Saw-flies, Gall-flies, Ichneumons, 
5 l6 
fertile eggs) called workers combine to build a common nest and numerous, 
brood-cells, in which eggs are deposited by a single queen female, the mother 
of the whole community. With this division of labor has come to exist a 
certain differentiation of structure, manifest in a difference in size and in some 
anatomical details between the working females and the egg-laying female. 
But with the bees certain interesting gradations in domestic economy 
or insectean sociology exist which throw some light on the possible line 
of progression or specialization from strictly solitary to strictly communal 
life. Numerous technically “ solitary ” bees show a marked gregariousness, 
a fondness, as it were, for the company and society of other individuals of 
their kind. This is chiefly manifested in the building of many nest-burrows 
close together, forming a sort of village or colony of homes, each home belong¬ 
ing to a single female, built by her, provisioned by her, and the young issuing 
from it her own offspring, but all these homes belonging to individuals of 
one species of gregarious or social inclination. Near Stanford University* 
Fig. 721. —Diagrams of nest-burrows of short-tongued mining-bees. B> nest of Andrena; 
A, compound nest of Halictus. 
in a roadside cutting exposing a clayey bank, lived a few years ago a great 
colony of the large mining-bee Anthophora stanjordiana , the vertical, open- 
mouth nest-burrows set about as closely as they could be without breaking 
into each other. This bee does not store up food in the nest, but brings it 
to the larva, the burrow not being closed. The whole colony covered but a 
