18G BULLETIN 31, UNITED STATES NATIONAL MUSEUM. 



iiiittMiiuv, below strongly produced forwards, the tubercle verj- large; in 

 the middle with a broad, shining black stripe, reaching to the base of the 

 antennae and on the lower half only slightly grayish dusted ; elsewhere, 

 as on the greater i)art of the front, clothed with whitish-yellow dust; 

 cheeks sliining black ; the lower border of the cheeks forms with the 

 plane of the occiput an obtuse angle. Antenuse black; immediately 

 above their base a shining black spot ; the vicinity of the ocelli black ; 

 the middle line of the front also somewhat darker ; pile of the front 

 black ; at the vertex in moderate extent yellowish. Thorax opaque 

 black, the usual stripes grayish, very narrow and indistinct, in the mid- 

 dle interrupted, the median ones obsolete behind. The pile of the 

 thorax is yellowish throughout, without any intermixture of black. 

 Scutellum brownish, shining, on the middle with blackish, on the bor- 

 der with yellow pile. Abdomen black, opaque, the hind margins of the 

 segments, successively wider posteriorly, moderately shining; second 

 segment on each side with a large, yellow, three-cornered spot, the 

 inner angles of which show only a trace of whitish color, and do not 

 approach each other very closely; third segment on each side with a 

 curved, narrow, semi-fascia, not quite reaching the lateral margin, at 

 which there is no trace of a jellow spot ; fourth segment with similar 

 whitish semifasciai, which attain the lateral margins; on the last seg- 

 ment they are shorter and less distinct. The pile of the abdomen is 

 thick, erect, noticeably longer than in the related species, of a yellow 

 color, on the hind margin of the second segment somewhat darker, on 

 the hind borders of the following segments in moderate extent blackish; 

 on the lateral margins of the abdomen the pile js throughout yellowish, 

 only on the posterior angle of the posterior segments is there any black- 

 ish pile. Femora black, the hind pair of moderate width ; in all the tip 

 is brownish-yellow, in the hind pair, however, only at the extreme tip ; 

 tibia? black, base brownish-yellow, the hind pair but little arcuate, at 

 their end slightly yet distinctly thickened ; tarsi black throughout. 

 Wings hyaline, somewhat grayish-brownish tinged; stigma dark brown, 

 sharply bordered at each end. 



M. horealis is distinguished from H. groenlandicus by the more oblique 

 Ijrofile of the face, by the greater length of the pile on the thorax, scu- 

 tellum and abdomen, by the absence of black pile on the hind part of 

 the black dorsal stripes, by the greater indistinctness and more remote 

 position of the median light-colored stripes, by the less dilatation of the 

 hind femora, which in the females on the distal half on the outer side 

 has a distinct longitudinal groove, while in R. grcenlandicus there is only 

 a large flat impression. — Loew, 1. c, translation. 



Helophilus mexicanus. (Platf VIII, fig. 7.) 



HelcpMluK mexicanus Macqnart, Dij)!. Exot.,ii, 2, (»4, 6; tab. ii, fig 2; Oaten 



Sackeii, Cat. Dipt., p. 2(17. 

 HeJophilux pohigrammuH Loew, Ceiitur., x, Tjo ; Osteu Sacken, West. Dipt., 338. 

 Asemost/rphus oculi/erus Bigot, Ainiales Soc. Eut. Fr., 1883, p. 3r)0. (Male.) 

 f Anemosyrphus nigroaoutatus Bigot, ibid., p. 351. 



Habitat. — Washington Territory, California !, Mexico (Macq., O. S.). 



