298 THE entomologist's record. 



the larger and lighter forms have developed more slowly, with 

 a longer period of growth, and less intense metabolism ; in 

 short, as Mr. P. Geddes would say, the first have developed 

 katabolically, the last anabolically. When eggs or seeds are 

 subjected to a low temperature, although life is not necessarily 

 extinguished, growth and metabolism cease. The winter in 

 North America is sufficiently cold to have a like effect upon 

 hybernating pupae, — they live, but do not grow.^ The summer 

 comes on with comparative suddenness, and the hot rays of 

 the sun throw them into the most intense metabolism, 

 so that the imago emerges with the wing-structures, so far 

 from having developed slowly and in the cold, presenting every 

 evidence of rapid change. In a climate like that of England, 

 however, the winter is not cold enough to entirely arrest wing- 

 growth, and hence the spring emergences present usually some 

 evidence of slow change accompanied by gradual growth. It 

 will probably be objected to the above theory, that summer in 

 America is at least as hot as spring, so why do not the summer 

 forms present at least as much evidence of quick change ? To 

 which I can only reply, that I am inclined to suppose that the 

 vital structures and organs of generation develop at a much 

 lower temperature than the wings, of which theory confirmation 

 will be seen in such examples as the normally wingless, but 

 otherwise perfect, Chorezus ineptus, which is said often to 

 develop wings in unusually hot seasons. I hold, therefore, 

 that the North American species hybernating in the pupal 

 state attain a nearly perfect development of their vital functions 

 before the spring, although wing-growth has been in abeyance ; 

 but those pupating and emerging in the summer cannot assume 

 the perfect state until the time necessary for the growth of the 

 vital and reproductive organs has expired, so that the wings, 

 developing all the while, have no period of sudden quick 

 change like those of the spring brood. The seasons in Europe 

 were probably at one time much more marked, and possibly 

 some of the Mediterranean species arose as summer forms of 

 northern species, or vice versa : for instance, in the genus 

 Gonopteryx. Colias eurytJieme, of North America, has in the 

 summer brood an orange patch on the fore wings similar to 

 that of Gonoptejyx deopatra, but the spring emergence has the 

 patch reduced, and sometimes almost absent, thus resembling 

 G. rhamni. Now, supposing the climate were to become more 



^ Develop rather than "grow." I believe all size variations to be phytophagic, 

 and as such, to be determined in the larval stage. — ^J.W.T. 



