Occasional Papers of the Museum of Zoology 7 



specimens studied is a noticeable difference in the width of the 

 wings. This is not a sexual characteristic, for it is shared by 

 both males and females. 



Promachus gigantuUis Hine. — This is one of the largest 

 American species of its family. Specimens at hand range 

 from 35 to 47 millimeters in total length. Judging from the 

 size, it must be an important predaceous enemy of other in- 

 sects in regions where it abounds. The type was collected at 

 El Paso, Texas. 



Asilus gracilis Wiedemann. ---This species is distinguished 

 from all other described species of Asilus in this country by the 

 long antennal bristle, which is fully twice as long as the third 

 antennal segment. It is a pale slender species, well adapted 

 to hiding on the gray sand. 



Asilus lcucopogo)i Williston. — The species is a common one 

 on sand in arid regions, and is difficult to capture because of its 

 protective coloration. It resembles the preceding species, but 

 the antennal bristle is much shorter and the genitalia are very 

 dift'erent. 



