3 64 Annals Entomological Society of America [Vol. X, 



Genus Zethiis Fabricius. 



The five representatives of this genus found in America 

 north of Mexico are readily divided into two groups which may 

 be called after the oldest species in each, the spinipes group 

 and the poeyi group. The first would fall into the Division 

 Zethusculus Saussure and the second into the Division Didymo- 

 gastra Perty. Saussure regarded the separation of the latter 

 division from the former, which was based on the difi^erent 

 lengths of the subpetiole, as "entirely empirical and should 

 not be preserved except to facilitate the determination of 

 species." However with the limited number of species covered 

 by this paper the two groups are quite distinct. 



Key to the Species of Zethiis. 



1. Robust species; clypeus triangular; depth of head behind the eyes greater 



than before their hind margin; concavity of the propodeum wide; small 

 spines on the lateral aspect of the middle and posterior tibia;; petiole con- 

 stricted apically, gaster black or blackish {spinipes group) 2 



Slender species; clypeus oval; depth of head behind the eyes less than 

 before their hind margin; concavity of the propodeum not pronounced; 

 no spines on the lateral aspect of the tibia;; petiole much narrowed, but 

 not constricted apically; gaster after the subpetiole reddish {poeyi group). A 



2. Petiole half as wide as long, greatest width nearer the apex than the 



base; area on the mesonotum adjacent to the tegulae not distinctly 



defined, sparsely punctate .3 



Petiole much more inflated, two-thirds as wide as long, greatest width 

 nearer the base than the apex; area on the notum adjacent to tegula; 

 distinctly defined and impunctate stibstricta Haldeman 



3. Pronotal lobe impunctate basally; little yellowish on dorsal aspect of 



the thorax spinipes Say 



Pronotal lobe densely punctate basally; much yellowish on the dorsal 

 aspect of the thorax variegatus Saussure 



4. Clypeus without teeth apically poeyi Saussure 



Clypeus with three teeth apically slossonce Fox 



Zethus spinipes Say. 



Zethus spinipes Say, Thomas, Bost. Jour. Nat. Hist., vol. 1, 1837, p. 387-388.— 

 Saussure, Henri de, Etud. fam. Vespid., vol. 3, 1854, p. 122. — Say, Thomas, Writings 

 of Thomas Say, (LeConte, J. L.), vol. 2, 1859, p. 767. — Saussure, Henri de, Smith- 

 son, Miscel. Coll. No. 254, 1875, p. 29. 



Eumenes pennsylvanica Haldeman, S. S., Proc, Phila. Acad. Sci., vol. 6, p. 365. 



Female. — Length, 14.75 mm. ; wing, 12.5 mm. Mandibles 4-toothed, 

 first tooth distinctly longer than the second ; clypeus roughly triangular, 

 nearly t\vice as wide as long, basal margin narrow, concave, sides 

 slightly convex, sotnewhat indented by the insertion of antenna, and 

 widely divergent apically, apical lateral margin not distinctly separated 

 from the gense, apical margin truncate, with two small teeth, surface 

 strigose in median portion, coarsely punctate elsewhere; small carinse 

 on inner margins of insertion of antennae, area between the antennae 

 strigose; head greatly inflated behind the eyes, deeper behind the eyes 

 than before their hind margin; pronotal lobe impunctate; mesonotum 



