TABANIDA) 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 bey ond 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. 
Empodium. The plural form empodia is usually used. A pad or 
cushion located between the pulvilli at the distal end of each 
last tarsal segment. 
Eyes 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 antenne. 
Facial callosities. Prominent elevations, one on either side of the 
face. They vary in coloration. 
