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their immediate progeny, only one pair arrives at ti^e stage in 

 their turn of laying eggs, it is evident that in the case of those 

 species which pass the winter in one of the early stages, the 

 number of individuals extant during the winter must be actually 

 greater than the number of the parent generation, at any rate 

 than of such of them as succeed in reproducing their species. 



The reaction of winter upon insect life is felt both directly and 

 indirectly. Directly by the withdrawal of the energising influence 

 of sunshine, while the low temperatures induce lethargy and 

 torpidity ; (these influences can be observed in a minor degree on 

 any cold, dull day in summer) ; indirectly by the cessation of 

 vegetable growth and the dying down of many of the herbaceous 

 plants, which means the cutting off of the food supply of a large 

 part of the insect host. These consequences of winter are not 

 equally felt by all insects. Certain lepidopterous larvse, for instance, 

 whose food supply is not seriously interfered with, are very much 

 more aflected by winter than others in similar circumstances, some 

 seeming to wake up and be ready to feed during any warm spell 

 throughout the winter, while others will commence hibernation 

 comparatively early in the autumn and not wake until spring is 

 well advanced. Those insects whose food supply is completely cut 

 off must perforce find some means of tiding over the barren months 

 of winter until the fresh spring growth enables them to feed again. 



Now of the four main stages of an insect's life two, the egg and 

 the pupa, are in any case periods of more or less prolonged fasting, 

 and very naturally, as may be thought, a large number of insects 

 take advantage of one or other of them as a convenient stage in 

 which to tide over the winter months. 



■ In spite, however, of apparent quiescence, both these stages are 

 in reality periods of histological activity and reorganisation ; in the 

 egg the cellular tissue is dividing and differentiating to form the 

 parts and organs of the young larva, while in the pupa these organs, 

 having reached their full size, are being altered, or even broken up 

 and reformed as the organs of the perfect insect, often very different, 

 and required to perform very different functions from those of the 

 larva. ■ It is not then altogether surprising that many insects have 

 adopted one of the physically more active though physiologically 

 comparatively quiescent stages, i.e., the larva or the imago, as that 

 in which to pass the winter. 



In this case the insect is said to hibernate, by which term is 

 meant to enter into a torpid condition during which no food is taken, 



