most serious defect was found in the fact that mosquitoes
bred very freely in the water standing in the concrete basin and in
the cistern. In order not to have one pest multiplying at the expense
of another, it is necessary to run all water out of the concrete floor at
least once a week and to clean the floor at this time; if then a little
oil is poured over the surface of the liquid in the cistern, mosquito
breeding wiU be prevented entirely. This method was used during
the last weeks of the experiment with satisfactory results. If the cis-
tern were carefully and tightly covered, perhaps the use of oil would
not be necessary.

No counts or estimates were made of the larvae destroyed during
October and November. It is known, however, that larvae continued
to appear in the water on the floor during the most of October and
during the warmer parts of November. On December 10 the manure
was examined without removing it from the platform, and therefore

A MAGGOT TRAP IN PRACTICAL USE.

11

not as thoroughly as on the former occasion, but there were found at
the fresher end of the pile at least four nests of several hundred puparia
each. It is not possible to estimate the percentage destroyed, but it
was quite plain that the trap was not as effective during the autumn
as in the summer. This may have been due partly to carelessness in
the matter of watering the heap, but more probably to the lower air
temperatures of this period. When the outside temperature is low,
the difference between the air and the temperature of the manure
heap is so great that the larvee will not leave the heap; and if the' low
temperatures prevail for a long period the larvag will eventually
pupate in the manure. The following experiment shows the effect
of low air temperature. This experiment was conducted at New
Orleans, La., in December, 1913. A small wire basket was filled
with fresh horse manure on December 1 and was continually exposed
to flies. The number of larvaB caught and the temperature during
the period are tabulated below.

Experiment to shoiv effect of low air temperature in preventing migration of house-fly
larvse, New Orleans, La., December, 1913.

Number
of larvse
caught.

Mini-
mum
tempera-
ture.

Maxi-
mum
tempera-
ture.

Mean
tempera-
ture.

Dec. 2 "-

12

15

47

199

745

" F.

57

56

57

56

57

48

40

32.5

34.5

38

41

47

58.0

49

50

52

55.5

51

° F.
74
67
68
73
70
61
61
50
56
59
65
68
73
66
62.5
69
60
58

" F.

65.5

3

61 5

4

62.5

5

64 5

6

63.5

7

55

8

14,000

0

1

43

465

1900

55

9

41.7

10

45.3

11

48.5

12

53

13

53

U

65 8

lo

1700

lis

1S5

leo

16

56.2

17

60.5

IS

57.8

19

54.5

1 Approximate. Counts of Dec. 8 and 15 include catch of preceding day.

Probably most of those that were caught on December 8 had
migrated during the night of December 6. Not much migration from
the manure takes place during the day, because of the maggots' nega-
tive reaction to light; therefore the minimum temperature is probably
more significant than the daily mean temperature. It will be seen
from the table that minimum temperatures of 40° F. or less wiU stop
all migration from the heap.

It may be said, then, that the maggot trap has another defect in
that it is not effective when temperatures are low, and that it is not
at aU effective when the air temperature is below 40° F.

12 BULLETIN NO. 200, U. S. DEPARTMENT OF AGEICULTUKE.
SOME ADVANTAGES OF THE MAGGOT TRAP.

Some of the advantages of the maggot trap are obvious enough and
need be only briefly mentioned here. It is an exceedingly simple
arrangement, and the initial cost of construction need not be very
great. Once having been constructed, no continuous money outlay
for its maintenance is necessary. The concrete parts are permanent,
and the wooden platform would require renewal only at intervals of
several years, depending partly on the kind of wood used. The writer
is of the opinion that in the long run the maggot trap would be less
expensive than the investment which many farmers now make in
screens for their dwellings and repellents, sprays, and fly nets for the
protection of their animals.

The labor required in the operation of the maggot trap is a very
small item. It is just as easy to place the manure on the platform as
to dump it on the ordinary pile. It requires only a few minutes each
day to see to it that the daily addition is carefully and compactly
heaped and the entire heap well moistened. The work of cleaning out
the floor below the platform will require about one-half an hour once
a week.

It is very easy to run a wagon or manure spreader close alongside
the maggot trap, as a glance at the photographs wiU show, and it
would be just as easy, or indeed easier, to load from such a platform
than from the ground. To facilitate loading as well as the cleaning
of the floor below, the platform should be no more than 10 or 12 feet
wide.

The maggot trap can be adapted for use on farms where the daily
production of manure is very great. As was stated on a preceding
page, the trap used in this experiment would hold the total production
from three horses for three months. Now the problem of construct-
ing a trap of reasonable size to take care of the manure of 40 or 50
horses is not as hopeless as might at first appear. The production of
manure per horse per day may be safely estimated at 2 cubic feet. It
will be seen that a platform 10 by 20 feet would hold manure produced
by 50 horses during a period of 10 days if the heap is made 5 feet high.
If two platforms are arranged as suggested in figure 4 they could be
operated as follows: Platform No. 1 woifld be gradually fiUed up
during the first 10 days; then, whfle this remains on the platform, the
manure produced during the second 10 days would bo placed on plat-
form No. 2; at the end of 20 days the manure on platform No. 1 would
be haule^ away and the platform refilled during the third 10-day
period while heap No. 2 was standing the length of time required to
rid it of maggots. In this way the two piles would alternate, the one
being in the process of formation and the other standing till practi-
cally aU maggots had left it. It would be convenient, as indicated in

A MAGGOT TRAP IN PRACTICAL USE.

13

the diagram, to have a cistern located between the platforms and a
pump that could be used in applying water to both piles. In making
plans for a maggot trap one must take into consideration the volume
of manure produced and the length of time it must remain on the
platform. As previously stated, it wiU be safe to estimate that the
production of manure per horse per day is 2 cubic feet and that after
10 days it will be practically free from maggots, provided it has been
well watered.

THE INFLUENCE OF THE MAGGOT TRAP ON THE VALUE OF THE

MANURE.

Plate III illustrates an aU-too-common method of keeping manure.
It covers a large area of ground, and no attempt at heaping has been
made. The manure in such a pile is loose and shallow, and air
penetrates mto practically all parts. These are the conditions

Fig. 4. — Imaginary cross-section of an arrangement suggested for use where manure production is large.
a. Pump; c, concrete floor and walls of cistern; o, outlet pipes leading from floor of maggot trap to
cistern; p, platform maggot trap; t, cistern for liquid manure; g, grotind level. (Original.)

which give rise to the maximum loss of ammonia and nitrogen. It
also happens that the conditions wliich tend to the loss of nitrogen
are the same wliich favor the development of fly larvae. An immense
surface is exposed for deposition of eggs, and the penetration of au*
makes it possible for larvae to feed in practically all parts. The
fresher portion of the manure shown in this photograph was found
heavily infested all through the season.

It has been shown that the losses occurring in manure thus care-
lessly stored will vary from 30 to 64 per cent of the total amount of
nitrogen (Beal, 1906), and that by careful methods of storage this loss
may be reduced to 15 per cent. Several methods of storage for the
purpose of preventing loss of ammonia and nitrogen have been
proposed. Among others is that recommended by Deheram, Beal,
Thome, Ringelmann, and others, which consists in keeping the manure
compactly heaped and well watered. Both heaping and watering
tend to prevent the penetration of air and thus check the destructive

14 BULLETIN NO. 200, V. S. DEPARTMENT OF AGRICULTURE.

aerobic fermentation. This method is used to a considerable extent
in parts of France and Germany and is fully discussed by Ringelmann.
A cistern is provided into which drain aU the liquids from the stables,
and the manure heap is watered by pumping the liquid manure from
the cistern from time to time.

It is the writer's intention here merely to point out that the disposal
of manure on the platform maggot trap is but a shght modification of
the method just mentioned. Figure 4 differs from a diagram given
by Ringelmami only in the platform and in the outlets through which
the drowned larvae may be washed into the cistern. Here is shown
the cistern in which the liquid manure collects. Watering with the
hquid manure adds to the heap the valuable constituents of the urine
and promotes the anaerobic fermentation. If it is true, as just
suggested, that lack of oxygen and the presence of carbon dioxid
render the manure unfavorable for the development of the larvae,
it foUows that compact heaping and watering, by excluding air and
increasmg the moisture content, also insure the greatest percentage
of migration. As a matter of fact, compactness and high moisture
content are the very factors wliich make the maggot trap most
effective, whether the explanation is to be found in the temperature,
or moisture, or lack of oxygen.

CONCLUSIONS.

In tliis paper we have described the structure of, and the method
adopted in using, a platform maggot trap. All the manure from a
stable m which thi'ee horses were kept was stored on this platform.
The results obtained during August and September seemed to show
that at least 98 per cent of the larvae breeding in this manure were
destroyed. Fly counts made before and after the trap was installed
indicated an average reduction of from 67 to 76 per cent. That the
reduction of fhes did not correspond to the percentage of larvae
destroyed was probably due to the presence of several other breeding
places weU within the range of flight.

Two difficulties were experienced in the practical working of the
trap, viz, the accumulation of a certain amount of straw and debris
on the floor under the platform and the breeding of mosquitoes
in the water used to drown the fly larvae. It was also found that
low air temperatures hinder migration and consequently decrease
the efficiency of the trap.

Among the merits of the maggot trap were mentioned (1) the com-
paratively small initial cost and absence of money outlay necessary
for its maintenance, (2) the very small amount of additional time or
labor required in its operation, (3) the ease with which wagons
or manure spreaders can be loaded from the platform, and (4) its
adaptabihty for use at stables where the daily production of manure

A MAGGOT TRAP IN PRACTICAL USE. 15

is large. Finally, it is suggested that the same conditions which
render the trap most effective are the ones which tend to preserve
the value of the manure.

REFERENCES TO LITERATURE.

Beal, W. H.

1904. Barnyard Manure. (Arevisionof Farmers' Bulletin No. 21.) U. S. Dept.
Agr., Farmers' Bui. 192, 32 p., 4 figs.
Brown, P. E.

1913. Farm Manures. Agr. Expt. Sta. Iowa State Col. Agr. and Mechanic Arts,

Circ. 9, 16 p., illus., April.
Deherain, p. p., and Dupont, C.

1900. Sur la composition des gaz confines dans le fumier de ferme. In Ann.

Agron., Paris, t. 26, p. 273-294.
Hewitt, C. G.

1914. Fui'ther observations on the breeding habits and control of the house

fly, Musca domestica. In Jour. Econ. Ent., v. 7. no. 3, p. 281-293,
figs. 20-21, June.
Howard, L. 0.

1911. The House Fly — ^Disease Carrier. New York.
Hutchison, R. H.

1914. The migratory habit of house-fly larv^se as indicating a favorable
remedial measure. An account of pi-ogress. U. S. Dept. Agr., Bui.
14, 11 p., Feb. 28.
Levy, E. C, and Tuck, W. T.

1913. The maggot trap — A new weapon in our warfare against the typhoid
fly. In Amer. Jour. Pub. Health, v. 3, no. 7. p. 657-660, illus., July.
Ringelmann, Max.

1913. Amenagement des Fumiers et des Purins, 187 p., 103 figs. Paris. (Nouv-
elle Bibliotheque du Cultivateur.)
Thorne, C. E.

1913. Farm Manures, 242 p., illus. New York and London.

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1915

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