472 C. R. OSTEN SACKEN'S PRODROME 



54. Tabanus rhombicus n. sp. 



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

 with a black, shining sul)callus ; foee whitish gray, -with white hairs ; palpi 3'ellowish, stout 

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

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

 gray lines ; pleuras gray. Al)domen 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 fiinge of grayish hair 

 expanded into a veiy faint triangle in the middle, and but sliglitly expanded on each side, 

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

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

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

 blackish, Avith a dense gray pollen and fringes of whitish hairs ; sometimes the first and 

 second segments are faintly reddish on the sides. Femora black, with gray pollen ; tibia? 

 and tarsi reddish In-own; front tibia? on their distal half and front tarsi dark brown (in 

 some specimens the tibia? and tarsi are much darker than in others). Wings subliyaline ; 

 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. 



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

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

 Columljia (Crotch) seem to belong to the same species. Two specimens from the British 

 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. rhomhlcus is very like T. mlcrocejihalus in its general appearance, Ijut 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 fen)ora are darker, etc. In most specimens the ocellar tubercle is 

 not denuded of pollen, although the eminence is 2:)lainly visible. The markings of the 

 abdomen aie very like those of 2\ microccjihahis, only the triangles of the intermediate 

 row are larger. 



List of the treviously described Species wnicn rejiaix unkxown", unrecognized or doubtful; 



ALL FROM NORTO AMERICA, NORTH OF MeXICO. 

 LiNNE. 



T. calois (Syst. Nat,, p. 1000, 0) is not giganieus DcGcci- {^Uneatus Fab.), although quoted by Dl^Gcci-; 



about the confusion existing with regard to tliis species, see Wiedemann, Auss. Zw. I, p. 135. The 



name is better left in abeyance for the present. 

 T. exccstuans (Sy.st. Nat., II, p. 1000, 8) ; see No. 10, T. mclanocerus Wied. 

 Fabricius. 



T. marginaUs (Syst. Antl., 00, 31). Very doubtful species; doubtful also wliether Wiedemann descril)ed 



the same species (compare Auss. Z\v., I, p. 166) ; my No. 20, T. viuax, seems to be the nearest to it. 

 Palisot-Beauvois. 



T. femigiireus (Tab. HI, f. 2, p. 221). 

 T. nelndosHs (Tabjll, f 4, 5, p. 222). 

 T.pcdUdus (Tab.ffi, f. 3, ]>. 100). 

 T.prilpinus (Tab. Ill, f. 1, p. 221). 



I cannot make out these specie j. 



