Life cycle of the endangered crawling water beetle Haliplus basinotatus (Coleoptera: Haliplidae) in an irrigation pond and implications for its conservation

Abstract

Haliplidae are a family of small water beetles that play crucial roles in wetland ecosystems, including bioturbation and serving as prey within food webs. In Japan, many Haliplidae species are rapidly declining, and the conservation of their habitats has become an urgent priority. Haliplus basinotatus, a crawling water beetle inhabiting vegetation-rich wetlands, is listed on the Japanese Red List, but its biology remains poorly understood. We conducted field surveys in an irrigation pond and rearing experiments to investigate the life cycle of H. basinotatus. Our results revealed a univoltine life cycle: adults lay eggs in late summer, larvae hatch in autumn and grow over 8 months, and new adults appear the following summer. Furthermore, our findings suggest that adults disperse to surrounding ponds during the summer and congregate in breeding-suitable ponds in the autumn. In conclusion, the conservation of H. basinotatus in irrigation ponds requires maintaining aquatic habitats during winter, appropriately managing vegetation to support charophyte growth, and ensuring habitat connectivity within the network.