attracted by lights, and have come to be called "electriclight bugs."

Among our most dreaded insect pests are the chinchbugs-small black-and-white insects, but traveling in companies aggregating many millions.

As they go they feed upon the stems and leaves of grain, which they devour with extraordinary rapidity. The squash-bug family is also extensive, and destructive to the young squash and pumpkin plants in the early spring.

The lice are small, curiously shaped bugs, which suck the blood of other animals. The plant-lice, also small, suck the juices of plants, and are often exceedingly destructive. This is especially true of the phylloxera, a plant-louse

FIG. 80.-Giant water-bug (Ser- which causes annually the loss of

millions of dollars among the vineyards of this and other countries. Even more destructive are the scale-insects, curiously modified forms, of which the wingless females may be found on almost any fruit-tree and on the plants in conservatories, their bodies covered with a downy, waxy, or other kind of covering, beneath which they remain and lay their eggs.

129. The flies (Diptera).-The group of the Diptera (meaning two-winged) includes the gnats, mosquitoes, fleas, house-flies, horse-flies (Fig. 81), and a vast company of related forms. Only a single pair of wings is present, the second pair being rudimentary or fashioned into short, thread-like appendages known as balancers, though they probably act as sensory organs and are not directly concerned with flight. The mouth-parts are adapted for piercing and sucking. The eyes, constructed on the same plan

as those of the Crustacea, are comparatively large, and are frequently composed of a great number of simple eyes united together, upward of four thousand forming the eye of the

common house-fly.

These insects are widely distributed throughout the world, where they inhabit woods, fields, or houses as best suits their needs. Their food is varied. Some suck the juices of plants, others attack animals, and, while many are troublesome pests, others, especially in the early stages of their existence, are of great benefit.

130. Typical forms.-Owing to the widely different habits and structure of the members of this group, we shall briefly consider two examples, the mosquito and the house-fly, which will give us a fairly good idea of the characteristics of all. The eggs of the mosquito are laid in sooty-looking masses on the surface of stagnant pools. Within a very short time the young hatch, and, owing to their peculiar swimming movements, are known as "wrigglers." They are then active scavengers, devouring vast quantities of noxious substances and performing a valued service. They frequently rise to the surface, take air into the tracheal system, which opens at the posterior end of the body, and descend again. After an increase in growth and many internal changes resulting in a chrysalis-like stage, they rise to the surface, split the shell, and, using the latter as a float, carefully balance themselves and soon fly away.

The house-fly usually lays its eggs in decaying vegetable matter, and the young, maggot-like in form, are active scavengers. They too undergo deep-seated changes during the next few days, finally transforming into the adult.

Many of this great group of the flies spend their early life in the water or other medium acting as scavengers; but, on the other hand, numbers attack domestic and other animals, and throughout their entire lives are an intolerable plague. 131. The beetles (Coleoptera).-Owing to the ease of preservation and their bright colors, the beetles have probably been more widely collected than other insects. Fully ten

thousand distinct species are known in North America alone. They are all readily recognized by the two firm, horny sheaths enclosing the two membranous wings, which alone are organs of flight. The mouth is provided with jaws, which are used in gnawing. Some prey on noxious insects or upon decaying vegetable or animal matter, and are often highly beneficial; but others attack our trees and domestic animals, and work incalculable damage.

In some of the stag- or wood-beetles (Fig. 82), which we may select as types, the adults are often found crawling about on or beneath the bark of trees, living on sap or small animals. The eggs laid in these situations develop into grub-like larvæ, which bore their way through living or dead wood, and in this condition sometimes live four or five years. They then transform into quiescent pupa (Fig. 82), which finally burst their shells and emerge in the adult form. Others, like water-beetles and the whirligigbeetles, whose mazy motions are often seen on the surface of quiet streams, pass the larval period in the water. Under somewhat different conditions we find the potatobugs, lady-bugs, fire-flies, and their innumerable relatives, but the changes they undergo in becoming adult are essentially the same as those described for the other members of the order.

132. The moths and butterflies (Lepidoptera).-The moths and butterflies occur all over the world. In their mature

FIG. 83.-Monarch-butterfly (Anosia plexippus). From photograph by A. L. MELANDER and C. T. BRUES.

state they are possessed of a grace of form and movement and a brilliancy of coloration that elicit our highest admiration. The mouth-parts are developed into a long proboscis, which may be unrolled and used to suck the nectar out of flowers, though in many of the adult moths, which never feed, it may remain unused. The wings, four in number, are covered with beautiful overlapping scales that

adhere to our fingers when handled. This feature, and the general plan of the body, which is much the same throughout the group, enables us to recognize most of them at once.

FIG. 84. The silver-spot (Argynnis cybele). Photograph by A. L. MELANDER and C. T. BRUES.

133. The ants, bees, wasps, etc. (Hymenoptera).-The ants, bees, and wasps are the best-known insects belonging to this order. They are characterized by four membranous wings, by biting and sucking mouth-parts, and the female is often provided with a sting. All undergo a complete metamorphosis. The eggs may be laid in the bodies of other insects, or they may be placed in marvelously constructed homes, and be the objects of the greatest attention, the parents or attendants often risking or losing their lives in their defense. The members of this order have long attracted attention, largely on account of their remarkable instinctive powers. They live in highly organized communities, and certain of their characteristics may be illustrated by a study of some of the more familiar forms.