32 On JJipterafrom Vera Cruz. 



Lvowiiisli or pale. Claws and pulvilli elongate. Tegulee 

 large, translucent sraoky-yellowisli, halteres yellow. 



? . Differs in front being about one fourth width of head, 

 frontal stripe and orbital margins in consequence narrower, 

 the silvery of orbits with less of a golden sheen ; wings not 

 so broadened or large, evenly fuscous hyaline, without patch 

 of dark fuscous on costa. Abdomen without purplish reflec- 

 tion, shining black or with slight greenish reflection, the 

 brassy-ashy pollen much more conspicuous, forming more or 

 less distinctly a pair of triangular spots on anterior part of 

 second, third, and fourth segments, leaving the median vitta 

 apparent. The pollen varies in its intensity and shade of 

 brassy. It is, together with the thoracic vittaj, sometimes 

 obscure and indistinct in both sexes. Foot-claws and pulvilli 

 moderately short, about as long as last tarsal joint. 



Although these two forms (male and female) are in general 

 facies so different, the fact that they were all taken together 

 over the ants, without a single specimen of any other Hyalo- 

 onyia being present, one series being all males while the other 

 is all females, convinces me that they are the two sexes of 

 one species. 



It seems probable, from the circumstances under which this 

 Hyalomyia was found, that it also, as well as the Stylogasters, 

 is parasitic on ants (genus Ecitpn). In all my collecting 

 in this locality, I met with no other specimens of Hyalomyia 

 than the above^ excepting only the single specimen next 

 described. 



35. Hyalomyia violascens^ sp. n. 



One male, San Rafael, June 26. 



Length 4^ millim. 



Belongs in the group with punctigera, Towns., purimr- 

 ascens, Towns., &c., in which the front is trigonal, the eyes 

 of male moderately or closely approximated, and those of 

 female nearly or quite contiguous. Differs from my de- 

 scription oi pu7-2mrascens, (J (Pr. Ent. Soc. Wash. ii. p. 137), 

 as follows: — Orbits silvery pollinose, face subsilvery ; eyes 

 closely approximated in front of ocelli, nearly obliterating the 

 narrow brownish frontal vitta, which is thus elongate- 

 triangular in front and narrowed to a line behind. Frontal 

 bristles weak. Antennse black, third joint oval, a little 

 longer and wider than first, silvery in some lights. Palpi 

 very small, filiform, brownish. Thorax silvery only on 

 humeri and pleurse. The apical pair of scutellar bristles 

 decussate. Abdomen wholly very polished deep violet- 

 black, reticulations of the ashy pollen showing faintly in 



