472 C. R. OSTEN SACKEN'S PRODROME 



54. Tabanus rhombicus n. sp. 



Female. Front compiiratively broad, gray, slightly coarctate anteriorly ; callosity black, 

 with a black, shining subcallus ; face whitish gray, with white hairs ; palpi yellowish, stout 

 at base, clothed with short, black hairs ; antenna? more or less dark reddish, the third joint 

 black, more or less red at base, its npper angle very shallow. Thorax grayish black with 

 gray lines ; pleurae gray. Abdomen grayish black, with gray spots, as follows : on the 

 second and third segments an equilateral triangle in the middle, and an oblique one on each 

 side; the following segments show a grayish hind margin, with a fringe of grayish hair 

 expanded into a very faint triangle in the middle, and but slightly expanded on each side, 

 where the lateral triangles should lie ; (all these markings seem to rub off very easily ; 

 especially the intermediate row of triangles, formed of hairs only, with hardly any gray 

 pollen under them) ; the sides of the second segment sometimes fliintly reddish. Venter 

 blackish, with a dense gray j^ollen and fringes of whitish hairs ; sometimes the first and 

 second segments are faintly i-eddish on the sides. Femora black, with gray pollen ; tibise 

 and tarsi reddish brown ; front tiljite on their distal half and front tarsi dark brown (in 

 some specimens the tibite and tarsi are much darker than in others). Wings subhyaline ; 

 stigma brown ; a very faint, small cloud on the bifurcation of the third vein and at the base 

 of the second posterior cell ; first posterior cell broadly open. Length, 13-15 mm. 



HaJ). Colorado Mountains (Lieut. W. L. Carpenter, J. Ridings). I have six specimens, 

 only one of which can be called tolerably well preserved. Four specimens from British 

 Columbia (Crotch) seem to l^elong to the same species. Two S2:)ecimens from the Bi-itish 

 Possessions (Saskatchewan or Lake Winnipeg, S. H. Scudder) may perhaps also belong 

 here ; they are smaller, somewhat narrower, and the abdomen more reddish on the sides. 



T. rJiombieus is very like T. microcephalus in its general appearance, but its head is 

 comparatively larger, the front broader, the subcallus (in all my specimens at least) is 

 denuded, the bifurcation of the third vein shows a little cloud, which, although faint, is 

 sufficiently distinct, the femora are darker, etc. In most specimens the ocellar tubercle is 

 not denuded of pollen, although the eminence is plainly visible. Tlie markings of the 

 abdomen are very like those of T. mkroce^jhahis, only the triangles of the intermediate 

 row are larger. 



List of the pkeviously described Species wriicn ke-Main" uxknowx, uxrecogxized ok doudtful; 



ALL FROM NoKTU AmEUICA, NORTH OF JMeXICO. 

 LiNNE. 



T. ccdois (Syst. N:it., p. 1000, G) is not gir/anteus DeGeor { — lineatus Fab.), altliouyii quoteil by DeGccr; 

 about the confusion existing with regard to tliis species, see Wiedemann, Auss. Zw. I, p. 1.35. The 

 name is bettor left in aljej'aiiee fov tlie jiresent. 

 T. cxcestuans (Syst. Nat., II, p. 1000, 8) ; sec No. 10, T. nulanoccrus Wiod. 

 Fabricius. 



T. mart/iiuilis (Syst. Antl., 09, ?>1). Very doubtfiil species; doubtful also whether Wiedemann described 

 the same species (compare Auss. Zw., I, p. IGG) ; my No. 20, T. vioax, seems to be the nearest to it. 

 Palisot-Beauvois. 



T. ferrwjinexis (Tab. Ill, f. 2, \^. 221). 

 T. nehulosuft (Tab. Ill, fl 4, 5, p. 222). 

 T.i'allidas (Tab. Ill, f. .3, p. KlO). 

 T.2->alinnus (Tab. Ill,- f. 1, p. 221). 

 I cannot make out these species. 



