358 HYMENOPTERA OP AMERICA. [PART I. 



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

 and uot spiued 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 tbe posterior ridge; by its metatliorax, bituber- 

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

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

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



From 0. eoijotus and lutonacus it differs sufficiently by its- 

 crested truncate post-scutel. 



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

 of Orizaba (Sumichrast). 



153. O. ChicIlimecilS Sauss. — Minimus, gracilliinus, niger, cribri 

 instar punctata* ; protliorace bidentato ; post-scutello truncato, cristato ; 

 metanoto superne bituberculato ; capite et antennis J omnino nigris ; 

 protboi-acis margine antico, scutelli et abdominis segmentorum 1', 2' 

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



Otli/n. chichimecus Sauss. Revue de Zoolog., IX, 1857, 2S0, £• 



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



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

 Antennas 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. Metatliorax 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 subhyalinc. 



