Selective predation on chemically defended chrysomelid larvae

Abstract

Laboratory experiments showed that femaleTenthredo olivacea prefer to prey upon insects of a previously encountered species, instead of upon unknown ones. This has been observed when comparing two natural prey of the sawfly, the larvae ofPhratora vitellinae and those ofPlagiodera versicolora. The two species secrete copious amounts of defensive secretion, the first salicylaldehyde, and the latter a mixture of cyclopentanic monoterpenes. The predator appears less reluctant when encountering a species whose secretion has been previously experienced. A selective pressure might thus exist favoring rare secretions, which is consistant with the well-known diversity of defensive compounds among sympatric insects.