Zoölogy: The Science of Animal Life / Popular Science Library, Volume XII (of 16), P. F. Collier & Son Company, 1922

Another group, the Diploda, are known as galley worms, or millipedes, and have two pairs of bristlelike legs on each segment. Here the body is as round as that of an earthworm, and is incased in a hard, chitinous shell, usually red-brown in color; and when disturbed they coil up and emit an acrid, unpleasant odor as a defense.

WEAVERS OF SILKEN TRAPS

The class Arachnida, which contains the scorpions, spiders, mites and their allies, connects the Crustacea with the Insects; and some naturalists include within it the eurypterids and king crabs, classified in this book with the Crustacea. All live on land and breathe air except a small group of allies (Pycnogonida) which are marine, and may be found on the rocks, and clinging to wharf piles, etc., on our coasts as well as elsewhere; they appear to be all legs, and are known to New England fishermen as "no-body crabs." The class includes seven orders, the lowest in rank of which is that of the scorpions (Scorpionida).

Scorpions are inhabitants of warm countries, and some tropical American species are six inches in length, but those of our Southern States are smaller. They have slender bodies consisting of a cephalothorax and a long abdomen ending in a sharp sting through which two poison glands inject poison into the wound made by it, the effect of which may be very severe on a man, and is fatal to the insects and other small creatures on which scorpions prey; this "tail" with the sting is usually carried curled up over the back. The body is protected by chitinous plates above and below. The legs are four. From the head spring two great, crablike, pincer claws. When these seize an insect they hand it back to two small but powerful appendages at their base which act as jaws. Between them is a small mouth. Scorpions are nocturnal in habit, hiding by day in crevices, and wandering about at night; thus they are likely to seek such dark retreats toward morning as a person's boots; and in hot, dry regions travelers must be cautious about examining their clothing and baggage to avoid being stung. The scorpions retain their eggs until hatched. The young when born differ little except in size from their parents, and are cared for with much solicitude by the mother, who carries them around with her for some time, hanging by their pincers to her body. The race is ancient, fossil remains occurring as early, at least, as the Carboniferous age.

The second order, Pseudoscorpionida, includes the "book scorpions," a series of minute, stingless, scorpion-shaped creatures found in moss, under the bark of trees, or more often on flies. A third order, Pedipalpida, is that of the scorpion spiders, or "whip scorpions" of the tropics; the fourth, Solpugida, contains certain ugly creatures intermediate between scorpions and spiders; and the fifth order, Phalangida, is that of the small-bodied, vastly long-legged things called "harvestmen" in England and daddy longlegs by us, which run about in the summer heat, and feed on minute insects. They abound in all the warmer parts of the world, and in great variety, South America showing some very bizarre forms. This brings us to the sixth order, Araneida—the spiders.

THE SPIDERS AND THEIR WEBS

Spiders are usually thought and spoken of as "insects" by the layman. Many persons call almost every creature an insect that is small and supposed to be useless, or suspected of harmfulness. But spiders are different from insects properly so called in many important particulars of structure and habits. Spiders have four pairs of legs, while insects have six legs. The spherical abdomen, which is cut off from the head by a deep constriction, shows no segmentation, and on its floor are large glands (the arachnidium) producing the silk which is exuded from three pairs of tubes with sievelike openings, at the end of the abdomen, called the spinnerets. Their nervous system is highly developed, and they show much intelligence. Spiders are of two sexes, but the male is usually much smaller than his mate.

When egg-laying time comes the female forms a little silken bed attached to grass, or underneath a stone, or stuck to some object, or placed in a burrow, or hung like a hammock by long guy lines, and deposits in it eggs like drops of jelly. One sort places this under water, forming a nest like an inverted cup and filling it with bubbles of air, and spending much of its time in this real diving bell. A common garden spider (Lycosa) forms globular cocoons, and drags them around attached to the spinnerets, regardless of jars and bumps. In a large section of the tribe this is all the use that is made of the silk, which differs from that of insects (caterpillars) in being made up of a great number of finer threads laid together while soft enough to unite into one.

It is a common habit with spiders to draw out a thread behind them as they walk, and in this way they make the great quantities of threads that sometimes cover a field of grass. This is the gossamer often so annoying to us in late summer, but a thing of beauty when glistening with dew.

The gossamer of autumn, however, is made by the very small spiders of the genus Erigones, which hide in the herbage, but in the fine weather that comes after the first frosts climb to the tops of posts, fences and tall weeds, in company with the young of larger kinds, and "turning their spinnerets upward allow threads to be drawn out by ascending currents of air, until sometimes the spiders are lifted off their feet and carried long distances." These are the "ballooning spiders" of which one hears. In this way the whole country is overspread with lines and tangles of trailing silken threads that whiten our clothes and stick to our faces.

Three or four hundred species of spiders might be obtained in almost any locality in this country by diligent search, and thousands of foreign species are known; hence only a few conspicuous examples may be mentioned here. The tribe may be divided according to habits into two groups of families: 1. The hunting spiders, which run on the ground or on plants, catching insects by chase or by strategy; and 2. The cobweb spiders, which make webs to catch insects, and live all the time in the web or in a nest near it.

In the former group are the Drassidæ, a family of small, varicolored spiders that run about on the ground or in bushes, one large genus of which (Clubiana) includes pale, or purely white species; their cocoons are baglike or tubular. The most conspicuous genus is Misumena, in which the species are white or brightly colored, and which spend their days among flowers, waiting in rigid attitude for an insect to alight near them on which they may pounce. Spiders can see well for four or five inches, but not much beyond that. The Attidæ are small, hairy, or scaly jumping spiders, often brightly colored, that are found in open places and on the tops of low plants, whence they leap on their prey, or make long jumps to escape danger. To the next family, Lycosidæ, belong the large spiders most often seen in fields and pastures. They are fond of dry, sandy places, where the females live in silk-lined holes. These lycosids are long-legged, rapid runners, and capture their game by running it down. To this family belongs the famous tarantula of southern Europe, fabled to produce a madness (tarantism) in a person bitten that could be cured only by dancing to music of a certain lively measure called "tarantella." (The so-called "tarantula" of our southwestern desert region, is, however, another species.) A common northern spider (Lycosa carolinensis) is its equal in size, (the longest legs covering a spread of three inches), and in color, black with gray legs. Still larger is another North American lycosid (Dolomedes tenebrosus), gray with spiny legs ringed with dark and light gray, which spreads four inches.

These big ugly creatures, and the bites of spiders generally, are regarded with unnecessary dread by most persons. The jaws (mandibles) are close together at the front of the head. They are two-jointed, the basal joint stout, and the end joint or claw slender and sharp-pointed. The claw has near its point a small hole, which is the outlet of the poison gland. "The poison kills or disables the insects which are captured by the spider. Its effect on the human skin varies in different persons. Sometimes it has no effect at all; oftener it causes some soreness and itching ... and cases have been known in which it caused serious inflammation which lasted a long time. Spiders seldom bite and only in self-defense, the bites so commonly charged to them being often the work of other animals."

In the family Agalenidæ we meet with the first of the web makers. These are spiders of moderate size, characterized by a big head marked off from the thorax by converging grooves. Their natural home is in the grass, where their flat, closely woven sheets of silk, almost invisible by reason of their transparency, but brought into plain view when coated with dew or dust, are spread everywhere. They also are fond of getting into cellars and old buildings, and constructing webs across corners, bracketwise. Somewhere the web sinks like a narrow funnel into a short tube in which the owner hides, watching hungrily until a fly alights on his silken platform.

"The Therididæ," says Emerton, "are the builders of the loose and apparently irregular webs in the upper corners of rooms, in fences and among rocks, and between the leaves and branches of low trees and bushes. They are generally small, soft and light-colored spiders, with the abdomen large and round and the legs slender and usually without spines.... Most of the Therididæ live always in their webs, hanging by their feet, back downward. The webs have in some part a more closely woven space under which the spider stands." These spiders are quick to avail themselves of any chance to spin their shapeless meshes of almost invisible silk, which few regard as real "webs," in closets, cellars, and all over the house or barn. Many of them are adorned with gay colors or striking patterns, and some are much feared, especially Latrodectus mactans, about half an inch long, which is black with scarlet spots. It is common from Canada to Chile, and everywhere is considered fatally poisonous—why, it is difficult to say.

Last of our list, and highest in rank, are the Epeiridæ, the "orb weavers," as they are often called, who make those regular spiral nets which are in our mind's eye when we think of cobwebs. Most of the moderately large and handsome house and garden spiders are of this family, and everyone can easily examine their work, although it is less easy to watch them at it, as the webs are built and repaired at night. Among the obscurer and foreign species the abdomen often shows humps, points and long forward-reaching horns that make them exceedingly grotesque, and doubtless difficult to handle by birds and other creatures that seize them as food.

One of the round webs of the Epeiridæ consists of several radiating lines, varying in different species from a dozen to seventy, crossed by two spirals—an inner spiral that begins in the center and winds outward, and an outer spiral that begins at the edge of the web and winds inward. The inner spiral is made of smooth thread, like that of the rays, to which dust will not cling; the outer spiral is made of more elastic thread which, when fresh, is covered with fine drops of sticky liquid.

"In beginning a web, after the radiating threads are finished, the spider fastens them more firmly at the center and corrects the distances between them by [inserting] several short, irregular threads, and then begins the inner spiral, with the turns at first close together and then widening
... until they are as far apart as the spider can
reach with the spinnerets [resting] on one and the front feet on the next, and so goes on nearly to the outside of the web, where it stops abruptly. The spider usually rests a moment, and then begins, sometimes at another part of the web, the outer sticky spiral.... As soon as the inner spiral is found in the way a part of it is cut out, and by the time the outer spiral is finished the inner is reduced to the small and close portion near the center.... The whole making of the web seems to be done entirely by feeling, and is done as well in the dark as in daylight. When the spider is active and the food supply good, a fresh web is made every day, the old one being torn down and thrown away."

As a rule these orb weavers do not stay in the web in the daytime, but hide away in their nests made in some near-by but concealed place; and their egg cocoons are hidden in all sorts of places.

All of the spiders that have been considered so far belong to the division of the class that has but a single pair of lungs. A second division has been made for those having two pairs of lungs, composed of a single family, the Mygalidæ, consisting of the so-called "bird-catching" spiders and the trapdoor spiders. The great mygale of Guiana has a body sometimes two inches long, and its legs will span eight or nine inches of space. It is hairy all over, intensely black, and a terror to all small creatures, even catching small birds, according to tradition; but proof of this is wanting.

The trapdoor spiders are those of the genera Cteniza and Atypus which dig and inhabit vertical holes in the soil, lined with silk and closed at the top by a hinged stopper or "trapdoor." Several species occur in southern Europe, one of which has a second door hanging by a silken hinge half way down the shaft; and in case of trouble the spider goes below it and pushes it above its head, so that the intruder is deceived into thinking it has opened an empty nest. Cteniza californica is the common species of our Southwest. The cover of the hole is made of dirt fastened together with threads, and is lined, like the tube, with silk, and fastened by a thick hinge of silk. The spider holds the door shut from inside. These underground homes are safe retreats for the spiders during the day, and nesting places in which their eggs are deposited and young reared; at night the spiders go forth in search of prey.

MITES AND TICKS

Mites and ticks are classified with the spiders as degenerate relatives of arachnoid stock. Ticks are large enough to be seen without a magnifying glass, and some become half an inch long. Ticks are wholly parasitic. The female lays several thousand eggs at one time on the ground or just beneath the surface. "The young 'seed ticks' that hatch from these in a few days soon crawl up on some near-by blade of grass, or on a bush or shrub, and wait quietly until some animal comes along. If the animal comes close enough they leave the grass or other support and cling to their new-found host." These parasites are the agents of the spread of several infectious diseases of cattle, the worst of which is the destructive Texas fever, and of mankind, as spotted fever and other ills resulting from the presence of blood parasites.

CHAPTER XI
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.

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.

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.

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.

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.

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.