56 HYMENOPTERA OF AMERICA. [PART I. 



Geu. LABIS Sauss. 

 Labua Sauss. Reise d. Oesterr. Fregat. Novara. Hym., p. 3. 



Mandibles short, obliquely truncate, with 3-4 terminal teeth. 

 Maxillae elongate; their palpi elongate, 6-jointed. Labium 

 elongate, quadrifid, its palpi 4-jointed. Head rounded, swelled 

 at the occiput; clypeus rounded or truncate. 



Tliorax elongate ; its anterior angles sharp. 



Abdomen very slender; its petiole elongate, linear. Wings 

 somewhat as in Eumenes and Zethus. 



As the forms of the insects of this type are becoming various, 

 one could well think that the genus Labus might be fused into 

 G. Elimus, which only differs from this by another form of thorax 

 and petiole. Such differences occur under the species of the 

 genus Zethus. 



A. Petiole filiform at base, a little widened posteriorly ; its 



extremity margined by a transverse rounded cordon pre- 

 ceded by a transverse channel (as in Eumenes of Division 

 Omicron). Second segment sessile, elongate. Jletathorax 

 attenuated. Head inflated. Second cubital cell much pro- 

 longed at the basilar extremity ; the second recurrent vein 

 inserted after the middle of its posterior border. (Asiatic 

 type.) L. Spiniger Sauss., L. Humbertianus Sauss. 



B. Petiole linear, slender, p)rismatic ; 2d segment subpedicu- 



late. Tliorax elongate; metathorax short; prothorax 

 crested anteriorly. Second cubital cell equally dilated at 

 both extremities ; second recurrent vein inserted in the 

 middle of its posterior border. (American type.) 1 



1 The genus Elimus would make a third t} r pe: — 



C. Petiole linear, rather thick (very elongate, somewhat pyriform), biden- 



tate; its extremity marked with an impressed point ; head moderate; 

 thorax oval, not acute angled anteriorly ; metathorax rounded ; the 

 2d segment elongate, rather attenuate posteriorly ; 2d cubital cell in 

 a regular truncate triangle; second recurrent nerve inserted in the 

 middle, or a little before the middle, of its posterior border. 





