256 BULLETIN 45, UNITED STATES NATIONAL MUSEUM. 



INOSTEMMA Haliday. 

 Ent. Mag., i. ]..270 (1833); FOrster, Hym. Stud., ii, p. 107 (1856). 

 (Tyi)C /. Jiosrii .In lint'.) 



Head transverse, the frons convex, the ()ccii)nt often impressed, rarely 

 distinctly margined; ocelli 3 in a triangle, tlie lateral being nearer to 

 the margin of tlie eye than to the front ocellus; eyes rounded. 



AntenniTB inserted just above theclypeus, 10-jointed, the scape clavate, 

 in the 9 terminating in a 4-joiiited club, in S Avith a 5-jointed club, the 

 last funidar joint very minute. 



Thorax ovate, the mesouotum with 2 delicate impressed lines, often 

 obsolete anteriorly; the scutellum semicircular, subconvex, separated 

 from the mesonotum by a straight impressed line ; the metathorax short, 

 sloping, unarmed. 



Front wings with the submarginal vein abruptly terminating in a 

 stigma before attaining the middle of the wing. 



Abdomen in 9 i)ointed-ovate, subcompressed below, 0-jointed, the first 

 segment always with a horn extending forward over the thorax, the 

 second very long, the following very short, about equal in length; in S 

 shorter, oblong oval, with the tip rounded, 7-jointed. 



Legs clavate, the tibial spurs 1, 1, 1, the basal joint of posterior tarsi 

 about three times as long as the second, 2 to 4 subequal, the last as long 

 as the second. 



The horn like structure at the base of the abdomen renders the females 

 in this genus easy of recognition, while in the males the position of the 

 ocelli and the anteniiic must be carefully examined or they will be apt 

 to be confused with those in closely allied genera. 



TABLE OF SPECIES. 



Head finely microscopically punctate, the thorax smooth, shining 2 



Head and thorax punctnlate or shagreened, subopaque. 

 Vertex impressed at the middle, frons with a median Inrrow. 

 Antenna' wholly black. 

 All coxie and femora black (femora sometimes piceous), tibiie and tarsi yellow- 

 ish or brownish-yellow. 

 Scapuhc with a distinct median impressed line; metaplema with silvery 



pubescence I. CUESSONI Ashm. 



Scapulic without an impressed line; tibiae fuscous; metapleura sericeous 



I. HOUNi Ashm. 

 Vertex not impressed. 

 Scape yellow. 

 All coxa- black, club of femora fuscous, rest of the legs brownish-yellow. 

 ScapuUe without an impressed line, abdominal horn extending only to the 



middle of thorax I. packardi Ashm. 



2. Vertex not impressed in the iiiiddh', frons without a median furrow. 

 Antenna; brown-black. 



Coxa; and legs dull rufous or jiiceous. trochanters, knees and tarsi pale. 

 Metapleura finely striated, subsericeous I. uileyi Ashm. 



