no. 2070. PARASITIC AND PREDACEOUS DIPTERA— WALTON. 179 



Family TACHINIDAE. 

 Genus GYMNOSOMA Meigen. 



GYMNOSOMA FULIGINOSA Desvoidy. 



One robust specimen taken near irrigation pond. 

 Genus MYIOPHASIA Brauer and von Bergenstamm. 



MYIOPHASIA SETIGERA Townsend. 



A series of more than 40 specimens was taken on the mesa. This 

 species at first glance resembles very closely some specimens of M. 

 aenea taken in the northeastern portions of the United States. It is, 

 however, usually more bristly as regards the sterno-pleural region, 

 most of these specimens possessing three or more sterno-pleural 

 bristles. Several of the individuals bear but two. An actual meas- 

 urement of the angle included between the penultimate section of the 

 fifth vein and the hind cross vein in a series of 20 specimens in this 

 species gives an average of 114°. The same angle in a similar number 

 of specimens of M. aenea taken in various parts of the north and east 

 gives an average of 92°, a difference of 22°. Thus it appears that the 

 excess of obliquity of the hind cross vein in M. setigera is a good spe- 

 cific character, much more stable in fact than the hairiness of the 

 eyes, the presence or absence of a weak pair of marginal macrochaetse 

 on the second abdominal segment, or the closing or opening of the 

 first posterior cell. These latter characters are all variable and unre- 

 liable within specific limits in this genus. 



MYIOPHASIA ROBUSTA Coquillett. 



A series of 15 specimens male and female collected on sunflowers in 

 an arroyo on mesa. The type of this species, a large male, seems to 

 be the only specimen mentioned in the literature; accompanying it 

 in the National Museum collection are three specimens from Mexico 

 City, Mexico. This is a very distinct species. The female has not 

 been described, and as the sexes are dichroic, a description is appended 

 herewith. 



Female. — Uniform cinereous pollinose, abdomen slightly brassy. 

 Front fully one and one-half times as wide as either eye, sides widely 

 divergent below. Frontal vitta dark brown, occupying one-third of 

 width of front at narrowest part. Parafacials wider than facial 

 depression. Cheeks nearly two-thirds as high as eye, yellowish 

 gray pollinose. Antennae reddish, third antennal joint on anterior 

 edge brown, about one and one-half times as long as second joint. 

 Arista incrassated at extreme base, microscopically pubescent. Pro- 

 boscis and palpi nearly black. Two pairs of orbital bristles, para- 

 facials bearing a distinct row of large hairs extending from base of 

 antennae to the lower edge of eye, other scattered hairs also present. 

 A pair of cruciate frontals immediately before ocelli. Eyes usually 



