78 DIPTERA OP NORTH AMERICA. [PART II. 



K f Tip of the hind femora blackish. 6 exilis Lu\ 



I Tip of the hind femora not blackish. 7 



,_ f Thorax dark violet. 8 



\ Thorax not violet. 9 



( Coxae up to the tip somewhat blackish. 7 spectabilis Liv. 



\ Coxae yellowish-white. 8 albiceps Lw. 



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



Fore coxae entirely yellow, or at the utmost somewhat ini'uscated near 

 the base. 10 



r Hind tarsi from the tip of the first joint black. 10 lasvigatus Lw. 

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

 I never black. 11 



, , f Antennae entirely black. 12 



\ Antennae partly red. 16 



1 f Lamellae of the hypopygium black. 1 1 frequens Lw. 



I Lamellae of the hypopygium not black. 13 



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



X Lamellae of the hypopygium white. 14 



f Interior appendages of the hypopygium penicillate. 

 14] 13 fimbriatus Lw. 



( Interior appendages of the hypopygium not penicillate. 15 



f Third and fourth longitudinal veins but slightly converging. 



14 despicatus Lw. 



Third and fourth longitudinal veins altogether parallel. 

 [ 15 difficilis Lw. 



1 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 



, - ( Lower part of the face of the <j? distinctly hairy. 16 nigribarbus Lw. 



\ The lower part of the face not hairy. 18 



lg f Antennae small. 17 parvicornis Lw. 



\ Antennae of tolerable size. 18 opacus Lw. 



, Q f Venter and posterior margin of the pleurae not yellow. 20 



I Venter and posterior margin of the pleurae yellow. 21 



20 ( Thorax brightly shining, front white. 19 poljtus Lw. 



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



01 / Hypopygium remarkably stout and large. 21 crassicauda Lw. 



I Hypopygium of the usual size and thickness. 22 



22 / Antennae very small. 22 minutus Lw. 



t Antennae of middle size. 23 ventralis Lw. 



15 



