1929] 
Biology of Mining Bees 
179 
upper part was dry, powdery pollen. There were also many 
drops of moisture condensed on the walls of this cell. 
Whether the pollen had been put in dry, and the moisture 
that we found in the cell was due to nectar or water which 
the mother may have added, or whether the pollen was 
moist and the moisture which I found upon opening the cell 
was that which had come out of the pollen and condensed on 
the walls, is matter for conjecture. 
Fig. 15. The brood cup of E. taurea, with the mud wall cut away to show 
the intact papery lining. 
Another nest was opened which had a three-and-one-half 
inch gallery leading down to the cell. This cell was half filled 
with pollen, and the bee itself was within, with her pollen 
baskets full to overflowing. The nest was obviously far 
from complete. These bees do not seal the mouth of the 
turret; neither do they seal the burrow at the surface of the 
ground, but leave it open its full length. The cells at the 
bottom are sealed securely enough to afford sufficient pro- 
tection when they are hidden within the tunnels chiseled 
out of the hard clay. Sometimes one does find one of these 
turrets sealed, but this work is done by a Trypoxylon wasp 
which takes possession of the place for her own nest. 
These white-banded bees varnished the interior of their 
brood-cups with some waterproof substance, as did the two 
species of Anthophora; but these supplied an added protec- 
tion to the young bees, in the form of a thin, papery wall 
which completely lined the cells. While it is brittle, it is 
strong enough that one may pick away the mud from the 
outside and leave this lining intact, as shown in fig. 15. At 
first I thought that this lining had been placed there by the 
mother, but since those cells in which the eggs had failed to 
hatch did not have this lining, it seemed reasonable to 
