Abstract
Diving beetles inhabiting rice paddies and neighboring ponds are thought to be endangered due to various threatening factors. We investigated the regional red data book to evaluate the status of 133 species of diving beetles in Japan. Hydaticus satoi was already extinct from eight prefectures, Cybister tripunctatus orientalis from six, Dytiscus sharpi from four, and Cybister japonicus from two, indicating their high-risk status. Four common small-bodied species, including Laccophilus difficilis, are listed in the RDB of Kanagawa Prefecture. We evaluated the status of D. sharpi, for which information is relatively abundant, and found that all habitats known before World War II had already been developed. After the rediscovery of this species in Chiba Prefecture in 1984, several habitats were found in several prefectures. However, approximately 60% of the habitats have been lost since then. Several habitats remain in Ishikawa Prefecture but habitat loss due to the abandonment of rice paddies, development, over-exploitation, and invasion by alien species is of great concern. However, a number of conservation measures have been implemented, such as the flooding of abandoned rice paddies and the restoration of traditional farming practices.
