Wing reduction is strongly related to environmental conditions. Those few species where males are affected inhabit coastal habitats or small oceanic islands, areas where wind conditions are such as to prevent individuals flying directionally towards potential mates. Jumping is a typical mode of progression in members of these species. Wing reduction in females is strongly related to the degree of egg maturation at eclosion. Well developed eggs leave little room for the flight muscles, which become reduced. Reduction of flight muscles leads to flightlessness, a first stage in wing reduction, Tympanal organs, which occur mainly at the base of the thorax or of the abdomen, also tend to become reduced or lost. Females emerging from the pupa with well developed eggs have no need to sustain themselves while the eggs mature. As long as males can find them, and provided eclosion occurs on a suitable foodplant, these females can lay their eggs rapidly. Species exhibiting these characteristics are often active in the cold season (e.g. many Geometridae) where rapid oviposition, occurring before extreme conditions overtake individuals, is clearly advantageous.In other words you can mate and lay all your eggs before you and your partner freeze to death and, since it is winter, you may be less likely to be eaten by a bird.
Reference: Scoble, Malcolm J. (1992) The Lepidoptera. Natural History Museum Publications, Oxford University Press