256 BULLETIN 45, UNITED STATES NATIONAL MUSEUM. 



INOSTBMMA Ilaliday. 



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

 (Typo /. liosdi Jurine.) 



Head transverse, the Irons convex, the occiput often impressed, rarely 

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

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



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

 in the 9 terminating in a 4-jointed club, in $ with a 5-jointed club, the 

 last fuuiclar joint very minute. 



Thorax ovate, the mesonotum with U delicate impressed lines, often 

 obsolete anteriorly; the scutellum semicircular, subconvex, separated 

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

 slojiing, unarmed. 



Front wings with the submarginal vein abruptly terminating in a 

 stigma before attaining the middle of the wing. 



Abdomen in 9 ])ointed-ovate, subcompressed below, G-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 antenna^ must be carefully examined or they will be apt 

 to be coMfu>sed with those in closely allied genera. 



TABLE OF SPECIES. 



FKMALES. 



Head finely nii(Tosco])ically punctate, the thorax smooth, Hhinmg 2 



Head and thorax jmnctnlate or Khagreened, 8u)io[)a(jiie. 

 Vertex impressed at the middle, Irons with a median furrow. 

 Antenna- wholly hlack. 

 All eoxa^ and femora blaek (femora sometimes piceons), tibia; and tarsi yellow- 

 ish or brownish-yellow. 

 Scapuhe with a distinct median impressed line; metapleura with silvery 



pubescence I. ckessom Ashni. 



Scapuhe without an imiiressed line; tibiie fuscous; metapleura sericeous 



I. UORNI Ashm. 

 Vertex not impressed. 



Scape yellow. 



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



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



middle of thorax I. packardi Ashm. 



2. Vertex not impressed in the middle, frous without a median furrow. 



Antennae brown-black. 



CoxiP and legs dull rufous or piceous, trochanters, knees and tarsi pale. 



Metapleura finely striated, subsericeous I. kileyi Asbm. 



