334 D1PTERA OF NORTH AMERICA. [PART II. 



{The lower part of the face, in the female, distinctly clothed with hair. 

 16 nigribarbus Lw. 

 The lower part of the face not hairy. 24 



„.( Antennae small. 17 parvicornis Lw. 



X Antennae rather large. 18 opacus Lw. 



„r ( Venter and posterior margin of the pleurae not yellow. 26 



(. Venter and posterior margin of the pleurae yellow. 27 



2 p ( Thorax shining, front white. 19 politus Lw. 



X Thorax rather dull, front gray. 20 debilis Lie. 



97 C Hypopygium very stout and large. 21 crassicauda Lw. 



X Hypopygium of ordinary thickness and size. 28 



2 q f Antennae very small. 22 minutus Lw. 



I Antennae of middle size. 23 ventralis Lw. 



19. G. politus Loew. % and 9. 



I have now obtained also the male of this species. The cres- 

 cent-shaped lamellae of the hypopygium are white-yellowish, their 

 interior appendages not penicillate. The dorsum of the thorax 

 is not quite so bright as that of the female, which otherwise it 

 resembles very much. 



24. O. pusillus, nov. sp. 2 . — Laete viridis, nitens, facie alba, coxis 



praeter apicem femoribusque nigris. 

 Bright green ; face white ; coxae, with the exception of the tip and the 



femora, black. 

 Long. corp. 0.10. Long. al. 0.11. 



Bright metallic-green, by no means black-green, shining. Front 

 with a not very conspicuous gray- whitish dust. Antennae black ; 

 the third joint not very small, with an almost imperceptible pu- 

 bescence. Coxae black, their second joint yellowish. Femora 

 black, the tip of the four anterior ones to a considerable extent 

 yellowish. Tibiae yellow. Tarsi at the basis yellow, from the 

 tip of the first joint blackened. (The hind tarsi are wanting.) 

 Wings with a brownish-gray tinge. 



Hab. Illinois. (Le Baron.) 



Observation. — A single female of this species is in my posses- 

 sion for some time ; but the rather imperfect condition of this 

 specimen, and the hope of obtaining better ones, induced me to 

 delay the publication of this species. As my hope has not been 

 fulfilled, I furnish its description now. It is easily distinguished 



