CECIDOMYIA. 203 



the protruding portion of the breast-bone consisted of two trian- 

 gular projections with a triangular excision between them. 



28. C. strohilo'ides, n. sp. Terminal buds of the willow (the 

 species is not known to me) deformed in the shape of the cone of 

 a pine. This deformation, communicated to me by Mr. Rob. 

 Kennicott, who found them abundantly in northern Illinois, is an 

 inch or more long and contains several reddish larva? under each 

 scale, so that the total number of the larvas in one gall is very 

 considerable. A precisely similar gall has been observed by Mr. 

 Bremi on one of the European willows, and is figured in his mono- 

 graph (Denkschr. d. Schweitz. Ges. fiir Xafurk., Yol. VIII, tab. 

 II) under the name of Cer. strobilana. The perfect insect like- 

 wise remained unknown to him. 



29. C. cla-ysopsidis Lw. The gall (Tab. I, f. 1) occurs in Sep- 

 tember on Chrysopsis mariana and was communicated to me by 

 Prof. Schaeffer in Washington. Gall and fly are described by 

 Mr. Loew as follows : — 



" The gall consists of a woollen knob of nearly the form and 

 size of a very small walnut. On the sides there are single pro- 

 jecting leaves, which appear to have undergone no deformation ; 

 at the upper end the leaves of the extremity of the shoot seem to 

 be a little shortened. On removing the rather long hairs of the 

 knob, the interior may be observed to consist of a very great num- 

 ber of single galls, which have no compartments, and coalesce here 

 and there. Each of these galls has an obconical form, unless 

 modified in consequence of its coalescence with the neighboring 

 ones ; and it is covered exteriorly with hairs growing longer to- 

 wards the upper end, and resembling the pubescence on the stem 

 and leaves of the plant. In its interior there is a cylindrical 

 smooth cavity, which the perfect insect leaves through a small 

 round opening of the upper end. This opening apparently does 

 not exist during the larva-state of the insect, since together with 

 galls which were furnished with it, and had been abandoned by 

 the perfect insects, I found some which had no opening and con- 

 tained the imagos dead. 



" The small Gall-gnat which produces this deformation belongs 

 to the genus Gecidomyia in the restricted sense, and may be called 

 Cecidomyia chrysopsidis. " 



