Effects of diapause duration on diapause termination and post-diapause reproduction in Orius sauteri

To determine the duration of winter conditions necessary to achieve successful termination of diapause in Orius sauteri (Poppius) (Hemiptera: Anthocoridae), nymphs were subjected to a L12:D12 photoperiod at 18 degrees C and emerged females were maintained under the same conditions for 15, 30, 45, or 60 days. After the respective period, the females were subjected to a photoperiod of L16:D8 at 25 degrees C, and four parameters were evaluated: pre-oviposition period, oviposition period, total number of eggs laid per female, and longevity. In females of all four groups of different rearing durations at 18 degrees C, oviposition commenced within 2 weeks. There was a strong correlation between the pre-oviposition period and the duration of rearing at 18 degrees C, with the pre-oviposition period of females reared for 60 days being 4.5 +/- 0.7 days, which was equivalent to that of non-diapause females. Although the pre-oviposition period of females reared for a 30-day period was approximately 10 days, these females laid the highest total number of eggs among the four treatment groups. Longevity was found to be negatively correlated with the length of rearing duration at 18 degrees C, whereas neither oviposition period nor total number of eggs per female was significantly correlated with the rearing duration. We subsequently subjected females collected in the field in late October to the same rearing conditions at 18 degrees C for 30, 45, 60, or 90 days, and accordingly found that the pre-oviposition period of field-captured females was longer than that of the laboratory-bred females. However, the highest total number of eggs laid by field-captured females was observed in those subjected to a 30-day rearing period. Based on these observations, we can conclude that a period of 30 days under conditions of 18 degrees C is sufficient to induce diapause termination without reducing fecundity.