Source : Webster's Revised Unabridged Dictionary (1913)

Bark louse \Bark" louse`\ (Zo["o]l.)
   An insect of the family {Coccid[ae]}, which infests the bark
   of trees and vines.

   Note: The wingless females assume the shape of scales. The
         bark louse of the vine is {Pulvinaria innumerabilis};
         that of the pear is {Lecanium pyri}. See {Orange
         scale}.