TABANID^ OF OHIO. 29 



A SYSTEMATIC TREATISE OF OHIO SPECIES. 



In the keys which are given below I have included a few 

 species which have never been taken in Ohio, but in the descrip- 

 tions only such species are considered as have been taken in the 

 state and are deposited in the Ohio State University collection. 

 Before atempting to use the keys one should acquaint himself 

 with he meaning of terms as given below. 



EXPLANATION OF TERMS. 



Antennae. Always three segmented. Third segment compound, 

 composed of from five to eight annuli or rings, bearing a 

 prominent basal process in Tabanus. This process is absent 

 or at least rudimentary in the other genera of our fauna. 



Apical-spot. That part of the dark picture of the wing of Chry- 

 sops beyond the outer border of the cross-band, which term 

 is explained below. 



Basal cells hyaline. As this character is used in the key for the 

 females of Chrysops some explanation is necessary. Those 

 species which have slight infuscations at the base or apex of 

 either of these cells are treated as having the basal cells hya- 

 line, while those species with these cells infuscated far beyond 

 the middle are placed in the other group. C. montanus has 

 the most infuscation of any species placed in the former 

 group, and C. frigidus the least of any placed in the latter. 



'Color of eyes. In life nearly all the species have highly colored 

 bands or spots on the eyes. These are not distinguishable 

 in dry specimens, but may be revived by moisture. How- 

 ever, this process usually destroys many other characters 

 which it is desirable to retain. 



■Cross-band. The part of the dark picture of the wing of Chry- 

 sops beginning at the costa in the region of the stigma and 

 proceeding backward, sometimes reaching and sometimes not 

 reaching the posterior border of the wing. 



.Empodiiim. The plural form empodia is usually used. A pad or 

 cushion located between the pulvilli at the distal end of each 

 last tarsal segment. 



£yes hairy. This character is very plain in some species, but 

 hard to see in others. It is always most easily seen in the 

 males. 



Face. The anterior surface of the head between the eyes and be- 

 low the antennas. 



Facial callosities. Prominent elevations, one on either side of the 

 face. They vary in coloration. 



