Identification of sex pheromone components in Trissolcus brochymenae females

Long- and short-range sex pheromones appear to play a crucial role in the mate finding and courtship behaviour of most parasitic Hymenoptera. Yet these parasitoids have been rarely investigated and only a few pheromones have been identified. Recent studies have shown that sexual communication of Trissolcus brochymenae (Hymenoptera: Platygastridae), a quasi-gregarious egg parasitoid of the harlequin bug, Murgantia histrionica (Heteroptera: Pentatomidae), starts before contact between males and females and is mediated by chemical compounds produced by virgin females, which triggers the courtship behaviour of males. In this study, the pheromone components involved in the short-range recognition of T. brochymenae females by males were investigated using electrophysiological and behavioural methods. Female body extracts were analyzed through EAG and GC-EAD and the active compounds were identified through GC-MS. Then the behavioural responses of virgin males to the GC-EAD active compounds were evaluated in closed arena bioassays. Two active compounds in EAG and behavioural tests, tetradecyl acetate and (Z)-11-hexadecen-1-yl acetate, were identified as sex pheromone components. Both compounds triggered intense male antennation and mount when applied to solvent-washed female cadavers. Dose-response tests showed different curves for the two compounds. This is the first study on the identification of sexual pheromones in Platygastridae. The difficulties of sex pheromone investigations on such minute egg parasitoids and the possible exploitation of these new findings in integrated pest management are discussed.