L82 HYMENOPTERA OF AMERICA. [l>ART I. 



arcuate trenchant ridge. Abdomen slender; first segment a little 

 narrower than the 2d, distinctly truncate anteriorly, subpedicu- 

 late at the base, with the anterior face smooth ; the superior face 

 slightly widened behind, bounded before by a strong sutural 

 ridge, very distinct. The abdomen very finely punctured, but 

 the 3d and following segments rather strongly so, and especially 

 the border of the 2d segment offering a wide zone, very strongly 

 bchannelled, with subturned up border. Near 

 the margin of the \>\ segment one sees also a line of punctures. 



Insect black, clothed with gray-ferruginous hair. Two lateral 

 dots on the clypeus, one behind each eye, a mark on the front, 

 yellow or ferruginous ; a bilobate spot in the middle of the pro- 

 thorax and post-scutel, wholly or partly yellow. Wing scales 

 brown. Abdomen wholly black; only the first segment adorned 

 with a yellow border, suddenly widened on the sides (or joined 

 with two lateral spots). Tibiae and tarsi ferruginous or yellow ; 

 antennae ferruginous beneath, black above, with the scape at times 

 wholly ferruginous at the base. Wings of a transparent brown, 

 with violet reflections, particularly obscure along the nervures. 



I'm: A spot beneath the wings and a border on the 2d abdo- 

 minal segment, yellow. 



%. Smaller. Antennae very large, terminated by a little 

 hook; clypeus yellow, with a triangular notch; labrum and man- 

 dibles before, yellow; post-scutel yellow, or only bipunctate with 

 yellow; the 2d abdominal segment a little compressed at the 

 base, bordered with yellow; its margin a little sinuate, concave 

 areuate in tin' middle above, more or less retrousse, compressed : 

 the .'111 and 4th segments often adorned with a fine yellow edging. 

 The border of the 1st segment often presents a little of red; some- 

 times a little widened on the sides. With this species the orna- 

 ments are yellow-golden or sub-orange. 



Var. a. A yellow dot under the wing. Border of the prothorax 

 entire, bilobate. 



b. %. Post-scutel black. On the abdomen only two narrow 

 borders. (Illinois.) 



C. %. Head and thorax entirely black; mandib.es margined 

 with yellow ; Isl abd. segment narrowly, 2d very narrowly bor- 

 dered with yellow. (Florida.) 



Eess. a. diff. — This Odynerus is quite easy to recognize by the 

 very rugate and channelled border of the 2d segment; by the 



