Mating competitiveness of male coconut hispine beetle infected with <i>Mesenetia</i>

Abstract Releasing sexually sterile male insects to reduce mating success of wild females and wild males is known as a control strategy of serious insect pests. In this strategy, sexually sterile males are expected to be able to mate with wild females in the field where wild males are also present. Competitiveness of sterile males is thus critical in this strategy. In this study, we investigated the effects of infection of Mesenetia , bacterial symbionts that induce cytoplasmic incompatibility, on male competitiveness in the coconut hispine beetle Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae). First, we investigated the mating competitiveness of B. longissima males infected with Mesenetia through a process of releasing infected and uninfected males into a plastic cup with uninfected females. Egg hatch rates in different I/U ratios (ratio of infected males to uninfected males)—0.2, 0.5, 1, 2 and 5—were then recorded. Results showed that hatch rates decreased with the increasing I/U ratio. The model assuming equal mating competitiveness fit well to observed hatch rates. We then investigated sperm utilization in females under sequential mating with infected and uninfected males. Results showed that hatch rates drastically decreased after second mating when females mated with uninfected males first and infected males second. These suggest that B. longissima males infected with Mesenetia have comparable mating and sperm competitiveness with that of uninfected males.