Dec., 1904,] 
Tabanidap. 
2 I 9 
Chrysops Meigen. 
The species of this genus have fairly good characters. We 
have recognized the males of a number of the western species, 
but there are still several unknown. Twenty species are recog- 
nized in the following pages, one described as new. I offer the 
following key as an aid in separating them: 
1. Apex of the wing beyond the cross-band hyaline 2 
Apex of the wing beyond the cross-band not entirely hyaline 4 
2. Abdomen yellow on the sides of at least the first two seg- 
ments excitans 
Abdomen uniformly black ' 3 
3. Base of the fifth posterior cell hyaline carbonariiis 
Base of the fifth posterior cell not hyaline mitis 
4. Second antennal segment decidedly longer than the third ceras 
Second antennal segment not longer than the third 5 
5. First antennal segment distinctly enlarged 6 
First antennal segment not enlarged 10 
6. First and second antennal segments distinctly enlarged virgnlatus 
Second antennal segment not distinctly enlarged 7 
7. Hyaline triangle separated from the posterior margin of the wing 
by an infuscated space fulvaster 
Hyaline triangle reaches the posterior border of the wing 8 
8. Facial and frontal callosities almost entirely black or brown facialis 
Facial and frontal callosities yellow or the latter margined with 
brown 9 
9. Slender species, male with base of anal cell hyaline, female with 
two small black spots on the middle of the second abdominal 
segment pachycera 
Robust species, male with base of the anal cell infuscated, female 
usually with a geminate black spot on the second abdominal 
segment coquillettii 
10. A hyaline spot in the discal cell discalis 
No hyaline spot in the discal cell 11 
11. Whole face black in ground color 12 
Part or whole of face yellow 14 
12. Abdomen yellow on the sides frigidus 
Abdomen black • 13 
13. Apical spot separated from the cross-band noctifer 
Apical spot united with the cross-band nigripes 
14. Abdomen with longitudinal black stripes 15 
Black abdominal markings not in the form of stripes 16 
15. Four black stripes running the whole length of the abdomen sequax 
Two black stripes running the whole length of the abdomen, the 
two lateral stripes abbreviated pikei 
16. Frontal callosity yellow with narrow brown border coloradensis 
Frontal callosity black 17 
17. Cheeks entirely yellow furcatus 
Cheeks with a black band from the eyes to the margin of the 
mouth 18 
18. Yellow on each side of the second segment not enclosing any 
black, apex of the second basal cell hyaline for its entire 
width lupus 
Yellow on each side of the second abdominal segment enclosing 
a small black dot, hyaline at the apex of the second basal cell 
crossed by brown 
19 
