The Collaborative International Dictionary of English v.0.48:

Bagworm \Bag"worm`\, n. (Zool.)
   One of several lepidopterous insects which construct, in the
   larval state, a baglike case which they carry about for
   protection. One species (Plat[oe]ceticus Gloveri) feeds on
   the orange tree. See Basket worm.
   [1913 Webster]