Patterns of Local Distribution and Coexistence of Two Giant Water Bugs, Diplonychus japonicus and D. major (Hemiptera, Belostomatidae) in Okayama, Western Japan

Patterns of local distribution of D. japonicus and D. major in Okayama, Japan were investigated. The two species occurred in different habitats and seldom coexisted. The main factor causing such an exclusive distribution could be a difference in preferred water temperature between the two species. D. japonicus lived in warmer habitats than D. major. In a few sites where water temperature was intermediate between the preferred habitats of the two species, they were found coexisting.