Almost all insects in this category can fold their wings in repose back
over their bodies, as illustrated in fig. 31. A few kinds, notably some
of the moths and butterflies, have lost this wing action and in repose
hold their wings erect. In some of these kinds, the male is winged and
the female is wingless; in others, certain generations may be wingless
and others winged; and, in still others, the species may be wingless in
all stages. No members of the orders of folding-wing insects molt after
becoming winged or sexually mature.
[Illustration: Fig. 30.--Cursoria. _Supella supellectilium_, the
brown-banded cockroach. Actual length about 0.6 inch. (Drawing
courtesy of C. O. Mohr.)]
[Illustration: Fig. 31.--Cursoria. _Stagmomantis carolina_, a
praying mantis. Common in southern and central Illinois. Actual
length of adult about 1.5 to 2.0 inches.]
[Illustration: Fig. 32.--Cursoria. _Diapheromera femorata_, a
walkingstick insect. This insect lacks wings. Actual length about
3.0 inches. (Drawing courtesy of C. O. Mohr.)]
Cursoria
Cockroaches, Mantids, Walkingsticks
An order that includes three groups of terrestrial insects, each group
markedly different in appearance from the others: (1) rapidly running
insects usually having two pairs of wings, each with a dense network of
fine veins, the front pair of wings thick and leathery, fig. 30
(cockroaches); (2) winged insects having long, grasping front legs, fig.
31 (praying mantids); and long, wingless insects resembling sticks, fig.
32 (walkingsticks). The mouthparts are fitted for chewing. The young
look and act like the adults except that they do not have wings. The
cockroaches are omnivorous, feeding chiefly on organic foods rich in
carbohydrates, or on fungus growth. Cockroaches are among our most
persistent indoor pests, eating a wide variety of domestic foods. The
praying mantids feed on other insects, which they capture in their
enlarged front legs. The walkingsticks eat leaves. The cockroaches and
mantids lay eggs that are glued together and form pods or capsules, each
containing 30 or more eggs. The walkingsticks lay their eggs singly.
[Illustration: Fig. 33.--Isoptera. _Reticulitermes flavipes_, the
commonest kind of termite found in Illinois: _A_, first form queen
with wings spread, many times natural size (this is the form that
lays eggs); _B_, worker nymph, natural size; _C_, first form queen,
approximately natural size, with wings placed in their natural
resting position. (Drawing courtesy of C. O. Mohr.)]
[Illustration: Fig. 34.--Orthoptera. _Melanoplus bilituratus_, the
migratory locust, a common Illinois grasshopper. Actual length about
1.0 inch.]
Isoptera
Termites
Fragile or soft insects with chewing mouthparts. The mating forms are
dark brown and have two similar pairs of wings; both pairs are delicate
and have a fine network of veins. The workers are white and soft bodied.
Termites, which live in colonies in wood, are also called "white ants,"
although they are not true ants. The common native species in Illinois
is _Reticulitermes flavipes_ (Kollar), fig. 33, which lives in rotten
logs and is destructive to buildings of wooden construction throughout
Illinois; it is most destructive in the southern part of the state.
[Illustration: Fig. 35.--Orthoptera. _Ceuthophilus maculatus_, a
wingless cave cricket. Crickets of this kind are found in caves,
under rocks, and in basements. Actual length about 1.0 inch.]
[Illustration: Fig. 36.--Dermaptera. _Labia minor_, an earwig
frequently abundant in Illinois. Actual length of adult about 0.2
inch.]
Orthoptera
Grasshoppers, Crickets
Terrestrial insects usually with two pairs of wings, each wing with a
very fine, dense network of veins, the front pair thick and leathery,
the hind pair delicate and fanlike. The mouthparts, fitted for chewing,
have stout mandibles. The young look and act like the adults but do not
have wings. This order includes all the grasshoppers, crickets, and
katydids. Fig. 34 shows the migratory locust or grasshopper, _Melanoplus
bilituratus_ (Walker). Adults of several of the groups of Orthoptera
never develop wings. These include such odd forms as the cave crickets,
exemplified by _Ceuthophilus maculatus_ (Harris), fig. 35.
Dermaptera
Earwigs
Insects with two pairs of wings, the front pair forming short, hard
covers, the second pair large, membranous, many-veined, and in repose
folded intricately beneath the front pair. The abdomen ends in a pair of
pincer-like structures. A common Illinois form is _Labia minor_
(Linnaeus), shown in fig. 36. Of the half-dozen species known from
Illinois, all but one were originally from Europe or Asia. Earwig
females lay eggs in chambers in the ground and guard them.
[Illustration: Fig. 37.--Plecoptera. _Isoperla confusa_, one of the
typical stoneflies found in Illinois; adult form. Actual length
about 0.8 inch. Illinois stoneflies range in length from 0.25 inch
to 1.5 inches.]
[Illustration: Fig. 38.--Plecoptera. _Isoperla confusa_; the nymph
of the species shown in fig. 37. The nymph lives in streams. Actual
length about 0.6 inch.]
Plecoptera
Stoneflies
Insects that pass the young or nymphal stage in streams. They have
slender, soft bodies and long tails; they move about rapidly. The adults
are terrestrial in habit and occur along streams. In most species, the
adults have two pairs of wings that are folded flat over the back; the
number of crossveins varies from many to few. The antennae are long; the
mouthparts are of the chewing type but greatly reduced. Of exceptional
interest are stonefly adults that emerge in winter and are active from
November through March. The winter forms can often be collected on
bridges. Figs. 37 and 38 illustrate a spring species, _Isoperla confusa_
Frison.
Zoraptera
Zorapterans
Small, whitish insects, about a twelfth of an inch long, that run
rapidly. They live in small colonies in rotting sawdust, in rotten logs,
and under the bark of stumps. They have fairly long antennae, chewing
mouthparts, and a pair of short, inconspicuous tails. Most members of a
colony are wingless, but occasionally there occurs a darker specimen
having two pairs of wings. These wings have only a few veins. In
Illinois only a single rare species has been found; it is called
_Zorotypus hubbardi_ Caudell, fig. 39.
Corrodentia
Booklice, Barklice
Small, rounded or flattened insects, rarely a quarter-inch long, usually
about 0.13 inch. In many species, adults have two pairs of wings, which
have only a few zigzagging veins. Winged forms, such as _Psocus
striatus_ Walker, fig. 40, are found in crevices of bark and on dead
leaves. Common species found in houses and on stored grain are usually
wingless and louselike, similar in general appearance to fig. 41.
Corrodentia eat fungus growth on bark, dead leaves, moldy grain, damp
books, and similar materials. Some of the outdoor species become very
abundant on drying corn leaves during autumn and may breed in immense
numbers. They do little harm, feeding chiefly on fungus strands.
Phthiraptera
Chewing Lice, Sucking Lice
Wingless, blind, flattened insects with short antennae, short legs,
inconspicuous mouthparts, and no tails on the posterior end of body.
They are found exclusively on the bodies of birds and other warm-blooded
animals. The young have the same general shape and habits as the adults
and are found with them. Illinois species of lice belong to two distinct
suborders, which may be differentiated through use of the following key:
[Illustration: Fig. 39.--Zoraptera. _Zorotypus hubbardi_, the only
zorapteron recorded from Illinois. The specimen on the left is a
winged adult female; the specimen on the right is a wingless adult
female. Actual length of adults about 0.08 inch.]
[Illustration: Fig. 40.--Corrodentia. _Psocus striatus_, a common
bark louse found on many trees. Actual length 0.2 inch.]
[Illustration: Fig. 41.--Phthiraptera. Suborder Mallophaga.
_Cuclotogaster heterographus_, a chewing louse found on the heads of
poultry. Actual length about 0.1 inch.]
[Illustration: Fig. 42.--Phthiraptera. Suborder Anoplura.
_Haematopinus asini_, the blood-sucking horse louse. Actual length
0.1 inch.]
Legs fitted for running, as in fig. 41, without Suborder
large pincers at their ends; mouthparts situated Mallophaga
near the middle of under side of the head and
fitted for chewing. Occurring on birds and
mammals. The chewing lice
Legs fitted for clinging to hairs, each leg Suborder Anoplura
ending in a large pincer, as in fig. 42;
mouthparts retracted within head, consisting of a
set of thin, needle-like parts fitted for sucking
blood. Normally occurring only on mammals. The
sucking lice
_Suborder Mallophaga._
Individuals of many species of chewing lice move about with considerable
rapidity. Many of them are very prettily banded and colored, as is the
chicken head louse, _Cuclotogaster heterographus_ (Nitzsch), fig. 41.
Anyone who has worked with domestic fowls or animals has seen members of
this order scurrying among the feathers or hair. These insects feed on
what they can chew from the surface of the skin and in some cases are
known to injure their hosts.
_Suborder Anoplura._
The sucking lice are sluggish insects that usually cling to hairs. Human
lice are often found clinging to clothing. Various species occur on
native and domestic species of mammals in Illinois. Fig. 42 shows the
horse louse, _Haematopinus asini_ (Linnaeus).
Thysanoptera
Thrips
[Illustration: Fig. 43.--Thysanoptera. _Thrips tabaci_, onion
thrips. Actual length less than 0.1 inch.]
Small, active insects, usually about 0.1 inch long, rarely a
quarter-inch long, very slender, usually each with two pairs of narrow
wings and with the under side of the head forming a sharp, conelike
sucking structure. Each wing has a long fringe on the hind margin; each
front wing may have one or two veins running the length of the wing. The
young of these insects are somewhat similar to the adults but are softer
bodied. Fig. 43 shows an adult of _Thrips tabaci_ Lindeman, the onion
thrips. Thrips suck the juice from plants. Because of their minute size,
they are seldom noticed, but they can be collected in large numbers from
blossoms of almost any plant. A few species of thrips, such as the onion
thrips and the privet thrips, attack agricultural or horticultural
plants and inflict considerable damage. A few species occasionally bite
human beings.
Hemiptera
True Bugs and Their Allies
Insects usually with two pairs of wings and with the mouthparts formed
for sucking. The order contains two distinct suborders, the Heteroptera
and the Homoptera. All species of Hemiptera in North America fall
readily into one suborder or the other, but certain species in other
parts of the world are intermediate between the two suborders.
[Illustration: Fig. 44.--Hemiptera. A typical stink bug of the
family Pentatomidae, showing attachment of beak and arrangement of
wings. Actual length about 0.4 inch.]
In the suborder Heteroptera, containing the stink bugs, the chinch bugs,
and their allies, the beak is attached to the under side of the front
part of the head; the base of the front pair of wings is hardened, and
only the apical portion is membranous or delicate; the entire hind pair
is delicate. In repose, the wings are folded over and flat against the
body, the hind pair underneath. These characters are shown in fig. 44,
which pictures a stink bug belonging to the family Pentatomidae. The
young have the same general appearance and habits as the adults, but
they lack wings. This suborder includes many common kinds, such as the
water bugs, the water striders (these seldom develop wings even in the
adult stage), the ambush bugs, and the lace bugs, as well as the stink
bugs and the chinch bugs. The chief pest of this group is the chinch
bug, _Blissus leucopterus_ (Say), fig. 45. Other pests include many
kinds of plant bugs, of which _Lygus lineolaris_ (Beauvois) is shown in
fig. 46. The bed bugs, another group never developing functional wings,
also belong in this suborder.
[Illustration: Fig. 45.--Hemiptera. _Blissus leucopterus_, the
chinch bug. Actual length about 0.1 inch.]
[Illustration: Fig. 46.--Hemiptera. _Lygus lineolaris_, the
tarnished plant bug. Actual length about 0.2 inch.]
[Illustration: Fig. 47.--Hemiptera. _Anuraphis maidiradicis_, the
corn root aphid. The form at the left is the winged form; that at
the right is the wingless form. All of the plant lice have these two
forms. This species, as well as other kinds of plant lice, is
frequently attended by ants, which feed on the honeydew produced by
the aphids. Actual length less than 0.1 inch.]
Members of one family, the Reduviidae or assassin bugs, prey on other
insects. A few species called kissing bugs, some of them an inch long,
occasionally attack people, inflicting an extremely painful bite and
causing considerable bleeding.
[Illustration: Fig. 48.--Hemiptera. _Aspidiotus perniciosus_, the
destructive San Jose scale. The scale is cut away on upper specimen
to show insect proper beneath. Diameter less than 0.1 inch.]
[Illustration: Fig. 49.--Hemiptera. _Empoasca fabae_, the potato
leafhopper. This species is pale green. Some species are
distinguished by bright red or yellow markings. Actual length about
0.1 inch.]
[Illustration: Fig. 50.--Megaloptera. The larva of a species of
_Sialis_, an alderfly. This form is aquatic. Actual length 0.7
inch.]
[Illustration: Fig. 51.--Megaloptera. The adult of _Sialis mohri_,
an alderfly. Other members of this order reach a length of 1 or 2
inches. They are mostly black, black and white, or mottled gray in
color. Actual length 0.5 inch.]
The suborder Homoptera contains the cicadas, aphids, and their allies.
All these insects have sucking mouthparts, but in each the beak is
attached at the back of the head instead of the front of the head as in
the suborder Heteroptera. In many species of the Homoptera, each
individual has two pairs of wings, both of which are membranous.
Probably as many species are without wings, however, as with them. The
nymphs are in most respects similar to the adults. Sexual characters,
and in some forms wings, gradually develop as the insects approach the
adult stage, when development is complete.
[Illustration: Fig. 52.--Neuroptera. _Chrysopa nigricornis_, a green
lacewing. When handled, members of this genus give out a very
penetrating and disagreeable odor. Actual length 0.6 inch.]
[Illustration: Fig. 53.--Neuroptera. A larva of the genus
_Chrysopa_. This form uses the long jaws to impale aphids and suck
their body juices. Actual length 0.5 inch.]
This suborder contains a large number of economic pests, including scale
insects and leafhoppers, as well as many aphids. In many species of
aphids each insect has a pair of tubular structures near the end of the
body; these are called cornicles and can be seen in fig. 47, showing the
corn root aphid, _Anuraphis maidiradicis_ (Forbes). In most species of
scale insects each individual produces a tough scale, which covers and
protects its delicate body, as in fig. 48, showing the destructive San
Jose scale, _Aspidiotus perniciosus_ Comstock. Leafhoppers of many
kinds, such as _Empoasca fabae_ (Harris), fig. 49, are among the
destructive pests of beans, potatoes, grapes, apples, and other plants.
The treehoppers, spittlebugs, and lanternflies also belong to this
suborder.
Megaloptera
Alderflies, Dobsonflies
In this and in the following orders of insects, the life history
includes four distinct stages, the egg, the larva, the pupa, and the
adult. In the Megaloptera, which include alderflies and dobsonflies, the
larvae are caterpillar-like or grublike, and the pupae represent a
transformation stage in which the tissues of the larvae are converted to
those of the adults. The larvae never have external wing pads; in winged
species, these pads first appear externally in the pupae. The adults
have long antennae, two similar pairs of net-veined wings, and chewing
mouthparts. They are moderately strong fliers. The larvae, fig. 50, live
in streams and lakes; when fully grown they migrate to dry land and
pupate in the ground or under the bark of rotten logs.
Typical of the appearance of Illinois alderflies is the adult of _Sialis
mohri_ Ross, shown in fig. 51. Well known to the fisherman is the
hellgrammite, the tough, ferocious, leathery larva found under rocks in
streams and prized for bait. This larva matures into the large
dobsonfly, _Corydalis cornuta_ (Linnaeus), which often attains a
wingspread of 4 inches.
Neuroptera
Lacewings and Their Allies
Insects with two pairs of wings, both pairs about the same size and
shape and intricately netted with veins; antennae long and slender,
mouthparts fitted for chewing, posterior end of body without tails. The
green lacewings, including _Chrysopa nigricornis_ Burmeister, fig. 52,
are our commonest members of this order. The young or larvae of this
order are entirely unlike the adults and are somewhat grublike in form.
The aphid lion, the interesting larva of _Chrysopa_, fig. 53, is
frequently collected by the sweeping method. Another interesting larva
of this order is the doodlebug or ant lion, of Huckleberry Finn fame.
The adult insects that mature from these ant lion larvae are very
similar in appearance to the chrysopids or lacewings. The larva of each
of these insects sinks its long, sharp, curved mandibles into the body
of its prey and sucks out the body juices. The female _Chrysopa_ has the
curious habit of forming a long, slender stalk under each egg; the
bottom of the stalk is fastened to the upper side of a leaf. The stalks
are thought to have the effect of keeping the first larvae of a hatch
from devouring the eggs placed nearby.
When the larva is mature, it spins a globular, silken cocoon or cell
around itself and in this changes into the pupal, or quiescent, stage.
While the pupa itself does not appear active, within it the larval
tissues are reorganized into the structures of the adult, and the final
growth of the wings and reproductive organs occurs. When this change is
completed, the adult insect emerges from the cocoon.
[Illustration: Fig. 54.--Coleoptera. _Copris minutus_, one of the
scarab beetles. The drawing shows one of the elytra upraised and
illustrates the method of folding the hind pair of wings under the
elytra. Actual length 0.4 inch.]
[Illustration: Fig. 55.--Coleoptera. A weevil belonging to the genus
_Curculio_, which feeds on nuts and acorns. In this genus the beak
is exceptionally long. In most of the Illinois weevils the beak is
shorter and stouter. Actual length 0.4 inch.]
Coleoptera
Beetles, Weevils
Insects with two pairs of wings, the second pair delicate and folded
under the first pair, which are hard and thickened and folded back
against the body, touching each other along the midline to form a hard
shell, as shown in _Copris minutus_ (Drury), fig. 54. The upper wings
are not used for locomotion, but form part of the body armor and are
called _elytra_. In most beetles they cover the entire posterior part of
the body; in many others they are abbreviated and cover only part of the
abdomen. The immature stages of the beetles are wormlike or grublike and
have a great variety of food habits. Some of them defoliate plants,
others attack roots, and still others feed on other insects.
A great many of the serious insect pests, including kinds that attack
field crops, stored products, and household goods, are beetles. Beetles
of one group having the front of the head produced into a snoutlike
structure, as in the genus _Curculio_, fig. 55, are called weevils or
snout beetles. This group has maggot-like larvae and contains many of
our worst pests, such as the plum curculio, cotton boll weevil, alfalfa
weevil, and clover weevil. Bizarre and striking forms occur in many
beetle groups, notably among the scarab and long-horn beetles. The
largest in Illinois is the rhinoceros beetle, _Dynastes tityus_
(Linnaeus); the males (one shown on the cover of this circular) have
long projections on both head and thorax; the larvae live in rotten
wood.
Tree-boring beetle larvae are destructive to many orchard, ornamental,
and native trees. These include chiefly the round-headed borers, adults
of which are long-horn beetles; flat-headed borers, adults of which are
metallic wood borers; and engraver or shot-hole types, adults of which
are small and bullet shaped and are called bark beetles.
In a few families of beetles, both the adults and larvae are fitted for
aquatic life. Well known among these are the shining whirligig beetles.
Hymenoptera
Bees, Wasps, Ants, Sawflies
Insects typically with two pairs of wings; antennae of various lengths;
chewing mouthparts; without tails. A typical member of this group is the
wasp _Vespula maculata_ (Linnaeus), fig. 56. Many adult members of the
group are atypical in that they lack wings; these include all the true
ants, fig. 57, which are without wings except for the sexual forms
produced at the time of the nuptial flights. Forms of one species,
_Lasius interjectus_ Mayr, are shown in fig. 58. The wings, when
developed, are without scales; the venation is much less extensive than
in the Neuroptera; and the hind wings differ in shape and size from the
front wings. The young stages of the Hymenoptera are caterpillar-like or
grublike, entirely different from the adults.
This very large order includes such well-known forms as the bees, as
well as the wasps and the ants, mentioned above. In addition, it
includes the sawflies, whose caterpillar-like larvae are extensive
defoliators of a large number of native and cultivated plants and
shrubs; the large and varied groups of parasitic wasps that exert great
influence in the natural control of a tremendous number of other
insects; and a large number of gall-making wasps, whose galls are
especially conspicuous on oak trees. A parasitic wasp of the genus
_Opius_ is shown in fig. 59. The parasitic wasps are extremely diverse
in size, shape, and habits. They range in size between 0.02 and 2.0
inches.
[Illustration: Fig. 56.--Hymenoptera. _Vespula maculata_, the common
bald-faced hornet. Actual length 0.8 inch.]
[Illustration: Fig. 57.--Hymenoptera. A worker ant belonging to the
genus _Formica_. This form lacks wings. Actual length 0.3 inch.]
Mecoptera
Scorpionflies
Insects typically with two similar pairs of delicate wings, each wing
with a network of veins. In repose the wings are laid either tentlike
over the back or almost flat. The mouthparts are fitted for chewing and
usually are lengthened into a beaklike structure, as in _Panorpa
chelata_ Carpenter, fig. 60. The larvae, seldom found, live in damp
woods. The adults of most winged species occurring in Illinois are about
0.5 inch long. They are active in early summer in shady woods, flying
through the undergrowth. Adults of the genus _Boreus_ are smaller and
they have very short, veinless wings. They emerge in the winter and
early spring; these little metallic black insects often hop around on
late winter snow. In certain genera, the adult male genitalia form a
bulb-like structure at the end of the body, as in fig. 60. This
structure is harmless but, because it resembles a scorpion's sting,
insects of these genera are given the name scorpionflies.
[Illustration: Fig. 58.--Hymenoptera. _Lasius interjectus_, a
harmless winged ant, the yellow ant, with which the winged termite
is often confused: _A_, queen with wings spread, many times natural
size; _B_, worker ant, natural size; _C_, queen, approximately
natural size, with wings partially closed and as usually seen. Ant
has a narrower waist and shorter wings than termite. Actual length
of queen about 0.3 inch.]
[Illustration: Fig. 59.--Hymenoptera. A parasitic wasp, _Opius_, sp.
Actual length 0.1 inch. (Drawing from U. S. D. A.)]
[Illustration: Fig. 60.--Mecoptera. _Panorpa chelata_, one of about
15 Illinois species of scorpionflies. Only the male has the
"scorpion" tail. Actual length of insect about 0.5 inch.]
Trichoptera
Caddisflies
Insects with two pairs of wings, poorly developed mouthparts of the
chewing type, and long antennae; without tails on the posterior end of
the body. In repose, the wings are held rooflike over the body and have
only a moderate number of longitudinal veins, which are not connected by
crossveins into any resemblance of a network. Neither body nor wings are
covered with scales. The larvae are wormlike and they live in streams,
ponds, and lakes. Many of them build cases of sticks, stones, or sand
and move about with only the front end of the body protruding from the
case. When disturbed, the larvae withdraw completely into the cases and
are then very difficult to see. The adult fly and larva of _Rhyacophila
fenestra_ Ross illustrate this order, figs. 61 and 62. In many aquatic
situations, caddisflies are the predominant small animal life and are an
important factor in fish food economy. Also, they are stream pollution
indicators.
[Illustration: Fig. 61.--Trichoptera. _Rhyacophila fenestra_; the
adult form of this caddisfly is shown here. Actual length about 0.4
inch.]
[Illustration: Fig. 62.--Trichoptera. _Rhyacophila fenestra_; the
larva, shown here, is aquatic and builds no case. The larvae of some
other kinds of caddisflies live in cases made of sticks and stones.]
Lepidoptera
Butterflies, Moths
Insects typically with two pairs of wings, with long antennae, and with
mouthparts forming a long sucking tube. The body and wings are covered
with a dense mass of scales, which are characteristic of this order,
fig. 63. The young are known as caterpillars or grubs. The larval stage
in this order is well exemplified by the fairly smooth, cylindrical
caterpillar of the fall armyworm, _Laphygma frugiperda_ (Smith),
fig. 64. Some other larvae are hairy; still others are sluglike.
[Illustration: Fig. 63.--Lepidoptera. A typical moth, showing scales
on wings and body, and sucking tube, which is coiled up under the
head when not in use. Species of this order occurring in Illinois
include specimens that vary in size from 0.1 inch to several inches.
The largest of these insects have a wingspread of over 5 inches.]
To this order belong not only a very large number of species, but also a
very large number that are especially injurious to agriculture. These
include such species as the codling moth, cabbage moth, butterflies, the
entire cutworm group, and a host of others. In addition, the various
clothes moths, which are a constant source of loss to householders, and
various species of meal moths, which cause tremendous damage to stored
grain every year, are members of this order.
[Illustration: Fig. 64.--Lepidoptera. _Laphygma frugiperda_, the
fall armyworm: _A_, egg mass on leaf; _B_, top and side view of
individual eggs; _C_, adult; _D_, larva; _E_, pupae. Wing span of
adult about 1.5 inches. (Drawing from U. S. D. A.)]
In one group of moths, there are clear "windows" on the wings, but these
are always surrounded by areas or lines of scales. A few species of the
Lepidoptera are very odd in having wingless females. Examples are the
bagworms and some of the cankerworms. In these species, however, the
body of the female is densely clothed with scales, which will serve to
identify her as one of the Lepidoptera.
The habits of Lepidoptera larvae are very diverse. Most of these larvae
are leaf eaters, but some bore into trunks of trees and stems of
herbaceous plants. Some of the small ones mine within leaf tissue,
others live in the ground, where they eat roots, and a few are aquatic,
living in clear, rapidly flowing streams.
Diptera
Flies, Mosquitoes, and Their Allies
Insects with only one pair of wings, each wing with a limited number of
veins. Other characters of the order, including antennae and mouthparts,
are extremely varied. Most immature stages are wormlike or maggot-like.
They live in protected situations, such as within the tissues of a
plant, in water, in leaf mold, or in the tissues of animals. A typical
life cycle is that shown for the house fly, _Musca domestica_ Linnaeus,
fig. 65. The ubiquitous house fly is undoubtedly the best known
representative of this order. It is also one of the most persistent and
dangerous insect pests, being a possible carrier of many diseases.
[Illustration: Fig. 65.--Diptera. _Musca domestica_, the house fly.
The fly has only a single pair of wings; the pale, maggot-like larva
is without legs; the darker, egg-shaped puparium contains the pupal
or quiescent stage. Length of adult 0.2 inch. (Drawing by Alice Ann
Prickett.)]
Mosquitoes, punkies, black flies, and horse flies are likewise well
known members of this order. In addition to economic forms, the order
Diptera includes midges, crane flies, bee flies, robber flies,
bluebottle flies, and a great assortment of other kinds of insects.
Interesting are the bee flies, which mimic other insects such as honey
bees, bumble bees, and wasps to an extent that wins them immunity from
the attention of many beginning collectors.
Siphonaptera
Fleas
Wingless insects that evolved from folding-wing insects; conspicuously
flattened from side to side; with stout spiny legs, and with numerous
spines over the body; without conspicuous antennae or tails or a forked
posterior appendage like that of the springtails; usually hard; ranging
in color from yellowish brown to almost black.
The human flea, _Pulex irritants_ Linnaeus, and a widespread Illinois
rat flea, _Nosopsyllus fasciatus_ (Bosc), are shown in fig. 66.
All the fleas, which feed on the blood of birds and other animals, have
sucking mouthparts. They are powerful jumpers. The young stages are
slender, white larvae, fig. 67, which live in the nests of various
animals; these larvae are seldom collected. The fleas are found on the
animals themselves or around their nests. Several species of fleas,
including the cat and dog flea, the human flea, and the rat fleas,
attack man. One of the rat fleas, _Xenopsylla cheopis_ (Rothschild) is
the common transmitter of the organism causing bubonic plague.
[Illustration: Fig. 66.--Siphonaptera. _Pulex irritans_, human flea
(left), and _Nosopsyllus fasciatus_, one of the rat fleas. Actual
length of body about 0.1 inch.]
[Illustration: Fig. 67.--Siphonaptera. Larva of flea found in mouse
nest. Length about 0.12 inch.]