38 BULLETIN 45, UNITED STATES NATIONAL MUSEUM. 



This species lias been taken from tlie ne.sts of the ant Formica rufi- 

 barbishy II.(l. Ilubbanl, at Ft. Assiniboine, Mont., and is also associated 

 with ants under stones, at Wasliinjiton, D. C, and at Beatty, Pa. 



Isobrachium luandibulare Hp. nov. 



9 . — Length, S..")""". Closely allied to /. rifjiventre and closely re- 

 semblin*;^ it: Head brown, not so distinctly imnctate, the outer tooth 

 of mandibles longer, the inner tooth subobsolete; eyes entirely wanting ; 

 legs yeHow, the anterior tibia' at base dnsky; middle tibiae strongly 

 spinous. The abdomen is long and measures 2""" ; it is brownish-yel- 

 low, except the short petiole, whi<'h is black. The 13-jointed antenme 

 are nearly twice the length of the oblong head; scape half the length 

 of the head, much uarrowed at base: last flagellar joint twice as long 

 as the penultimate, rounded at tip. 



S . — Length 3.6"'™. Black and agreeing in color and structure with 

 I. myrmecophllum, excei)t as follows: The head is a little broader; the 

 antenna? a little stouter and shorter, the flagellar joints scarcely 1^ 

 times as long as thick; mandibles very large and broad, brownish-yel- 

 low; there are no teeth within after the second tooth which is small, 

 while the doisum of the metathorax, except at base, is smooth and 

 shining. 



Habitat.— District of Columbia and Fort George, Fla. 



Types in ('oil. Ashmead. 



Both, sexes of this species were taken together in the nests of Cam- 

 ponotiis penusyhmnieus. May 27, 18&], by Mr. Theo. Pergande. 



Isobrachium rufiventre sp. nov. 



9 . — Length, 3.5 to 4""". Head variable, from piceous to black, about 

 twice as long as wide, with scattered punctures; eyes wanting; thorax 

 brown; antenna', legs, and abdomen brownish-yellow. The mandibles 

 are large, crossing each other at tips, and terminate in 3 black teeth, 

 the two outer large, eipial, the inner one small. Antenuie 13-jointed, 

 1^ times as long as the head; scape st<mt, not quite half as long as 

 the hea<l; pedicel a little hmger and st<mter than the first flagellar 

 joint, the following joints to the last, wider than long, the last conic. 

 Prothorax narrower but longer than the mesothorax, rounded before, 

 more than twice as long as wide, separated from the mesonotum by a 

 deep groove; mesothorax subcordate, as wide as long, trilobed, with- 

 out a scutellum, the lateral lobes obcordate. Middle coxa^, much larger 

 than either the front or hind coxte, pilose beneath, the tibiaj spinous; 

 anterior tibia? with only a few spines. Abdomen long, pointed at apex, 

 about l.G""" in length. 



S . — Length, 3.6 to 4""". Head and thorax black, shining, sparsely 

 punctuate, the jw&terior margin of collar tinged with rufous. Antenna? 

 and mandibles pale rufous; legs, including (;oxje, pallid or whitish. 



