361 



— Thorax with at least black discal marks; wings marked otherwise 



than as above 4 



4. Thorax and scutellum black 5 



— Ground color of thorax yellow, disc with black marks, scutellum 



yellow 6 



5. Setulose hairs on frons and cheeks black; Avings with very distinct 



infuscation, which extends to base and is most distinct in cell 



bounded by first vein and costa; legs entirely yellow (111.) 



pallkUpcs, n. sp. 



— Setulose hairs on frons and cheeks yellow ; wings with rather indis- 



tinct infuscation, which does not extend to base ; legs yellow, hind 

 femora and tibiffi largely black (111.) fumipennis Malloch. 



6. Sides of mesonotum near anterior angles with a white spot (111.) . . . 



splendidus Malloch. 



— Sides of mesonotum without a white spot (Mass.) 



ohscuripennis Johnson. 



7. Thorax and scutellum glossy black ; apical half of hind femora black, 



the remainder of legs yellow (La.) pilosulus Becker. 



— Either disc of mesonotum or the scutellum yellow ; legs not as above 



8 



8. Halteres yellow 9 



— Halteres black 11 



9. Scutellum black, disc of mesonotum yellow, with a posteriorly tri- 



dentate black mark which covers almost the entire disc (Pa., 111., 

 N. H. ) dorsalis Loew. 



— Scutellum yellow, with brownish marks upon the disc 10 



10. Disc of mesonotum with 3 confluent black vitta?, forming a large dis- 



cal mark, rarely narrowly separated ; scutellum with a basal black 

 mark on each side (N. H.) epliippium Zetterstedt. 



— Disc of mesonotum with 3 black spots, the rudiments of the normal 



vittffi, beyond middle; scutellum with a large brownish mark on 

 disc (111.) interrupius,n. sp. 



11. Legs entirely yellow or with only a faint brownish mark at apices of 



hind femora (N. H., Vt., 111.) montanus Coquillett. 



— Legs with distinct, deep black marks 12 



12. Thorax glossy black, lower half of pleurae and the scutellum yellow 



(111.) apicalis Malloch. 



Thorax and scutellum yellow, disc of the former with black marks 

 (Pa.) festivus Loew. 



Gaurax flavidulus, n. sp. 



Male. — Yellow, subopaque. Head yellow, ocellar region, inner 

 upper mouth-margin, and back of head black. Thorax yellow, a black 

 central spot on pleurae and a similarly colored transverse one on mid- 

 dle of postnotum. Abdomen yellow, infuscated on sides of first seg- 



