They Might Be Giants
about a day after laying eggs. Males often mate again, but also die soon.
Seven to 14 days later, depending on air temperature, a battalion of tiny larvae, each one about the size of a mosquito, emerges. Many don't live to take their first bite of leaf; young larvae are food for birds, spiders and other insects. Those that survive soon develop well-defined heads and mouth parts for chewing. All Saturniids feed on the leaves of trees and shrubs. None of them bore into stems, stalks or fruits, and almost none feed on grasses, herbs or wildflowers. Most have poorly developed eyes and are almost blind.
Behind the head, the body has three segments that later form the adult-stage thorax. Each segment sports a small pair of legs-called true legs-used for mobility. The abdomen, just behind the thorax segments, holds several pair of fleshy legs, called prolegs. These usually are equipped with small suckerlike pads ringed with hooked claws-tools that help the caterpillar anchor itself to a leaf as it eats.
Although Saturniid larvae, like the fully grown adults, appear soft and squishy, they have a firm, external skeleton. Because this exoskeleton restricts growth, larvae must stop feeding and molt at regular intervals. Spinning a silken pad on a twig, a larva firmly anchors its legs to the pad and sits tight for about two days. The old "skin" splits apart, and the "new" larva pulls itself out, shaking its head side to side to free itself from the old head capsule. A Saturniid larva usually molts four to six times before it is mature enough to molt to a pupa and spin a cocoon.
Saturniid larvae are diverse in shape and color and each species is different. They may be green, clear, smooth or fuzzy. The Io moth larva, native to Missouri's hardwood forests, grows to 2 inches long and is covered with branched, green spines with black tips. If you handle one, you'll likely feel a painful sting. They don't have stingers, but their "hairs" break and dispatch a mild toxin.
Other Saturniid larvae depend on camouflage for survival and mimic the seed pods of their host tree or shrub. Still others have no camouflage at all and rely, instead, on simply tasting bad. They eat leaves from their host plants that make them gustatorily unappealing to predators.
Eventually the larvae molt to the pupal stage-a dormant stage between larvae and adulthood. Almost all