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AGRICULTURAL ENTOMOLOGY
FOR STUDENTS, FARMERS, FRUIT-GROWERS
AND GARDENERS /
BY
HERBERT OSBORN, B.Sc., M.Sc.
PROFESSOR OF ZOOLOGY AND ENTOMOLOGY IN THE OHIO STATE UNIVERSITY,
COLUMBUS, OHIO, AND DIRECTOR OF THE LAKE LABORATORY,
CEDAR POINT, OHIO.
ILLUSTRATED WITH 252 ENGRAVINGS AND A COLORED PLATE
ih Ado EB GER
PHILADELPHIA AND NEW YORK
1916
Entered according to the Act of Congress, in the year 1916, by
LEA & FEBIGER,
in the Office of the Librarian of Congress. All rights reserved. ;
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PREFACE.
Tus book is designed to meet the needs of students and
others who wish to learn something of insect life especially
in relation to farm crops and livestock. The author assumes
that the students who read it will have had some traming
in general biology and will have the guidance of teachers
familiar with the subject in connection with adequate labor-
atory facilities and opportunities for field studies. The
details of laboratory and field studies have not been included
since these are easily supplied by the teacher. For those
making individual studies there are many available books
covering the technic of entomological work. A glossary
has been included which covers the subject as presented in
these pages and in most of the reports and bulletins that are
likely to be consulted by the average student.
In order to make the scope of the book adequate it has
been necessary to condense the matter to the most essential
details, and to omit much that has value but which is not
absolutely indispensable to the presentation of the important
principles that concern the practice of economic entomology.
The author acknowledges his indebtedness to many
sources of information which are too numerous to mention
individually, but he is especially indebted to Dr. Howard,
of the Bureau of Entomology, for the privilege of using the
illustrations secured from his office and for suggestions; to
iV PREFACE
Professors Washburn and Bruner for the loan of plates;
to the Iowa Experiment Station for use of figures, and the
Ohio Experiment Station for a number of photographs for
original use here. Professors Hine, Metcalf, Barrows,
Mr. Kostir and Mr. Drake have assisted in reading manu-
script and proof and have generously given the author
the use of photographs and drawings.
EO:
Cotumsus, Ouro, 1916.
CONTENTS:
CHAPTER I.
INTRODUCTION 17
CHAPTER. If.
Crass ARACHNIDA . Pape
CHAPTER, IL.
THE Six—FooTeD INSECTS a RR) OE ae ae ae i mer 38
CHAPTER) IV.
LowrErR PTERYGOTA tee ¢ ES Go DM Seen cs See il
CHAPTER, Y.
OrDER HEMIPTERA cc goa Ree ces Re te, dae 93
CHARTER, Var
NEUROPTERA AND ALLIES ear ee ae kom OO Meee ee a LG
CHAPTER VII.
COMMORTERAW SSERTURSH -. scikgm on lta Sah eee ses fy a O72
CHAPTER VIII.
IGE PED OPT RAMEE ME ve Aa ics cs i eae ee Carl PRE or DG
CHAPTER IX.
OrpDER DIPTERA SR IPT ee eee arom Mir ca As lato a Ro os
CHAPTER X.
IS EE SWAN DEN VASES ay oa ctr 5 One ee ne ami ee a) a WB to < OONT
CHAPTER Xa.
PRINCIPLES OF Economic ENTOMOLOGY . ... . eect We
CeOSSAR Valea era Pees wre NEE kr | ee es Le IDO
JGNWDIDD SE, 5. ee ae TRI an Blip ate alt I aR en ete? 1220
AGRICULTURAL ENTOMOLOGY.
CiHPAGE nae le
INTRODUCTION.
THE recent rapid growth in the subject of Agricultural
Entomology makes it a difficult matter to bring together
a comprehensive statement that will cover all of its different
phases in a thorough manner. Some idea of its growth
may be indicated by the fact that instead of a single ento-
mologist employed in the United States Department. of
Agriculture, as was the case forty years ago, there are now
several hundred who are devoting their entire time to the
investigation of entomological problems, practically all of
which are related to agriculture.
A similar development of this work has taken place in
the State Experiment Stations, and there are also State
Entomological departments working in almost every State,
and in many of them two or three different organizations,
each with a large quota of workers.
Economic entomology in its wider sense covers all those
phases of the subject which have to do with insects of
importance in relation to mankind. The forms which
have distinctly agricultural relation are so numerous and
represent so completely all the different groups of insects
that we are compelled to include a very general survey of
the subject.
Some idea of the size of the group of insects and of its
place in biological study may be secured from the statement
2 (17)
18 INTRODUCTION
that there are now known and have been scientifically recog-
nized and described something over three hundred thousand
species of insects, a number which far surpasses that of all
other groups of animals together. Furthermore, the immense
numbers of individuals in each species and the great facility
which they possess for migration and rapidity of increase
make them a very dominant group of animals.
Not all insects, to be sure, have a direct importance to
mankind, but there is so large a number that are very
directly related to human interests in the way of destruction
of property or menace to health that it is unnecessary to
emphasize their importance. Many estimates have been
attempted of the extent of loss of crops, livestock, forests,
agricultural products, ete., and while none of these can be
considered exact, it is increasingly evident that such estimates
are conservative and in many cases the loss is greater than
is recognized. One of the current estimates is that about
10 per cent. of the aggregate of farm crops in the United
States is lost by insect attack, and if this be taken as an
approximate proportion there is something like one billion
dollars to be counted an economic loss from this source
each year.
It must be admitted that the entomologist has not been -
able as yet to solve all of the problems of insect control.
There will doubtless be many cases where a practical control
of insects may not be reached for many years, but for a
considerable number of the most common and serious pests
it has been possible to discover methods by which a very
large proportion of the loss can be prevented. One phase
of entomological work, therefore, is the demonstration of
these possibilities in order to secure a general adoption of
control measures that have been proved successful.
While it is manifestly impossible to include in a small
book any full discussion of the many phases of entomology,
it is the purpose of this work to present a basis for the under-
standing of field observations, and especially for the under-
standing of the many articles relating to economic insects
which are now appearing in Government and State pub-
INTRODUCTION 19
lications. Many of these publications are available and will
be found to contain an immense store of information, much
of it of very practical value, but its greatest utility will be
found to rest upon some acquaintance with the general
facts of insect life and insect habits. These are so dependent
upon certain conditions of structure and development that
acquaintance with some of the fundamental biological
features of insect life are essential to the most effective
utilization.
Formerly all of the arthropods, that is, all animals with
jointed bodies and jointed appendages, were grouped under
the head of insects, and even yet this term has a pretty
wide application in popular usage, although it is seldom
used now to cover as wide a range as formerly. The Arth-
ropods, as a whole, include crustaceans, myriapods, arach-
nids, hexapods, or six-footed insects, and of these the air-
breathing forms, all except the crustaceans, are still quite
commonly treated as insects.
The Onychophora is a tropical group including peripatus,
the most primitive of tracheate animals, and would on this
basis be considered as falling next to the crustacea.
The most generalized next to these, the myriapods, might
be counted as possessing the greater number of insect-like
characters. This group, however, does not include any
forms that possess wings, but in the matter of antennee and
the tracheal respiration they are closely associated with
insects. The members of this group are, for the most part,
of comparatively little economic importance. A few of the
species included in the group of centipedes (Chilopoda) are
poisonous, and in tropical countries are of some importance
on this account. The few species that occur in temperate
regions have little importance except as they may feed upon
other insects which occur under the litter at the surface of
the ground.
One species, the house centipede, a peculiar long-legged
creature, which is occasionally found in cellars or around
houses, usually where there is some dampness, is, however,
of a certain amount of importance because of its feeding
20 INTRODUCTION
upon insects, and is looked upon as rather serviceable in the
destruction of flies. It is a quite ungainly looking creature,
Vic. 1.—Scutigera forceps: Adult—natural size. (From Marlatt,
Div. Ent., U. 8S. Dept. Ag.)
with slender, flattened body, extremely long legs, and an
apparent duplication of anterior and posterior ends.
iurent duplicat f ant 1 post ds
The millipedes (Diplopoda) are nearly cylindrical in
INTRODUCTION 21
shape, are recognized as having two pairs of legs to each
apparent segment and there is usually a large number of
segments, 40 to 100 or more, so that the name thousand-
Fic. 2.—Scutigera forceps: a, newly hatched individual; 6, one of the
legs of same; c, terminal segment of body showing undeveloped legs coiled
up within—all enlarged. (After Marlatt, Div. Ent., U. 8S. Dept. Ag.)
legged worm is fairly descriptive. Most of these species
are found in moist places and feed upon vegetable debris,
but a few have been recorded as attacking vegetation, and
one species has been credited with injuring seed corn.
CED ACP Reale
CLASS ARACHNIDA.
In the strict technical sense the group Arachnida may be
excluded from the Insecta, but in general usage, and to a
large extent in entomological practice, these divisions are
put together, and it seems desirable that the group should
be given a place in any work dealing with the insects in
general.
The group Arachnida includes spiders, scorpions, harvest-
men, mites, ticks, etc., and is characterized by the presence
of four pairs of legs, the absence of antenne and compound
eyes, and the lack of distinct metamorphosis, although
in certain groups there is a considerable change from the
newly hatched or six-legged form to the mature eight-legged
stage.
In general structure the Arachnida agree with other
Arthropoda, but the head and thorax are usually merged
into a cephalothorax separated from the abdomen by a
more or less distinct stalk; in the Acarina, however, this
separation is not marked and the body is without distinct
separation of head, thorax, and abdomen.
The economic importance of the group depends upon
their attacks upon certain crops, from the fact that many
of the species, such as spiders and harvestmen, are uniformly
predaceous and serve as important checks upon injurious
species; while other forms, such as the mites and ticks, are
parasitic upon domestic animals and man, and some of the
species occupy a most important relationship as carriers
of infectious diseases.
The subdivisions of the group are, for the most part, very
well marked and represent ancient groups which have
diverged quite widely from each other.
The scorpions (Scorpionida), mostly tropical in distribu-
(22)
CLASS ARACHNIDA 23
tion, are represented by fossils in early geological times,
and are noted as possessing poison glands. ‘They are recog-
nized by the broad cephalothorax, a division of the abdomen
into two portions, an anterior preabdomen of seven seg-
ments, and a slender hinder postabdomen of six segments,
on the last one of which there is a large poison gland and
sting. The sting is distinctly venomous and fatal to insects
or smaller animals, but seldom serious in its effect on the
human species.
The Pseudoscorpionida are minute forms resembling
scorpions in the width of the body and the long pedipalps,
but have no postabdomen or sting. They occur somewhat
commonly under bark or decaying logs or occasionally in old
papers or books, where they may secure book lice as food.
The Pedipalpi, or whip scorpions, have a tropical or
subtropical distribution and differ from the preceding groups
in the presence of a long, slender bristle or whip extending
from the hinder abdominal segment.
In the group Solpugida there is an exceptional separation
of head and thorax and the abdomen is distinctly segmented,
while the chelicerze are greatly enlarged and strongly chelate.
These are not only largely tropical, but are particularly
characteristic of arid regions. One species occurs in the
Rocky Mountain region as far north as Colorado. They
are carnivorous in habit, but not of particular economic
importance, as they occur usually in small numbers and in
locations which do not offer opportunity to capture espe-
cially injurious insects.
The Phalangida, or harvestmen, often called “daddy-
longlegs,’ are somewhat large and resemble spiders in
appearance, but the abdomen is not distinctly separated
from the thorax and the legs are in most species extremely
long. They feed on insects, especially on flies and other
small forms, and are to be counted as distinctly beneficial.
On account of a strong pungent odor they are disagreeable
to handle, but their presence in gardens and other places
where insects abound may be considered as distinctly desir-
able.
24 CLASS ARACHNIDA
Order ARANEIDA.
This group includes the familiar spiders which are very
generally distributed over the world, and occupy a rather
conspicuous place among other animals. Their body is
sharply divided into cephalothorax and abdomen, and the
four pairs of legs are usually nearly equal in length. The
Hiren:
Epeira scolopetaria, showing normal position of spider in web
head downward.
re7niget
Fic. 186.—The alfalfa caterpillar (Hurymus eurytheme): female in the
adult or butterfly stage. One-half enlarged. (After Wildermuth, Bur.
Ent., U. S. Dept. Ag., Fig. 2.)
Fic. 187.—The alfalfa caterpillar (Hurymus eurytheme): male in the adult
or butterfly stage. One-half enlarged. (After Wildermuth, Bur. Ent., U.
5S. Dept. Ag., Fig. 3.)
so that it must have an effect on the clover crop on which
the larva feeds.
MONARCH BUTTERFLY 245
In the Eastern Mississippi Valley and Atlantic Coast
States it is perhaps less common than the related sulphur
butterfly, Colias philodice, which is so plentiful as adults
that it is fair to assume an abundant progeny feeding in
clover fields.
Fig. 188 Fic. 189
Fia. 188.—The alfalfa caterpillar: egg—greatly enlarged. (After Wilder-
muth redrawn from Scudder, Bur. Ent., U. S. Dept. Ag., Fig. 4.)
Fic. 189.—The alfalfa caterpillar (Hurymus eurytheme): larva or cater-
pillar stage—about twice natural size. (After Wildermuth, Bur. Ent., U.
S. Dept. Ag., Fig. 1.)
Fic. 190.—The alfalfa caterpillar (Hurymus eurytheme): pupa or chrys-
alis stage—twice natural size. (After Wildermuth, Bur. Ent., U.S. Dept.
Ag., Fig. 5.)
Monarch Butterfly (Anosia plexippus).—TVhe monarch but-
terfly (family Danaid@) is interesting in two or three ways,
though not of any special importance economically. It is
one of the largest butterflies outside of the Papilios, and it
246 LEPIDOPTERA
is pretty readily recognized by the dark reddish-brown color
with black bands and stripings and the border including a
number of white spots. It deposits eggs on milkweed as its
host plant. These eggs hatch very shortly and the larvee
develop during the latter part of the summer and pupate
and become adults in autumn, and it is quite common in
October to see immense swarms of these butterflies. They
gather along hedge rows and on trees, sometimes appearing
by millions. Late in the afternoon they will cluster on the
branches in immense numbers. At the time of their gather-
ing in immense numbers they seem to have a general south-
erly movement and they are known to migrate at least to
some extent during the autumn, though the migrations
probably do not cover as long distances as that of birds—
not over 200 to 500 miles. They appear in great abundance
in the South in the winter. It is not possible to follow indi-
viduals for very great distances, but evidently they hibernate
in the adult stage in the South and it is pretty generally
believed that the hibernating individuals in Nor ther n locali-
ties are likely to perish. Indiv iduals that start the first
generation must have travelled from the South. The spring
individuals are frayed and give evidence of having travelled
some distance. The spring-appearing individuals deposit
eggs and from these the generation of caterpillars comes
that mature during midsummer. The adults appear in the
latitude of New York about the middle or last of July.
There are two distinct generations for each year. The cater-
pillar is quite prominently banded and has some striking
thread-like appendages. It reaches the length of one and a
half or two inches and is nearly as thick as a pencil. It is
found particularly on the milkweed. Their pupation occurs
by attachment to the leaves of the milkweed or plants or
objects convenient or adjacent to the host plant. The pupa
cases are attached by a sort of spur or hook at the posterior
end of the body caught into a little web that has been spun
on the leaf. The larvee locate on a suitable object and spin
a little web and then the larva contracts and the larval skin
splits along the back and this larval skin is held by the pos-
NYMPHALIDA 247
terior segment in such way that it can twist the pupa case
around and eatch the hook of the pupa case into the web.
The pupa case lasts only a week or ten days and then gives
rise to the adult form. It is mimicked by a species which has
an additional black band on the hindwing and there are
differences in the legs. This, the viceroy (Basilarchia
archippus) has evidently gained protection by taking on
the appearance of the monarch.
One other species in the family Nymphalide that should
be noticed is the common mourning cloak vanessa (/uvan-
essa antiopa) which is interesting because of its very wide
distribution and its very great hardihood. It is said to occur
over practically all of the northern hemisphere from 30° to
the Arctic Circle. It occurs here in the winter time, hiber-
nating as an adult and has been found secreted in hollow
logs, bridges, and in almost any sheltered place, and if
taken indoors will revive and feed on sweetened water
quite readily. They begin to fly quite early in the spring.
It is double-brooded—the eggs deposited in early spring
produce larvee which mature in midsummer. They breed
on willow particularly and the larve are dark-colored and
rather conspicuous. They also infest poplar, elm, and
dogwood, but willow seems to be the favorite. The chrysalis
is attached to the twigs of these plants and the adults
appear in midsummer. These adults deposit eggs and a
second generation appears in autumn which hibernates and
carries the species over winter. In some places they have
an economic importance, but ordinarily they are not a
serious pest, and the butterfly is such a handsome species
that it may be counted as deserving immunity.
CHAPTER IX
ORDER DIPTERA.
Ths is a very large and important order and includes a
number of important economic species such as the house
fly and the mosquito. ‘They are separated from all other
insects by the wing structure, the front wings only being
fully developed as means of flight and the ‘second wings
being modified into knob-like structures which seem to hae
some use in sustaining the insect in a certain position.
They vibrate but cannot serve any distinct function as a
means of flight. They are modified wings. This is a case of
specialization, reduction in size. This is codrdinated with
the centralization of the nervous system. There is distinct
metamorphosis whose stages are usually sharply marked.
The larve are usually called maggots, those of the mosquitoes
“wrigglers.”” The larvee occur in all manner of situations.
Some are aquatic, some terrestrial, some subterranean, etc.
The group is separated mainly by larval characters—one
group including mosquitoes and gnats, another the more
specialized flies. The larva contracts and the skin hardens
and forms a pupal case whose end splits off like a cap.
The Orthorapha, mosquitoes and gnats, are the less
specialized or the more primitive group.
Of the groups in the first series the mosquitoes (Culicide)
are the most in evidence, if not the most important, and
are receiving more attention lately because of their asso-
ciation with the transmission of various diseases. The
mosquito is not a single species. There are a great many
different species and they differ a great deal in life history
and habits and in their relation to disease. The most general
statement to be made regarding their cycle is that the eggs
( 248 )
MOSQUITOES 249
are deposited on the surface of the water and perhaps in
some species in mud or damp earth. The larvee are essentially
ee
S
YE
Fic. 191.—Anopheles maculipennis: male. Fic. 192.—-A nopheles maculi-
Carrier of malaria. (Harrington.) pennis: female. Carrier of
malaria. (Harrington.)
Fig. 193.—Anopheles punctipennis: male. Carrier of malaria. (After
Howard.)
250 ORDER DIPTERA
aquatic and air-breathing, with the trachea opening at the
end of the abdomen. The pupe are also aquatic but keep
near the surface and spiracles open near the head. The pupa
case splits on the dorsal side and the mosquito rests on the
Fig. 194.—Anopheles punctipennis: female. (From Howard,
Div. Ent., U. S. Dept. Ag.)
surface of the water until its wings are dried enough for flight.
One species has been observed mihose eggs May remain over
winter in mud, and hatching and development depends upon
the presence of water. Mosquitoes breed in minute quanti-
MOSQUITOES 251
ties of water if they have it for a few days, and especially
those that are more common about towns depend on small
pools, tanks, and rain barrels rather than larger bodies of
water. More breed in small pools than large, because there
are usually no fishes in the small pools. They fly for a few
rods but for no extreme distance—one-half mile or a mile.
Fig. 195.—Culex teniorhynchus: female showing the short palpi which
distinguish Culex from Anopheles; toothed front tarsal claw at right—
enlarged. (From Howard, Div. Ent., U. S. Dept. Ag.)
They may be transported, but most annoyance comes from
those bred close at hand. The connection between mosqui-
toes and malaria has been fully established. The parasite
seems to be dependent upon two distinct hosts. Unless
there is a case of malaria in the near vicinity they cannot
communicate it to another. The relation of mosquitoes to
yellow fever has also been worked out very carefully. One
202
ORDER DIPTERA
Ak
ee
—
Fia. 196.—Resting positions of Culex (at left) and Anopheles (at right)—
enlarged. (Redrawn from a rough sketch published in the British Medical
Journal.) (From Howard, Div. Ent., U. 8S. Dept. Ag.)
\
Fic. 197.—Yellow-fever mosquito (Stegomyia fasciata): A, male; B,
female. (After Howard.)
GALL GNATS Zoo
striking thing is the discovery of the immense number of
species of mosquitoes. There have been many new species
discovered in the last few years.
Gnats (Chironomide).—Gnats are related to mosquitoes
and are interesting partly because of their close resemblance
to mosquitoes and partly because they occasionally multiply
so as to cause annoying contamination of reservoirs or
obstruction in water tanks. The antenne are plumose as
in the mosquitoes but the mouth parts are different. The
larve are more distinctly aquatic than the mosquito larvee
can survive down in the water without coming to the sur-
face for air. Some live in mud—slender red, worm-like crea-
tures. One species is quite plentiful in the Northern States
especially near lakes and sometimes as abundant as the May
flies.
Gall Gnats.—The next group is the one including the gall
gnats. It is a very important family with two or three very
important species. The most conspicuous of the galls
produced by these is the cone gall produced on willow trees—
the pine cone willow galls. These are the result of the work
of the larvee of the gall gnats. They are made up of a series
of leaves which overlap in the form of a pine cone. ‘These
correspond with the leaves that would have come out along
the twig had it grown out normally. The leaves are devel-
oped close together and the larve of the gall gnat is found
in a little cell in the centre of the gall. It issues in the spring
and deposits its eggs in the willow buds before the twigs
have started to grow, and the larvee hatch and form the galls
by feeding. There are a good many things in these galls
besides these larvee. Other insects find them a convenient
shelter, and other insects deposit eggs there. The tree
crickets are an example of this. These may be a little mis-
leading but they have nothing to do with the formation of
the gall. The pine cone gall is most conspicuous. There
is another species which simply produces an aborted growth
that looks like Brussels sprouts.
The other species in this family to be mentioned are the
clover and wheat midges and the Hessian fly.
254 ORDER DIPTERA
Clover-flower Midge (Dasyneura leguminicola).—The clover-
flower midge lives within the heads of clover and feeds upon
the clover bloom and seed. Its life-cycle is adapted to the
~
{ « ~
z)
\s
f
;3
Fic. 198.—The clover-flower midge (Dasyneura leguminicola): a, enlarged
dorsal view of male with scales denuded; b, head; c, genitalia; d, antennal
joints, more highly magnified, to show structure; e, tarsal claw; /, f, forms
of scales. (From Riley, Div. Ent., U. 8. Dept. Ag.)
blooming of the clover, so that the larvee appear at the proper
time for feeding upon the clover seed. There are two fairly
distinct broods each season, the first brood of larvae develop
HESSIAN FLY 250
in early summer and mature in midsummer, the larvie issuing
from the clover heads and pupating in the ground and the
second brood appearing later in the summer and depositing
eggs which produce the second generation of larvee which
develop in the later blooming clov er. These hit the crop
of clover grown for seed. They mature with the late autumn
and either maggots or the mature puparia would be found
during the winter time and the larve particularly which are
caught before they have completed their growth may be
included in clover seed. The fully developed larve pass
into the pupa stage at the surface of the ground. It is
doubtful if the midge can be transported from one place to
another by means of the clover seed. Just how it is intro-
duced into remote districts is uncertain. Its means of loco-
motion is by its own flight. It is pretty generally dispersed
throughout the portion of the country where clover is now
grown. The means of treatment would lie more in the
direction of cutting the clover at the time to cut short the
growth of the larvee—a little earlier cutting of the clover,
catching the larvee before they have issued from the clover
heads.
Hessian Fly (Mayetiola destructor)—The Hessian fly is
the most destructive of the family. It is an introduced
species and was first described from materials.in this country
in 1820. It probably originated where wheat did. It was
never described scientifically until by Say. It had been
known as a destructive insect earlier than 1820 and the
name was given to it about the time of the Revolution, when
the Hessian soldiers were in this country, either because the
insect was thought to have been introduced by them or as
an obnoxious name. The name was adopted over the entire
English-speaking world. The evidence that it is an old-
world species is from its food plants and that it spreads
from one centre. There are a number of other evidences.
Its natural food plants seem to be limited to wheat, rye, and
barley, though there is a question as to barley. It was
proved by a Frenchman that it does not occur on oats. At
one time it was thought to breed in various grasses, but later
bo
56 ORDER DIPTERA
studies show that this was not the true Hessian fly. If any
attempts are made to control it by rotation of crops its
restriction of food plants should be well known. Its life-
aycle is quite similar to that of the clover-flower midge and
it has become very distinctly adapted to the crop it infests.
Any great change in ordinary methods of raising wheat
would likely prove destructive to the insect. The winter is
Fic. 199.—The Hessian fly (Mayetiola destructor): adult female—much
enlarged. (After Webster, Div. Ent., U. S. Dept. Ag.)
passed in the flaxseed stage—the puparium stage. The
larval skin shrinks and forms a tough, dark brown covering
about the size and shape of a flaxseed. Within this there
is formed a real pupa that has the outline and features of the
adult insect. There is a distinct metamorphosis. These
* hibernating puparia give rise in early spring to adult midges
that deposit eggs on the stems and leaves of wheat plants—
HESSIAN FLY 257
winter wheat. In spring wheat regions the flies appear
at about the time of the coming up of the wheat and deposit
eggs on it. There is not necessarily much difference in the
time and method of deposition except that those on winter
wheat are apt to be a little higher on the stems and farther
from the ground. ‘These burrow into the stem in such a
way as to cause weakening of the stalk, which is apt to bend
Fria. 200.—The Hessian fly: adult male—much enlarged. (After
Marlatt, Div. Ent., U. S. Dept. Ag.)
and break as it approaches maturity and falls to the ground,
so that it cannot be harvested. Sometimes only 1 or 2 per
cent. of the field will be infested and in other fields one-third
or one-half of the crop will be lost. As the wheat matures
the larvee mature and change to the flaxseed stage and
remain protected between the sheath and the stem of the
plants down near the ground. Sometimes they are high
17
JR
Zo ORDER DIPTERA
enough to be cut off and carried with the straw when the
wheat is harvested, but more commonly are left in the
HNIT
Fia. 201.—Egg of Hessian fly—greatly en- Fie. 202.—The Hess-
larged; section of leaf of wheat, at right, ian fly: larva before“ flax-
showing eggs as usually deposited, less seed’”’ is formed—much
enlarged. (After Webster, Div. Ent., U. S. enlarged. (Webster, Div.
Dept. Ag.)
Ent., U. S. Dept. Ag.)
Fig. 203.—The Hessian fly: larva Fia. 204.—The Hessian
taken from ‘“‘flaxseed,’’ much enlarged fly: puparium or “‘flax-
with ‘‘breast-bone’’ still more enlarged seed,’”’ much enlarged.
at right. (After Webster, Div. Ent., (After Webster, Div.
U. S. Dept. Ag.) Ent., U. S. Dept. Ag.)
stubble. They survive the midsummer in this condition and
are apparently dependent more or less on conditions of
HESSIAN FLY 259
temperature and moisture. They come out in the fall and
are ready to deposit eggs on wheat plants accessible in the
Fie, 205.—The Hessian fly: pupa taken from ‘‘flaxseed,”’ greatly
enlarged. (After Marlatt, Div. Ent., U. S. Dept. Ag.)
Fig. 206.—Injured plants and flaxseeds. (Photo by Ohio Exp. Sta.)
260 ORDER DIPTERA
autumn. ‘The eggs deposited in the autumn give rise to larvee
which develop and pass into the flaxseed stage to hibernate.
If they are accelerated in their development and are provided
with food material—volunteer wheat—there may be one or
more extra broods in the summer. As high as five or six
extra broods were observed by Marchal. There are ordi-
narily two broods adjusted to the occurrence of young wheat
plants. One important thing is the distribution of the
species by means of the shipping of infested straw. This
must be the main or only means by which the species is
taken from one country to another. It has been introduced
into most wheat-growing countries of the world. The
natural distribution of the species is limited to about 20
miles a year. Flight aided by the wind might carry it some
little distance. For local measures attention to the stubble
is one of the most important things. If it is thick and dry
enough to burn over during midsummer, it can be destroyed
in this manner. Plowing under very deeply is another
method but must be done early enough to bury the stubble
before the flies have issued. The most generally practised
method, and most highly recommended, is to adjust the time
of planting so as to avoid the period of egg deposition. If
the time of planting wheat can be deferred for a week or two
after the appearance of the flies, it will escape. Flies will
not deposit eggs on the bare plowed field. If the wheat comes
up after the flies have issued and passed the egg-laying period,
it escapes attack. For the Central States the time of appear-
ance has been pretty definitely determined, and it has been
shown at what time wheat can be planted with the greatest
security. For the latitude of Columbus, Ohio, it is about
the first of October. It is possible to plant trap crops so as
to catch the flies as they appear and the whole crop can be
plowed under after the eggs are deposited on it. This is not
particularly popular. If planting is done with reference
to temperature and to different seasons, results will be better.
Hot, dry weather seems to prevent the issuing of the flies.
Family Simuliide— The family Simuliide@ includes the
black flies and buffalo gnats. These constitute extremely
FAMILY SIMULIIDA 261
injurious pests and occasion many losses to agriculturists,
so that they deserve a paragraph at this point, although for
most of their existence they have very little in common with
farm life. They have had an added interest in recent years
on account of the effort to prove them the carrier of the
disease known as pellagra, but proof of such a connection
is still wanting. The adults are short, small, thick-bodied
insects; the thorax especially heavy, and the humped appear-
ance of the whole body has given rise to the name buffalo
gnats. They are all small species, scarcely any of them a
quarter of an inch inlength. The larvee are distinctly aquatic,
usually living in swiftly running water. They are so fully
adapted for aquatic life that they attach themselves by
silken threads to submerged objects and depend for their
food upon minute organisms floating or swimming in the
water. The pupal stage is also passed under water, a thin
cocoon being spun upon the under side of the leaf or other
submerged object. When the adults emerge from these they
rise rapidly to the surface of the water, the wings expanding
promptly, and they are ready for flight almost instantly.
At times they occur in enormous swarms and the females
are very blood-thirsty, attacking all kinds of warm-blooded
animals, sometimes with very disastrous results. In the
Northeastern States and in parts of Canada, especially in
Labrador, there is a species known as the black fly. They
occur at times in such abundance as to make it practically
impossible to remain out of doors, and domestic animals will
seek any possible shelter in order to avoid the attacks of the
insect. In the Southern Mississippi Valley there are two
common species which have been studied in detail. One of
these, the turkey gnat, is said to make its attacks very gen-
erally upon poultry, although it is not limited to these animals.
The other species which is credited with the greatest
amount of loss in the Mississippi Valley region may be
considered somewhat in detail and as a representative for
the family.
Southern Buffalo Gnat (Simuliwm pecuarum, Riley).—The
‘investigations of 1885-86-87, which have been reported very
262 ORDER DIPTERA
fully in the Department publications, and from which the
statements here made are mostly compiled, have shown
that the extent of territory invaded by these insects is much
greater than formerly supposed. It may be stated to com-
prise, in the worst years, the whole of the Mississippi Valley
from the mouth of the Red River, in Louisiana, to St. Louis,
Mo. All the adjacent land to the many rivers and that
empty from the east and the west into the Mississippi River
Fic. 207.—Simulium pecuarum: larva—enlarged. (From Annual
Report of Department of Agriculture, 1886.)
is invaded by swarms. They are driven about by the wind
and reach points far away from their breeding places.
The extent of the losses due to this species has already
been stated, though it is, of course, impossible to separate the
losses due to this species from those caused by the turkey
enat. In a general way the latter may be said to be more
destructive to poultry, while the attacks of this species are
more particularly directed against the larger domestic
animals.
FAMILY SIMULIIDA 263
The larva is not differeint in general appearance from that
of other species. The annexed cut (Fig. 207) shows it con-
siderably enlarged and will make a detailed description
unnecessary. It is translucent when living; the body in
a Bee etoa.
C
Fic. 208.—Simulium pecuarum: head of larva: a, beneath; b, side;
c, above—greatly enlarged. (From Annual Report of Department of Agri-
culture, 1886.)
b
Fig. 209.—Simuliwm pecua- Fig. 210.—Simulium pecua-
rum: pupa—enlarged. (From rum: female, side view—en-
Riley.) larged. (U.S. Dept. Ag.)
some individuals is without markings, while in most it is
distinetly marked with dark cross bands on the back in the
middle of the joints, while at each side is a white space;
the under side is more or less irregularly spotted with brown.
264 ORDER DIPTERA
The head is yellowish-brown, nearly square, horny, and
marked as in the figure (Fig. 208).
The tip of the abdomen is crowned with rows of hooks,
and on the upper side of the abdomen is the set of breathing
organs, which have been mentioned heretofore.
The larve are found more particularly attached to sub-
merged logs, wholly or partly submerged stumps, brush,
bushes, and other like objects in the larger creeks and bayous
of the region to which they are common.
ee Pm Ate
TL)
oe
Fie. 211.—Simulium pecuarum: head of male at right; head of female
at left—greatly enlarged. (From Annual Report of Department of Agri-
culture, 1SS6.)
When fully grown the larvee descend to near the bottom
of the stream, sometimes eight to ten feet, to make their
cocoons.
The cocoon upon these leaves is conical, grayish or brown-
ish, semitransparent, and has its upper half cut square off,
more or less ragged, as if left unfinished. Its shape is irregu-
lar, the threads composing it very coarse, and the meshes
rather open and ordinarily filled with mud. They are not
always fastened separately, but frequently crowded together,
not forming, however, such coral-like aggregations as in some
of the Northern species. The larva in spinning does not
leave its foothold, but running in the centre of its work, uses
FAMILY SIMULIIDE 265
its mouth to spin this snug little house. In it, it changes to
a pupa, which has its anterior end protruding above the rim.
They remain in the pupa state but a short time. Both
larval and pupal skins remain in the pouch for some time.
The adult fly on emergence from the pupa rises quickly to
the surface, and the wings expanding almost instantly, it
darts away.
The time of the appearance of the swarms is regulated by
the earliness or lateness of the spring, and consequently it
is much earlier in the southern parts of the Mississippi
Valley. As a rule they can be expected soon after the first
continuous warm weather in early spring. In 1885 the first
swarms were observed in Louisiana March 11, in Mississippi
and Tennessee May 1, and in Indiana and Illinois May 12.
Horse Flies ( 7'abanid@).—Horse flies are pretty well known
and quite important economically. They cause annoyance
to domestic animals and to man. They are not credited with
carrying any disease, but seem to be well adapted to such a
performance. They are aquatic in the larval stages so far
as the larvee have been studied, and the larve are carnivorous
and seem to feed on a variety of aquatic life, dead or alive.
They pass through pupa stages in the mud or deeper in the
marshes of pools and ponds. The adults are very active
and swift flying. The eyes occupy practically the whole
head and are composed, especially in the males, of an enor-
mous number of facets. The females are the biting members
of the family, having the mouth parts much more fully devel-
oped. The males live on plant juices, but probably do not
feed extensively in the adult stage. The females seem quite
blood-thirsty, though perhaps this is not a necessary food.
The eggs are deposited in little clusters or masses on aquatic
plants, usually just above the surface of the water, so that
the larvee on hatching at once enter the water. The insects
of this group are much more abundant where there is an
area of water surface to provide the water habitat. The
females gather to the water probably to secure water in con-
nection with the deposition of the eggs, and a Russian ento-
mologist proposed the plan of putting kerosene on the surface
266 ORDER DIPTERA
of the pools to destroy the adult females, and this seems to
have been very successful. The trouble in this is that the
kereosene kills other forms of life which are not obnoxious.
There are several species in this locality. ‘The species com-
mon about horses are the green heads and the big black flies.
The green heads sometimes cause a great deal of trouble.
The remaining families of the order come in the suborder
Cyclorhapha. This group includes an immense number of
flies, many different families and some of the families an
immense number of species.
Fic. 212.—Tabanus atratus: a, larva; b, pupa; c, adult. (After Riley.)
The first important family in the group is that known as
the Syrphide. This one family presents about as great a
variety of life, habit and conditions as any in the order.
There is everything from aquatic to arboreal species in the
larvee. The rat-tailed forms which live in liquid have a long
tube extending to the surface of the liquid. Another species
occurs on trees. The more important economically are
the ones that feed on plant lice, and these are a most impor-
tant factor of control. Many species mimic members of
other groups of insects. Some look very much like wasps,
FAMILY OESTRIDA 267
others like bees, and the rat-tailed species (Fristalis tenax)
looks like a drone bee. .
Bot Flies (Oestrid@).— The bot flies are parasitic in various
mammals, occupying the body tissues and primarily the ali-
mentary tract. The adults are bee-like, with rounded heads
and small eyes, and are hairy. The antenne are sunken into
little pockets or pits in the front of the head, and the mouth
parts are aborted. The adults do not feed. The females are
3 ;
ea
ie
Fic. 213.—Horse bot fly (Gastrophilus equi): a, egg, enlarged; b, nat-
ural size; c, larva, newly hatched, enlarged; d, more enlarged: e, oral
hooks; f, body spines; g, mature larva, twice natural size; h, adult female.
(Author’s illustration, Bur. Ent., U. 8. Dept. Ag.)
the more commonly seen and they deposit their eggs on the ani-
mals that are to serve as hosts for the larvae. The males gener-
ally remain in shady places among grass, etc., so that they are
much less likely to be observed. The larvee seem to have
adjusted themselves to the parasitic condition from a more
primitive condition, possibly that of living in organic matter
of some kind. It seems most likely that some form with
habits perhaps like the blow fly might in some cases deposit
268 ORDER DIPTERA
eggs in such places that the larvee would survive and the
habit gradually acquired of living within the host tissues.
They reach maturity without destruction of the host form
and the habit gradually becomes fixed. This habit is now
definitely fixed among all the species of the family and
they are restricted to mammals as hosts. Some infest the
alimentary canal, some the nasal passages, some the tissue
beneath the skin. The larvee as parasites have undergone
considerable modification from the primitive forms. They
are usually provided with rows of spines or sharp spurs that
assist their movements when they leave the host forms and
for those that live in the alimentary canal there are hooks,
modifications of the mouth parts, that serve to attach them.
They may feed to some extent upon the secretion of the host,
but most of the nutrition is absorbed through the body walls.
The Horse bot fly (Gastrophilus equi) is one of the best
examples and probably represents most nearly the primitive
condition for thefamily. The adult occurs through the middle
and last of summer and the eggs are deposited on the hairs of
the horse, small yellow eggs glued very firmly to the hairs.
In depositing the eggs the female darts toward the animal
and thrusts the egg against the hair without alighting. The
abdomen is thrust forward under the body. A glutinous
secretion is discharged with the egg and binds and hardens
almost immediately. The eggs are very thick-walled with
chitinous walls and have a little operculum or cap at the end
of the egg which is easily detached after a certain stage in
the development. The time for hatching varies from three
days to forty, but usually ten to fifteen days after deposition.
Before that time they are hatched with a great deal of diffi-
culty, and the larve are rather inactive. After fifteen to
twenty days the activity begins to diminish. The majority
die if not hatched in thirty to forty days. They do not
hatch without the assistance of moisture, friction, and
warmth to stimulate the larve. With a little moisture and
friction the cap slips off easily and the hooks of the larva
fit it to attach itself immediately to the tongue or other part
of the body of the horse. The egg shells remain on the hair
FAMILY OESTRIDA 269
after the hatching occurs. The time for the hatching of the
eggs is rather important with regard to the treatment. of
the animal. It has been studied pretty carefully. Different
statements as regards the period of incubation may mean
different species observed. Egg deposition may go on until
quite late in autumn, but is usually at its height about
August or early September. The activity is retarded by cold
weather and the larvee may survive longer then. The method
by which they get into the stomach of the horse is by the
horse licking itself or some other animal on which there are
eggs. At first they are long and slender but after attachment
in the stomach become thicker and fasten themselves by
hooks to the stomach and remain there through late autumn
and winter and early spring. They are sometimes very
thickly set in the stomach of the horses. They must cause
considerable interference with the activity of the stomach,
and if massed together at the pyloric orifice may act as an
obstruction. The effect on the animal is in some cases quite
evident. The damage is doubtless different in different
animals. The worst infested are those that have been in
pasture. When they have completed their growth in the
stomach they loosen their hold and pass out of the stomach.
They burrow into the ground and pupate and remain in this
condition several weeks—six or seven—and issue from mid-
summer to early autumn. There is one generation a year
and the longer period is spent in the body of the animal.
Treatment for the larvee is rather severe. They may be
killed with turpentine, but care must be used not to injure
the horse by an overdose. The means of prevention are
indicated by the life-cycle—condition of the egg and length
of time it may develop. If eggs are removed every week or
ten days there is no danger of serious infection. Horses
curried regularly are not apt to be infested. They may be
shaved off, and this is the most ready means of preventing
the infection. Washes could be used to kill the larvee
kerosene, carbolic acid, ete.
There are three or four species of this parasitic genus in
the horse, but no other so common as Gastrophilus equi.
270 ORDER DIPTERA
They cause a good deal of annoyance. One is called the chin
fly (Gastrophilus nasalis), which lays eggs on the jaws.
Another, the red-tailed bot fly (Gastrophilus hemorrhoidalis),
also deposits eggs in the vicinity of the mouth.
Bot Fly of the Ox ( Hypoderma lineaia).—The bot fly of the
ox illustrates another method of development, but seems
to have been derived from that of the one occurring on the
horse. It is known in some parts of the country as the
Texas heel fly. It occasions a great deal of loss to the cattle
Fic. 214.—Hypoderma lineata: female—natural size indicated by side
line. (From Insect Life.)
industry. The larve perforate the hides. They develop
under the skin and on maturing pass through the skin,
leaving a lot of openings. Such hides are docked one-third
in the market. Eggs are laid on the hairs of the legs, and as
he found none on the hairs of the back, Dr. Curtice concluded
that the larve were taken into the mouth and travel by way
of the esophagus and through the tissues of the thoracic
region up through the tissues of the back as their normal
route. The puncture is made after the larva is under the
FAMILY OESTRIDA 201
Vig. 215.—Aypoderma bovis—enlarged. (After Brauer.)
Fic. 216.—Piece of warbled hide—warbles about half size. (After
Omerod.)
272 ORDER DIPTERA
skin and some time before it is ready to issue. The adults
appear quite early in the season and the larve in the backs
of cattle are never seen until in the winter time—January
first to March or April. They cause the muscles to have a
jelly-like consistency. They injure the cattle in regard to
growth and to milk conditions. The annoyance of the flies
att
ey Jars A a? at
A UEC AAS, a
Fic. 217.—Hypoderma lineata: a, eggs attached to hair; 6, c, d, dorsal,
ventral, and lateral view of egg; e, embryonic or first larva, as seen in egg;
f, g, mouth parts of same enlarged; h, anal segments of same still more
enlarged. (From Insect Life.)
when they deposit eggs and also the injury caused by their
presence in the back of the cattle is in England estimated
at about $5.00 a head. Eggs are attached to the hairs, and
the larvee, according to Curtice, pass into the mouth and
through the esophagus and through its walls into the adja-
cent tissue and migrate by slow degrees to the dorsal portion
of the body, finally reaching the subcutaneous tissue along
FAMILY OESTRIDH 273
the backbone, about six or eight inches from it and between
the shoulders and the hips. The time of the appearance
in that location and the time when the larvee are taken into
Fic. 218.—Hypoderma lineata: ovipositor of female: a, from side; b,
tip, from below—enlarged. (From Insect Life.)
Fic. 219.—Hypoderma lineata: second stage of larva from esophagus:
a, larva; b, enlargement of cephalic segments, end view; c, mouth parts;
d, enlarged end view of anal segment, showing spiracles and spines. (From
Insect Life.)
18
274 ORDER DIPTERA
the mouth are separated by quite a period. Curtice claims
to have found larvee at all points between these two positions.
This cannot be purely accidental. More recently an Irish
investigator has reached the conclusion that the larvee bore
into the skin and migrate to the wall of the esophagus from
which point they travel to the position under the skin of the
back. The adults emerge in early summer, in Texas as
{FES
ie,” tiie Ree"
al
Fig. 220.—Hypoderma lineata: a, second stage of larva from back; 6b
and c, enlargement of extremities; d, ventral view of third stage with
details of extremities at e and f; g, dorsal view of mature larva with enlarge-
ments of anal spiracles at h; 7, the same, lateral view. Natural size indi-
cated by side lines. (From Insect Life.)
early as May, in northern States May or June. The larve
are pretty well grown by February, and by early March they
have practically reached maturity and the grubs issue
during March and early April, drop into the ground and
pupate and remain in this stage for five, six, or seven weeks,
and the adults come on from May to early June or the first
of July.
The European species which has now been studied with
FAMILY TACHINIDA 275
special reference to its mode of introduction is believed to
follow the same method, but Miss Ormerod persisted in the
belief that the eggs were deposited on the back and that the
larvee bored through the skin, and claims to have seen chan-
nels through the skin through which the larve travelled. It
is not likely that there would be this difference in the two
species. This species causes a great deal of loss in the old
world. ‘The one method available for controlling either of
these species is the destruction of larvee during the late
winter and early spring when they are conspicuous along
the back, and the method of extermination of the species
would be to have all animals examined and all the grubs found
destroyed. This is feasible theoretically, but impossible
practically. They do not migrate far, and any stock owner
can by close attention secure a large measure of immunity
for his own herd. Co6peration would secure a more extended
extermination.
Sheep Bot Fly (Oestrus ovis)—The sheep bot fly illustrates
another method of development. It deposits eggs or newly
hatched larvee in the nostrils of sheep and these work their
way up the passages. This entrance occurs during summer
time and the development of the larve goes on through fall
and the larvee work their way back in spring and pupate in
the ground and the flies issue in midsummer. They cause
the greatest irritation and most serious symptoms occur
during the time the larve are working themselves back.
The sheep sneeze, etc., and sometimes show a dizziness or
stagger. They may be cut out of the frontal sinuses but the
cost of the operation is too great for general use. Preven-
tion consists in avoiding the deposition of eggs in the nos-
trils. Applying tar to the noses is one method, and another
method is by furnishing plowed places or dusty places so that
the sheep can bury their noses when the flies try to deposit
eggs, or by giving the sheep a shed, as the flies are active
in the sun and not in the shade.
Family Tachinide.—The family Vachinide has a very
important economic position on account of the large number
of species that are parasitic upon destructive insects. The
276 ORDER DIPTERA
adults appear much like the house flies or the stable fly but
have usually numerous prominent bristles and spines, the
bristles (arista) of the antenne lack the fine hairs which are
characteristic of most of the Muscidae.
These insects show some very striking adaptations in their
parasitic life, some of the species depositing their eggs
directly upon the bodies of the caterpillars which are to be
the hosts of the larvee. The larvee on hatching bore at once
into the caterpillar and develop within its tissues. In cer-
Fig. 221.—Euphorocera claripennis, a parasite of the alfalfa caterpillar:
adult and enlarged antenna of same; puparium—enlarged. (From Howard,
Bur. Ent., U. S. Dept. Ag.)
tain species the eggs are laid upon the leaves and depend
for their entrance to a host insect upon the leaf being eaten
by some herbivorous form and in this case it would seem as
if there would be some chance of the eggs being crushed or
the larvee being destroyed in the process of swallowing. In
one rather remarkable form the eggs are evidently deposited
within the burrows of wasps which are stored with spiders.
The Tachinide follow the wasps as they drag their victims
to the burrow and when the wasp enters they no doubt
FAMILY MUSCID& PALE
deposit their eggs upon the spider, the larva feeding upon
the food intended for the wasp larva or possibly upon the
wasp larva itself.
The typical Muscid flies (Muscide@), house fly, blow fly
screw-worm fly, all live in organic matter in a state of decay,
and all of them show very rapid rate of development, the
larve acquiring their growth in a few days’ time, though
longer time is usually passed in the pupa stage. The adults
may live for a long time. House flies, for example, conceal
themselves about houses and suryive the winter, possibly
also as pupe, and deposit eggs which start the summer
Fie. 222.—Common house fly (Musca domestica): puparium at left;
adult next; larva and enlarged parts at right. Allenlarged. (After Howard,
Div. Ent., U. S. Dept. Ag.)
generations which follow each other with a great deal of
rapidity. Twelve to fifteen days is all that is required for
the complete cycle of many of the species. They are scaven-
gers and in this may be looked upon as beneficial. They
present also certain dangerous aspects as carriers of disease,
especially typhoid, and deserve all the opposition they are
receiving.
The screw-worm fly deposits eggs occasionally in the
nostrils of individuals, and in the case of wounds of animals
the larvee work into the living tissue. It causes losses in
cattle industry in the South.
278 ORDER DIPTERA
The house fly (Musca domestica) is perhaps the most
universal, and occurs wherever civilization extends, and
presents an Important feature in its possibilities of carrying
disease germs. One of the first cases establishing this con-
Fig. 223.—The common house fly: a, full-grown larva; 6b, one of its
anterior spiracles; c, antenna; d, hind end of body showing anal spiracles;
e, side view of head; f, head from above; g, head of young larva; h, eggs.
All enlarged. (From Howard, Div. Ent., U. S. Dept. Ag.)
nection was that determined during the Spanish-American
war, where the source of the typhoid was traced to house flies.
It is known to serve as a carrier for tuberculosis, dysentery
and other diseases. Flies breed in filth, especially horse
manure, the eggs requiring a few hours to hatch, the mag-
FAMILY MUSCIDA 279
gots from four to six days to grow, and pupation six to eight
dle: s, so there may be many generations in a summer. Pro-
tection may be readily eained by community effort. Their
flight is sufficiently restricted to make individual effort on
a farm well worth while, even if some nearby farms are neg-
lected.
Fig. 224.—The common house fly: a, pupa removed from puparium;
b, hind end of body of larva in second stage; c, anal spiracles of larva in
first stage. All enlarged. (From Howard, Div. Ent., U.S. Dept. Ag.)
Horn Fly (Ha@matobia serrata Rob.-Desv.).—In the intro-
duction and rapid spread of this insect we have an excellent
illustration of the importance of giving attention to the
injurious insects of other countries and of taking all possible
means to prevent their importation.
The species in hand has been a common insect in Europe,
and with other members of the same genus recognized as a
troublesome insect, though apparently no careful study of its
life history has been made there.
280 ORDER DIPTERA
It was first noticed as troublesome to cattle in this country
in 1887, and while we cannot say with certainty just when
it was introduced, we may be pretty sure that it was during
the year 1886, or at most not earlier than 1885. It is even
possible that it may have been brought over in the spring of
1887, as its powers of reproduction are such that a few weeks
would suffice to make it a conspicuous pest in a limited
area.
Within two years from the time it was first recognized in
serious numbers it had become so numerous and had spread
over so large a region that it was made the subject of a
very careful and successful study by Messrs. Howard and
Marlatt of the Division of Entomology. The results of
these inv estigations were published in Insect Infe (vol. ii, p.
93) and in the Annual Report of the Commissioner of Agri I-
culture for 1889.
As to its introduction and spread in America, all accounts
agree in placing the first serious occurrence of this insect in
the vicinity of Philadelphia, and it appears probable that
it was at that port that the flies first landed.
From there as a centre it spread in all directions, though
at first mainly southward, and by 1889 it had covered most
of the State of New Jersey, portions of eastern Pennsylvania,
a considerable area in Maryland, and also a portion of
northern Virginia.
In 1891 it had been reported from New York, Ohio, Ken-
tucky, Georgia, Florida, and Mississippi, and in 1892 from
Connecticut, Massachusetts, Canada, Michigan, Indiana,
Iowa, Louisiana, and Texas.
The adults of the horn fly are about half as large as the
common house fly and very much like it in shape and color.
The accompanying figures will serve to distinguish it. The
larval stages are passed in from four to six days.
The pupa stage may last from five to eight or ten days, so
that the full time from egg deposition varies from ten to
seventeen days, estimated for the average as about two weeks.
As the flies doubtless begin laying soon after issuing from
the pupa stage, there is room for a number of generations
FAMILY MUSCIDA 281
during even a northern summer, probably from six to eight
being common.
For the destruction of the larvee, which is probably the
most effective way of preventing damage, two principles
have been established. The first involves the killing of the
maggots by introduction of some destructive agent; the
other, the prevention of their maturing by the rapid drying
marx de
Fic. 225.—Horn fly (Hematobia serrata): a, egg; b, larva; c, puparium;
d, adult in biting position. All enlarged. (From Riley and Howard.)
of the mass of dung which supplies their food. The use of
lime, as originally suggested in Insect Life, is a very effective
plan, and where not prohibited by expense, should be generally
adopted. Prof. Smith’s suggestion to spread out the drop-
pings of manure so that they may dry rapidly is applicable
during dry weather and in some localities is accomplished by
drawing brush across the fields, a method which must
282 ORDER DIPTERA
necessarily fail to be complete in its operation, but much less
expensive than the use of a shovel by hand.
The Stable Fly (Stomoxys calcitrans, Linn.).—The stable
fly is a well-known species which is widely distributed and a
familiar pest in many countries. Its bite is severe and it
causes a great amount of annoyance to cattle, horses and
other domestic animals, and is frequently very troublesome
to people working in places where it abounds. It is not
confined to stables or to the quarters of domestic animals,
but occurs frequently in shady places, groves and in dwell-
Fia. 226.—Stomoxys calcitrans: adult, larva, puparium, and details—all
enlarged. (From Howard, Div. Ent., U. 8. Dept. Ag.)
ings, especially in cloudy weather, and puts the occupants
to great inconvenience. Its bite is not poisonous, and aside
from the pain given and the possibility of it disseminating
disease, it is less injurious than some other members of the
group. When abundant, however, this annoyance may be
very great, and they all deserve attention. Indeed, it is
especially charged against this species that they have been
the means of transmitting glanders from diseased to healthy
horses, and anthrax among cattle, a charge which appears
very reasonable from the fact that it inflicts a deep bite and
FAMILY MUSCIDA 283
does not gorge itself at a single animal, but may fly from
one to another in securing a meal.
In late years it has come into especial prominence as a
a carrier of disease. It was at one time thought to be the
‘arrier of infantile paralysis but this relation has not been
substantiated.
Fic. 227.—Muscina stabulans: a, larva; b, head below; c, head, side
view; d, thoracic spiracle; e, stigmatic plate; f, female; g, head of female;
h, mouth parts; 7, antenna. All enlarged, d, e, h, i, greatly enlarged. (Bur.
Ent., U. S. Dept. Ag.)
Tsetse Flies.—The tsetse flies have been notorious for a
long period as extremely serious pests in parts of Africa
and were described by early explorers because of heavy loss
to domestic and wild animals. In recent years these have
been connected with the transmission of certain kinds of
diseases, and are now looked upon as having a most impor-
tant bearing from the medical standpoint.
The species longest known, Glossina morsitans, has been
especially connected with loss among cattle, and horses.
Glossina palpalis which has been determined as the cause
84 ORDER DIPTERA
Fig. 228.—Glossina palpalis (xX 32), the carrier of the trypanosome of
sleeping sickness. (Bruce.)
Fria. 229.—Phormia terrenove—enlarged. (Howard, Div. Ent., U.S.
Dept. Ag.)
FAMILY MUSCIDA 285
of sleeping sickness in man has received perhaps the greater
attention in recent years.
It can easily be seen that the introduction of either of
these species into this country or even into South America,
with the opportunity for further distribution would be a
most serious menace, as there would be every possibility of
the introduction of the diseases which are associated with it.
These are perhaps examples of insects which deserve most
careful attention from the stand-point of possible exclusion,
and every effort made to learn their habits in detail and to
Fig. 230.—Lucilia cesar—enlarged. (Howard, Div. Ent., U. 8. Dept. Ag.)
avoid such means of transportation as might possibly serve
to transfer them to this country.- It is reported that such
an introduction has occurred in Australia.
Blue-bottle Fly (Lucilia casar).—The blue-bottle fly is
another species which is very abundant and almost uni-
versally distributed. Its attacks are made upon any avail-
able fleshy material such as carcasses of dead animals, fish,
and so on. The female deposits eggs on living animals that
have bruises or wounds or attractive points for deposition.
Sheep are especially subject to attacks of this sort. The
maggots of the flies do not limit themselves to the external
286 ORDER DIPTERA
parts but burrow into the flesh and may perhaps cause very
serious Injury.
The meat fly or blow fly is another species that falls in
the same group with regard to its habits, and against which
it is important to protect domestic animals.
Flesh Flies (Sarcophagide@).—Flesh flies are quite familiar
objects around houses, especially if there is any exposure of
Fic. 231.—The green-bottle fly: a, egg masses in cow dung; 6b, hatched
egg; c, a portion of the egg surface seen under the microscope; d, unhatched
egg; e, larva. All enlarged except a. (From Ann. Rept., U. 8. Dept. Ag.,
1890.)
fresh meats to attract them. The eggs are laid on meat by
preference and hatching occurs within a very short time, in
fact in some species it is stated that larvee are extruded from
the adult. Aside from their deposition upon meats, how-
ever, there is often a deposition upon fresh wounds or abra-
sions so that the larvee may make a serious attack upon
domestic animals or even human beings, if there is an oppor-
tunity for the attack. As a protection against this kind of
FLESH FLIES 287
injury it is important that all bruises or scratches should
be treated promptly so that domestic animals will not serve
as an attraction for the species.
Fic. 232.—Homalomyia brevis: female at left; male at centre, with
antenna enlarged; larva at right. All enlarged. (After Howard, Bur. Ent.,
U.S. Dept. Ag.)
ee ad
ma Cs eI I
Fic. 233.—Apple maggot (Rhagoletis pomonella): a, adult: b, larva or
maggot; c, funnel of cephalic spiracle; d, puparium; e, portion of apple
showing injury by maggots; a, b, and d, enlarged; c, still more enlarged;
e, reduced. (After Quaintance.)
In the genus Drosophila are a number of species, the
“pomace flies’ which feed principally upon decaying fruits.
288 ORDER DIPTERA
They are perhaps of slight economic importance as they do not
attack growing plants, but on account of the great ease with
which they may be bred in captivity they have been the
basis of some most important investigations concerning the
transmission of hereditary characters.
Another species is one that occurs as a pest in apples and
is known as the apple maggot (Rhagoletis pomonella), which
differs in its method of work from the codling moth larvee
in that the larvee work near the skin and make tunnels
through the apple. It punctures the skin and deposits eggs
inside. ‘This goes on during the summer and the larve
mature in autumn with the maturing of the fruit. They
hibernate as pup. This species occurs now and then in
Ohio, but is not so universally common as the apple worm.
It is more distinctly a northern species, sometimes a serious
pest in New England and parts of the States and Canada
bordering on the Great Lakes.
Family Hippoboscide.—The family Hippoboscide includes
sheep ticks, and forest flies. They have the wing structure
of the Diptera, suctorial mouth parts, but a very remarkable
method of reproduction. Instead of extruding eggs, they are
retained in the oviducts and developed through the larval
stage, being nourished by nutritive fluids. They are not
extruded until they are ready to pass into the pupa stage.
They take no nutriment as pupe after leaving the oviducts.
There is no food taken until as adults. There is an adapta-
tion for the parasitic habit. This is a different sort of adapta-
tion than is found in any other group of Diptera except the
succeeding group. They are different from any other group
of animals.
Sheep Tick (Melophagus ovinus, Linn.).—The sheep tick is
a common pest of sheep. It differs from the most of the
other members of the family in never possessing wings. The
head is small and sunken into the prothorax. The middle
portion of the prothorax is rather slender, contrasting with
the development of this region in the winged forms.
It is of a reddish or gray-brown color, about one-fourth of
an inch long, and easily detected when present in any num-
ORDER SIPHONAPTERA 289
ber on sheep. They never migrate from the original host
except it be to attach to another animal of the same species,
and probably the principal movement is that which occurs
after sheep are sheared, when the ticks tend to migrate to
lambs. On the sheep, if abundant, they may cause con-
siderable damage, indicated by lack of growth or poor
condition, and when massing upon lambs they may cause
great damage, resulting in the death of the victims if not
promptly relieved.
They are distributed over the world generally where
sheep are kept, and are too well known by sheep breeders
to make it necessary to emphasize the injury they may
cause. All breeds of sheep seem alike subject to attack,
but I know of no record of their occurrence upon other
animals.
While the ticks may be greatly lessened in number by the
vigorous use of pyrethrum—a most available remedy during
winter—the most practical plan to adopt, and one which if
thoroughly followed will make all others unnecessary, is to
dip the sheep each year after shearing.
A flock once freed from the pests will not be again infested
except by the introduction of infested animals: hence care
should be taken in making additions to the flock to free the
newcomers from parasites. It is also well to keep the sheep
for a few days. after dipping in a different inclosure from
that occupied before, to avoid possible infestation from any
stragglers that may have been caught on wool upon posts
or brush, and if the wool is charged with them when clipped,
it should be stored where the ticks could not easily return to
the sheep. The ticks cannot travel any distance inde-
pendently, and will soon die when removed from the sheep,
and proper care here will insure success.
Order SIPHONAPTERA.
Another order is the Siphonaptera. he fleas are wingless
or have the wings so aborted that they are practically wing-
less. Vestiges of wings may occur but are useless as organs
19
290 ORDER SIPHONAPTERA
of locomotion. The adults have suctorial mouth parts and
puncture various kinds of animals, sucking the blood for a
food supply. The larvee are slender and live in refuse and
rubbish, litter of dog kennels, etc., and when mature change
to a very distinct pupa stage and then to adult flea. The
pupa stage is like the adult in shape but the legs, etc., are
encased in the rigid pupa case. The hindlegs are specially
Fic. 234.—Cat and dog flea (Ctenocephalus canis): a, egg; 6, larva in
cocoon; c, pupa; d, adult; e, mouth-parts of same from side; f, antenna;
g, labium from below; 6b, c, d, much enlarged; a, e, f, g, more enlarged.
(After Howard.)
developed and their mode of progression is by leaping.
They occur on different kinds of animals, as the dog and cat,
and there are species that occur in houses, on squirrels,
rats, mice, and various mammals. It is mainly on the
smaller species of mammals, and one species occurs on birds.
One species attacks poultry. It buries itself in the skin
something like a jigger, though not so extreme in the extent
to which it will burrow.
CALAP"TE RX.
BEES AND WASPS.
Order HYMENOPTERA.
Tue Hymenoptera are in some respects the culmination
of the group of insects. They are specialized in several ways
but the species are all characterized by having the mouth
parts developed into both biting and sucking structures.
In some respects they seem more specialized than all other
orders and in some respects they seem less specialized than
the Diptera and Lepidoptera. As a matter of fact in the
evolution of the groups of insects there are several orders
that must be looked upon as having evolved along divergent
lines at the same time and none can be said to really outrank
the others. The Coleoptera, Diptera, Lepidoptera, and
Hymenoptera, all have a high degree of specialization. It
is better not to try to consider them as in the line of a series
of steps running up, but as parallel or divergent branches
from a general trunk, all of them extending to extreme
distances from the primitive stock.
The Hymenoptera have four wings, and these are provided
with rather few veins and pretty highly specialized in the
venation, and in a few groups the veins are practically
reduced to nothing. The mandibles are present for the most
part in the adult forms but are almost lost in some forms that
are fed by the adults in communal forms. They are both
mandibulate and haustellate. The larvee are usually footless,
fleshy, grub-like animals which depend on their food being
supplied for them in one way or another and are incapable
of moving about and securing their own food supply. This
represents a high degree of specialization and reaches its
(291)
292 BEES AND WASPS
culmination in the community habit of ants and bees. In
no other group except the white ants is there such develop-
ment of the community habit.
The pupa stage is generally included in the nest or cells
formed for the larval stage, and the forms are seen to be
quite highly specialized when the cocoon is cut open. The
larvee moult but the moults are not so conspicuous as in
exposed forms. The group exhibits quite a variety of
habit, some leaf-eating forms, some wood-boring forms,
some that develop in galls, many that are parasitic inter-
nally on other insects, and many store food in their nests,
such as spiders, caterpillars, ete. These are sometimes
stored in the ground, sometimes in mud cells, sometimes in
channels in the wood, sometimes in paper cells.
There are two large divisions, the Phytophaga, leaf-eating
or plant-feeding free caterpillar-like forms, and the Aculeata
which represent the other forms of the group, the larve of
which are dependent on a food supply provided by the adult.
The adults of this group have a sting.
The group Tenthredinide@ is a large family of leaf-eating
and gall-making insects and the typical ones being the
willow saw fly and the gall-making willow forms.
The willow saw fly (Cimbex americana) is one of the largest
species that we have. The adult is steel blue, the wings
smoky. It is quite conspicuous and lays its eggs on the
leaves of the willow along the midrib and principal veins of
the leaf. The larve hatch in a few days and grow during
the midsummer and are noticed as large yellow caterpillar-
like forms clinging to the twigs and leaves of willow par-
ticularly or sometimes also to elms and a few other kinds of
of trees. Some of the larvee have a prominent black dorsal
line. They coil themselves quite a little especially when
resting. While feeding the body is stretched out and they
cling by means of the prolegs of the abdomen as well as by
the thoracic legs. Prolegs are similar to those of the cater-
pillar. There are certain similarities with some of the very
generalized Lepidoptera and the prolegs might possibly be
taken to indicate some affinity. However, it is probably
ORDER HYMENOPTERA 293
better to look upon it as an independent development of a
similar structure based on similar habit. The number of
prolegs varies from twelve to sixteen. There are twenty-two
legs altogether. The saw fly larvae become fully grown by
the latter part of the summer and secrete themselves near
the surface of the ground, generally among dead leaves and
rubbish. They spin a quite strong silken cocoon with a
papery texture, somewhat more dense than is common for the
caterpillars of the silk-making moths. In this cocoon they
remain as larvee for quite a period. They finally pupate and
the adults issue in the spring and deposit eggs so as to
produce the summer generation of willow worms. ‘They
become of economic importance where the shade trees they
feed upon are of importance—willow trees, elm, etc. They
are parasitized and the cocoons are eaten by mice and so
kept down generally to a moderate number and are not
usually very destructive.
The pear slug (Hriocampoides limacina) occurs quite
commonly in orchards and attacks not only the pear, from
which it dervies its name, but also apple and other orchard
trees. The larva has a strict resemblance to the mollusks
called slugs, as the body is covered with a dense slimy secre-
tion which hides the segmentation and external features of
the body. They feed upon the surface of the leaves, just
leaving ribs and veins. The trees attacked often have the
appearance of being scorched by fire.
They are best treated by the application of arsenical solu-
tions, applied as soon as their work appears.
The American rose slug (Hndelomyia rose) is frequently
troublesome in its attacks on the leaves of rose bushes which
are stripped or skeletonized so that the bushes are rendered
quite unsightly.
Arsenical solutions can be used, or if these are not desired,
hellebore may be used for their control. Other species
affect gooseberry, strawberry and other such crops. Many
instances being of considerable importance.
The Uroceride are wood- or stem-boring species and
more specialized than most of the preceding family.
294 BEES AND WASPS
One form is particularly interesting, T’remea columba, or
horn tail or pigeon tremex. It has a rather peculiar shape
both in the larval and adult stages. The adult is an inch
or more in length and with a prominent ovipositor which
extends back about one-half inch from the back of the
abdomen; both larvee and insects are cylindrical, the result
of the boring habit. These adults appear in summer and
deposit eggs on the bark of different kinds of forest trees—
syeamore, maple, and others. The larvee burrow in, form-
Fic. 235.—Pear slug: a, adult saw fly, female; 6, larva with slime
removed; c, same in normal state; d, leaves with larve, natural size;
a, b, c, much enlarged. (From Marlatt, Div. Ent., U.S. Dept. Ag.)
ing tunnels through. the heart wood pretty well down into
the tree. Sometimes the trees are extensively perforated.
Boring continues in through the tissue of the wood till they
get their maturity and then they burrow out through the
bark. Pup are formed in the burrow near to the surface
of the tree and the adult works its way out from the cocoon
after the pupa is split open. Occasionally the adults will
be found with the ovipositor fast in the bark of the tree
or in the wood. They burrow in to deposit eggs and seem
ORDER HYMENOPTERA 295
unable to withdraw the ovipositor. Presumably they
deposit a single egg in each perforation. There are two
common parasitic species, Thalessa atrata and lunator,
which are the natural check upon the multiplication of this
form and which ordinarily keep its numbers down to narrow
limits. Without this check the species would probably mul-
tiply to a great extent. The parasites are representatives
of another family, [chneumonide. They are rather slender-
bodied and with extremely long ovipositors. In Thalessa
atratathey are four or five inc hes! long. These are driven into
the burrows of the tremex and the eggs are deposited in the
burrow and presumably at some point close to the tremex
larva. The larva of the Thalessa is said to attack the tremex
larva externally and not to be internally parasitic-—a little
variation from the general habit of parasitism for the family.
Cynipide.—The Cynipid@ are in one sense a vegetable-
feeding group, though some are hosts or guests of gall- makers.
The primary feature is that they make galls and the larvee
develop within these galls. Galls are not a normal plant
product, nor a product of the insect alone, but a combina-
tion product of the insect and the plant. A stimulus given
to the plant cells results in a definite specific form of growth
which is just as specific as the form of the leaf or the fruit
of the plant on which it is formed. Species can be deter-
mined accurately from the form and structure of the gall.
The most familiar of these galls are the oak apples. mineee
are rich in tannic acid which gives the gall a decided flavor.
A globular structure is built out by a great growth of plant
cells. The gall grows and dey elops more rapidly than the
larva. The larva gets its growth by eating the cells which
are close to it and all the rest of the structure is apparently
developed purely as a protective device for the larva.
The greatest number of species occur on oaks, some on
roses, ete. There are dozens of different kinds on oaks and
many different species on a single species of oak and some
restricted to one certain species of oak alone.
Parasitica includes several families: Ichneumonidae, a large
group; Braconida; Chalcidide,a large group;and Proctotrupide.
296 BEES AND WASPS
All of these are distinctly parasitic in habit. Braconide
and Ichneumonide are the more generalized kinds of para-
sites and parasitize such forms as the caterpillars of the
Lepidoptera in immense numbers. They constitute a very
important check upon a number of very important species.
It is hard to do much in the way of encouragement of them,
though they may be transported from one country to
another. One subfamily is pretty commonly parasitic on
plant lice.
Chalcidide form a specialized group with much reduced
venation for the wings and the Proctotrupide are minute
and largely egg parasites.
Family Ichneumonide.—The Ichneumon flies include
many of the larger species of parasitic Hymenoptera and a
number of species which have important economic bearing
on the abundance of destructive species. Good examples are
to be noted in the species of Thalessa which parasitizes the
pigeon tremex and in species of Ophion which attack a num-
ber of different kinds of caterpillars. The species of Pimpla
are also conspicuous members of the group and their attacks
are made especially upon injurious species of moths, so that
they are to be counted distinctly serviceable.
Pimpla conquisitor is one of the parasites of the tent cater-
pillar and it is possibly due to this species that the tent
caterpillar is less destructive than it otherwise might be. In
this species the parasite lays its eggs in the cocoon of the
host and its larva develops within the pupa, so that it
serves to prevent the development of the adult and the
deposition of the eggs which would follow.
Family Braconide.—The family Braconide@ is quite similar
to the preceding but the species are on the average smaller
and many of the species parasitize the minuter kinds of
insects such as plant lice. A quite common species 1s A pan-
teles glomeratus which is a parasite of the common cabbage
worm and which no doubt serves as a quite important factor
in assisting to keep this pest in check.
Perhaps one of the most important species is the little
Lysiphlebus tritict which is a very abundant parasite of
ORDER HYMENOPTERA 297
Fic. 236.—Pimpla conquisitor, an important parasite of the tent cater-
pillar: a, larva, enlarged; b, head of same, still more enlarged; c, pupa; d,
adult female, enlarged; e, f, end of abdomen of adult male, still more
enlarged. (From Fourth Report, U. S. Ent. Con.)
Fia. 237.—A panteles glomeratus: a, adult fly; 6, cocoon; c, flies escuping
from cocoons; a, b, highly magnified; c, natural size. (After Chittenden,
Div. Ent., U.S. Dept. Ag.)
298 BEES AND WASPS
aphids. It is a minute species and its larva maintains its
entire growth within the body of an aphid, the entire con-
SU
Fig. 238.—Parasitized cabbage worm (Pontia rape@), showing cocoon
mass of Apanteles glomeratus below. (From Chittenden, Div. Ent., U. S.
Dept. Ag.)
Fia. 239.—Lysiphlebus tritici, principal parasite of the spring grain aphis:
adult female and antenna of male, greatly enlarged. (Webster, Div. Ent.,
U.S. Dept. Ag.)
ORDER HYMENOPTERA 299
tents of which are not equal to a drop of water. However,
the parasite may feed upon the aphid during some little
time and is supplied with food from the efforts of the aphid
Fie. 240.—Wingless female of ‘‘green bug’’ containing larva of the
parasite Liysiphlebus tritici. Much enlarged. (Webster, Div. Ent., U. S.
Dept. Ag.)
sucking nutriment from the plant. This species is consid-
ered one of the principal agents in control of the spring grain
aphis or the “green bug’ which during recent years has
Fig. 241.—Lysiphlebus depositing its eggs in the body of a grain aphis.
Much enlarged. (Webster, Div. Ent., U.S. Dept. Ag.)
caused extensive injury to the wheat crop in the south-
western part of the country. Its attack seems to be dis-
tributed, however, over a number of species and it is therefore
300 BEES AND WASPS
able to maintain itself even in the absence of any one species
of plant louse.
Fic. 242.—Pteromalus puparum: female at left; male at right—highly
magnified. (Chittenden, Div. Ent., U. 8. Dept. Ag.)
Fig. 243.—Chalcis ovata, a parasite of the alfalfa caterpillar: a, pupa;
b, parasitized pupa of tussock moth (Hemerocampa leucostigma): c, adult;
d, same in profile; e, pupal exuvium. Enlarged. (From Howard.)
Family Chalcididee.—The family Chalcidide, one of the
groups which includes extremely minute insect forms which
parasitize insects, such as the plant lice, scale insects, and
ORDER HYMENOPTERA 501
many other forms. They have broad heads, rather thick
jaws and are quite generally of brilliant metallic colors. A
distinctive character is found in the reduction in the veins
in the wings so that only the costal vein borders the front
margin of the wing and is so developed as to be rigid. In
larger insects a great number of these parasites may develop
in a single individual. In the smaller species usually a
single parasite is found in the host. They are especially
Fic. 244.—Tsosoma tritici: adult of the joint worm—much enlarged.
Howard, Div. Ent., U. 8S. Dept. Ag.)
effective in the destruction of scale insects, and some of the
species are parasitic in the eggs of other insects. In some
cases they become secondary or tertiary parasites in which
case their value is changed.
Pteromalus puparum, one of the parasites of the cabbage
worm, 1s apparently distributed well over the area occupied
by this species and its attacks upon the host form serve as
one of the quite constant checks upon the abundance of that
species. The parasitized pupe usually show a different
302 BEES AND WASPS
color, and if observed these may be allowed to remain in
the fields with the expectation of the parasite serving a
good purpose for a later generation. If possible it is well
to assist them somewhat by putting the pup under screens
which will permit the escape of the parasites, without
allowing the escape of butterflies which might issue from
healthy pup.
While most of these species are parasitic, there are a few
which are plant feeders, and notable among these is the
Fic. 245.—Bits of hardened straw remaining with the grain after
thrashing. (After Webster, Div. Ent., U.S. Dept. Ag.)
wheat joint worm (Isosoma tritict), which is the cause of a
great deal of damage to wheat in many parts of the country.
The presence of the joint worm is evidenced by the forma-
tion of woody places in the stem, within which the worm
is found and the effect of its injury is to cause the stems to
become weakened so that frequently the grain will be broken
down, especially if there are severe winds. The insects pupate
within the stems and remain in the pupal stage all winter.
This accounts for their frequently being found in chaff or
ORDER HYMENOPTERA 308
straw. Sometimes the hard pieces of straw are carried over
in the threshing and mixed with the grain. It is evident
Fia. 246.—Isosoma tritici: female ovipositing. (Photo by Ohio Exp. Sta.)
that burning of the stubble in the fall or early spring will
destroy the pupa in the fields and it is considered that the
use of straw and chaff in the bedding of stock or as fodder
304 BEES AND WASPS
is an excellent plan to reduce the infestation. Of course
burning chaff or straw would accomplish the purpose, but
Fig. 247.—Isosoma tritici: adult male. (Photo by Ohio Exp. Sta.)
Fria. 248.—Isosoma tritici: larvee. (Photo by Ohio Exp. Sta.)
ea % a
this is not deemed necessary if the straw passes through the
barnyard, as most of the pupe are killed by this treatment.
ORDER HYMENOPTERA 305
The egg parasites (Proctotrupida) are extremely small, most
of the species being parasitic in the eggs of insects. Eggs of
web worms are parasitized and the whole development of
the Proctotrupid is contained within the egg, One species
is described as one-nintieth of an inch in length, another one
one-hundred-and-fiftieth of an inch and the body very slender.
These serve a most important function in the destruction of
other insects, those that would otherwise hatch from the
eggs. When the parasites feed on the caterpillars the damage
is only partly checked, but when the parasite feeds on the
eggs the damage is all prevented. One of the important lines
of economic entomology is to study such forms and -their
life histories with regard to other species, as primary para-
sites, secondary parasites, tertiary parasites, etc., since
their value depends on whether they directly control a pest
or whether as a secondary parasite they reduce the numbers
of a primary parasite which is useful.
Ants (Formicina) are one of the most interesting groups
of insects. They are sometimes given the rank of a superior
family, but the principal family is that called Formicidae.
The name is associated with the secretion of formic acid.
The name of the group probably gave the name to the
chemical. The secretion is one of the characteristics of the
Hymenoptera. Ants present striking habits of family life;
the formation of different classes among the individuals
of a colony. This separation into classes is paralleled in
other groups, as the bee family and among wasps, and
expecially the termites. The result. of community life is
that it presents certain relations in the community in the
way of division of labor. The primary forms are males
and females, and then a class which are not sexual but are
derived from a modification or suppression of the reproduc-
tive factor in one of the sexes. Occurring with this is the
reduction or complete absence of wings. These constitute
the so-called workers or soldiers of a colony. They have no
wings whatever. This feature reaches far back into the
ancestry of the group, or else shows parallel evolution.
Sexual individuals have wings primarily but in the case of -
20
306 BEES AND WASPS
the queens the wings are broken off or dropped off after the
flight associated with mating. ‘Then the females are unable
to travel and remain fixed in a certain colony and furnish
offspring for the colony. A group of ants is called a formi-
cary. It may vary in number of individuals from a few
hundreds to thousands. A single queen ant may survive
for a great number of years and the same colony may go on
for many years. The usual course of the life-cycle is for
winged females to issue from some colony and make their
flight that is connected with mating, and then to burrow
into the ground or select a suitable nest to place the eggs
and begin the formation of a new colony. The fertilized
queen is capable of producing workers and in some cases the
queen alone will start a colony. In some forms perhaps the
help of other ants is needed. With the starting of the
colony and the deposition of eggs a colony becomes more
populous. Differentiation has not gone quite so far in ant
colonies as in some others. The workers take care of the
eggs and the young and shift the young about, and if the
nest is disturbed they carry the pupe to a place of safety.
The pupe are, of course, helpless. The workers and soldiers
_die off pretty rapidly. They survive through the working
period and when they die are replaced by other workers.
The colony retains its individuality year after year. The
life of the colony is probably at least as long as the life of
the queen and probably continues longer than that. Other-
wise the colony would have to terminate soon after the
death of the queen. The multiplication of colonies is pro-
vided for by the issuing of new queens from the colonies
and the ability of the ant to survive depends as much on
its ability to form new colonies as on new individuals.
There is just as much reproduction of colonies as of indi-
viduals. The cycle is probably for annual periods in each
season and the females are probably produced annually.
The food of the ants is primarily plant food. They collect
nectar and various substances of vegetable origin, and the
workers are responsible for the collecting and storing and
using of the food supply. Indirectly they get such supplies
ORDER HYMENOPTERA 307
from the aphids. They store up grain in some instances,
and use this grain to some extent at least as a food
supply.
One of the species—the honey ants-—collect honey and
store it in the stomachs of certain individuals of the colony.
The bodies of these individuals become very much distended
and the abdomen becomes large and spherical and these
keep the food for a part of the year. This ant occurs in the
plateau regions of Colorado, particularly in the Garden of
the Gods. The volume by McCook on these ants is an
especially interesting account of animal adaptation. Also
Lubbock’s book on Ants, Bees and Wasps gives many
interesting experiments, but his observations indicated that
while there is an adaptation to complex conditions they are
not comparable to the activities of human beings.
There are many species—little red ants, those occurring
in gardens, and walks, the house ants, and the large car-
penter ants, which form nests in hollow logs. The queen is
quite a large insect and usually with wings entirely wanting.
Large red ants and large black ants construct hills for their
nests, sometimes three to six or eight inches high, and
perhaps twelve to eighteen inches across the top. This red
ant is a slave-making species, going out on forays and
capturing black ants which they force to carry on the labor
of the colony. Some species are said to have carried the
slave-making habit to such an extreme that they are unable
to get along without the slaves and even require slaves to
go out and capture new slaves.
Field Ants.—One of the important species is the little
field ant which is associated with the corn-root louse and
which has been named in connection with the discussion of
the aphid. This species is very widely distributed through-
out the United States and wherever corn is grown and the
corn-root louse is present it constitutes an important factor
in the abundance and destructiveness of the root louse.
The Argentine ant (Jridomyrmex humilis Mayr) is one of
the recently introduced pests and one which is liable to
become distributed to cover the Southern States and possibly
308 BEES AND WASPS
to occupy at least the cotton-growing region if not a greater
extent of the country.
The species is thought to have been introduced from
Argentina and was first noticed in New Orleans where it
was reported as occurring in fair numbers in 1891. It is
now known throughout most of Louisiana and in eastern
Texas, and also occurs in California. Within the range of
its distribution it has become a very. serious pest and its
further distribution will naturally be a matter of serious
consequence to other localities. Without assistance the
ant migrates slowly but with the opportunities afforded
by commerce its dispersal may be quite rapid.
As with the other ants there are males, females, and
neuters; the males and females being winged, the neuters
wingless but the females lose their wings after the mating
flight.
The size of the colonies varies from a few individuals to
many thousands and a number of queens may be present
in each colony. The nests are built in various places under-
ground, seldom occurring at any great depth.
This species is a most difficult one to control and experi-
ments with poisonous materials, repellants, etc., have met
with only partial success.
Wasps (Sphecina).—In this group we have a considerable
number of solitary forms of those which preserve the primi-
tive conditions of males and females without workers or
with large broods raised at one time in one nest. Mud,
paper, pith, ete., are used as building materials. The sand
wasp (Bembecine) burrows into the sand for its nest. They
stock these nests with insects of different kinds such as May
flies. The larvee develop by feeding upon the bodies of these
stored insects. It is strange that they can keep a burrow
complete enough so that they can pass in and out a number
of times. They are very common here and are protected
to some extent by the coloration of the body. Their bur-
rows are constructed along through the summer and the
larve develop during the summer and presumably all reach
the pupa stage before winter and live over as pupe, issuing
ORDER HYMENOPTERA 309
the following season. The adults will be found flying around
all through the midsummer months. Perhaps they are a
Vic. 249.—The Argentine ant, adult forms: a, adult male; al, head of
male; a2, petiole of male; 6, worker; bi, head of worker; 62, petiole of
worker; c, fertile queen; cl, head of queen; c2, petiole of queen. All
greatly enlarged. (After Newell.)
310 BEES AND WASPS
little more abundant in the later part of July. They belong
to the Bembecide. One of the large members of the family
is called the “cicada killer’ Sphecius speciosus.
Social wasps (Vespide) make large nests and large colon-
ies and show some degree of differentiation into classes or
‘astes of individuals in that there may be smaller indi-
viduals at the end of the season which live through the
winter.
The Hornet (Vespa maculata) builds up a large paper nest
which is made up of a series of combs with the aperture at
the lower part. This becomes very populous during the
latter part of summer. The survivors are adults that secrete
themselves under leaves and rubbish and start a fresh
colony the succeeding year. They do not live in the large
nest through the winter. This common species is social.
The yellow jacket (Vespa germanica) is also a_ social
species, its nests are found in hollow trees.
It is interesting to compare the materials used by these
species. They use wood or paper which is a pulp worked up
from the wood fiber and is to be compared with manufactured
paper in the tissue of which it is made and in the manner of
manipulation. |
In the bees, Apidea, there is an elongation of the beak for
getting the nectar from the flowers and the more specialized
forms secrete wax for the formation of the cells. This is
worked up into a gum or built into cells for the rearing of
the larvee. There is a gradual culmination in the develop-
ment of community life in this family from the wild bees that
are practically solitary up to the bumble bee and honey bee.
The honey bee is probably the best-known because kept
under domestication. A bee colony consists of a queen, which
is a constant factor in the colony—a queenless colony can-
not survive any length of time—and drones or males which
occur during the summer. These are the normal-sexed indi-
viduals. Then we have the workers or neuter forms which
are undeveloped females and these carry on all of the com-
plex work of the colony, providing food, caring for the larvee
and for the rearing of new queens.
ORDER HYMENOPTERA oll
The cycle as applied to the queen would involve three to
five years. They live that long and deposit millions of eggs
during that time. The drones live but a short period. The
workers live a few weeks or months through the summer
and in the more inactive parts of the year. The queens from
the egg stage to the adult stage occupy about sixteen days,
the workers twenty-one days, the drones twenty-four days.
There is a distinct difference in the eggs that produce workers
and drones. The worker eggs are fertilized and the drone
eggs are unfertilized. This is apparently controlled by
the queen and dependent upon the kind of cells in which
the eggs are laid. The exact method of control by the
queen is not fully understood. The size of the cells may have
some effect by the pressure on the abdomen. ‘The accelera-
tion of the queen may be because the workers feed them with
a richer sort of food. They develop more rapidly and the
reproductive organs are fully developed. There is colony
reproduction as well as individual reproduction, that is, an
increase in the number of colonies. They die off from old
age, loss of queen, cold weather, etc., and if there were no
process for increasing the number of the colonies they
would be exterminated. This is provided for by swarming.
The queen and a large number of workers issue from the
colony and form a new colony. The old colony is provided
for by other young queens in the cells or else fertilized.
There is a loss of honey but no break in the life of the colony.
Bee-keeping is an important industry and there are many
books dealing with the subject. Among those of special
value are the following:
Cheshire, Honey Bee. Root, Bee-keeping. Langstroth, Hive and Honey
Bee. Snodgrass, Anatomy of the Bee. Benton, The Honey Bee. Cook,
Manual of Bee-keeping. Comstock, How to Keep Bees. Phillips, Bee-
keeping. Pellett, Productive Bee-keeping.
CHAPTER Xl
PRINCIPLES OF ECONOMIC ENTOMOLOGY.
WHILE it cannot be assumed that we have at present a
complete knowledge of those underlying principles which
are to be recognized in the prevention or control of insect
ravages, enough has been done to make an attempt at a
brief statement of such principles in order. Many of these
principles have been stated in greater or less detail in the
writings of different entomologists but no comprehensive
statement has been attempted—especially since the marked
advances of the past quarter-century. Applied entomology
today is a totally different structure than that which
existed twenty or even ten years ago. In many respects it
is getting nearer to the fundamental laws of biology, and
there is a more general appreciation that its successful appli-
cation involves thorough acquaintance with biological prin-
ciples. In the broadest sense economic entomology involves
a recognition of the relation existing between insects and
other organisms, but finally, the relation they bear to the
human species.
RELATION OF INSECTS TO OTHER ORGANISMS.
Considering the great multiplicity of msect forms, their
world-wide distribution in almost every condition open to
the support of life, it is not strange they occupy a most
important relation to other organisms. This relation may be
serviceable or inimical, directly or indirectly from the
stand-point of any particular organism, and may indeed
differ totally at different times or under different conditions.
From the stand-point of any particular species it is detri-
(312)
ECONOMIC ENTOMOLOGY 313
mental if the insect feeds upon the plant or animal or inter-
feres with its successful existence. It is beneficial, if it
contributes to its success by warding off other dangers or
assisting pollination or contributing in any way to its better
growth and development.
ECONOMIC ENTOMOLOGY.
Economic entomology is based upon the relation of
insects to mankind and all species that interfere with his
welfare are considered injurious, and those that may serve
him in any way are considered beneficial. The relation,
however, may become very complex. An insect that feeds
upon a cultivated crop, or destroys the products of a crop,
or injures a domestic animal, or worries man himself, or
menaces his health by inoculating him with disease, is
injurious from the human stand-point. While if it produces
a valuable material such as silk or honey, wax, dyes, etc.,
or serves to destroy injurious species as predaceous and
parasitic forms, or feeds upon noxious plants, weeds, or dis-
poses of noxious substances, as the scavengers, it is directly
useful, and we term it beneficial. Many cases are very clearly
in one class or the other; many have little apparent impor-
tance one way or the other, and in many cases the relation
may change with circumstances. For example, a parasitic
insect preying on an injurious species is useful to us, but if
it destroys a useful insect it becomes injurious. A parasite
on a parasite, that is, a secondary parasite is detrimental if
the primary parasite attacks an injurious insect, and a
parasite upon this secondary parasite, that is, a tertiary
parasite would be useful, since its effect would be to check
the secondary and favor the primary parasite. Still further,
a quaternary parasite, and this is I believe as far as this
relation is known, would be injurious. The reverse in each
case would be true if the original host were useful.
We should not forget that these three terms refer strictly
to mankind, for in the broader biological sense each kind of
314 PRINCIPLES OF ECONOMIC ENTOMOLOGY
animal is doing its best to perpetuate itself and multiply
its kind, and every interference is from its stand-point
injurious.
FOOD HABITS.
It is very evident that one of the first and most important
relations concerning an insect is to be found in its food
habits.
Insects, like other animals, may be considered primarily
herbivorous. ‘That is, the most general plan of nutrition
for them would be to feed upon fresh, growing leaves of
plants, with feeding upon fruits, seeds, bark, wood, roots,
decaying wood as adaptations, while the assumption of car-
nivorous habits either as predaceous or parasitic species, or
to go further, sucking blood of higher animals may be
considered adaptations in another direction.
It is on this broad, general basis that we may consider
herbivorous insects in the main injurious, and carnivorous
insects, especially if predaceous and parasitic on other insects,
as beneficial.
In this connection we may refer to the principle which
has been termed “unity of habit” and treated by Dr. B. D.
Walsh. This is in effect that in any given group we may
expect to find similar habits among all the species, and if for
any species the habits are unknown, they may be expected
to follow those of the known species. To this law there may
be striking exception, however, and along certain lines
peculiarities should be considered the rule and not the
exception. To find the most certain action of the law we
may, I think, say that in all particularly specialized groups
“unity of habit” is practically general. In less specialized
groups variation is more frequent. For example, in the bark
beetles, Scolytide, we would be astonished to find a leaf-
eating larva, or in Aradide@ a species that does not live under
bark is exceptional. In Lepidoptera, the larval diet is gener-
ally herbivorous and the two or three carnivorous species
notably the exception. We safely assume that all plant
lice are plant feeders and treat them accordingly. The
MEASURES FOR INSECT CONTROL 315
weevils are reckoned invariably as plant feeders, almost
entirely confined to fruit or seeds, while Carabidae, though
largely carnivorous, show too much variation in food and
too many herbivorous species to make it safe to draw con-
clusions without the study of each species. In the applica-
tion of this principle, therefore, it becomes necessary to
consider the nature of the group as a whole, not merely
the habits of certain ones.
MEASURES FOR INSECT CONTROL.
There have been a great many different remedies and
plans of treatment for the control of injurious insects and it
would be impossible to discuss them all, even those which
have general application, in a short course. The attempt
will be to select some of the most universal and useful and
give them with such rules as to make it possible to apply
them without further instruction.
In general the methods of control for insects may be
separated into those which are direct and have in view the
destruction of the insect with some destructive agent or
mechanical application, and those methods that depend upon
some plan of cultivation or sequence of crops to prevent or
modify the insect attack.
Direct Methods. Insecticides.—Substances used in such
manner as to kill directly are termed insecticides, and insec-
ticides may be classed broadly into two large groups: (1)
those which are poisonous in character and depend for their
effect upon the insects swallowing them with their food and
(2) those which affect the insects by contact or penetration,
such as the oils and fumigants.
Of the poisonous materials some preparations that are
among the most important may be mentioned.
Paris Green.—Paris green is a bright green arsenical
powder which should contain at least 50 per cent. arsenious
oxide and not over 3.5 per cent. soluble arsenic. The for-
mule for its use are as follows:
IPAnISVoTCCNnh ae tee si Spec om Be 5 ounces
umprlimers ssike es 8 ee, as 1 pound
IWisitelmeemrnn. So ete eyes 2 os 200 rallons
316 PRINCIPLES OF ECONOMIC ENTOMOLOGY
For small quantities use:
Paristoreenyas 30) co a) ee ee ne ae 1 heaping teaspoonful
Dumplime ~) 2 = = 92 94. 4 2.0r 73 ounces
Wiater= ci) Seo.) mr cmes, ahem hoy orm mets 3 gallons
For dry application the powdered Paris green may be
mixed with flour or air-slaked lime and dusted upon the
plants by enclosing the powder in a muslin sack and shaking
this over the plants it is desired to treat.
London purple is a by-product in the manufacture of
aniline dye and is an effective poison but somewhat less
certain in its effect and more likely to injure foliage. It is
at present not so common on the market as Paris green, it
is, however, somewhat cheaper and when properly diluted
is a desirable insecticide.
Arsenate of Lead.— Arsenate of lead, available in two forms
—paste or asa white powder—may be secured on the market,
or the arsenate may be formed by chemical combination of
arsenic and lead. Formule for the use of this substance
are as follows:
Arsenateot lead (paste) an) lennon cnet 3 to 10 pounds
Wistert) oe. fel One ee a net oOroallons
or
Arsenate of lead (powder) . . . . . 1 to 4 pounds
Waters (050) 2s gn nn ee ees OOoallons
For small quantities use:
Arsenate of lead (paste) . . . . . . . +. ~ 1 teaspoonful
Nighi ee Poke ee ey ee oe ke ee ealiloin
If used as a spray this can be applied to a great variety of
plants for the destruction of leaf-eating insects, and since
it can be used at high strength without injury to foliage it
may be used for the most resistant kind of insects. Its killing
power is not equal to that of Paris green and consequently
somewhat stronger solutions must be used.
Like Paris green, it may be used in the dry form as dust
or with a powder gun.
Hellebore.—Hellebore is a white powder destructive to
insects but not poisonous to domestic animals or man, unless
MEASURES FOR INSECT CONTROL 317
in large doses. It may be used as a spray or in a dry form
and is applicable to currant bushes or other kinds of fruit,
for saw-fly larvee and other leaf-feeding insects where it is
undesirable to use arsenic.
Arsenical Bran Mash.—This is used as a bait for cut worms
and other insects which endanger vegetation and which it is
desirable to kill before the vegetation has been attacked.
Formula as follows:
Bran NE ae ie) ba edit ie es OR pOUNGS
Tennis Caren ogeecey a Nes Be La. Bec es eee + pound
Cheap molasses. ae ee ee eer lo Quant
Water, as needed to moisten:
For small quantities use:
Bran ee aN a? 1-5, oe ee Bla) Sel Quart
iParistoreenue a) mis) ee ae ae) eee se teaspoonful
Cheap molasses. eee eee lntablespoontul
Water, as needed to mciacen®
For grasshoppers the attractiveness of this bait is very
much increased by the addition of lime juice or orange or
lemon flavor.
Contact Insecticides.—Insecticides of this group depend
upon immediate contact with the insects to be affected,
different kinds of sprays, direct applications and the use of
fumigants which are distributed to the insects to be reached.
Lime-sulphur wash is the most important of the insecti-
cides now in use against the scale insects, especially the
San José scale. The commercial lime-sulphur preparations
on the market generally may be secured at seed-stores
or from dealers in nursery or orchard supplies and depended
upon as containing the correct proportions and if used
according to directions should give very certain results.
These can be secured at reasonable prices and are often
preferable to the solutions of home preparation. How-
ever, directions for the preparation of the compound may be
of service and two formule will be given, one for the concen-
trated solution to be diluted when used and the other for
immediate use.
318 PRINCIPLES OF ECONOMIC ENTOMOLOGY
Fic. 250.—Making lime-sulphur solution (Photo. Ohio Exp. Sta.)
Fia. 251.—Plant for making lime-sulphur solution in large quantities.
(Photo. Ohio Exp. Sta.)
Concentrated Lime-sulphur.
Lump lime ee ce hs oe Se ee ae eee = ro Ohpounds
Sulphur Sy etop tre os ye a ee eee a) eres eo LOOMMOUnGS
MEMEO Ns oe mo o's 6 o o uo « -6 (AO rallionae
Dilute as directed.
MEASURES FOR INSECT CONTROL 319,
For exact preparation the use of the hydrometer is desir-
able and the following scale of proportions is recommended.
Reading on hydrometer Number of gallons of water to 1 gallon
in degrees (Baumé). of the concentrated lime-sulphur.
35 9
34 82
333 81
32 Pa)
31 73
30 ifr
29 64
28 63
27 6
26 iy
25 5t
24 5
23 4}
22, 41
21 33
20 33
19 35
18 3
17 23
16 25
15 Qt
14 2
Regular Lime-sulphur Wash (for winter spray).
Lump lime ON een Memme a Se ek oe) os. Ge Vs Se OOUNGS
Stille 5 6 5 so 6 6 8 oe 6 Gp 6 6 = lPioxoriborel
\Wistclie wee we ewe ee ey hss ew 50 gallons
Kerosene.—The use of kerosene or petroleum combinations
has given some of the most useful combinations and they
still have a wide range of usefulness, although at present
less used than the lime-sulphur solutions for scale insects.
Generally they may be applied to practically all kinds of
insects which are suctorial in habit and cannot be reached
by arsenical sprays, but they are especially efficient against
the scale insects at time of migration and against such soft-
bodied insects as the plant lice. In the preparation of the
kerosene emulsion it is extremely important that a thorough
emulsion be obtained so there will be no separation of oil
from the water, as there is much damage to the foliage if
this oceurs,
320 PRINCIPLES OF ECONOMIC ENTOMOLOGY
The standard formula for kerosene emulsion is as follows:
Hard soap . 4 pound
Hot water (soft) . 1 gallon
Kerosene (coal oil) 2 gallons
To form the emulsion take a gallon of soft water and
dissolve in it a half-pound of soap, then remove from fire,
add two gallons of kerosene, which should be thoroughly
mixed and agitated at once. One of the best methods is to
run the solution through a spray pump, driving it back into
the bucket from which the solution is drawn, and about
five or six minutes of this mixing will produce a perfect emul-
sion. It should be carried to such completion that there
will be no tendency for the oil to separate. Small quantities
may be made rapidly in the proper proportions by the use of
an egg-beater or by a process which produces a violent
agitation which may be maintained for some length of time.
This strong emulsion should be kept in a cool place and
covered or in a tight receptacle and may be diluted as wanted
with soft water, the amount of dilution depending upon the
insects to be reached. For scale insects, one pint of strong
emulsion to nine parts water. Soft plant lice are readily
killed by a solution of one part of stock solution to fifteen
parts of water.
Tobacco Extract.—This is a very efficient contact insecti-
cide and may be used against many kinds of insects but
especially such forms as plant lice, thrips, and the better-
protected sucking insects. Various solutions are on the
market but the one termed Black Leaf 40, containing 40
per cent. nicotine sulphate, is one which seems to have
proved one of the best; this is used in dilutions of 1 part
to 300 of water to 1 part to 600 parts of water—for use in
winter time, when plants are dormant, and for summer use,
dilutions—1 to 500, to 1 to 1000 are recommended for tender
insects such as plant lice. Similar solutions may be used for
parasitic lice and mites on domestic animals.
Tobacco dust may be used or an extract prepared from
this by steeping or soaking in water overnight. In making
the preparation boil one pound of dust or stems to a gallon
MEASURES FOR INSECT CONTROL 21
of water, and this may be diluted, one to two parts of water
and applied for leaf-sucking insects.
Pyrethrum or Persian Insect Powder.—'I'his is a very power-
ful insecticide when properly prepared, but loses its strength
when exposed to air, so that particular care should be taken
to keep it in a tightly closed receptacle or it must be used
when quite fresh. It is a powdered material derived from the
grinding of the leaves or flowers and buds of the Pyrethrum
plant, the main supply coming from Dalmatia, but a consider-
Fig. 252.—An orchard demonstration in spraying.
(Photo. Ohio Exp. Sta.)
able amount being produced in California. It is a volatile
oil and it is the vaporization and contact of this which is
destructive to the insect. It may be used as a spray by the
dilution of one ounce of powder to two gallons of water, and
is available for saw-fly larvee and other pests upon currants,
gooseberries, etc., being especially valuable on account of
its not being poisonous to man or domestic animals. ‘The
powder, blown into rooms is effective for the killmg of
mosquitoes and flies, but for this purpose does not compete
21
O22 PRINCIPLES OF ECONOMIC ENTOMOLOGY
with some other measures. It may be used upon dogs and
cats for the killing of fleas by dusting in the hair.
Machinery.—lor the application of these various insecti-
cides, a great many forms of spraying outfits, dusting
machines, ete., have been devised. These are now so thor-
oughly standardized and handled by reputable firms that
anyone may secure such outfits as may be needed for his
individual purpose.
Cultural Methods.—Another distinct group of measures
for insect control (the indirect methods) may include those
which have to do with methods of culture and alternation of
crops and various cultural methods which incidentally have
an effect upon the activities of insects.
First among these may be mentioned the general practice
of crop rotation which for a good many insects serves in an
admirable way to prevent undue multiplication of injurious
forms. Aside from its advantages in other ways, rotation
serves to dislodge or starve out a great number of insects
which are not able to migrate readily and which become
established in any field only after several years of uninter-
rupted development. For such forms the plowing up of the
fields or a change from one crop to another may prove an
almost perfect control. A striking example of this has been
noted in the case of the corn-root worm. In somewhat les-
ser degree the process is available for many of the pasture
and meadow insects which are dependent upon grasses as
their main food supply and which when grass is plowed
under, especially if this is done at a time when the insects
are in larval or in a known migratory stage, serves to destroy
them very effectively.
In a general way plowing will cut off the food supply, some-
times will bury the insects to such a depth that they do not
extricate themselves. In this connection, however, it is some-
times very important that the condition of the insects be
known, as there are cases, such as white grubs, sod worms,
and wire worms, which if plowed under with the sod will,
if a second crop is planted soon, transfer their attack to the
new crop with very disastrous consequences. It frequently
MEASURES FOR INSECT CONTROL O20
happens that corn planted on sod land is in this way very
seriously injured. ‘The precaution should be to plow under
long enough before the new crop is planted to allow oppor-
tunity for the starving out of insects which may be present
in the grass.
Another practise in this line is for such an arrangement of
crops that insects which naturally migrate from one crop to
another will be separated by a crop of different character,
something that will not serve them as a food supply. For
instance, the migration of the chinch bug from wheat fields
into corn fields may be prevented by the introduction of a
strip planted to potatoes, beans or some crop which is not
available as chinch bug food.
The use of an early planted crop for the purpose of attract-
ing insect egg deposition with the view of destroying the
insects so attracted and thus protecting the later crop, has
been in vogue for many years and is applicable to such
species as have several generations in a season. A good
example of this is the corn-ear worm which if attracted to
a small area of early planted corn which is fed to hogs at the
time the worms begin work will assist much in the preven-
tion of attacks on adjacent fields.
In some cases where an insect is especially destructive in
a certain area, resort may be had to the suppression of the
cultivation of a crop for one or two seasons, thus eliminating
food. This will largely diminish if not practically extermi-
nate such insects as are strictly dependent upon this crop for
existence. Naturally sucha method is limited in application,
as the complete suppression of any crop in a certain district
is a difficult matter to accomplish.
Clean culture is often recommended as an important
aid in the suppression of insects, and there is no doubt that
for many species attention to the elimination of food plants
which assist them to survive and the cleaning up of litter
in which they may hibernate will accomplish a great deal
in the reduction of numbers and the consequent extent of
injury. Clean culture, however, must be taken in connec-
tion with a study of the habits of the species which it is
324 PRINCIPLES OF ECONOMIC ENTOMOLOGY
desired to control and cannot be considered as an efficient
practise for many insects that are troublesome on the
average farm. In this connection it may be stated that it
is good entomological practise to use wire fences in place
of the old rail or board fences, and it is a good plan to culti-
vate as close as possible to fence lines with the consequent
reduction of the growth of weeds, bushes, and so on.
Another matter which deserves attention is a close guard-
ing against the introduction of pests in seed or along with
introduced plants, as many of the serious pests are readily
transferred from place to place in such materials as straw
and various kinds of seed packages and thus gain a foot-
hold in a locality in which they have not been troublesome
before.
NATURAL ENEMIES.
Insects are preyed upon by many natural enemies—birds,
reptiles, toads, spiders, and these serve as checks to their
inordinate increase. Bird protection has been strongly
urged as an aid in insect control and certainly all or nearly
all of our common field birds are best allowed all the pro-
tection possible. Especially the small insectivorous birds
such as wrens, swallows, chickadees, titmice, ete., should be
given all the protection possible. Spiders are also generally
useful rather than injurious and should be undisturbed.
PREDACEOUS AND PARASITIC INSECTS.
The position of the predaceous and parasitic insects Is one
of considerable complexity, since their attacks may be
directed against both injurious and beneficial forms, and
their relation to human interests depends, of course, upon
the nature of the insects which they attack. In a general
way the carnivorous species feed upon the herbivorous ones,
and the herbivorous ones being ordinarily the most destruc-
tive to valuable crops, the average result may be looked
upon as advantageous. The study of these natural enemies
of the injurious insects has formed a considerable part of
PREDACEOUS AND PARASITIC INSECTS 320
economic entomology, and the importance of the subject
has been pretty generally recognized, though different
workers have assigned quite different value or importance to
to the subject.
Predaceous insects are those which attack and devour
other insects, possibly quite different kinds of insects, and
do it without sacrificing their own activity or independence.
Parasitic insects, using this term as it applies more particu-
larly to economic entomology, are those which are dependent
for a larger or smaller part of their existence upon some
particular kind of insect host. Nearly all are internal
parasites and in a great majority of cases the entire develop-
ment of the individual from the egg to pupa or adult stage
is passed within the body of a single individual host. Some-
times a large number of individuals will develop within a
single host, as in case of the minute ichneumons which
parasitize the larger caterpillars.
It must be noted here that a parasite itself may be para-
sitized by another species called a “secondary” parasite
which, by reducing the numbers of the parasitic species,
would become from the economic stand-point injurious.
This, again, in some instances may support still another
parasite, a so-called “tertiary” parasite, which by reducing
the numbers of the secondary parasite would be detrimental,
and a fourth, where such occurs, again assumes the opposite
role. It is evident where such a complex condition of para-
sites exists that it is practically impossible to adopt any
means of encouraging the beneficial or destroying the inju-
rious ones, and that this complex system of wheels within
wheels must be allowed to work out its own conclusion in the
balance of nature.
For most species there is perhaps but little that can be
done in the way of preserving the beneficial parasites or of
facilitating their work. We simply allow them to go on un-
molested, serving so far as they may, as a natural check upon
the injurious species. Many of our destructive insects are
insects that without this check would be seriously destruc-
tive, the regular attacks of these parasites serving very
326 PRINCIPLES OF ECONOMIC ENTOMOLOGY
effectively to keep the destructive species in reasonable
bounds and often preventing it from causing any serious
loss. The Hessian fly is certainly kept in check during a
considerable portion of the time by just such agencies, and
we can scarcely doubt that if the parasites of this species
were eliminated and other conditions unaffected, the losses
incurred would be enormously increased.
With some species it may be possible to assist the para-
sitic forms or to preserve them in such manner as to get the
advantage of their service. For instance, the cabbage
butterfly is very commonly parasitized by a small ichneu-
monid (Pteromalus) which issues from the pup, and it is
evident that if the pup were gathered and instead of being
crushed were enclosed in wire screen of such mesh as to
retain the issuing butterflies but allow the free escape of
the minute parasites, there would be a destruction of the
healthy butterflies without any reduction in the numbers of
the parasites. Again, in the case of the Hessian fly, care
as to the time when the stubble is burned or plowed under
in order to allow opportunity for escape and survival of
the parasites, might be of special service in their protection.
In California extensive shipments of lady bugs from the
northern part of the State to the Imperial valley to prey
upon the plant lice affecting melons is claimed to have
accomplished much in their control.
On the whole, however, the utilization of parasites in a
direct manner can hardly be depended upon as a very great
advantage, especially because of the difficulty in so training
the average cultivator that he will be able to distinguish
between parasites and non-parasitic forms, and adapt his
practice to accommodate them.
A more important phase of the subject perhaps is found
in the transportation of parasitic species from one country
to another where an injurious species has been introduced
without the introduction of its native enemy. It has already
been suggested that the original habitat of an injurious
insect is a matter of great importance, especially with
reference to its natural parasites, and a number of instances
EXCLUSION AND RESTRICTION BVA
are now in evidence showing the possibility of controlling
injurious, introduced species by means of the introduction of
the native enemies. ‘The most conspicuous is that of the
cottony cushion scale, introduced into California ‘several
years ago, and in more recent years the very extensive intro-
duction of predaceous and parasitic enemies of the Gipsy
and brown-tail moths in the New England States for the
control of these very destructive imported pests.
EXCLUSION AND RESTRICTION.
These are most important means of controlling insect
depredations. Formerly the entomologist devoted his
entire attention and effort to the study of native species
but now his attention is largely directed toward exclusion
from and restriction in the United States of new insects.
Until recently in the introduction of new plants from foreign
countries, no attention has been paid to the new insects
introduced with them. An important part of the work of
the entomologist in the future will be to study the insects
of other countries—not only those that are now destructive
there but those that do no particular damage, yet when
the natural checks are removed, are likely to become
destructive.
Special attention must be paid to those insects which are
native in those countries from which we import a greater
part of our plants. Some of the foundation principles in the
study are:
1. An insect, coming from another country, is more likely
to become destructive here if it comes from a somewhat
similar climate, and if the food plants are somewhat closely
related to those of its native country.
2. Insects coming from different climates may, if they have
a wide range of food plants, adapt themselves to the new
climate. It will then be proper to consider tropical species,
especially if their food plants are widely distributed and
have nearly related species in the country to which they are
brought.
328 PRINCIPLES OF ECONOMIC ENTOMOLOGY
3. Tropical insects that are limited to tropical plants for
food, will have little importance in temperate regions except
in greenhouses.
Most of the seale insects are tropical and in this climate
are on the borderline of their destructive region, but on
account of their general food habits they constitute a general
pest.
The question of the control of the distribution of the
destructive species is yet a new problem and one over which
there is considerable dispute; any measure intended to exclude
a foreign species must be adapted to a particular species, as
a general law will not suffice. Even the general exclusion of
the food plant will not alone be effective in keeping out the
pest, as it may have other means of dispersal.
Inspection and enforcement of restrictions at the port of
entry are being quite generally adopted. Inspection is most
effective when applied to plants. Sometimes it is necessary to
introduce a foreign species to prey on another foreign insect
that is already here, as was the case with cottony cushion
scale in California.
GLOSSARY OF THE TERMS USED IN
ENTOMOLOGY.
ABDOMEN. ‘The posterior region of the insect body.
ABIOGENESIS. Spontaneous generation.
ABRADED. Scraped or rubbed.
ACALYPTRATA. Those muscid flies in which alule are absent or
rudimentary.
AcuLEATE. Prickly; armed with a sting.
AcuUMINATE. ‘Tapering to a long point.
ApporsaL. Close to but not on the middle of the dorsum.
ApEpHAGoUsS. Belonging to the Adephaga; pentamerous, predatory,
terrestrial beetles with filiform antenne.
ADPRESSED. Contiguous or pressed to.
Aaamic. Reproducing without union with a male.
AGAMOGENESIS. Reproduction without fertilization by a male;
parthenogenesis.
AGGLUTINATE. Glued together in a mass.
AGGREGATED. Crowded together.
ALA (pl. Aua#). Wing or wings.
Auary. Relating to wings.
ALATE. Winged.
ALTERNATION OF GENERATIONS. Periodic production of partheno-
genetic females in a species that occurs in both sexes. These females
produce both sexes. Examples occur in Cynipidze and in some
Homoptera.
AuuLm.