2 Everett E. Wehr ^ 



Only three of the North American genera of Tabanidae are 

 represented in the Nebraska fauna, viz., Silvius, Chrysops and I 

 Tabanus. In order to show the relationship of these three 

 genera, however, the following table (after Hine) of the nine 1 

 North American genera is given : 



1. Hind tibiae with spurs at the tip 2 



Hind tibiae without spurs 6 



2. Third segment of the antennae composed of eight annuli, the 

 first of which is only a little longer than the following ones 3 



Third segment of the antennae composed of only five annuli, the 

 first of which is much longer than the following ones; ocelli 

 present 5 



3. Front of female narrow; ocelli present or absent; fourth pos- 

 terior cell at least open Pangonia 



Front of the female broad with a denuded callus; ocelli present 4 



4. Eyes in the female acutely angulated above; wings in both sexes 

 with a dark picture Goniops 



Eyes in the female not acutely angulated above; wings hya- 

 line Apatolestes 



5. Second segment of the antennae about half as long as the first; 

 eyes in life with numerous small dots Silvius 



Second segment of the antennae as long or but little shorter 

 than the first; wing with a dark picture Chrysops 



6. Third segment of the antennae with a well developed basal pro- 

 cess Tabanus 



Third segment of the antennae without, or with a rudimentary 

 basal process 7 



7. All the tibiae enlarged, the hind pair ciliate Snoiviellus 



None of the tibiae enlarged and the hind tibiae not ciliated 8 



8. Front of the female as broad as long, the callus trans- 

 verse Haematopota 



Front of the female narrow Diachlorus 



108 



