706 NATURAL HISTOEY OF AQUATIC ANIMALS. 



borings that it completely gave way under a ship-load of merchandise stored upon it. This pest 

 is not confined to pure sea-water, but occurs in the piles and timbers of wharves in harbors that 

 are not only brackish, but also muddy and contaminated with sewage. Capt. B. J. Edwards 

 told me that formerly when the cedar channel-buoys in Buzzard's Bay, Massachusetts, were not 

 taken up they would last not more than two years, owing chiefly to the attacks of this Teredo; 

 but under the present system there are two sets of buoys, which are alternately taken up and 

 put down every six months. After a set has been allowed to dry thoroughly they are scraped 

 to remove the barnacles, etc., and then receive a thorough coat of verdigris paint each time 

 before they are put down. With this treatment they will last ten or twelve years, but they 

 are more or less perforated and injured every year, until finally they become worthless. This 

 statement does not apply to the spar-buoys, which are taken up only once a year, in April 

 and May. Captain Edwards says that the Teredos would destroy an unpainted spar buoy in 

 one year, but when painted with verdigris they will only work where the paint becomes rubbed 

 off. They first attack buoys or piles just below the water's edge, but eventually will destroy 

 the entire submerged wooden portion. Commenting upon this information, Professor Verrill says: 



" Inasmuch as the Teredos produce their young all through the summer, and they develope to 

 a very large size in one season, it is evident that the best time to take up the buoys would be in 

 midsummer, before the early crop of young have grown large, and leaving too little time for the 

 later crop to become large, in the buoys thus put down, before winter, when most of them would 

 probably be killed by the cold weather. In this way the damage might be materially diminished, 

 if not inconsistent with the other duties of the oflicers of the vessels employed in this service. 

 There are, as yet, no means of estimating the extent of the damage done to our wharves, shipping, 

 etc., by this and the various other species of Teredo found on our coast, but, judging from their 

 abundance along the whole coast, it is much greater than is generally supposed. 



"The Teredo navalis is also abundant on the coast of Europe, from the Mediterranean and 

 Black seas to Christiania and the coasts of Great Britain. Its habits have been quite thor- 

 oughly investigated by several Dutch naturalists, owing to the great damage that it has done 

 on their coast, at times even threatening a general inundation of the country by destroying the 

 wood-work of the dikes. This Teredo occupies a zone of considerable breadth, for it often lives 

 considerably above low-water mark, and extends several i'eet below it, even to the depth of four- 

 teen feet, according to some writers. 



"The best remedies in common use to resist or prevent its attacks are copper sheathing, used 

 chiefly on vessels ; broad-headed nails, closely driven, used for piles and timbers ; creosote and 

 coal-tar, frequently applied. The various poisonous substances that have been applied to timber 

 for this purpose, however useful they may be in other respects, have little or no effect on the 

 Teredo, for it does not depend upon the wood for its food, and even protects its body externally 

 with a layer of shell, lining its holes. The only remedies that are likely to succeed are those 

 calculated to prevent the lodgment and entrance of the young ones beneath the surface. Even 

 creosote, thoroughly applied uu-.er pressure at the rate of ten pounds per square foot, has been 

 found insufficient to prevent their attacks, for piles thus treated at Christiania were found by Mr. 

 Jeffreys to be filled with the Teredo within two years after they were put down. 



" Several other species of Teredo also occur on this coast. The Teredo megotara has been found 

 in floating pine wood at Newport, Rhode Island, and in cedar buoys, etc., at New Bedford, Massa- 

 chusetts; as well as in Massachusetts Bay, at Provincetown, and other places; it is also found as 

 far south as South Carolina at least. This species sometimes grows to a large size, forming tubes 

 at least eighteen inches long. It sometimes occurs, also, in the piles of wharves in this region. 



