THE BEMBECID WASPS OF BOULDER COUNTY 245 



Steniolia duplicata Provancher 



This species is quite common at Boulder during the later part of the 

 summer, usually flying around flowers of Chrysothamnus graveolens. 



Bembidula ventralis Say 



A female without any black on the tibiae was taken at Boulder, 

 Colo., July 25, 1908 by S. A. Rohwer. 



Bembex sayi Cresson 



This species is not common, and when seen is hard to catch, because 

 of its swift flight. Three females were taken in Boulder during the 

 first of August by S. A. Rohwer. The bands on the mesonotum are 

 very narrow in two of the specimens, and there is more black on the 

 abdomen. This species does not nest in colonies as do Bembex spinolae 

 Farg. and Stizus godmani Cam., but digs its nest off by itself. I found 

 four nests during the season in the sandy soil along a creek west of 

 Boulder. The nest is always closed on leaving. The wasp while near 

 her nest appears very nervous, quite contrary to the actions of Stizus 

 godmani Cam. There is no hesitation as to finding the nest, but the 

 wasp will light, dig for a few seconds, then fly off, look around to see if 

 anything is near, then return to the nest. Sometimes when inside 

 she would close the opening even if she stayed a few moments. On 

 August 4, 1908, I excavated a nest which was 70 cm. long and 1 cm. in 

 diameter. It was 10 cm. below the surface, and leaving it at an angle 

 of about 70 . The provisioning was not completed, but it contained a 

 Tabanid larva, one specimen of Tabanus jratellus Will, and three 

 Tachinids which have bright red eyes in life. This species has a short 

 season of flight. It lasts only about three weeks, during the later part 

 of July and first of August. 



Bembex spinolae Farg. 



This species was rather common during August of 1907, but only one 

 specimen was taken in 1908. All the BouJder specimens have a small 

 yellow spot below the tegulae. 



