Tabanidae of Nebraska 5 



Apex of the wing beyond the cross-band not entirely hyaline 2 



2. First antennal segment distinctly enlarged; the hyaline spot is 

 crescent-shaped and entirely surrounded by the dark of the 

 wing; the first two segments of the abdomen yellow on the sides, 

 length 2, 7-9 mm., S, 7-8 mm fulvaster 



First antennal segment not distinctly enlarged 3 



3. A hyaline spot in the discal cell; face grayish with four black 

 dots; length ?, 9-10 mm., 8-9 mm discalis 



No hyaline spot in the discal cell 4 



4. First basal cell hyaline 5 



First basal cell altogether or to a considerable extent infuscated 7 



5. Abdomen with a middorsal yellow stripe on the first four seg- 

 ments, which is attenuated posteriorly; length 9, 7-8 mm. obsoletus 



Abdomen without a middorsal yellow stripe 6 



6. A black triangle encroaches upon the posterior part of the 

 yellow on each side of the second abdominal segment; length $, 



8-11 mm.; $, 8-9 mm moerens 



No black triangle on each side of the second abdominal segment; 

 length 9, 8 mm., S, 7-8 mm callidus 



7. Frontal triangle, thoracic stripes and scutellum yellow; length 



$, 9 mm.; $, 7-8 mm vittatus 



Frontal triangle and scutellum mostly or altogether black 8 



8. The hyaline triangle crosses the second longitudinal vein, apical 

 spot invades the first posterior cell; length 9, 8-9 mm sequax 



The hyaline triangle does not cross the second longitudinal vein, 

 and is almost as wide at the apex as at the base of wing; length 

 9, 7-8 mm pikei 



Chrysops carbonarius Walker. List., i, 203 (1848) ; Hine, Ohio, Natur- 

 alist, v. No. 2, 220 (1904). 

 1848. yiiger Walker, List., i, 202. 

 1850. provocans Walker, Dipt. Saund., i, 73. 

 1850. (?) atra Macquart, Dipt. Exot. Suppl., iv, 40. 

 1875. fugax Osten Sacken, Prodrome, i, 375; Williston, Trans. Kans. 

 Acad. Sci., x, 132 (1887). 



Ill 



