204 THE WORLD'S LUMBER ROOM. 



(Fig. 41) and goat-moths feed on decaying timber, and as the 

 latter spend about four years in the caterpillar state, appa- 

 rently never ceasing to eat, they bore considerable tunnels not 

 only in fallen trees, but in those which, but for them, might 

 long remain standing. The goat-moth caterpillar when full 

 grown is three inches or more long and as thick as a man's 

 finger ; and since as many as sixty-seven have been found 



Fig. 41. THE WOOD-LEOPARD MOTH. 



in the mere splitting of a piece of trunk two feet long, it 

 is no wonder that many an elm and willow are unable to 

 stand against the wind after being colonised by them. 



It is perhaps when we consider the vast amount ot 

 damage which wood-eating insects inflict upon us, that we 

 best realise the great services they also render, for in a fully 

 cultivated country it is the havoc which they play that 

 chiefly comes under our notice. 



Certain fly-grubs also feed on rotten wood, decaying 

 roots, &c. ; the jet ant makes its nest in decaying trees, and 



