22 
Psyche 
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O. NEST 
• * TERRITORY 
OPEN SAND 
Figure 1. Map of main observation area showing vegetation, nests and territories. 
tions to nesting. For species such as P. albopilosus which nest in the 
open sand, it may be adaptive to dig much deeper nests because 
shifting sands can disrupt the cells in the nest. Mean cell depth for 
P. psyche and P.. albopilosus at Roggen are 21.5 and 52.0 cm, 
respectively (Evans 1975 and unpublished data). The ability of 
females of P. psyche to nest in the peripheral area with stabilizing 
vegetation allows them to dig shallower nests and possibly more per 
season and to avoid the high surface temperatures of the open sand 
during the middle of the day. 
On the other hand, areas of more dense vegetation may restrict 
nesting due to the fact that plant roots interfere with digging. 
Therefore, although plants stabilize the dune, females require at 
least a small amount of space between plants for digging. Nests 
occurred in small bare spots in the vegetation, at least a short 
distance from the base of the plants. Female P. psyche consistently 
nest in this type of situation, not only in the Roggen area (where the 
species is extremely abundant), but also in other areas of Colorado 
and New Mexico where 1 have observed this species. 
It was evident that males set up territories in small plots devoid of 
vegetation (or nearly so) within the nesting area (Figure 2). By 
