ODYNERUS. 1 15 



only be distinguished by the composition of the palpi, which are 

 not 4- and 6-jointed in Monobia, as in Odynerus. 



Transitions to Montezumia. — A few Odyneri take the appear- 

 ance of Montezumia, the first abdominal segment becoming quite 

 funnel-shaped (0. taptensis, etc.). In this case they can only be 

 distinguished by the examination of the palpi. Jjut in general 

 the facies is very different in Odynerus. 



Transitions to Nortonia. — A number of Odynerus have the 

 abdomen subpetiolate, the first abdominal segment becoming 

 elongate. This is especially the case in the species of the sub- 

 genus Odynerus, Division Hypodynerus. These form a regular 

 transition to Nortonia, and are only distinguished by their 

 appearance and more angulate nietathorax ; the first segment has 

 also a more triangular, depressed, and gibbous form, not being 

 funnel-shaped in the same way. In Nortonia it is properly 

 funnel-shaped. In Hypodynerus a sort of petiole only is formed 

 by the anterior face of the first abdominal segment. Nortonia is 

 quite intermediate between Odynerus and Eumenes, while Hypo- 

 dynerus quite connects itself with Odynerus by decided transi- 

 tions, and has the thorax very different from Eumenes. Indeed 

 in Nortonia the petiole cannot be doubted when the abdomen is 

 elevated; while in Hypodynerus, when the abdomen is raised. 

 the anterior face of the first segment is applied against the nieta- 

 thorax and fits against it, and one can only see the upper face of 

 the segment, which is quite transverse and which causes the 

 abdomen to appear quite sessile. 



Though it is not possible to define a trenchant limit between 

 Nortonia and Odynerus, yet as the most changeable types are 

 not American, it would be superfluous to insist upon this point. 



Geographical distribution. — The genus Odynerus is much the 

 greatest among the Vespidse, and, in a philosophical point ol' view, 

 one might take it for the stem of the family. 



Judging by the numerous species which have been found in the 

 countries already explored; by the number known in North 

 America and in Europe; by the numerous species which have 

 resulted from my researches in Mexico (although I could only 

 give to it very little time), and by what other travellers have 

 brought from various parts of the world, it is beyond doubt that 

 there exist more than a thousand species oi' Odynerus, and 

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