70 
Psyche 
[June 
were some tunnels about . 6 cm. 0/^ inch) wide, to a depth of 
about 10 cm. (4 inches). In them I did not find the larvae of 
Perdita opuntice but a few brown cocoons of a wasp instead. 
The bee which is apparently isolated at White Rocks is a 
small insect with black head and thorax and a clear amber- 
colored abdomen. It is scarcely 7 mm. inch) long. The 
face of the female is black; that of the male, partly yellow. One 
is struck by the fact that the pollen grains on the hind legs are 
distinctly larger than are the ocelli or simple eyes of this insect. 
See Fig. 3. 
Correspondingly narrow are the galleries of this bee in the 
sandstone. The entrances to the nests are generally found on 
Fig 1. — The nest is composed of numerous tunnelways leading down from the surface of 
the stone. The larvae with their typical double-rowed sawtooth backs are shown in some of 
the cells. Heavy stippling indicates sandstone; light stippling, fine, loose sand. (Verticle 
section approximately one-third natural size.) 
the upper surfaces of certain dome-shaped sandstone formations, 
some three to five yards wide 6 . Each nest has several entrances. 
These are more or less widened by the continual erosion of the 
stone. Hence, in a typical nest, one would expect to find three 
or four openings from 1-2 to 1 cm. in width, and separated from 
each other by a distance of about 10 cm. (4 inches). Most of 
these entrances are open. But, in a few cases, especially those 
leading almost straight down, the opening is closed with fine 
sand. However, the bees do not have difficulty in securing 
their entrance to these. They can not rake the sand out to open 
a passageway, for the fine particles would fall back on either 
6 See Plate II, middle figure. 
