88 BARNARD 



pilings in which the creatures live are a product of mankind. Induced 

 populations are those infesting wooden test blocks which had been placed 

 in the harbor. 



Laboratory populations were kept in gallon jars half full of filtered, 

 unaerated seawater. Best culture results were obtained when the animals 

 were removed from the originally infested wood collected in the harbor 

 and transferred to clean blocks of Douglas Fir. These blocks had been 

 soaked and washed in seawater for a month prior to use in order to 

 remove sap and other pollutants, as newly immersed wood produces a 

 gelatinous exudate which traps and kills the animals when they attempt 

 to cling to it. Seawater was filtered to remove diatoms, other organisms, 

 and silt, then stored at about 8° C. in order to prevent bacterial growth. 

 Although the harbor water in which the chelurids live contains these 

 filtered agents the same water, though aerated, soon becomes stale. 

 Chelurid populations were maintained in the aquaria for about two years, 

 although the water temperature ranged from 17° to 23° C, about 8° 

 above the range in the harbor. 



Wood originally infested in the harbor and brought to the laboratory 

 was unsatisfactory for maintaining cultures both because of the high 

 concentration of animals per unit of water and because of the presence 

 in most of the wood of preserving agents which soon contaminate the 

 water. Successful cultures were maintained only with fewer than 200 

 animals in each aquarium. 



BURROWS MADE IN THE LABORATORY 



Blocks of Douglas Fir exposed to chelurids in the laboratory within 

 two weeks showed evidence of erosion, consisting of a surface furrowing 

 in the soft layers of the wood between the darker and harder annular 

 rings (fig. IC). The longer the exposure, the deeper and longer the fur- 

 rows became (figs. ID, 2E, F). The wood blocks were placed so that 

 the same side always faced the outside light. In each of the experiments 

 the original furrowing started on the darker sides of the block and as 

 the furrows were extended toward the lighter side their increasing depth 

 apparently provided shade for the animals. 



After exposure to the chelurids for periods up to 24 months, the fur- 

 rows were two to three times as deep (5-7 mm) as the height of the 

 animals. Examination of the furrows under a stereomicroscope showed 

 the concave surfaces to be quite smooth. 



