1929] 
Biology of Mining Bees 
161 
solid clay they built distinct cup-shaped or thimble-shaped 
cells in which they placed the store of prepared pollen and 
the egg, and then individually sealed them, in this way 
obviating the necessity of sealing the outside or main tunnel 
to exclude intruders. This method gave excellent protection 
against injury by violence and the weather, for the cells 
containing the eggs or larvae were heavier than the little 
pots which the potter-wasps attach to twigs, and they 
equalled in thickness and warmth the mud walls of Trypox- 
ylon politum and they had in addition the protection of 
the deep burrow. These cells were oval, % inch in length, 
placed close together and were varnished on the inside with 
some special waxy substance. Fig. 12 shows a lump of mud 
with these brood pots. 
The bees continued to extend the tunnels by excava- 
tion and enlarge the chimneys by addition. They brought 
water from a mud-puddle in the road fifteen feet dis- 
tant, carrying the load in the gullet. With a portion 
of the water they would wet the hard, yellow clay, remove 
a mouthful of it, back out and apply it to the last ring in 
the chimney. The bees would carry the mud under the 
thorax with the front pair of legs, while the two hind pairs 
furnished locomotion; as the bee backed out of the nest to 
the opening, the ball of mud was passed to the hind legs, 
and she now held her footing with the front legs while with 
hind legs she slapped the mud onto the last layer and with 
many active thumps with the tip of the abdomen, punched 
and beat it into shape. “Punched” is really the right word 
correctly to describe the gesture. Entechnia taurea does 
similar work with much finer precision; in that species the 
bee divides the ball of earth into two portions, applies the 
first part to the center of the tube at the bottom, and care- 
fully smooths and works it on the left side almost to the top ; 
then she applies the second portion in the same way at the 
base and works it up on the right side. The result of this 
method is that, either through the builder having insufficient 
material, or from some other cause, there remains a split or 
open groove down the full length on the upper median side 
of the tunnel, where the two halves of the load of mud fail 
by only a narrow margin to meet. 
