112 ' NORTH AMERICAN DIPTERA. 



WETATRICHIA Coq. 



In general form similar to Scenopmus, robust, mostly black ; but 

 the thorax is more arched above ; the scutellum is not separated from 

 the thorax by a distinct wide suture, and its apex depressed, forming 

 an unbroken curve with the thorax when seen in profile; entirely 

 clothed, excepting the dorsum, of abdomen, with scale-like hairs, which 

 on closer observation are elongated bulbs inserted on short stalks, 

 giving the insect a whitish appearance. The first posterior cell 

 closed and petiolate. 



.YIetatrichia biilbosns O. S., PI. II, figs. 3 aud 4. 

 Scenopinns O. S., West. Dipt., 275, 1877. 



This species is very well described by Osten Sacken. Tiiree 

 males and two females from Alamogordo, New Mexico (Viereck 

 aud Rehu), differ from the typical description in that the head and 

 thorax do not seem to have that blackish-bronze color ; the scales 

 ai"e all clear white ; the costal cell is not brown ; and the distance 

 between the two cross- veins is not shorter than the posterior cross - 

 vein. 



PSEUDATRICHIA O. S. 



The species of this genus, as far as I have seen, are of an entirely 

 different shape from those of the other two genera, and seems to 

 form a distinct group in themselves by their slender, elongated bodies 

 and legs. 



The following characters are typical for our present species, and 

 as to our present knowledge of the genus : slender, elongate species ; 

 thorax longer than broad, slightly arched above ; scutellum rather 

 prominent, but not large; abdomen narrow, cylindrical, not fiat; 

 legs slender, elongated ; wings narrow in proportion to their length, 

 first posterior cell closed and petiolate. 



TABLE OF SPECIES. 



1. Scutellum yellow, or brownish in middle 2. 



Scutellum entirely black 3. 



2. Abdomen and head black longiirio Lw., 'J, . 



Abdomen and head yellowish, in fact, the entire insect generally brown or 



yellowish '. griseola Coq., % , ^ . 



3. Abdominal dorsum shining, more or less pilose 4. 



Abdominal dorsum, at least in part, semi-opaque ; tiie segments more or less 



dilated at their posterior margins; head as long or longer than high. 



uiiicolor Coq., % , <$ . 



