206 



INSECT ARCHITECTURE. 



the level of the water, an operation well described by 

 Scopoli, Swammerdam, and Rt'aumur. The excava- 

 tions are always proportioned to the size of the in- 

 habitant; and consequently, when it is young and 

 small, the hole is proportionally small, though, with 

 respect to extent, it is always at least double the 

 length of its body. The hole, being under the level 

 of the river, is always filled with water, so that the 

 grub swims in its native element, and while it is se- 

 cure from being preyed upon by fishes, it has its own 

 food within easy reach. It feeds, in fact, if we may 

 judge from its egesta, upon the slime or moistened 

 clay with which its hole is lined. 



A'fiitj cf the Gruhs of Ephemera. 



A. The grab. B. Perforations in a river bank. C. One laid 

 open to sliow tlie parallel structure. 



In the bank of the stream at Lee in Kent, we had 

 occasion to take up an old v/illow stump, which, pre- 

 vious to its being driven into the bank, had been per- 

 forated in numerous places by the caterpillar of the 



