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U. S. DEPARTMENT OF AGRICULTURE,
DIVISION OF ENTOMOLOGY— BULLETIN No. 42.
L. O. HOWARD, CHiifr OF DIVISION Of Hi
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SOME INSECTS ATTACKING THE ****"“"
WHEAT,
RYE, HARLEY, AND OATS,
WITH
METHODS OF PREVENTION AND SUPPRESSION.
* X V. . - ' •» \ ' ' \u ' ‘ r '
- . V y
PREPARED UNDER THE DIRECTION OF THE ENTOMOLOGIST,
BY
F\ Nl. WEBSTER, Nl. S.,
Special Field Agent.
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WASHINGTON:
GOVERNMENT PRINTING OFFICE,
I903.
U. S. DEPARTMENT OF AGRICULTURE,
. DIVISION OF ENTOMOLOGY — BULLETIN No. 42.
L. O. HOWARD, Chief of Division.
SOME INSECTS ATTACKING THE STEMS OF GROWING WHEAT,
RYE, BARLEY, AND OATS,
WITH
METHODS OF PREVENTION AND SUPPRESSION.
PREPARED UNDER THE DIRECTION OF THE ENTOMOLOGIST,
BY
F\ NT. WEBSTER, Eel. S.,
Special Field Agent.
WASHINGTON :
GOVERNMENT PRINTING OFFICE.
I903.
LETTER OE TRANSMITTAL.
United States Department of Agriculture,
Division of Entomology,
Washington , D. C. , September 25, 1903.
Sir: I have the honor to transmit herewith the manuscript of a
paper entitled 44 Some insects attacking the stems of growing wheat,
rve, barley, and oats,“ prepared under my direction by Prof. Francis
M. Webster, temporary field agent of the Division of Entomology,
and now stationed at Urbana, 111. Professor Webster has acted as
field agent of this Division, having received temporary appointment
since 1884, with headquarters at the experiment stations of Indiana,
Ohio, and Illinois, and is abl}T qualified for the prosecution of the
present work through }^ears of study in the States mentioned of the
insects which will be treated. As remarked in the introduction, this
paper deals with the injuries committed to small grains by different
forms of minute flies, eight species in all, which are generally confused
by the average farmer with the Hessian fiy. The differences between
these various species and their method of attack in comparison with
that of the Hessian fly are dul}r pointed out, and many valuable sug-
gestions based upon an intimate knowledge of the habits of these
insects are made for the mitigation of their ravages. In most instances
losses by these insects could be prevented b}T the simplest of farming
practices, as set forth in their proper place. I recommend the publi-
cation of this report as Bulletin No. 42 of this Division. The fifteen
text figures are necessary for the purposes of illustration, those illus-
trating plants having been kindly loaned by the office of Agrostologist.
Respectfully,
L. O. Howard,
Hon. James Wilson, Entomologist and Chief.
Secretary of Agriculture.
2
CON T E N T S .
Paga
Introduction 7
The genus Isosoma 9
Dealing with the destructive species outside of the grain fields 11
The greater wheat straw-worm ( Isosoma grande Riley) 14
Previous record of the insect 14
Discovery of the summer form 15
Discovery of dimorphism and alternation of generations 16
Riley’s name, Isosoma tritici, invalid 17
Life history 17
Oviposition of the spring form ( minutum ) 18
Oviposition of the summer form (grande) 19
Description 21
Adults of summer form ( Isosoma grande Riley) 21
Larva, pupa, and egg of summer form 21
Adults of spring form (Isosoma minutum) 21
Larva and pupa of spring form 21
Natural enemies 22
Preventive and remedial measures 22
Distribution 23
The joint worm (Isosoma tritici Fitch) 23
Previous record of the insect 24
Life history 26
Distribution 26
Description 27
Adult female 27
Adult male 27
Natural enemies 27
Remedial and preventive measures 28
Difficulty in recognizing the species 28
The barley straw-worm (Isosoma liordei Harris) 29
Previous records of the insect 29
Life history 31
Effect of the larvye on the plant 31
Description 32
Adult female 32
Adult male 32
Natural enemies 33
Preventive measures 33
The captive Isosoma (Isosoma captivum How.) 34
Description 34
Adult female 34
Adult male 35
3
4
The genus Isosoma — Continued. Page.
Webster’s Isosoma (Isosoma websteri How. ) 35
Description of adult female 36
The hairy-faced Isosoma ( Isosoma hirtifrons How.) 36
Description of adult female 37
Isosoma secale Fitch 38
Description 38
Adult female. 38
Adult male „ 38
Fitch’s Isosoma ( Isosoma fitchii How.) 39
Description 39
Adult female 39
Adult male 39
The two-winged grain and grass flies 40
Were probably originally grass feeders 41
Early reports of injuries to grain 42
The greater wheat stem-maggot (Meromyza americana Fitch) 43
Past history of the insect 43
Life history 46
Description 47
Adult fly, egg, larva, and pupa 47
Food plants 47
Selection of food plants by the adults 48
Place and method of oviposition 48
Method and nature of attack 49
Extent of ravages 50
Preventive measures . 50
Natural enemies 51
The lesser wheat stem-maggot ( Oscinis carbonaria Loew) 51
Life history 52
Food plants 53
Place and method of oviposition 53
Nature of injury 53
Extent of ravages 54
Description of adult 54
Close resemblance to Oscinis soror Macq 55
Description of egg, larva, and pupa 55
Preventive measures 56
Natural enemies 56
The American frit-fly ( Oscinis soror Macq. ) 57
Confusion with other species 57
Depredations in Minnesota 58
Life history 59
Food plants 60
Difficulties in studying habits 60
Remedial and preventive measures 61
Description ' 61
Conclusion 62
ILLUSTRATIONS.
Page.
Fig 1. Canadian rye grass ( Elymus canadensis) 12
2. Virginia rye grass ( Elymus virginicus) • 13
3. Greater wheat straw-worm (Isosoma grande Riley), spring generation,
form minutum ; stages 14
4. Greater wheat straw- worm ( Isosoma grande Riley ) , adult summer form . 14
5. Head of wheat partly destroyed by Isosoma minutum 18
6. Method of oviposition of female of summer form (I. grande ); b, point
in straw where egg is placed 20
7. Pedicidoides ventricosus Rewp., a mite which destroys the larva 22
8. Isosoma tritid Fitch; adult of the joint worm 24
9. Effect of joint worm in wheat straw 25
10. Isosoma liordei Harr. ; adult of the barley straw-worm 30
11. Isosoma captivum How.; adult 34
12. Isosoma websteri How.; adult female 35
13. Isosoma hirtifrons How.; adult female 37
14. Greater wheat stem-maggot (Meromyza americana Fitch); stages and
effect on young wheat plant 44
15. Oscinis soror Macq., stages; cZ, head of Oscinis carbonaria 52
5
SOME INSECTS ATTACKING THE STEMS OF GROWING
WHEAT, RYE, BARLEY, AND OATS.
INTRODUCTION.
Throughout the United States, where the smaller cereal grains —
wheat, rye, barley, and oats — are to any considerable extent cultivated,
a multitude of injuries to growing* wheat are charged by the average
farmer to the Hessian fly; whereas, in many cases these ravages are
really the work of insects whose habits differ greatly from those of
that insect. Indeed, some of them are not flies at all, and even
where the ravages are caused by flies, these are not necessarily the
Hessian fly, and the same remedial and preventive measures that are
applicable to this notorious wheat pest may not be at all effective
against them. In fact, it is with the hope of enabling the farmer, as
also the economic student, to distinguish between some of the chief
insect enemies of cereal grains, and especially between many of them
and the Hessian fly, that this publication has been prepared.
In the following pages the author has restricted himself to the con-
sideration of two groups of grain-affecting insects, the one composed
of true flies, and the other not, though both during their developmental
stages live and thrive within the stems of wheat, and to some extent
within those of the growing grasses as well. Indeed, as a whole, they
were doubtless primarily grass feeders, and their grain-attacking
habits, being of more recent origin, brought about by the changed con-
ditions of their natural food supply, consequent upon the influences of
advancing civilization, may be looked upon as a modification of their
original methods of living.
While this variety of food plants, including the wild grasses, as well
as the cultivated grains, probably has the effect of more generally
diffusing some of these insects, thus rendering serious outbreaks of
less frequent occurrence, the other phase of the problem is that though
the farmer might exterminate them from his fields, they would still
inhabit the grass lands and from there continually send a fresh supply
of colonists into his fields to repopulate them. But, again, this has
its redeeming features, as it enables the grain grower, in some cases,
to meet his enemies in the grasses and there fight them to better
advantage to himself than in his cultivated fields. The Hessian fly is
8
an exception, as it has yet to be found attacking the grasses in this
country; }ret several insects whose injuries in the wheat fields have
been charged up to it by the farmer may be destroyed to a greater or
less extent by closely pasturing the roadsides and fence corners in
summer or burning them over in winter or early spring.
The first group of these grain-attacking insects to which attention
will be here given is composed of those that are not flies at all in the
true sense of the term, but small ant-like creatures, realty related to the
ants which they so closely resemble. Their young live within the stems
of the smaller cereal grains and grasses, and, though these rarely kill
the wheat stems outright, they may either prevent the production of
the kernels or cause these last to shrink and shrivel, thereby greatly
reducing them both in weight and market value. These insects are
called the grain and grass Isosomas, and their young are the wheat
straw- worms and the joint- worms. What is still more surprising, they
belong to a group of insects the majority of which are not vegetable
feeders, but parasitic on other insects, and it was a long time before
entomologists were willing to accept the fact that they were the real
depredators and not parasites. This doubt as to the real food habits
of these insects had not entirety disappeared up to 1884, when the
author proved by successive rearings not only the vegetal habits of one
of the species, but also the even more interesting fact of dimorphism
and an alternation of generations, showing that what appeared to be
two species was realty two generations of one of them; but one of the
generations, being wingless in the adult stage, renders it the more
easily controlled by the farmer through a rotation of crop/*
The second group of insects here considered is composed of true
flies, and these also are both grain and grass feeders in the larval or
maggot stage. All true flies have but two wings, and the maggots
have no jaws, but the mouth parts consist of two minute hooks whereby
they tear or slightly wound the surface of the tender stems and suck
the juices flowing therefrom. The Hessian fly is also a true fly, but
its form partakes more of that of the mosquito, while these under con-
sideration have very much the form of the common house fly, except
that they are smaller, and they are frequently quite differently colored.
The maggot of the Hessian fly is larger and more robust than are
those of the Oscinids, though shorter and differing in color from those
of Meromyza.
Judging from my own experience and observation, these insects are
much more injurious to the young grain plants. One brood of mag-
gots of Meromyza work in the full-grown straw it is true, but, as a
rule, the injury at that time is seldom very severe, while the larvae of
the Oscinids are rarely found in the full-grown straw, except in the
« Reports U, S. Comm. Agr., 1884, pp. 383-387; 1885, pp. 311-315; 1886, pp. 573-574.
9
extreme north, notably in Minnesota, and in Manitoba and the North-
west Territories in Canada. The Isosomas do not attack the grain
plants in the fall, and thus we have a natural division between the two,
which is applied in the discussion of these insects in the following
pages.
The Oscinids are not destructive in this country alone, as allied
species have long been a serious pest in England, France, Germany,
and Sweden. The frit-fly ( Oscinis frit Linn.), is some years especially
destructive in Europe. The gout-fly ( Chlorojps tseniojms Meigen) and
the wheat bulb-fly ( Ilylemyia coarctatci Fallen) are both more or less
injurious to small-grain crops in England.
In the preparation of this bulletin the writer has been greatly aided
by Dr. Howard and his corps of assistants, both in the Department of
Agriculture and also in the United States National Museum, and by Dr.
S. A. Forbes in kindly and promptly placing the notes and collections
of the Illinois State Laboratory of Natural History at the author’s
disposal. The writer is also indebted for specimens to Dr. James
Fletcher, entomologist and botanist for the Dominion of Canada, and
for similar favors received from Prof. F. L. Washburn, State ento-
mologist of Minnesota.
THE GENUS ISOSOMA.
The grass and grain joint- worm flies belonging to this genus are
widely distributed in America, some of the most important ranging
from the Atlantic to the Pacific coasts and from Canada southward
probably as far as the grains, wheat, rye, and barley are grown.
The genus Isosoma is known to inhabit Europe, Africa, Madeira,
St. Vincent, Australia, and Tasmania. In Europe it ranges over
Russia, Switzerland, Germany, Austria, and Italy. When the insect
faunas of Asia and Central and South America come to be better
understood, we shall in all probability find that species occur in those
countries also.
These insects belong to the Chalcididae, a family of parasites whose
normal food is other insects in one or more stages of their develop-
ment. For a long time entomologists refused to believe that the
species of Isosoma and their allies were exceptions to this supposed
rule, and Harris firmly believed that Isosoma liordei was a parasite
and not the true depredator in barley straw. Dr. Asa Fitch after-
wards established the fact of ph}Tophagic habits in 1. hordei as well
as in several other species, but English and European entomologists
were not wholly convinced, at least not all of them, up to as late as
1882. When the writer began the study of grain-infesting Isosoma
in 1881, comparatively little was known of the habits of some of our
most common species, and the establishing of the fact of dimorphism
10
and alternation of generations b y him in the case of Isosoma tritici
Riley, as it was then known, and I. grande was without a parallel, in
this genus, and so remains in this country. Among the ten or twelve
American species that I have reared, none of the others, so far as I
have been able to determine, enter the pupal stage in the fall and
winter in that condition, a and thus the greater wheat straw-worm ( Iso-
soma grande) is one stage in advance of the others in spring, and
the spring form, minuta , is developed at the time when other species
are entering the pupal stage. This is also the only species that I have
not succeeded in rearing from food plants other than wheat, with the
possible exception of Isosoma websteri , which might have been reared
from young cheat plants, though I hardly think this probable. The
fact that I have only found this latter species in spring, and then only
females, is indicative of a dimorphism and alternation of generations;
but unless it be an undescribed species reared from stems of Tricusjpis
sesleroides , which is very late to mature, being even later than any
other species known to me, I do not think such alternation can be
connected with any other species that I have studied. On the other
hand, and at the other extreme in the matter of food plants, the
E^mus Isosoma (Z elymi French), has never been with certainty
reared from wheat, though abundantly from the stems of cheat grow-
ing among wheat and from Elymus growing along the margins of
wheat fields.
I also find, much to my surprise, that I have reared Fitch’s Isosoma
tritici aside from its known food plant, wheat, only from Elymus vir-
ginicus. Even where this latter grass and the closely allied E. cana-
densis have grown side by side, the joint worm ( Isosoma tritici
Fitch) has held strictl}r to the former. The white-spotted Isosoma
(Z albomaculata Ashmead), perhaps the most closely allied to Z grande
of any of the species known to me, and which we should suppose
would more than any other incline to dimorphism and alternation of
generations, seems, however, to show no such tendency, and, more-
over, I have reared it from both cheat and Elymus virginicus , the life
cycle, so far as I have been able to follow it, being parallel with those
of Isosoma elymi , Z tritici , and Z hordei . I do not, of course, wish
to obscure the possibility of an alternation of generations among these
insects, with a different food plant for each generation. On the
opposite page is given in tabulated form the food plants of the spe-
cies of Isosoma known to attack grains and grasses in North America.
a Should the observations of Dr. Andrew Xichols, given under Isosoma hordei,
prove correct, this may in future prove erroneous as to I. grande, unless the latter
also attacks barley. — F. M. W.
11
DEALING WITH THE DESTRUCTIVE SPECIES OUTSIDE OF THE
GRAIN FIELDS.
In attempting to control the grain-infesting Isosoma, the practical
farmer will, in several ways, find himself at a disadvantage. The
very deceptive resemblance of these insects to ants, and also to others
actually beneficial, will prevent his readily recognizing them in the
fields, even if he were to see them at all, and it is only wThen, by acci-
dent, perhaps, that he finds the worms in the stems of his grain, that
he will ordinarily be able to detect their presence. As the develop-
ment of the insect takes place entirely within the straw, rarely,
except in the case of two species, showing any external effects, much
injury may occur to the kernels of grain without his being able to
determine the cause. It is, therefore, advantageous to him to know
that he may reduce the chances of injury by careful attention to the
uncultivated areas that inevitably surround his cultivated fields. As
an illustration of the influence of neglecting uncultivated patches like
fence corners and roadsides, and allowing these to become overgrown
with the different species of rye grass (Elymus), I give the results of
my own rearings of these insects from stems of grasses, taken from two
different localities along the Illinois Central Railway. In connection
with what is here given, it might be well to call attention to the fact
that the grounds within the fences along our more important railways
are usually better kept than are similar uncultivated grounds along
the highways, to say nothing of the fence corners, borders of open
ditches, and similar tracts on the premises of the farmers themselves.
The locality' from which I secured the greatest number of barley
straw-worm flies (Isosoma hordei) is situated about 2 miles north of
Champaign, 111. The contour of the ground is such that mowing over
in summer is difficult, and burning over in winter, though practical,
probably did not seem necessary to the railway people. As a conse-
quence, a small tract grew up to the Canadian rye grass (Elymus
12
canadensis , fig. 1), the stems of which literally swarmed with the larvae
of this species. It beyond question would have furnished enough
adults to have stocked hundreds of acres of barley had it been within
reach. The presence of the old stems clearly indicated that the place
had been neglected for years, and grass stems of the previous year
were filled with punctures where the adults had made their escape.
Without anyone knowing it, there was here kept a perpetual nursery
for barley straw- worm flies, and though not at present a barley coun-
try, it is true, it is easy to see what the effects would be were the sit-
uation otherwise and must be elsewhere where this grain is more
largely grown.
The locality from which I secured the least number of these insects,
and, in fact, none of the grain-attacking species
at all, is located along the same railway, in the
edge of the village of Peotone, 111. Here the
topography of the ground along the railway is
even worse than that in the Champaign locality,
but close proximity to the village rendered more
attention to it necessary. I am informed by
those living near the place that it is regularly
mown off during the latter part of June and
again in September. The material used in my
breeding experiments was collected August 12
at Champaign and August 21 at Peotone, and,
though the Canadian rye grass was much more
abundant in the latter locality, and to all out-
ward appearances at the time the material was
secured offered the joint- worms a far superior
place to develop there, yet with ample material
I did not obtain a single individual, though in
Dekalb Count}^, about 60 miles west of Chicago,
where, to my certain knowledge, no wheat or
barley has been sown for years, from grass col-
(. Elymus canadensis ), (after lected August 20 I reared quite a number of
scnbner). these insects. The Dekalb County material was
collected from along the neglected roadsides in the country. I can
see no possible explanation of the difference in abundance of the joint-
worms in the rye grass secured at Champaign and that secured at
Peotone, except the difference in the attention given to mowing off
the grass during the summer — the same attention that farmers can
without trouble give to the roadsides, fence corners, and ditch bor-
ders on and about their own premises. These things are a part of
good husbandry, yet among intelligent farmers I have found the two
species of rye grass growing not only by the roadsides, but along the
very borders of their wheat fields, in some cases the grass and wheat
being intermixed along the extreme edges of the fields of grain.
13
Under much the same conditions I have reared the greatest numbers
of joint-worm flies, at present known as Isosoma tritici Fitch, from the
Virginia rye grass {Elymus virginicus, fig. 2). In this case the grass
from which I secured these insects in greatest profusion came from
the most neglected roadsides. In the vicinity of the citvT of Urbana,
111., I secured material from two localities, one quite near the resident
quarter, where the city government required the mowing off of weeds
and grasses, commencing in June, and the other farther from town,
along a neglected bank where the
grass was allowed to grow up un-
disturbed year after year. From
grass stems from the former local-
ity I secured almost nothing, while
from that coming from the latter
localit}r I obtained enough to show
that there was here a constant
menace to the wheat fields in the
neighborhood. Now, as a matter
of fact, there is comparatively
little wheat or rye grown in the
neighborhood, and until I reared
these insects from the wild grasses
I could not account for their sud-
den appearance in the wheat and
rye fields, observed and recorded
in former years by Professor
Forbes and his assistants. What
has proven true here has been
shown to follow similar conditions
elsewhere in both Illinois and
Indiana. That is to say, where
farmers have allowed these grasses
to grow up about their farms year
after year under the impression
that they were not worth any attention, I have found the insects in
abundance, and also find that despite their otherwise good farming,
they have probably suffered more or less from the attacks of the
two species of destructive Isosoma in their grain, though they may
not have observed them or their subtile effects on the kernels of the
wheat and rye. I am convinced that there is an element of loss here
of which farmers are unaware and the precise effects of which they
do not therefore comprehend, yet might if they realized the situation.
Fig. 2. — Virginia rye grass ( Elymus virginicus )
(after Scribner) .
14
THE GREATER WHEAT STRAW-WORM.
( Isosoma grande Riley. Fig. 3, form minuta ; fig. 4, form grande.)
PREVIOUS RECORD OF THE INSECT.
The history of this species extends back only to 1880, though it was
probably for many years confused in wheat with the joint-worm.
It sometimes occurs that insects which the systematist can only con-
sider distinct prove on thorough study to belong to one and the same
Fig. 3. — Greater wheat straw-worm ( Isosoma grande Riley), spring generation, form minutum: a, b,
larva; /, female; g, fore-wing; h, hind-wing; all much enlarged (from Riley).
species, while, on the other hand, it sometimes occurs that what the
systematic entomologist considers the same species prove on investi-
gation to be entirely different, and thus the problem of control, if
injurious, is either simplified or complicated, as the case may be.
However easy it may
appear to the farmer,
to learn all of the life
history of an insect is
not unfrequently a
matter of no little dif-
ficulty. Where we can
follow out the life cycle
of a species accurately,
there is usually found
some place or period
in its existence when
it is more easily con-
trolled or destroyed
Fig. 4. — Greater wheat straw-worm ( Isosoma grande Riley), adult ^ anV Other time
summer form, much enlarged (from Howard). _ " ,
and it otten occurs that
at the critical point some simple manipulation of his land or his crop,
on the part of the farmer, will accomplish wonders. This species
seems to offer illustrations of all of these features.
A
15
In June, 1880, Mr. J. K. P. Wallace, of Andersonville, Tenn., sent
to Dr. C. Y. Riley a number of wheat straws containing larvae, with
the complaint that nearly ever}T stalk or straw was affected by them,
and, as a consequence, the straw was inclined to fall before the grain
had fully ripened. Mr. J. G. Barlow, of Cadet, Mo., about this time
also complained of a similar trouble in his neighborhood, in some cases
resulting in nearly a total loss of the crop. In the winter of 1881-82,
Dr. Riley was able to rear some 30 adults from these infested straws,
and, as he considered the species described by Dr. Fitch only a variety
of the barley straw-worm ( Isosoma liordei Harris), he described the
adults obtained from these straws as Isosoma tritici Riley, which
description was published in the Rural New Yorker March 1, 1882.
This w^as the situation and the condition of our knowledge of the
species at the time the writer was appointed a special agent of the
Division of Entomology, of which Dr. Riley was then chief, and
under his instructions began the study of these and other grain insects
in Ma y, 1881.
DISCOVERY OF THE SUMMER FORM.
On May 8, 1881, in a field of wheat near Bloomington, 111., I found
Isosoma tritici Riley, as it was at that time known, in considerable
numbers, crawling over the young wheat plants, and on the 11th of
the same month watched a couple of females deposit their eggs in these
growing plants. On May 30, while examining plants from this same
wheat field, young Isosoma larvae were found in the stems, and I also
found larvae in the stems in which I had observed the captured females
to oviposit May 11, but these last were much too large for Isosoma
tritici. During the previous few days I had been getting from fields
of both wheat and rye in the same locality a much larger Isosoma,
possessing fully developed wings, and on May 29 a pupa, also too
large for I. tritici , was found in the upper part of a dwarfed wheat
plant. In the light of more recent studies we now know that I had
three species under observation instead of one. The small individuals
found early in the month of April belonged to the spring form of this
species, and others were lsosoma websteri , while the larger individuals
swept from wheat and rye, later in the month of May, were some
of them the summer form ( I. grande ), and others belonged to another
species, afterwards described as lsosoma captivum Howard. My field
of observation was at this time transferred from Bloomington, 111., to
Oxford, Ind.
On June 6, in a field of wheat near Oxford, I observed female Iso-
somas, seemingly like those taken a few days before in the wheat and
rye fields near Bloomington, ovipositing in wheat plants, well up
toward the top of the stem, probably between the upper joint and the
one next below, although, on account of the head of the wheat having
not }ret put forth, it seemed as though the egg was being placed in the
16
upper joint. A large number of these adult females were secured, and
these constituted the types upon which the description of Isosoma
grande was based. a
DISCOVERY OF DIMORPHISM AND ALTERNATION OF GENERATIONS.
At harvest I arranged with the owner of the field near Oxford to
allow a small area where I had witnessed the oviposition of the female
Isosomas to remain uncut, and I afterwards secured these straws, a part
being kept out of doors and the remainder kept within doors during
the following winter. Some conception of the extent to 'which these
straws were tenanted by the larvae of this species may be gained by the
fact ‘that of 90 straws from the same field 81 were infested and con-
tained 136 larvae. These straws were cut close to the ground, and,
therefore, the contained larvae represented the total number. Of 90
straws as cut by the harvester, there were a far less number of larvae
present, only 25 being found in the entire lot, the remainder having
been left in the stubble.
By October all of the larvae had pupated, and my first adult was
obtained December 7 from the lot of straws kept indoors. From
this time on till J une I continued to secure adults issuing from these
straws, but everyone of them were Isosoma tritici Riley. All of the
straws were now split open in order to determine whether or not any
individuals still remained, but none were found.
My first adult from the straws kept out of doors appeared March
23, and others continued to appear up to the first week in April, all, as
with the straws kept indoors, being Isosoma tritici Rileys These
straws were now split open and examined, but there was no trace of
lsosoma grande , which I knew had deposited eggs in these very straws.
Despite all this, on June 1, in sweeping the grass along the borders
of a wheat field at Lafayette, Ind. , only about 20 miles from where
1 had found them the previous year, I captured lsosoma grande , and
on the following day found them present in the wheat fields.
During the fall of 1885 1 took the precaution to sow a small plat of
wheat and so protect it that no insects could reach it. The cover was
renewed in spring, and some of the lsosoma tritici emerging from
straws taken from the field the previous summer were placed in
the inclosure where the }Toung protected wheat plants were grow-
ing. The adults were placed on this young wheat April 12, and the
utmost care taken to prevent any other insects from reaching them,
a The records and material in the files and collections of the State Laboratory of
Natural History show that what is probably7 the larvae of this species was found in
abundance in wheat straw in the fields in southern Illinois, in July, 1884, and adults
of the summer form ( grande ) were collected byr Mr. Garman, at that time an assistant
of Dr. Forbes, in various localities in southern Illinois, during late May7 and early
June, 1884, or just about the time that I began to observe it about Oxford, Ind.
17
and, besides, the fields were closely watched for Isosoma grande. On
June 2, fift}T-one days after, I found a female of tsosoma grande in the
inclosure and in the act of ovipositing in the now full-grown wheat
plants. Others were observed similarly engaged during the follow-
ing fortnight, and when the straw was ripened it was cut off' and
placed in glass jars. I had thus again reared the one supposed species
from the other. During the following winter many adults were reared
from these straws, but all were of the one form (/. tritici Riley), and
I had reared the two forms twice from each other, leaving now no
further doubt that they were simply two generations of the same
insect, besides showing that as the spring generation is without wings
and can not fly from one field to another, a simple rotation of crop on
the part of farmers would result in keeping the insect so reduced in
numbers as to place it out of necessary consideration as a wheat-
destroying insect.
In all of my own rearings of both forms of this species I did not
secure a single male, and of the large number reared at the Depart-
ment of Agriculture at Washington, from material furnished by me,
but three individuals of this sex were obtained. a
riley’s name, isosoma tritici, invalid.
In a more recent study of these insects, b Dr. L. O. Howard found
that the species described by Dr. Fitch as Isosoma tritici was a valid
one. This being the case, Riley’s name must no longer be used, and
the later one, Isosoma grande , thus covers both. Doctor Howard has
given the name minutum to the wingless spring form, and this name
will hereafter be used in this paper.
LIFE HISTORY.
The insect passes the winter in the center of the straw, just above
the joint, in the pupal stage. Rarely an adult will emerge in late
autumn, but if kept indoors others will appear during December, the
most during January, showing that they are ready to appear during
the first settled warm weather in spring. In further proof of this, I
have found hat as the winter advances they require less time indoors
in which to develop than if the straws are brought in in December,
thus showing that, while subject to all of the influences of winter, they
are undergoing a change that carries them nearer to maturity. A ith
the settled spring weather the}r eat a round hole in the straw and
make their way forth. As males are few they rarely pair, if at all,
but are ready to begin oviposition as soon as out of the straw. They
ai —
a Report U. S. Comm. Agr. 1886, p. 573, footnote.
& Grass and Grain Joint-worm Flies and their Allies, Tech. Ser. 2, Div. Ent.,
U. S. Dept. Agr.
7327— No. 42—03 2
18
Fig. 5. — Head of wheat partially de-
stroyed by Isosomci minutum (drawn in
Division of Entomology).
are, except in rare cases, entirely devoid
of wings, and migration is therefore out
of the question, except for short distances.
OVIPOSITION OF THE SPRING FORM
(minutum).
At the time that the minute, wingless
females that comprise this form appear
in spring the young wheat plants are only
starting to throw the stem upward, and
if one will take the trouble to cut one of
them directly through the center, longi-
tudinally, he will be able to observe the
embryo head not far above the surface
of the ground. Pushing its ovipositor
through the stem to the center, the mother
insect places her egg in the embr}m head,
which is not only the most vital part of
the plant, so far as the fruitfulness thereof
is concerned, but where her offspring will
be in the midst of the most tender and
highly nutritious food possible. As a re-
sult of this the young head is destroyed
and further growth of the stem prevented.
In some instances the young larva is itself
destroyed before it has finished its destruc-
tion of the head, and a distorted wheat
head supported by a dwarfed and weakly
stem is the consequence. One of these
partly destroyed heads is illustrated in
fig. 5. In most cases the stem ceases to
grow, withers up, and dies, though usu-
ally standing upright, at the height of from
1 to 6 inches, with the leaves drooping down
about the stem, both dead and discolored.
In feeding on the young head the larva
forms a. cell-like cavity which, owing to
the size of the larva and pupa, sometimes
takes on a somewhat gall-like appearance,
not noticeable except when cut in two. It
would seem that the superior article of
food which nature provides for these lar-
vae might to some extent account for the
larger and more robust adults which
constitute the second or summer brood.
The larvae must develop quite rapidly, as,
19
by June 10, nearly all have transformed to the adult summer form
( grande ). which begins to appear about June 1, reaching its maximum
in point of numbers about June 20, though I have found an occasional
individual as late as the 27th of that month. In ovipositing, minutum
seems to prefer the lateral stems in which to place her eggs, thus
leaving the central stem unaffected. With the summer form {grande)
this selection is reversed and the largest and most thrifty stems are
selected. Spots of rank growing, thinly placed grain will suffer worse
than the more densely growing areas.
OVIPOSITION OF THE SUMMER FORM (GRANDE).
Nurtured in the midst of the embryo head, we would natural^ look
for an adult insect differing somewhat from the one developing from
larvae whose food is of a coarser and tougher nature, and in this case,
whether as a coincidence or otherwise, we have a much larger insect
with fully developed wings, forming in consequence the migratory
brood of the species. That these females wander about from field to
field is shown by the fact that they' may be captured during June by
sweeping over the grass lands with an ordinary insect net, such as is
used by entomologists for this purpose.
The method of oviposition between the spring and summer forms
does not differ materially, except as the difference in the conditions of
the plant makes slight variations necessary. The former must place
her eggs in the very young plant comparatively close to the surface
of the ground, while the latter seems to try to get her egg immedi-
ately above the uppermost joint of the wheat stem within her reach.
At the season of the year when this takes place the upper, and fre-
quently the joint next below, is not uncovered by' the leaves and
sheath, but the majority of the eggs are placed, singly, just above
either the second or third joint below the head, and rarely above the
upper joint. The significance of this to the farmer is that very few of
the larvae hatching from these eggs will be taken away with the straw,
but, on the contrary, left in the field in the stubble. If the reverse
were the case, and most of the larvae removed with the straw to the
barnyard, there to be either run through the stables or similarly util-
ized, in most cases hardly an individual would get back into the wheat
fields in spring, for it must be remembered that at this period the
adults are wingless and incapable of flying. The method of oviposi-
tion is shown in fig. 6, <2, and the point where the egg is deposited in
the straw is shown in figure 6, b, the transverse line showing the track
of the ovipositor. To place her egg, the female takes up her position
just above the joint, with her head downward. She then straightens
her legs, thus throwing her body away from the stem, at the same
time bringing her feet almost directly beneath the body. She now
brings the abdomen downward and forward between her legs, much
20
as a bee would do if alighting and instantly stinging an animal. The
next move is to let the tip of the abdomen strike the stem and then
go back to its proper position, but the tip of the ovipositor does not;
on the contrary, it catches on the surface of the stem, directl}" beneath
the body of the insect, and by putting its machinery in motion and
drawing the stem toward her she slowly forces the ovipositor into the
soft, juicy stem at the point where this is solid and not hollow, as is
the case a. short distance above and immediately below the joint. The
tip of the ovipositor is composed of two flattened plates arranged side
by side, the edges of which are sharp, and are propelled with a sort of
rotary motion alternating with each other. In this way the ovipositor
cuts and drills its way to the center of the stem, and an egg is forced
down the interior and left in its proper place in the stem of the plant.
The female recovers her ovipositor by again straightening her legs
and pushing the plant from her. Only
one egg is placed in the same location,
though perhaps more than one is placed
in the same straw by the same female,
but if so they are placed above different
joints in the straw. The larvae must
mature quickly, for, though pupation
does not take place until about October,
the stem ripens and becomes tough and
woody, wholly unfit for the food of the
larvae, within less than a month. It
would seem that the mother insect is
aware of this, as she invariably selects
the greenest and rankest growing plants
in the more open spots, where the straw
matures the slowest and remains green
and juicy the longest.
Briefly, then, the insect passes the winter in the stubble — with the
exception of the few that haAre been removed with the straw — in the
pupal stage. In late March or during April the spring form
\minutum ), small, jet-black, ant-like, and with rare exceptions wing-
less females, eat their way out of their winter home and seek the
}xoung growing wheat plants. They deposit their eggs singly, placing
them in the embryo head. These hatch within a few daj^s and the
larvae mature and transform to the form grande , large, robust, also
jet-black, with fully developed wings, in late May and the first two-
thirds of June. These last are also females, and without pairing they
begin to deposit their eggs in the now nearly full}" developed straws.
The eggs are placed just above the uppermost joint accessible to the
female, usually the second or third below the head. But a single egg
is deposited in a place, the object of the mother insect seeming to be
to get it in the center of the stem in the more or less solid portion
Fig. 6. — Method of oviposition of female
of summer form ( Isosomci grande,
Riley): a, female inserting her eggs;
6, section of wheat stem showing point
reached by oviposition (after Riley).
21
just above the joint. The eggs, as with those of the spring brood, hatch
in a short time, and the larvae reach maturity by the time the straw
has become too tough and dry to afford further nutriment. The larva
at this time usually gnaws its way down into, or at least partly into,
the joint, and without forming cell or cocoon, about October passes
into the pupal stage.
DESCRIPTION.
ADULTS OF SUMMER FORM.
( Isosoma grande Rilev.)
Length of body, 4.2 mm.; expanse, 7.6 mm. Antennae rather more slender and
less clavate than in the spring form and bat half the length of the thorax. Thorax
with the mesonotum slightly more rugulose; wings larger and less hyaline than in
the winged specimens of the spring form, with the veins extending to the outer
third, the submarginal nearly four times as long as the marginal; legs with the
femora less swollen. Abdomen not so long as the thorax, stouter than in the spring
form, ovate-acuminate, approaching typical Eurytoma. Less hairy than in the spring
form, especially about the legs, the hairs about the abdomen being less numerous,
less regular, and shorter. Coloration similar to that of the spring form, but brighter
and more highly contrasting, the promotal spot larger and brighter yellow, the
pedicel of the antennae yellow, and the femora with a definitely limited suboval
yellowish spot below, near the tip, extending two-fifths the length of the femur on
front pair, smaller on middle pair, and still shorter and less definite on posterior
pair.
Larva greenish yellow in color. Average length, 6 mm. ; otherwise of same pro-
portions and structure as in spring form.«
Pupa, average length, 5 mm. Except in larger size and ample wingpads undis-
tinguishable from that of the spring form, minutum.
Egg of the ordinary ovoid form with pedicel about twice as long as the bulbous
part. The apical end is furnished with a distinct hook, perhaps for the purpose of
holding the egg in place while the ovipositor is being withdrawn from the plant.
ADULTS OF SPRING FORM.
(. Isosoma minutum.)
Length of body, 2.8 mm.; expanse of wings, 4 mm.; greatest width of front wing,
0.7 mm.; antennae, subclavate, three-fourths the length of thorax; whole body
(with exception of metanotum, which is finely punctulate) highly polished and
sparsely covered with long hairs toward the end of abdomen; abdomen longer than
thorax and stouter. Color, pitchy black; scape of antennae, occasionally a small
patch on the cheek, mesoscutum, femoro-tibial articulations, coxae above and tarsi
(except last joint) tawny; pronotal spot large, oval, and pale yellowish in color;
wing veins dusky yellow and extending to beyond middle of wing; submarginal
three times as long as marginal; postmarginal very slightly shorter than marginal,
and stigmal also shorter than marginal. (See Riley, Am. Nat., 1882, p. 247.)
Larva, length, 4.5 mm.; of the shape indicated in fig. 3; color pale yellow; mouth
parts brownish. Antennae appearing as short two- jointed tubercles. Mandibles
with two teeth. Venter furnished with a double longitudinal row of stout bristles,
a pair to each joint. Each joint bears also, laterally, a short bristle. Stigma pale,
circular; ten pairs, one on each of joints 2 (mesothoracic) to 11.
Pupa, jet black without other coloring; smaller than that of summer form. That
is to say, the pupse wintering over in the straw and from which the spring form
develops is thus to be described; that following the larva} developing in spring is
understood to belong to the summer form.
a Riley, Ann. Rept. U. S. Dept. Agr., 1884, p. 58.
22
NATURAL ENEMIES.
Probably the most efficient enemy of this species is a small, slender,
four-winged fly, of somewhat brilliant metallic-colored body and yel-
low legs. This has a very slight resemblance to an Isosoma, and,
indeed, was described as Isosomct allynii , now known as Eupelmus
ally nil French. A somewhat similar insect with metallic body and
yellow abdomen, Stictonotus isosomatis Riley, is very efficient in destroy-
ing the larvae in the straw. Homoporus (, Semiotellus ) chalcidephagus
Walsh and bevond a doubt other chalcids are also instrumental in hold-
ing it in check. These parasites are all the more
efficient as they are double-brooded also, developing
in late summer and at once ovipositing in other larvae.
There is also an egg parasite that I have reared in
connection with Isosoma, but not with certainty from
this species. This is Oligosita americana Ashmead
MS. As in all cases where I have obtained this there
were species involved other than the one under con-
sideration, it is obviously impossible to say that it
destroys the eggs of this species, but with such regu-
larity does it occur in connection with Isosoma in
general that no doubt it preys upon this one with the
others. When the wheat is harvested the straw is
frequently, and, in fact, almost invariably, cut off
between joints, thus leaving the larvas, if there are
such in the straws at that point, exposed to attack
from predaceous insects. The larvae of a small, slender, black and
yellow carabid beetle ( Leptotrachelus dorsalis Fab.) crawls up,
descends into the stubble and devours the Isosoma larvae, but unfor-
tunately its taste seems to be too obtuse to allow it to coniine itself
strictly to Isosoma, and as a consequence it devours parasites as well
as host. The mite Pediouloides ( Heteropus ) ventricosus (fig. 7) is also
an enemy, gaining access to the larvae precisely as with the beetle
larvae previously mentioned.
PREVENTIVE AND REMEDIAL MEASURES.
The fact of the spring brood being almost entirely wingless and
therefore unable to fly from field to field places it almost totally at the
mercy of the farmer, as he has but to change his crop from one field
to another to rid himself of its presence. It is true the summer form
can fly about from field to field at will, and it does so, but if the spring
brood of adults are left helpless in a field with no wheat plants in which
to place their eggs, it will be seen at once that there can be no sum-
mer brood emanating from this source. Rotation of crop will as a
consequence be sufficient to prevent an overabundance of this species.
But there are conditions under which this is not practicable, as in some
Fig. 7. — Pediculoides
ventricosus Newp., a
mite which destroys
the larva — much
enlarged ( after Mar-
latt).
23
sections and with some farms tne soil is but little fitted for other crops,
and where wheat follows wheat year after year for an indefinite period.
Under such conditions, burning’ the stubble before preparing the
ground for the new crop in fall will prove effective. If this burning
is delayed until September, many of the parasites will have developed
and escaped. The burning can be best carried out by cutting the grain
as high as possible, leaving the stubble long. A few days before
burning a mower should be run over the field, cutting off all grass and
weeds, which, when dried, will add to the fuel supplied by the stubble.
Taking advantage of a favorable wind, the farmer can burn over his
field cleanly, thereby not only ridding it of the presence of this pest,
but also the Hessian fly, besides burning up much of the seed of foul
weeds and grasses.
DISTRIBUTION.
This species seems to occur throughout the middle belt of country
from the Atlantic to the Pacific, wherever wheat is grown as a staple
crop. Whether it is single-brooded in the North and is, therefore, in
such countries capable of sustaining itself in spring wheat, is not yet
known. Having no other known food plant than wheat, it will neces-
sarily follow that its range will be restricted to areas of wheat culti-
vation, and being double brooded, requires fall wheat in which to
develop. The fact of its having been so long confused with what now
seems the true joint-worm fly ( Isosoma tritici Fitch) renders its actual
distribution, as well as the extent of its ravages in the past, somewhat
obscure. I found the summer form {grande) in considerable numbers
in spring wheat at Lafayette, Ind., June 19, 1895, and it is likel}r that
it can breed therein, though fall wheat is necessarv for form minutum.
THE JOINT-WORM.
( Isosoma tritici Fitch. Figs. 8 and 9.)
I have previously referred to the confusion of Isosoma tritici Fitch
with I. liordei Harris, and which was so persistently insisted upon by
Walsh and Riley. It was not until 1896 that Dr. Howard succeeded in
establishing the fact that this is a valid species, and now we are con-
fronted with a long series of complications that can only be safely
corrected by carefully rearing both species and studying them anew.
Failing entirely in securing sufficient material from wheat in carrying
out the investigations upon which this bulletin is based, I feel now
very much like letting the insect alone until an opportunity is offered
to untangle the knotted skein. Doctor Fitch stated distinctly that the
term “joint-worm*' was to be applied to the insect attacking wheat,
and it was because of the mistake of considering it the same insect as
that described by Harris that the name “joint-worm” came to be
applied to I. Jiordei at all; a mistake that belongs neither to Harris
nor Fitch, but one that has misled nearly everybody.
24
PREVIOUS RECORD OF THE INSECT.
About the year 1848, in central Virginia, throughout the country
adjacent to Charlottesville, Albemarle County, and Gordonsville,
Orange County, the wheat began to sutler seriously from attack of
what was at that time called the joint- worm. In 1851 the wheat in
Albemarle County was, much of it, not worth the harvesting. In
1854 the ravages of the pest had become so serious that a u joint- worm
convention v was held in Warren ton to devise means for controlling it
and preventing, if possible, its further ravages, as by this time it had
become almost impossible to raise wheat at all in the infested terri-
tory. The action of this convention was to recommend a better s}^s-
tem of cultivation, the use of guano and other fertilizers to promote
the rapid growth and early ripening of the grain, and the burning of
the stubble after harvest.
Fig. 8. — Isosoma tritici Fitch: adult of the joint- worm, much enlarged (from Howard).
Looking back to this period, our later-day entomologists can hardly
understand how there should have been any difficulty in determining
beyond a possible doubt the author of all of this destruction. Doctor
Fitch, who, it seems, received some of the growing wheat plants
infested with the larvte from that locality, always insisted that he found
a cecidonr\rian larvae inhabiting cells like those occupied by the joint-
worm and that these were the true depredator, and, though he continued
to stoutly defend his determination, we. have yet to discover a Cecido-
myia either causing or inhabiting such a cell or gall in the wheat plant.
From all that has been since learned relative to these insects it is clear
that the ravages were those of this species, with, perhaps, individuals
of the preceding species intermixed among them. As a matter of
history it may be stated that Doctor Fitch was still unconvinced that
the joint-worm, and not a dipterous insect, was responsible for the dam-
25
age in Virginia as so late as 1859 lie expressed astonishment that he was
unable to rear any Hessian Hies from
the same straw from which he reared
the joint- worm. Surely the unento-
mological farmer might be pardoned
for falling into the same error until,
at least, he is placed in possession of
some way of distinguishing them from
each other.
After finding out bejmnd question
that this is a valid species, that it is the
true joint-worm fly attacking wheat
and not barley, while Isosoma hordei
attacks barley and not wheat, notwith-
standing the effect on the straw is much
the same, and that though it resembles
Isosoma grande rather closely, it is
quite different in habits and life his-
tory, we are forced to conclude that
we really know very little about it. 1
have reared it in limited numbers from
wheat straw in Illinois, Indiana, and
Ohio, though it would appear that
about 1885 it became excessively abun-
dant in some parts of Michigan, and,
in fact, I am not sure but that I have
n^self found the larvae in some abun-
dance, but supposed them to belong to
the preceding species. The uncer-
tainty in regard to the identity of these
larvae was owing to the fact that at the
time they were observed this was not
considered a valid species, and I at that
time considered them as belonging to
Isosoma grande , but now doubt my
former opinion from the fact that this
species does not always form galls
either in wheat or Etymus, that there
were several larvae between the joints
instead of one, and that they were
located just under the inner walls of
the straw, but not forming a cell,
whereas those of the species last con-
sidered is found only in the center of
the straw, in the more solid sub-
Stance, immediately above the joint (drawn in Division of Entomology) .
26
itself. In 1885 Professor Cook described Isosoma nigrum , which he
states was reared from larvae forming creases and hardened deformities
in the straw. Professor Cook's specimens, sent to Washington, have
been determined by Doctor Howard as Isosoma Iritici Fitch. a (See
also Walsh, Trans. 111. St. Agl. Soc., vol. 5, pp. 185-190, tigs.)
LIFE HISTORY.
The larvae pass the winter in the straw, if in wheat, and in the stems
of Virginia rye grass ( Elymus virginicus) in the East, and E. glaucus
and another grass, either Bromus ciliatus or a species of Agropyron,
in California.
In the Middle West the adults appear the latter part of May and
early dune. The egg does not differ materially from that of I. grande ,
and it is probable that the method of oviposition is much the same as
in that species, the female placing her eggs in the }Toung growing
wheat plant just abos^e the uppermost joint to which she can secure
access at the time. Ordinarily the upper joint is not yet uncovered,
except in case of very early wheat, and in that which has made less
advance even the second joint from the head is so covered with the
sheaths that the insect is unable to determine its position, so that
sometimes we find more larvae between the second and third joints
than we do farther up between the first and second, precisely as with
I. grande. The larvae reach their full growth by harvest, but do not
pupate until the following spring.
All adults are winged, and both sexes are represented. Outside the
wheat field I have reared the insect only from Elymus virginicus , and
I question its breeding in the stems of cheat (. Bromus secalinus ) for
the reason that I have reared it from the rye grass and not from the
cheat, though both were abundant in the same locality. Mr. Koebele,
who reared it from Elymus glaucus in California, was uncertain
whether he also reared it from Bromus ciliatus or Agropyron. Both
the Bromus mentioned by Koebele and Agropyron repens occur in the
East, and it is very probable that future studies of the species will
show that there are other grasses besides rye grass that will require
attention from the farmer who wishes to guard against its appearance
in his fields by preventing its breeding permanently along roadsides
and the borders of his fields.
DISTRIBUTION.
Doctor Fitch received this insect from Maryland, Doctor Lintner and
Professor Comstock reared it in New York, the United States Depart-
ment of Agriculture has it from Virginia and North Carolina, Pro-
fessor Cook reared it in Michigan, I have reared it in Ohio and Illinois
a Grass and Joint- worm Flies and their Allies, Tech. Ser. 2, Div. EnL, U. S.
Dept. Agr., p. 18.
27
and found it in Indiana, Doctor Fletcher has reared it in Ontario,
Canada, and Mr. Koebele in California, and there is hardly a doubt that
investigations will reveal its presence throughout the entire wheat-
growing region of North America. Being fully winged and single
brooded, as well as capable of breeding in abundance outside of the
grain tields, there seems no good reason why it should not cover the
whole country, attacking either spring or winter wheat.
DESCRIPTION.
11 Female. — Length 4 mm.; expanse 7.6 mm. Head, pronotum, ana mesonotum
strongly rugulose but not umbilicate-punctate except toward tip of scutellum, where
an occasional umbilicate puncture occurs; metanotum also strongly rugulose, with a
faint trace anteriorly of a median longitudinal furrow; metanotal spiracles large and
perfectly circular; pronotal spots moderately large and often faint, but plainly dis-
cernible from above, sometimes, however, quite bright and distinct. Abdomen
longer than thorax, nearly as long as head and thorax together; abdominal segments
4 and 5 together longer than 2r 3 only about half as long as 4, and 5 as long as two
preceding united; first funicle joint one-half longer than second; club longer than
three preceding funicle joints together. Body slightly but plainly pilose except at
sides of metanotum, where the fimbria is very obvious. Legs black except at joints,
which, with the tarsi, are yellow. Claw of stigmal club given off before the tip.
Male. — Length, 2.9 mm.; expanse, 6 mm. Petiole shorter than hind coxae, faintly
punctate; flagellum of antennae uniformly pilose, joints well rounded above, not
strongly pedicellate; joint 1 three times as long as wide and nearly three times as
long as pedicel; none of the funicle joints constricted in the middle; joints 2 and 3 each
nearly as long as 1; joints 4 and 5 each a little shorter; club plainly divided by a
distinct incision into two joints, but the terminal ovate joint is not pedicellate.”
Howard, Tech. Ser. 2, Div. Ent., LT. S. Dep. Agr., pp. 17, 18.
Originally described by Fitch, Jour. N. Y. State Agr. Soc., 1859,
p. 115. Cited as Isosoma hordei b}T Walsh, Amer. Ent. and Bot., II,
p. 332. Described as Decatoma basilaris by Provancher, Faun. Ent.
Can., II, p. 569.
NATURAL ENEMIES.
%
The natural enemies are, with few exceptions, probably the same as
with the preceding species, to which this is more closely related than with
the one that follows, at least so far as its life history is concerned. In
my own rearings I have invariably bred this in connection with I.
grande if from wheat straw, or with 1. elymi if from grass, so that
personally I am not able to say that certain parasites actually came
from I. tritici , though there is no reason for doubting that such was
the case. Certain parasites do most certainly confine themselves to
particular species of Isosoma. Websterellms tritici Ashm. has only
been reared from this species, as it is now known. An undescribed
Isosoma occurs in considerable abundance in the stems of Tricuspis
seslerioides , and from this I have reared a parasite belonging to the
genus Torymus, but strangely enough this parasite has only been
28
reared from this particular Isosoma, even where the grass infested by
its particular host was growing in the midst of Elymus, literally alive
with the larvae of three other species of Isosoma. Thus, while some
parasites attack all of the species, there are evidently others that
restrict themselves to one.
REMEDIAL AND PREVENTIVE MEASURES.
Owing to its possessing wings whereby it is capable of flying readily
from one held to another, or breeding in the stems of grasses in the
intervening territory, a rotation of crop will be less effective in the
case of this species than with the preceding. For the same reason,
careful attention to roadsides, borders of fields, and ditches becomes all
the more imperative. The burning over of the stubble fields before
preparing the ground for wheat again in the fall, or the same treatment
of the uncultivated areas above mentioned at any time during winter
or early spring will effectually exterminate these insects where these
measures are carried out. In the Middle West wheat seldom follows
wheat on the same ground for a series of years, the grain being rotated
with red clover, which prevents the burning over of the stubble fields
in the fall, but does not in any way affect the treatment of grass lands,
and if the crop is rotated annually and the borders and waste places
attended to there is little likelihood of the farmer suffering greatly
from the depredations of this insect. I have invariably found the
most serious injuries to occur on thin or poorly fertilized soils or
where the land had not been thoroughly prepared before seeding.
Probably whatever tends to produce a healthy, vigorous growth of
the wheat plant will tend to discourage oviposition by the insect. It
is not known that the insect prefers one variety of wheat to another,
but the variety with the stoutest straw will probabl}" suffer least from
attack.
■
DIFFICULTY IN RECOGNIZING THE SPECIES.
I have made no attempt to describe the larva and pupa in their proper
place, because I do not believe they can be separated by any descrip-
tion from those of the preceding species if in wheat, or those of Isosoma
elyrni French if in grass. Notwithstanding this the farmer can readily
separate them at the proper season of the year, even if both are present
in his cultivated fields. After October this species will be in the form
of a yellowish white larva in the stubble, while the preceding species
will be in the form of a black pupa, both perhaps in the center of the
stubble. In spring the larvae of this species will change to a jet black
pupa, while those of I. grande will have developed and escaped. So,
then, pupae found in the fall will probably belong to the preceding
species; those found in spring, if in wheat, to this, and larvae found
after October, if in wheat stubble, also to this species. However,
29
too much reliance must not be placed on these distinctions, as there are
other supposed species of these insects attacking wheat of whose larvae
and pupae we know nothing, but with our present knowledge the facts
just given are the best that can now be offered the farmer in order to
enable him to separate the different main enemies of his grain and
receive whatever practical benefit is possible from what information is
now available, leaving future studies to throw more light upon his
problems. The adults can be easily separated from those of the pre-
ceding species b}^ their smaller size, and from the next by their smaller
size and the color of the legs, which in I. hordei are honey vellow.
The larvae are also smaller than those of the following species and may
or may not cause galls and deformities in the straw. The adults of the
summer form of the preceding and those of the following species are
abroad at the same time as are those of this species during the last
days of May and early June.
While fig. 9 illustrates the effect of the larvae on a wheat plant, there
are so many variations from this that it is at present impossible to
separate these two gall-forming species by their effect on the straw.
THE BARLEY STRAW-WORM.
( Isosoma hordei Harris. Fig. 10. )
Up to 1896 this species was confused with the preceding and the
term “joint-worm ” applied thereto. The fact is, Harris seems not to
have given this name to his species at all, but on the other hand Doc-
tor Fitch applied it to his I tritici , and it was owing to the confusion
of these two insects that the name became misapplied, and 1 have here
given Harris’s species the name “barley straw-worm,” in accordance
with the name hordei.
PREVIOUS RECORDS OF THE INSECT.
Of all of our described species of Isosoma this was the earliest
known and was for many years supposed to be the only species infest-
ing cultivated grains or, in fact, inhabiting this country, as it was con-
sidered a parasite on the real depredator, presumed to be some kind
of a two-winged fly, and was actually described by Dr. W. T. Harris
in 1830 as a parasite, under the name Ichneumon hordei. a Doctor
Har ris certainly seems to have been aware of the fact that as early
as 1821 Mr. James Worth, of Sharon, Bucks County, Pa., found
larvae clearly belonging' to some species of Isosoma affecting the culms
of wheat “near the root, where they caused enlargements of the
stem;”* 6 and in 1823, Mr. Joseph E. Muse, of Cambridge (Eastern
Shore), Md., reared an insect, also from wheat, which he termed a
a New England Farmer, July 23, 1830; Ins. Mass., 1841, pp. 434-437,
& American Farmer, vol. 4, p. 394.
30
“TenthredoA whose larvae, as he stated, “ burrow within the stems
and feed upon them.“rt Doctor Harris, in the edition of 18dl of his
Insects of Massachusetts, page 431, refers to the statement of Dr.
Andrew Nichols, of Danvers, who stated that worms found in his
barley straw were about one-tenth of an inch in length and of a ye\-
low or straw color, and that in the month of November they appeared
to have passed into the chrysalis state, but living through winter
unchanged in the straw. The insects referred to by Mr. Worth, of
Pennsylvania, and Mr. Muse, of Maryland, might quite probably have
been Isosomct tritici Fitch, but if the one referred to by Doctor Nichols
was an Isosoma at all it was certainly I. grande , as that is the only
species attacking grain that is known to pupate in the fall. Thus it
will be seen that it is not easy to determine just what Harris might have
included as belonging to his I. liordei , though he nowhere states that it
was ever obtained from
any other than barley
straw; hence the name,
liordei , applied to it. It
is interesting to know
that specimens labeled in
his handwriting a Para-
sitic in barley, June 15,
1830,'’ are still in the
museum of the Boston
Society of Natural His-
tory, so that there can
be no mistake in the
identity of the insect
described. Even in the
edition of his Insects of
Massachusetts, of 1841, Harris makes no mention of his species having
been found affecting wheat. In the edition of 1852 he relates that
about eight years before children sleeping on straw beds in Cam-
bridge, Mass., had been bitten by these insects and the annovance had
been so great that the beds, both straw and ticks, had been burned.
Now people do not use barley straw for such domestic purposes, nor
in fact do they use wheat straw as a rule, but oat straw. As Doctor
Harris does not enlighten us as to what kind of straw it was from
which the insects annoying the children came, we still have no direct
proof that this species was ever known in connection with wheat straw.
About 1852 there appeared a similar trouble in the barley in cen-
tral New York, and though Doctor Fitch described it as a distinct
species under the name JEurytoma fulvipes? we now know that it was
« Loc. cit., vol. 5, p. 113.
& Jour. X. Y. Agricultural Soc., Yol. IX, p. 115.
Fig. 10. — Isosoma hordei Harris: adult of the barley straw-worm
(from Howard).
31
Isosoma hordei. This last outbreak in central New York appears to
have been rather widespread and disastrous, for in 1858 Hon. George
Geddes, president of the State Agricultural Society, stated that while
formerly a yield of 10 bushels of barley to the acre was expected, they
could not at that time rely upon more than 20, and unless relief came
barley growing, on account of the attack of this pest, would have to
be abandoned.77
There was a local outbreak of this species in Ontario, Canada, in
1867-68, and observed at AVakeman, Chagrin Falls, and Barry, Ohio;
Indiantown, Cuckoo, and Paynes, Va. ; Albany, N. Y. ; Canada West
(William Coupe r); Ottawa, Canada; and Urbana, Carbondale, and
Marshall, 111. So far it has not been reported from the Pacific coast
States. Doctor Fitch confined this species to the insect reared by
Harris in Massachusetts, and the one working the injuries in central
New York as Isosoma fulvijpes , both of which are now known to
belong to Isosoma hordei.
CD
LIFE HISTORY
The species is single brooded. The adults of both sexes, all fully
winged, emerge from the straw and grass in late May and earl}- June,
ovipositing almost immediately. The effect of the larvae on the grow-
ing plants begins to show within a short time, and. though the larvae
become full grown during June and early July, they remain in this
condition within their cells until May of the following year.
EFFECT OF THE LARV 2E OX THE PLAXT.
The eggs may be deposited in the stem of barley or grass aiprwhere
between the root and the head, even among the lower spikelets of the
head. The effect of the larvae may be to cause hard, woody cells,
whose outline is indicated only by slight discolorations, the outer sur-
face of the stem being smooth and not in the least swollen, the cell
being entirely within the walls of the stem, causing no distortion in
the straw; or there may be anywhere from one to a dozen galls in a
cluster, and these may be either clearly defined or so packed together
and cramped as to lose all semblance to the typical galls and take on
the appearance of diminutive growths, resembling the black knot of
the cherry and plum. The straw or grass stem may be enlarged to
two or three times its natural size, forming an elongated oval woody
growth that pushes its way outward, bursting, as it were, the sheath
at base, and showing between the edges. This growth is usually on
one side of the stem, just above the joint, and is marked with inter-
lacing creases and furrows indicating the outlines of each individual
cell, and in many cases sending downward from the lower extremity
small root-like appendages, the use or cause of which it is difficult
a Trans. X. Y. Agl. Soc., 1859, p. 332.
32
to understand. All of these malformations as well as others may
be found in the stems of Elymus canadensis in abundance, from
which swarms of the adults will emerge in late May and earl y June.
Owing to the woody nature of these abnormal growths, straw attacked
by this species is more likely to be broken up into small bits, and
these go in with the grain at thrashing, thereby increasing the dan-
ger of transportation from one locality to another, but to offset that,
as it were, there is likely to be a greater proportion of the insects
left in the stubble than with the other species, as the affected straws
are usually more stunted in growth and shorter. At present there is
no other insect attacking wheat, rye, or barley that causes similar
growths in the straw except Isosoma tritici Fitch, in wheat, and the
farmer can hardly mistake the work of these two pests for those of
any other in his fields.
DESCRIPTION.
“ Female. — Length, 3.6 mm. ; expanse, 6 mm. Eronotum and mesonotum minutely
hut strongly rugulose, smoother than I. tritici ; metanotum more coarsely rugulose,
the larger elevations taking a longitudinal direction, no central furrow or carina;
pronotal spot very small, not visible from above. Abdomen as long as head and
thorax together; joints 4, 6, and 7 subequal in length, the fifth a little longer; joint
3 a little longer than 4, 2 hardly longer than 3 and 4 united; funicle joints 2 to 5 sub-
moniliform, but still a little longer than broad. All legs (except coxge) and antennae
honey-yellow, flagellum and femora a little darker; claw of stigmal club straight,
given off well before tip of club; pilosity sparse.
“Male. — The only males which I have seen are the two from the Harris collection
These are both in very bad condition; neither had an abdomen and one has no
antennae. With the other, but three funicle joints remain on the left antenna (the
others being broken off) and four on the right, but the latter are still inclosed in the
pupal sheath. The three funicle joints remaining on the left antenna are not pedi-
cellate, very slightly arched above, and furnished with close, moderately short hair
not arranged in whorls; joint 1 longest, 2 and 3 successively decreasing. Joint 4 is
still shorter, judging from the sheathed right antenna.” (Howard, Tech. Ser. 2,
Div. Ent., LT. S. Dept. Agr., pp. 18, 19.)
The foregoing description was drawn up from specimens in the
Fitch collection, labeled, in Fitch’s handwriting, 44 Eurytoma fulvipes
Fh. other specimens from the Harris collection, reared from barle}7,
June 15, 1830; other specimens from 44 Canada West,” and still others
reared by myself from stems of Elymus canadensis growing near
Champaign, 111. This is the Ichneumon hordei described by Harris
in the New England Farmer, the Eurytoma fulvipes described by
Fitch in his seventh report, and the Isosomci liordei mentioned b}r
Walsh in the American Entomologist (Vol. II, p. 330).
The larva, except from its larger size and habit of living within a
cell, is not distinguishable from that of the other species of grain-
infesting Isosoma. It is little larger than that of I. grande , found m
May and early June, and it has the universal yellowish-white color.
The same may be said of the pupa.
33
NATURAL ENEMIES.
The larvae appear to suffer more from the inroads of natural enemies
than do those of other species of these insects, perhaps because of
their inhabiting the walls instead of the center of the straws, thereby
rendering* them more accessible. It may be that this is the older form,
and a greater number of the parasitic species have become adapted to
it as a host insect. There is little doubt that Oligosita americana
Ashm. and Polyneura citripes Ashrn. both attack and destroy the
eggs, as I have reared them in numbers from stems of Elymus inhab-
ited by the larvae, and also the stems of other grasses inhabited by
other Isosoma larvae. Eujpelmus cdlynii French, easily known by its
slender body, metallic color, with yellow legs, is associated with this
as it is with nearly all other species of these insects that inhabit the
stems of grain and grass. Merisus isosomatis Riley, conspicuous for
its yellow body, is almost as abundant as the preceding, and, as the
name implies, is parasitic on other species also. Ilomojporus chalci-
dephagus Walsh is also a parasite, but I have reared it in lesser num-
bers than the other two, in Illinois, Indiana, and Ohio. Almost the
first parasitic species that I reared in connection with the present
studies of Isosoma hordei was a second new genus and species, Para-
pteromalus isosomatis Ashmead MS. I have myself witnessed the
oviposition of all of these parasitic species, and their life history is
probably practically the same. The adults emerge in spring a little
later than those of the Isosoma, but there is a second generation of
adults in summer, and it is these that I have observed placing their
eggs in the cells of I hordei , thus doubling their effectiveness in hold-
ing it in restraint and preventing more frequent and greater devasta-
tions in the grain fields of the farmer. While carrying on the present
investigation I have reared an undetermined Eurytoma, a parasite on
Isosoma, but as I reared four species of the latter from the same lot
of stems, it is impossible to say to what extent it preys upon the one
now under consideration, nor do I know anything in connection with
its habits, except that it makes its appearance in spring, simultaneously
with other parasites.
PREVENTIVE MEASURES.
The preventive measures might well be summed up under the
caption of good farming, for there is not one practical measure but
will pay for its carrying out, aside from its entomological influ-
ences. As the adults are fully winged and can fly freely from one
field to another, less must be expected from a rotation of crop, but
even under these conditions, a certain amount of benefit will result
from a careful sy stem of crop rotation. Wheat, rye, or barley should
never be grown on the same land for more than two years in succes-
sion without carefully burning over the stubble before preparing the
7327— No. 42—03 3
34
ground for another seeding. To these must be added the mowing off
of roadsides and along fences and margins of fields during late June
or early July, or the burning over of these during winter or early
spring, thus destroying the hibernating larvae. The rye grass along
the margins of fields and ditches should receive special attention in the
matter of mowing and burning. It is not known whether or not any-
thing is to be gained by early sowing, which, besides, is apt to invite
the attack of Hessian fly.
THE CAPTIVE ISOSOMA.
(Isosoma captivum Howard. Fig. 11.)
Very little is known of the habits and transformations of this species.
I found it in a field of growing rye near Normal, 111. , May 10, 1884,
and swept it from timothy and bluegrass about Lafayette, Ind., during
May, 1885, and again during the same month in 1886. Dr. J. A.
Lintner reared both sexes from wheat straw sent him from Johnsons
Creek, Niagara County, N. Y., in December, 1887, the adults appear -
Fig. 11. — Isosoma captivum How.: adult (from Howard).
ing in March of the following year, the straw having, presumably,
been kept indoors during the winter. a Probably the adults occur
normally at about the same time as those of Isosoma Jiordei , tritici ,
and elymi. We know that it attacks wheat, probably rye, and perhaps
barley.
DESCRIPTION.
“Female. —Length, 3.4 mm.; expanse, 5.8 mm. Head and mesonotum uniformly,
finely, and closely rugulose, not shagreened; metanotum more coarsely rugulose and
with a narrow and shallow central longitudinal groove, which widens slightly pos-
teriorly; pronotal spot plain, moderately large; hind coxse delicately punctate.
« Fourth Report, State Entomologist of New York, p. 34.
35
Abdomen shiny, as long as thorax, oblong-ovoid; the second segment occupying
nearly one-third the whole surface; segments 4 to 6 subequal, the third a little
shorter; funicle joints 2 to 5 subequal; club nearly as long as three preceding joints;
joint 1 one-half longer than 2; pile sparse and short, more marked at metanotal fim-
bria and terminal joints of abdomen than elsewhere. Color uniform black, except
for pronotal spot, tarsi, middle and hind femoro-tibial knees, front tibse and apical
third of front femora, which are light honey yellow. Stigmal club about as in I.
hageni and 1. agrosiidis, except that its tip is more rounded instead of squarely truncate.
11 Male. — Length, 2.5 mm.; expanse, 5 mm. Punctation rather finer than with
female; petiole as long as first abdominal joint, strongly rugose; flagellum of anten-
nae long; pedicel not globose, slightly elongate; joint 1 of funicle longest, twice as
long as pedicel; joints 2, 3, 4, and 5 each a little shorter than its preceding joint;
not so strongly pedicellate as with I. californicum and I. bromi, moderately arched
above with hairs arranged in two indefinite whorls; club separated into two subequal
pedicellate joints, giving the funicle the appearance of being 6-jointed instead of
5-jointed, as with bromi and californicum ; scape short, about as long as pedicel and
first funicle joint together; strongly expanded below tip. Coloration like that of
the female.” (Howard, Tech. Ser. 2, Div. Ent., U. S. Dept. Agr., pp. 13, 14, 1896.)
The earlier stages of development are unknown, but the}^ probably
differ little from those of allied species. Quite likely the same natural
enemies prey upon it and the same repressive measure will apply to it
as with the preceding species.
WEBSTER’S ISOSOMA.
( Isosoma websteri Howard. Fig. 12.)
This is in all probability a wheat-infesting species, as I found it in
a wheat field near Bloomington, 111., May 9 and 11, 1884, and about
Lafayette, Ind., also in fields of wheat, June 2 and 16, 1885. I also
Fig. 12. — Isosoma websteri: adult female — much enlarged (from Howard).
reared it from a pupa taken from a growing wheat plant in the
Bloomington, 111., field May 29, but have not encountered it since
in my studies of these insects. Nothing is known of its life history
36
except what I have just given. Its close resemblance to I. maculatum ,
which I have reared from stems of cheat from the vicinity of Cham-
paign and Urbana, 111., is quite suggestive, the adults of this last
species being abroad during late May and early June in the same
localities.
DESCRIPTION.
‘ ‘ Female. — Length, 3.4 mm.; expanse 6.3 mm. Head, pronotum and mesonotum
as with I. maculatum; metanotmn with only the beginning of a central furrow, its
lateral carinae immediately curving around the sides, each inclosing an oval, flat-
tened, nearly smooth portion of the metascutellum ; a median carina extending
nearly to the tip of the sclerite; pronotal spot moderately large and plainly seen
from above, occupying a little more than one-third of the dorsal aspect of the pro-
notal foreborder. Abdomen much longer than the thorax ; segments 3 to 5 increasing
in length; 6 and 7 as long as 5. Antennae with joint 1 of the funicle twice as long
as 2; joints 3, 4, and 5 gradually decreasing in length, subequal in width; joint 5
more closely connected with club than with the preceding joint. Color and wing
venation as with I. maculatum .” (Howard, Tech. Ser. 2, Div. Ent., IT. S. Dept.
Agr., pp. 15, 16, 1896.)
While, as stated, this is probably a wheat-infesting species, it is to
be remembered that it has been reared only in a single instance, and
it is within the range of possibility that my growing wheat plant, as I
supposed, might possibly have been cheat, as it is easy to confuse the
young plants^ and as the two grow everywhere intermixed in the
fields mere collecting offers no solution of the problem whatever. Of
the four species of Isosoma which I have reared from common cheat
( Bromus secalinus ), viz, I. elymi , I. albomaculata , I. lvirtifrons , and
I. maculatum , none were found in the wheat straws growing in the
same field.
Should the species become numerous enough to cause serious depre-
dation it will probably yield to the same repressive measures as the
other grain-attacking forms.
THE HAIRY-FACED ISOSOMA.
(Isosoma hirtifrons Howard. Fig. 13.)
The type specimens of this species were reared from rye straws
collected by Mr. Coquillett, in Mercer County, Cal., in 1885. It was
reared by myself from stems of common cheat growing in a wheat
field near Urbana, 111., in 1902. I know nothing whatever of its life
history except that it appeared in my breeding cages in common with
the other cheat-infesting species. The records of the Illinois State
Laboratory of Natural History and those of the office of the State
entomologist contain numerous references to Isosoma attacking rye.
37
Specimens of the affected straws show that a part of this injury was
due to Isosoma tritici , whose presence could be detected by the larval
cells in the walls of the straw; also many straws were attacked by a
noncell-making species, the larvae being in the center of the stems
immediately above the joint. No adults were reared, as the larvae
were supposed to be those of the old Isosoma tritici Riley, which is
not now known to attack any grain except wheat. It is therefore
impossible to say which of the species whose larvae live in the cen-
ter of the stem it was that did the injury in these cases. I made
everv effort to secure material from the fields of rye about Urbana
and Champaign, 111., during the summer of 1902, but was unable to
find any infested straw, and therefore can throw no light upon the
identity of the rye-attacking species; but the fact that the one under
consideration is known to affect rye in California would place it under
Fig. 13. — Isosoma liirtifrons How.: adult female, much enlarged (after Howard).
suspicion wherever it occurs in the eastern States. I judge that it
will be very easily confused with other species, and the fact of its
infesting cheat would lead to the suspicion that it will be found infest-
ing other grasses.
DESCRIPTION.
“ Female . — Length, 3.7 mm.; expanse, 7 mm. Sculpturing of head, pronotum, and
mesonotum as in I. websteri , except that there are sparse, large, shallow punctures on
the mesoscutellum; cheeks much fuller than in other species; metanotum as with I.
mciculatum. Abdomen about as long as thorax; segments 3 to 6 increasing in length.
Antennae stout, moderately long, very hairy; proportions about as in I. websteri . Body
not unusually pilose, except face, which is closely covered with short white pile; pro-
notal spots very plain, but not large, occupying about one-third of the dorsal aspect
of the fore-border of the pronotum. Color black, except for all femoro-tibial knees
and pronotal spot. Claw of stigmal club given off some distance from tip, delicate
and short.” (Howard, Tech. Ser. 2, Div. Ent., U. S. Dept. Agr., p. 16, 1896.)
88
Up to the present time cheat has been looked upon only as an
undesirable plant growing1 among wheat like weeds among corn, but
it now appears to be doubly undesirable on account of its harboring
insect enemies of cultivated grains.
ISOSOMA SECALE Fitch.
This was described b y Doctor Fitch in 1861, after he had become fully
convinced that these insects were not parasitic but the true depredators
among grain. a I have not myself encountered it in the study of grain
insects, but from the statements of Doctor Fitch it does not seem to differ
in habits from Isosoma liordei and I. tritici , and one can not help sus-
pecting that a careful study of its life history and development will
show that it is one of these species. It was given the common name
of “rye fly,” and adults were reared from straws grown in 1860,
emerging about the 1st of June, 1861. The larvae were found to
occupy cells in the walls of the rye straw, and not in the base of the
sheaths, as was supposed to be the case with I. liordei , though Doctor
Fitch describes “the disease which the insect causes in the rye being
in every particular like that in barley and wheat.” As we now know,
barle}r and wheat are attacked by two different species, but all three
seem to have precisely the same life history, so that whether there be
one species or more, the farmer will be able to meet it or them with
the same preventive measures.
DESCRIPTION.
“Female. — Length, 3.6 mm.; expanse, 6.6 mm. Punctation as with I. liordei; pro-
notal spot large, plainly seen from above. Abdomen as long as head and thorax;
segments 4 and 5 subequal; 6 and 7 together shorter than 5; 2 much longer than 4
and 5 together. Color black; scape and legs black; front tibke, knees, and tips of
middle and hind tibiae and all tarsi honey yellow; claw of stigmal club given off near
tip of club, somewhat curved; antennae as in I. liordei.
“Male. — Length, 3 mm.; expanse, 5 mm. Specimen in poor condition. Expansion
of scape more abrupt from tip than with other males described; funicle joints well
arched above, scarcely pedicellate, each with 2 indefinite whorls of hair and with no
median constriction; each joint twice as long as wide; club plainly divided into two
joints, but no trace of pedicel to terminal joint, resembling I. liordei in this respect;
petiole a little shorter than hind coxae and shorter than first abdominal segment.”
(Howard, Tech. Ser. 2, Div. Ent., U. S. Dept. Agr., p. 19, 1896.)
In this connection it may not be out of place to state that I have
reared an undetermined species of Isosoma in connection with I hor-
dei from the stems of Ely m us canadensis , growing near Champaign,
111., and seeming to affect the grass much in the same manner as
« Seventh Report Noxious and other Insects of New York, pp. 849-851.
39
that species. It may on further study prove to have some connection
with the one now being discussed, though I have not found it attack-
ing rye.
FITCH’S ISOSOMA.
( Isoso m a fitchii H o ward . )
This is the last of the described Isosomas known to attack growing
grain, though 1 have reared what appears to be still another from
wheat straws from Carbondale, 111.; but the specimens are still
undetermined and nothing definite can now be said of them. This
species was described from 2 females and 1 male found in the Fitch
collection, labeled in Fitch's handwriting, “ Eurytoma hordei Harris,
Nos. 15223 and 15197." Nothing whatever is known of its habits,
but it was presumably reared, with some other species, from grain.
DESCRIPTION.
“ Female . — Length, 3 mm.; expanse, 5.8 mm. Head, pronotum, and mesonotum
faintly shagreened, nearly smooth, shining; mesoscutelluin with a few sparse punc-
tures; metanotum with a complete median longitudinal furrow emarginate on the
anterior half and with a central carina extending nearly to tip; very coarsely rugu-
lose either side of the furrow with a faint granulation between raised lines; pronotal
spot large, plainly seen from above, and two spots together occupying about one-
third of the dorsal aspect of the foreborder of the pronotum. Antennae with well-
separated joints; funicle joints 2, 3, 4, and 5 equal in length and width; joint 1 a
little longer; joint 5 as well separated from the club as from preceding joint; club a
little longer than 4 and 5 together, but of the same width. Abdomen as long as the
thorax; joint 4 shorter than 6; 5 longer than 6; 7 and 8 subequal. Color black,
except for pronotal spot and knees, which are luteous; claw of stigmal club given off
about at tip of club, straight.
“ Male. — Length, 2.2 mm.; expanse, 4.2 mm. Petiole about as long as hind coxge
and nearly equal in length to first abdominal segment. Antennae with funicle joints
very slightly arched above, each joint fully three times as long as wide, and slightly
constricted in the middle; otherwise as with I. liordei (Howard, Tech. Ser. 2,
Div. Ent., U. S. Dept. Agr., p. 20, 1896.)
I have now treated all of the species of these insects known to attack
cultivated grains in this country, though there may be still others as
yet unknown. These known species have been described in each case,
not especially for the benefit of the unentomological farmer but because
this publication will go to many lands and into the hands of many dif-
ferent peoples. Some will care nothing for descriptive matter, and
such can easily pass over it in the use of this bulletin, but there will
be others who will look to its pages for aid in determining with exact-
ness the identity of the species which they may have before them, and
for these descriptions are a necessity. Some of the species included
may appear to be of no especial interest to the practical farmer, but
of this no one can confidently predict. It may be true to-day and not
40
true to-morrow, for no one can tell what year or in what part of the
country any one of these, even the one that seems the most insignifi-
cant, may suddenly come to the front and commit serious depredations
over a considerable area. Besides this, the}^ are all of them so obscure
in appearance and their effect on the plants they attack so subtile and
hidden from the eyes of the farmer that he is unaware of his loss until
on threshing his grain he finds that it does not turn out well and the
kernels are light and shriveled. It is like the thefts of a trusted offi-
cial— they are not missed until, by accident, perhaps, the defalcations
are discovered, when we are struck with amazement at their magni-
tude and ask ourselves and each other how it is possible for such
things to go on continually through a long series of years and escape
detection. The financial loss occasioned by an unusually disastrous
outbreak of these pests can be estimated, but it is a mistake to sup-
pose that such losses constitute more than a very small percentage of
the amount annually filched from the farmers by these insidious foes
of his crops. It is not so much the big losses that occur at rare inter-
vals, and of which we read much in the public press, but the infinite and
perpetual leaks from this source that pull down the farmer’s profits —
leaks that, as has been shown, he may readily prevent in a most inex-
pensive manner. It is for the very reason of their obscurity and
insidious attacks, coupled with the magnitude of the losses caused by
them through a long series of years, that has prompted a study of
their habits and the publication of the facts in the present form.
THE TWO-WINGED GRAIN AND GRASS FLIES.
The insects included under this head are true flies, having only two
wings and their }mung are maggots without feet, eyes, or jaws. They
belong to the family Oscinidae, containing a large number of species
with variable food habits, some of them not attacking plants, but living
on the cast skins of other insects, shells of insect eggs, and in the bur-
rows made in plants by other insects. Some of them are leaf-miners,
others live in galls on grasses, while still others live underground on
the roots of plants. Still others, that are known to live in the stems
of grain and cause more or less destruction by their attacks, will be
here considered, though it must not be supposed that there are not
still others of such depredators of which we as yet know nothing.
Our grain-affecting species are to be found in the genera Meromyza,
Chlorops, Elachiptera, and Oscinis. It is to the last that the very
destructive frit-fly {Oscinis frit) of England and Europe belongs and
which is so terribly destructive to grain crops in those countries. The
habits of Meromyza americana have been pretty well studied and we
now have a fairly good knowledge of its life history and habits; but of
the most of the other species belonging to the above genera we only
41
know that the}7 attack the stems of wheat and other smaller grains, but
we are far from possessing a full knowledge of their life c}Tcles.
Chlorops proximo, Say is known to attack wheat plants in Kentucky,
flies emerging in May ; I have reared Elaclnptera longula Loew from
maggots in the stems of Panicum crus-galli in Illinois, the flies in this
case appearing late in August, and from both wheat and oat plants in
Indiana. It has also been reared from oats in Ohio by Prof. W. B.
Alwood. From wheat plants in Indiana I have reared Elachijotera
nigricornis Loew, and from the same lot of plants I reared also E. costata
Loew, the latter having been reared from oats in Ohio by Professor
Alwood and from maggots found in a decayed cavity in the roots of
living garden radish in Illinois b\7 Mr. Coquillett. The extent to which
the larvae of the last species attacks and destroys wheat plants is uncer-
tain, for though I have reared them from volunteer wheat plants grow-
ing up in the fields I have never been able to separate their maggots
from those of Oscinis. I have reared Oscinis trigramma Loew and 0.
coxendix Fitch from volunteer wheat plants in Indiana, and 0. dorsata
Loew, 0. coxendix Fitch, 0. umbrosa Loew, and 0. trigramma Loew
from August-sown wheat at Wooster, Ohio. Oscinis carbonaria Loew
is treated in this paper under the head of the lesser wheat-stem maggot.
The larvae of all of these except Meromyza closely resemble each other,
work in the young plants, and, some of them at least, destro}7 the cen-
tral stem before the plant tillers or individual tillers afterwards. The
larvae or maggots are small, yellowish white, pointed anteriorly, but
more blunt at posterior extremity, without jaws, but provided with a
pair of minute hooks whereby they rend the tender growth of the plant
and extract the juices. They may generally be found in the midst of
their work surrounded by the injured tissue and grass saturated with
the sap of the plant, and later on the brown puparia may be observed
about the bases of the young plants in late fall and even outside the
sheaths, and scattered on the ground in spring. The}T are often mis-
taken by farmers for the u flaxseed" or corresponding stage of the
Hessian fly.
WTERE PROBABLY ORIGINALLY GRASS FEEDERS.
Beyond a doubt the larvae of these flies were originally grass feed-
ing, and we find them at present developing in the stems of grass, but
seemingly preferring grain at times, probably when the grain at the
time of oviposition offers a more inviting place for the female to
deposit her eggs with the assurance that her offspring will be within
reach of an ample supply of food. Until the last half of the last cen-
tury the average farmer paid little attention to such matters, and, as
the flies were as now less thoroughly studied than other insects, there
wTas little to encourage the entomologist in attempting to study their
habits, as it is rather a thankless task to rear them and get their life
42
history worked out only to learn that the species can not be deter-
mined, and the information thus gained is thus rendered practically
worthless because of not being able to state definitely which of the
many forms one has been studying. Only recently I have learned
the name of a species reared from grass stems eighteen years ago.
For this reason even now the earlier stages of nearly all of those reared
from growing grain are obscure or unknown, the flies having simply
been reared from grain or grass, but the young of any particular
species can not be separated from those of perhaps a half dozen other
similar flies. There is much need at present of careful studies of
these insects with a view of determining their exact relation to agri-
culture, and especially to what extent they may be combated outside
the grain fields of the farmer. At present not more than one farmer
out of a thousand knows of their existence, and the injur}^ they do is
attributed to the Hessian fly, thus to a certain degree throwing
obscurity over all reports of the ravages of the latter insect, which
can not be reached outside the grain field, while some at least of these
other flies surely can. When I began to study the life history of the
lesser wheat- stem maggot, in 1884, it was the most unsatisfactory
and, at that time, to all appearances, the most unprofitable piece of
work that I ever undertook, for the reason that it was impossible to
separate it from other similar species; but this has now been largely
overcome with this insect, and we know that much can be done to
prevent its injuries.
EARLY REPORTS OF INJURIES TO GRAIN.
One of the earliest reports of injuries to grain in this country that
can be attributed to these insects with any degree of certainty was
cited by A. S. Fuller, from the works of M. Du Hamel du Menceau
(New Hamburg edition of 1759), as follows: '
There is a smaller kind of worm which gets into the roots, chiefly oats, and work-
ing upward destroys all the inside of the plant, which perishes soon after. I sus-
pect it to have been an insect of this kind that destroyed so much wheat in the
neighborhood of Geneva, and which M. de Chateauvieux described thus: “Our
wheat in the month of May, 1755, sustained a loss which even that cultivated accord-
ing to the new husbandry did not escape. We found in it many little white worms,
which afterwards became a chestnut color. They post themselves between the
blades and eat the stems. They are usually found between the first joint and the
roots. Every stalk which they attacked grew no more, but became yellow and
withered. The same misfortune happened to us in the year 1732. These insects
appeared about the middle of May and made such havoc that the crop was almost
destroyed. ’ ’
The attack on oats was clearly that of the stalk borer or heart worm,
the caterpillar of the moth Papaipema ( Gortyna) nitela Guen., but
that in the wheat does not accord with the work of any other than of
some of these small grain and grass dies under consideration. Mero-
43
myza maggots do not turn brown or “ chestnut colored/' and those of
the Hessian fl}T, even if it were known to occur in America at that
early date, do not eat oft' the stems. As early as 1822 Mr. James
Worth, of Bucks County, Pa., seems to have reared these flies from
maggots attacking wheat.
It is therefore probable that as the area of cultivation increased
in this country these insects have gradually transferred their atten-
tion from grass to grain as a matter of necessity, and though more or
less numerous every year in the grain fields, they become excessively
so when the grass conditions are less favorable than those of the grain;
but the grasses are a continual source of supply from which the grain
fields are colonized. These interrelations may be more or less cur-
tailed by the farmer with but little expense.
THE GREATER WHEAT STEM-MAGGOT.
( Meromyza americana Fitch. Fig. 14.)
. PAST HISTORY OF THE INSECT.
This is in all probability an insect native to the far South, as it
occurs in Mexico and northward over the entire United States and far
into British America, its food plants, before the advent of the Cau-
casian farmer, being the wild grasses. The fl}" was described in 1856
under the name here applied, but without definite proof of its attack-
ing grain further than that it was collected in wheat fields and closely
resembled the European species Meromyza saltatrix Linn. There is
now, however, considerable evidence of its having attacked growing
wheat at least as early as 1822 in Pennsylvania a and in 1845 in Michi-
gan.* 6 The evidence furnished by Mr. James Worth, of Bucks County,
Pa., indicates tha_t three broods were observed, as he calls attention to
the attacks of “ a little worm found in the lower part of the stalks of
wheat and rye in spring and fall and about the joints in June." Of
these larvae he says that “some were pale yellow, with brown spots
about the mouth," which would imply that they were those of some
species of Isosoma; but he further states that one kind was found in
volunteer wheat, which the Isosomas do not attack, and their larvae
are not found in the plants in fall, and in case of only one, with a
possibility of another species, are they to be found in the plants in
spring. While Mr. Worth evidently was not able to separate the
different species of the larvae found in growing grain, his careful
descriptions and exactness in locality and dates are exceedingly val-
uable and enable those familiar with the forms of which he writes to
recognize them with reasonable clearness. Hence we are left with
little doubt that he observed the larvae of Isosoma and Meromyza
«The American Farmer, vol. 4, p. 394; Memoirs Penn. Agl. Soc., Vol. 1, p. 165.
& Prairie Farmer, Sept., 1845, p. 216.
44
without separating them, and also in fall, including those found in
volunteer wheat, this latter species and other Oscinkke. The reference
in the Prairie Farmer seems to have been drawn out by a notice in the
Michigan Farmer of a new wheat insect in that State, described as the
product of a greenish fly about three-sixteenths of an inch in length,
whose larva is a white worm one-fourth of an inch long, ribbed, without
feet, with two forked lines on its forehead, found in the straw above
the upper joint, where it devours the juices which would otherwise
ascend to the head, but which denote the presence of the worm in the
straw by turning white prematurely when the grain is in the milk.
There is also here reference to the presence of “9 eggs * * *
found in a single straw, one of which had just hatched,’' but which
eggs, so called, are now known to have been the bodies of a minute
parasitic mite, whose
rounded form is not unlike
that of an egg and which
is occasionally found
attacking the maggot in
the straws.
Doctor Fitch did not
rear the flies which he
described, but collected
this in connection with
several species of Oscinis
by sweeping in the wheat
fields with an insect net.
Being familiar with the
grain attacking habits of
similar insects in Europe,
he expected, as he say's, to
rear the flies from the
growing wheat plants at
different seasons, but fail-
Fig. 14. — Greater wheat stem -maggot ( Meromyza americana ).•
a, mature fly; b , larva; c, puparium; d, infested wheat stem —
all enlarged except d (from Marlatt).
ing, as he states, to do this, contented himself with describing the flies
without attempting to connect them with the injuries which he clearly
observed. Nothing further appears to have transpired relative to this
insect until in the year 1867, when Doctor Riley reared the fly from
larvae working in the growing stems of wheat, immediately above the
upper joint, in the month of June, and in Missouri. In this case the
flies appeared during the first week of July, after a pupal period of
twelve to fourteen days. These facts were published in the Rural New
T orker for January 28, 1869, and in his first report as State entomol-
ogist of Missouri he discussed the insect and gave illustrations of the
adult, larval, and pupal stages, but does not appear to have suspected
the occurrence of a second brood later in the season. In 1876 a farmer
of Hinckley, Ohio, reported it as attacking his spring wheat. a We
a Country Gentleman, July 27, 1879.
45
also hear of it during this same year in the State of New York, where
stalks of growing wheat containing the larvae were sent to Doctor Lint-
ner, from Scipioville, in August. Some of these stalks contained
larvae, and some of the tiies were observed crawling about on the table
where the package had been unwrapped, and these were supposed to
have emerged from the straws while in transit. Doctor Lintner adds
nothing to our knowledge of the species at this time, but gave it the
common name of the wheat stem-maggot in preference to Doctor
Fitch’s American MeromyzaA
In March, 1883, Dr. S. A. Forbes, State entomologist of Illinois,
received information of serious injuries to young wheat in Fulton
County, of that State, and on investigation found the depredator to be
a small, slender maggot which attacked the plant just above the root,
thereby killing it. Farmers in the infested territory had noticed the
injury during the preceding November and December, but had not
taken steps to learn of its destructive character until, with the coming
of spring, the pest seemed to break out anew. From larvae taken from
infested plants from these fields puparia were obtained April 30, and
the flies began to appear by May 4, and continued to emerge until
June 1, thus showing that the insect might do serious damage to young
wheat in the fall, pass the winter in the maggot stage, and resume its
work of destruction again in spring. This, taken in connection with
what had been observed by Riley and Lintner, showed plainly that the
flies emerging in May and June oviposited in the growing stems of
the wheat, and the larvae hatching from these eggs entered the stems
just above the upper joint. Doctor Forbes, in his thirteenth report as
State entomologist, gave full details of his observations and called
attention to the possibility of a third brood developing in midsummer,
and also gave the insect the common name of the “ wheat-bulb worm.”* 6
During the summer of 1884 I was engaged as a special agent of the
Division of Entomology, under Doctor Riley, and from June 1 to Octo-
ber was located at Oxford, Ind. , engaged in the study of grain insects,
especially those attacking wheat. From straws taken from a field near
Oxford I reared adult flies up to July 26, and volunteer wheat, taken
from this same field September 5 and sent to Washington, gave adults
September 11, 13, and 16, according to the divisional notes. During
the same year adults were reared from volunteer wheat October 1 and
found in the field of young wheat on October 6.c In 1886 Doctor
Forbes put the final touch, so to speak, to the settlement of the occur-
rence of this midsummer brood by finding both eggs and larvae on
August 4 in volunteer wheat, and in his fifteenth report (p. 39) con-
structed a calendar showing the periods covered by the several broods.
«Loc. cit., Vol. XLIV, p. 535, 1879.
6 13th Rept. State Entomologist of Illinois, pp. 13-29, 1884.
c Rept. U. S. Comm. Agr., 1884, p. 390; Bull. 9, Purdue Univ., Oct., 1886.
46
This calendar shows our combined work on the insect, and is all the
more valuable on account of our having* worked entirely independently
of each other over territory within the same latitude, and with other
conditions in every way similar. It is also a matter of interest that
on February 27, 1891, I collected all stages of the insect except the
eggs in wheat growing on the grounds of the Agricultural College of
Texas, at College Station.
LIFE HISTORY.
Throughout the region of latitude 40° N. the insect is three- brooded,
although there may be but two in the north and more than three in the
far south, though Doctor Fletcher states that about Ottawa, Canada,
about latitude 45° N., there are three broods, the adults appearing in
the beginning of June, the end of July, and again late in September.
My observation in Texas, about latitude 30° 30', does not necessarily
indicate additional broods, as there may be, as with the Hessian fly, a
prolonged summer resting period, during which the insect is continued
in a stage requiring no food and incapable of reproduction, until the
vegetation upon which the larvse are dependent for their food supply
begins to take on new life, and, as with the Hessian fly, we may find
that the very conditions that serve to prevent the starting up of the
fresh growth of vegetation, so essential to the life of the young larvse,
has also the effect of retarding the emerging of the parent insects. Such
problems as these are for National investigation, where imaginary
lines and political boundaries do not enter into consideration. Within
the wheat belt of the United States, broadly speaking, the life c}Tcle of
this insect is as follows: The winter is passed in the larval stage, and
the short pupal stage coming in May brings the emerging of the adults
at the time when the female is able to place her eggs on the plants
where the young, on hatching, will make their way to the tender and
succulent stem just above the upper joint. By the time the straw has
ripened the larvse have ceased to require food, and pass through the
pupal stage, the adults of this brood appearing in July. Eggs are now
deposited in volunteer wheat and grass, and, owing either ta the retard-
ing effects of meteorological influences or a diversity of food of the larvse
or both, perhaps, the emerging of the adults is prolonged throughout
a period extending from late August through September until late
October. At this period the fall wheat offers a decided^ inviting
plant to the female fly on which to place her eggs with a prospect of
her progeny having an abundant food supply. It is the larvse from
eggs deposited during this period that winter over in the plants and
give rise to the May -June generation of flies. It is this last brood that
is of more especial interest to the farmer, as it is very seldom that the
pest does serious injury to grain except in fall and early spring.
47
DESCRIPTION.
Adult. — Length, 0.17 inch to tip of abdomen and 0.20 inch to end of wings.
Color, yellowish white, with a black spot on the top of the head, which is con-
tinued backward to the pedicel of the neck. Thorax with three black stripes,
approaching each other anteriorly, but not coming in contact, the middle stripe pro-
longed anteriorly to the pedicel of the neck and posteriorly to the apex of the
scutel. Abdomen with three broad, blackish stripes, which are confluent posteriorly
and interrupted at each of the sutures. Tips of the feet and veins of the hyaline
wings blackish. Eyes, bright green. Antennae, dusky on their upper side. (Lintner.)
Egg. — Snow white, fusiform, longitudinally ridged, the space between the ridges
being concave and marked off into rectangular areas by still slighter ridges transverse
to the others. Length, 0.023 inch; breadth, 0.005 inch. (Forbes.)
Larva , — Very pale green, slender, footless, tapering anteriorly, somewhat nar-
rowed, but subtruncate posteriorly; one-fourth of an inch in length by about one-
eighth of an inch in width. The segments are thirteen in number, including the
head, those in the center of the body being a little wider than long. The four ante-
rior segments narrow rapidly forward, the one next the head being at its apex less
than half the diameter of the fourth. The three posterior segments are also some-
what narrowed, the penultimate being about three-fourths the diameter of the sec-
ond preceding. The head is provided beneath with the pair of black toothed hooks
common to many dipterous maggots. The antennae are very short, scarcely longer
than broad, two-jointed, the second joint extensile. There are two circular, appar-
ently sensory, areas below the antennae upon the front of the head, doubtless repre-
senting maxillary palpi. The mouth is beneath the head, sucker-like in form. The
last or anal segment is divided into two lobes and bears upon its posterior surface
two breathing pores or spiracles, each guarded by a circlet of about twelve depressed
spines. The surface of the larva is entirely smooth and shining, except for some
very fine transverse ridges on the under side of the segments, evidently used in loco-
motion. On each side of the base of the second segment is a small, gill-like append-
age, divided into two lobes, each lobe with six divisions. (Forbes.)
Pupa. — The pupa of this species is what is technically known as a coarctate pupa,
contained within the last skin of the larva, which is not shed previous to transfor-
mation, but remains as a protective envelope for the forming pupa. As the latter
shows through its case, the color is green, except at the ends, where, with the growth
of the pupa within, the case is left empty and transparent. It is about one-sixth
of an inch long by one-fifth in width, and divided into ten clearly recognizable
segments. The anterior of these, corresponding to the head and first segment of
the larva, is yellowish, shrunken, and corrugated, about half the width of the third
segment. The second and third are obscurely divided, the first being short and
narrowing rapidly forward. Within it are observed the retracted maxillae of the old
larva. The remaining segments to the eighth are about equal in length, separated by
deeply impressed sutures at first, the anterior sutures becoming obliterated as the
enlargement of the head and thorax of the pupa within distends the envelope. The
ninth segment is the longest of all, the tenth being nearly equally long, but narrower,
and shrunken and wrinkled on its posterior border. The eleventh, representing the
twelfth of the larva, is only a brown and corrugated rudiment. As the development
of the pupa approaches completion, the eyes, wing-pads, and legs are visible through
the transparent covering, but they form no elevations of the surface. (Forbes.)
FOOD PLANTS.
Besides wheat, rye, oats, and barley, all of which it has long1 been
known to infest, I have reared Meromyza americana from the com-
48
mon blue grass (Poa pratensis) , while Doctor Fletcher, in Canada, has
reared the Hies from maggots in the stems of Agropyron, Deschampsia,
Elymus, and Poa, and as he states that the Hies are enormously abun-
dant in meadows and prairies all the way from northern Quebec
through the Lake Superior region, Manitoba, and the Northwest Ter-
ritories, there seems to be ample proof of its ability to sustain itself
without trouble among the grasses of that country.
The extent to which it attacks fall wheat in autumn is entirely
obscured from the fact that, in the majority of cases, it is confused
in its work of destruction with the Hessian fly. In Ohio, at a time
when the Hessian fly was being accused of devastating whole fields of
wheat in the fall, by collecting a great number of the affected plants
at the beginning of winter and placing them in the insectary I reared
fully as many of these as I did of the Hessian fly, which at that time I
was especially engaged in investigating. It is on this account that the
entomologist who attempts to stud}" the economics of the Hessian fly,
which does not breed in the grasses, will find the greatest difficulty in
weighing the evidence offered by those who can not or will not note
the difference in the nature of these insects and the great similarity in
the final effects of their attacks upon growing fall wheat in autumn
and spring.
SELECTION OF FOOD PLANTS BY THE ADULTS.
Either some A^arieties of the same kind of grain are more or less
repugnant to the flies, or else they possess a very finely adjusted sense
of the larval preferences for certain other varieties, for they certainly
exhibit a considerable discrimination in their selection of the different
varieties of wheat on which to place their eggs. Doctor Forbes has called
attention to the fact that the most seriously injured fields of wheat in
Fulton County, 111., in 1883, were of the Fultz variety. At Lafayette,
Ind., June 14, 1889, among a lot of experiment plats on the experi-
ment-station grounds, sown side by side, on the same day, with the
same soil and other conditions, there was a marked difference between
the number of affected straws in the Velvet Chaff and in the Michigan
Amber, the infestation being fully four times greater in the former
than in the latter. Even in the case of larger fields bordering each
other the conditions did not vary, and where the two varieties over-
lapped along the margins the same partiality for the Velvet Chaff had
been shown. Doctor Fletcher has also noted a strong prejudice in favor
of some varieties of the same kinds of grasses. For instance, while
Poa serotina was one of the most seriously affected of all of the grasses,
P. pratensis , P. cddsia , and P. compressa were almost exempt from
attack. Attack on Setaria mridis was observed in a single instance.
PLACE AND METHOD OF OVIPOSITION.
According to Forbes, the eggs are placed on the stems of grain, “some
being pushed down beneath the ensheathing bases of the leaves and
49
others cemented to the stems just at the margin of the sheath, while still
others were placed along the edge of the sheathing base of the leaf,
sometimes being thrust under the edge." This agrees with my own
observations and is doubtless the usual method of oviposition, as the
main object on the part of the female is to place the eggs where the
young larvae will the most easily reach the tender, juicy stem as soon
as possible after escaping from the egg, and is probably true in the
case of grasses as well as of grain.
METHOD AND NATURE OF ATTACK.
Both Doctor Lintnerand Doctor Forbes have endeavored to indicate
this by the selection of explanatory common names for this insect. The
former, disregarding Fitch's name, American Meromyza, as too tech-
nical, and having observed the larvae in the full-grown straws only,
gave it the name of the “wheat-stem maggot,” while Doctor Forbes,
having first encountered the larvae in the bulbous lower stem in early
spring, gave it the name of the “wheat-bulb worm,” on account of
its resemblance to the “wheat-bulb maggot” ( Hylemyict coarctcita) of
England. It is really a maggot and affects the stems of the plants
which it infests, besides being the largest maggot of this kind at
present known to attack the stems of grain in this manner in this
country; hence, in order to distinguish it from other smaller stem
maggots, I have here termed it the “ larger wheat stem-maggot.”
The larva has no jaws or mouth, but a couple of hook-shaped
appendages by which it tears the plant and feeds from the juices, the
cavity made by this destruction of the stem being filled by a pomace-
like mass in which the larva is to be found. The effect on the plant
is shown by the accompanying illustration (fig. 14, d). In young
plants the central spindle-shaped enfolded leaf is killed, precisely as
with attacks of Oscinis larvae, the detached portion turning first yellow
and later brown, then shriveling up and dying, leaving the outer
lower leaves uninjured. In Hessian -fly attacks this spindle-shaped
leaf is absorbed and does not appear at all in young wheat in autumn,
so that there need never be any confusion of the work of these two
insects in fall wheat, and the effect on the full-grown straws is even
more easily distinguishable. When attacked by the maggots of this
species the fully grown straw withers at the upper joint and all that
portion of the stem including the head, the sheath excepted, changes
to a whitish color, the remainder of the plant, including the upper
sheath, continuing uninjured and of the usual green color. The Hes-
sian flv never affects the full-grown straws in this manner and the
lesser wheat stem-maggot does so but rarely, so that the presence of
these maggots in the straw can be easity detected shortly prior to
harvest by their whitened color from the upper joint upward. The
larvae are within the stem and not outside and under the sheath, as
7327— No. 42—03 4
50
with the Hessian fly; they are larger and of a more glassy green color
than those of the lesser wheat stern-maggot, and it is only when still
very young that the ordinary farmer need ever mistake them for any
of the others mentioned in this bulletin. It is only in the manner of
killing the stem of young wheat that it need be confused with others.
EXTENT OF RAVAGES.
Though present in the fields every year, as is witnessed by the
whitened heads of grain in the fields just prior to harvest, I have never
known a serious attack at that season of the year; nor is there any-
thing at present to indicate that it is likely to work more serious
injury at this season in the future than it has in the past.
Its ravages in the }7oung wheat in fall and spring, as illustrated by
the outbreak in Illinois in 1882-83, are not as yet of usual occurrence,
though several similar instances have come to my knowledge within
the last twenty years. In two cases— one in Indiana in 1888 and
another in Ohio in 1900 — the fields were also badly infested by Hes-
sian fly, but from the material reared it would seem that this species
was to be credited with no small percentage of the loss. Occasionally
fields of fall wheat, especially if sown early, are attacked in the fall
and ruined by this insect alone* though the damage is in some cases
attributed to the Hessian fly. It is, however, easy enough to detect
the difference between injuries caused by these insects, as has been
explained under methods of attack.
PREVENTIVE MEASURES.
The liability of attack from this insect is not sufficient^7 great to
warrant any expensive measures being put forth in order to forestall
possible outbreaks. As yet, we have no way of foretelling these sud-
den attacks, as the pest has never proven excessively abundant in the
same locality two years in succession. The fact that late-sown wheat
is less subject to injury, and in cases where the two have been found
in a combined attack, the grain has been sown early, indicates that this
now-accepted method of warding off an attack of Hessian fly will work
equally well with this species. There is nothing at present to indicate
any change from these conditions throughout the winter-wheat grow-
ing regions of the Northern States. Whether or not the same rule
will apply in the South remains to be seen, as we know too little of
the pest in that portion of the country to be able to speak positively.
In the North, in the regions devoted to the raising of spring wheat, it
would appear that a burning over of the grass lands in winter would
reduce the probabilities of attack. The destruction of volunteer wheat,
which should be done in any case as a protective measure against
attacks of Hessian fly, will of course tend to reduce the probability of
the young wheat being attacked in autumn. It must be borne in mind,
51
however, that this is a grass as well as a grain insect, and eradication
from the grain fields will not protect from infestation from without.
NATURAL ENEMIES.
The abundance of one of these and the extent to which they are
able to perform their deadly work is a most encouraging feature,
viewed from the standpoint of the husbandman. A small, shining
black, four-winged fly, with reddish-yellow legs (Ccelinius meromyzae
Forbes), is exceeding beneficial in its parasitic work on the maggots of
this pest. This parasite wras discovered and described by Doctor
Forbes in connection with the investigations of the outbreak in Illinois
in 1883. So abundant is this parasite that it is almost impossible to rear
the flies from the straws in J uly without also rearing numbers of these
diminutive friends. They attack the maggots by placing their eggs in
their bodies, and the eggs hatching feed upon the maggots and destroy
them. This parasite occurs generally with the depredator, even in
the far North.
Another natural enemy is the mite Pecliculoides ( Ileterojpus ) ventri-
cosus Newport, illustrated on page 22. The young of this insect are
so very minute as to be quite invisible to the unaided eye. They are
without wings, but very active, and make their way to the maggot
working within the stem and fastening themselves upon it suck its
blood, in the meantime themselves increasing rapidly in size until
the}T appear like minute globular eggs, the abdomen being distended
with young, as there are no males, and the body having much the
proportions the stem has to the pumpkin. Each female gives birth
to a great number of young, which at once either escape to other stems
to hunt out their victims or else settle down with the parent. These
are frequently found attacking the maggots and are apt to escape
detection, or, if observed, mistaken for eggs. The reference in the
Prairie Farmer, calling attention to the presence of what probably
were these maggots in stems of wheat previously cited, also mentioned
the presence of nine eggs with the maggot. Without a doubt these
were the mites that had attacked the maggot, though this was long
before the mite was known to inhabit this country, it being a native
of Europe, as far as now known.
THE LESSER WHEAT STEM-MAGGOT.
( Oscinis ccirbonaria Loew. Fig. 15, d. )
With our present knowledge of the early stages of development it
is yet impossible for me to separate out from several other allied
species such as belong to this one and give a detailed account of its
life cycle, and especially is this true with reference to Oscinis soror ,
or what is the same thing, Oscinis variabilis Loew. To be able to do
this will require the most careful and exact studies of the early stages
52
of the offspring of adult flies belonging to each species ovipositing on
plants known of a certainty to be free from infestation by other
species. Such studies can only be carried out with the aid of better
conveniences than I have had at my disposal, and should be taken up
by the General Government, whose investigators are not restricted by
State lines, and who can follow wherever their problems may lead them.
Though Oscinis soror ( 0. variabilis) has been reared from growing
wheat by others as well as myself, I have found that 0. carbonaria
has been thus obtained with the greatest frequence7 over the widest
range and under conditions that lead to the belief that it is the more
important of the two, from an economic point of view at least.
LIFE HISTORY.
This can only be given in a general way, as in no instance has the
progeny of a single female been carried through the life cycle and the
several broods throughout the year clearly defined. I have myself
reared this species from
growing wheat in Illinois,
Indiana, and Ohio, over not
to exceed two degrees of lat-
itude, or collected them in
the wheat fields throughout
this area, or they have been
reared in Washington in the
Department insectary from
Fig. 15. — Oscinis soror Macq.; a, mature fly: b, antenna plants Sent there by me from
of same; c, puparium; cl, head, of 0. ccirboncirici — ci, c, d, IhlS Same temtOl'V as fol-
magnified; b, still more enlarged (original). f’
lows: Urbana, 111., July,
August, and September; Oxford, Ind., from May to October, not inclu-
sive; Lafayette, Ind., July, August, and September; Wooster, Ohio,
May, June, Juty, August, and September; and in the latter locality
from August-sown wheat. In the insectary I have also reared it in
November, December, and the following April, but did not observe it
abroad in that locality during November, December, or April. Besides
these rearings of mine, it was reared at Washington, July 7, from plants
received on the 3d of same month from Prof. Lawrence Bruner,
West Point, Nebr., and reared by Forbes, in Illinois, September 17,
from volunteer wheat. This is the species mentioned by Doctor
Fletcher as being so destructive in the Dominion of Canada in 1890, as
shown by specimens of the adult which he has kindly sent me. a
There was a bad outbreak of this insect in a field of wheat near
Wooster, Ohio, in the fall of 1891, and the field was badly affected.
In March of the following year I found many larvae and pupae about
the bases of the affected plants, and an attempt was made to study
a See Experimental Farm Reports, 1890, p. 158, and 1898, p. 177.
53
them further, but insufficient facilities for doing* so prevented. There
was, however, plent}T of evidence that the insect may winter in either
the larval or pupal stages. A single specimen was reared at the
Department in Washington from a stalk of wheat received from Mr.
J. G. Kingsbury, editor of the Indiana Farmer, the fly appearing
June 18. In this case the maggot was in the straw above the upper
joint, and the wheat head was evidently killed b}r its attack. From all
of these facts it seems that its life cycle may be about as follows: It may
winter over in the field either in the larval or pupal stage, the adults
emerging in May. From the presence of larvae in the stems of wheat
and grass from wdiich adults have afterwards been reared it would
appear that there is a brood of flies emerging in June and July, much
as in Merornyza americana , which lay their eggs in grass and volunteer
grain; another brood of flies resulting in September and October
whose offspring hibernate as previously stated, there being, as in
Merornyza, three broods each }^ear, from six weeks to two months being
required for the insect to pass through its development during the
summer months.
FOOD PLANTS.
I have reared these flies only from wheat, probably because I have
made no special effort to rear them from any other plant. Doctor
Fletcher has reared the species from Agropyron caninum , A. ienerum ,
A. repens , Poa pratensis, and Elymus canadensis. a
PLACE AND METHOD OF OVIPOSITION.
I have observed oviposition only among small wheat plants, but
presume that the methods employed in such cases do not differ from
those where the food plant is some of the grasses. The object on the
part of the female seems to be to place her eggs low down on the plant,
as near the root as possible and along the enveloping edge of the
sheath. The very young larvae are always to be found in this situa-
tion, and the edges of the enveloping bases of the leaves are always
ragged and discolored in infested plants.
NATURE OF THE INJURY.
The young maggot on hatching from the egg feeds along the thin
edge of the lower base of the enfolding leaf where it is white, juicy,
and tender. It seems to make no effort at first to reach the central
portion of the plant, seeming to know that that part will remain ten-
der and succulent, but gradually works its way inward and upward to
a point just below where the central spindle-shaped unfolding leaf
leaves the ensheathing portion of the next older one, the exact locality
seeming to be decided upon according to the toughness of this central
a Experimental Farms Reports, 1890, p. 158.
54
leaf, which of course varies with age and may be the first slender shoot
of the plant, or one of the older and tougher tillers of much older
plants. This central compactly rolled leaf is cut oii, the maggot at
first working upward until this leaf becomes too tough or begins to
wither, when it reverses its position and works downward, where the
food supply is always fresh and juicy. Pupation does not take place
here, but the larva makes its way when full fed to between the bases
of the older leaves, and in that situation the puparia are to be found.
A very }Toung plant does not admit of very extended travel by the
larva, and in an older one the continuity of its path is soon obliterated
by the growth of the plant itself, and the larva is frequently found a
couple of inches above the base where it entered after hatching from
the egg, as is witnessed by the minute patches eaten out of the leaf.
As but a single maggot is found in each stem, I have often wondered
if the female so distributed her eggs as to prevent a clashing of }Toung,
and feel very much inclined to the opinion expressed in some unpub-
lished notes by Mr. Pergande to the effect that more than one egg may
be deposited about a single stem, but the oldest and strongest maggot
kills off the weaker, leaving but one In full possession.
EXTENT OF RAVAGES.
Usually the work of this species is so confused with that of others
as to render anything like a definite estimate of the damage that can
be justly charged to its attacks in the grain fields almost impossible.
I have never observed injuries to the full-grown straw, though I have
occasional^ found larvae in them that I presumed to belong to this
species. In fall wheat the plant recovers from a slight injury, espe-
cially if growing in a fertile soil, and I apprehend that more damage
will follow an attack in fields where the soil is poor or badly worn
than where it is richer. In the field of wheat near Wooster, Ohio,
that was so severely injured in 1891, the Hessian fly was also present
and did fully as much injury as this insect, both I should say, destroy-
ing fully one-half the crop. Dr. Fletcher has called attention to a
field of spring wheat in Canada that was damaged fully 75 per cent,
for the most part due to the attacks of this species. In the United
States, I do not believe that an injury of from 5 to 15 per cent of the
crop by reason of the attacks of this and other Oscinis is at all unusual,
but this can not in all cases be wholly charged up to this particular
species.
DESCRIPTION.
The following description of the fly of Oscinis carhonctria has been
kindly drawn up for me by Mr. Coquillet:
A small, black, two-winged fly having the knobs of the halteres, the feet, and
usually both ends of the tibiae yellow. Length varying from 1 to nearly 2 milli-
55
meters (from one twenty-fifth to nearly one-twelfth of an inch). The last joint
of the antennae is nearly circular in outline, and on the upper edge is a nearly bare
bristle or arista; on the upper part of the otherwise opaque head is a polished,
nearly triangular spot that extends from the]extreme vertex almost to the antennae.
The wings are nearly transparent and are without an auxiliary vein — that is, there
are only three (instead of four) veins that terminate in the front edge of the wing
before its apex; the vein bordering the front edge of the wing extends beyond the
extreme apex of the wing; the usual two small cells near the base of the wing are
wanting, the anterior one being confluent with the discal or central cell, while the
posterior one is wanting, there being only one cell (the axillary) behind the fifth
vein. The legs are devoid of bristles and of stout, apical spurs, and are rather short
and robust; the first joint of the feet is rather slender and longer than any of the
other joints. The thorax is also without bristles, except along the sides and across
the posterior end; it is somewhat polished and is devoid of gray dust. The face
does not project strongly forward on its lower part; the proboscis is short, robust,
and terminates in the fleshy lips.
CLOSE RESEMBLANCE TO OSCINIS SOROR MACQ.
Oscinis soror Macq. is very closety related, but may be distinguished
by the fact that the polished spot on the upper part of the head
extends onl}T about halfway from the vertex to the antennae, instead
of almost reaching the antennae, as in the preceding species. (D. W.
Coquillett.)
At present, owing to the confusion of this species with soror , an
account of which will follow, it seems impossible to give desirable
descriptions of the preparatory stages of this insect. I have followed
those of Professor Garman, not knowing whether he was dealing with
this species or not, but because his descriptions seem to me to apply
as well to this as any that I could suppl}r. It must be kept in mind,
however, that this is only a temporary makeshift to give some kind of
an idea of what these look like, and thus enable the farmer to reduce
the uncertainty as to the identical species that is injuring his crop,
and that later and more careful investigations will probably show that
this and several other species, but with habits that are practically the
same, have been confused, and thus the present arrangement serve a
practical if not a scientific purpose.
Egg. — The egg of what is supposed to be this species was described by Mr. Per-
gande in the Department notes as follows: Colorless, polished, and longitudinally
ribbed with numerous extremely fine transverse striae.
Larva. — Cylindrical, white, with faint yellow cast. Body composed of thirteen
segments. No head and no legs. Mouth with two strong black hooks. Posterior
segment of body with a pair of knob-like prominences. Length of alcoholic speci-
mens, 0.14 inch.
Pupa. — In this stage the insect is inclosed in the hardened and brown skin of the
larva and this is called the puparium. This last is bright yellowish-brown, with
distinct and very finely wrinkled divisions. The two knob-like prominences in the
)arva are retained and are conspicuous at one extremity. The black hooks of the
larva are molted with the skin and can be seen through the puparium. The obso-
lete mouth of the larva is withdrawn, blackened, and wrinkled. Length from 0.10
to 0.14 inch.
56
PREVENTIVE MEASURES.
It is doubtful if one farmer out of a thousand fully realizes the
danger arising* from volunteer wheat. This growth springs up in the
fields in greater or less abundance, and is almost invariably left to
itself, as, having no value, it is thought not worth while to bother
with it. Besides, the general practice in many sections of the coun-
try of seeding the wheat lands to timothy and clover would prevent
any attempt to destroy the volunteer wheat, except by pasturing,
which is not considered a part of good husbandry at that season. A
rotation of crop, however, has in itself some advantages, as it forces
the flies to migrate from one field to another, in which there must be
more or less casualties, and many more would probably be attracted
to the grasses and the young fall wheat be protected to this extent
from attack. Where wheat is to follow wheat in the same field, it
will certainly pay the farmer to destroy this volunteer growth, as it
not only harbors all of these flies and offers unusual advantages for
the development of this midsummer brood, but it offers a breeding
place for the Hessian fly as well. Volunteer wheat, then, should be
destined wherever possible by the plow or disk harrow, and, where
practicable, by pasturing, so as to prevent the flies from breeding
therein. Burning over the grass lands, except timothy or clover,
where it is probably not necessary, will offer much protection, espe-
cially in spring-wheat growing regions, and where fall wheat is much
grown, reasonably late sowing will probably prove one of the most
effective means of protection.
NATURAL ENEMIES.
While this species probably has its usual number of natural ene-
mies, it is not always possible to determine the exact species from
which these have been reared, but an insect that is parasitic on one
species of these flies might be confidently looked for as being parasitic
upon other allied species. Ehyssalus oscinidis Ashm. is parasitic on
a species of Oscinis larvae mining in the leaves of plantain, in Wash-
ington, D. C. Aphxreta californica Ashm. and A. oscinidis Ashm.
have both been reared from other species of Oscinis, while I have
reared Cyrtogaster occidentcdis Ashm. from either this species, O.
sotot , or 0 . umbrosa , in Indiana, though it is known to occur from
Texas to South Dakota and east to Virginia and the District of Colum-
bia. These are all minute four- winged flies, and there are probably
many others that also help to keep these flies reduced in numbers. I
have also observed the common parasitic fungus Entomophthora muscde
attacking the flies, but this is probably a minor factor among their
natural enemies.
57
THE AMERICAN FRIT-FLY.
(Oscinis soror Macq. Fig. 15, p. 52.)
This species has been so interminably confused with other allied
species, especially with what has been going the rounds as Oscinis
varaiilis Loew? a synonym, and as frequently confused with 0. car-
bonaria as with this, that it seems almost impossible to say anything
about it with any degree of certainty that one is not really dealing
with something else. Oscinis soror is, nevertheless, a valid species,
and its larvae in all probability attack growing grain, though I have
myself rarely reared it from grain, and my proof of its destructive-
ness in wheat fields is unfortunately not as conclusive as I wish it were.
The larvae certainly have a wide range of food plants, as I have reared
it from maggots in the stems of Panicum crus-galli in Indiana during
September, and also from the stems of Poet pratensis in June and from
wheat in July. It has also been reared from larvae wintering in the
seed capsules of Vernonia noveboracensis May 15 in Washington, D. C. ;
in June and July, at Columbus, Ohio, from oat plants; from the roots
of cucumber, October 2, in Maryland; and from strawberry plants in
Michigan. Last year I reared the flies from the stems of Ercigrostis
minor at Urbana, 111., in September. These definitely authenticated
rearings of the flies show a wide range of food plants, and the species
is one of the most abundant of all the Oscinids.
CONFUSION WITH OTHER SPECIES.
Owing to a species having been found in Illinois and Kentucky
attacking wheat and doubtfully determined by Doctor Williston as
Oscinis variaMlis Loew, now known to be a synonym of this species,
and this determination having been applied elsewhere to other Oscinidse
attacking wheat, has led to much confusion, as where the name 0. vciri-
abilis has been applied to a form committing depredations, we can not
say with any degree of certainty whether the insect involved was this
species or 0. carbonciria , unless specimens actually reared from the
plants so attacked are at hand. Realizing the difficulty when I began
the preparation of this bulletin, I applied to Mr. Coquillett, of the
Lmited States National Museum, for suggestions as how to best over-
come it and received from him an offer to determine any material
reared from larvae attacking wheat in various parts of the country.
Doctor Fletcher had published accounts of the ravages of Oscinis vctri-
abilis Loew? in Canada, Dr. Otto Lugger of similar ravages of Oscinis
soror in Minnesota, and Professor Garman of the attacks of Oscinis
variabilis Loew? in Kentucky. Application was therefore made to
Doctor Fletcher, Professor Washburn, successor to the late Doctor
Lugger in Minnesota, and Professor Garman, for reared material in
order to as far as possible place the responsibility for these depredations
58
on the species actually engaged therein. Material kindly placed at my
disposal by Doctor Fletcher has shown that it was Oscinis carbonaria
Loew that committed the depredations in Canada. Professor Washburn
was less fortunate, though he did all that was possible for him to do to
aid me, and sent specimens that, judging from the labels attached, had
been reared b j Doctor Lugger, but whether from wheat or not it is
impossible to determine, as nothing could be found that would throw
any light upon this point. The specimens sent me from Minnesota by
Professor Washburn comprised two species, 0. soror and 0. dorsata
Loew, the former having been supposed by Doctor Lugger to have been
responsible for the injuries to wheat in Minnesota in 1892, while the
latter was reared by me from wheat plants in Ohio in the fall of 1897,
thus indicating that both might have been involved in the Minnesota
trouble. Assuming that Doctor Lugger had sufficient grounds for
holding Oscinis soror responsible for the damage in his State at the
time stated, I have so considered it here, but have thought proper to
indicate the uncertainties surrounding this conclusion. Not being able
to secure any material whatever from Professor Garman, I am forced
to reluctantty place the blame for the outbreak in the wheat fields in
Kentucky' in 1889 upon Oscinis soror , but with a strong suspicion that
it was really Oscinis carbonaria that was responsible for the trouble.
I have applied Doctor Lugger’s descriptions of the larva and pupa to
this species as being the best that can be done with our present knowl-
edge of these insects, but subject to revision, as future investigations
shall clear up more or less of the obscurity at present surrounding
them.
DEPREDATIONS IN MINNESOTA.
There is one fact connected with the Oscinis problem in Minnesota
that seems to point especialty to O. soror as the real depredator, and
not O. dorsata , and that is in the striking difference in the color of
the two, the former being black and the latter yellow, a difference
that could hardly have escaped the keen e}Tes of Doctor Lugger, and I
can not but feel that he was correct in his attributing the depredations
to the species now being considered. I strongly suspect that some of
the “deadheads"’ to which Doctor Fletcher has called attention in his
reports and other publications as occurring in the wheat fields of Mani-
toba and the Northwest Territories may have been to some extent due
to the work of this species also.
Doctor Lugger seems not to have studied the several generations of
the species in his State (Minnesota), but gave his attention especially
to the one that proved the most destructive. From what has been
stated of the insect farther to the southward, it wnuld appear that
there are the same number of broods as with 0. carbonaria , the pest
wintering over in the young plants of fall wheat and grass. In Min-
nesota it evidently winters in the straw, from which it would seem
59
that in the north there is one less brood than there is farther to
the south, a condition of affairs entirely possible, as we now know
that the Hessian fl}T is there largely at least single brooded, but double
brooded farther south. In his second annual report as State ento-
mologist, pages 6 to 10, Doctor Lugger gives these facts relative to
the work of the insect in his State:
During the summer and early part of the fall numerous letters were received from
many parts of the State in which the writers complained about minute worms which
infested the stems of wheat just above a joint from 3 to 4 inches above the ground.
The specimens received at the same time showed that, as a general rule, the first
and second joints of the plant were infested. Some farmers complained that their
crop of wheat was thus very materially reduced. The plants harboring the worms
did not indicate their presence until flowering time, but as soon as the head began
to form the stem above the injured joint wilted, turned yellowish, and soon broke
down entirely by bending over the infested spot. * * * But wdien the infested
stems were investigated it was found that the worm had weakened them to such an
extent that when the head was formed the plant became topheavy and broke down
at the weakest point from force of gravity. * * * These heads were either
entirely empty or filled with berries more or less shrunken. The bent or partly
broken stems were, as a general rule, still adhering to the lower portion of the plant.
This bending or breaking had taken place most frequently above a node or joint
about 3 inches from the ground. Just below this breakage, and immediately above
the joint, the culprits were to be found. In most cases but one puparium, but in
a few cases two, three, or even more puparia could be detected. Such a puparium
is the contracted and hardened skin of the larva or worm; it is of a glossy, chestnut-
brown color, shading to yellowish brown toward the smaller end. If closely
inspected it shows faint traces of sutures or segments. * * * These seed-like
objects contain at this time (October) whitish larvae or worms, and no pupae have
been detected inside of them up to this date. * * * Judging from the fact that
only pupae [puparia? — F. M. TV7.] can be found at this time, it would appear as if
this insect hibernates in that stage. This is really the only one in which it could
well pass our northern winters, being in that stage well protected by its old and
thickened skin and by the stem of the plant. The puparia are inserted in the mate-
rial of the upper part of the node, inaccessible to any moisture from the outside, as
the stem above does not break off entirely, but simply bends in a more or less acute
angle a short distance over them, thus preventing the entrance of water. Yet the
culm is sufficiently fractured to permit a free exit of the future fly in spring. * * *
The damage caused by this insect in 1892 was by no means small. In many
places fully one-fourth of the entire crop of wheat was destroyed, and in a great
many more the losses amounted to at least one-tenth. As many places are badly
infested, the total amount is quite large, and if no steps are taken to prevent it a
repetition may become ruinous in 1893. Most farmers plowed their fields in the fall
of 1892 or early in 1893, and consequently the losses in the latter year were small,
and in 1894 but very few of these insects wTere to be found. The spring of this year
[1896? — F. M. TV.] being very wet, prevented extensive plowing, and the insects,
not being disturbed or plowed under, again became a pest and caused considerable
damage. The name “frit-fly” is a well-deserved one, as Swedish farmers call the
worthless grain resulting from the attack of such flies “frits.”
LIFE HISTORY.
As stated by Doctor Lugger, the life history is still very obscure, and
it will require careful study and close observation to secure a knowledge
60
of it over the country. The facts given by him in his report are unlike
what has been observed farther south, but these differences are not
sufficient to indicate that it was not this species that caused the injuries
mentioned. Even if we assume that the insect reared in Kentucky by
Professor Garman belonged to this species, we find that adult Hies
have been reared by others in May, late June, and early July, and
again in September, thereby indicating three broods in the vicinity of
latitude 40°, the species wintering as larvae or pupae, probably the
latter, the flies emerging from these ovipositing in May, the adults
from these appearing in June and July, these in turn giving origin to
a fall brood in September, whose progeny winter over as stated. In
more northern and inland sections of the country it seems that the
fall brood may drop out and the one occurring farther south in
midsummer pass the winter as puparia and the adults emerge the
following spring.
FOOD PLANTS.
Either this has a greater range of food plants than Oscinis carbo-
narici , or else we have not learned much about those of the latter. As
it is, the food of this species is so varied as to almost incline one to
the suspicion that it stands accused of ravages that should be placed
to the credit of another but for the facts supplied by Doctor Lugger.
However, this variation in its bill of fare gives the farmer a still
better opportunity of fighting it outside his grain fields.
DIFFICULTIES IN STUDYING HABITS.
The fact that maggots taken from wheat plants in a field develop
these flies does not necessarily prove that other maggots attacking
wheat in the same field will produce the same species of flies; there-
fore, descriptions drawn up from such collections may or ma}T not be
correct, and for the same reasons observations on the habits of such
larvae are liable to be incorrect. It is only by placing flies on plants
known to be free from all other infestation and studving these that we
shall be able to get at the truth in relation to anatomical and biological
facts. An investigator will then know just which species he is dealing
with, and whatever descriptions are drawn up from material secured
in this manner and whatever observations are made upon them will be
sure to be accurate so far as the species under observation is concerned.
. In no case has this been done, and as a consequence we have only a
general knowledge of these insects, and any descriptions of the larvae
may or may not prove correct in future. Though there is a noticeable
difference between the adult figured by Doctor Lugger as this species
and the one figured by Professor Garman as Oscinis variabilis Loew ?
the figures of the larva and puparia are exceedingly alike. For the
same reason any recommendations looking to the control of the pest
61
in the grain fields must be made somewhat at random and aimed at
Oscinidae in general rather than at this particular species.
REMEDIAL AND PREVENTIVE MEASURES.
Over the area where winter wheat is cultivated the same measures
that have been urged against the two wheat stern-maggots will apply
equally well here, so far as we now understand the habits of this
species. These are the destruction of volunteer wheat, the burning
over of waste grass lands in winter and early spring, and late sowing
of the grain in fall. In spring- wheat regions the experience of Doctor
Lugger in Minnesota is strongly indicative of the effect of plowing the
infested fields as soon as possible after the crop has been removed.
He states that in the fall of 1891 and spring of 1892 not more than
one-half of the acreage of wheat land was plowed, owing to unusually
wet weather during these periods, and the pest that had gained a foot-
hold, as it were, in 1891, meeting with no reverses on account of lack
of plowing, simply continuing to increase in numbers, with the result
that in 1892 it committed serious and widespread depredations. Where
the fields can be burned over in fall or spring the result will, of course,
be the extermination of the pest in such fields in the northern portions
of the country, but farther south it is the grass lands that need to be
burned over, since there is no way of reaching the insect hibernating
in the winter-wheat plants. The fields of spring wheat in the North
will, of course, be to some extent also protected by the burning over
of the grass lands in fall or spring.
DESCRIPTION.
The difference between this species and Oscinis carbonaria have
already been pointed out in the treatment of the latter species (see
p. 55).
Larva. — This very closely resembles that of 0. carbonaria , as is
shown by the illustrations used by Doctor Lugger in his publications.
He states, however, that the larva is of a greenish-white color when
alive and just removed from the culm.
Puparium. — Here, again, it would be difficult to identify the pupa-
rium by either the illustration or description given by Doctor Lugger,
as both closely resemble those given of 0. variabilisf by Professor
Garman. Doctor Lugger describes this as being of a glossy chestnut-
brown color, shading to yellowish brown toward the smaller end, and
showing faint traces of sutures or segments.
Of the other species of small Oscinidae whose larvae are found in and
about the stems of growing grain I have alread}7 written, and it is
impossible with our present knowledge of them to go into further
details. Some of these may be destructive and some may not, as the
fact of these having been reared from grain plants does not necessarily
62
prove that they are destructive, as they may live upon the dead and
decaying older leaves or they may simply inhabit the burrows made by
other insects. The practical farmer will probably be able to meet their
depredations by the same measures that have been recommended for
those species with which we are the most familiar, at least until a more
extended study can be made and more light thrown on their habits.
CONCLUSION.
In the foregoing it has been the aim of the writer to so present this
subject as to enable the farmer to distinguish some of the more obscure
enemies of his crops and prevent a peculiar and subtle shrinkage in
the profits of his labors, and one that he can meet in most cases by
simple measures that cost nothing except the time consumed in carry-
ing them out during seasons or days of comparative inactivity on the
farm. Not all of the ravages in the wheat fields are due to the Hessian
fly, and, indeed, the crop reports are usually wholly unreliable in respect
to the actual occurrence of this insect, except it be in cases of over-
whelming numbers. One of the most practical preventive measures
that can be applied against the Hessian fly will also prove of value in
warring against these other pests, viz, late seeding of fall wheat in
autumn; and a second measure, that of rotation of crops, will be found
almost as valuable. Fighting insects demands a better system of
farming, which of itself will pay in other directions, and the American
farmer must calculate upon insect depredations as no small element in
his business. Of what use is it to rear two blades of grass where but
one grew before if he is to lose both of them by reason of insect attack ?
It is not the farm but the profits thereof that are lost through the
devastations caused by injurious insects, and it costs the American
farmer more to feed these insidious foes than it does to educate his
children.
O
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