MATERIALS. 133 



blade of a penknife can make no impression upon them. I feel 

 quite sure that, after an inspection of these, it will be readily 

 conceded that the animal is perfectly well able to bore away 

 to its heart's content, without having to resort to the secretion 

 of acid or to any other aid. 



I have never heard any question raised as to how the larvse 

 of the goat moth (Cossm Ligniperda), leopard moth (Zeuzera 

 JEscidi), or those of the " Clearwing " family and other wood- 

 eating insects, eat into the solid heart timber of elms, oaks, 

 poplars, etc., and I am unable to understand why the Teredo 

 should not be credited with similar powers. 



The T. navalis attains a length of 18 inches to 2 feet, and 

 bores holes up to | inch in diameter. It usually 'grows to a 

 larger size in warm latitudes than in the colder ones ; but I have 

 seen timber as far north as Thurso (58 3G' N. Lat.) riddled with 

 Teredo holes, some of which I could put my finger into. The 

 holes do not, however, usually exceed f to J inch in diameter, 

 and the worms commonly found are not more than from 6 to 8 

 inches long. 



There is a very large species of Teredo (T. giganted) which 

 inhabits the East Indian and China seas, It is said to attain a 

 length of nearly 6 feet, and to measure 3 inches in diameter 

 at its thickest part. It seems chiefly to inhabit shallow water, 

 amongst mangrove trees, and is not so much to be feared as the 

 smaller species. 



Although the Teredo attacks submerged timber at all 

 moderate depths, it, like the other timber pests, is most active 

 between low water of spring tides and high water of neaps. 



I have already mentioned Limnoria terebrans and Chelura 

 terebrans. These are small crustaceans, scarcely less formidable 

 than the Teredo. They are akin to, and somewhat resemble 

 respectively, small wood-lice and sandhoppers. They do not 

 measure more than from -^ to J of an inch in length. 



I have seen piles of pitch pine so perforated by them that 

 large pieces, almost resembling sponge, and easily crushed by the 

 hand, could readily be detached. 



They appear to work chiefly in the cellular tissues of the 

 wood, and therefore generally attack the ends of timbers first ; 

 but the harder woody fibre is by no means proof against them. 

 Both they and the Teredo seem to be very fond of getting into 

 timber through joints and bolt-holes. 



