10 PROCEEDINGS OF THE NATIONAL MUSEUM Vol. 68 



CYLINDROMYIA COMPRESSA. new species 



(Fig. 23) 



A small species of ordinary appearance, known only in the female, 

 and having very unusual egg-laying apparatus. Parafacials and 

 parafrontals silvery, the former a little wider than the third an- 

 tennal joint. Antennae black, rather small, the second joint con- 

 siderably more than half the third. Sternopleural two. Scutellum 

 with one large pair of bristles near the apex, between which in the 

 single specimen there is an apical bristle on one side but not on the 

 other. First and second abdominal segments red except the base of 

 first and a very little of the apex of the second above. The first 

 has only two lateral bristles, one near the base, the other near the 

 hind edge. No discals except a pair near the base on fourth seg- 

 ment. On the median line below the ends of the first principal 

 tergite seem to fuse together behind, and in this region bear about 

 20 distinct small spiny bristles on a slight swelling. In profile the 

 venter of the second segment is a little concave. The third and 

 following segments of abdomen are shining black. The third seg- 

 ment below with a median groove for the reception of the tip of 

 the last genital segment; this groove continues on the fourth seg- 

 ment where it is mostly filled up by a globose shining black median 

 sclerite; fifth segment contracted and tapering; sixth segment rather 

 long, compressed, curved, shining black, drawn out into a sharp 

 upturned point as viewed in profile; the point is composed of two 

 blade-like portions divided below for some distance and between 

 them the sharp sting projects. Front tarsi with a slight widening of 

 the last three joints. Wings with rather uniform smoky coloration, 

 more yellow in the costal cell and at base. 



Length, 7.G mm. 



Described from a single female specimen taken at Banff, Alberta, 

 by C. B. D. Garrett. 



Type in the Canadian National Collection. 



This species is most nearly related to dosiades, in which occa- 

 sionally the discals are partly absent. Whether compressa normally 

 has one pair of scutellars or two can not be decided from the single 

 specimen, in which the apical pair is represented only by a bristle 

 on one side. Both of these species have in the female a swollen, 

 spiny area on the venter of the first abdominal segment, not the 

 second as in signata and nana', they also have no hooks on the last 

 genital segment. There is no doubt of the distinctness of compressa 

 however, as the last genital segment is much more acute and com- 

 pressed than in dosmdes. 



The Eui'opean interrupta Meigen is very much like this species, as 

 I note from a female in the Canadian collection kindly sent me for 

 study. It has discal abdominal bristles however. 



