Jan., 1914.] Tabanus Longus, Fulvulus and Sagax. 225 



TABANUS LONGUS, FULVULUS AND SAGAX. 



Jas. S. Hine. 



These three species of North American horseflies have proven 

 more or less troublesome from the standpoint of determination on 

 account of their resemblance to one another and the variation 

 among different specimens of each species as well as their general 

 aspect which corresponds very closely with several other species 

 of their genus. 



The following combination of general characters will serve well 

 to group the three species in question and separate them from 

 others similar in appearance: the wings are transparent with no 

 vestiage of infuscation on the cross veins or furcation of the third 

 vein; no suggestion of a stump of a vein on the anterior branch 

 of the third vein in any of the specimens I have examined; the 

 costal cell is transparent or very pale yellowish; the general color 

 of all specimens is yellowish or brown, never black; the abdomen 

 has a middorsal stripe with a row of spots on each side; these 

 spots are usually rounded and do not reach the hind margins of 

 their respective segments; in longus the dorsal stripe is narrow 

 and nearly always abbreviated posteriorly and in rubbed speci- 

 mens may disappear altogether. The characteristic thing about 

 the middorsal stripe in the thrae species under consideration is 

 its widening on the posterior margin of each segment thus pro- 

 ducing an irregular stripe quite different from the regular stripe 

 in costalis, linecla and a long list of other North American species. 



With the material at hand the opportunity is given for a 

 study of variation. Each of the three species has been divided 

 into series mainly from the standpoint of coloration and size as 

 not much variation in structure is apparent. Coloratioti appears 

 to be largely a matter of locality and almost invariably specimens 

 from southern regions are decidedly smaller than those taken 

 well north. 



The following key should be of use in separating the species 

 here considered: 



1. Third segment of the antenna narrow, without a distinct angle near 

 its base on the dorsal side, sagax. 



Third segment of the antenna wider, with a distinct angle near its base 

 on the dorsal side. 2. 



2. Thorax yellowish, without stripes, middorsal abdominal stripe 

 distinct, front in the female narrow, fulvulus. 



Thorax brown, often faintly striped, middorsal abdominal stripe narrow 

 and usually more or less abbreviated posteriorly, front in the female dis- 

 tinctly wider, longus. 



