Tunnels 

 per sg In. 



1 

 10 



25 

 50 



75 

 *100 



Attack 



Rating 



• 



Trace 

 Slight 

 Moderate 

 Medium Heavy 

 Heavy 

 "Very Heavy 



♦NOTE: Eatings of around 100 per sq. in. Indicate tlie .mazimum density 

 "beyond which it is Impossible to count. 



Al.OU Illustrations of Borer Damage 



Figures 1 to 11, Inclusive, have heen selected' from a large 

 numher in the files of the Clapp Lahoratorles in order to show the 

 results of heavy attacks on test hoards and piles which were exposed 

 only k to 18 months each. One of the latter, shown in Figures 7 and 8, 

 although electrolytic-copper-sulphate treated, was ccaapletely destroyed 

 in l8 months, largely "by Teredo!! 



Figure 5 shows the results of the comMned attacks during 1^ 

 months in l^l<-7 "by crustacean Limnorla and molluscan Teredlnldae . 

 This attack was much more severe than that on a similar panel suhmerged 

 in the same harhor at Pensacola, Florida, during 8 months in 19^5; at 

 that time Teredo attacks riddled the "board, hut there was very little 

 evidence of Limnorla. 



