Anna B. Comstock

The Promethea

Teacher's Story

HE promethea is not so large as the cecropia, although the female resembles the latter somewhat. It is the most common of all our giant silk-worms. Its caterpillars feed upon wild cherry, lilac, ash, sassafras, buttonwood and many other forest trees.

During the winter, leaves may often be seen hanging straight down from the branches of wild cherry, lilac and ash. If these leaves are examined, they will be found to be wrapped around a silken case containing the pupa of the promethea. It is certainly a canny insect which hides itself during the winter in so good a disguise, that only the very wisest of birds ever suspect its presence. When the promethea caterpillar begins to spin, it selects a leaf and covers the upper side with silk, then it covers the petiole with silk, fastening it with a strong band to the twig, so that not even most violent winter winds will be able to tear it off. Then it draws the two edges of the leaf about itself like a cloak as far as it will reach, and inside this folded leaf it makes its cocoon, which always has an opening in the shape of a conical valve at the upper end, through which the moth may emerge in the spring. This caterpillar knows more botany than some people do, for it makes no mistake in distinguishing a compound leaf from a simple one. When it uses a leaflet of hickory for its cocoon, it fastens the leaflet to the mid stem of the leaf and then fastens the stem to the twig. The male pupa is much more slender than that of the female. The moths do not issue until May or June.

Promethea cocoons.  Note how the leaves are fastened by silk to the twigs. Photo by M. V. Slingerland.

The moth works its way out through the valve at the top of the cocoon. The female is a large, reddish brown moth with markings resembling somewhat those of the cecropia. The male is very different in appearance; its front wings have very graceful, prolonged tips, and both wings are almost black, bordered with ash color. The promethea moths differ somewhat in habit from the other silk-worms, in that they fly during the late afternoon as well as at night. The eggs are whitish with brown stain, and are laid in rows, a good many on the same leaf.

Promethea caterpillars.  Photo by M. V. Slingerland.

The caterpillars, as they hatch from the eggs, have bodies ringed with black and yellow. They are sociable little fellows and live together side by side amicably, not exactly "toeing the mark" like a spelling class, but all heads in a row at the edge of the leaf where each is eating as fast as possible. When they are small, the caterpillars remain on the under side of the leaves out of sight. In about five days, the first skin is shed and the color of the caterpillar remains about the same. Four or five days later, the second molt occurs, and then the caterpillar appears in a beautiful bluish green costume, with black tubercles, except four large ones on the second and third segments, and one large one on the eleventh segment, which are yellow. This caterpillar has an interesting habit of weaving a carpet of silk on which to change its skin; it seems to be better able to hold on while pushing off the old skin, if it has the silken rug to cling to. After the third molt, the color is a deeper greenish blue and the black tubercles are smaller, and the five big ones are larger and bright orange in color. After the fourth molt, which occurs after a period of about five or six days, the caterpillar appears in its last stage. It is now over two inches long, quite smooth and most prosperous looking. Its color is a beautiful, light, greenish blue, and its head is yellow. It has six rows of short, round, black tubercles. The four large tubercles at the front end of the body are red, and the large tubercle on the rear end of the body is yellow.

The male promethea.  Photo by M. V. Slingerland.

The cynthia is a beautiful moth which has come to us from Asia; it is very large with a ground color of olive-green, with lavender tints and white markings; there are white tufts of hairs on the abdomen. It builds its cocoon like the promethea, fastening the petiole to the twig, therefore the lesson indicated for the promethea will serve as well for the cynthia. The cynthia caterpillars live upon the ailanthus tree and are found only in the regions where this tree has been introduced.

The female promethea.  Photo by M. V. Slingerland.

References—Moths and Butterflies, Dickerson; Caterpillars and Their Moths, Elliot and Soule; Moths and Butterflies, Ballard.

Method—This work should begin in the late fall, when the children bring in these cocoons which they find dangling on the lilac bushes or wild cherry trees. Much attention should be paid to the way the leaf is fastened to the twig so it will not fall. The cocoons should be kept out of doors, so that the moths will issue late in the spring when they can have natural conditions for laying their eggs, and the young caterpillars are supplied with plenty of food consisting of new and tender leaves.

2. How is the leaf fastened to the twig? Could you pull it off readily? What fastened the leaf to the twig?

3. Tear off the leaf and study the cocoon. Is there an opening to it? At which end? What is this for?

4. Cut open a cocoon. Is it as thick as that of the cecropia?

5. Study the pupa. Is it as large as that of the cecropia?

6. Can you see where the antennæ of the moth are? Can you see the wing covers? Can the pupa move?

3. Make water-color drawings of promethea moths, male and female.

4. If a promethea mother lays eggs, describe them.

2. How do they change color as they grow older? Do they remain together or scatter? Do they continue to hide on the lower sides of leaves?

3. What preparation does a promethea caterpillar make before changing its skin? Why does it shed its skin? Do its colors change with every change of skin?

4. Describe the caterpillar when it is full-grown. What is its ground color? What are the colors of its ornamental tubercles? The color of its head?

5. Describe how a promethea caterpillar makes its cocoon.