RHOPALOMERnXflS HELOMYZID^. 125 



damp places. The known species are confined to Central and 

 South America. 



The group is evidently sharply divided into two minor 

 groups, by the presence or absence of the auxiliary vein and 

 the length of the first longitudinal vein. 



TABLE OF GENERA. 



1. Auxiliary vein wanting, the first longitudinal vein short; first posterior 



cell of the wings not narrowed ; palpi slender (Rhinotorince, Central 



and South America) RHINOTORA Schiner. 



Auxiliary vein well-developed, the first longitudinal vein longer; first 

 posterior cell much narrowed in the margin; palpi dilated (Rhopal- 

 omerina;). . . . . ", ... . . 2 



2. Scutellum oval ; arista plumose. ...'.' 3 



Scutellum pyramidal, directed obliquely upward ; arista plumose or 



bare (Central and South America). . RHOPALOMEHA Wiedemann. 



8. Front with bristles; face carinate; hind tibias dilated and with tubercles 



(Central and South America). . . . WILLISTONIELLA Mik. 



Front without bristles; face tuberculate; hind tibiae slender (S. Amer.) 



APOPHORHYNCHUS Williston. 



47. HELOMYZID^E. 



Face usually nearly perpendicular, with vibrissse ; front 

 bristly on the posterior half only; antennae short. Abdomen 

 rather broad and long, more or less flattened, composed of six 

 segments ; male genitalia somewhat prominent ; costa of the 

 wings bristly ; first longitudinal vein bare. Wings compara- 

 tively large ; all the basal cells distinct. Tibiae with spurs 

 and a preapical bristle. 



The larvae of Leria have been bred from bat and rabbit 

 dung; those of Helomyza from truffles, decaying wood, etc. 

 They are cylindrical, obtuse behind, more pointed in front ; 

 the antennae situated upon long, conical processes ; mouth 

 booklets large and pointed ; the seven abdominal segments 

 on each side in front widened, below with bristly pseudopods. 

 Many of the species of this family live in caves or burrows. 



