Induction and Termination of the Reproductive Diapause in the Minute Pirate Bug Onus strigicollis Poppius (Hemiptera: Anthocoridae)

Abstract

This study was carried out to investigate the effect of the photoperiod and temperature on the reproductive diapause in Orius strigicollis. The photo-period and temperature affected nymphal development, adult longevity, diapause induction, and diapause termination in O. strigicollis. At 18 °C, nymphs developed significantly faster at a photoperiod of 8:16 (L:D) h than at a 12:12 (L:D) h. When kept at 15°C and 9:15 (L:D) h continuously from the 2 nd instars, the longevity of adult O. strigicollis was much shorter than that from the 4 th instars, but their longevity was not different between the genders. At 18°C, when continuously kept under short photoperiod from the first three nymph stages, 100% of adults entered the reproductive diapause within 40 days after adult eclosion. From the 1 st to 3 rd instars, O. strigicollis displayed a long-day response with a critical photoperiod between 12 h and 14 h at 18°C within 20 days after adult eclosion. When continuously kept at 15°C and 18°C with a 9:15 (L:D) h photoregime from the 2 nd instars, all females entered the reproductive diapasue, while the diapause incidence at 20 °C and 25 °C was quite low even within 20 days after adult eclosion. No diapause incidence was found when only the egg or the first three nymph stages were kept at 18°C and 8:16 (L:D) h, while the later two nymph stages showed a slight increase in diapause incidence. Combined exposure from the nymph to adult stages to 18°C and 8:16 (L:D) h is necessary to attain 100% of diapause incidence. Diapause in O. strigicollis was terminated rapidly as long photoperiod and/or lower temperature was treated.