52 STRANGE DWELLINGS. 



burrow, in which it resides, and which supplies it with nourish- 

 ment as with a residence. The tunnels which it makes are 

 mostly driven in an oblique direction ; so that when a large 

 number of these creatures have been at work upon a piece of 

 timber, the effect of their united labours is to loosen a flake of 

 variable dimensions. As long as the weather is calm, the 

 loosened flake keeps its position ; but no sooner does a tempest 

 arise, than the flake is washed away, and a new surface is 

 exposed to the action of the Chelura. 



When the Chelura is placed on dry land, it is able to leap 

 nearly as well as the sand-hopper, and performs the feat in a 

 similar manner. 



This is not the only wood-boring crustacean witi-^ which our 

 coasts are pestered ; for the Gribble {Limnoria terebrans) makes 

 deeper tunnels than the preceding creature, though it is not so 

 rapidly destructive, owing to the direction of its burrows, which 

 are driven straight into the wood, and do not cause it to flake 

 off so quickly as in the case when the Chelura excavates it. 

 Still, it works very great harm to the submerged timber, boring 

 to a depth of two inches, and nearly always tunnelling in a 

 straight line, unless forced to deviate by a nail, a knot, or 

 similar obstacle. The Gribble is a very tiny creature, hardly 

 larger than a grain of rice, and yet, by dint of swarming 

 numbers, it is able to consume the wooden piles on which 

 certain piers and jetties are supported ; and in the short space 

 of three years these destructive Crustacea have been known to 

 eat away a thick fir plank, and to reduce it to a mere honey- 

 comb. Sometimes these two wood-boring shrimps attack the 

 same piece of wood, and, in such cases, the mischief which 

 they perpetrate is almost incredible, considering their small 

 dimensions and the nature of the substance into which they 

 bore. The common fresh- water shrimp, so plentiful in our 

 brooks and rivulets, is closely allied to the Gribble, and will 

 convey a very good idea of its appearance. In some parts of 

 our coasts the ravages of these animals are so destructive, that 

 the substitution of iron or stone for wood has become a necessity. 



