NESTS OF THE POLYBIA. 505 



increase in size, the Wasp builds ujd the walls of the cells, so 

 as to accommodate them, and then places over them a covering 

 of thin paper. Scarcely has she done this than she proceeds 

 to place another layer of cells upon the cover, and, as the 

 vk^orker wasps are hatched, they build cells at such a rate that 

 layer after layer may be seen in one nest, each being placed on 

 the cover of the preceding layer. 



The Polybia does not seem to be very particular as to the 

 material on which it supports its nest, though a large leaf is 

 generally a favourite locality. There are numbers of these 

 curious habitations in the " Nest Koom " of the British Museum, 

 and very variable they are. One of them looks just like a huge 

 brown sausage, round which a series of strings had been tied 

 about an inch apart. These represent the layers of combs which 

 are placed regularly inside the protecting cover. It is remark- 

 able, by the way, that some of the large wasps called Chartergus, 

 which hang their nests to the branches of trees, act in a very 

 similar manner. 



