104 S. A. ROHWER. 



Habitat. — Florissant, Colorado, June, 1906. Dedicated to 

 Prof. T. D. A. Cockerell, who collected it. 



This species is related to nearcticus Kohl, but may be known 

 at once by the absence of spines on the tibiae. It belongs to 

 the genus Pemphredon -in the restricted sense. 



Diodontus argentinie n. sp. 



Male. — Length 4 mm. Clypeus with a deep sub-semicircular notch 

 in the middle, and two lateral teeth. Front with close, rather small, 

 in some places confluent punctures; the vertex with small, distinct, 

 well scattered punctures; cheeks rather strongly striato-punctate. 

 Ocelli in a equilateral triangle, not placed in pits; the distance the 

 lateral ocelli not nearly as great as the distance between one of them 

 and the nearest eye margin. Third and fourth antennal joints equal; 

 joints 9-12 slightly spined beneath. Dorsulum shining, with a few 

 very small punctures; mesopleurae striate above, below in the middle 

 rugose. Scutellum posteriorly striated, at the sides there is a large 

 circular depression. Metanotum rugose; posterior face with small 

 indistinct fovea and a few stria?; the lateral ridges strong; metapleurae 

 with some transverse stria?. Legs rather robust; posterior tibia? not 

 strongly spined. Venation somewhat different than the typical 

 Diodontus as figured by Kohl (Die Gattungen der Sphegiden), but 

 most of the American species are similar to argentine. The tran. med. 

 and ba. are interstitial; the cub. of the hind wings is interstitial with 

 the tran. med. There is an indication of a first tran. cu. Abdomen 

 shining, impunctate, not constricted between the segments dorsally. 

 Color black; tibia? and tarsi beneath yellowish-brown; palpi grayish- 

 yellow. Wings dusky hyaline, iridescent; venation black. Besides 

 the usual pubescence of the face the insect is nude. 



Habitat.— Cripple Creek, Colorado, July 29, 1906 (S. A. 

 Rohwer), at flowers of Argentina anserina. Cripple Creek is 

 in the Canadian Zone, and has an altitude of about 10,000 feet. 



This species is not close to any described species. The 

 black mandibles, dark legs, striato-punctate cheeks should 

 make it easy to separate it from the other species. 



Diodontus vallicolae n. sp. 



Male. — Length about 4 mm. Anterior margin of the clypeus 

 notched in the center and with two lateral teeth. Seen from above 

 the head is depressed between the eyes. Between the antenna? is a 

 faint indication of a carina. Front rather coarsely punctured, the 

 punctures elongate, and at some angles appearing striato-granular; 

 vertex more sparsely punctured; cheeks below striato-punctate, but 

 not so strongly so as in argentinie. Antenna? rather elongate, some- 

 what moniliform apically, joints 10-12 slightly spined apically be- 



