WITH FUR THER HIS TOR1E S. 1 63 



butterflies from the tropics northward are perhaps 

 less striking because so gradual, and seem fairly 

 connected with physical conditions ; color is de- 

 pendent upon light, and of course the greatest 

 intensity and duration of light is in the tropics ; 

 the two phenomena are completely parallel. It 

 is, however, harder to understand a very curious 



FIG. 137. Papilio Antiopa, nat. size ; under surface on right (Harris). 



sport in one of our butterflies, which is known to 

 have originated within ten years. There are a 

 very few butterflies common to this country and 

 Europe ; three, the Painted Lady, the Red Ad- 

 miral, and the Camberwell Beauty [Fig. 137], have 

 long been known to inhabit both countries ; and 

 not a few entomologists have attempted to find 

 some difference between representatives from 



