James Wilson, age 11, of Milwaukee, Wis., for his question:
How do pupae, cocoons and chrysalises differ?
Certain insects go through a pupa, or sleeping beauty stage, during which they change from grubby caterpillars into glamorous adults. Mother Nature provides each little insect with a suitable resting place while this amazing change is going on. He must be kept warm and quiet and he must be as inconspicuous as possible. Some insects spend the pupa stage in a tough, leathery crysalis, others are wrapped in a cocoon ‑ a soft blanket of silk. Both the crysalia and the cocoons are going through the insect's pupa stage of development.
Not all insects go through a pupa stage. Some, like the grasshopper, hatch from eggs into miniature copies of their parents. These midgets are called nymphs and they grow by molting, by shedding their skins for larger skins, Several molts are necessary before the nymphs are fully grown. As a rule, wings appear after the last molt.
The pupa insects go through four different and distinct life changes. They begin as eggs which hatch into grubby worms or caterpillars. They are then in the larva stage of insect life. All caterpillars are larvae, very different in appearance from their adult parents. In a matter of days or weeks, the larvae eat their fill and go to sleep. The pupa stage begins.
The caterpillar of the silkworm moth spins itself a soft cocoon from a thread of silk a quarter mile long. The fuzzy, woolly bear caterpillar, black with a red waist band, is the larva of the small yellow isabella moth. This cozy caterpillar spends the winter in his larva stage, feeding on pointed plantain leaves. Come spring, he winds himself in a fuzzy cocoon and becomes a pupa while he changes into a moth 1ike his mother.
Most, but not all moths pupate in silken cocoons. The wide‑winged sphynx moth pupates as a hard‑coated purple chrysalis. There are a hundred or so different sphynx moths and in their larva stages they are among the biggest pests known to man, The tomato worm, the potato worm and the tobacco worm are caterpillars of various sphinx moths. When they have eaten their fill of our vegetables and salads they drop to the ground and spend their pupa stage in the ground as hard chrysalis.
The butterflies all spend the pupa stage wrapped in sturdy chrysalises. The tiger striped monarch caterpillar feeds on milkweed and spends his pupa stage in a chrysalis of milkweed green. The mourning cloak pupa is like a crisp brown burr, hanging from the brown twig of a n elm, the tree on whose leaves it fed as a caterpillar. Angle wing butterflies form brown, shell‑like chrysalises which hang unnoticed from trailing hop vines. The cabbage butterfly has a chrysalis which is as green as a cabbage leaf. Growing ants go through the pupa stage in silken cocoons. Mosquitoes pupate as chrysalises which float near the surface of a pond.