186 DIPTERA OF NORTH AMERICA. [PART II. 



The feet are sparely fringed with bristles ; the hind tarsi shorter 

 than the hind tibiae and their first joint without bristles. 



The genus Sympycnus stands in the closest proximity to Anep- 

 sius, is, however, very easily distinguished from it by the glabrous- 

 ness of the first joint of the antennae. Among the genera which 

 have no hair upon the first joint of the antennae, Xanthochlorus, 

 Teuchophorus and Campsicnemus are the next to it ; they differ 

 from Sympycnus by the following characters : 1. Xanthochlorus 

 by the depression on the posterior end of the thorax and the pre- 

 vailing yellow color of the body and of the bristles upon the 

 thorax ; 2. Teuchophorus by the steeper position of the posterior 

 transverse vein, the thickening of the costa in the male, the isolated 

 and strikingly strong bristles upon the feet and the entirely hidden 

 hypopygium ; 3. Campsicnemus by the elongated metathorax, by 

 the last segment of the fourth longitudinal vein, which is parallel 

 to the third and ends always beyond the tip of the wings and 

 by the face of the male, which is very narrowed upwards, &c. 



The name of the genus (from o^Ttrxi-oj, crowded together) has 

 reference to the crowding together of the ends of the fourth and 

 the third longitudinal veins, whereby Sympycnus is distinguished 

 from Campsicnemus and many other related genera. 



I am only acquainted with species from Europe, Africa and 

 North America; the majority of the North American species 

 differ from the European and from the South African species by 

 the fourth longitudinal vein ending exactly into the tip of the 

 wing, while in the other species, this end is distinctly before the 

 tip. As they agree in all other details of organization, there is 

 no ground for a generic separation, but it would be advisable to 

 form of them a group within the genus Sympycnus. The charac- 

 ter of the genus Sympycnus, as hitherto established, requires, with 

 regard to these species, a slight modification, which I have, already 

 introduced. 



Table for the determination of the Species. 



{Fourth longitudinal vein ending before the tip of the wing. 

 1 tertiarms, nov. sp. 

 Fourth longitudinal vein ending into the tip itself. 2 



( Antennae entirely black. 2 frontalis Lw. 



( Antennae pale near the basis. 3 



( Thorax with dark longitudinal lines. 3 lineatus Lw. 



\ Thorax without dark longitudinal lines. 4 nodatus Lw. 



