Abstract: 【Aim】 Short photoperiod can influence cold hardiness of insects in diapause-inducing period. In order to clarify the effects of photoperiod on cold hardening of Chrysoperla sinica (Tjeder), our study focused on cold hardiness of Ch. sinica adults during the process of diapause-termination and nondiapause periods. 【Methods】 The supercooling ability (supercooling point, SCP; freezing point, FP) and the mortalities of overwintering adults from the natural population at -12℃ and the 2nd and 3rd instar larvae of the laboratory population at -7℃ were investigated during adult diapause termination and induction of the long (15L∶9D) and short photoperiods (9L∶15D) in the laboratory condition, respectively. 【Results】 The SCP values of overwintering Ch. sinica adults in December were mainly distributed between -10℃ and -14℃. The SCP values of 43.70% overwintering adults were below -12℃, and the mortality of overwintering adults at -12℃ for 1 d was 62.00%. The mortalities of overwintering adults at -12℃ treated under the long photoperiod were higher than those under the short photoperiod except those treated for 0 d, and significant difference existed among adults treated for 15, 20, and 25 d. The SCP and FP values of the 2nd and 3rd instar larvae in the short photoperiod were higher but had no significant difference from those in the long photoperiod (P>0.05), but the mortalities of the 2nd and 3rd instar larvae at -7℃ under the short photoperiod were 67.00%±4.04% and 24.33%±1.33%, significantly lower than those under the long photoperiod, which were 78.00%±1.33% and 53.00%±3.46%, respectively. 【Conclusion】 The results indicate that the Ch. sinica is a freeze-intolerant insect, and its cold hardiness could be enhanced under the diapause-inducing short photoperiod.

Key words: Chrysoperla sinica, diapause, photoperiod, overwintering adult, larvae, cold hardiness