CHEMICAL SIGNALS MEDIATING INTERACTIONS BETWEEN GALERUCA-TANACETI L. (COLEOPTERA, CHRYSOMELIDAE) AND ITS EGG PARASITOID OOMYZUS-GALERUCIVORUS (HEDQVITS) (HYMENOPTERA, EULOPHIDAE)

Chemical signals mediating interactions between Galeruca tanaceti and its egg parasitoid Oomyzus galerucivorus (Hymenoptera, Eulophidae) wer e studied. Neither odor of gravid females of G. tanaceti nor volatiles of their feces were attractive to the parasitoid, However, the presen ce of the beetles' feces on a substrate arrested the parasitoid and el icited frequent antennal drumming. Thus, feces may contain a kairomone important for host finding. Odors of damaged and undamaged host plant s had no effect on the parasitoids, O. galerucivorus did not detect it s host eggs at close range but encountered them by chance. Neither the structure nor the dark color of the egg surface play a key role in ho st recognition, but chemicals of the extrachorion which could be isola ted by dichloromethane. Fractionation of the dichloromethane extract b y TLC revealed a single active fraction which induced host recognition behavior. Since rite eggs of G. tanaceti contain anthraquinones and a nthrones which are active as feeding deterrents against predators, we hypothesized that reproductive success of O. galerucivorus is due to s equestration of these protective compounds. However, GC-MS analyses re vealed that there was no transfer of them from the host egg into the a dult parasitoid.