Althou^li fres to move atout on wooden surfaces, they usually continue 

 to iDurrow close to their starting point. Usually very numerous, and 

 living on the wood suhstance, they soon i^educe the surface of the wood 

 to a network of interlacing "burrows which are readily eroded "by 

 movement of the water, thus .enahling the "borers to continue drilling 

 deeper into the wood. 



There are many examples of untreated piles which are "being 

 destroyed hy Limnoria ,at the rate of one inch per year. Even heavily 

 creosoted wood is not immune from attack hy these ravenous animals, and 

 it sometimes suffers serious damage. Limnoria retains its free-swimming 

 ahility throughout the adult stage, thus it is ahle to move, when 

 disturhed, to a more congenial hahitat. On piling, the attack is usually 

 most intense from half tide to slightly helow low tide. However, 

 destructive attack has often occurred from the low-tide level down to 

 the mud line, at depths that may reach 70 feet. 



AI.05 Method of Detecting and Bating Borer Attacks 



1. Detection . Standard test hoards, suhmerged at various 

 depths and examined at regular intervals, are the most practical means 

 thus far devised for detecting the various species of "borers and/or 

 fouling- organisms which occur in a given area. The severity of "borer 

 attacks is determined in accordance with a standard rating scale which 

 ranges from "trace" to "very heavy." 



In this way valuatle data have "been accumulated from harhors 

 all over the world on density of "borer attack, rate of destruction, 

 "breeding seasons, dlstri"bution of the various species, length of life, 

 rate of growth, and other significant factors relative to "borer 

 activity and destructiveness. 



Standard test "boards (see paragraph AI.08) are now "being 

 operated "by the William F. Clapp Laboratories at more than 5OO 

 locations along "United States coeists. The infoimation thus "being 

 collected and analyzed as to the hahits and life histories of "boring 

 organisms is proving valua"ble to designers and "builders of marine 

 structures and to those responsi"ble for the maintenance and protection 

 of such structures. 



2, Ratings for Evaluating Borer Attacks -on Test Boards . 



a. Severity of Attack . Study of data accumulated from a 

 large num"ber of test "boards shows clearly that a mere count of the 

 num'ber of horers is not a true indication of the severity of their - 

 attacks. It has heen o"bserved that many em"bryonic forms of species such 



