Captive breeding of two insular populations of Pachyrhynchus sarcitis (Coleoptera: Curculionidae) from Lanyu and Babuyan Islands

Endemic species of oceanic islands are vulnerable due to their geographical isolation and small population sizes. For endangered island species, captive breeding program is an important strategy for conservation and sustainable management. Pachyrhynchus sarcitis is a flightless weevil decorated with colourful markings and distributed exclusively on several islets of Southeast Asia including Lanyu, Ludao, and Babuyan Islands. The life history of threatened Pachyrhynchus species of these islands was poorly known. This study reared P. sarcitis from Lanyu and Babuyan Islands for the first time in the laboratory using their host plant (Leea guineensis). The two island populations showed significant differences in instar numbers, in which the weevils from Lanyu Island had a higher instar number regardless the length of developmental duration. The adult body size of both sexes of the Babuyan population became smaller under laboratory condition; whereas Lanyu population in the laboratory did not show this trend. The differences in larval development might suggest local adaptation to the host plants or other life history associated characteristics which requires further research.