Cocoons are another never-ending source of delight. If you think that there are no unsolved problems of the commonest insect life around us, say why it is that the moths and millers pass the winter wrapped in swaddling clothes of densest textures, roll upon roll of silken coverlets; while our delicate butterflies hang uncovered, suspended only by a single loop of silk, exposed to the cold blast of every northern gale? Why do the caterpillars of our giant moths--the mythologically named Cecropia, Polyphemus, Luna, and Prometheus--show such individuality in the position which they choose for their temporary shrouds? Protection and concealment are the watchwords held to in each case, but how differently they are achieved! Cecropia--that beauty whose wings, fully six inches across, will flap gracefully through the summer twilight--weaves about himself a half oval mound, along some stem or tree-trunk, and becomes a mere excrescence--the veriest unedible thing a bird may spy. Polyphemus wraps miles of finest silk about his green worm-form (how, even though we watch him do it, we can only guess); weaving in all the surrounding leaves he can reach. This, of course, before the frosts come, but when the leaves at last shrivel, loosen, and their petioles break, it is merely a larger brown nut than usual that falls to the ground, the kernel of which will sprout next June and blossom into the big moth of delicate fawn tints, feathery horned, with those strange isinglass windows in his hind wings. Luna--the weird, beautiful moon-moth, whose pale green hues and long graceful streamers make us realise how much beauty we miss if we neglect the night life of summer--when clad in her temporary shroud of silk, sometimes falls to the ground, or again the cocoon remains in the tree or bush where it was spun. But Prometheus, the smallest of the quartet, has a way all his own. The elongated cocoon, looking like a silken finger, is woven about a leaf of sassafras. Even the long stem of the leaf is silk-girdled, and a strong band is looped about the twig to which the leaf is attached. Here, when all the leaves fall, he hangs, the plaything of every breeze, attracting the attention of all the hungry birds. But little does Prometheus care. Sparrows may hover about him and peck in vain; chickadees may clutch the dangling finger and pound with all their tiny might. Prometheus is "bound," indeed, and merely swings the faster, up and down, from side to side. It is interesting to note that when two Prometheus cocoons, fastened upon their twigs, were suspended in a large cageful of native birds, it took a healthy chickadee just three days of hard pounding and unravelling to force a way through the silken envelopes to the chrysalids within. Such long continued and persistent labour for so comparatively small a morsel of food would not be profitable or even possible out-of-doors in winter. The bird would starve to death while forcing its way through the protecting silk.