162 HYMENOPTERA OF AMERICA. [PART I 



loses its slender appearance. The first segment of the abdomen 

 is often quite strongly punctured and even sometimes divided by 

 a groove. We possess many males of very small size (length 

 G-7 mm.) and quite slender, taken by Edward Norton in the 

 environs of New York and in Massachusetts, which offer very 

 slender yellow markings, and in which the metathoracic ridges 

 are quite blunted. One, however, recognizes them by their 

 enlarged antennae, yellow beneath at the extremity. With this 

 species the bordering of the prothorax is narrow, a little bilobed, 

 terminating in a point on each side. Sometimes the metathorax 

 is but little angulate, while the superior ridges are also more 

 arcuate. 



Bess. a. diff. — This species is recognized by its form, very 

 slender and elongate, but yet different from that of 0. fulvipes, 

 in that the thorax is flattened above and the abdomen beneath, 

 as with the 0. capra and its congeners, not cylindrical as with 

 the 0. fulvipes and its neighbors. In its livery it resembles the 

 0. campestris, but is distinguished from it by its very much more 

 slender form, by the very sharp ridges bordering the metathorax, 

 by the first segment having the border not enlarged upon the 

 sides, etc. The very small males could be easily confounded with 

 •those of the 0. Philadelphia, but can be easily distinguished 

 from them by the wide and short form of the superior face of the 

 first segment and by the absence of its great longitudinal groove. 



Hab. The United States. Canada. (Lake Superior.) Con- 

 necticut. Xew York. Pennsylvania. Illinois. Louisiana. The 

 Prairies. (Fort Tejon.) (14 ?, 10 V) 



9. A. ambiglius Spin. — Niger, punetatus ; ruetanoto rugoso, excavato, 

 acute marginato, utrinque angulato ; antermi.s subtus rufis ; pronoti mar- 

 gin e antico, macula subalari, et scutelli. abdominis segmentorum 1', 2' 

 margine portico, luteis ; secundo subtus basi tuberculato ; alis rufes- 

 centibus, apice griseis, tegulis flavo-margiuatis ; % clypeo flavo, tibiis 

 et tarsis rufis; scutello et pleuris normunquam immaculatis. 



Odyn. ambiguus Spin., Gay's Hist. fis. de Chile, Zool., VI, 264, 9 (1851) 



9.— Sauss. Vehicles, I, 140, 23, 9. 

 Odyn. BustiUosi Sauss., Gay's, Chili, ibid. 507,10, % . — Sauss. Vespides, 



I, 141, 25, % ; III, 205. 



9. Total length, 9.5 mm. ; wing, 6.5 mm. 

 $ . Total length, 7 mm. ; wing, 5.5 mm. 



