Aposematic Caterpillars: Life-Styles of the Warningly Colored and Unpalatable

Caterpillars have an impressive array of defenses to avoid being eaten. For example, they may blend in extremely well with their background (Cott 1940; Edmunds 1974, 1990), they may mimic potential predators of their own predators (Nentwig 1985; Pough 1988), they may construct shelters (Fitzgerald 1980; Fitzgerald and Willer 1983; Damman 1987), and they may be unpalatable due to urticating hairs (Kawamoto and Kumada 1984), defensive glands such as osmete­ ria (Honda 1983; Damman 1986), or chemicals sequestered from their host plants (Duffey 1980; Blum 1983; Bowers 1990). Insects that are unpalatable are particularly interesting in that they not only use their bad taste or unpleasant odor as a defense, but they usually also advertise this defense to would-be predators by attributes such as conspicuous coloration, gregariousness, and sedentary be­ havior. Possession of unpalatable qualities coupled with advertisement of those quali­ ties has many consequences for the life history features, population biology, physiology, and foraging behavior of aposematic caterpillars. For example, apo­ sematic caterpillars need not hide from most potential predators and so, on a basis, may be able to spend more time feeding than cryptic caterpillars that must behave in ways that reduce their susceptibility to predators. Sequestration of defense compounds from larval host plants may require particular physiological adaptations by larvae to ingest, accumulate, and store those compounds (Brattsten 1986; Bowers 1992). In addition, unpalatable caterpillar species may be mimicked palatable caterpillar species, and the presence of varying proportions of palat­ able look-alikes could affect the efficacy of aposematism, and the population dynamics of both model and mimic. Conspicuously colored, unpalatable insects have been referred to as warningly