178 THE COLORING OF BUTTERFLIES, 



pendent upon locality and season, there are other 

 minor distinctions that appear to embrace all 

 localities and seasons. As we go from north 

 southward, or as, in any given locality where the 

 insect is double-brooded, the season advances, we 

 find the individuals growing larger, less heavily 

 marked beneath, and, in the female, paler on the 

 upper surface. 



In this butterfly, then, we have a curious com- 

 bination of phenomena. There is first a great 

 difference in the aspect of the insect in widely 

 separated localities, so that local races have been 

 described as distinct species ; then there is simple 

 dimorphism occurring in the spring brood in a 

 central locality, but not at the two extremes ; a 

 simple dimorphism partaking of a seasonal char- 

 acter, inasmuch as the earlier individuals of the 

 affected brood are of one form, and the later of 

 another ; not unlikely it will be proved that, as 

 in the Zebra Swallow-tail, this secondary seasonal 

 dimorphism is correlated with premature hiber- 

 nation of some spring and summer chrysalids, 

 and that the spring brood as a whole is composed 

 of fragments of all the broods of the previous 

 year. Besides this secondary seasonal dimor- 

 phism, we have a pure seasonal dimorphism, in the 

 distinction of the spring and summer broods, 

 wherever more than one exists ; and finally, in 

 the south we have a distinct form of dimorphism 



