76 INSECT ARCHITECTURE. 



till she has spread fifteen or sixteen layers one above 

 the other, rendering the wall altogether nearly two 

 inches thick. The several layers are not placed in 

 contact like the layers of a piece of pasteboard, but 

 with small intervals or open spaces between, ap- 

 pearing somewhat like a grotto built with bivalve 

 shells, particularly when looked at on the outside. 

 This is probably caused by the insect working in a 

 curvilineal manner. 



Section of the SociaJ-Wa!;p''s Nest. — a «, the external wall ; 

 b, cc, five small terraces of cells for the neuter wasps; d d, ce j 

 three rows of larger cells for the males and females. 



Having finished the ceiling, she next begins to 

 build the first terrace of her city, which, under its 



