202 THE WORLD'S LUMBER ROOM. 



tunnels in submerged timber, and does its work so quickly 

 that a piece of hard sound wood is completely riddled in 

 five or six weeks. 



Though extremely useful in its right place, it has at 

 times done much mischief; and it is as a protection against 

 its ravages that ships are sheathed with copper, and the 

 timbers of piers and jetties, &c., are studded with iron nails, 

 the rust from which soon spreads over the whole surface and 

 renders it unpalatable. Dockyards have sometimes suffered 

 much from it ; and the Dutch have been greatly alarmed by 

 its attacks on the wooden piles supporting the all-important 

 dykes which alone preserve their country from being flooded 

 by the North Sea. 



The pholas, rock-boring Venus, &c., already mentioned 

 as piercing stone, also help to clear away dead wood. 



But to return to the land, where there are numerous 

 other removers of dead vegetable matter. In the tropics a 

 large proportion of insects of all orders, but especially 

 beetles, are more or less dependent upon vegetable matter, 

 particularly bark, timber, and leaves in various stages of 

 decay, and the number and variety of insects which may be 

 collected in a given time depends upon the number of 

 trees which have been or are being cut down. In the 

 Aru Islands, we are told by Mr. A. R. Wallace, no sooner 

 is a tree felled than it is attacked by swarms of little wood- 

 borers, hundreds of which perish from their over-eagerness, 

 being glued into their holes by the outflow of sap. 



Numerous species of small beetles lay their eggs in dead 

 wood, and the larvae, as soon as hatched, begin making tiny 

 galleries in all directions. A quantity of oak timber was 



