42 COSTA RICAN DIPTERA 



11. Face opaque, wnth nose-like tubercle between antennal foveae; wings 



spotted Uythea 



Face shining, evenly convex, without nose-hke tubercle; wings not spotted, 

 hyaline Typopsilopa 



12. Face very short; mouth large, with margin anteriorly attaining the nose- 



hke tubercle between the foveae; opaque brown species with contrasting, 

 silvery pleura Brachydeutera 



Face large, prominent below, without tuberculous swelling; epistoma 

 scarcely retreating Napaea 



Face evenly convex or more or less tuberculate; epistoma generally re- 

 treating 13 



13. Abdomen broad, circular in outline; face with a median, prominent, semi- 



globose swelling; black, shining species Gastrops 



Abdomen ovate 14 



14. First three abdominal segments together not longer than fourth, with 



flattened depressed area on dorsum Lytogaster 



Abdomen normal 15 



15. All head and thoracic bristles reduced to setulae, or wanting; antennae 



retained in pit-like foveae. (Neotropical?) Mosillus 



At least vertical and scutellar bristles well developed 16 



16. Third antennal joint elongate, decumbent; spine weak or wanting. (South 



America and West Indies) Ceropsilopa* 



Third joint short, or, if elongate, spine well developed 17 



17. Facial bristles strong; third antennal joint lenticular 20 



Facial bristles strong; third antennal joint elongate 18 



Facial bristles hair-like; third joint short 22 



18. Face with two pau-s of bristles. (South America.) ? Clasiopella 



With only one pair 19 



19. Frons and face oblique, in same plane; face most prominent at epistoma. 



Plagiops 

 Frons and face convex in profile; epistoma retreating Psilopa 



20. Mesonotal setulae in distinct series 21 



Setulae scattered, not seriated Discocerina 



21. Third costal section at least equal in length to second; wings noticeably 



pointed at tip of third vein Atissiella 



Third costal section at most one-half as long as second; wings not pointed. 



Allotrichoma 



22. Face evenly sculptured in distinct transverse furrows. (South America.) 



Cerometopon Cresson' 

 Face at most minutely pitted on the facalia Ochtheroldea 



* Ceropsilopa Cresson. Described in Ent. News, xxviii, 340, 1917. 

 « Ent. News, xxv, 241, 1914. 



