Caterpillars

Frederick W. Stehr

Michigan State University

The larvae of butterflies, skippers, and moths of the order Lepidoptera are generally known as caterpillars. Caterpillars

FIGURE 1 Caterpillar of the polyphemus moth, Antheraea polyphemus, showing the five pairs of prolegs bearing crochets (hooks). (Photograph by Joseph L. Spencer, Illinois Natural History Survey.)

come in a diversity of sizes, shapes, and colors. The most common form has a conspicuous head, a thorax with three pairs of legs, and an abdomen with five pairs of prolegs that bear crochets (hooks) (Fig. 1) that enable the caterpillar to cling tightly to or wedge itself between materials. In fact, some of the giant silk moth caterpillars (Saturniidae) can cling so tightly to a twig that a proleg can be ripped from the body if they are pulled too hard. A few other orders of insects contain larvae that are caterpillar-like, but only the larvae of the leaf-feeding sawflies (Hymenoptera) are commonly encountered. They are easily mistaken for caterpillars, but they usually feed in groups (as do some caterpillars), rear up when disturbed, have more than five pairs of prolegs on the abdomen, and never have crochets on the prolegs.

FIGURE 2 Twig-mimic inchworm caterpillar of a moth (Geometridae). (Photograph by Fred Stehr, Department of Entomology, Michigan State University.)
FIGURE 3 "Bird dropping" mimicry by the caterpillar of the orangedog, Papilio cresphontes. (Photograph by J. Mark Scriber, Department of Entomology, Michigan State University.)
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