48 BULLETIN 15 7, U. S. NATIONAL MUSEUM 



had been abundant the preceding summer, were wholly absent from 

 this region. 



As in the case of puddle butterflies, roadside butterflies are all 

 males, and practically all of them are fresh. Worn and battered 

 males and very worn females are occasionally seen, but are quite 

 exceptional. Roadside butterflies are always exceedingly pugnacious 

 — even vicious — and in this they differ from the typical social puddle 

 butterflies. They at once attack any individual of their own kind 

 that ventures near them, and they dash after bees, wasps, grasshop- 

 pers, large flies, and such of the larger butterflies as come their way. 

 All of them seem to have a special dislike for the large, slow-flying, 

 and rather clumsy milkweed butterfly {Danaus plexippus). For 

 some reason — possibly because of its black wings — the Carolina 

 locust {Dissosteira Carolina) always invites attack by the roadside 

 butterflies, particularly the buckeye {Jimonia lavinia). Farther 

 north it is attacked even by such small and weak species as the com- 

 mon co^Dper {Chrysopho)nus phlaeas hypophlaeas) . I have seen 

 smaller clear-winged grasshoppers attacked by the very smallest 

 of our local butterflies, the little tailed blue {Everes comyntas). 



In the case of the pearl crescent and of the buckeye I have 

 noticed that with the coming in of a new brood fresh males first 

 appeared along the roads, later gradually supplanting the worn 

 males in the fields, just as in the case of the puddle butterflies. 



Roadside butterflies appear to be fresh males that are unable to 

 cope with the older males in the fields and are therefore driven beyond 

 the limits of the areas wherein the females live. As they mature and 

 as the older males die off they are able to go back to the fields, in their 

 turn helping to drive out such young rivals as may appear. 



It should be noticed that some of our roadside butterflies — the 

 buckeye {Junonia lavinia)^ the red admiral {Pyrameis atalanta)^ 

 the hop merchant {Polygonia corrwia), and the question mark {P. 

 interrogationis) — occur in two forms, one of which is dark colored 

 and relatively inactive. In these butterflies the males of the dark 

 forms are never seen as roadside butterflies no matter how abundant 

 they may be. These dark forms, like the cabbage butterfly and the 

 orange clover among the pierids, seem not to be affected by pressure 

 of population. 



Roadside butterflies and puddle butterflies both represent surplus 

 males exiled by pressure of population long before there can be any 

 question of danger to the food plants. These exiled surplus males 

 are divided into puddle and roadside butterflies simply by their rela- 

 tive ability or inability to get along together. Species in which the 

 males, in the absence of the rivalry incited by the presence of fe- 

 males, are more or less gregarious become puddle butterflies, while 

 species in which the males are always quarrelsome whether females 



