274 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



Observation. — This paper was already in press when I received a speci- 

 men of Epibates (Apatomyza) niger Macquart, collected by Mr. H. K. Mor- 

 rison in Georgia. It is a male, but a not very well preserved specimen. 

 The little spines on the thorax are almost obsolete in this species ; with 

 a strong magnifying glass, some traces of them are visible. The eyes 

 are not contiguous on the front, but, like those of E. muricatus $, sepa- 

 rated by a narrow, linear interval. The third antennal joint is much 

 broader than in the other species ; it expands immediately beyond the 

 base, contracts again about the middle, and ends in an elongated point ; 

 the curves it forms, above and below, are not quite symmetrical, the one 

 below being flatter ; altogether, it has the shape of an elongated and 

 somewhat irregular ace of spades. The principal figure of Macquart's 

 gives a somewhat more correct representation of it than the figure of 

 the head in profile. The anal cell is open. 



Family THEREVID^. 



Psilocephala costalis Loew, Centur., viii, 16. — California. 



Thereva comata Loew, Centur., viii, 9. — California. 



Thereva FUCATA Loew, Centur., x, 37.— California. 



Thereva melanoneura Loew, Centur., x, 36. — California. 



Thereya hirticeps Loew, Berl. Entom. Zeitschr., 1874, 382. 

 Francisco. 



Xestomyza planiceps Loew, Centur., x, 38.— California. 



California seems to be quite rich in Therevidce, as I have collected four 

 species of Thereva (two in Marin County, one in Southern California, 

 and one in Yosemite Valley), none of which I am able to identify with 

 the above quoted descriptions. Xestomyza planiceps I received from Mr. 

 Henry Edwards. The following snow-white Thereva was very common 

 in Yosemite Valley about the beginning of June : — 



Thereva vialis n. sp., <?.— Grayish ; clothed with snow-white pile, 

 especially on the abdomen ; antennas black ; femora black, with gray 

 pollen ; tibias brownish-yellow, black at tip ; tarsi dark brown, brownish- 

 yellow at base. Length 8-9 mm . 



Male. — Head white, with white pile ; some black bristles on vertex, 

 and alongside of them on the occiput; some others on the face on each 

 side of the antennas (in some specimens only a few, which, for this 

 reason, are discernible with difficulty); antennas black, first joint not 

 longer than the two following together, slender, whitish -pollinose, with 

 white pile and near the tip with some black bristles. Thorax gray, 

 being clothed with a dense pollen; two distinct longitudinal stripes 

 white; white pile, especially on the pleuras; the ordinary bristles black. 

 Abdomen densely clothed with silvery-white pollen and long white pile ; 

 a few black bristles on the under side of the hypopygium. Femora 

 dark, clothed with gray pollen and white pile ; tibias brownish-yellow, 

 the tip black ; tarsi dark brown or black, base of the first joint brownish- 

 yellow; on the middle tarsi, this color occupies nearly three-quarters of 





