Insect gladiators: competitive interactions between three species of bethylid wasps attacking the coffee berry borer, Hypothenemus hampei (Coleoptera: Scolytidae)

The coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Scolytidae), originates from Africa and has since invaded all major coffee growing areas in the world. The parasitoid species, Cephalonomia stephanoderis Betrem and Prorops nasuta Waterston (Hymenoptera: Bethylidae) have been introduced into many countries as biological control agents. Recently, a further bethylid, Cephalonomia hyalinipennis Ashmead, was found naturally attacking the coffee berry borer in southern Mexico. The biologies of these three species are broadly similar. We evaluate the potential for interspecific competition by observing direct behavioral contests for hosts occurring between adult female parasitoids. We show that such contests readily occur and the loser is frequently killed. Prior ownership of hosts and ovipositional experience influence contest outcome, probably via the dynamics of egg maturation. There are also competitive asymmetries between these species: C. stephanoderis is generally the most successful. We discuss the implications of interspecific competition on the question of the best number and combination of natural enemy species for biological pest control.