THE TRIBE OF THE YELLOWS 99 



of its range. For there is pretty good evidence that the 

 specimens seen in the Northern states are migrants from 

 the south, coming singly or in scattered flocks in early 

 summer, and if they lay eggs the butterflies of the new 

 generation return south in autumn. But the precise con- 

 ditions are not well known and need careful observations 

 in various localities. 



The life-story of a generation of these butterflies is much 

 like that of the other Yellows. The eggs are laid, one in a 

 place, on the leaflets of various species of wild senna 

 (Cassia) and soon hatch into cylindrical caterpillars that 

 devour the tender leaflets. In a few weeks the cater- 

 pillars mature and change to curious and characteristic 

 chrysalids. The head projects in the shape of a cone and 

 the back is so concave as to give the side view of the chrys- 

 alis a very striking appearance. 



Like so manj^ of the Yellows this butterfly is sun-loving 

 and social in its habits. Great numbers flock together, 

 their large size and bright coloring rendering them very 

 conspicuous. They often alight on the ground to sip 

 moisture when they have been likened to beds of yellow 

 crocuses. They also fly long distances in flocks that at- 

 tract much attention. It is likely that the northward dis- 

 tribution takes place in summer through such migrating 

 hosts. 



Other Sulphur Butterflies 



The Large Orange Sulphur is a closely related butter- 

 fly of about the same size, in which the coloring is uni- 

 formly orange-yellow instead of lemon-yellow. It also be- 

 longs to the tropics, occurring in our extreme Southern 

 states and ranging occasionally as far north as Nebraska. 



