270 HYMENOPTERA OF AMERICA. [PART I. 



Clypeus, a line on the mandibles, and the line on the scape of 

 the antennae, of a pale tawny. 



Var. No spots on the front nor on the metathorax. 



Bess. a. diff. — This Odynerus is easily recognized by its livery 

 and its velvety aspect. 



It differs from the 0. Guerreri by its conical abdomen and by 

 the superior salients of the metathorax ; from the 0. for amino tus, 

 by its metathoracic concavity, not nearly so well limited, and by 

 the salients of the superior angles, which are not sharp, but rui 

 obtuse, and separated from the post-scute], not by a little fissure, 

 but by a wide notch. By its livery it recalls the 0. otomitus, 

 which is near to it, but differs in its conical, sessile abdomen, 

 having the first segment wide and truncate, in its great size, etc. 



Eab. The hot and temperate parts of Mexico. (I caught 4 % , 

 2 9 in the valley of Mexlitlan.) 



C. Hinder plate of metathorax no longer margined superiorly 

 by sharp edge*; the superior edges blunted and effaced by 

 the rugosities of the latero-superior faces, which continue 

 over the edges down <>n to (he posterior face, and lose tin m- 

 selues in its concavity, instead of being separated from the 

 hinder face by tltc sharp edges. (Lateral angles still 

 existing.) 



92. O. arvensis Sacss. (Fig. 1H, 16a.) — Medius, niger, grosse punc- 

 tata* : O. dorsali simillimus at minor; ore, macula frontali et post- 

 oculari scapoque subtns, rufis vet ilavis ; pronoti margine, post-scutello, 

 maculis 2 metanoti abdominisque segmentis ]P-3° vel l°-4° flavo- 

 limbatis, 20-40 crassissime punctatis ; primi margine utrinqne auctoet 

 rufo-vario, pedibus flavis, basi nigris, alls fnmosis. 



9 • Clypeo valde latiore quara longiore, truncato, grosse punctato, nigro 

 vel rufo ; superne fascia fiava. 



%. Clypeo polygonal! pnulo latiore qnam longiore, fiavo, truncato, apice 

 dentulis 2 distantibus instructo. 



Odijn. arvensis Sauss. Rev. de Zool. XXI, 1869. 



9. Total lengtb, 14, 12 mm. ; wing, 11, 5-9 mm. 

 % . Total length, 12, 5-9 mm. ; wing, 9-7 mm. 



9. Form rather near to that of 0. Boscii, but smaller. The 

 abdomen a little more conical ; the 2d segment shorter and 

 more coarsely punctured; its inferior border a little lamellate 



