HYMENOPTERA. 363 
occupy themselves in building new cells, and in raising the wall 
of enclosure which is to protect the nest. This wall, formed of 
wax, starts from the base and raises itself, like a vertical rampart, 
from every point in the circumference. They then surmount 
this by the first roof, which is flat, supported by some pillars, 
and in which they have left one or two irregular openings. The 
whole is finally protected by a hemispherical covering of moss, 
made into a sort of felt and lined with wax. Fig. 330 represents, 
in its entirety, a nest of this humble bee. 

Fig. 335.—Nest of the Moss Humble Bee (Bombus muscorum). 
The workers also take their part in rearing the eggs. They 
bring the paste, which they slip into the cells to the larvee by 
a small hole, which is shut immediately afterwards. Later, they 
again give their assistance in disengaging the pup from their 
envelopes. In short, they make themselves generally useful ; 

