204 NORTH AMERICAN DIPTKRA. 



SUBGENERA OF ASII.US. 



a. Ovipositor laterally compressed. b 



Ovipositor conical. b 



b. Third antenna! joint unusually hairy*. . Anarmostus. 

 Third antennal joint not unusually hairy. . . . . c 



c. Face without gibbosity, narrow throughout, not at all carinate, 



the mystax composed of a few long hairs. Senoprosopis. 

 Face with gibbosity, or not unusually narrow. d 



d. Posterior border of the last ventral segment in the male more or 



less widened Machimus. 



Posterior border of the last ventral segment of the male not un- 

 usually widened. ........ e 



e. Legs prevailing shining yellow in color. Heligmoneura. 

 Legs prevailingly black, or light and opaque colored. . f 



f. Abdomen shining black above and below. Stilpnogaster. 

 Abdomen not shining black above and below. . . . g 



g. Male genitalia clubdike Neoitamus. 



Male genitalia not club-like; the sixth and seventh segments 



take no part in the formation of the female ovipositor. 



Tolmerus. 

 h. Abdominal segments with bristles before the incisures. 



Philonicus.t 

 Abdominal segments not with bristles before the incisures, i 



i. Bright-colored, larger species Asilus. 



Small, ashy gray species Rhadiurgus. 



and hard to define, and many of them are doubtfully entitled to recog- 

 nition. At the most, few if any of them are based upon«real generic 

 characters, and the names are only useful as aids in the determination 

 of the numerous forms. 



The groups Epitripttts, Lophonotus and NeoSristicus have also 

 been reported from Central America by Hellardi and Bigot, but there 

 is doubt as to their correct reference. 



* The only reported species of Anarmostus is from Brazil and Brit- 

 ish Honduras. It has the abdomen deep steel blue and black, the 

 wings deep steel blue (l6 mm.) 



t Loew. Linn. Knt. 144; Philodicus Loew, Dipt. f. S. Afr. p. 144. 



