AMERICAN DIPTERA. 277 



bristles are small and indistinct ; the head is larger in pro- 

 portion than in the other genera. Of the specimens ex- 

 amined the eyes of all the males are in contact, unless other- 

 wise mentioned, and the femora have flexor spines, although 

 these are sometimes so minute as to be scarcely discernable 

 under high magnification. The cleft of the hypopygium is 

 understood to be on the right unless otherwise noted. 



A knowledge of the life history of this group of insects 

 would be a great help in the study, and it is only by breed- 

 ing that many of the species can best be procured, as Mr. 

 Perkins* has already done with his Australian and Hawaiian 

 species. They are known to be parasitic on Homoptera. 



TABLE OF SPECIES. 



Males 1. 



Females 35 . 



1. Stigma colored, generally long and conspicuous 2. 



Stigma hyaline, or very small 26. 



2. Fourth vein beyond post-cross vein with fork (Fig. 137) 3. 



Fourth vein normal 5. 



3. Antennas long, white acuminate 18. appendiculatus n. sp. 



Antennas obtusely pointed 4. 



4. Femora yellow; mesonotum only microscopically pubescent. North 



Carolina species 31. COnstricttlS Banks, n. sp. 



Femora more or less blackened medianly; mesonotum distinctly 

 pilose. Mexican species 17. elegantulus Will. 



5. Humeri brown or black 6. 



Humeri yellow or white 18. 



6. Legs entirely yellow; knobs of halteres black. 



16. atlanticus Hough. 

 At least all femora with distinct black rings 7. 



7. Hypopygium cleft 8. 



Hypopygium not cleft. 



Antennas yellow 5. ? flavitarsis Will. 



Antennas black 17. 



8. Hypopygium smaller than fifth segment, generally only a little 



visible, with apical cleft 9. 



Hypopygium as large, or larger than fifth segment and generally 

 assy metrical 11. 



9. Halteres black or brown 12. 



Halteres white or yellow 10. 



* Rept. Exp. Sta. Hawaii. Sugar Plant. Ass., Div. Ent., Bull. No. 

 1, pt. 4, 1905. 



TRANS. AM. ENT. SOC, XXXVI. DECEMBER, 1910. 



