6 University of Michigan 



insect in Arizona and know it to be an active robber fly which 

 catches a variety of insects for food. It has a wide distribu- 

 tion in arid regions. 



Mallophora giiildiana WilHston. — This is a much smaller 

 species than the preceding, but has similar habits. It flies from 

 one perch to another when disturbed, and catches many small 

 insects. The yellowish gray color is more or less protective on 

 the sandy areas where it is usually found. 



ProjuacJius magniis Bellardi. — The genus Promachus con- 

 tains several species of large active flies which are often 

 abundant and are known to have an influence in materially 

 reducing the numbers of insects upon which they prey. Their 

 large size makes it possible- for them to dispose of most other 

 insects, and on account of their abundance much food is re- 

 quired. In my treatment of Promachus in a former paper, I 

 had to omit the present species because material was not 

 available. In this collection there are more than twenty fine 

 specimens of both sexes, and from this material the following 

 short description is formulated. Bellardi had only the female, 

 so the male is here described for the first time. 



Alale. — Length 27-35 millimeters. General color dark; 

 mystax and beard white; antennae and proboscis black; palpi 

 with black bristly hairs; all bristles of the whole body black; 

 legs very dark reddish ; thorax of the same color with narrow 

 gray stripes dorsally; wings reddish hyaline, slightly darker 

 at the apex ; abdomen black above with gray posterior borders 

 to the segments. There is no great marking in the first pos- 

 terior cell as in Promachus vcrtchratus, but the darker area at 

 the ap6x of the wing crosses this cell. The male and female 

 are easily associated; the former has the genitalia densely 

 silvery pilose above. The most apparent variation in the 



