330 MEMOIRS OF THE CARNEGIE MUSEUM 



Trire III. Sphegigcisterini. 

 The species tallini,Mn tliis triKe are easily recognized Ijy the mucli longer and 

 more slender marginal vein. They differ from the others also in habits, the majority 

 of the species being parasites of dipterous insects, and especially of the gall-making 

 species Ijelonging principally to the faiuily O'chloiinjiiilx. 



TABLE OF GENERA. 



1. Females 2 



Males Ki 



2. Abdominal petiole longer than the hind coxce 3 



Abdominal petiole shorter than the hind coxa;, or at least never longer 7 



3. Head with the cheeks compressed, (he vertex not very narrow 4 



Head sublenticular, the cheeks rounded, the vertex narrow. 



Pronotum large, quadrate, mesonotum flat, with complete parapsidal furrows ; second abdomi- 

 nal segment very large, occupying fully two thirds of the whole surface of the abdomen, the 

 following very short Syntomopus Walker (type S. ihoracicus Walk.). 



4. Mesothoracic furrows incomplete, abbreviated posteriorly ov only distiuL-t anteriorly 5 



Mesothoracic furrows complete, distinct. 



Scutellum with a cross-furrow before the apex ; abdomen short oval, keeled beneath, the second 

 and third segments very large, the second broadly emarginate at apical margin. 



Merismus Walker (type M. megapterus Walk.). 



Siiitelluni convex, iritliuiil a cross-furrow before the apex, the second segment large, occupying 

 a little more than lialf the whole surface of the abdomen, the apical margin straight, not 

 emarginate Acroclisis Fijrster (type A. nigricornis Forst.). 



5. Metanotum usually smooth, but always with a median carina (except sometimes in Polycyrtus), the lateral 



folds also usually present 6 



Metanotum punctate, without either a median caiina or lateral folds. 



Scutellum convex, without a cross-furrow before the apex ; abdomen with the second and third 

 segments very large ; .sometimes the abdomen is triangulate as in Perilampvs. 



Trigonogastra Ashmead, g. uov. (type T. aurata Ashm.). 

 G. Seutelhiiii wilh a delicate cross-furrow before the apex ; abdomen with the second and third segments 



very large, the latter about one third the length of the second Sphegigaster Spinola 



(type »S'. paUicornig Spin.). 



Scutellum without a cross-furrow before the apex or the furrow is subabsolute ; abdomen with the 



second segment very large, occupying half or a little more than half the whole surface, the following 



very short, often retracted Cryptoprymna Forster (type Prosodes atra Walker). 



7. Mesothoracic furrows incomplete, much abbreviated, or indicated only anteriorly 8 



Mesothoracic furrows complete, distinct, rarely only two thirds the length of the mesonotum 13 



8. Metanotum not broad, and with a more or less distinct median carina, or at least the carina is indicated 



basally ^ 



Metanotum broad, punctate, ivithout a median carina V genus. 



9. Second abdominal segment at apex broadly and usually deeply, semicircularly emarginate 10 



Second abdominal segment at apex not broadly and deeply emarginate, straight or at the most w ith 



only a slight sinus 11 



