ODYNERUS. 259 



— b. All the intermediate degrees between the black and the 

 rufous variety (Illinois, Tennessee). 



%. Metathorax less blunted on the latero-superior borders of 

 the concavity, the superior edges more elevated, forming lines of 

 salient rugosity, and separated from the post-scutel on each side 

 by a fissure ; often exhibiting two slightly crenulate salients; the 

 two lateral teeth very sharp. Abdomen more conical. 



A little smaller; clypeus as long as wide, yellow. Mandibles, 

 inner borders of orbits, spot on the front, and a line on the scape 

 of the antennae, in general, yellow ; hook of the antennae ferru- 

 ginous. A red spot under the wing. Borders of abdominal 

 segments 2, 3 adorned with yellow ; the 2d reflexed, strongly 

 channelled ; rugosities of these two borders excessively strong. 

 Wing not so deeply colored as in female. 



Var. a. Angles of metathorax red ; a little red bordering the 

 yellow within the black notch of the first segment, especially on 

 the right and the left. 



b. Two yellow dots on the superior face of the metathorax and 

 two beneath the wings. 



c. The whole anterior border of the prothorax red, widely 

 margined with yellow. 



d. Wings transparent. Scutellum black. — Illinois (Walsh). 



e. Body more and more rufous. 



This species seems to become more rufous as it goes southward. 

 It is also rather variable in the strength of the punctures. 



Bess. a. diff. — The 0. dorsalis is remarkable for the inequality 

 of the metathorax in the different sexes, from whence it results 

 that the males are well placed in this section, while the females 

 seem by their effaced ridges to go better into the Divisions B. or 

 C. The species greatly resembles the 0. Boscii and arvensis, 

 but above all it differs from them by its greater size, by its trun- 

 cate, not bidentate clypeus, and by its more obscure wings. It 

 differs from the 0. Boscii by the less elevated ridges of the meta- 

 thorax, and from the arvensis by the more elevated ridges. The 

 ferruginous individuals resemble the 0. Iturbidi. Finally, the 

 species is clearly different by its maxillary palpi, which are those 

 of a Bhynchium. 1 



1 With the 0. dorsalis, the maxillary palpi have the 1st article large; 

 the 2d and 3d slender and long ; the last three quite small. The 3d 



