UTAH ACADEMY OF SCIENCES 17 
As the larvae increase in size the waxen cell is en- 
larged but they evidently remain in one cell until about 
ready to pupate. The waxen cells are then larger than 
the thumb and somewhat irregular in shape as the soft 
walls rather shape themselves around the larvae. In 
spinning their cocoons, however, each larva builds for him-: 
self an ample papery cocoon. 
Besides the breeding cells, the nests contained two 
other kinds of cells not usually found in the nests of the 
common American species. These were the honey pots 
and the pollen tubes. The honey pots were round waxen 
cells open at the top and filled with honey. They differed 
from the old cocoons which were also utilized as honey 
pots in their form and size and in that they were com- 
posed entirely of wax. 
The pollen tubes were long cylindrical cells of soft 
wax situated on the outside of the nest and extending 
from the bottom to the top of the nest like chimneys. 
This nest contained four of these placed about an equal 
distance apart. They were filled to within one-fourth inch 
from the top with pollen packed into a firm uniform 
mass. . 
The nest contained about sixty individuals and was 
remarkably free from parasites. The body of a mutilated 
Psithyrus was found under the nest where the bees had 
thrust her after tearing off her wings and the most of 
her legs and pubescence. 
While the nests of the bumble bees are of particular 
interest in that they form an important link between the 
solitary and the permanently social bees, yet the bees of 
the genus Osmia are probably the master builders of the 
bee kingdom. In no other genus are the places chosen 
for the nest or the forms of the cells so diverse. 
Only a few of these have as yet been studied but 
each one has its own method of building its home. Some 
dabble in clay, others form their nests of dainty hued 
vegetable fibres; but wherever the cells are placed the 
bee itself seldom makes the excavation but places them 
in some convenient cavity. 
