OF THE TABANID^ OF THE UNITED STATES. 467 



49. Tabanus socius n. sp. 



Female. Is very like T. affinls ; it will be sufficient to indicate the differences. Smaller 

 in size, being only 15-16 mm. long ; the coloring of the dark portions is of a lighter gray, 

 somewhat slate color ; the second joint of the palpi is shorter and much stouter at the base, 

 the color of the palpi is paler ; antennas of a lighter red, last joint Ijut very little infuscated 

 towards the end ; the yellowish brown at the base of the front tibine is more extended here, 

 in many specimens the tibia3 are black at the tip only ; the front is distinctly coarctate 

 anteriorly, but narrower than in T. ajfinis ; the linear prolongation of the callus in most 

 specimens forms a slightly elevated ridge, sometimes nearly reaching the ocellar tubercle. 

 Length, 15-lG mm. I have about a dozen of specimens from the northwestern parts of 

 the Hudson's Bay Territory (Fort Simpson, Kennicott), agreeing in these characters; also 

 two specimens from Illinois. All these specunens have the antealar tubercle reddish. 



This species is most remarkably like the common European T. tropicus ; however, a 

 specimen of the latter in the Museum of Comparative Zoology, labelled by Dr. Loew, has 

 a somewhat broader front, the antealar tubercles black, the antennas somewhat more brown- 

 ish at the tip. I sent a specimen of T. socius to Dr. Loew, who declared it to be different 

 from his T. trojyicus. 



There seems to be a good deal of uncertainty connected with the European species of 

 this group. Dr. Schiner, Fauna Austr., Diptera, I, p. 30-31, makes trojncus (non Linne) 

 Loew = solstitialis (Meig.) Schiner; irojiic^is (Linne) Schiner = /invV/ws (non Fallen) 

 Loew; and btriclus Fallen (non Loew) = /ro^j/c^s Panzer. Loew observes (Yerli. Zool. 

 Bot. Ges., 1858, p. 586), in a note to the description of T. frojnciis, that " the difficulties 

 concerning this species are increased by the flict that there are evidently several other 

 species yet coming in conflict hero, which cannot be distinguished w'ith certainty in single 

 specimens." Similar difficulties probably exist among the Noi'th American species. 



T. vicimts Macq., Dipt. Exot., I, 1, p. 143, 4-4 (Carolina) apparently belongs in this 

 relationship. 



50. Tabanus septentrionalis. 



Tabanus sejJtentrioyialis Loew, Vcrli. Zool. Bot., 1858, p. 593. 



I translate Dr. Loew's description : 



'•Female. Ex-cinereo nigricans, abdomine trifariam cinereo maculato. maculis lateralibus 

 obliquis, margin! postico vix contiguis, tibiis obscure testaceis, ocnlis hirtis, trifasciatis, palpis 

 nigropilosis, antennis nigris, frontis callo infero et linca longitudinal! media atris. Long. 

 Corp. 6 lin. ; long. al. 5^ lin. 



" (Cinereous blackish, abdomen with three rows of cinereous spots, the lateral ones 

 oblique, hardly touching the hind margin, tibia? dark testaceous, eyes hairy, with three 

 stripes, palpi with black hairs, antennse black ; frontal callosity and a longitudinal line in 

 the middle, black; length 13 mm.) 



'' The great uniformity which prevails through the whole dipterous fauna in the arctic 

 regions, and the resemblance between T. sejjfentrionalis and the two preceding species,^ 



^T. quatuor/mtatus Slt-ig. and nigricornU Zett. 



