Effects of different prey on larval growth in the diving beetle Cybister sugillatus Erichson, 1834 (Coleoptera: Dytiscidae)

Abstract The population size of the diving beetle Cybister sugillatus Erichson 1834 (Coleoptera: Dytiscidae) has been declining in Japan; therefore, there is a need to understand their fundamental ecology for conservation purpose. Understanding the feeding habits in the larval stage will contribute to habitat restoration and ex situ conservation. In this study, we investigated the effects of the availability of different kinds of prey, such as Odonata nymphs and tadpoles, on larval growth of C. sugillatus. The results showed that Odonata nymphs were the preferred prey for larval growth because C. sugillatus larvae did not show significant growth on tadpoles alone. This trend was also observed in other Cybister species. Our results suggest that habitat restoration requires the development of an environment rich in a variety of aquatic invertebrates, including Odonata nymphs. In ex situ conservation, stable rearing and breeding of C. sugillatus can be made possible by providing them with Odonata nymphs as food.