64 



NATURE SKETCHES IN TEMPERATE AMERICA 



Lyell, "I always repeat to myself that we hardly know why 

 any one single species is rare or eoiniiion in the best-known 

 countries." Whether a species is abundant in a given locality 

 is necessarily determined by natural causes. Chief among the 

 conditions favoring existence of a species are its adjustment to 

 its surroundings, that is, maintaining itself against competi- 

 tion with members of the same species and other enemies, and 

 the resistance to climatic conditions. I have attempted in 

 the foregoing account to exemplify by the polyphemus moth 

 some of its adaptations to these varied conditions. 



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^^-f .-/^4 



i'- f U 



Protective resemblance in the snout hntterflij (Libythca back- 



manm). The palpi jjroject forward, so as to resemble 



a stem, the underside of the vnngs simulale a 



dried leaf. This insect appears in May. 



