PIERINAE; ANTIIOCIIARIS GENUTIA. 1151 



Food plants and habits of caterpillar. Tlie caterpillar feeds upon 

 Cruciferae of a .slender liabit. Schonborn obtained them about Washing- 

 ton on Sisyuibriiuu tlialiana (an introduced plant). I found tlic eggs in 

 Connecticut on Arabia perfoliata, and the caterpillars fed readily on Bar- 

 barea vulgaris ; Boll in Texas saw the female laying eggs on Cardamine, 

 and I obtained an egg, as stated, from a female confined on Capsella bursa 

 pastoris. "The young larva feeds on the flowers and buds, and as these 

 pass away, on the seed pods, usually beginning at the end of the long, 

 slender pod. and eating towards the stem" (Edwards). 



Pupation. The larva when changing to pupa constructs a long strand 

 of threads for a loop, which passes over the suture between the second and 

 third abdominal segments ; it then releases all hold excepting by the anal 

 prolegs, the others being well withdrawn and the whole body not only free 

 I)ut distant from the surface. Before changing, the wings can jje seen to 

 fill the second and third thoracic segments, from the normal point for a 

 spiracle straight down through the thickened part of the legs ; the veins 

 arise at the stigmatal point (that is, the point where a spiracle would be, 

 were there any on these segments) and reach through two joints of the 

 legs, that is to the equivalent of the whole proleg : in the front wing all 

 the branches of the subcostal and median veins can be traced, excepting 

 the first median nervide, and the relations of the median nervules to each 

 other and to the subcostal are seen to be wholly different from what they 

 are in the fully developed wings. The costal and subcostal nervures of 

 the hind wings can also be seen to be as in the fore wings, and the precostal 

 appears as an independent vein. 



In his last account of this butterfly Edwards gives the following 

 observations on the changes undei-gone by the caterpillar after maturity. 

 (Butt. X. Amer., Ser. iii, Pt. 6.) 



After the plant has gone to seed, Mr. Schonborn says it ntterly disappears, and the 

 larvae never pupate on the plants, but go to the trunks of the nearest trees and there 

 change in the cracks of the bark, or other protected places. The color of the pupa 

 is such that on an oak it would be almost undistinguishable. 



I kept my larvae on growing plants set in a flower-pot and covered by a muslin bag, 

 kept upright by sticks, and one morning chanced on a larva in the act of pupating, 

 almost done, while another was just about to begin. Both were attached by buttons 

 of white silk and by girdles to the same stick. The second one at this time was 

 curved from end to end, the head almost touching the stick. (See cut, 2.) Presently 

 it straightened itself and a creeping movement passed from tail to head in a way to 

 loosen the skin from the body, the larva con\-ulsively throwing itself against the 

 girdle, then to the support (3). These throes soon burst the skin at top, exposing the 

 head, over which the process was bent down, flattened and small (4). When the cast 

 reached the last segment it was thrown to the ground by a rapid twisting movement 

 of the pupa, and afterwards the same continued for nearly a minute, accompanied by 

 a vigorous pushing downward. This double motion fixed the hooks securely in the 

 button, which was forced into a cup shape, so that it quite sheathed the end of the 

 segment and afforded a firm support (7 magnified). I have not noticed this pecu- 

 liarity in the shape of the button in any other species. It would be useful, consider- 



