Natural selection of butterfly anti-sex pheromones by hitchhiking wasps
Many insects possess a sexual communication system that is vulnerable to chemical espionage by parasitic wasps. We discovered that hitch-hiking Trichogramma egg parasitoids can exploit the antiaphrodisiac (AA) pheromones emitted by butterflies. These pheromones are passed from male butterflies to females during mating to render them less attractive to conspecific males. They are known from butterflies from the families Pieridae and Nymphalidae (Heliconiini). When a tiny Trichogramma wasp detects the antiaphrodisiac, it rides on a mated female butterfly to a host plant and then parasitizes her freshly laid eggs. PhD students Xianhui Shi and Liana Greenberg aim to understand how selection by egg parasitoids has contributed to the evolution of AAs in butterflies.