OF THE TABANID^ OF THE UNITED STATES. 377 



and denser yellow, sometimes almost fulvous hairs near the root of the wings and on the 

 upper part of the pleurag. Abdomen black ; first and second segments more or less yellow- 

 ish on the sides ; all the segments, except the first, with a naiTOw gray border posteriorly, 

 which expands into a distinct triangle on the first two segments, and a less distinct one 

 on the third. In well preserved specimens these gray margins and triangles are clothed 

 with a golden-yellow pubescence. On the venter the segments are covered with gray 

 pollen posteriorly, and clothed with yellowish hairs. Legs black, the brownish color at the 

 root of the four posterior tarsi hardly perceptible. Wings : general coloring of the hya- 

 line portion dingy grayish ; the brown portions but moderately dark ; costal cells bro-\vn, 

 first basal cell infuscated on its proximal half; second basal cell almost hyahne, except its 

 extreme proximal end ; fifth longitudinal vein more or less clouded Avith brownish, which, in 

 some specimens, forms a distinct Ijorder inside of the second basal cell ; the crossband does 

 not reach the posterior margin, and fills obliquely the jjroximal half of the fourth posterior 

 cell ; a pale Ijrown cloud fills the proximal end of the fifth posterior cell. The space along 

 the costa between the crossband and the tip of the wing is faintly tinged with brown. 

 The halo along the distal margin of the crossband is indistinct, although the apical ^^ortion of 

 the wing is rather grayish. 



Hah. White Mountains, N. H. Nine female specimens. The yellow color on the sides 

 of the abdomen has more or less extent in different specimens ; sometimes it is confined to 

 the anterior corners of the second segment and is hardly perceptible on the first ; such spec- 

 imens have the first antennal joints almost black. On the average, the yellow on the abdo- 

 men has much less extent than in C. excitcms, and only extreme cases in both species show 

 any approach to each other. C. sordldus is easily distinguished from all the preceding spe- 

 cies by the gray posterior margins of the abdominal segments. Although the hairs upon 

 them can be rubljed off, the gray margins and triangles remain, which is not the case in the 

 other species of this group. (Only the triangle on the second segment in C. excitans, and 

 perhaps in C. niitis, shows the same permanence.) 



Mr. Walker's description of Ohrysops niger is based on specimens of the present species, 

 as the description of the abdomen undoubtedly proves. 



7. Chi-ysops niger. 



Chrysops niger Macquart, Dipt. Exot., I, 1, 161, 10. 

 ? Chrysops carbonarms Walker, List, ete., I, p. 203, Variet. (3. 



? . Apex of the wings hyaline; second basal cell altogether hyaline; face ferrnginons in the middle. 

 Length, 6|-8 mm. 



Female. The black, shining facial callosities are separated by a large, shining, yellowish- 

 ferruginous spot extending from the antennae down to the mouth ; the black, shining cheeks 

 are separated from the callosities above them by the usual stripe of fulvous pollen ; the 

 pollen on the front is grayi.sh-yellow. Antennae : first joint reddish, often blackish at tip ; 

 second, blackish, mixed with reddish; third, black, reddish at base. Thorax with a broad 

 greenish-gray poUinose stripe in the middle, divided longitudinally by a blackish line ; its 

 sides are more distinctly gray, assuming the appearance of two gray lines ; on each side of 



MEMOIRS BOST. SOC. NAT. HIST. VOL. a. 95 



