ODYNERUS. 159 



6, 6. The first abd. segment margined with yellow. 

 7. Two yellow fasciae on the abdomen. 28. pilosus. 

 7,7. Five yellow fasciae on the abdomen. 18. Sylveirce. 

 5.5. Thorax black, with yellow or luteous ornaments; body 

 sericeous or shining, not velvety. 



6. Abdomen with 2 yellow or luteous fasciae. 



7. Body very coarsely punctate, posterior margin of pro- 



thorax luteous. 21. conspicuus. 



7, 7. Body not very coarsely punctate ; anterior margin of 



prothorax yellow. 

 8. Post-scutel black. 9. ambiguus. 



8, 8. Post-scutel yellow. 22. cingulatus. 

 6, 6. Abdomen with 3 yellow fasciae. 



7. Post-scutel black. 16. Santa-Anna. 



7, 7. Post-scutel yellow. 25. campestris. 



6, 6, 6. Abdomen with 4 or 5 yellow fasciae. 



7. Thorax cubic, short. 



8. Two yellow spots on the second segment. 



• 20. birenimacnlatus. 



8, 8. No yellow spots on the second segment. 



20. r birenimacnlatus. 

 17. \ Bustamenti. 

 7, 7. Thorax more elongate. 



8. Metathorax with sharply defined border. 



9. Post-scutel black. 



, „ ^ ,, 10. f capra. 



10. Ornaments yellow \ ; 



14. I adiaoatus. 



10, 10. Ornaments white. 12. albophaleratus. 



9, 9. Post-scutel more or less yellow 



10. Body normal. 



11. Color gray, sericeous. IS. Sylveirce. 



. 15. f fastidiosuscuhts. 



11,11. Color black, shining. < J 



13. <- Catskdlensis. 



10, 10. Body slender, elongate. 8. tigris. 



8,8. Metathorax rounded behind. 25. campestris. 



I. Metathorax having its concavity angulate, bordered all around 

 by trenchant edges (Sect. I, a, Sauss. Vespides, I, 135). 



(Group of O. parietum Linn.) 

 Among these insects the metathoracic cavity has a polygonal 

 form, determined by its angulate edges. The medial carina 

 divides the fossette into two equal parts, which can be compared 

 in form to two coupled pentagons. Their angles often make on 

 each side a sort of tooth (which is variable among individuals of 



