76 williston: new dipikka. 



Twenty-four specimens, South Dakota and Nebraska (J. M. 

 Aldrich). 



Asilus (Stenoprosopus) arizonensis, n. sp. 



female. Face and front rather narrow, wholly densely light yellow 

 pollinose, the bristles of the face (which are mostly confined to the 

 oral border) all white; face in profile vertical, without gibbosity, 

 straight, or gently conca\e in the middle. Antennae black, the 

 second joint yellowish; the first two joints with short black hair, 

 together about as long as the third; second joint a little shorter than 

 the first; arista about as long as the third joint. Beard not long, pure 

 white. Thorax in ground-color largely reddish yellow; mesonotum 

 opacjue yellowish, with three broad, brown stripes, nearly bare in 

 front, behind with stout bristles. Scutellum with a distinct groove 

 before its apex, its border with two approximated bristles. Abdomen 

 in ground-color black, with yellow hind borders; in life, ai)])arently 

 grayish-yellowish i)ollinose. witli more distinctly yellow hind borders. 

 Legs yellow; a spot on the upper side of the hin<l and front femora, 

 the tip of all the tibiae, and the tip of the tarsal joints brownish; 

 femora slender. Wings grayish hyaline, ])ure hyaline on the basal 

 middle portion. Tip of the oviduct with small bristles. 



Length, i y-uS mm. 



One specimen, .Ari/una, (J. H. Coinstock) No. 175. 



Empis sociabilis, n. sp. 



Male. Eyes closely contiguous. Frontal triangle and face bare, 

 gray pollinose. Antennae black. Palpi slender; proboscis longer 

 than the vertical diameter of the head. Thorax brownish gray, 

 opaque, the mesonotum with three, narrow, inconspicuous, brown 

 stripes. Abdomen brownish black, subshining; pile on the sides in 

 front light-colored, rather long. Hypopygium small, black; the 

 inferior lamellae small, ovate. Legs black. Wings hyaline; stigma 

 narrow, brown. 



Length, 5-6 mm. 



Six specimens, Washington (Prof. C. \'. Piperv 



Chilosia chalybescens, n. sp. 



Male. Eyes densely and long pilose; pile of dorsum of thorax 

 yellow in front and behind, bkck across the middle; abdomen steel- 

 blue. Frontal triangle with light-colored, vertical triangle with black, 

 pile. Antennae black, the third joint rounded. Front and face 

 shining black; face in profile with a long shallow concavity; lateral 

 grooves well marked. Dorsum of thorax shining greenish black, 



