1911] Promachus and Proctacanthus 165 



KEY TO THE SPECIES OF PROMACHUS. 



1. First submarginal cell with a gray shadow which sometimes is very narrow. .2 

 First submarginal cell without any trace of a gray shadow 12 



2. Male genitalia with dense silvery hair above, color of the tibiae very near 



like that of the femora (> 



Male genitalia without silvery hair above, color of the tibiae usually in strik- 

 ing contrast to that of the femora 3 



3. Gray bands on the dorsum of the abdomen fully as wide as the black bands. .4 

 Gray bands on the dorsum of the abdomen confined to narrow posterior 



borders of the segments 5 



4. Thorax deep reddish brown, male genitalia clothed with black hair..rufipes 

 Thorax yellowish gray, male genitalia clothed with gray hair. . . .vertebratus 



5. Gray shadow in the first submarginal cell less than half as wide as the cell; 



male genitalia rounded at apex sackeni 



Gray shadow in the first submarginal cell darker in color than usual, distinct- 

 ly more than half as wide as the cell; male genitalia truncate at apex forfex 



6. Abdomen with black hair on some or all of the first five segments above. .9 

 Adbomen without black hair on any of the segments above 7 



7. Abdomen uniformly clothed with short gray hair, mystax very pale yellow or 



nearly white, beard white. truquii 



Abdomen clothed with yellow hair, beard and mystax distinctly yellow. . . .8 



8. Gray shadow in the first submarginal cell wider than the marginal cell, male 



genitalia almost as long as abdominal segments five, six and seven com- 

 bined fitchii 



Gray shadow in the first submarginal cell distinctly narrower than the margi- 

 nal cell, male genitalia shorter than abdominal segments six and seven 

 combined .' quadratus 



9. Mystax white or with a very slight shade of yellowish, legs chiefly black. . 10 

 Mystax plainly yellow, legs chiefly yellowish red 11 



10. Abdomen densely brown pollinose on the sides albifacies 



Abdomen gray pollinose on the sides and extending across narrowly on the 



hind margins of the segments princeps 



11. Abdomen densely brown pollinose on the venter and sides, wings plainly 



brownish bastardii 



Abdomen pale yellowish gray pollinose on the venter and sides, wings nearly 

 hyaline quadratus 



12. Legs pure black 13 



Legs more or less reddish 14 



13. Abdomen distinctly banded with black and gray, the gray bands slightly 



more than half as wide as the black nigripes 



Abdomen not distinctly banded, although the narrow posterior margins of 

 the segments are somewhat different from the other parts by appearing 

 whiter aldrichli 



14. Very large species, 35 to 40 millimeters in length giganteus 



Small species, not over 25 millimeters in length minusculus 



Promachus vertebratus Say. 



Total length 26 to 31 millimeters. Front and face clothed with 

 yellow pollen, hairs and bristles of the whole head yellowish, beard 

 paler than the mystax, often some of the bristles on various parts of the 

 head are black but there does not appear to be any uniformity as to 

 which ones are black and often there are none of this color. Proboscis 

 shining black, palpi clothed with yellowish hair with an intermixture 

 of black in some specimens, antennae black. Thorax yellowish pol- 

 linose, dorsum with a brown stripe at the middle divided by a narrow 

 gray line, wings dilute brownish; legs somewhat variable in color, 

 clothed with black bristles and recumbent pale hair, femora in large 

 part black although they may be almost entirely reddish, or even only 



