1929 ] 
Biology of Mining Bees 
181 
in the exposed portions. One can readily see how landslides 
or rain would demolish the work of these little builders, 
and do damage to their tunnels as well. Three small colonies 
were seen, also, in roadside banks in situations similar to 
the above except that the soil was crumbly and exposed. 
Much of their work has been lost ; they did not become estab- 
lished in these exposed sites. Others were seen at Wesco, one 
hundred twenty miles southwest of St. Louis. Some were 
in banks, others in level ground, and in three different 
places they had chosen for their home-site the soil in the 
roots of some trees which had been torn up by a tornado 
three years previously. Here again they enjoyed the pro- 
tection of the roots, and throve. One of them (fig. 14) had 
twenty-five nests on one side of the base of the upturned 
tree, and thirty on the opposite side. 
The colony of bees during the five years, had decreased 
in size. In 1922 about forty members were building and 
two-thirds of them were far back on top of the clay bank 
where the darkness was indeed conspicuous; the turrets 
were pointing in every direction. During this same period 
its neighbor Anthophora abrupta had reached great pro- 
portions. The causes for the rise of one species and the 
decline of the other, are fully discussed in the St. Louis 
Academy of Science paper already referred to. 
