The Collaborative International Dictionary of English v.0.48:

Bark beetle \Bark" bee`tle\ (Zool.)
   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.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bark beetle
    n 1: small beetle that bores tunnels in the bark and wood of
         trees; related to weevils