18 HYMENOPTERA OF AMERICA. [PART I. 



Hab. South America. Cayenne. 



This t}*pc has very much the form of Zethusculus, on the part 

 of its clypens, and yet this form of clypeus appears in Z. spinipes. 



Division ZETHUSCULUS Sauss. 

 (Sadss. Vespides, I, 15 ; III, 118.) 



Second abdominal segment subsessile, or briefly pediculate (the 

 pedicle having at most a quarter the length of the segment). 

 Petiole lengthened, its inflation variable. 



Species small, ornamented with black and yellow. 



The insects of this group often have the clypeus armed with 

 two little separated teeth ; this part is in general moderately 

 rounded, but is at times lozenge-shaped, as in the division Heros, 

 with the lateral angles sharp {Z. spinipes) ; the head and thorax 

 are cribrose with great punctures, often rugose — the vertex offer- 

 ing frequently a corrugation which includes the antennas. The 

 thorax is generally short, and at times strongly angulate; the 

 metathorax in particular is sometimes convex as with the true 

 Zethus, and at times becomes angulate. The lateral ridges are 

 very distinct and the flanks beneath are smooth, compared with 

 the rest of the thorax. The posterior face of the metathorax is 

 convex, having two convexities or moderately flattened eleva- 

 tions, always velvety, less punctured than the rest of the thorax, 

 and in general covered with striae or wrinkles, silky upon the 

 dividing groove. Sometimes the posterior face of the metathorax 

 is concave and offers under the post-scntel a little excavation, 

 which recalls what one sees among certain Odynerinse. 'One 

 often perceives, also, two longitudinal carina} which start from the 

 angles of the post-scutel. 1 When these carina? become enlarged, 

 they produce ridges which border the cavity (Z. rniniatus). 



The petiole is quite variable; sometimes the knob is elliptical 

 and depressed, but more often the swelling is moderately cylin- 

 drical ; at first somewhat large, it then diminishes in size gradu- 

 ally to the extremity. In fine, it inclines to the campanular form, 

 whether lengthened pyriform, or clubbed and calling to mind the 

 HJumenes or even tubular ; but the other characters always suffice 



1 When I say : metathorax bicarinate, it is meant that the carina? exist 

 on the posterior face of the metathorax ; for as the lateral edges or ridges 

 are found on all the species, I do not mention them in the descriptions. 





