ODYNERUS. 1G1 



bordered by very sharp and trenchant ridges, not arcuate, but 

 straight and forming on each side an acute spiniform angle. The 

 latero-superior borders of the plate are straight, salient, terminated 

 above by an elevation which is separated from the post-scutel by 

 a kind of notch or feeble fissure. Upon the sides of the meta- 

 thorax, the ridge is prolonged by a wide and indistinct furrow 

 (in other words, the latero-superior faces of the metathorax are 

 feebly and widely channelled along the edge which borders the 

 posterior side) ; the superior medial ridges which form the 

 re-entering angle are less strongly pronounced. Abdomen 

 depressed. Head and thorax densely cribrose. Superior face 

 of the metathorax very rugose. 



Insect black. A spot at the base of the mandibles, another 

 upon the front, a point behind the eyes, the anterior border of 

 the prothorax, a spot below the wings, the posterior border of 

 the post-scutel and two spots on the posterior border of the 

 scutellum, yellow. Clypcus either with four yellow spots, or 

 yellow with a black square, or bordered with yellow. Antennas 

 black, ferruginous beneath, with a yellow line upon the scape. 

 Segments of the abdomen all ornamented with a regular yellow 

 border; the borders of 3d and 4th often very narrow and the 5th 

 wanting. Feet black, tibiae and tarsi yellow, these last often 

 orange. Wings transparent, washed with brown-violet toward 

 the end ; wing scales yellow, with a brown dot. 



% . Smaller, having the form equally slender, although the 

 thorax may be shorter. Coloration the same, but in general the 

 border of the scutellum presents but two yellow dots, while the 

 post-scutel is black, or also marked with two yellow points. 

 Head large; eyes much swollen ; clypeus lengthened, pentagonal, 

 terminated by two teeth, entirely yellow, as well as the mandibles. 

 Angles of the prothorax dentiform. Legs entirely yellow, the 

 femora at times marked with black above ; coxa? spotted with 

 yellow. Antennas very large and very thick, orange beneath, 

 terminated by a ferruginous hook, or they are wholly ferruginous 

 upon the last two articles. 



Observation. — There exist some quite singular differences in 

 the form of the males. In general, the thorax is less length- 

 ened than in the ?. The teeth and metathoracic ridges are 

 also subject to vary within certain limits, being often blunted. 

 When the last segments of the abdomen are retracted, the insect 

 11 



