rope, and now common in certain parts of New England. Its wings are yellow, with two blackish spots on the forward wing, and one on the hinder wing. The chrysalides of this species are very common on fences, and, when collected in the fall, may be kept through the winter. During February and March the butterflies will come out, and these may be fed on honey or sugar mixed with water, and in this way may be kept alive for some time.

75. The caterpillar, then, having changed into the chrysalis, remains in this condition a few weeks, or even many months, and then the skin slowly cracks open, and out crawls a creature no longer like a caterpillar, but having three pairs of long, jointed legs, the body divided into three very distinct regions—the head, thorax, and abdomen-the thorax having wings, and the head furnished with long antennæ, and provided with mouth-parts suitable for sipping nectar, and no longer like the heavy jaws of the caterpillar, suited only to chewing coarse leaves; in short, a creature resembling the insect which first laid the eggs from which the caterpillar

came.

76. Other names are given to these three stages of an insect. The worm, or caterpillar, is called the larva; the chrysalis is called the pupa; while the perfect insect is called the imago. These terms are necessary, for without them the proper condition of an insect could not be easily described.

Take, for example, the caterpillar stage of a butterfly: the same stage in a common fly is known by the name of

maggot, and in other insects the same conditions are known by the name of borer, grub-worm, and many other terms. If the pupil learns that all these various names describe a similar stage in the lives of these insects, it is much more convenient to have some general term describing all these stages, such as larva, or larval stage.

77. While most insects pass through changes similar to those above described, there are others, such as the grasshoppers, crickets, roaches, and bugs proper (a group of insects which includes the squash-bug, chinch-bug, and bedbug, all of which have a disagreeable taste and odor, and to which naturalists restrict the name of bug), which do not pass through a caterpillar and chrysalis state. The young hatch from the egg, and closely resemble the adult insect,

a

f

FIG. 31.-DIFFERENT STAGES OF THE CHINCH-BUG: a, Egg; b, Newly-hatched Larva; c, Larva after First Moult; d, Larva after Second Moult; e, Pupa; f, Perfect Insect. [These figures are copied from the Seventh Annual Report of C. V. RILEY, State Entomologist of Missouri.]

except that it has no wings, and is of course much smaller than the parent. In its growth it moults or sheds its skin, and each moult reveals its wings more advanced in growth,

G

till finally, on the last moult, it attains the size and features of the mature insect. And even in this growth, so unlike the moth and butterfly, the terms larva and pupa are applied to certain stages of its history.

The foregoing figure represents the egg and successive stages of the chinch-bug, an insect which has been so destructive to various crops in the West. The figures are all enlarged; the little line at the lower left-hand side of each figure represents the natural size.

78. Many insects, as the beetles, flies, moths, butterflies, bees, and wasps, pass through complete and distinct changes from their early condition to maturity, as above described. Other insects, as the grasshoppers, crickets, roaches, and bugs, hatch out from the egg, as little six-footed insects, and not as worms, and in their growth do not pass through an inactive pupa or chrysalis stage, but slowly acquire wings, and ultimately attain full growth as above stated. Hence these changes are not so completely defined as the changes in the insects first mentioned. For this reason the term complete metamorphosis is used to define the mode of growth of the beetles, flies, and other insects having a similar mode of growth; while the term incomplete metamorphosis defines the mode of growth of the grasshoppers, crickets, and others.

79. Many of the larvæ of insects look like worms—so much so, indeed, that they are commonly called worms, such as cut-worms, canker-worms, currant-worms, and the like. The pupils have learned that these are not true worms, but only the larval condition of certain insects.

True worms, however, never change into any thing else. Such, for example, is the earthworm, hair-worm, and leech, and worms which live in the sea.

FIG. 82.-EARTHWORM.

FIG. 83.-MARINE WORM.

These worms, and other true worms, generally speaking, have the body divided into a great many segments or rings, as in the earthworm. In the larvæ of insects, on the contrary, the segments are limited in number. With few exceptions the larvæ of insects have legs, and these legs in the fore-part of the body are jointed. In worms, jointed legs do not occur. The jointed legs of the larvæ number three pairs, and are on the three successive rings back of the head, and consequently correspond to the three pairs of legs in the adult insect.

In certain larvæ other legs occur, but these are not jointed, though often having special structures at their extremities,

by which they are enabled to cling. These are called prolegs, or false legs.

It would be well for the pupils to collect some leeches and earthworms, and, if they live near the sea-shore, a few worms may be collected under stones at low tide.

Having collected these, let the pupils compare them with the larvæ of insects.

As the larva of an insect comes from the egg, it has its full number of segments at the outset. In the larva of a butterfly, for example, there may be counted, besides the head, twelve segments or rings, and this number does not increase as the creature grows, but remains constant; and, as we have already learned, the creature does not long remain in its worm-like stage, but assumes other conditions, ultimately becoming a creature unlike, in form and habits, the larval condition in which it spent a portion of its life.

80. The true worm, on the contrary, comes from the egg with a very limited number of segments, and as it grows new segments are formed, till in some worms as many as four or five hundred segments are developed before the animal has attained mature proportions, and in this condition it remains; that is, it is complete, never changing or passing through larval or pupal stages to develop into something quite unlike the worm.

Briefly, then, a larva may be distinguished from a true worm generally by its limited number of segments, and, when supplied with legs, having three pairs of jointed ones on the anterior rings of the body.