264 DIPTERA FROM SOUTHWESTERN UNITED STATES 



Subfamily Phaoniinae 

 The species included in the subfamily as herein limited possess 

 the following characters: Sixth vein not extending to margin of 

 wing; hind tarsus without spine at base on ventral surface, except 

 in a few species of Pogonnniyia scutellum bare below; sterno- 

 pleura with bristles 2:2, or 1:2, if the latter they are not in an 

 equilateral triangle; propleura bare below humerus; calyptra 

 unequal, the lower always larger than the upper. 



Key to Genera Here Treated and Their Nearest Allies 



1. Fourth vein curved forward at apex 2 



Fourth vein straight or almost so, never distinctly curvei forward at 



apex 5 



2. Third vein bare at base; metathoric spiracle with several long bristles 

 along the lower margin which are difficult to see owing to their lying close 



against the covering of (he spiracle Muscina R.-D. 



Third vein bristled at base; metathoracic spiracle without such l)ristles. .3 



3. Prothoracic i)late between the fore coxae with l^ristly hairs on its lateral 



margins; arista pubescent or bare Limnophora R.-D., pt. 



Prothoracic plate between the fore coxae bare 4 



4. Arista plumose; eyes in male narrowly separated above Myiospila R.-D. 

 Arista bare; eyesof male widely separated above. . Bucephalomyia gen. n. 



6. Eyes of male separated Iw at least one-third the width of the head; arista 

 in both sexes bare, much thickened to or nearly to middle; apical seg- 

 ment of abdomen in female with four stout curved tliorns; anterior 

 orbital bristles below level of ba.se of antennae. . . . Tetramerinx Berg 

 Eyes of male separated by le.ss than one-third the width of head, or the 

 species have not all the above characters 6 



6. Hind tibia with one long, outstanding bristle beyond middle on the pos- 



tero-dorsal surface, rarely with a few additional smaller setulae basad 

 of the bristle; hind co.xae bare on po.sterior margin above. 



Phaonia R.-D. 



Hind tibia entirely without bristles on postero-dorsal .surface 7 



Hind tibia with a number of bristles on postero-dorsal surface which are 

 of almost equal lengths, or with one to two small setulae near base, if 

 with one long bristle beyond middle the hind coxae have bristly hairs 

 on posterior margin above 11 



7. Third vein bristly at base Mydaea R.-D. 



Third vein bare at base 3 



8. Hind coxae with bristly hairs at apices above TrichopticusRond., pt. 



Hind coxae bare above at apices 9 



9. Eyes of male flattened above, the facets on the flattened ijart about five 



times as large as those on the lower half; fifth abdominal sternite with 

 very large, deep U-shaped incision in posterior margin; genitalia of 

 female without paired projecting processes (figs. 1 and 2). 



Xenaricia gen. n. 



