110 THE ECONOMIC MOLLUSCA OF ACADIA. 



The time of breeding of this species differs somewhat with the 

 locality, but it takes place generally in the spring or summer months. 

 They are very prolilic. The young at first can swim freely about, but 

 in a very short time (one writer says four days) they are fully equipped 

 for their life work, and attaching themselves to wood, begin to bore 

 their tunnels. After entering the wood, they increase rapidly in size, 

 so that the adult burrows are many times larger than those by which 

 the young enter. It is thought that as a rule they do not live longer 

 than a year or eighteen months. They require pure salt water, free 

 from sediment, and cannot generally live in brackish or polluted 

 situations. Their tubes are sometimes ten inches long, but generally 

 not more than half that length. 



A piece of Teredo-bored wood shows but little outward trace of the 

 condition within. Except for the small holes made by the entering 

 young, it may appear quite sound, when in reality riddled by the 

 burrows and composed of almost nothing but their calcareous tubes. 



Along with the Teredo, there is frequently found a small crustacean, 

 Limnoria lignorum^ which also forms burrows and is very destructive. 

 They work, however, in different ways, for the latter attack only the 

 surface of the wood, and honey-combing it so thoroughly that nothing 

 is left but partitions between burrows, allow it to be easily destroyed by 

 the waves. As the outside is removed, they progress deeper, and so 

 rapidly do they work that an inch a year is frequent]}^ removed all 

 around the largest submerged timbers. The minute size of theburrows, 

 about one-sixteenth of an inch in diameter, and the absence of a 

 calcareous lining, as well as the presence of the crustacean itself, will 

 always distinguish its ravages from those of the Teredo. It largely 

 replaces the latter on those parts of the shores of Acadia where the 

 Teredo does little harm, i. e., on the Atlantic Coast of Nova Scotia and 

 around the Bay of Fundy, and it does great damage in these localities. 

 It is particularly destructive at Disby. The Teredo, on the other hand» 

 perforates the wood through and through, and makes it so fragile that 

 it will break under a slight shock. It seems to have little preference in 

 regard to the wood it attacks, the hardest and softest being equally 

 injured. The southern palmetto is said to withstand it. 



Economics. About the years 1730-32, great damage was 

 done to the dykes of Holland by this Teredo. A general sub- 

 mergance of the country was threatened, and the consequent 

 alarm led to the careful study of the habits and structure of 

 the animal. Since then, it has appeared in numbers at 

 different periods. In 1858 fresh alarm was caused, which 

 resulted in the appointment of a commission to investigate 

 the whole subject and experiment upon different methods for 



