Larval Rearing Methods for Two Endangered Species of Diving Beetle, Cybister chinensis Motschulsky, 1854 and Cybister lewisianus Sharp, 1873 (Coleoptera: Dytiscidae), Using Laboratory-Bred Food Prey

Abstract

To facilitate ex-situ conservation of predaceous endangered insect species large numbers of live prey organisms are typically collected from the natural environment, potentially exacerbating biodiversity decline. To address this issue, two endangered beetle species (Cybister chinensis Motschulsky, 1854 and Cybister lewisianus Sharp, 1873) were reared using only laboratory-bred food. The beetle larvae were provided with laboratory-bred two-spotted cricket (Gryllus bimaculatus DeGeer; Orthoptera: Gryllidae) larvae as prey. The survival rates of the beetle larvae were as follows: C. chinensis, first instar larvae, 100% (n = 25), second instar larvae, 100% (n = 25), and third instar larvae, 92% (n = 23); C. lewisianus, first instar larvae 96% (n = 24), second instar larvae 92% (n = 23), and third instar larvae 92% (n = 23). The body length of adult insects fed laboratory-bred crickets did not significantly differ compared to the body length of field-collected adults.