Distasteful properties

Although the larvae of many ithomiine butterflies feed on solanaceous plants and must be adapted to the presence of steroid alkaloids, the distasteful properties of adults are... 

Predators ignore sea hares because, like other mollusks without shells, they have chemicals that afford them the protection once given by a shell. (We saw earlier that a compound from a tropical sea hare is now a promising anticancer drug.) Many sea hares have an acrid or fetid odor that is distinctly unpleasant to humans. Their egg masses and their skin must be distasteful, because one exploratory bite is enough to convince a would-be assailant to look elsewhere for food. For some species, the deterrents responsible for these properties may come directly from their seaweed diet, but other species seem to synthesize these defenses for themselves. The evidence is mixed and confusing. 

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