INSEJCUTOR INSCITI.E MENSTRUUS 145 



and dense, yellow. Pleurae brown and black, thickly dusted 

 with gray ; mesopleurse with somewhat longer hairs than those 

 on mesonotum. Scutellum convex, broadly rounded, much 

 broader than long, shining, ocher yellow, rather evenly punc- 

 tured, with light yellow hairs and a few bristle-like ones on the 

 posterior margin. Abdomen much broader than thorax, 

 broadest at posterior margin of second segment ; color light yel- 

 low, more or less stained with dark by body contents ; second 

 segment more or less translucent. Coxae yellow. Anterior and 

 middle pairs of legs yellow, with white pile. Hind pair some- 

 what darker, the femora distally tinged with brown and with 

 minute black spines along ventral surface; tibiae tinged with 

 brown on distal half ; first tarsal joint grayish brown, paler 

 distally and ventrally. Wings hyaline, faintly smoky, without 

 trace of maculation, slightly darkened distally along anterior 

 margin ; stigma yellow. Halteres pale yellow. Length about 

 3.75-5 mm. ; wing 3.75-5 mm. 



Dead Run, Fairfax County, Virginia, May 23 and June 9, 

 1915. Six males (R. C. Shannon). 



Type, Cat. No. 19681, U. S. Nat. Mus. 



This species is very distinct from the other North American 

 species ; it is much smaller and different in general coloration. 

 From notata O. S. it is easily distinguishable by the short 

 scutellum and the clear wings ; the fourth vein is much less 

 sinuate and its last section shows very shallow angulations, 

 with very slight stumps in some specimens. The resemblance 

 with vacua O. S. is more close, but, aside from the lighter 

 coloration, the scutellum is shorter, the eyes more broadly 

 contiguous, and the third antennal joint more ovate. Perhaps the 

 resemblance is closest with media Will., known only from a 

 single female from California, which is now before me. This has 

 the mesonotum black, gray pruinose, only the humeri and 

 narrow lateral margins yellow, the pile whitish. The scutellum 

 is more prominent and flattened. The penultimate section of 

 the fourth vein is more sinuate, the last section without pro- 

 nounced angulations. All specimens were taken hovering near 

 a chestnut log on a hillside with a northern exposure. 



