TABANIDA OF OHIO. 31 
the others, but when there are five the basal one is much longer 
than any of the others, often longer than all the others combined. 
The eyes are separated in the female and contiguous in the 
male. They have an area of enlarged facets above in the latter 
sex, and in life are marked with green and purple markings in 
both sexes. In dry specimens these markings are lost, but may 
be partially restored by moisture. Ocelli are present in some 
species and absent in others; and the occiput is flat or concave. 
The proboscis projects and in some species is much elongated ; 
the maxillary palps are large and two segmented. 
The thorax and abdomen are clothed with more or less hair, 
but no spines or bristles. The wings are rather large and en- 
compassed by the marginal vein, two submarginal and five pos- 
terior cells present, basal cell elongate, anal cell usually and some- 
times some of the posterior cells closed. Tegule always promi- 
nent. Legs ample; pulvilli moderate; empodia developed pulvi- 
liform; middle tiba with spurs at the tip. 
Abdomen composed of seven visible segments, broad, never 
constricted. 
Key to the North American Genera. 
1. Hind tibiae with spurs at the tip, sometimes small 2, 
Hind tibiae without spurs 6. 
bo 
Third segment of the antenna composed of eight annuli, the 
first of which is only a little longer than the following ones 3. 
Third segment of the antenna composed of only five annuli, 
the first of which is much longer than any of the following 
ones; ocelli present D 
3. Front of female narrow; ocelli present or absent; fourth 
posterior cell at least open Pangonia. 
Front of female broad with a large denuded callus; ocelli 
present 4, 
4. Eyes in the female acutely angulated above; wing in both 
sexes with a dark picture Goniops. 
Eyes in the female not acutely angulated above; wings hyaline 
in both sexes Apatolestes. 
5. Second segment of the antenna about half as long as the 
first; eyes in life with numerous small dots Silvius, 
Second segment of the antenna as long or but little shorter 
than the first; wings with a, dark picture Chrysops. 
6. Third segment of the antenna without, or with a rudimentary 
basal process 3 ; Te 
Third segment of the antenna with,a well developed basal 
process “ P , Labanus.* 
7. Front of female as broad as long the callus transverse Haematopota. 
Front of the female narrow +s] / Diachlorus. 
*Including Atylotus and Therioplectes. 
