2S2 HYMENOPTERA OF AMERICA. [PART I. 



?. Insect very coarsely punctured, recalling the 0. Boscii, but 

 more coarsely cribrose and more retracted on the metathorax. 

 Clypeus pyriform, wide, punctured, rather wider than long. 

 Post-scntel feebly crenulate. Concavity of the metathorax occu- 

 pying all its width, rounded, notably wider than high, excavated, 

 finely striate and smooth as far as the borders; these are 

 extremely trenchant, but not forming spiniform lateral angles; 

 thesa ridges above all very salient on the summit, where they 

 often terminate in a dentiform or lamellar salient, separated from 

 the post-scutel by a strong notch. The external lateral surfaces 

 of the metathorax very rugose. Abdomen conical truncate, at 

 the base having a sharp ridge; the border of the second and fol- 

 lowing segments quite strongly punctured; but that of the 2d 

 not sensibly depressed. 



Insect black, clothed with tawny hair. Mandibles and at times 

 the end of clypeus, red. Two spots or an arc at the summit of 

 clypeus, a spot on the front, another behind each eye, and the 

 inner bordering of the orbits, as well as a line on the scape of the 

 antennae, yellow. Border of the prothorax, a spot under the 

 wing, tegulaa, two spots on the scutel, two others on the summit 

 of the metathorax and post-scutel, yellow ; segments 1-4 of the 

 abdomen bordered with the same color; the first border widened 

 on the sides; legs yellow, the base black. Wings transparent, 

 washed with brown-ferruginous. The yellow of the ornaments is 

 almost orange; it often passes, without doubt, into red. 



Var. One specimen has its ridges blunted at the beginning or 

 where the lateral angles would be, if they existed, but their 

 summit always forms a trenchant prominence. 



% . Unknown. 



Bess. a. diff. — This species is allied to the 0. Boscii, arvensis, 

 Hidahji, by the distribution of the colors. It has like the 0. 

 Boscii the scutel spotted with yellow, and like the other species 

 the post-scutel yellow. But it is distinguished clearly from these 

 species: 1st, by it's retracted metathorax, not laterally bidentate, 

 in consequence of the rounded posterior plate (not squarely cut), 

 of which, however, the ridges are very sharp and quite arcuate 

 (and not more or less straight or oblique as in the species cited); 

 2d, by the border of the 2d segment, which, although punctured, 

 is not depressed, and less reflexed. 



