MONOGRAPH OF THE NORTH AMEKICAN PKOCTOTUYPH)^. 37 



as thirk, t\w last Joint twi<'»^ as loiij; as the penultimat*'. Thorax 

 aiiti'iiurly narrowed, tluH-oUar brownish, thr iiu'sonoluin with 1 «;r<M>ves, 

 the iniihlh' furrows nioiv or less iridistiiut ami al)lne\ iated i)osterioily, 

 tlie stutelluiu with a transverse furrow at base, the nietathorax twiee 

 as lonj; as wide, rujjulose, with a median carina. Winjjs subhyaline, 

 the stijjina an<l nervnres pale brownish yellow, the transverse median 

 nervnre evected. Lejis brownish-yellow, the posterior vox-.v. som(>what 

 dusky. Abdomen oval, piceous-black, the apical eiljjes of the segments 

 testaceous. 



IIahitat.— Spokane Falls, Wash. 



Type S in Coll. Ashnu'ad. 



The larjfcst 8pe<ies in the {jenus known to me, and readily dis- 

 tinguished by the evected tran8vers«i median nervnre. 



Isobrachium myrmecophilum s)i. ii<»v. 



(Pl.ii.Fi«H.3, <?; 4, 9) 



9. — Length 3""". Head twice as long as wide, black or piceous, 

 shining, punctate, and sparsely covered with a dusky pubescence. 

 Eyes and ocelli entirely wanting. Mandibles rufous, with .'{ teeth. 

 Anteniue short, 13-,jointed, rufous, the scape nearly one-half as long as 

 the tlagellum ; pedii-el small, rounded; the tlageUar joints, except the 

 last, all transverse, the last oblong, more than twice as long as the 

 preceding. Thorax brownish-piceous, highly polished, with a few 

 scattered punctures; the i)rothorax is greatly elongate, 2^ times as 

 h)ng as wide, with nearly parallel sides rounded otf anteriorly, the 

 anterior depression of the collar pale rufous, finely transversely acicu- 

 late ; prosterimm black ; mesouotum separate<l from the pronotum by 

 a distinct furrow; the niesothorax is sei>arated from the nietathorax by 

 a strong constriction, trilobed but without a scutellum ; the metathorax 

 is scan'ely larger than tlie middle mesothoracic lobe. Legs pale brown- 

 ish-yellow, stout, the middle tibia'- strongly spinous; all tarsi longer 

 than their tibia;. Abdomen oblong oval, brownish pice(ms, much 

 shorter than the thorax, smooth, impnnctured, sparsely pilose. 



i . — Length 3 to 3.5'""'. Black, punctate; head oblong, with a thim- 

 ble-like punctuation, mandibles rufous, antenuiB and legs pale brown- 

 ish-yellow, collar pale anteriorly; abdomen jHceous, paler at sutures. 



Antenna; 13-jointed, extending to base of scutellum, the flagellar 

 joints not quite twice as long as thick. Thorax with 4 grooved lines, 

 the middle pair parallel, abbreviated posteriorly; those on the shoulder 

 abbreviated anteriorly. Metathorax long, minutely shagreened with 

 a central longitudinal carina. Wings hyaline, the stigma and sub- 

 costal nervure pale brownish, the other nervures subhyaline; the radius 

 is very long, almost reaching to the apex of the wing, the transverse 

 hiedian nervure, oblique, interstitial with the basal. 



Habitat. — Pennsylvania, District of Columbia, Montana, and Ari- 

 feona. 



Types in Coll. Ashmead. 



