Feeding Preferences of the Endangered Diving Beetle Cybister tripunctatus orientalis Gschwendtner (Coleoptera : Dytiscidae)‎

Abstract EN

The numbers of Cybister tripunctatus orientalis Gschwendtner 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 about C.

tripunctatus orientalis, such as its feeding habits, remains unknown.

In order to elucidate the feeding habits of C.

tripunctatus orientalis larvae, 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 that C.

tripunctatus orientalis larvae prefer Odonata nymphs to tadpoles.

In addition, all the first instar larvae of C.

tripunctatus orientalis developed 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 that C.

tripunctatus orientalis larvae prefer insects to vertebrates.