364 INSKCTA. 



Trixa, Meifj , 

 Where its length but little exceeds that of the second *. 



There the abdomen is sometimes strongly inflated, and, as if vesi- 

 cular, with the divisions of the annnli but slightly marked ; sometimes 

 it is much flattened. The wings in the last case are very distant, and 

 frequently somewhat arcuated exteriorly. 



Gymno£OMia Meig. — Tachina, Fah., 

 Where the abdomen is inflated, as if vesicular or ovoid, with the sepa- 

 ration of the annuli rather indistinct; the antennae are as long as the 

 face of the head, the second and third joints of almost equal length, 

 and the latter linear f- 



CiSTOGASTER, Lat., 



Where the form of the abdomen is the same; but the antennae are 

 much shorter, with the third joint longer than the preceding one, 

 almost square, somewhat larger, and rounded at the end \. 



Phasia, Meig. — Thereva, Fah., 

 Where the abdomen is strongly flattened, and almost semicircular ; 

 the tibiae are simply furnished with little hairs §. 



TRiCHiopot)A, Lat. — Tachina, Fah., 

 Where the abdomen is also flattened, but oblong, and the two pos- 

 terior tibiae are provided exteriorly with a fringe of lamelliform 

 cilia II . 



Sometimes the anterior face of the head presents two ranges of 

 long hairs, forming a sort of mustachios, two of which are usually 

 the longest, and situated at the superior extremity of the buccal ca- 

 vity, one on each side. 



in some, the wings are vibratile, and the abdomen is narrow, elon- 

 gated, almost cylindrical, or forming an elongated cone. They form 

 three subgenera. 



In the wings of the two first, as in those of the preceding ones, and 

 most of the others, the two external and closed cells of the poste- 

 rior extremity are almost equally prolonged backwards; the outer 

 one extends somewhat beyond the other, and its posterior angles are 

 acute. The antennce are as long as the face of the head, or hardly 

 shorter. 



LoposiA, Meig., 



Where the last joint of the antennas forms a very large triangular 

 palette^. 



OcYPTERA, Meig., Fab., 



Where the same joint of those organs, hardly wider than the penulti- 

 mate, resembles a linear palette, or one forming a long square. 



* Meigen. 

 f Idem. 



+ Confounded with the preceding subgenus, 



§ Lat., Geu. Crust, et Insect., IV, 344 ; see also Fab. and Meigen. 

 II The Thereva plumipes, ic.nipes, Fub., and various undescribed species, all from 

 America, 



^ iee Meigen. 



