32 GENERA OF IIYMENOI'TERA. 



24. — Hast' of sciitfllmn. iinniodiiiti'ly at tlu' thickciu-d aiitciidr jiiai-irin, with two 

 small traiisvcTSf fovi-a-. or better with a small and slKtrt transverse 

 groove, feebly interrupted medially, and separated externally by a lon- 

 jritudinal earina from tlie very variable triansnlar lateral fovea, these 

 two iimgitudinal ridges are not, as usual, parallel, but diverge po.steri- 

 orly : anteniife 14-jointed, long and slender, third joint twice, or nearly 



twice, as long as fourth : lin Compositie galls) 5. ••Timaspis ^layr. 



Base of scutellum with two very sharply .separated fovese, which are more 

 or less triangular or quadrangular, and often very lai'ge ; the large tri- 

 angular lateral fovea not extending u))wavds and inwards, but lies on tin- 

 free side of scutellum ; antennne 13-14-jointed, third joint shorter, or a 

 little longer, than fourth ; marginal cell short, or moderately long, in the 

 last case the third antennal joint is no longer than fourth : (in galls of 

 various herbs and bush-like plants) 7. • Aulax Hartig. 



"i-i.— Base of scutellum with two sharply separated fovea"; metathorax with 

 straight, parallel ridges, rarely distinctly, but not sharply .serrulate, or 

 inferiorly somewhat divergent (as in many European aganious forms); 

 parapsidal groovesshar]) and entire, often indi.stinctly defined anteriorly, 

 mesothorax rarely transversely wrinkled; antenna; and tibia- not fim- 

 briate : third joint of antennse longer than fourth ; these joints are equal 



in the American A. tiiliicohi ; (in Uak-gallsj 17. Andricus Hartig. 



Otherwise formed; metathoracic ridges (except in Loxaulus) not .straight 

 and ]iarallel ; base of scutellum with a transverse furrow, or with two 

 shari)ly limited foveie ; in the last case the metathoracic ridges in the 

 middle elevation of metathorax are strongly arcuate or angularly s<;pa- 

 rated 2(i. 



26. — Claws of posterior tarsi entire; anteniue and tibia- not fimliriate; me.sotho- 



rax glabrous 27. 



Claws of ])osterior tarsi hidentate ; mesothorax often abundantly hairy; 

 scutellum usually with an uninterrupted transverse groove 30. 



27.— Parapsidal grooves of the polished or moderately deeply wrinkled meso- 

 thorax very shaiply defined ; anteniut with 14 !."> free joints, the third 



as long, or longer than fourth 2tt. 



Parapsidal grooves of the alutaceous mesothorax shallow, feebly or not at 

 all impressed anteriorly; antenme with l.'J 11 free joints, third and 

 fourth etjual ; middle ai-eji of metathorax with a more or less distinct 

 median longitudinal carina 29. 



28. — Base of scutellum with two distinctly separated fovea*; the moderately 

 thick antenna- with 14 free joints; mesothorax jwlished ; body yellow 



or reddish yellow; (in Oiik-galls) 22. Biorhiza Westw. 



Base of scutellum with a broad transvei-se groove ; the not thick antennai 

 14-15-jointed ; (in Oak-galls) 2(). 'Dryocosmus Gir. 



29. — Cheeks without any, or only a feeble groove; antenna; 14-jointed ; head not 

 broader liehind the eyes; scutellum at ba.se with two fovea- ; metathorax 

 with two median, angular, divergent ridges; (in Oak-galls). 



24. ''Plag-iotrochus Mayr. 



Cheeks with a sharp furrow ; antenna- with Hi sharjily defined joints; bead 



distinctly broader liebind the eyes; base of scutellum with an arcuate 



transverse groove; metathoracic ridges almost straight and parallel ; (in 



N. Am. Oak-galls) 2.">. Loxaulus .Mayr. 



