中华草蛉成虫越冬前取食对越冬死亡率的影响

越冬代中华草蛉成虫,在越冬前取食一定的时间后,均能改变体色,开始越冬。越冬期间的死亡率与冬前取食时间的长短及取食量有密切的关系。冬前获得充足营养的成虫贮存在不生火的屋内,越冬期间死亡率很低,至8月20日成活率仍有80％;而没有充分取食的成虫则大量死亡。作者认为北京地区每年春季草蛉数量很少与越冬前田间成虫食料不足,因而越冬期间大量死亡有关。对保护草蛉越冬的途径提出了建议。

EFFECT OF PRE-DIAPAUSE FEEDING ON THE WINTER MORTALITY OF CHRYSOPA SI NICA

Population of Chrysopa sinica in the Beijing area is usualy high in summer and autumn. In the winter the number of adults diapausing is high, generally only few adults can be found in the field the next spring. Natural control of insect pests by C. sinica is not significant until its population ' is built up in mid-summer.Possible causes for the low population in spring were studied. Labora- tory experiments showed that adults of the over-winter generation after feeding for various period of time, changed their body coloration and entered into diapause. Mortality during diapause was closely related to the nutrition condition of the adults. When adults properly fed before diapause were stored in an un-heated room, only a few died in winter and 80% still alive at the end of March. While those inadequately fed had very rare chance of survival.It is clear then that the low population of C. sinica in spring in the Beijing area is due to the shortage of adult food such as honey dew and nectar in the field after harvest of the main crops, so many over-wintering a-dults are poorly nourished and will not survive the winter. Ways to improve this situation are discussed.