PHYSICAL AND CHEMICAL FACTORS INVOLVED IN HOST RECOGNITION BEHAVIOR OF ANAPHES IOLE GIRAULT, AN EGG PARASITOID OF LYGUS-HESPERUS KNIGHT (HYMENOPTERA, MYMARIDAE, HETEROPTERA, MIRIDAE)

Factors involved in host recognition by the egg parasitoid Anaphes iol e Girault (Hymenoptera: Mymaridae) have been investigated in the labor atory toward Lygus hesperus Knight (Heteroptera: Miridae). The female parasitoid readily recognized all the host eggs when they were embedde d by L. hesperus in an artificial substrate, as well as the eggs that were artificially reembedded at a normal depth, i.e., with only the eg g cap protruding above the substrate. However, the percentage of accep tance decreased and the examination time before acceptance increased i f the eggs were deeply embedded or more exposed. Completely exposed eg gs, with no substrate wounds involved, were accepted in half of the ca ses after a long examination, suggesting that although plant wound is not necessary for recognition, it affects the parasitoid's host select ion behavior. In fact, even artificial wounds not containing eggs or h ost-derived chemicals were sometimes probed. Almost all eggs soaked wi th different solvents were also accepted, but when applied to a smooth glass surface, chemicals extracted from the eggs elicited intense exa mination. Nevertheless, when solvent extracts were applied to glass cy linders, simulating host eggs, acceptance did not increase compared to untreated glass cylinders. It is suggested that both the host-derived chemical cues and the exudates from the substrate are involved in A. iole host recognition behavior together with physical factors, althoug h a contemporary combination of all these factors is not indispensable for host acceptance. (C) 1996 Academic Press, Inc.