The two silk-worm moths which we figure this month both possess a point of excellence far in advance of any other of our native silk-worm moths; Luna on account of its graceful form and delicate colors, and Polyphemus for the silk of its cocoons.

It seems that most persons who speak of the Luna moth (Tropaea luna) feel called upon to give a more or less poetic description of it. This, I hope, has been rendered unnecessary by the colored plate, so that it will suffice simply to mention that the beautiful shade of green is of very rare occurrence among our larger moths, and that no other has the long, graceful "tails" on the hind wings, a characteristic which adds greatly to the beauty of this insect.

This moth does not seem to be very abundant anywhere, but when once seen will long be remembered on account of its great beauty. The green and yellow colors are evidently very closely related, because either one may, to a greater or less degree, replace the other, so that some of the moths have quite a strong, yellowish tinge. One of our common swallow-tail butterflies (Iphiclides ajax) possesses a very similar green color in its wings, but does not seem to show this tendency to replace the green by yellow. On the wings are four eyes pots which are also found in Polyphemus. These are remarkable in that they are transparent in the center. This clear area in Luna is quite small, while in Polyphemus it is about as large as the entire eye spot of Luna. The legs are brown and colored like the front edge of the fore wings. The hairs on the body and at the base of the wing are very long and are white or yellow. The wing expanse ranges from three and three-fourths to five and one half inches.

During April or May the mother moth lays her dark-brown or chocolate-colored eggs upon hickory, walnut, beech, oak, and a few others of our forest trees. The limited number of food plants is doubtless one reason for the rarity of the moths, as compared with such a common and almost omnivorous larva as Cecropia. A single moth may lay about one hundred eggs, which are smaller than those of Polyphemus. These hatch in about ten or fifteen days, the larva making its escape by eating a circular hole in the shell. Occasionally a young larva may be seen crawling about for a short time, carrying upon its head or tail the empty shell.


The adult larva is about three inches long, of a delicate pate green, a color very difficult to preserve in the dead larva. Those on the plate have lost this delicate green and have become yellow, but show the form perfectly. This larva is very much like that of Polyphemus, but may be distinguished from it by possessing a longitudinal pale yellow lateral line, which is not found in Polyphemus. Since the cocoon is quite thin and contains but little silk, it is, considered of but little value. This cocoon is spun among two or three Waves, and is about two inches long. Some authors claim that the cocoon falls to the ground with the autumnal falling of the leaves; others that it transforms on the ground among the fallen leaves. The cocoon is quite similar to that of Polyphemus, but not so firmly attached when fixed to a stem. The moths emerge in April and May, there being only a single brood in the north, while there are two in the south.

The color of the cocoon seems to be influenced in some way by the kind of food eaten by the larva. Cocoons made by larva which have been fed on hickory leaves have a darker color. In the true silk worm moth this same influence has been noticed; larvae fed upon the vine producing red cocoons, on lettuce emerald green cocoons, while those fed upon white nettle produce yellow, green or violet cocoons. It is necessary in order to procure these results, that the larvae be fed upon the mulberry till about twenty days before the formation of the cocoon.

Polyphemus — The life history of this native silk worm (Telea polyphemus) is by far the best known, because many years ago it was very carefully studied with the hope that it would prove an important silk insect. This hope unfortunately has not been realized.

The moths, as shown by the plate, are really beautiful; the large eye spots on the hind wings contributing much towards this effect. The transparent, window-like centers in the eye spot are also of quite rare occurrence among our moths. These transparent areas do not possess the very minute scales found on the other parts of the wing. Almost all of the wonderful variety of colors found in the wings of butterflies and moths are due either to coloring matter in these scales, or to the breaking up of the white light by minute lines on these scales, such as are seen in the play, of colors on a soap-bubble. These fine lines on the scales are only on the upper side, and are about one-sixteen-thousandth of an inch apart.

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