578 [December 



rarely that the leaves composing each gall show any traces of the peculiar, widely- 

 removed serratures which characterize the leaves of the willow on which they oc- 

 cur, their edges being almost invariably perfectly entire. The color of the galls 

 when recent, is the same as that of the recent leaves of the willow on which 

 they grow, but at the fall of the leaf they become reddish brown, and after 

 hanging on the twig more than one year, almost black. 



Described from 19 bunches of galls. Very comiuou near Rock 

 Island, Illinois.* The eggs that originate these galls must be laid from 

 the middle of April to the end of May, and by the middle of July the 

 galls have attained their full size. When the twig on which they grow 

 is at all small, it generally dies the next spring. 



Larva. — On July 31 the larva was already .03 — .10 inch long, and whitish hy- 

 aline witli opaque, white, curdy, bowel-like markings; breast-bone indistinct. 

 Out of 12 specimens examined Nov. 12, all had formed their cocoon *nd were 

 full-grown, being .10 — .20 inch long and .05 — .10 inch wide, of the usual oval 

 form, rarely elongate so as to be 3 or 4 times as long as wide, whitish or yellow- 

 ish subhyaline, with the same opaque-white markings ; breast-bone distinct, 

 dusky, robustly Y-shaped : the two prongs of the Y placed in front, basally 

 divaricating at an internal angle of about 45°, and tapering on their external 

 edge into a slender, acute thorn at tip, so that their external edges are nearly 

 parallel with each other. Ordinarily the three arms of the Y are subequal 

 in length, but occasionally the lower (or posterior) arm is shortened about 

 i. and occasionally the other two arms are similarly shortened. The lower ex- 

 tremity of the Y is generally squarely but obscurely truncate, but sometimes 

 the whole lower arm tapers gradually to a point from the bifurcation down- 

 wards. The cocoon is whitish-hyaline, delicately thin, scarcely larger than 

 the larva, and generally adlieres laterally and especially towards its base to a 

 fewof tlie innermost small leaves of the gall, its base being imbedded in a shal- 

 low, cup-like cavity at the tip of the globular stem from which the leaves of 

 the gall take their origin. In this cocoon the larva, as well as the pupa, is 

 always found with its head towards the tip of the gall. On Feb. 20 the larvse 

 were more generally and more deeply yellowish, the breast-bone darker, and 

 many of them had a broad, dorsal, dusky vitta on 3 or 4 of the middle joints. 

 One contained 15 parasitic larvae, showing plainly through its integument, in 

 the manner figured by Westwood Intr. II. p. 167, fig. 14, which I afterwards 

 squeezed out and counted, and April 19 I found a sim.ilar specimen containing 

 10 larvse. On Feb. 20 I also found a single Proctotrupide imago inside each one 

 of 11 or 12 cocoons, all very lively when disengaged from their own cocoon. On 

 March 29 I found nothing but larvte in very numerous galls which I opened, 

 and continued to lind very many larvae up to April 21, and for some time after- 

 wards. Those examined April 19 were more highly colored, being yellowish- 



*I found, March 16, on the tips of the twigs of young, stunted, wild plum- 

 trees, bunches of galls much resembling S. bransicoides, but with the cells all of 

 them em])ty. 



