ODYNERUS. 271 



and truncate, but often appearing slightly bidentate. Thorax 

 widened before, retracted little or none. Post-scutel crenulate. 

 Metathorax very coarsely rugose; its concavity striate, but 

 cribrose in its superior moiety from the punctures which continue 

 with those of the superior face ; the latero-superior ridges blunted, 

 effaced ; on each side a dentiform angle at the meeting of the 

 lateral and inferior ridges. First abdominal segment silky, 

 smooth, truncate, and a little rounded at the base ; the 2d short, 

 densely punctured; its posterior border offering a wide depressed 

 zone, widened in the middle, very coarsely cribrose, as well as 

 the following segments ; at times a little channelled, but the 

 border not turned up. 



Insect black. Mouth red, with a yellow spot at the base of 

 the mandibles; superior moiety of the clypeus yellow or red; 

 inner border of orbits and a spot behind each eye, red or yellow; 

 scape of the antennae red, with a black line above; a spot on the 

 front, yellow or red. Anterior border of prothorax yellow, often 

 followed with red; tegulae yellow or red, post-scutel and a spot 

 on each side of metathorax above, yellow ; segments 1-4 of the 

 abdomen regularly bordered with yellow ; the first having its 

 border on each side widened or confounded with a spot or oblique 

 band, yellow surrounded with red, which leave above a black 

 trilobed or square notch ; often of red on each side or bordered 

 with yellow. Legs yellow, black at the base. Wings smoky or 

 a little reddened with a light violet reflection. 



Var. a. Clypeus red, with a yellow band on the summit. 



b. No red on 1st abdominal segment, 



c. Two yellow or red dots on the scutellum (Tennessee). 

 ' d. Prothorax red, bordered with yellow (Missouri). 



The crest of the post-scutel varies; sometimes finely crenulate 

 and continuous, sometimes dentate and notched in the middle. 



% . A little smaller. Clypeus polygonal, yellow, wider than 

 long, truncate on its anterior border, offering a very small tooth 

 on each extremity of this border; its apical margin a little pro- 

 longed, so that the polygon is not regular, the inferior borders 

 forming thus a larger arc than the superior; hook of the antennae 

 black or ferruginous; mandibles and ornaments of the head yel- 

 low or orange ; a red dot on the flanks before the tegulae ; often 

 the posterior border of the prothorax red and a little of red about 

 the scutels ; latero-superior borders of the concavity of the 



