Photoperiod, dormancy and the end of flight activity in Chrysopa cornea Stephens (Neuroptera: Chrysopidae)

Abstract

AbstractThe flight activity of Chrysopa carnea Steph. was studied during 1970–77 using 21 suction traps sited between 50 and 58°N. in northwestern Europe. Flight continues until late October and early November, well beyond the time (late August) when reproductive diapause is initiated at these latitudes. Flight ends as an all-or-none response to changing daylengths, the most northern populations having a shorter critical photoperiod, about 10 h 20 min, between morning and evening civil twilights, than the most southern ones, the critical photoperiod of which is about 10 h 45 min. By contrast, the critical photoperiod for induction of reproductive diapause is longer in northern populations. At latitudes less than 30° N. there is no winter dormancy but there is sometimes aestivation during the hottest period of the summer. In C. carnea, uniquely, winter dormancy has two distinct components, reproductive diapause and loss of flight activity, each controlled independently by photoperiod.