28 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 83 



Thorax and scutellum black, o-ray pollinose ; mesonotum marked 

 with four bUick stripes in front and five behind suture, outer pair 

 stopping before base of scuteHum ; inf rasquamal hairs present^ 

 calypters ^Yhite. 



Abdomen black, all segments with gray pollen, which in some 

 views extends thinly past the middle of the last three ; basal segments 

 each with a pair of median marginals (smaller on the first) ; third 

 with a marginal row of 10 to 12 ; fourth bearing a complete row of 

 discals as large as those in the marginal roAV ; genital segments black, 

 I'etracted. 



Legs black, reddish near base; claws and pulvilli longer than 

 apical tarsal segment; hind tibia with a row of uneven wide-spaced 

 bristles on outer posterior edge. 



Wings with a brownish tinge on the anterior margin, small cross 

 vein inf uscated ; venation normal ; third vein setulose two-thirds the 

 distance to small cross vein ; apical cell open well before exact wing 

 tip ; epaulets blackish ; costal spine ordinary in size. 



Length. — 9 mm. 



Female. — Unknown. 



Type.— Male, U.S.N.M. no. 44765. 



Remarks. — Described from two male specimens in the United 

 States National Museum: One (the type) labeled Sanchez, Chi- 

 huahua, Mexico, September 2, 1909 (C. H. T. Townsend) ; the other, 

 Las Vegas, New Mexico, August 19, 1901 (H. S. Barber). 



The prominent front, more strongly receding face, longer and 

 broader third antennal segment, and haired parafacials readily sep- 

 arate the species from P. derelicta.^ to which it is closel}^ related. 

 Another difference is the presence of median marginals on the first 

 abdominal segment. 



(13) PARADIDYMA ARISTALIS, new species 



Arista densely pubescent; parafacial bristles uniform in length 

 downward, smaller than usual; sides of face cinereous, with black 

 hairs extending below middle outside of the main row of bristles; 

 mesonotum with four black stripes in front and five behind suture. 



Male. — Front at vertex 0.26 of the head width (one specimen), 

 rather prominent at antennae; paraf rentals cinereous pollinose to 

 vertex, rather sparsely clothed with short black hairs and consider- 

 ably widened before middle; median stripe reddish brown, slightly 

 narrowed behind ; inner verticals large ; ocellars proclinate ; orbitals 

 absent; frontals about six in the row, the lowermost nearly on level 

 with apex of second antennal segment; face receding, moderately 

 deep, and concave above the mouth; vibrissae large, on level with 

 oral margin ; facial ridges divergent downward, bearing a few bristly 



