THE TRIBE OF THE WHITES 89 



spring form is decidedly smaller and the markings are 

 much less distinct than in the summer form. 



The seasonal liistory of this species is comparatively 

 simple. In winter the chrysalids are found. From these 

 chrysalids in early spring the small butterflies of the spring 

 form come forth. These lay eggs upon various crucifer- 

 ous plants which hatch into greenish caterpillars that eat 

 the leaves and soon mature so far as their caterpillar stage 

 is concerned. They are then about an inch long, with 

 downy cyhndric bodies more or less marked with rather 

 pale yellow stripes, touched here and there with purplish 

 green or dotted slightly with fine black dots. These cater- 

 pillars now attach themselves by means of a button of silk 

 and a silken loop to some support like a piece of board, the 

 side of a stone, or almost any available shelter. Each 

 casts its larval skin and appears as a grayish chrysalis 

 from which probably a fortnight later the summer form 

 of the butterfly emerges. There are commonly two 

 broods of this summer form, making three sets of butter- 

 flies for the entire season. The caterpillars of the second 

 summer brood of butterflies go into the chrysalis stage in 

 autumn to remain throughout the winter. 



Some very interesting observations upon the sleeping 

 habits of this butterfly have been made in St. Louis by 

 Mr. and Mrs. Phil Rau. The insects were found abund- 

 antly resting upon the seed heads of white snakeroot. 

 Early in October, when a warm south wind was blowing, 

 the great majority of the butterflies slept horizontally 

 with their heads toward the wind. At other seasons and 

 in other places, many of them were found in a vertical 

 position but practically all had their bodies toward the 

 wind prevailing at the time. The observers were unable 



