516 



Saw-flies, Gall-flies, Ichneumons, 



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 stanfordiana, 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 



