This new eerles was started in December 19^i|-. However, the attack 

 continued to "be as severe aa before, euad It appeared that even a 2-ln. 

 panel was not sufficiently thick to cairy a test through 8 months. It 

 was therefore requested on March 25, 19^5* that "blocks k Inches thick 

 he used. Increasing the thickness of the panels did not solve the 

 prohlem, however, because It was soon discovered that the attack was 

 Just as destructive to the thicker hlocke. The more wood present, the 

 greater became the number of horers infesting the panels, so that the 

 attack was Just as severe proportionately In the thicker panels as in 

 the thinner ones. 



As Increasing the thickness of the panels did not prolong their 

 life, it was decided to shorten the period of suhmergence and infesta- 

 tion to which the psmels had been exposed. Conseciuently, on November 6, 

 19^5> It was requested that the peuaels be removed emd replaced "by a new 

 series operated on a 4-month hasis, instead of on the 8-month hasls which 

 previously obtained. This change was made later the same month. However, 

 It was found that even after the period of suhmergence was reduced to 

 I months, the destruction of the panels was too rapid to permit making 

 accurate euialyses; so in Deoezoiber 19^6, this period was further reduced, 

 jfoilowlng the decision that 5 months was the longest practical period of 

 suhmergence . 



Teredlnidae occurred in 55 of the kl control panels, ranging from 

 minute pits or embryonic speclmciis to specimens up to 6^ mm In length. 

 One of these panels, submerged for oialy one month, was filled, ajtid 

 another was riddled. The hreeding season extends from March 9 to •^~ 

 December 20, but in 19^ and 19^7, it continued until Fehruary 20. 

 It is clearly apparent that the growth attained by the sets of 

 Teredlnidae that develop during the months >diich have warmer water 

 ten^erature is imich greater than the growth of those borers \diich 

 develc^ at either limit of the hreeding season. 



Teredlnidae occurred in all except one of the hj test panels, 

 the exception helng a panel that was removed during a change in panel 

 series, after having heen submerged for only 6 days. Maximum lengths 

 of 60 mm were recorded in one month, 93 mm in 2 months, and 2'4'0 in 

 5 months. Eight of these panels were filled; 9 were riddled; 12 were 

 more or less completely destroyed, although few had heen left submerged 

 for more than 5 or 4 months. The attack rated very heavy each year. 

 Including 19**^. 



2. Llmnoria . Idmnorla were more or less active throughout the 

 period covered hy the test but never occurred in particularly descruc- \ 

 tlve nuitibers. They occurred on 2k of the kl control panels hut not 

 on any control panel prior to Octoher 8, 19^. The largest number on a. 

 any one of these panels was 25O. Llmnoria occurred on 22 of the kj '^ 

 test panels. Their occurrence, even here, was Irregular and sporadic, 

 the attack rating from none to a trace most of the time. However, they 

 attained a low moderate peak in a panel removed on August 11, 19^5 > 

 after 8 months' submergence, and rated as slight on k of the panels 

 removed from July 20 to October 20 in 19k'Jf after 5 months' submergence. 



81 



