4 PROCEEDINGS OF THE NATIONAL, MUSEUM vol. 82 



of upper lateral angle of enclosure, becoming gradually more visibly but 

 finely striato-punctate apically, the striae merging into the large lateral 



rugose areas on the sides sulcatus, new species 



Petiole of abdomen not distinctly carinate on center of venter, or with no 

 visible sulcus on at least a part of anterior half of carina between bases 

 of antennae ; usually smaller species averaging about 5 mm in length ; 

 propodeum with fine but distinct striae on area bordering enclosure on 



entire dorsal aspect trisulcus (Fox) 



5. Petiole of abdomen not sulcate in center of dorsum and without laterodorsal 

 carinae; vertex glossy, with fine, rather shallow, scattered punctures. 



frontalis (Fox) 



Petiole of abdomen with a very well developed carina on each side and very 



distinctly though shallowly sulcate on practically its entire length on 



dorsum 6 



G. Entire vertex glossy, with very minute, shallow, and rather close punctures. 



corusanigrens Rohwer 



Vertex at least partly striate or striato-punctate, the punctures larger and 



denser above and on sides, striae best seen when head is viewed at an 



angle from side trisulcus (Fox) 



DIODONTUS FRONTALIS (Fox) 

 Psen frontalis Fox, Trans. Amer. Ent. Soc, vol. 25, p. 4, 1898. 



In common with all the other species of the genus, including those 

 of Europe, this species is shining black, with silvery hairs on most 

 of the body, most evident on the head and especially the face, the 

 tarsi mainly yellow, the fore pair entirely so, and the fore tibiae 

 largely of that color. The antennal flagellum is usually of a more 

 or less noticeable testaceous-yellow color on most of its length below, 

 and the wings are hyaline, with the stigma fuscous. 



Structurally the entire membership of the genus is very similar, 

 and it is only by means of the rather minute characters cited in the 

 above key that it is possible to distinguish them. Trivial though 

 these characters appear at first sight, there is very little variation 

 in them, and I believe they are entirely reliable for specific dis- 

 tinctions. 



Originally described from Utah and Las Cruces, N.Mex. There 

 are before me 2 females and 1 male, 1 female with the locality 

 Boulder, campus of the University of Colorado, July 4 (T. D. A. 

 Cockerell), and the other pair with merely the State label from the 

 Baker collection. 



The male was unknown to Fox. When Mr. Rohwer examined the 

 Fox types in Philadelphia he made no notes on that of frontalis. 



DIODONTUS TRISULCUS (Fox) 



Plate 1, Figures 1, 2 

 Pscn trisulcus Fox, Trans. Amer. Ent. Soc, vol. 25, p. 5, 1898. 



This is the only other species of the genus than the preceding one 

 known to Fox. and as Mr. Rohwer did not examine the type when in 



