30 GENERA OF HYMEXOPTERA. 



A suture between nusothorax and scutellum, the latter with a distinct, more 



or less elevated carinate anterior margin 13. 



13. — Abdomen, especially from third to last segments, entirely or at least on lower 

 two-thirds, covered with a rich silky pubescence, also head, thorax and 

 legs; head much widened behind the eyes: mesothoracic ridges parallel 

 or nearly so; aganious form 14. 



Abdomen without silky pubescence, almost or entirely without hairs 15. 



14. — Claws of iKjsterior tarsi entire ; antennte long and slender, last joint .some- 

 what thicker than second, distinctly thicker than long ; parapsidal 

 grooves not impressed anteriorly ; scutellum as long as wide, its base 

 with an entire transvei-se furrow formed by a fine carina and open at 

 each end ; fin galls of Qiiercus cerris) 19. •■Aphelonyx Mayr. 



Claws of posterior tarsi bidentate ; antennse thicker and shorter, second 

 joint as long or longer than thick ; i«rapsidal grooves entire ; scutellum 

 somewhat broader than long, the base with two transverse furrows, each 



closed externally by a carina; (in Oak-galls) 18. Cynips Linn. 



l."*. — Cheeks with a sharp furrow; antenuie distinctly 14-jointed, tiagdluni mod- 

 erately .slender, more so at tip than at middle, the joints at lea.st IH as 

 long as thick; parapsidal grooves sharp and entire; nie.sothorax pol- 

 ished ; the two dei)res.sions at base of scutellum .separated from each 

 other by a sharp carina ; metathonix above with two parallel ridges, the 

 disc strongly arcuate ; second joint of posterior tarsi as long as apical 

 joint, claws indistinctly bidentate ; head and thorax black, alMlomen 

 yellowish red ; sexual form ; (in Oak-galls). ..21. • Trigonaspis Hartig. 



Otherwise formed ; apical third of antennte not thinner than at the middle, 



(except in one .species of Timaspis) 16. 



lf>. — Entire body nearly everywhere jwlished and very shining, of a reddish 

 yellow color ; cheeks shorter than half of the eyes; antenuie with 13 

 free joints, those of apical half distinctly thicker than joints 3-3; par- 

 apsidal grooves sharp and entire ; base of scutellum with a transvei-se 

 groove, which is divided in two by a sharp median carina, di.sc of scu- 

 tellum laterally and behind with a very distinct marginal ridge ; nieta- 

 thorax with two angularly curved ridges, divergent mediulh' ; abdomen 

 strongly compre.'.sed, lenticular, acute above and below: marginal cell 

 long and open at the margin of the wing ; claws of posterior tarsi entire ; 

 (in leaf-galls of Qiiercus cerris) "2.3. ^Chilaspis Mayr. 



Body not at all yellow, polished, also scutellum, the disc of which is mar- 

 gined 17. 



17. — Face, occiput, mesothorax and mesopleune polished, not hairy, blaek ; an- 

 tenna- with 13-14 distinct joints ; prothorax with two f<ivea> near the 

 middle, immediately liehind anterior margin; ba.se of .scutellum with 

 two well-defined foveffi ; metathorax with two parallel ridges; second 

 and third segments of abdomen united, with or without furrow; claws 

 of po.sterior tarsi entire ; (in Potentilla-galls)..H. -sXestophanes Fiirst. 



Otherwise formed 18. 



is. — Abdomen with second and third segments united, without or rarely with a 

 trace of a separating suture, so that only six free segments appear, seg- 



ments 2-3 forming almost the entire abdomen ; cheeks without furrow ; 



the front laterally striped; head not wider behind the eyes; prothorax 

 not narrowed medially ; ba.se of scutellum with two .shari)ly marked 



