Aspects of the Foraging Behaviour of Tetrastichus Asparagi Crawford and Tetrastichus Spec. (Eulophidae), Gregarious Egg Parasitoids of the Asparagus Beetles Crioceris Asparagi L. and C. Duodecimpunctata L. (Chrysomelidae)

Abstract

Tetrastichus asparagi is a monophagous parasitoid of the common asparagus beetle (Crioceris asparagi) and does not accept the twelve-spotted asparagus beetle (C. duodecimpunctata) as host. A new species of Tetrastichus was found to attack the twelve-spotted beetle, and to refuse C. asparagi as host. Both species of Tetrastichus feed from freshly laid host eggs, and oviposit in eggs containing an advanced embryo or in larvae. The two Tetrastichus species are able to discriminate between unparasitized and parasitized hosts, and reject parasitized hosts after antennation or after probing with the ovipositor. Both Tetrastichus species are gregarious and lay about six eggs per oviposition. The importance of host selection and host discrimination in the foraging strategies of parasitoids is discussed.