2 34 The Ohio Naturalist. [Vol. V, No. 2, 



30. Antennae black, or at most with a trace of red at the base of the 



third segment 31 



Antennee largely red 33 



31. Subcallus denuded centron 

 Subcallus not denuded 32 



32. Wing with brown clouds on the cross- veins and the furcation of 



the third vein sonoinensis 



Wing with no clouds on the cross-veins and furcation of the 

 third vein phcsnops 



33. Front of the female unusually wide above, distinctly narrowed 



anteriorly captonis 



Front of the female not unusually wide, sides nearly parallel 34 



34. Third antennal segment fully as broad as long laticornis 

 Third antennal segment longer than wide 35 



35. Costal cell bro^vrn 36 

 Costal cell hyaline 37 



36. Palpi robust epistatus 

 Palpi slender affinis 



37. Head decidedly wider than the thorax laticeps 

 Head not noticeably widened 38 



38. Base of the anterior branch of the third vein with a stump frenchii 

 Base of the anterior branch of the third vein not with a 



stump susurrus 



Tabanus aegrotus Osten Sacken. Easily identified by Osten 

 Sacken's description. It appears some like our eastern atratus, 

 but the wings may be said to be subhyaline instead of black as in 

 that species. Usually the whole body is black, but in some spec- 

 imens the abdomen above has a median row of very small white 

 triangles, one on the posterior border of each segment. 



Tabanus affinis Kirby. There is some variation in the extent 

 of red on the abdomen. This seems to occur in specimens from 

 the same locality to the same extent as in specimens from differ- 

 ent localities. Its size, fifteen to nineteen millimeters, makes its 

 determination rather easy, as it is the largest of our species with 

 pilose eyes. Some specimens of affinis and some of sonomensis 

 are rather close together, but the third segment of the antennae is 

 narrower in sonomensis and the basal process less prominent. 

 The palpi are very slender in affinis. 



Tabanus annulatus Say. Rarely collected and probalby there 

 is not more than a dozen good specimens in the collections of the 

 country. The front is narrow and the frontal callosity and what 

 in other species is called the spindle shaped line, unite to form a 

 very narrow raised line of nearly uniform width reaching nearly 

 to the vertex, eyes naked, a small ocelligerous tubercle. Thorax 

 uniform gray, abdomen brown with a gray posterior border to 

 each segment; wings hyaline. Length 12 to 14 millimeters. 

 Taken as far west as Kansas and Missouri. The species is one 

 of the anomalies of its family. 



Tabanus atratus Fabricius. Its large size and black color 

 serve to separate this species from all others of the western 

 Tegion. Taken as far west as Colorado. 



