Abstract
To confirm inheritance of wing form and reproductive diapause of female Thrips nigropilosus, and prevalence of brachypterous and diapausing females in winter populations on the Ryukyu Islands, field sampling and rearing trials at 18°C were conducted. Kainan-shi (34.2°N) females from Honshu Island developing under short-day photoperiods (≤11.5 hours light) entered reproductive diapause, whereas Miyakojima-shi (24.1°N) and Yaese-cho (26.1°N) females from the Ryukyu Islands never entered diapause even under shorter day lengths. All Kainan-shi females molted into brachypters under short-day conditions (≤11 hours light) and became macropters under long-day conditions (≥12 hours light). The percentage of brachypters in Yaese-cho and Miyakojima-shi females developing under short-day conditions (≤11 hours light) was less than 50%, and no females developed into brachypters under photoperiods with at least 11.5 hours of light. Under short-day conditions (10 hours light), 93% of females molted into brachypters and 35% of females entered diapause in F1 hybrids between Yaese-cho females and Kainan-shi males. Macropters and brachypters were found in the field in overwintering adult females on Okinawa Island.
