Seasonal Changes in Egg Diapause Induction and Effects of Photoperiod and Temperature on Egg Diapause in the Rice Leaf Bug, Trigonotylus caelestialium (Kirkaldy) (Heteroptera: Miridae).

Seasonal changes in egg diapause induction and the effects of photoperiod and temperature on egg diapause in the rice leaf bug, Trigonotylus caelestialium (Kirkaldy), were examined using a population in Joetsu, Niigata Prefecture. The bugs were reared from egg to adult at five temperatures, ranging from 22 to 34°C, combined with eight photoperiods, ranging from 9L–15D to 16L–8D. The critical photoperiod for egg diapause induction fell between 13L–11D and 14L–10D at 25°C. However, the females reared at 28, 31 and 34°C deposited a large proportion of non-diapause eggs even if the photophase was shorter than 14 h. When the females laying diapause eggs were transferred to 11L–13D at 31°C, the number of females laying non-diapause eggs increased gradually on and after five days. Therefore, it is concluded that the females reared at a high temperature from the egg stage produce non-diapause eggs regardless of the photoperiod, and that a high temperature at the adult stage causes females laying diapause eggs to deposit non-diapause eggs. Seasonal changes in the proportion of diapause eggs produced by females collected in the fields were examined for three years, from 1999 to 2001. In 1999 and 2001, the percentage of diapause eggs increased gradually in September. However, the percentage of diapause eggs produced by the females collected on 20 September, 2000, decreased to less than 10%. It is considered that this phenomenon was caused by high temperatures for 4 days in the previous week.