FOODPLANT EFFECTS ON COLOR MORPHS OF EUMORPHA-FASCIATA CATERPILLARS (LEPIDOPTERA, SPHINGIDAE)

Caterpillars of the hawkmoth Eumorpha fasciata are highly polymorphic for colour, with green, pink, and pink-and-yellow forms in the second through fourth instars, and green and multicoloured forms in the fifth instar. Four years of field censuses on four foodplant species determ ined that all morphs were found on all plant species; morph frequencie s were homogeneous on each plant species over time; and morph frequenc ies differed consistently among plant species. When larvae were reared from eggs on three of the hostplant species in the laboratory, differ ences in morph frequencies paralleled the census results. Thus foodpla nt quality is one factor affecting larval colour in E. fasciata. A lit erature survey reveals that foodplant effects on larval colouration ma y be widespread in the family Sphingidae, but most reports are anecdot al rather than experimental. The implications of this mechanism of col our determination are discussed.