1913] North American Dipterous Genus Neurigona 29 



Note. — The females of the five following species which have 

 the dorsum of the thorax yellow, and the flattened space before 

 the scutellum black can be separated as follows: nitida differs 

 from the other four by having a central shining black line on 

 the dorsum; carbonifer has the front metatarsi only three- 

 fourths as long as their tibias, while in dimidiata, rubella, and 

 perplexa, the front metatarsi are nearly equal to their tibiae; 

 in dimidiata it is fully as long, and in the others hardly as long 

 as their tibias, dimidiata has the first and second joints of the 

 hind tarsi equal, while in the other two the second joint is 

 distinctly the longest, in the last two the bend in the last sec- 

 tion of the fourth vein is sharper, and the tarsi are darker than 

 in dimidiata; the only difference between the females of rubella 

 and perplexa that I can see is that in rubella the posterior cross- 

 vein is rectangular while in perplexa it is a little oblique, but it 

 is difficult to separate them. 



I have compared the female of the European species N. 

 quadrifasciata Fab. which is the type species of the genus, and 

 closely related to this group, and find that it differs from all of 

 our five species mentioned above, by having the third and 

 fourth veins more widely separated at the tips, the fourth vein 

 ending in the apex of the wing, while in our species the fourth 

 vein ends distinctly before the apex of the wing. Fig. 28 is the 

 apical part of the wing of quadrifasciata Fab. 



I have also examined N. suturalis Fall, of Europe, and find 

 it quite distinct from any of our species. 



2 Neurigona perplexa n. sp. 



Figure 2. 



Thorax and abdomen yellow, the former with the flattened space 

 before the scutellum black, and the latter with black bands; hypopygium 

 black, small. Hairs and bristles of the front coxae whitish; front 

 metatarsi about the length of their tibias. Length 4>4 mm. 



Male : Face very narrow, eyes almost touching on the center of the 

 face, leaving only a small triangle above and below, face and palpi 

 silvery white; proboscis and antennee yellow, arista brownish; front 

 and occiput black, covered with white pollen; frontal and post-vertical 

 bristles black; orbital cilia whitish. Thorax yellow; the humeri and 

 lateral edges of the dorsum whitish yellow; flattened space before the 

 scutellimi black, with white pollen; a dark central line on the dorsum 

 between the acrostichal bristles, reaching from the black flattened space 

 to the front of the dorsum (this may not be found in all specimens) ; 

 pleurcB pale yellow, with white pollen, and the usual black spot in front 

 of the halters; scutellum yellow with a black spot at base; bristles of 



