286 HYMENOPTERA OF AMERICA. [PART I. 



Insect black, clothed with a brownish or grayish pile. A spot 

 on the summit of the mandibles, an arcuate band or two spots on 

 the summit of clypeus, a spot on the front, another behind each 

 eye, a line on the scape of antennae, a narrow line on the anterior 

 border of prothorax, tegulse, a spot under the wing, post-scutel, 

 knees, tibiae, and tarsi, yellow. The first four or five segments 

 of the abdomen regularly bordered with yellow ; the border of 

 the first confounded on each side with a spot or an oblique lateral 

 line. Wings transparent, smoky, with some violet reflections; 

 nervures brown. A red or brown dot on the wing scales. (The 

 wings are at times slightly ferruginous.) The last article of the 

 tarsi at times brown. 



Var. a. Two yellow dots on the superior faces of metathorax. 

 placed on each side of the post-scutel (Tennessee). 



6. Often two yellow dots on the scutel and the lateral spots 

 of the first segment lengthened, oblique (Illinois). 



%. Smaller. Clypeus yellow, polygonal, as long as wide, 

 terminated by a slightly concave border, appearing bidentate if 

 looked at beneath. A yellow line on the mandibles. Hook of 

 the antennae ferruginous beneath. Last article of tarsi often 

 black. The intermediate thighs often varied with yellow. 



Var. Frontal and post-ocular spots almost nothing. Border- 

 ings of the abdomen very narrow. Wings hyaline. In the two 

 sexes the superior teeth of the mctathoracic ridges are often but 

 little developed, indistinct, or even wanting. One also remarks 

 variations in the punctuation of the border of the concavity of 

 the metathorax. The extremity of the clypeus is often hollowed 

 by a fossette which gives it the appearance of being notched and 

 bidentate-. 



Bess. a. diff. — This species has the same distribution of colors 

 as the 0. Megaera, but its ornaments are of a lively yellow and 

 not whitish. Besides, the abdomen is less conical; the clypeus 

 9 has its angles more salient and the metathorax is not bounded 

 by distinct and trenchant ridges without. The two superior 

 teeth of the metathorax are as strong as they are well developed. 

 T7ie icings are less obscure. 



The 0. foraminatus somewhat recalls also the Ancistrocerus 

 campestris. 



Finally, it resembles in so striking" a manner the 0. trilobus 

 Fabr., that one will be tempted to take it for an American variety 



