1929] 
Biology of Mining Bees 
165 
nine cells collected, three had dead larvae, five contained 
dried-up balls of food, and one harbored a parasitic cuckoo- 
bee. 
The “open door policy” of this species sometimes brought 
its trouble too. Not infrequently an animated fight was to 
be seen between two females, one evidently trying to usurp 
the burrow that had been made by another, and often dead 
bees were found at the foot of the bank. Occasionally a 
dead one was found in the burrow, and in all probability a 
second mother, in appropriating the nest, cleared the dead 
body out with the other rubbish. Frequently, however, the 
fights appeared quite alarming without proving fatal. One 
pollen-laden mother was seen backing out of her hole with 
the front leg of an intruder in her mandibles. The visitor 
showed no fight, but resisted with all her might ; at the foot 
of the hole, every little gain that the rightful owner made 
was offset by the intruder pulling her back. At last the 
intruder lost her hold, and as they went tumbling to the 
ground they engaged in a pugnacious embrace. Needless to 
say that the rightful owner lost most of her load of pollen, 
which deluged the face and head of her antagonist. Another 
pair was locked in deadly embrace for over twenty minutes, 
and there seemed no probability of their separating soon. 
They were so intent that they were unaware of the fact that 
they were being pushed into a test-tube. After five minutes 
more of violent struggling in this novel place, they lost their 
grip for a moment and separated, and when they were 
liberated, they both flew into the air, little disconcerted by 
the ordeal. 
A. abrupta made nests either with or without turrets, and 
the turret-making activities were directly correlated with 
water conditions. They required water in abundance, and 
when it was plentiful, so too were the turrets ; in droughty 
years they struggled on with few and small or no turrets, 
and their nesting activities were much reduced. If they had 
to struggle on with a small drop of water, they consumed much 
more time in mining than when they could be generous with 
the water and thoroughly and quickly wet the hard clay. It 
was pathetic to see the mother back out of her hole with a 
load of slightly moist soil instead of a load of wet mud; 
