Effects of photoperiod and temperature on the development and diapause of the endangered butterfly Zizina emelina (Lepidoptera: Lycaenidae)

Abstract

We investigated the effects of photoperiod and temperature on the development of the endangered butterfly Zizina emelina under laboratory conditions, and its seasonal occurrence in Osaka Prefecture, central Japan in 2009. At 20 °C most individuals reared under conditions of <13 h of light/day entered diapause during the larval stage, whereas those reared under ≥14 h of light/day developed into adults without any developmental arrest. At 25 °C, none of the individuals entered larval diapause irrespective of the photoperiod. The critical photoperiod for diapause induction at 20 °C was 12 h 40 min. Almost all larvae that had been in diapause for 2 months (with or without chilling at 10 °C) developed into adults, and the mean pupation period after transfer to 25 °C under 16 h of light/day differed little between the two groups, suggesting that chilling is not necessary to terminate larval diapause in Z. emelina. Adults were continuously found from late April to late October, with a low population density during spring. We estimate that this species has 5–6 generations in Osaka, according to the developmental threshold, effective accumulated temperature, and critical photoperiod data obtained from the rearing experiment. The estimated seasonal life cycle was similar to the seasonal prevalence observed in the field.