246 TRANSACTIONS OF THE ILLINOIS 



scales sprinkled along their outer or costal border its whole length. At their tips is a 

 large triangular grayish-black spot, which is longer on the outer than on the hind side, 

 and on its inner side straightish, frequently with a concavity towards its inner end. In 

 the female this spot is larger, but effaced on its inner end, whereby it has more of a 

 squarish than a triangular form. Slightly beyond the center of these wings is a large black 

 dot or round spot, and between this and the inner edge, in the female, is a second spot, 

 which is usually smaller and less regular in form, with its edges more indefinite. And 

 in this sex is frequently a faint gray streak on the inner border of these wings, extend- 

 ing from opposite the inner spot forward towards the base. The hind wings in both 

 sexes have a black spot on the outer margin a little back of the middle, which is smaller 

 than those on the upper wings, and its edges indefinite. On the under side the fore 

 wings are white and sprinkled with black scales at the base and along the outer border 

 sometimes to the middle. Along the inner side of the rib vein towards the base is a 

 broad stain of yellow, more distinct in the females. The tips are pale yellow, and in 

 both sexes there are two black spots, corresponding with those on the upper side in the 

 females, but commonly smaller. The hind wings are pale yellow, and dusted over with 

 small black scales, which are more numerous towards the base ; the outer edge is bright 

 yellow near the base, and no vestiges of the black spot of the upper side are here visible 

 in either sex. 



Curtis' s description of the species, as observed in England, is as 

 follows : 



The male is white, the superior wings have black tips dusted with white, and the 

 inferior wings have a black spot on the upper edge ; the female is similar, but has two 

 large black spots likewise beyond the center of the superior wings ; under side of same 

 white, the apex yellow, and two black spots beyond the middle, the lower one some- 

 times nearly obliterated; inferior wings yellow, freckled with black; length of male, 

 eight lines; expanse, about two inches; the female is larger, and sometimes of a duller 

 color ; but I possess a male, taken near Oldham, in Lancashire, which has all the wings 

 of a bright-yellow color. 



The female butterfly deposits her eggs singly here and there, usually 

 upon the under side of the leaves, not in clusters as do some other species 

 of the same generic group; but she does not confine herself to this part 

 of the leaf, as the edge and upper side are often selected, especially when 

 the insects are abundant. To the natural eye they appear like little pale, 

 yellowish-green grains, being so small that they pass unnoticed unless the 

 attention is turned especially towards them. If examined by a magnify- 

 ing glass they will be found to be conical, or shaped like the old-fashioned 

 sugar loaf, the larger end or base of which is flat, being glued to the leaf; 

 the apex is also cut squarely off. Their surface is glossy and beautifully 

 fretted with alternating minute ribs and furrows; the ribs, of which 

 there are usually about twelve, run lengthwise, with intervening furrows; 

 it is also striated transversely with very fine impressed lines regularly 

 placed. The length is rather less than one-twentieth of an inch, the 

 thickness about one-fourth the length. 



The time required for the eggs to hatch varies somewhat, but is 

 u.sually about six or seven days. The little pale-yellow, glossy caterpillar, 

 which is less than one-tenth of an inch long when it first escapes through 

 the opening it has gnawed in the shell, not satisfied with release from 

 its prison, as the first act of its free life devours the shell. This habit 

 appears to have been first noticed by Harold, and is mentioned by West- 



