Physical and Chemical Factors Involved in Host Recognition Behavior ofAnaphes ioleGirault, an Egg Parasitoid ofLygus hesperusKnight (Hymenoptera: Mymaridae; Heteroptera: Miridae)

Factors involved in host recognition by the egg parasitoidAnaphes ioleGirault (Hymenoptera: Mymaridae) have been investigated in the laboratory towardLygus hesperusKnight (Heteroptera: Miridae). The female parasitoid readily recognized all the host eggs when they were embedded byL. hesperusin an artificial substrate, as well as the eggs that were artificially reembedded at a normal depth, i.e., with only the egg cap protruding above the substrate. However, the percentage of acceptance decreased and the examination time before acceptance increased if the eggs were deeply embedded or more exposed. Completely exposed eggs, with no substrate wounds involved, were accepted in half of the cases after a long examination, suggesting that although plant wound is not necessary for recognition, it affects the parasitoidʹs host selection behavior. In fact, even artificial wounds not containing eggs or host-derived chemicals were sometimes probed. Almost all eggs soaked with different solvents were also accepted, but when applied to a smooth glass surface, chemicals extracted from the eggs elicited intense examination. Nevertheless, when solvent extracts were applied to glass cylinders, 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 inA. iolehost recognition behavior together with physical factors, although a contemporary combination of all these factors is not indispensable for host acceptance.