26 PROC. ENT. SOC. WASH., VOL. 22, NO. 2, FEB., IQ2O 



C. Ovipositor cylindrical, with terminal circlet of spines 



Prcctacanthus. 



CC. Ovipositor compressed, without spines Erax. 



BB. Posterior branch of third vein terminating behind tip of wing; an- 

 terior branch without stump. 



D. Three submarginal cells present. 



E. Abdomen shorter than wings; body thickly pilose, Mallophora. 



EE. Abdomen longer than wings; body thinly pilose. .Promachus. 



DD. Two submarginal cells present Asilus. 



Ommatius Wiedemann . 



O. marginellus Fabricius. Fairly common; June 14 to Sep- 

 tember 1; in copula, July 28, August 6 and September 1. P. I. 



Proctacanthus Macquart. 

 Key to the Species. 



A. Abdomen largely reddish; thorax dark brown rufiventris. 



AA. Abdomen not reddish. 



B. Thorax with brown markings; wings clear brown philadelphicus. 



BB. Thorax with dark, nearly black markings; wings pale brown. 



C. Large stout species, middorsal stripe of thorax gray-pollinose, not 



plainly differentiated milbertii. 



CC. Smaller, rather slender species; thoractic stripe usually plainly 

 differentiated and not distinctly pollinose brevipennis. 



P. brevipennis Wiedemann. Bladensburg, Md., June 23, 1916, 

 R. C. Shannon; Branchville to Beltsville, Md., June 4, 1914, 

 L. O. Jackson; Beltsville, Md., June 25, 1915, R. C. Shannon; 

 June 14, 15, 18, July 4, McAtee; July 6, prey Anomala sp., 

 Banks; Odenton, Md., July 4, 1913, in copula, McAtee. 



P. milbertii Macquart. Chain Bridge, Va., September 17, 

 Banks. 



P. philadelphicus Macquart. Fairly common; June 25 to Oc- 

 tober; in copula September 3. Among the prey have been noted 

 a large tachinid fly, further unidentified, the grasshopper, Or- 

 phulella pelidna, the tiger beetle Cicindela punctulata, the honey- 

 bee, and the paper wasps, Vespula germanica and V, vulgaris. 



P. rufiventris Macquart. Maryland near Plummers Island, 

 June 29, 1913, R. C. Shannon. 



Erax Scopoli. 



Key to the Species. 



A. Dark brown species; wings smoky; mystax yellowish to reddish; ovi- 

 positor split at tip rufibarbis. 



AA. Black and gray species; abdominal segments usually gray or white 

 margined behind; mystax gray, grayish yellow, or mixed with black; 

 ovipositor not split at tip. 



