246 UNIVERSITY OF COLORADO STUDIES 



Stizus godmani Cameron 



On July 31, 1908, I found a colony of Stizi nesting in a sandy creek 

 bed in the northwest part of Boulder, Colorado. The creek is very 

 near the contact of the Upper Austal and Transition Life Zones, and 

 affords a very interesting locality in which to collect Fossorial Hymenop- 

 tera. The colony of Stizi was near the edge of the sandy area, quite 

 close to a field of alfalfa. It was about 10 by 15 feet in area, and closely 

 filled with nests; often the nests were but three or four inches apart. 

 The conduct of the colony was very similar to that of Bembex spinolae 

 as described by Peckham in his interesting book on the habits of wasps. 

 Each time a wasp left its nest it would close it tightly with the loose 

 gravelly sand, throwing the sand in much the same manner as it would 

 if it were digging, then tamping it down with the four anterior legs, 

 holding the posterior pair over the abdomen. On return there was no 

 hesitation about finding the nest; but they would alight within a few 

 inches of it, walk to the exact spot, and, uncovering the opening, dis- 

 appear into the ground. I watched this colony a short time each day, 

 and found their working hours on warm sunny days to be from about 

 9 : 30 in the forenoon, to 4 in the afternoon. Of course there were always 

 a few who worked over time. On cloudy and rainy days little or no 

 activity could be noticed about the colony. Two days it rained about 

 noon, but shortly afterward it was bright and sunny; and by 3 o'clock 

 the whole colony was very active. About August 5 I began to notice 

 that the number of individuals was fewer than the day I first found the 

 colony, and from then on they became noticeably fewer; and on August 

 10 not a single Stizus was seen around the nest. 



The nest is about 8 cm. in diameter and 40 cm. long, ending below 

 the surface about 5 inches (13 cm.). It is straight, and at an angle of 

 about 90 with the surface. It is provisioned with small flies; none 

 of the ones I obtained could be determined because they were without 

 wings. None of the species of Bembex are known to remove the wings. 



The most interesting thing to me in connection with the finding of this 

 colony was that here in the same nesting site and within an area of about 

 150 square feet three apparently distinct forms were found nesting. 

 These were S. godmani Cam., S. lineatus Cam. and S. flavus Cam. 



