1S9 



of tlu- (irg.misnis. Jusl as tliere are certain years when fruits or t;rains are exception- 

 ally al>un(lanl, so there are years when teredos a|)pear in certain localities in extra- 

 ordinary numbers. Some of the conditions influencing the varying intensit\- of attack 

 from year to year will he discussed in a later chapter. 



Such recurring attacks of Teredo ha\e resulted in a number of spasmodic in\esti- 

 gations, stimulated Iw the immediate necessities of the situation, and left incompleted 

 when the spur to action disappeared through the intervention of natural agencies of 

 control. OnK- the prospect of sudden calamity-, or tlie unexpected in\asion of a new 

 locality has aroused general interest in the matter. 



From the time of Pliny until about the sixteenth centur>- the shi[)\\(irm appears 

 to have fallen (|uite into obli\ion in l-.urope. I'oUowing the discover^' of America, it 

 was reported as something new and unusual that in the West Indies ships were seri- 

 ously damaged by a borer which occurred there. When a little later it was obser\ed 

 that similar organisms were occasioning damage along the coasts of Europe, the 

 earlier accounts of Greek and Latin writers were forgotten and it was generally agreed 

 that the borers had been introduced by ships from foreign lands. Even Linnaeus 

 shared this oi^inion, antl stated in his description of Teredo navalis that it had been 

 imported from India. 



It seems more probalile, ho\ve\er, that the occurrence of the shipworm in ICurope 

 had merely escaped general notice during the middle ages, its rediscovery being 

 contingent on circumstances, chief among which was the erection of chkes along 

 the coasts of Holland. The first dykes, which were made by driving piles and heaping 

 up earth behind them, were erected in l.Sf)(). Within a few years it was noticed that 

 the piles were being damaged, hut apparently there occurred no serious attack until 

 about 1700, when the d\kes l)ecame damaged to such an extent that inundation of 

 the country was threatened. 



The forced practical interest in marine borers which the inhabitants of the 

 Netherlands took at this time occasioned the first serious investigation of these 

 organisms and resulted in a considerable advance in knowledge regarding them. A 

 number of treatises on the natural history of the shipworm appeared during the en- 

 suing half century, foremost among which is the work of Sellius published in 17,S3, a 

 work of unusual merit for that period and one which retains its place as a classic 

 of the literature on marine borers. 



There ha\e been since the time of Sellius some ti\e hundred published references 

 to marine borers, for the most part fragmentary and of little scientific worth, but 

 with a few notable exceptions, which will be referred to farther on. In all this volume 

 of literature, however, there is to be found no single comprehensive account of the 

 biological aspects of the marine borer problem in relation to possible methods of 

 control. 



The natural history of the various species of borer is far from being a matter 

 merely of theoretical or academic interest. It cannot be too strongly emphasized 

 that any method of combating the ravages of these organisms must depend for its 

 success on a recognition of the biological factors involved. It has not infrequently 

 occurred in the past that time and money have been invested in proposed methods 

 of protection, the failure of which could ha\'e been predicted by the biologist on a 

 priori grounds. 



From the point of view of the engineer it is of the highest importance to know 

 the various species of borer with which he has to deal, and regarding each, its breeding 

 season, larval habits, distribution, method of attack, the rapidity with which it de- 

 stroys piling, and the various ecological factors which may alter any of these. In 



