60 HYMENOPTERA OF AMERICA. [PART I. 



Head much compressed transversely, that is, wide, but not thick, 

 nor enlarged ; the eyes very convex and entirely covering the 

 cheeks. Clypeus always longer than wide, with a variable 

 termination (bidentate, indented, truncate, or rounded). 



Thorax variable, globular, or long quadrate, rarely compressed, 

 but always without spiniform angles. 



Abdomen lengthened pediculate. The first segment forming a 

 linear or subcampanulate petiole, about as long as the thorax ; 

 the remainder of the abdomen pyriform. 



This genus is very abundant in species, and is found over all 

 the surface of our globe. It is broken up into peculiar types, of 

 wmich one (Division Alpha) is represented everywhere, and the 

 others solely on one part of our planet. These types are con- 

 nected by natural transitions which embarrass one in assigning 

 them very fixed limits. 



The Eumenes are well represented on the new continent. Of 

 six divisions 1 into which I have divided the genus, four are found 

 on the Western Continent, but the divisions Paehymenes, 

 Omicron, and Zeta, are only represented in the tropical parts of 

 America. The insects, peculiar to the Division Omicron, inhabit 

 all the equinoctial parts of the continent ; and those which belong 

 in the Division Alpha, extend themselves over the two American 

 continents within their most extended limits. 



Division PACHYMENE3. 

 (Sauss. Vespides I, 73, III, 153.) 



Abdomen much depressed, never compressed, petiole widened 

 or campanular, parted by a groove ; its hinder margin having 

 usually a transverse groove; clypeus generally bidentate ; body 

 smooth, silky, and chatoyant or velvety ; wings large. (American 

 type.) 



These insects have the appearance of Polybia, as the Monte- 

 zumia have that of Synoeca. It is especially by this appearance 

 that one recognizes them and the semblance holds good in the 

 depressed form of the petiole and in the p}Tiform abdomen as 

 well as the silky appearance of the body. 



1 I do not count the Division P<ireumenes, which is worthy to form a 

 genus (Etudes sur la Farnille des Vespides, III, 133). 



