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

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 2nd instars, the longevity of adult O. strigicollis was much shorter than that from the 4th 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 1st to 3rd 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 2nd 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.