Thrips (Thysanoptera: Thripidae) on the flowers of a dioecious plant, Dioscorea japonica (Dioscoreaceae)

The genus Dioscorea L. (Dioscoreaceae) is widely distributed throughout Africa and Asia and includes 500 to 650 species (Burkill 1960; Miege and Lyonga 1982), almost all of which are dioecious (Terauchi 1990). Pollination of species in this genus has received little attention because many of the cultivated species are propagated vegetatively from tubers. Insect visitors to flowers have been reported for two species, D. alata L. from India (Abraham and Nair 1990) and D. rotundata Poir. from Nigeria (Pitkin 1973; Segnou et al. 1992; Bournier 1994). Dioscorea japonica Thunb. is found throughout Japan, Korea, and China (Ohwi and Kitagawa 1983), but insect visitors to the flowers have not previously been reported. We investigated the insect visitors to flowers of D. japonica because the insect fauna associated with one species of a genus often differs from that associated with other species of the genus and may vary within a single species between different geographic regions (Kobayashi et al. 1999).