18 PROCEEDINGS OF TKE NATIONAL MUSEUM vol. 70 



Walker ' erected the genus Uhristes for one of the species ^Yhich he 

 described as flavitihia, and it is here proposed to use this name in 

 the subgeneric sense for this group of species. 



Subgenus Ubristes Walker. 

 Uhristes Walker, Insecta Saunders, Dipt. vol. 1. 1852, p. 217. 



Genotyiie. — UhHstes favitibla Walker. 



A group remarkable for its similarity in appearance to the sting- 

 less honey bees, of the genus Tngona. Rather small and compact, 

 ranging in color from entirely black to almost entirely yellow; 

 face usually narrow; third longitudinal vein with or without an 

 appendix; abdomen broad basally, usually contracting apically; 

 hind legs usually hairy ; eyes thinly and shortly pilose. 



Walker described only the one species, favifihia, although the 

 other species here recorded (from the British Museum) were evi- 

 dently before him at the time. As far as I am aware the other 

 species are all new and are here described. 



Two species, Microdon v)heeleri Mann and M. 7riicromidas Shan- 

 non described from Panama, also belong to this group. 



KKY TO BUAZILIAN SPKCIES OF THK STTBr.Kvrt; T'RT!IRTF,S 



1. Thorax and abdomen entirely black 2 



More or less j'ellow present ' 4 



2. Abdomen ".spindle shaped," very slightly narrowed beyond the middle; 



fairly large species, 10 mm. ; legs very hairy flavitibia Walker. 



Abdomen tapering toward the apex to a blunt poinl ; rather small 

 siieeies, 7 mm. ; legs moderately hairy 3 



3. Three visible abdominal segments; wing with preapical wlilte stripe. 



lacteipennis, new species. 

 Four visible .segments, the fourth distinctly longer than the third; wings 

 uniformly infuscated trigoniformis, new species. 



4. Abdomen ovate with two pairs of large yellow spots; scutellum produced 



into a point, triangular in shape scutellaris, new species. 



Abdomen constricted behind spnniid tergite; scutellum rounded on hind 

 margin 5 



5. Third vein with an appendix, wing uniformly infuscated. 



fraiidator, new species. 

 Third vein without an appendix, a brnnd, whitish preapical crossband 

 on wing ,__i.^___^ goettei, new species. 



MICRODON (UBRISTES) LACTEIPENNIS. new species 



31ale. — A rather small, blacki.sh species, with eyes fairly approxi- 

 mated above antennae; ocelli closely grouped and centrally placed 

 upon the upper portion of front (=ocellar) triangle; first antennal 

 joint about twice as long as broad, second equals one-half length 

 of first, and the third is twice as long as the first; face black, 

 narrowly yelloAvish on sides next to border of eyes; face narrow, 



3 Insect:' SannflfTs, Dipt., vol 1, 1S'>2, p. 217. 



