FIG. 7.

Scales from

the unaided eye this colored substance from the wing appears to have no definite form; in fact, it looks like the pollen from flowers. An examination with the compound microscope, however, shows that each of these tiny bodies has a definite shape (Fig. 7). Each scale has at one end a tiny stem, but in other respects they vary considerably in form. The scales are attached in the following manner. In the membrane of the wing are openings into which fit the stems of the scales. The latter are arranged in rows and overlap something like the shingles on a roof (Fig. 8). In spite of this arrangement it is evident that the scales are not firmly attached, since the slightest touch is sufficient to dislodge many of them. Rough handling was not apparently planned for in the construction of these insects. The presence of these scales on the wings of butterflies and of their near relatives, the moths, is so characteristic that these insects have been called the Lepidoptera (Greek, lépido scale + ptéra = wings). Not only are scales found on the wings but, in the shape

wing of a butterfly.

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of hairs, they form a fuzzy growth FIG. 8. Piece of the over the surface of the whole body.

9. Proboscis. Another marked characteristic of butterflies and moths is the sucking tube, or proboscis. While the proboscis seems to be a single structure, in reality it is composed of two slender appendages, each having a groove on

its inner surface; so that, when the two parts are brought together, they form a tube through which the butterfly sucks nectar from flowers. When the

proboscis is not in use, the butterfly rolls it into a tight coil underneath the head (Fig. 9).

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10. Legs. The legs of a butterfly are not very strong, since they are relatively so long and slender. This is perhaps the reason why these insects seldom use them for walking. They are, however, very useful in clinging to flowers. The two curved claws on the tip of each foot show clearly the means by which the animals are able to hold on to the plants on which they usually alight.

11. Reproduction and life history of butterflies. — As in the reproduction of plants, the development of the butterfly begins with a special cell known as an egg-cell. These eggcells are formed in the body of the female insect. When these egg-cells have been fertilized by sperm-cells from the male butterfly, which correspond to sperm-cells of the pollen grains (P. B., 91), the eggs are deposited on the under side of the leaves of plants on which the young can feed (Fig. 6). These egg-cells divide and subdivide, till at last a many-celled organism is developed that is commonly called a worm," but that is more correctly known as a caterpillar (Fig. 6).

The tiny caterpillar emerges from the covering of the egg and begins to feed upon the leaf. As it feeds it grows, and

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'P. B. "Elementary Plant Biology," by the authors of this book.

from time to time sheds or molts the more or less hardened skin that covers the whole insect. At last, after several molts, the caterpillar reaches its full size and then stops eating. At no time in the growth of the caterpillar would one be likely to mistake it for a butterfly (Fig. 6). It has no wings, no antennæ, and instead of a proboscis one finds a pair of strong jaws with which it eats leaves. The distinction between thorax and abdomen is not at all clear, and at first sight it seems to have more legs than a butterfly. The three front legs are really jointed, but they are so short and thick that there seems to be no resemblance between them and those of a butterfly. The other pairs of legs, varying in number, are not jointed structures, and hence are not really legs at all.

The mature caterpillar now attaches itself to some object and, after molting once more, usually assumes quite a different shape from that of the caterpillar, and forms about itself a hardened skin within which a marvellous transformation occurs (Fig. 6). The long, coiled tube takes the place of the jaws as a feeding organ, and long, slender, knobbed antennæ appear on the head; two pairs of beautifully colored wings develop on the thorax, as well as the three pairs of slender, jointed legs; and at last the fully developed butterfly breaks through the covering that held it and flies

away.

It is evident, then, that a butterfly passes through several fairly distinct stages. First we may distinguish the egg stage, then the caterpillar or larva stage, which is followed by the transformation stage in which it is called a pupa. The pupa of a butterfly is often called a chrysalis (Greek, chrýsos gold) on account of the golden spots of color on many pupa cases. Lastly we have the fully developed or adult insect that emerges from the pupa stage.

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12. Distinguishing characteristics of moths. The moths and butterflies belong to the same order of insects; that is, the scaly winged insects. But there are some characteristics in which these two kinds of insects differ. For instance, moths when at rest fold the wings horizontally (Fig. 11), while butterflies fold them vertically, that is, erect (Fig. 10). The wings, too, of moths are not usually as brilliantly colored. Most moths fly at night, while butterflies are day-flyers. The body of moths is usually relatively broader than that of butterflies. Moth antennæ are of various shapes, often like a feather, but never knobbed.

In general, the life history of moths is very much the same as that of butterflies, but the larvæ of many moths spin a more or less silky mass of threads about themselves, as is the case with the silkworm caterpillar (Fig. 16), and this outside covering of the pupa stage is known as the cocoon.

13. Economic importance of butterflies and moths. The larvæ of both butterflies and moths are voracious feeders, as any one knows who has had any experience with caterpillars. In fact, they may be called animated feeding machines, since the animal must not only provide for its own growth, but must also store up enough food to form the new parts such as the wings and the legs. Not all larvæ of butterflies and moths are considered harmful, however, since some of them are not prolific enough to have any serious effect upon vegetation, which is the source of food of most caterpillars. This is true of many of the butterfly larvæ and of some moth larvæ. Then, too, some of the larvæ feed on plants that are not useful to man. This is true of the larva of the monarch butterfly (Fig. 6), which feeds upon leaves of the milkweed. The adult butterflies and moths of course are not capable of doing any harm since, when they eat anything at all, they most commonly suck the nectar of flowers. When the flowers are visited in this way,

they are very likely to be cross-pollinated and thus are benefited instead of injured. But in general the moths and butterflies play but little part in the very important process of cross-pollination of flowers, most of this work being done, as we shall soon learn, by the bees. The following are a few of the injurious forms of butterfly and moth larvæ.

14. Cabbage butterfly.

- This is one of the few forms of butter

fly larvæ that are of sufficient economic importance to be worthy of

mention. Any one who has been near a cabbage patch will remember to have seen many rather small white butterflies (Fig. 10) hovering about among the cabbages. These are the cabbage butterflies depositing their eggs on the under side of the leaves. The small green caterpillars that develop from the eggs very soon show what they can do in the way of eating. The ragged appearance of the young leaves is a warning to the gardenerto "get busy" if he desires The caterpillars do most harm when the cabbages are young, since these plants may be so injured as to be unable to form heads. The caterpillars are often killed by sprinkling with a mixture of Paris green and arsenate of lead in water (47). This mixture should not be used, however, after the heads begin to form, on account of the possibility of the poison collecting between the leaves of the head, with consequent danger to the consumer.

FIG. 10.-Life history of cabbage butterfly. (Coleman.)

a crop.

15. Tussock moth.

The caterpillars of the tussock moth attack our shade trees. Where they are unchecked, they will practically