84 



OHIO BIOLOGICAL SURVEY 



3 Wings cinereous hyaline, without distinct dark markings; abdomen very 



sknder cognata 



Wings more or less brownish or blackish 4 



4 Wings with a broad median cross- band, reaching to ihe fourth posterior cell; 



scutellum and posterior part of the dorsum shining golden fascipennis 



Wings with the front border, at least, for its whole length brownish or 



blackish 5 



Wings with front border narrowly darkened but not for its full length; body 



black, the first second and third abdominal segments with an oblique white 



spot on each side at base *costata Say ( Ind. ) 



5 Posterior half of the wings nearly hyaline tarchetius 



Wings more or less brown or blackish on the posterior part 6 



6 Wings subcinerescent; all the veins, except the last segment of the fourth 



broadely clouded with blackish, confluent near the costa 



*lugens (Loew N. Y. Wise, N. J., Fla.) 



Wings with a triangular hyaline space behind the outer end of third vein, the 

 axillary portion more or less subhyaline. Ocyptaiuns fitscipi-niiis Say, See 

 Ocyptamus (below) fuscipennis 



24 B. fascipennis Wied. Three males, fotir females, Sandusky, Cin- 

 cinnati, Ira, Hinckley, Wauseon; last of May to early September. 



25 B. clavata Fal^r. Two Ohio specimens, male and female, November 



2. (Fig. 217.) 



26 B. cognata Loew. A small delicate species. One female. Ira, 



September 8. 



27 B. tarchetius Walker. Two males, one female, Sandtisky, Medina, 

 Hocking Co. (Fttlton); Early July to early August. 



Ocyptamus Macquart 

 28 O. fuscipennis Say. Common: Sandusky, Medina, Ira, Lake- 

 ville, Hinckley, Lochbourne; July i to September 9. (Fig. 224.) 



Platychirus St. Fargeau and Serville. 



1 Front tibiae in the male gradually dilated from the base, the tarsi gradually 



decreasing in width from the base to the tip; profile of the face only gently 



concave above the tubercle, the latter small; cheeks convex below 2 



Front tibiae of the male slender, suddenly dilated at the tip, metatarsi much 

 dilated, the remaining joints but slightly so; the front femora in the 

 male with a thick row of hairy pile on the posterior side; face in both 

 sexes with a conspicuous tubercle; cheeks concave below peltatus 



2 Front tibiae of the male, on the inner side toward the end, somewhat concave 



the outer angle produced into a lappet- like process, yellow spots on the 

 abdomen in both sexes very large, leaving only a median stripe and cross- 

 bands; hind femora and tibiae yellow quadratus 



Front tibiae of the male gently and evenly convex on the inner side, tlie tip 

 on the outer side less produced, more angular; second segment of the 

 abdomen in both sexes with a small rounded spot on each side, fifth seg- 

 ment in the male without yellow, legs chiefly black hyperboreus 



