358 IIYMENOPTERA OF AMERICA. [PART I. 



metathorax, destitute of large tubercles, its crested post-scutel, 

 and not spined clypeus (%). 



From 0. acolhuus, it differs by its post-scutel not truncate so 

 as to have a vertical posterior face, its crest being more anteriorly 

 placed, not on the posterior ridge; by its metathorax, bituber- 

 culate superiorly and bispined at the posterior end. The 1st 

 segment is also more elongate, and the clypeus % is not angular- 

 bidentate on its inferior margin Comp. also 0. nahuus. 



From 0. coyoius and totonacus it differs sufficiently by its 

 crested truncate post-scutel. 



Eab. The temperate parts of Mexico. One % from the valley 

 of Orizaba (Sumichrast). 



153. O. Chidlimecus Sacss. — Minimus, gracilliraus, niger, cribri 

 instar punctatus ; prothorace bidentato ; post-scutello truncato, cristato ; 

 inetanoto superue bituberculato ; capite et antemiis 9 omnino nigris ; 

 prothoracis margine antioo, scutelli et abdominis segmentorum l 1 , 2' 

 margine postico, flavis ; tibiis et tegulis flavo-ornatis. 



Odyn. chichimecus Sauss. Revue de Zoolog., IX, 1857, 2S0, J. 



Total lengtb, 6 mm. ; wing, 4.5 mm. 



9. The smallest species. Head a little higher than wide. 

 Antennae inserted below its middle. Sinus of the eyes very open. 

 Thorax slender, not contracted anteriorly; its anterior margin 

 finely crested ; its angles toothed. Post-scutel truncate ; its ridge 

 arcuate, crested, but not very strongly. Metathorax convex, 

 prolonged, having a polished shallow cavity, not extended supe- 

 riorly to the post-scutel ; superiorly this cavity is margined on 

 each side by a little compressed sharp tubercle. Extremity of 

 metathorax with two little spines, next to the two teeth which 

 make the articulation. Abdomen elongate ; the first segment 

 triangular funnel-shaped, swelled and a little constricted before 

 its margin, which is rather thick. Second segment cylindrical ; 

 head, thorax, and first abdominal segment polished and cribrose 

 with strong punctures; metathorax and second segment not quite 

 as strongly cribrose, and with a line of stronger punctures along 

 its margin. Metathorax finely punctured. Segments 3-6 quite 

 finely punctured. Black. Anterior margin of prothorax, poste- 

 rior margin of scutel, and of the first two abdominal segments of 

 the abdomen, yellow ; wing scales marginate with yellow ; tibiae 

 yellow on the superior face, at least at base. Wings subhyaline. 



