Source : Webster's Revised Unabridged Dictionary (1913)

Bark beetle \Bark" bee`tle\ (Zo["o]l.)
   A small beetle of many species (family {Scolytid[ae]}), which
   in the larval state bores under or in the bark of trees,
   often doing great damage.

Source : WordNet®

bark beetle
     n : small beetle that bores tunnels in the bark and wood of
         trees; related to weevils