( xc ) 



— i.e. that warmth heightens and accelerates, and coolness 

 retards, in other words, that these species would respond in a 

 normal manner to change of temperature within the limits 

 of health. 



Seasonal influence— Temperature. 



The rest of the world is all more or less " seasonal " and the 

 main distinction between the seasons is that of temperature. 

 In many countries containing an abundance of Lepidoptera the 

 principal climatic distinction is that between dry and wet 

 seasons, these, however, being often more or less associated 

 with changes of temperature. The recorded accurate observa- 

 tions on the effects of temperature in relation to Lepidoptera 

 are far more considerable than those on the effects of wet and 

 dry seasons, and, without in any way seeking to minimize the 

 operation of these, I practically limit myself to the former, 

 not only because I think it the most far-reaching and 

 penetrating influence, but also because the materials accessible 

 for the purpose are so much more abundant. 



Seasonal Lepidoptera. 



There are, as we know, places extreme in climate, such as 

 North-Eastern Siberia, where the annual l'ange of temperature 

 is over 100° F. (56° C), from about - 50° F. ( - 46° C.) in 

 January to over + 50° F. (10° C.) in July, and the polar regions, 

 where some of the Argynnids and Satyrids are found, and 

 where the actual life of a butterfly is limited to about a month, 

 though the whole duration of its life may extend over several 

 years, and the food plants are covered with ice and snow 

 except for about six weeks. Though the range of temperature 

 in the seasonal world in general does not approach such 

 extremes, the seasons are strongly marked in most of it, and 

 whenever the winter is sufficiently severe, either by its direct 

 effect or its indirect effect in destroying green food, to impose 

 a lengthened period of rest, the Lepidoptera are, like the 

 climate, seasoned in their habits ; and, the seasons having an 

 annual cycle, the normal life of a lepidopterous insect is 

 annual also, or at least is comprised within a year, its rate of 





