22 BULLETIN 1218, U. S. DEPARTMENT OF AGRICULTURE.. 



margins of segments 2 and 3, so as to appear jagged ; the red on the sides of 

 segments 2, 3, and 4 is clothed with a scarce and very minute golden-yellow 

 pubescence, in the shape of faint, oblique spots ; it also forms a fringe on the 

 incisures. 



T. phaenops is very like T. sonomensls, but it is usually a little smaller, the 

 front is narrower, the bifurcation of the third vein is not clouded ; in most, but 

 not in all, specimens, the red on the sides of the abdomen is less extended, 

 leaving a broader black stripe in the middle, which is expanded at the abdomi- 

 nal incisures, and therefore appears jagged. In shape, the abdomen is more 

 elongated, with more parallel sides. In life, this species is easily distin- 

 guished by the color of its eyes, which are of a very bright green, with com- 

 paratively narrow purple cross-bands, much narrower than the green intervals 

 between them; no purple in the upper and lower corners of the eye (at least, 

 in the specimens observed). 



Had. — Webber Lake, Sierra County, Calif., July 27. Four females. Two speci- 

 mens from Fort Bridger, Wyo., August 4, seem also to belong here. 



Distribution. 



Professor Hine {3) gives the distribution as " from Alaska and 

 British Columbia to California, and specimens are also at hand from 

 Wyoming and Colorado." In California it was found very abundant 

 east of the Sierra Nevada Mountains as far south as near Bishop and 

 as far north as Alturas. Specimens were taken north of Bishop, and 

 at Bridgeport, Topaz, and Alturas, Calif. In Nevada the species is 

 abundant- near Deeth and at Wellington. 



Abundance. 



This is the most abundant horse-fly in Antelope Valley and at 

 Bridgeport and Alturas, Calif. It is reported to be exceedingly 

 abundant and a pest of great importance on the range north of 

 Bishop, Calif. It is the most abundant species in Antelope Valley 

 and at Deeth, Nev. In Antelope Valley these flies were more abun- 

 dant in 1915 than during the four following years. They were 

 •fairly abundant in 1918, but comparatively scarce in 1919. The 

 earliest seasonal appearance of the species was May 19, in 1918. 

 As a rule they become gradually more abundant until the middle 

 of July. They are abundant until the latter part of August, when 

 usually there comes a marked reduction. They become gradually 

 scarcer and few are seen after October 1. The latest seasonal ac- 

 tivity observed was on October 19, in 1916. Only one specimen was 

 observed. After the first of September, as a usual thing, they give 

 very little trouble. 



Habits of the Adult Female, 

 feeding habits. 



Hosts attacked by Tdbanus phaenops are horses, mules, and cattle. 

 Occasionally one will attempt to feed upon man. They begin soon 

 after sunrise and gradually increase in numbers until about 10.30 

 a. m. From then until 4 or 5 p. m. they are abundant. The horses 

 and cattle congregate in separate bunches about 10.30 a. m. The 

 horses continually fight the flies with mouth, feet, and tail, not ven- 

 turing to feed at all until about 4 or 5 p. m. 



When these insects attack, they bite mostly on the shoulders, neck, 

 and face, around the breast, and below the elbow (fig. 15). The 



