FROM BUTTERFLIES TO BEETLES AND BEES
The generally accepted classification of the insects divides them into
more than twenty orders, and these into hundreds of families whose
species, already catalogued, are three times as numerous as all other
known animals together. "There are, for example," as Lutz remarks,
"15,000 species of insects to be found within fifty miles of New York
City; more than 2,000 of these are either moths or butterflies."
Insects as a class are characterized primarily by the division of the
body, when adult, into three clearly defined regions--the head, the
thorax or fore body, and the abdomen or hind body. All insects have
three pairs of legs, distinguishing them from the eight-legged spiders,
and from the many-footed myriapods and other arthropods, and most of
them have one or two pairs of wings, borne like the legs on the thorax,
the abdomen never bearing either. The head consists of four segments,
but in most cases the first three are consolidated into the hindmost,
and are represented only by the appendages they bear. The foremost of
these are the mouth organs, of which there are three pairs: the most
anterior are the mandibles, next the maxillæ, and then the labium,
the two latter bearing articulated prolongations known respectively
as maxillar and labial palpi. The mouth has an upper lip (labrum) and
contains a tongue. These mouth parts are variously modified, and by
these modifications insects may be classified in two groups: "First,
those in which the jaws and maxillæ are free, adapted for biting, as
in the locust or grasshopper; and second, those in which the jaws and
maxillæ are more or less modified to suck up or lap up liquid food, as
in the butterfly, bee, and bug." It is in this latter group that we
find those having those interesting relations with plants that result
in cross-fertilization of flowers.
[Illustration: A FLORIDA KATYDID
(_Cyrtophyllus floridensis_)]
From the forehead spring a pair of antennæ, which are not only
"feelers," but the bearers of other senses. They are jointed, and
exceedingly various in form and service. Some are mere stubs, others
long and slender as a whiplash, or they may be thickened at the end,
as commonly in butterflies, or bear rows of hairs on each side, giving
them in some cases a beautiful plumelike appearance. With their
antennæ insects inspect by touch whatever they come in contact with,
and test the shape of what they may be constructing, such as cells
for their eggs. They recognize one another, and apparently exchange
communications, or become aware of a stranger, and the ants induce
their captive aphids to let down the honeydew by stroking them with
their antennæ; but in many of these cases, if not all, additional
information is derived through the antennæ by reason of the senses of
hearing and of smell which many of them certainly possess. Ears, or
organs sensitive to vibrations, and delicate hairs and other processes
connected with nerves responding to touch are found in various other
parts of insects' bodies, but the feelers are preeminently the seat of
the sense of smell.
The eyes of insects are of two kinds, simple and compound. The simple
eyes are small and practically useless single ones (ocelli) situated
in a triangle of three on the top of the head. The compound eyes are
on the side of the head, and are covered by a transparent layer of
the chitinous skin (cornea), divided by delicate lines into square
areas (facets). Beneath each facet of the cornea is an "ommatidium,"
optically separated from its neighbors by black pigment, and consisting
of an outer segment or "vitreous body" and an inner segment or
"retinula" formed of sensory cells. In some such eyes the ommatidia
are few, but in others extremely numerous, so that the eyes cover a
large space; some hawk moths are said to have 27,000 facets. The
nature of the picture conveyed to the mind by such an eye has aroused
much discussion. Photographs taken through the eye of a dragon fly show
that, though the eye is compounded of many lenses and sensitive areas
(retinulæ) corresponding to them, yet the whole eye throws one image
on the retina. However complex such an eye may be, it is devoid of any
focusing arrangement and can only receive a clear image when the retina
and the object are separated by the focal length of the lenses. Hence
the need for active movement on the part of creatures having them.
The head is connected with the thorax by a neck often protected by the
overlapping front of the "tergum," or chitinous plate that covers the
thorax. The thorax consists of three segments, named from the front
backward "prothorax," "mesothorax," and "metathorax." These and a few
other technical terms are in such constant use in describing insects
that it is important to know them. The under (ventral) surface of the
thorax is protected by another plate named "sternum." The armor is not
continuous all around the body as in the crustaceans, but that on the
upper surface is connected with the sternum by a seam of soft skin
along the sides of the body.
Each segment of the thorax bears a pair of legs, each of which consists
of a stout, flattened "coxa," nearest the body; a small second part,
the "trochanter"; a third, the "femur"; a fourth, the "tibia"; and
finally the "tarsus," or foot, terminating in a pair of claws, bristly
on their under surface to give adhesive power. It is by means of these
stiff hairs, and not by any suction or stickiness, that flies are able
to walk on the ceiling and on vertical surfaces.
The wings of such insects as fly arise from the tergum of the thorax,
and are in two pairs except in the flies, where there is but one,
the hinder pair being represented by two little protuberances called
"halteres." Usually the wings are strengthened by rods called "veins,"
and the patterns of venation vary in different groups, and form one of
the means of classification.
The abdomen consists normally of ten segments, and contains most of the
digestive and all of the reproductive organs, above which runs the main
blood vessel, and below it the highly organized nervous system, the
chief ganglion of which, in the head, is termed "brain."
The breathing of insects, although rhythmical in its inhalation and
alternate exhalation, is not to the same purpose as ours. Respiration
goes on by means of a system of branching tubes (tracheæ) that ramify
throughout the body, and to which air is admitted through nine or more
openings in the side of the body guarded by valves called "spiracles."
The buzzing of flies, "singing" of mosquitoes, and the like, are sounds
made in these spiracles, not by their rapid wings. At intervals the
tracheæ are enormously enlarged to form air sacs. These no doubt,
lighten the body, but they probably serve also to provide a reservoir
of air from which the fine branches are filled by diffusion, and into
which the carbon dioxide is discharged. The circulation of oxygen in
adult insects, however, is never by means of the blood, but simply
by absorption by the tissues into which the excessively attenuated
tracheal tubes penetrate.
Insects are bisexual, and male and female are always separate
individuals. Except in a few abnormal cases among the most lowly, eggs
are produced and deposited in some favorable place for hatching.
SOME PRIMITIVE GROUPS
Insects go back in geologic history to the middle of the Paleozoic
age, and their remains are numerous and much differentiated in
Carboniferous rocks, when the orders Aptera, Orthoptera, Neuroptera,
and Hemiptera (the last represented in the Silurian by ancestral forms
of the bedbug and the cockroach--the oldest fossils yet discovered)
were flourishing. The beetles and ants first appear in the Trias, the
true flies, in the Jurassic, and the butterflies and moths, wasps, and
bees not until the Tertiary. This indicates an evolutionary progress
in structure with advancing time, as elsewhere in biology. The most
primitive type (Aptera) is still with us in the skipping silver fish
and snow fleas, or spring-tails, that annoy us in various situations.
They are wingless, very simple in organization, and without any
larval metamorphosis. Not much better are the Mayflies, or dayflies
(Ephemeridæ), that sometimes in early summer arise in enormous numbers
from lake shores and rivers, and then quickly disappear. Most of them
live, in truth, only a single day (or night), a single one of the many
American species surviving three weeks. During their brief life the
female drops into water several hundred eggs where they presently hatch
into swimming or crawling larvæ that next year, or perhaps not until
the third spring, creep out on land, molt, and fly abroad in ephemeral
crowds.
It is not a long step from these Mayflies to the dragon flies and
damsel flies (Odonata), which also belong to the water spaces of the
country, and are among the most interesting of all the insect tribes,
and the most beautiful, as they dart and curvet over the surface of
some glassy pool that reflects the steel-blue or peacock-green sheen
of their long slender bodies, and the black bars that alone make their
narrow and almost transparent wings visible. They are known by many
ridiculous names, as "darning needles," "snake doctors," etc., but
there is no harm in them; on the contrary they are to be encouraged,
for they consume, especially in their larval stages in the water, a
vast number of mosquitoes, gnats, and other troublesome "bugs." The
adults capture their food on the wing, and are hawklike in the agility
with which they turn and dodge in pursuit of their active prey. The
actual catching is done with the feet, which curve far forward, and
are studded with spines that give a sure grip on anything caught
between them; they assist, too, in clinging to plants, but the legs
are ill-adapted to walking. The wings are very powerful; are of a
glassy texture, and never folded; they are crossed by a great many
veins, breaking the surface into innumerable small squarish areas, and
bear markings that distinguish each of the two or three hundred North
American species.
Dragon flies, and their cousins, the smaller and more graceful,
low-flying damsel flies, pair as a rule in flight. In some of the
families the female descends below the surface of the water, and is
able by special apparatus to insert her eggs beneath the skin of a
plant; others place them in plant stems above the water, or simply drop
them at the surface, whence they sink to the bottom. The "nymphs," as
aquatic larvæ like this, with incomplete metamorphosis, are termed, go
about preying on anything they can seize and eat, and possess some very
peculiar temporary adaptations to their underwater career. After a time
the nymph (which is the "dragon" in dragon fly) changes from a rather
slender to a broad and flattened creature and crawls out of the water.
Soon its skin splits, and an adult dragon fly emerges.
Closely allied to the dragon flies are the stone flies, or alder flies
(Percoptera), whose ugly and predacious nymphs are so well known
to anglers as "dobsons," "crawlers," and by many other local and
opprobrious names, because they make excellent bait for still-water
fishing. The adult is that great, thin-winged creature called
"hellgrammite" (_Corydalis cornuta_), with a wing spread of four
inches, and possessed in the female of powerful biting jaws, which,
as in all insects, work horizontally and not up and down as among
vertebrates. In the male the jaws are extended into long, curved,
piercing organs which cross when at rest, and which are fully an inch
in length, but fortunately they are not used as jaws, but for holding.
Related to these is a group of well-known insects belonging to the
old order Neuroptera, but now placed in separate orders, all with
lacelike wings and an incomplete metamorphosis. They include the ant
lions, the useful aphis lions, the scorpion flies (Panorpa), the lovely
lace-winged flies, and the caddis flies, which make larval cases of
bits of stick, or of shells or fragments of stone, in the bottoms of
rapid streams. From somewhere in this group, probably, the ancestral
Lepidoptera branched off to develop into the butterflies and moths of
the present day. Next to them are the earwigs (Dermaptera), beetlelike
insects very conspicuous in Europe, but little noticed in this country.
A MUSICAL TRIBE
Out of this confusing array of rather primitive groups we come to an
extensive and well-defined order, the types of which are familiar to
the most careless of observers in all parts of the world. This is the
order Orthoptera, "straight wings," which includes the cockroaches,
mantids, walkingsticks, grasshoppers, locusts, katydids, crickets, and
their humbler kinfolk.
Cockroaches are native to all the warmer parts of the world, and we
have a common large brown one, and some others of our own; but the pest
of our kitchens is the small Oriental species whose origin was Asiatic,
and which probably accompanied the earliest westward wanderings of
mid-Asian men, and established themselves as boarders by the camp fires
of the cave men. At any rate, the "black beetles," as the British call
them--wrongly in both particulars--are now settled wherever ships have
gone or civilized goods have been carried. As they first began to be
really troublesome in New York City about the time when the Croton
water was introduced (1842) they got the local name "Croton bug," but
they are the world-wide _Blatta orientalis_, scampering around where
they are not wanted, carrying a queer packet of eggs under the tail.
[Illustration: TWO WALKINGSTICKS
(_Diapheromera femorata_)]
The mantids--of which a common species in the Southern States is known
as "mule killers" because of the superstition that its saliva poisons
stock--and the gaunt "walkingstick" insects that mimic twigs so well
that they are not seen as often as they might be, introduce us to the
great tribe of grasshoppers or locusts--two words that it has worried
bookmakers to keep straight. The grasshoppers fall into two families,
distinguished among other points by the length of the antennæ. The
short-horned ones (Acrididæ) are properly called locusts, and the
long-horned family (Tetigonidæ) are better known as grasshoppers,
despite the fact that until recently the books called this family
Locustidæ. To the Acrididæ belong the locusts that in years past have
worked such havoc now and then in the West, when vast swarms came from
the Rocky Mountains to the new farms along the eastern border of
the plains, and ate up the young grass and crops, leaving the ground
looking as if swept by fire. It is a story older than written history
in all plains districts of southern Asia, Asia Minor, Egypt, and
northern and south-central Africa, where no earthquake, or tornado,
or other reaction of nature against man's interference with natural
conditions, is so dreaded as a visitation of migratory locusts. In
this country any such "plagues" as half ruined Kansas forty years or
so ago need no longer be anticipated, because the plowing on ranches
and other disturbance of the ground in which the locusts lay their eggs
is now so extensive, and the methods of checking small flocks are so
well understood, that the vast surplus generations that constituted a
migration in search of food in the old days are no longer born.
All the Orthoptera are musical, or at any rate noisy, and make their
rattling or piercing notes as instrumentalists, not as vocalists.
"Some species," writes Frank E. Lutz, "make a rasping sound by rubbing
their hind legs against their front wings (tegmina). Others rattle,
while flying, their hind wings against the tegmina. These sounds
are primarily amorous serenades, and Nature's serenades without
attentive ears would be even more curious than the ears for which the
grasshoppers perform. In this family there is an auditory organ on each
side of the first abdominal segment, just above and back of the place
where the large hind femora start. Notice the clear round spot on the
next grasshopper you catch.... Few have not heard the masculine debates
as to whether Katy did or didn't, but many do not know by sight the
small, green, long-horned, stockily built disputants, both of whom
usually stay high in trees. The musical apparatus of the male--the
musician--is at the tegmina, and the leaflike wing covers, broadly
curving entirely around the body, act as sounding boards. The female's
wing covers do not have the thick rasp veins at their bases."
A third family, the Gryllidæ, contains the crickets--burrowing mole
crickets, ordinary black crickets dwelling in the herbage, and several
kinds of tree crickets that look like ghosts of their kind. All add to
the noise of a summer evening by rubbing the roughened surface of their
wing covers together--chirping to ears that are situated in the shins
of the listening cricketesses.
THE TRUE BUGS
Skipping the white ants or termites, which are few and comparatively
harmless in this country, but in the tropics make vast trouble for
house-holders; the various sorts of lice and the little black thrips
that destroys onions and some fruits, we come to the great assemblage
that entomologists call "bugs," limiting the word to the order
Hemiptera, which now must be considered.
The two features, basally common to all the immensely diverse members
of the order, are the character of: 1. The feeding organs; and 2. The
wings--in each case very distinct from that of all other insects. The
bugs have highly developed piercing and sucking jaws. The mandibles and
first maxillæ are transformed into stylets, often barbed toward the
tip; these work to and fro within the groove of a stout-jointed beak
(rostrum) which is formed by the union of the second maxillæ. The head
is usually triangular in shape, as viewed from above.
As to the second characteristic, the bugs are distinguished by the
modification of the fore wings into partly horny covers for the
entirely membranous hinder wings. This feature divides the order into
two suborders, Homoptera and Heteroptera. In the first this hardening
is little evident; but in the Heteroptera--where not wingless, as in
certain families--the fore wings are stiff and lie flat on the back
when closed, whereas in the Homoptera they are somewhat humped over the
back, and droop down on each side a little. The triangular space marked
on the back by the closed wings is a ready mark by which to recognize a
hemipteran, or true bug.
The Hemiptera display a greater diversity of form than any other order
of insects, and vary in size from almost microscopic scales to fat
cicadas and "giant" water bugs. "Some pass their lives in the upper
parts of trees, others chiefly on the lower limbs; still others prefer
the protection of roots, stones or rubbish on the ground; a large
number of species select a home beneath the surface of the earth,
often in the holes of ants or other insects; a conspicuous assemblage
of dull-colored forms occurs only in the crevices or under the bark
of trees and shrubs; while a host of others skim over the surface of
placid waters, and a few are found remote from land upon the rarely
disturbed waves of the tropical and subtropical oceans.... While the
greater number derive their food either from the sap of vegetables,
or the blood of fishes, animals and man, there are others which are
satisfied with the strong fluid that accumulates beneath damp, decaying
bark of trees, or still others which enjoy the juices of fungi or
ferns.... Those which creep about in search of living prey are often
furnished with curved or hooked forelegs, suitable for seizing and
holding creatures when in motion, such as caterpillars and other larvæ."
The Homoptera include the immense and destructive family Coccidæ,
the bark lice, scale insects, and mealy bugs, among which, however,
are the useful producers of lacs and such dyes as cochineal. Related
to them are the Aleyrodidæ, the destructive "white flies," and the
Aphidæ, almost infinite in number and in harmfulness to fruit trees and
cultivated plants; also the queerly shaped leaf hoppers and similar
minute, plant-sucking forms.
It is one of the curiosities of zoölogy that associated with these
minutiæ we find a family of bugs of large size--the cicadas, whose loud
"singing" by the male in autumn gives them the name "locust," and often
becomes annoying when one wants to sleep where trees are near by. The
noise is made by vibrating membranes stretched over a pair of sound
chambers, situated, one on each side, near the base of the abdomen.
The cicada lays its eggs in slits cut in the bark. The newly hatched
young drops to the ground and, burrowing into it, feeds by sucking the
juices of roots. The time spent in the ground varies according to the
species in various parts of the world. In the case of our "periodical"
cicada it lasts about seventeen years, whence we call that species
"seventeen-year locust," and know it, when a great swarm comes out of
the ground and ascends the trees, by the humming of the crowd which
sounds like the vibration of telegraph wires in the poles.
[Illustration: SEVENTEEN-YEAR LOCUSTS
1-4, pupæ, increasing in age; 5-15, the locust imago struggling out
of the pupa; 16, 17, 18, the imago stretching its wings; 19, empty
pupacase; 20, 21, perfect locust. (Smithsonian Institution.)]
The Heteroptera, or proper "bugs," are a much larger assemblage, a few
kinds of which have attracted popular notice. The long catalogue
begins with the small "water boatmen" that live an active predatory
life on the bottom of streams and ponds. Other common aquatic families
are the Notonectidæ, that swim on their backs, the Nepidæ, or "water
scorpions," one of whose genera is that of the slender, long-legged
"skaters" that glide so swiftly across the glassy surface of still
waters. Then there are the great water bugs (Belostoma), which all
over the world are the tigers of quiet rivers and ponds, pouncing from
their concealed lairs on even minnows, small frogs, and anything else
they can catch and kill. These great brown bandits are sometimes two
inches long. Some of the tropical species are strange in form and have
extraordinary habits in caring for eggs and young.
Leaving the aquatic group, we come to certain troublesome plant-sucking
bugs, and to the bedbug, which claims the longest lineage of any known
insect, for the remains of perfectly recognizable ancestors are found
in Ordovician rocks dating from early in the Paleozoic time. Skipping
the lace bugs, red bugs, or "cotton stainers," and others, we come to
a series of families that are among the worst pests of the farmer and
gardener, the chinch bug, squash bug, cabbage bug and many others, the
aggregate effect of whose ravages causes a loss of millions of dollars'
worth of crops every year, not only in this country, but everywhere
that grain, vegetables, and fruit are cultivated; and in most cases it
is not the native but introduced species that does the most damage.
GILDED BUTTERFLIES AND DUSTY MOTHS
The butterflies and moths, whose beauty attracts more collectors than
any other group of insects, constitute the order Lepidoptera, the
meaning of which term is "scaly winged," in reference to the fact that
the hairs that clothe and ornament the wings are scalelike. Butterflies
have club-shaped antennæ, and belong to the division Rhopalocera.
Moths are Heterocera. Some of the moths, especially the males, have
feathered antennæ, some threadlike, while a few tropical ones have
"club" antennæ, so that this distinction is not perfect. The pupæ
of butterflies are not protected by cocoons, as are those of most
moths, and are usually called "chrysalides" (singular, "chrysalis").
Butterflies in general only fly during the daylight, when few moths are
stirring, and usually hold their wings erect when at rest, while moths
hold them flat or folded against the body.
The Lepidoptera undergo a complete larval metamorphosis, and the
process is more familiar to general readers than in the case of
other insects. From the eggs, which are often objects of great
beauty when examined through a lens, are hatched wormlike creatures
that grow rapidly by repeated moltings of the skin into full-sized
"caterpillars"; those of certain moths develop in community nests,
but ordinarily they live singly. All have three pairs of thoracic
legs, and a variable number of temporary "prolegs" near the rear
of the body. Caterpillars may be smooth, round, and colorless, or
coated with a heavy fur, or bristling with knobs, tufts of hairs, and
other appendages, and brightly ornamented with color; and many of
these peculiarities appear to be wholly defensive in purpose. Some
caterpillars give off, when alarmed, disgusting and acrid fluids, and
the hairs of others irritate venomously the skin of anyone handling
them, and probably account for the fact that few birds will touch
certain species. All caterpillars feed voraciously--in fact, this is
the only time in the life of many species when food is taken, the adult
moths and butterflies as a rule being neither willing nor able to eat.
At a certain time, having completed its final molt, the caterpillar
arranges itself according to the custom of its race, and subsides into
a pupa.
[Illustration: CATERPILLAR OF THE MILKWEED BUTTERFLY
(_Anosia plexippus._) (Smithsonian Institution.)]
A century ago men interested in butterflies spoke of themselves
as aurelians, explaining that "aurelia" was a proper name for the
butterfly pupa because of the golden ornaments it usually bore. Really,
however, this characteristic, so marked in the gilt "buttons" of our
common milkweed butterfly, pertained to only a single family--the
Nymphalidæ. When the nymphalid caterpillar reaches the turning point,
it withdraws the abdomen a little from the cracking skin, exudes a
little sticky silk which it fastens to its support, then hooks the tip
of its abdomen firmly into this silk; this done, hanging thus by its
tail, the caterpillar finally shakes off its coat and, as a chrysalis
(a Greek word of the same general sense as the Latin _aurelia_) the
pupa hangs, head down and inert, until the following spring.
The butterflies of greatest size and most splendid coloring belong to
the family Nymphalidæ, whose hundreds of species are scattered all over
the warmer parts of the world. Here belong those gorgeous tropical
ones, whose wings, sometimes with a spread of five inches, emulate the
prismatic hues of the "eyes" in a peacock's tail, and which are so
often seen mounted as lovely ornaments in curiosity shops; and here
also is classified that strange "leaf butterfly" of Malaysia, whose
wings when closed so perfectly imitate a leaf of the tree on which it
alights that the sharpest eyes can hardly find it. Here, too, belong
our brown-streaked "fritillaries," such as the vanessas, and darker
ones like our mourning cloak, and many others well known to amateurs.
[Illustration: FINAL MOLTING OF A NYMPHALID CATERPILLAR
(a) Before shedding skin. (b) In act of shedding skin. (c) Trying to
catch hold of silk button. (Smithsonian Institution.)]
All of this family have their chrysalides hung by the tail; but in
the remainder of the butterfly families they are held in an upright
position by a loop of silk that passes around them like a girdle. Such
are the "coppers," the "blues," the "hair streaks" and many other
small, gayly colored species (Lycænidæ) common in summer, to which
season they add so beautiful an interest. In another large family, the
Papilionidæ, are found the great yellow and black "swallowtails," which
are almost exclusively American, and several dark blue or purple-marked
species, with "tails" to their wings, that attract the attention of the
most careless as they lazily flit among the flowers. In this family,
too, are the sulphur-yellow butterflies that dance over the roads and
fields in little flocks; and, alas, the white ones whose caterpillars
are so injurious to cabbages and similar vegetables. The last family
(Hesperidæ) contains small, rather obscurely marked, butterflies that
connect the Rhopalocera with the Heterocera, or moths.
[Illustration: CATERPILLAR BEGINNING ITS COCOON
Photo, A. N. Mirzaoff]
In fact the distinction between the two divisions of Lepidoptera is
one of convenience rather than of science, for it marks difference of
habits rather than of structure. Instead of a naked pupa, that of the
moth is inclosed in some sort of envelope called a "cocoon." This may
be an earthen cell underground, or a woolly tuft fastened to some such
support as the bark of a tree, or a leaf rolled and tied by silken
threads into a tube, or a burrow in dead wood, or a paperlike case
fastened to a twig; but in every case some special provision is made
for the easy emergence of the imago when the time comes for its birth
as a moth. The moths themselves do no harm. Their few weeks of life
are devoted entirely to mating and putting their eggs in just those
places where the larvæ they will never see can have the food proper for
them and the best chance for life--a matter of marvelous instincts and
adaptations. Few of them, except the hawk moths, eat at all. That is
done in the caterpillar stage, when many sorts become destructive of
the labor and hopes of the farmer and gardener and orchardist, or make
havoc in stores of grain and meal, and in garments of wool and fur,
carpets, and cabinets of natural history specimens.
[Illustration: MOTH AND EGGS
Photo, A. N. Mirzaoff]
Most of the moths are small, inconspicuous, grayish or brownish
creatures whose markings, very lovely when closely examined, so closely
resemble in their mottlings the places where the moths rest during the
day, that they are comparatively safe from the birds, monkeys and other
enemies that seek to catch and eat them. Some, however, are of large
size and brighter hue. Thus the silkworm moths of the Orient (and of
our own land) may measure four or five inches across the outstretched
wings, as does the cecropia and others that flit about evening lights;
and a near relative among us is the exquisite, long-tailed, luna moth,
which is pale green with chestnut edgings; many others in this group
are almost as "richy bedight" as butterflies. It is these that make the
large papery cocoons so easily seen in the fall in trees and bushes.
A remarkable family (Bombycidæ) is that of the hawk moths, which much
resemble in shape and action humming birds. They are day flyers,
but most active in the morning and evening twilights, and hover on
whirring wings before a flower, while with their long, tubular tongues
they suck its nectar, for these moths feed as well as do their fat,
uprearing, bulldoglike caterpillars, to which they owe another common
name for the family--that of sphinx moths. Their pupæ are lodged under,
on, or near the ground in a loose cocoon, and are to be recognized
by an appendage, curled around like a jug handle, in which lies the
chrysalis' long tongue.
FLIES AND THEIR HYGIENIC IMPORTANCE
Flies, scientifically speaking, are only those insects of the order
of Diptera, distinguished by having only one pair of fully developed
wings. They pass through a complete metamorphosis, and the larva is in
all cases a "grub" or "maggot" destitute of legs. It is rarely enclosed
in a cocoon but lies buried in the ground, floats in the water, or is
protected by the last larval skin which, separating from the pupa skin,
remains around it as a hard case. Flies and their larvæ live in the
most diverse manner. Some flies attack backboned animals and suck their
blood, some prey on smaller insects, some suck honey, and some find
their food in decaying animal and vegetable matter. A large number of
dipterous larvæ eat refuse, many feed inside growing vegetable tissues,
and some prey, or are parasitic, on other insects. More than 10,000
species of true flies have already been named in the United States
alone. The order contains all the different species and varieties of
fleas, mosquitoes, sand flies, gnats, midges and gall flies. Then come
the blood-sucking gadflies, and half a dozen families allied to them;
the scavenging syrphus flies, the bots that trouble cattle, the house
flies and stable flies of deservedly bad repute; and, lastly, the
horseflies, bee parasites, and botflies. The popular interest in these
insects is confined to the flies of our houses and stables, and to the
mosquitoes. In fact it is in the relation that the flies mentioned,
and some others, bear to public health and comfort, that this group of
insects is important at all to any but the special student.
BEETLES AND THEIR GRUBS
The beetles (order Coleoptera) make up a very distinct and natural
group of insects, characterized by the horny or leathery texture of
their forewings, or "elytra," which serve as cases for the folding
membranous hind wings alone used in flight. These elytra, when closed,
usually cover the whole hind body. They are strengthened with ridges
around their edges, and marked with a series of longitudinal furrows
and often also with impressed dots. The hind wings are sometimes very
small or wanting; in such cases the elytra are often fused together
along their middle edges (suture). The head is usually extended from
behind forward, having therefore a large crown and a small face; the
feelers are very inconstant in form; the mandibles are always developed
as strong biting jaws; the prothorax is free and movable; its tergite
(pronotum) is a very prominent feature in all beetles, reaching back to
the origin of the elytra.
The beetles undergo a complete metamorphosis, and the larvæ, called
"grubs," have various shapes, while the pupa is "free," that is,
closely similar in development and appearance to the adult. Beetles
are world-wide in distribution and more than 100,000 species have been
catalogued. They are divided into a great number of families, among
which those mentioned below contain the most noteworthy forms.
The tiger beetles are large-headed, predacious forms, most numerous
in the tropics, which live in holes in the soil and rush out to seize
passing prey. The ground beetles (Carabidæ) are a very extensive
family, represented in all parts of the world, and are insect hunters,
destroying hosts of injurious insects. Most of them are black or brown.
The Dyticidæ and Hydrophilidæ are aquatic families, including some
of the largest and fiercest of carnivorous beetles, the terrors of
ponds and marshes, where they prey not only on other insects and their
young, but on tadpoles, small fishes, etc.; and their grubs are quite
as savage. The rove beetles (Staphylinidæ) are a very large family of
narrow, elongated species, which are very active; they feed mostly on
small insects, worms and snails. The carrion beetles belong to the
family Silphidæ, the smaller among which live in moss and under tree
bark, and the larger genera contain the noted "burying beetles." Some
groups of very minute, ground-keeping species lead to the familiar
"ladybirds" (Coccinellidæ), a large and world-wide family of small,
rounded beetles, usually brightly spotted, which frequent plants of all
sorts, and feed chiefly on aphids. Some quaint superstitions pertain
to these pretty insects, that should be attracted rather than repelled
when they visit window gardens and greenhouses, which they will
endeavor to clear of the "greenfly" and similar injurious plant lice.
Passing over several inconspicuous families we come to the dermestids,
very small, dark-colored beetles of elliptical outline, some of whose
genera are among the worst of household pests, and have been spread by
commerce throughout the civilized world.
Some of the dermestids are troublesome as museum pests; others attack
food in the pantry, store, or warehouse. "Drugs do not escape their
attack, species devouring even cantharides and tobacco; woolen and silk
goods, feathers and furs, are ruined if left long exposed to their
depredations; and one species is accused of biting young doves....
_Anthrenus scrophulariæ_, probably introduced into America from Europe,
has received the names carpet beetle and buffalo bug, on account
of its habit, both as larvæ and imago, of destroying carpets. This
beetle measures about four-fifths of an inch in length, and is black,
brick-red and white, the last crossing the back in two zigzag lines.
The point of attack is the nailed-down edge or the lines of the seams."
Who has not been amused at the labors of the big black beetles that
one meets in summer on dusty paths rolling balls of fibrous material.
These "dung beetles" are the American cousin of the scarab of the
ancient Egyptians, which typified to them many mystical ideas connected
with life, present and eternal. With its shovellike head and broad
forelegs the beetle gathers and compacts the material it wants, and
begins to roll it, sometimes with the help, more often against the
struggles, of another beetle toward a prepared nest-hole. Arrived there
an egg may be inserted into it, and then the rounded mass is left as
food for the grub to be hatched from the egg; if no egg is inserted,
the ball becomes simply a mass of stored food to be eaten by its
maker. Processes vary among the 7,000 or more known species of this
cosmopolitan family.
Not all of this great family are dung beetles, however, or scarablike.
Here belong the May bugs and June beetles that come blundering around
lighted country residences in the evenings; and it is their fat white
grubs that, hatched from eggs buried in the ground, devour the roots
of the grass and other plants, spoiling the lawns and strawberry beds.
The robin is their most effective enemy. Among the lesser genera are
those of the rose bugs, hated pests of the horticulturist and fruit
grower. In that section of the family known as the cetonians are found
the giants of the race, the West African "goliaths," four inches long;
the tropical American Hercules beetle, exceeding six inches long, half
of which belongs to the forward-reaching horn of its helmet, the South
American elephant beetle which is even more bulky, and several other
giants, the males of which have the head ornamented with fearsome
protuberances.
Other families of beetles are the Buprestidæ, whose larvæ are injurious
to trees by boring into their wood; the Elateridæ, or snap beetles,
which arch their bodies and leap when they happen to fall on their
backs, and among which are found the many varieties of brilliant
"fireflies" for which the American tropics are famous. The larvæ of
the elaters mostly live in decaying wood, and are the justly hated
"wireworms" of our gardens. Then there are the Meloidæ, that include
the blister beetles, or oil beetles, one of which is the cantharides of
the pharmacopoeia; and there are a great many more.
HONEY MAKERS AND PLANT STINGERS
A long shelf is required in the naturalist's library for the books
relating to the Hymenoptera of America alone--our wasps, bees, ants,
and their smaller relatives, which engage everybody's attention by
their social habits and amazing display of instincts. Besides these
three principal and familiar groups the Hymenoptera include a host of
other insects of great but inconspicuous importance. In large part
these are parasitic on other insects or their larvæ, or even on their
eggs, and some are the most minute insects known, virtually invisible
to the unaided eye. Scarcely larger are the makers (Cynipidæ) of the
galls so commonly seen on trees and plants in which they breed. Another
group (Chalcidoidea) cause the swellings that disfigure plants by
placing their young within their tissues, such as the "joint worms"
that ruin grain; and here, again, many species are parasitic on grubs.
Then there are the sawflies (Tenthredinidæ), resembling bees, whose
ovipositors are like a pair of saws with which these insects are able
to bore holes into wood, within which the egg is placed and the young
larva burrows; of these are many and various kinds, all injurious to
trees, garden shrubs and plants, each kind restricted to a particular
sort of plant.
Perhaps even more numerous are the ichneumon flies, whose service in
the world seems to be to keep the insect hosts down to the number
possible to exist and at the same time to allow men and other animals
to live. Their method of life is to deposit their eggs on or in the
bodies of other insects, usually in the larval stage, where they
hatch and thrive by the slow death of the host. The ichneumon flies
are the dread of all other insects, most of whose adaptations for
self-preservation are directed against this insidious and universal
enemy to insect life.
None of the foregoing Hymenoptera live in colonies or by social
methods. That plan belongs to the four most advanced divisions--wasps,
bees, termites, and ants. Even among the wasps and bees, however, the
larger number of species live alone or in single families, each female
constructing a solitary receptacle for her purpose underground, in
soft wood or otherwise. Most species store with the egg placed there
half-dead insects, or pollen, etc., as food for the grub, which
receives no further attention; but a few, such as the big digger wasp
(Bembex) take food to the grubs daily. Another class of both wasps and
bees form nests of several cells containing eggs, and thus in spring
families are originated by fertilized females that have survived the
winter. As the larvæ develop in succession they are fed by the mother,
and presently mature sufficiently to aid her in caring for the younger
grubs. Out of such family nests, or "combs" of paper cells, often
attached to the ceilings of sheds and porches of rural houses, have
apparently developed the mutually helpful societies of bees and ants,
which are often of surprising extent and permanency.
The prosperity of these social insect communities, whose instincts,
habits, and products amaze us, is due to an organized division of
labor in the community between three classes of "citizens"--(1) the
comparatively few males, whose whole duty is to fertilize the queen
mother and supply the community with progeny; (2) the selected and
specially nourished "queen"; (3) a vast number of nonreproductive
females, the "workers," that build and guard the nest, gather and
preserve stores of food (honey), and nurse and rear the young. In
some groups the duties of the workers are subdivided among classes
that differ in size and equipment. It is these female workers, or
their correlatives among the solitary bees and wasps, that sting,
their useless ovipositors having been transformed by the addition of
poison into deadly weapons by which they procure their prey, or defend
themselves, or both. It is this division of labor, and attendant
habits, that especially characterize the higher Hymenoptera, and give
to the order the supreme rank it occupies among insects.