122 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



Their breeding or hiding places are usually easily found and 

 destroyed, or sliced potatoes or substances poisoned with 

 Paris green may be placed where the sow-bugs can find them. 

 Some members of this same order live in fresh water, others 

 are marine. 



The gribbles, genus Limnoria, are another group of crus- 

 taceans that are very destructive to piles and other submerged 

 woods, which they may completely honeycomb to the depth of 

 half an inch or more. Where abundant they may cause the 

 piles to lose as much as an inch of surface each year. It is a 

 common practice now to give the piles a coat of creosote, or 

 better still to drive the creosote into the wood by pressure, in 

 order to protect it from the ravages of these and other wood 

 boring species. These gribbles attack and destroy much 

 floating and water-logged timber that might otherwise become 

 serious obstructions to navigation. 



