Is early morning adult eclosion in insects an adaptation to the increased moisture at dawn?

Abstract

Many dipteran insects emerge as adults in early morning. One of the possible explanations for the adaptive role of early morning adult eclosion in insects is that the relatively humid and cool air would favor expansion of the wing in newly emerged adults. The dry and hot air around the noon would exert a harmful effect on the expanding wing by losing water at a faster rate. To confirm this hypothesis, the effect of desiccation and high temperature on wing-expansion of newly emerged adults of the onion fly, Delia antiqua was investigated. Desiccation had no or little effect on wing expansion, but high temperatures disturbed it significantly. It is likely that the increase in temperature in the middle of the day would interfere with the wing expansion of newly emerged adults, thereby selecting for the temporal gate of the adult eclosion in the early morning.