376 



THE STUDY OF INSECTS 



those cells that is closed will be found either a mass of pollen and nectar 

 with an egg upon it or a larva feeding on the food stored for it. 



The most striking feature of these nests is the fact that several 

 bees use the corridor as a passage-way to the cells they are building and 

 provisioning. But this corridor is not a public one; it is constricted at 

 its outer end and is guarded by a sentinel whose head nearly fills the 

 opening. When a bee comes that has a right to enter, the sentinel backs 

 into the wider part of the corridor and allows it to pass and immediately 

 thereafter resumes its guarding position with its head closing the opening 

 of the corridor. 



Anthophora.- — -The genus Anthophora is widely distributed and in- 

 cludes many species, more than eighty have been described from North 

 America alone; but the habits of only a few of these have been described. 



The nests of those American species the habits of which are well 

 known are usually built in steeply inclined or perpendicular banks of 

 earth, preferably in those of compact clay; they are also excavated in the 

 clumps of clay held between the roots of stumps in stump-fences. In the 

 West a favorite nesting place of these bees is in the walls of sun-dried 

 bricks of the adobe houses. Like Halictus and Andrena, the bees of this 

 genus are gregarious, hundreds of individuals building their nests close 

 together in the same bank of earth. 



A striking feature of these nests is the presence of a cylindrical tube 

 of clay extending outward and downward from the entrance of the tunnel. 

 This tube is rough on the outside but smooth within. It is composed of 

 small pellets of earth compacted together. These pellets when brought 



Fig. 627. — Section of a bank with nests of Anthophora. (Photographed by Miss P. B. Fletcher.) 



out from the tunnel are wet and easily molded into the desired form, but 

 soon become dry and firm (Fig. 627). 



Andrena. — Among the larger of our common mining bees are certain 



