Functional, evolutionary and ecological aspects of feeding-related mouthpart specializations in parasitoid flies

This paper considers mouthpart specializations for feeding among dipteran parasitoids, and places them in both an evolutionary and an ecological context. Parasitoid flies display specializations in relation to feeding on solidified honeydew, removing floral nectar from long, narrow, tubular corollas, and feeding on host materials. No species have as yet been identified which display particular specializations for pollen-feeding, but we consider it likely that they exist. Marked sexual dimorphism in mouthpart structure appears to occur only in the Phoridae. Mapping the occurrence of apparatus for removing floral nectar from long, narrow, tubular corollas ('concealed nectar extraction apparatus' or CNEA) onto published cladograms for Diptera shows that the evolution of such feeding apparatus has occurred many times independently. In contrast to parasitoid Hymenoptera, possession of CNEA is more often an autapomorphy for taxa above subfamily level in apparently two cases for superfamilies (Acroceroidea and Nemestrinoidea). We conclude that whereas in parasitoid wasps the pattern of occurrence of CNEA is mainly attributable to ecological expediency, in parasitoid flies phylogenetic history has also played a major role. We discuss the fitness advantages of the different feeding specializations among parasitoids generally (i.e. both Diptera and Hymenoptera) in relation to various ecophysiological factors. (C) 1998 The Linnean Society of London.