III. 



ON THE NORTH AMERICAN SCIOMYZID.E. 



. The family Sciomyzidce is principally based on the three genera: 

 Sciomyza Fall., Tetanocera Dura, and Sepedon Latr., all occurring 

 in North America, and on the genus Thecomyia Perty. 



The attempt to subdivide the second of these genera has been 

 made in various ways, but without success. I omit, therefore, to 

 mention the genera thus formed, especially on account of the 

 scantiness of my materials. 



Sciomyza has been also subdivided into smaller genera, namely: 

 Graphomyza Macq., Pelidnoptera Rond., Ctemdus Rond. and 

 Calobaea Zett., the last of which, differing from all the other Scio- 

 myzidce by its much smaller basal cells, may be considered as an 

 osculant genus. Some of the species placed by Meigen in Scio- 

 myza belong neither to that genus nor to the Sciomyzidce at all. 



The characters distinguishing the Sciomyzidce from all the other 

 Acalyptera are as follows. The anterior frontal border more or 

 less prominent ; face receding, proportionately long, with the oral 

 border sharp ; no distinct furrows for the reception of the anten- 

 na? ; no vibrissa? on the oral border ; the front with two bristles, 

 one behind the other on each side before the lateral bristles of the 

 vertex; the costal vein of the wings uninterrupted, without spine, 

 reaching to the fourth longitudinal vein ; the auxiliary vein dis- 

 tinctly separated from the first longitudinal vein on its whole 

 length ; the two basal cells much developed, rather large, smaller 

 only in the osculant genus Calobaea Zett. The legs have short 

 hairs and very few bristles, and are of moderate length and rather 

 stout, but not clumsy ; all the anterior legs, especially their tibia? 

 and tarsi, are more developed than in the allied families ; all the 

 tibia? on their outside before the tips have a small, erect, more or 

 less distinct bristle ; the intermediate tibia? have a certain number 

 of stout bristles at the tip ; the fore and hind tibia? have a single 

 weak bristle. 



