38 BULLETIN 45, UNITED STATES NATIONAL MUSEUM. 



This species has been taken I'rom the nests of the ant Formica rufi- 

 barbis by H. G. Hubbard, at Ft. Assiuiboiiie, Mont., and is also associated, 

 with ants under stones, at Washington, I). C, and at Beatty, Pa. 



Isobrachmm mandibulare sp. nov. 



9. — Lenj^th, 3.5""". Closely allied to T. rujivenfre and closelj' re- 

 sembling- it: Head brown, not so distinctly punctate, the outer tooth 

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

 legs yellow, the anterior tibia* at base dusky; middle tibife strongly 

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

 low, except the short petiole, which is black. The 13-jointed antenuje 

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

 of the head, much narrowed 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. myi'»tec(H)]tih(m, except as follows: The head is a little broader; the 

 antennte 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 dorsum of the metathorax, except at base, is smooth and 

 shining. 



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



Types in Coll. Ashmead. 



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

 ponotus pennsyJvanieiLSj May 27, 1883, by Mr. Tlieo. Pergande. 



Isobrachium rufiventre sp. nov. 



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

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

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

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

 the two outer large, equal, the inner one small. Antennse 13-jointed, 

 li times as long as the head; scape stout, not quite half as long as 

 the head; pedicel a little longer and stouter 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 Avide, separated from the mesonotum by a 

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

 out a scutellum, the lateral lobes obcordate. Middle cox», much larger 

 than either the front or hind coxie, pilose beneath, the tibiji? spinous; 

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

 about l.G">"' in length. 



$ . — Length, 3.G to 4"'"'. Head and thorax black, shining, sparsely 

 punctuate, the posterior margin of collar tinged with rufous. Anteniue 

 and mandibles pale rufous; legs, including cox;e, pallid or whitish. 



