1929] 
Biology of Mining Bees 
159 
suggested that carnivouous insects can derive their mineral 
salts from the blood and juices of their food, but these 
mining-bees are nectar feeders; hence it is possible that 
they may need to obtain their necessary mineral salts by 
some such direct methods as this. 
On the next day the persimmon blossoms were beginning 
to open and already the bees had turned their attention 
thither; within three or four days more they were in- 
tensely active at this new task. In this short time, less than 
a week, the males had disappeared. Thus in a short while, 
and in keeping with the rapidity with which this species 
lives and does things, the males had come and gone, and the 
females remained buzzing at their new work. They hummed 
and danced in the sunlight in front of the bank ; this activ- 
ity, however, was not a courtship dance such as occurs in 
other insect species, but merely the industrious search in 
flight before the face of the bank as each bee tried to dis- 
tinguish her own burrow. It was not a simple task at so 
early a time in the season, and it gave rise to more commo- 
tion than later when the bees had had more experience. If 
one singled out an individual in the crowd and continuously 
followed it with the eye, one would see that it finally plunged 
into an opening, sometimes to remain and sometimes to 
come precipitously tumbling out again and try another. It 
is little wonder that the returning bees must spend some 
time in distinguishing their own nest among hundreds or 
even thousands of burrows, but my observations have sub- 
stantiated my expectation that later in the season, when the 
turrets were nearly all built, they would consume less and 
less time in this orienting dance as they learned more 
readily to distinguish their own nests among the hundreds 
in the group. I have stated elsewhere that when these bees 
came home late in the evening, their hovering in front of 
the nests was much prolonged, owing to their difficulty in 
finding their way in the fading light. A number of the 
larger turrets and their occupants were marked ; these were 
watched in comparison with the rest of the population. It 
was soon apparent that those with large turrets found their 
homes with much less hesitation than the turretless ones. 
Hence I sometimes wonder, since I have never yet learned 
