Kairomonal effect of walking traces from Euschistus heros (Heteroptera: Pentatomidae) on two strains of Telenomus podisi (Hymenoptera: Scelionidae)

The semiochemical cues used by geographically isolated strains of the parasitoid, Telenomus podisi (Ashmed), to find eggs of the stink bug Euschistus heros were investigated. Two strains of Te. podisi, maintained on eggs of a South American host (E. heros) were studied. One parasitoid strain originated from specimens collected near Brasilia, Brazil (SA strain), and a second strain originated from specimens collected at Beltsville, Maryland (NA strain). Cold tolerance tests of adults from the NA and SA Te. podisi strains, analyses of the cuticular hydrocarbons between the two strains, and crossing experiments between strains each indicated consistent differences between the NA and SA strains. Subsequent experiments using E. heros showed that SA Te. podisi females specifically recognize traces left on the substrate by walking E. heros females and then search intensively the area of the 'footprints', apparently looking for an egg mass to parasitize. By contrast, Te. podisi females of the NA strain are incapable of recognizing the footprints of E. heros females despite the fact that these parasitoids were reared from eggs of E. heros. The possibility that the two strains are actually different species is discussed.