AMERICAN DIPTERA. 285 



Several specimens, Brookings, S. D., and New Bedford, Mass., 

 the latter from Dr. Hough. 



This species is almost identical with inermis Loew, except that 

 the male has yellow femora, like the female. 



ACJONOSOMA. 



Guerin-Meiievelle, Voyage sur la Cowette, 1838, 293. 

 Aldrich, Kans. Univ. Quart., II, 48, 1893 (Gnamptopsilopus) ; Can. Eut., Aug., 



1904, 246. 



TABLE OF NORTH AMERICAN SPECIES. 



1. Autennse entirely black 2. 



At least the basal joints yellow 6. 



2. Femora yellow 3. 



Femora black 5. 



3. Fore coxae with black bristles at tip (Mex.) InfiiinatJini Aldrich. 



Fore coxse with pale bristles at the tip 4. 



4. Base of hind coxse and hind margiu of pleura pale (U. S.). -COStRlis n. sp. 

 Base of hind coxai and bind margin of pleura dark (U. S.). 



j^cintillans Loew. 



5. Wings without black markings (Mex.) ciliipeiinis Aldrich. 



Wings black, except apex and hind margin (Mex.). .diiuitliatiiiii Loew. 



6. Dorsum of thorax yellow, with a green or blue stripe 7. 



Dorsum of thorax wholly metallic 8. 



7. Pleura yellow; middle tibia- and metatarsi with eiect cilia (W. I.). 



navidtiiii Aldrich. 

 Pleura with an indistinct dark spot; tarsi plain (W. I.), .dorsale Loew. 



8. Thoracic dorsum opaque, dusted; abdomen not pale at base (U. S.). 



pal lens Loew. 

 Thoracic dorsum shining, abdomen usually pale at base 9. 



9. Middle coxse infnscated on outer side at least to middle ....10. 



Middle coxje wholly or almost wholly yellow 13. 



10. Costa of male ciliated, with an angular projection forward near the tip ( U. S.). 



pMittaciniiiii Loew. 

 Costa of male without such projection 11. 



11. Middle femora of male shortened, dark at base, the tibise elongate (U. 8.). 



filipeK Loew. 

 Middle femora of male normal, pale 12. 



12. Abdomen pale at base above (U. S., Cuba) vai'ies;Htuni Loew. 



Abdomen not pale at base above (Cuba) Cast mil Loew. 



13. Fore femora with slender erect bristles below (U. S.) leiier Loew. 



Fore femora not with such bristles- . 14. 



14. Hind margin of pleura yellow 15 



Hind margin of pleura green (Mex.) luexicanuiii Aldrich. 



15. Abdomen above with basal yellow band, remainder green (U. S.). 



{hicolor Loew) uiiifasciatuiii Say. 



Abdomen with several bands, including the greater part of first four se''- 



ments (U. S.) rotuiicliceps n. sp. 



TRANS. AM. KNT. SOC. XXX. NOVEMBICK. 1904. 



