OF THE TABANID.E OF THE UNITED STATES. 373 



The descrijDtion of C. dlvlsus Walker, seems to agree with this S2)ecies, except the impor- 

 tant statement " chest and abdomen clothed with dark tawny hairs," of which there is no 

 trace in C. atroj^os. 



2. Chrysops excitans. 



Chrysops excitans Walker, Dipt. Saunders, p. 72. 



2 . Apex of the wings hyaline ; proximal half of the two basal cells infuscated ; two or three basal segments 

 of the abilomen yellowish on the sides ; a distinct gray or yellowish-gray triangle on the second segment. 



Length, 10-12 mm. 



3 . Body altogether black. Coloring of the wings darker than in ? , with a fenestrate hyaline spot in the 

 middle. Length, 10-11 mm. 



Female. The black, shining facial callosities prolonged in front and converging above 

 the month ; between them, a short pointed stripe of fulvous pollen ; similar stripes separate 

 the callosities from the black, shining cheeks ; frontal callosity large, black, shining, separa- 

 ted from the black spot on the vertex by a fulvous crossljand attenuated in the middle ; the 

 orbits and the root of the antennae show narrow margins of the same fulvous jjollen. An- 

 tennae : first joint reddish-black at tip ; second joint darker, almost black, although showing 

 traces of red, especially on the under side ; third joint black. Thorax blackish, clothed with 

 fulvous hair, especially dense on the pleurae ; on the dorsum the beginning of a broad, Imt 

 faint gray stripe is visible anteriorly ; it is more or less distinctly margined with lines of 

 yellowish pollen on each side, and is divided longitudinally by a faint, black line. Abdomen 

 black, the sides of two, sometimes three, basal segments, yellowish tawny ; the posterior 

 margins of the second, third and fourth segments show, on the black color in the middle, 

 triangles beset with golden hair; that on the second segment is especially large and 

 distinct; (in rubbed specimens this triangle is grayish or yellowish, the latter in such 

 specimens where the yellow on both sides is continued along the posterior margin). The 

 third and following abdominal segments are black, clothed with golden-yellow hair on their 

 surface, as well as on their posterior margin. Venter yellowish-tawny at the base, black 

 towards the tip, the black more or less encroaching upon the yellow along the central line 

 in tlie shape of spots of different sizes in different specimens. Legs black, with a vestige 

 of brownish at the basis of the tibiae and of the four posterior tarsi. Wings with a hya- 

 line apex ; the two basal cells infuscated up to the middle ; the crossband does not reach 

 the posterior margiir and does not fill out the fourth posterior cell ; the inner end of the 

 fifth posterior cell is infuscated, although less dark than the crossband ; anal cell and anal 

 angle have a slight brownish tinge ; the fifth vein, up to the crossvein, is brown in older 

 specimens. A more or less distinct whitish halo along the distal margin of the crossband, 

 sometimes hardly apparent. 



The coloring of the abdomen of the female is very variable in the extent of the yellow ; 

 in some specimens the sides of the third and even of the fourth segments are of that color ; 

 in one specimen (British Possessions, Scudder) the yellow is the prevailing color on the 

 abdomen, reaching the fifth segment, and leaving only a square black spot in the middle 

 of the first, fourth and fifth segments, and a bilobed spot on the second and third. The 

 coloring of the venter shows more or less yellow, in proportion to the ujiper surface ; in 



MEJIOIKS BOST. SOC. KAT. HIST. VOL. n. 



