20 
Psyche 
[March 
attack” (Brown 1975). Since territoriality is the exception rather 
than the rule in male sphecids, some ecological factors must 
impinge, favoring the evolution of the behavior in some species and 
not in others. According to Alcock, territoriality seems to evolve 
when males can locate areas where females are clumped or occur 
predictably. In addition, these areas must be defendable in terms of 
the time and energy budgets of the males. Lacking these conditions 
the large time and energy expense associated with defending a 
territory may not maximize reproductive success. 
Recently particular attention has been paid to male and female 
behavior in the sphecid genus Philanthus. In most North American 
species in which male behavior has been observed males exhibit 
territoriality. They also exhibit a specific behavior referred to as 
abdomen dragging which has been suggested to function in scent 
marking the territories with a mandibular gland secretion (Gwynne 
1978) which may attract females (Alcock 1975a). 
Philanthus psyche Dunning is a relatively small member of its 
genus, females and males averaging 9 and 8 mm in length, respec¬ 
tively. It is found in western and central North America (Great 
Plains and Great Basin) occupying sand dunes with low sparse 
vegetation, particularly grasses. Nesting areas are usually on the 
periphery of blowouts or similar dunal features. 
Methods 
Observations on Philanthus psyche were made about two miles 
east of Roggen, Weld Co., Colorado during July and August 1976 
and 1977 and occasionally throughout the summer of 1978. The 
general study area may be classified as sand sagebrush (Harrington 
1964). The specific study site was the area immediately surrounding 
a vegetation-free blowout, one side of which was bordered by a 
sandy ridge. The nesting area of P. psyche was in the border of the 
blowout and was level to slightly sloping. It was dominated by 
blowout grass \Redfieldia flexuosa (Thurb.) Vasey] and lanceleaf 
scurfpea ( Psoralea lanceolata Pursh). Further away the dominant 
plants were sunflower ( Helianthus spp.) along with various grasses. 
At the main observation area measuring 12 by 8 meters, detailed 
observations were made of male and female behavior and of 
locations of marked males, occupied territories and female nests. 
Individual males were marked with one or two spots of enamel paint 
