Feeding Preferences of the Endangered Diving BeetleCybister tripunctatus orientalisGschwendtner (Coleoptera: Dytiscidae)

摘要

The numbers ofCybister tripunctatus orientalisGschwendtner diving beetles are declining in most regions of Japan, and it is included in the Red Data List of species in 34 of 47 prefectures of Japan. However, basic ecological information aboutC. tripunctatus orientalis, such as its feeding habits, remains unknown. In order to elucidate the feeding habits ofC. tripunctatus orientalislarvae, feeding preference experiments were carried out in 2nd and 3rd instar larvae. The number of Odonata nymphs consumed was significantly higher than the number of tadpoles consumed, indicating thatC. tripunctatus orientalislarvae prefer Odonata nymphs to tadpoles. In addition, all the first instar larvae ofC. tripunctatus orientalisdeveloped into second instars when they were supplied with motionless Odonata nymphs, but their survival rate was lower when they were supplied with motionless tadpoles. These results suggest thatC. tripunctatus orientalislarvae prefer insects to vertebrates.