THE TRIBE OF THE BLUES 259 



Spring Azure has caused American scientists an immense 

 amount of patient labor. Over the vast territory from 

 Labrador across to Alaska and south to the Gulf of Mex- 

 ico, this little blue butterfly exists in so many different 

 forms that it requires special analytical keys to separate 

 them. Not only does it vary geographically so that in one 

 locality we find one form and in another a different form, 

 but it also varies seasonally to a marked degree. As one 

 would expect there is a striking difference in its annual 

 cycle between Labrador and the Gulf Coast. In the far 

 northern region there is but one brood a year, while in the 

 southern region there are at least two and perhaps more. 

 The variations in this butterfly are shown by the differ- 

 ences in the marking of both surfaces of the wings. These 

 markings may run from a faint blackish border along the 

 extreme margin and a few faint dots upon the under sur- 

 face, to a wide black margin around the wings and a deep 

 abundant spotting of the under surface. The markings of 

 the various forms are so uniform that the varieties are 

 easily distinguished. It is beyond the scope of this book 

 to attempt to differentiate all these varieties but any reader 

 interested will find an admirable summary of the con- 

 ditions illustrated by an excellent plate in Comstock's 

 "How to Know the Butterflies." The species as a whole 

 may be known from the fact that the upper surface is blue, 

 the lower surface ash-gray, more or less spotted with dark 

 brown, and the wings are without tails. {See plate, page 256.) 



The Strange Structures of the Larvae 



A remarkable variation of the adults is sufficient to give 

 this species a special interest, but the larvae also have a 

 unique attraction for the naturalist. The mother butter- 



