THE SYRPHIDAE OF OHIO 79 



73. Abdomen narrowed basally; slender species (see 27). 



Abdomen in no wise club-shaped 74 



74. Face transversely arched, not produced, not tuberculate, abdomen more or less 



elongate and nearly bare 75 



More or less thickly pilose species; often large 76 



75. Hind femora extraordinarily thickened (Fig. 234); anterior cross-vein rectangu- 



lar, and before the middle of discal cell Syritta (p. 94) 



Hind femora distinctly thickened, but the cross-vein distinctly oblique, and 

 near or beyond middle of discal cell > Xylota (p. 94 ) 



76. Scutellem, margin of thorax and pleurae with distinct bristles, femora slender 



(Chrysochlamys) Ferdinandea 



No bristles anywhere on body . . , 77 



77. Face short, not produced, concave from antennae to oral margin, not tuberculate; 



hind femora thickened 78 



Face produced, long 79 



78. Abdomen elongate Brachypalpus (p. 95) 



Abdomen very broad; thorax densely pilose; middle femora of male sometimes 



{Hadroinyia) with a stout, basal, inferior spur Pocota 



79. Face produced forward, pointed, concave from antennae to tip, not tuberculate; 



hind femora thickened Crioprora ( p. 96) 



Face not evenly concave in profile, but tuberculate or convex 80 



80. Third joint of antennae produced above into an anteriorly directed, conical 



process, terminatingin the thickened arista (Figs. 225, 226)Merapioidus (p. 96) 



Third joint of antennae obliquely oval; hind femora rarely thickened 



Criorhina (p. 96 ) 



81. Hind femora with conical, tooth-like protuberance below near distal end; 



antennae more or less elongated; sixth vein directed obliquely outward beyond 



anal cell Spilomyia (p. 97) 



Hind femora without much protuberance; sixth vein beyond anal cell not 

 unusual 82 



82. Antennae inserted low down, near middle of head in profile, the face not longer 



than front (Fig. 235) Temnostoma (p. 98) 



Antennae inserted on a conical process; front short, the face nnicli produced 

 downward (Fig. 236) ; antennae long or short Sphecomyia (p. 98) 



In the following discussion of genera, species known to occur in the State are 

 consecutively numbered and their names printed in bold face type. In addition 

 certain species, whose known distribution indicates probable occurrence, are included 

 wnth the hope of adding to the usefulness of the paper. Names of such species are 

 unnumbered, printed in italics and marked with a star (*). Their recorded distribu- 

 tion is indicated following the name. 



Microdon Meigeii 



1 Hind metatarsi not, or but slightly thickened; third segment of antennae about 

 as long as the first, blackish species, abdomen without orange yellow, tristis 

 Hind metatarsi strongly thickened in the male, brownish species 2 



2 Third joint of antennae longer than the first fuscipennis 



Third joint of antennae not longer than the first 



*globosus'Pa.h. (Mich., Col., Va., N. J., Fla., Carolina, Tex.) 



