Cuticular Hydrocarbons as Putative Sex Pheromones and Mating Peculiarity of Cuckoo Wasps Chrysis Angustula, Chrysis fulgida and Chrysis Iris (Hymenoptera: Chrysididae)

Abstract

Cuckoo wasps, also known as jewel or gold wasps (Hymenoptera: Chrysididae), are kleptoparasites and parasitoids that impose their offspring on the breeding efforts of other wasp species. Chrysidids oviposit in the nests of predatory wasps, and the hatched larva kills the host's larva and consumes the resources collected by the host. When a cuckoo wasp is detected by the host wasp, the host may abandon the nest or take other measures to prevent the development of the kleptoparasite. Chemical camouflage, particularly involving cuticlar hydrocarbons (CHCs), is crucial for cuckoo wasp females. There is a conflict because females need chemical signals that are easily detectable by males but not by the host wasps. It was demonstrated that virgin females of Chrysis angustula, Chrysis fulgida, and Chrysis iris contain CHCs that stimulate behavioral reactions in conspecific males. Coupled gas chromatography-electroantennogram detection analysis revealed 16 hydrocarbons with carbon chain lengths of C23-27 in virgin females: 6 in C. angustula, 8 in C. fulgida, and 13 in C. iris. A specific ratio of CHC compounds, including putative sex pheromones, was established for these three chrysidid species. Observations of re-mating refusals led to the hypothesis that virgin females of cuckoo wasps cease production of some unsaturated CHCs, functioning as sex pheromones, following mating. This change could reduce the risk of detection of CHCs traces left while entering the host's nest.