182 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.48. 



Genus PLAGIOPROSPHERYSA Townsend. 



PLAGIOPROSPHERYSA PARVIPALPUS v. d. Wulp. 



A series of 12 specimens collected on mesa; these vary in size from 



5 to 7 mm. 



Genus PLAGIA Meigen. 



PLAGIA AMERICANA v. d. Wulp. 



On mesa August 6. 



Genus SIPHOPLAGIA Townsend. 

 SIPHOPLAGIA ANOMALA Townsend. 



One male from sunflower August 10. 



Genus SENOTAINIA Maequart. 



SENOTAINIA TRILINEATA v. d. Wulp. 



A series of eight specimens collected. It is abundant here, but sits 

 on the ground on stones and is difficult of capture. 



SENOTAINIA RUBRIVENTRIS Maequart. 



Found in company with the preceding species. 



Genus PACHYOPTHALMUS Brauer and von Bergen- 



stamm. 



PACHYOPTHALMUS FLORIDENSIS Townsend. 



A series of 10 specimens from an arroyo on mesa. If the extra 

 row of weak frontal bristles be disregarded, this species will go into 

 Senotainia. Occasionally one finds a specimen in which the outer 

 rows of bristles are nearly obsolete. Thus a few specimens of this 

 species were found standing in the United States National Museum 

 collection under Senotainia rubriventris , from which species it is easily 

 distinguished by its bright yellow antennas and black hypopygium. 

 One specimen bearing label "Coll. Townsend, Brownsville, Texas, 

 June/' has the abdomen reddish in ground color, but is otherwise 

 identical with floridensis. 



Genus SIPHOSTTJRMIA Coquillett. 



SIPHOSTURMIA ROSTRATA Coquillett. 



A pair taken on the dry mesa about flowers. This is the first 

 record of this species from the arid southwest. 



Genus EXORISTA Meigen. 



EXORISTA PYSTE Walker. 



In the foothills, among the scrub oaks, early in August, this species 

 was present in swarms. Their high-pitched, mosquitolike note could 

 be heard many feet distant. No insect which might serve as a host 

 could be discovered on the oaks at this time, but Mr. Wildermuth/s 

 notes show that these bushes had been heavily infested by a species 

 of Mdlacosoma a few weeks previously. 



