as Teredlnldae or Pholadldae do not develop sufficiently to do much 

 damage. 



This is true m the cold Waters of Uewf oundland and vicinity, 

 where large numbers of emhryonic Teredo often occur, hut die hefore 

 they can emhed themselves in the test hoards. For this reason, it is 

 concluded that in evaluating Teredinidae and Pholadidae attacks it is 

 more useful to record the size and number of tunnels, that is, the 

 degree of attack, than to count the exact number of borers. Thus a 

 reading of even 500 minute pits vould be recorded only as a "trace", 

 from the standpoint of attack, if the borers vhich made the pits did 

 not live to make destructive tunnels. Limnoria attacks, however, can 

 be accurately rated by a careful count of the ntonber of borings. 



b. Scale of Ratings . This scale is used as a general guide 

 in evaluating the degree of attack on the standard test board (nine 

 blocks or panels, 8-month ba^is) by three of the most destructive species 

 of borers. 



Teredinidae 



Number of tunnels 



per block or panel , Attack Rating 



Up to 5 .Trace 



6 to 25 Slight 



26 to 100, or 25^ filled Moderate 



101 to 250, or 50^ filled Medium Heavy 



Over 250, or 75^ filled Heavy 



Filled, riddled, or destroyed Very Heavy 



Pholadidae 



Up to 5 Trace 



6 to 20 Slight 



21 to 50 Moderate 



51 to 100 Medium Heavy 



101 to 200 Heavy 



Over 200, filled, or riddled Very Heavy 



