16 PROCEEDINGS OF THE NATIONAL, MUSEUM. vol.65. 



Distribution. — Tennessee Pass. Colorado, July 8. Fairbanks, 

 Alaska, June 30 to July 4, 1921, J. M. Aldrich, collector. Moscow, 

 Idaho, no date. Custer, South Dakota, no date. Tabernash, Colo- 

 rado, August, E. S. Tucker, collector. Mountains near Sheridan, 

 Wyoming. Mount Constitution, Washington (Orcas Island) July 

 7, 1905. Bozenian, Montana, 4,800 feet, June 21, 1900, R. E. 

 Cooley, collector. Bozeman, Montana, 4,800 feet, July 8, 1901, E. J. 

 S. Moore, collector; Moscow Mountain, Idaho, July 8, 1911. Yellow- 

 stone Lake, Montana, August 8, 1918. Moscow Mountain, Idaho, 

 July 5, 1919, A. L. Melander, collector (A. L. M.). Farewell Creek 

 Saskatchewan (C. W. J.). 



8. SCELLUS AVIDUS Loew. 



Plate 1, fig. 7; plate 2, figs. 16 and 22. 

 Scellus aiudus Loew, Monographs of North American Diptera, 1864, pt. 2, p. 207. 



Male. — " Thoracis dorso aeneo-nigro, nitido, margine et linea, 

 media cinereo-pollinosis, pleurarum plaga supera, abclomineque ex 

 viridi laete cupreis, nitidissimis, halteribus albis, alls cinereis, punctis 

 duobus nigris, altero in vena transversa posteriore, altero in ultimo 

 venae longitudinalis quartae segmento ; lamellis analibus maris albis, 

 basi et apice tamen nigris. 



" Upper side of the thorax bronze-black, shining, its margin and 

 a middle line dusted with gray pow^der; a large spot on the upper 

 part of the pleurae and the abdomen l)right greenish-copper colored, 

 very shining; halteres white; wings gray with two large dots, one 

 on the posterior transverse vein, the other upon the last segment of 

 the fourth longitudinal vein; the anal appendages of the male are 

 white, but their basis and tip are black. Long, corp. 0.17. Long. al. 

 0.21. 



" Male. — Face somewhat broader than in the previous two species, 

 dusted with bright ocher-yellow powder, opaque. Front Avith white 

 dust. Antennae black. Most of the upper side of the thorax bright 

 bronze-black with faint violet reflections; its whole margin has a 

 rather broad border dusted with a whitish-gray powder, and there- 

 fore opaque; there is also a narrow middle line, which is mucli 

 abbreviated behind and likewise dusted with a white-grayish powder. 

 The upper part of the pleurae, from the shoulder to the root of the 

 wings, is entirely without dust, metallic greenish-copper colored, 

 very much shining; as I have only a single specimen, I am unable 

 to judge with certainty whether this large shining spot is also present 

 in fresh specimens, as I believe it to be, or whether in the above-de- 

 scribed specimen it is merely rubbed off; the other parts of the 

 pleurae are dusted with gray. The scutellum, which has two 

 bristles, is greenish-bronze colored and opaque. The very shining 

 abdomen is of a bright coppery color, but assumes, when its surface 



