180 DIPTERA OF NORTH AMERICA. [PART IV. 



/ Femora with a distinct brown band before the tip ; knob of the halteres 

 2 1 lemon yellow. 1 sulphurella 0. S. 



* Femora without brown band. 3 



o ( Antennae orange at the basis. 2 cognatella 0. S. 



X Antennae entirely black. 3 subcinerea 0. S. 



Description of the species. 



1. G. Slllplaiirella 0. S. % and 9 .— Sulphureo-fiava, fusco-varie- 

 gata ; antennis basi aurantiacis, in mare verticillis longis ; femoribus 

 annulo fusco ; cellula discoidali (in speciminibus typicis) clausa. 



Sulphur yellow, variegated with brown ; antenna? orange yellow at the 

 basis ; those of the male with long verticils ; femora with a brown 

 band ; discal cell (in normal specimens) closed. Long. corp. 0.2 — 0.25. 



Syn. Gonomyia sulphurella 0. Sacken, Proc. Ac. Nat. Sc. Phil. 1859, p. 230. 



Front and vertex sulphur yellow, infuscated in the middle ; 

 proboscis, palpi, and antennae brown ; basal joints of the latter 

 orange yellow ; flagellum of the male incrassated at the base and 

 slender beyond it, with long, feathery verticils ; that of the female 

 filiform with short verticils ; collare sulphur yellow ; mesonotum 

 light brown, yellow along the margins ; scutellum yellow with a 

 brown line in the middle ; metathorax yellowish, infuscated in the 

 middle ; pleurae yellow above ; a yellow stripe, margined with 

 brown, runs from the fore coxae backwards ; halteres yellow ; 

 knob lemon yellow; coxae pale yellow; femora slightly incras- 

 sated at the tip, with a yellow band beyond the middle and a 

 brown band near the tip, which is yellow ; anterior pair of femora 

 darker, their tip brown ; tibiae tawny, infuscated at the tip ; tarsi 

 fuscous. Abdomen of the male lemon yellow; base of the seg- 

 ments brown, genitals yellow ; abdomen of the female brownish ; 

 posterior margins of the segments yellow, genitals ferruginous. 

 Wings (Tab. II, fig. 2) slightly gray, pale at the base, stigma 

 pale ; origin of the praefurca a little posterior to the tip of the 

 auxiliary vein, strongly arcuated ; the remainder of the course 

 of the second vein is parallel to the first ; the distance between 

 the tips of the two branches of the second longitudinal vein is 

 nearly equal to the distance between the tip of the anterior 

 branch and that of the first longitudinal vein ; the inner ends of 

 the second submarginal, first posterior, discal, and fourth pos- 

 terior cells are nearly on one line ; the third vein is arcuated, 



