SATURNIID AND SPHlNGID CATERPILLARS: TWO WAYS TO EAT LEAVES

Abstract

We demonstrated allometric differences in re lative head mass in different instars of 12 species of Satumiidae and 14 species of Sphingidae. The differences were related to the different ways in which individuals from the two fami lies ate their respective host plants and to the different properties of the hosts that tcnded to be favored by each lepidopteran family, The salurniids tcnded to have various simple cUlling methods, while the sphingids tore and crushed the food, so that in the former, ingested food was in the form of relatively large uniformly sized pieces, and in the latter it was apparently well masticated. Satumiid mandibles were short and simple, while sphingid mandibles were long, toothed, and ridged in a variety of complex ways. The food ofsaturniids tended to consist of old, tough, tanninrich leaves, while that ofsphingids was softer, younger, and contained small toxic molecules. The generalists within each group tended to be similar to one another, while the specialists (which occurred more frequcntly among the sphingids) had very characteristic mandibles, each of unique design. One sphingid species feeding on a vine with characteristically very tough leaves had the "satumiid" design of mandibles. The features typical of the two groups of caterpillar are discusscd in relation to feeding strategy, digestion, avoidance of plant " defenses," and rapidity of ingestion.