EFFECTS OF TEMPERATURE AND PHOTOPERIOD ON NYMPHAL DEVELOPMENT OF THE STINK BUG, PYRRHOCORIS-SIBIRICUS KUSCHAKEWITSCH (HETEROPTERA, PYRRHOCORIDAE)

The stink bug, Pyrrhocoris sibiricus, is a ground-dwelling seedfeeder. The effects of temperature and photoperiod on nymphal development and adult body size were investigated under six rearing conditions with d ifferent temperature (20, 25 and 30 degrees C) and photoperiod (12L-12 D and 16L-8D) regimes. The survival rate in the nymphal stage was high er and the nymphal developmental period was shorter at higher temperat ures. Adult body size in terms of body length became larger with incre ases in temperature, and was largest at 30 degrees C under 12L-12D. Th ese results showed that this species is adaptive to high temperatures. In the field, the body size of adults that emerged from mid-August to late September was largest (SAKASHITA, unpublished data). This coinci ded with the fact that adult body size was largest at high temperature s under short day length. The nymphal developmental period. of this sp ecies was shorter under 12L-12D than under 16L-8D at 20 degrees C. It is considered that this leads to completion of nymphal development bef ore the onset of the winter season.