35 



is so characteristic of winter-emerging moths we must conclude 

 that it serves some definite purpose in connection with the time of 

 year at which they appear. That these species ate descended from 

 ancestors having normally winged females is evidenced by their 

 belonging to families quite normal in this respect, and by the fact 

 that the pup^e possess well developed, almost normal, wing cases. 

 So we must conclude that the possession of wings, at least by the 

 ? , must have been of some definite disadvantage to the species, 

 and that in the course of evolution they have been lost. The ^ J are 

 of course fully winged ; as they have to seek out the comparatively 

 stationary females the possession of full powers of flight would 

 appear to be even more necessary to them than to most species ; 

 evidently they are uninfluenced by the factors that led to the loss of 

 wings in the female. What then can have been the danger of wings 

 to the female, and to the female alone ? The most obvious sugges- 

 tion is, that by the possession of wings they might wander from a 

 situation suitable for depositing their eggs. A moth when it 

 emerges from the chrysalis at the foot of the tree upon which the 

 caterpillar fed, will usually climb up the stem of the tree to develop 

 and dry its wings, and very frequently the female will wait here to 

 be impregnated before attempting flight. In the case of these 

 winter emerging moths it was presumably dangerous to the species 

 for her to fly after impregnation, probably because of the unlikeli- 

 hood of her finding another tree suitable for depositing her ova. 

 But why should this danger be greater in winter than for the vast 

 majority of moths at other times of the year ? This question has 

 puzzled many entomologists, and various attempts at a solution 

 have been put forward. It has been suggested that owing to the 

 likelihood of rough weather the females might be blown away from 

 their foodplants with the risk of not being able to find them again, 

 or that her wing expanse is liable to damage in high winds, possibly 

 to such an extent as to prevent her attaining the food plant proper 

 to her species. 



Mr. Hudson (13) has drawn attention to a very similar condition 

 of things amongst the winter-emerging moths in New Zealand, and 

 advances the theory that the numbing effect of cold may be the 

 particular danger threatening the female, rendering her perhaps unable 

 to move and seek out the foodplant, though retaining sufficient 

 vitality to deposit her eggs wherever she may happen to be ; it 

 would therefore be important for her that she should not be able to 

 leave the foodplant in case of being overtaken by cold. In any case 



