338 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



darker antennae, the broader yellow cross-bands on the abdomen, leav- 

 ing a narrower black posterior margin of the segments. 



I have five males from Petaluma, Sonoma County, Gal., April 28. 

 Mr. Loew described specimens from Nebraska (F. V. Hayden). I have 

 also seen some from the Eed River of the North (R. Kennicott). 



Helophilus polygrammus Loew, Oentur., x, 55. — The author de- 

 scribes the female. In the male, the front is but very little narrower 

 than in the female; the color of the abdomen is lighter yellowish-brown 

 on the sides, especially on the second and third segments. 



Sab. — Webber Lake, Sierra County, California, July 27. A male and 

 a female. Oregon (H. Edwards). 



Mallota posticata Fabricius, Syst. Autl., 237,21 (Erisfalis). — I took 

 a male specimen near San Rafael, CaL, May 29, which resembles this 

 species very much. Unfortunately, I have only a single damaged male 

 from the State of New York for comparison. In the Californian speci- 

 men, the eyes do not come in contact, as there is a very narrow frontal 

 interval between them. There is a brown cloud in the middle of the 

 wing, especially on the central cross-veins, which does not exist in my 

 eastern specimen. These differences render the specific identity uncertain. 



Macquart is wrong when he calls the eyes of the male pubescent. My 

 statement (in the Bull. Buffalo Soc. N. H., Dec, 1875, 64), that the 

 male has a projecting spur in the middle of the hind tibiae, is likewise 

 erroneous ; it was based upon a specimen in which the pubescence of the 

 hind tibiae was clotted, so as to produce the appearance of a spur. 



Polydonta curvipes (Wiedemann ; synonym in the male sex with 

 P. Mcolor Macq.; in the female with Helophilus albiceps Macquart, Dipt. 

 Exot., ler suppl., 132, 9). — The male of this species is most remark 

 ably different from the female. A female in the Mus. Comp. Zool., 

 Cambridge, Mass., from San Francisco, Cal. ( W. Holden), resembles the 

 eastern specimens ; only the face is more whitish than yellowish, and the 

 vertex a little less thickly yellowish-pruinose. I also have received 

 specimens from Northern New Mexico (W. L. Carpenter). I would not 

 pronounce on the identity of these western specimens before seeing the 

 males. 



Tropidia quadrata (Say), a male from Marin County, California (EL 

 Edwards), does not differ from specimens from the Atlantic States. 



Pocota alopex n. sp. — Black ; thoracic dorsum with dense yellowish- 

 rufous pile ; pleurae black ; wings tinged with reddish-brown anteriorly, 

 subhyaline posteriorly. Length 10-ll ram . 



Female. — Antennae brown, first joint black; arista rufous; head 

 black, shining; front rather broad, beset with yellow pile. Thoracic 

 dorsum beset with dense yellowish-rufous pile, which nearly conceals 

 the shining black, submetallic ground-color; pleurae black, with black 

 pile; scutelium black, with a purplish reflection and long black pile 

 along the edge; halteres brownish. Abdomen black, shining, beset 

 with black pile and some scattered pale yellow pile toward the tip. 



