101 



lying down a favorite place of attack seems to be under the thigh and 

 back belly, around the bag. With certain animals the dewlap seems to 

 be badly attacked while with others this portion of the body is about 

 exempt. Certain cattle again will be covered with flies and will lose 

 condition rapidly, while others are but slightly troubled. 



Fig. 15.— Cow-horn showing hand of resting flies— reduced. (Original.) 



On the horns the flies settle thickly near the base, often forming a 

 complete band for a distance of 2 inches or more. (See Fig. 15.) They 

 seem to prefer the concave side to the convex side of the curve of the 

 horn, probably for the reason that the cow can not scrape them off so 

 readily, and one cow was noticed in which they reached nearly to the 

 tip of the horn on the concave side of the curve only. 



Description. — For a description of the adult we may adopt that sent 

 us by Dr. Williston, which was drawn up from Virginia specimens 

 which we had sent to him, and which is substantially identical with 

 that published by him recently in Entomologica Americana (loc. cit). 



Male. — Length 3.5 to 4 mm . Sides of the front gently concave, its least width about 

 equal to one-fourth of tlie distance from the foremost ocellus to the base of the antenna? ; 

 in the middle a narrow, dark brown stripe; a single row of slender bristles on each 

 side. Antennae brownish red ; second joint slightly tumid ; third joint a little longer 

 than broad, with its inferior angle rectangular ; arista swollen at the base (which 

 is black), the pectination long. The narrow sides of the front, and the still narrower 

 facial and genial orbits silvery gray, with a slightly yellowish cast; facial fovhe 

 and cheeks blackish, the latter clothed with yellowish hair. Palpi black, the inner 

 surface and immediate base more yellowish ; gently spatulate in shape, nearly as long 

 as the proboscis, and extending two-thirds of their length beyond the oral margin. 

 Mesonotum sub-shining black in ground-color, but mostly concealed beneath a brown- 

 ish dust, which, on the pleura?, is more grayish. Abdomen with similar dust; in the 

 middle with a more brownish sub-interrupted stripe, and narrow darker posterior 

 margins to the segment. Femora black, or very deep brown, first two pairs of tibia? 

 and tarsi brownish yellow or luteous, the hind tibiae and tarsi blackish brown ; hiud 

 tibia? on the posterior surface with a noticeable, erect, subapical bristle; hind tarsi 

 about as long as their tibia?, the first three joints widened from their base to tip, so 



