NORTH AMERICAN DIPTERA. 1 (il 



15. — Scutellum wholly hhu-k ,.. 



lo. 



Scutellum partly or wholly reddish, front tibise destitute of bristles, claws 



of front tarsi minute Ijl. adiiinbrala. 



16.— Tonientum of occiput white 2~ 



Tomentum of occiput wholly yellowish .>o 



17.-Proboscis projects one-fourth its length or more beyond the epistoma 18. 



Proboscis does not project beyond the epistoma 20. 



18.— First two antennal joints yellowish, the third sub.;lobular at its base ; front 



tibia", provided with bri.stles 29 



First two antennal joints black, the third conical at its base; front til)ia- 



destitute of bristles jg cai>rea. 



19. — Base of marginal cell hyaline, fourth alidomiual segment in tlie male shin- 

 ing tomentose 21. ao-roMtiK. 



Base of marginal cell brown, fourth abdominal segment in both .sexes desti- 

 tute of shining tomentum 20. lauta. 



20.— Tomentum of venter partly or wholly white or yellowish, claws of front 



tarsi small q, 



Tomentum of venter wholly black, claws of front tarsi large, legs black. 



14. aiiiia. 

 21.— Legs reddish, tomentum of apical half of venter yellowish, abdomen desti- 

 tute of black tomentum. brown clouds on veins at bases of third and 



fourth posterior cells 17. eiidora. 



Legs black, tomentum of apical half of venter black, apices of third and 

 fourth abdominal .segments black tomentose, no l)rown clouds, etc. 



1'). isiiipiiia. 

 22.— Base of fourth abdominal segments destitute of a crossband of black to- 

 mentum .f^ 



Base of front abdominal segment with a crossband of bhu'k tonientum, 



venter and breast yellowish tomentose and pilo.se. ...22. <*aiiipc>««ti'is. 



~3. — Venter and breast yellowish tomentose and pilose, abdomen destitute of 



black tomentum o-l 



Venter and breast wholly black tomentose and ]nU»ic. abdomen with Mack 



tomentum .....16. iiiopN. 



24.— Base of third antennal joint subglobular ; length of body 4-.s mni. 



1!). iiiaiirjif IIS. 

 Base of third antennal joint elongate-conical ; length of body 9 12 mm. 



33. edititia. 



25.— Pile and tomentum of head and abdomen partly white or yellowish 26. 



Pile aud tomentum of head and al)domen wholly black, base of wing to tip 



of di.scal cell blackish, the apex hyaline 23. atrala. 



26. — Scutellum partly or wholly reddish 27. 



Scutellum wholly black 3g 



27.— Apex of wings beyond base of second snbmarginal cell distinctly hj-aline 



and brown 28. 



Apex of wings beyond base of second snbmarginal cell either wholly hya- 

 line, wholly gray or wholly brown 31. 



28.— Third posterior cell divided by a crossvein into two cells, a stump of a 

 vein projects into the second cell from the great crossvein. 



50. Iialc^on. 

 Third posterior cell never divided into two cells 29. 



TRANS. AMEK. KXT. SOC. XIV. (21) OCTOBEK. 1887. 



