CAUSES OF DECAY AND DESTRUCTION OP TIMBER 265 
The Limnoria Terebrans, sometimes called the " boring 
gribble," and in Australia the " eobra," is always found in 
large numbers together, and in most parts of the world. 
It is only about the size of a grain of rice, in colour light 
grey, and very similar to the softer woods which it frequents; 
the only conspicuous points of the animal are the two black 
eyes. It can swim, crawl, and jump. 
The limnoria differs from the teredo, as it devours the 
wood and its tunnel forms both food and shelter. It 
attacks the wood by means of its mandibles or claws, and 
makes a very clear cut excavation. It works on the 
surface of timber so that its destructive work can be 
plainly seen, and when the wood is bored all over to the 
depth of perhaps half an inch it becomes brittle and is 
washed away by the movement of the water, thus affording 
fresh wood for the animal to act upon. The tunnels are 
only about half an iiich in length, slightly longer than the 
animal itself, and are beautifully formed ; like those of the 
teredo, they are usually parallel with the grain of the v,'ood 
(see Fig. 36). The multitude of these animals compensates 
for their small size. Not long ago, when examining the 
work of this creature on a piece of wood 10 inches square 
by 3 inches thick, the author placed it in a pail of salt 
water with the intention of keeping up life, but without 
success ; hundreds of these animals came out of the wood, 
and the water looked Just as though a couple of handfuls of 
rice had been thrown in. The limnoria often works in 
conjunction with the teredo, but it also infests the waters 
of colder seas where the teredo cannot exist, and has thus a 
wider range. It attacks most kinds of wood, even light 
scantlings of greenheart after a time, but prefers soft woods, 
and will eat pitch pine at the rate of half an inch a year on 
the northern coasts of Britain. Like the teredo, it also 
works from about half-tide level down to the ground, and is 
