ART. :i6 WASPS OF SUBFAMILY PSENINAE MALLOCH S 



Genus DIODONTUS Curtis 



Diodontus Curtis, Brit. Ent., vol. 1, p. 496, 1834. (Genotype, Psen palUpes 



Panzer, by original designation.) 

 Neofoxia Viereck, Trans. Amer. Ent. See, vol. 27, p. 338, 1901. (Genotype, 



Psen atratus Panzer, by original designation.) 



Distinguished from the other genera of Pseninae by the presence 

 of a prominent vertical carina between the bases of the antennae, 

 which is usually centrally sulcate on at least a part of its extent, and 

 which connects with a more or less curved ridge or carina that runs 

 across the face below the bases of the antennae. The second and 

 third submarginal cells each receive a recurrent nervure (pi. 1, fig.l), 

 and the nervellus of the hind wing is perpendicular or almost so 

 and situated jDroximad of the base of the cubitus (pi. 1, fig. 1). 

 Occipital carina as in Psen, not carried entirely across the ventral 

 surface of the head. Fore trochanters and basal third of the fore 

 femora flattened on ventral surface in females. Pygidial area broad, 

 with very inconspicuous punctures. 



The cited genotyi^es of this concept are accepted as synonyms, and 

 I have before me several examples identified as atratus by different 

 European workers which belong to the collection of the National 

 Museum. This species has the petiole of the abdomen similar to 

 that of t7'isulcus Fox, but the propodeum outside of the enclosure is 

 very coarsely rugose, and the head back of the eyes is vertically 

 striate, neither of which characters is found in the North American 

 species. 



I present below a key to the North American forms which I con- 

 sider entitled to specific recognition. 



KETSr TO THE SPECIES OF GENUS DIODONTUS 



1. Females 2 



Males 5 



2. Petiole of abdomen rounded on sides, without a definite lateral marginal 



carina on each limit of dorsal surface and without a dorsocentral sulcus 



except on basal half or less of its length 3 



Petiole of abdomen not regularly rounded on sides and below, usually with 

 distinct carinae at least on sides, and always with a well-defined but 

 shallow sulcus on practically entire length of its dorsal surface 4 



3. Propodeum with sides adjacent to enclosure distinctly striate though not 



very coarsely so ; mesonotum with quite deep punctures anteriorly and 

 laterally ; petiole of abdomen without any trace of laterodorsal carina 



even at base frontalis (Fox) 



Propodeum with very shallow punctures and almost no definite striae adja- 

 cent to enclosure ; mesonotum very feebly punctate ; petiole of abdomen 

 with a slight laterodorsal carina on basal half occidentalis, new species 



4. Petiole of abdomen with a very distinct central carina on ventral surface ; 



carina between bases of antennae distinctly sulcate to anterior extremity ; 

 larger species, 7 mm or more in length ; propodeum almost smooth laterad 



