108 SMITHSONIAN INSTITUTION 



confined more or less strictly. Beyond those areas are seen only 

 occasional individuals, which in most forms are always males. Later 

 in the year, when the individuals are very numerous, both sexes 

 wander and become of general occurrence, though away from the 

 normal habitat, males are almost always much more numerous. 



In some species, as for instance in the cloudless sulphur (Catopsilia 

 scnncc), the males will flock together and go on exploring expeditions, 

 sometimes traversing large areas never visited by females. In others 

 the males will congregate on muddy spots where they may occasionally 

 be seen in enormous companies sucking up the moisture. This is espe- 

 cially the case with the yellow clover butterfly (Eitryniits philodice) , 

 the lesser sulphur (Eurciiia llsa), and the yellow (Papilio glaucns) and 

 white or zebra {Papilio profcsilaiis) swallowtails. These companies 

 of males sociably iml)il:)ing moisture suggest men's clubs in a city. 



In other species, as the pearl crescent (Phyciodcs tharos), the 

 buckeye {Junonia cocna), and the viceroy {Basilar chia archippus), the 

 males wander away and gather along roads or the borders of waste 

 places. Here they become excessively pugnacious. They attack each 

 other and dart viciously at bees, wasps, grasshoppers, and other insects 

 that fly near them. They cannot in any way harm these objects of 

 their spite, but they do their best to worry them. I have seen a male 

 pearl crescent by a furious onslaught on an immensely larger milk- 

 weed butterfly {Danaiis menippe) cause it to fly awkwardly from side 

 to side, at the same time rising in a desperate endeavor to shake off 

 its puny adversary. 



These belligerent male butterflies striving to prevent passage across 

 their lines into an overpopulated area are acting in defense of their 

 species' food supply. They show a curious correspondence to the 

 military lines drawn around human social units for the same purpose. 



While the males of most butterflies are more or less pugnacious, 

 their pugnacity rapidly increasing with increasing numbers, some 

 butterflies are pacifists and will not fight. This is the case, for instance, 

 with the milkweed butterfly {Danaus nicnippe). A very curious 

 characteristic of this insect is that the sexes seem to be alike in all 

 their habits, and when on the wing can only be distinguished by the 

 brighter color of the males. This butterfly is remarkable for its 

 autumnal migratory flights in enormous flocks which, unlike the so- 

 called migratory flights of many other butterflies, include both sexes. 



Comparatively little has been done on the more intricate details 

 of the natural history of the butterflies, and it is hoped by a continua- 

 tion of these studies to clear up many j^oints that now seem obscure. 



