Sexual communication in the egg parasitoid Trissolcus brochymenae

Abstract

The males of the egg parasitoid Trissolcus brochymenae (Hymenoptera Scelionidae) exploit a short range pheromone for recognition of the other gender. To evaluate the role of this pheromone, the behavior of virgin males has been studied in closed arena when exposed to the following cues: 1) virgin females (alive, dead "washed" with solvents, dead" unwashed"); 2) dissected and re-assembled virgin females (females dissected into head, mesosoma, and gaster, then reassembled using two solvent "washed" parts and an "unwashed” part, or "unwashed" legs assembled with entire" washed" body); 3) "washed" females treated with acetone extracts (of virgin females and of legs). Males antennate and mount virgin "washed" females with lower frequency and duration compared to dead "unwashed" females, where physical and semiochemical stimuli are maintained. The extrusions of the penis never occur when " washed" females are employed. The site of production and/or release of the sex pheromone is the mesosoma with legs and wings. Stimuli from females with only the mesosoma "unwashed" induce more intense male response in terms of antennation, mounting and penis extrusion compared to stimuli from females assembled with "unwashed" head or gastro. The males antennate intensely and mount, without penis extrusion, the dead females treated with extracts of virgin females. Instead, mounts never occur when extract of legs was applied. The chemical analysis of acetone extracts of virgin males and females showed qualitative differences.