Male Mating Strategy and Preference for Females of Different Maturity Stages in the Small Water Strider, Microvelia iriomotensis (Heteroptera: Veliidae)

Abstract

Precopulatory mate guarding behavior is a common strategy among males of many species. Although this behavior increases male reproductive success, it is also costly for males. In Veliidae (Insecta: Heteroptera), male mate guarding of immature females has been reported in three species with pronounced sexual dimorphism, particularly in the nymphal stage. We observed a similar behavior in Microvelia iriomotensis (Heteroptera: Veliidae), in which males and females are characterized by small differences in body size. In this study, we conducted choice tests to quantify the preference of male M. iriomotensis for virgin females more than 3 d after emerging (senior females), virgin females within 24 h of emergence (junior females), and fifth-instar nymphs. Males more often approached senior females, with 80% eventually selecting these females as mates. To determine whether males mount female nymphs in the absence of adult females, we placed single mature virgin males in plastic cups along with one fifth-instar female nymph, and found that 79.6% of males mounted the nymphs within 5 h. The findings of this study indicate that senior females are the most advantageous mating partners for males and that mating after maturity would present the least risk to females. Our results also indicate that adult males will mount female nymphs even in species without a biased sex ratio. This behavior of M. iriomotensis males may be associated with the early sexual maturity of females, which enables them to lay fertilized eggs soon after emerging.