01806nas a2200133   4500008004100000245011500041210006900156260000800225300001100233490000700244520135400251100001801605856004901623       2009                        eng d00aOntogenetic dietary shift in the larvae of Cybister japonicus (Coleoptera: Dytiscidae) in Japanese rice fields0 aOntogenetic dietary shift in the larvae of Cybister japonicus Co  cJun  a856-600 v383 aA number of fragmentary reports suggest that the endangered diving beetle Cybister japonicus larvae feed on tadpoles, fish, and aquatic insects. However, no quantitative study on the feeding habits of C. japonicus larvae has been reported. In this study, field observations and rearing experiments were carried out to show the feeding ecology of C. japonicus larvae. Unlike previous commentaries, the first- and second-instar larvae of C. japonicus preyed on insects, mainly Odonata nymphs and Notonecta triguttata, irrespective of prey availability, but did not eat vertebrates such as tadpoles and fish in the field. On the contrary, the third-instar larvae fed on both insects and vertebrates. Rearing experiments showed that the number of Odonata nymphs consumed was significantly more than the number of tadpoles consumed by the first and second instars but third-instar larvae ate both the Odonata nymphs and tadpoles in the tadpole-Odonata nymph mixture experiment. The total body lengths of C. japonicus new adults in the Odonata nymph and tadpole-Odonata nymph mixture treatments were statistically equal. These results suggested that the first- and second-instar larvae of C. japonicus prey mainly on insects and do not eat vertebrate animals (insectivore), whereas the third-instar larvae fed on both insects and vertebrates (generalist).1 aOhba, Shin-Ya  uhttps://worldodonata.myspecies.info/node/202