BUTTERFLIES OF THE DISTRICT OF COLUMBIA 47 



unless the puddle species are very common. Thus in the exception- 

 ally dry summer of 1930, when the numbers of all the butterflies 

 were greatly reduced, the muddy patches were entirely deserted — 

 not a single example of even the commonest of our puddle butterflies 

 was to be found on them. 



The true explanation of the puddle butterflies seems to be that 

 they are males from overpopulated areas in which they are inces- 

 santly tormented by other males and from which they escape to more 

 peaceful surroundings. Requiring water, they naturally resort to 

 the puddles about which, in the absence of females, they fail to de- 

 velop their usual pugnacity and instead become gregarious, flocking 

 with others of their kind or with males of several kinds until they 

 become fully mature, when they either return to the field from which 

 they were originally driven or, remaining more or less gregarious, 

 wander away. 



The appearance of the puddle butterflies is always evidence of 

 an excess in the number of individuals of the species concerned in 

 any given area. It is primarily evidence of a growing pressure of 

 population. 



Before leaving the subject of puddle butterflies it may be remarked 

 that very worn and battered females are occasionally, though very 

 rarely, observed about puddles. To these the males pay no attention. 

 Similarly worn and battered males are also occasionally seen. These 

 are always solitary and never show any inclination to join the groups 

 of younger males. 



Comparable in certain ways to the puddle butterflies are the road- 

 side butterflies. Our typical roadside butterflies are the pearl cres- 

 cent {Phyciodes tha7'0s), the buckeye (Jimonia lavinia), the vice- 

 roy {Basilarchia archippics) , the hop merchant {Polygonia cormna)^ 

 the question mark {P. interregationis) ^ the red admiral {Pyra7neis 

 atalanta), and the Camberwell beauty (Vanessa antiopa). 



The pearl crescent is almost as much of a puddle butterfly as it is 

 a roadside butterfly, but while very common about puddles it is by 

 no means so gregarious as the more typical yellow or bright-orange 

 puddle butterflies. All the other roadside butterflies are to be seen 

 more or less frequently about puddles and muddy spots, but always 

 as individuals and never in groups. 



Roadside butterflies first make their appearance in midsummer and 

 gradually increase in numbers until the end of the season. They 

 never appear among the individuals of spring or early-summer 

 broods. If for any reason the numbers of a species are reduced be- 

 low the normal, no individuals of that species will be found as road- 

 side butterflies. Thus in the summer of 1930, when all butterflies 

 were relatively scarce, it was noticed that roadside butterflies, which 



