78 DIPTERA OF NORTH AMERICA. [PART II. 



» f Tip of the hind femora blackish. 6 exilis Lw. 



\ Tip of the hind femora not blackish. 7 



h f Thorax dark violet. 8 



I Thorax not violet. 9 



g f Coxse up to the tip somewhat blackish. 7 spectabilis Lw. 



( Coxse yellowish-white. 8 albiceps Lw. 



{Fore coxse up to the tip blackish. 9 subdilatatus Lw. 



Fore coxae entirely yellow, or at the utmost somewhat infuscated near 

 the base. 10 



SHind tarsi from the tip of the first joint black. 10 laevigatus Lw. 

 Hind tarsi towards the tip but little dusky, at the utmost brownish, 

 never black. 11 



.,, f Antennae entirely black. 12 



I Antennae partly red. 16 



,2 f Lamellae of the hypopygium black. 11 frequens Lw. 



I Lamellae of the hypopygium not black. 13 



, o f Lamellae of the hypopygium dark yellow. 12 lunifer Lw. 



I Lamellae of the hypopygium white. 14 



(Interior appendages of the hypopygium penicillate. 

 13 fimbriatus Lw. 

 Interior appendages of the hypopygium not penicillate. 15 



f Third and fourth longitudinal veins but slightly converging. 

 -■ c J 14 despicatus Lw. 



I Third and fourth longitudinal veins altogether parallel. 

 I 15 difficilis Lw. 



{Middle and hind coxae from the basis distinctly blackish. 17 



Middle and hind coxae yellow, or, at the utmost, the former with a 

 grayish tinge. 19 



jw f Lower part of the face of the £ distinctly hairy. 16 nigribarbus Lw. 



I The lower part of the face not hairy. 18 



,gf Antennae small. 17 parvicornis Lw. 



I Antennae of tolerable size. 18 opacus Lw. 



.. q j Venter and posterior margin of the pleurae not yellow. 20 



«• Venter and posterior margin of the pleurae yellow. 21 



2q $ Thorax brightly shining, front white. 19 politus Lw. 



I Thorax rather dull, front gray. 20 debilis Lw. 



n-i f Hypopygium remarkably stout and large. . 21 crassicauda Lw. 



«- Hypopygium of the usual size and thickness. 22 



oo / Antennae very small. 22 minutus Lw. 



\ Antennae of middle size. 23 ventralis Lw. 



