Source : Webster's Revised Unabridged Dictionary (1913)

Dobson \Dob"son\, n. (Zo["o]l.)
   The aquatic larva of a large neuropterous insect ({Corydalus
   cornutus}), used as bait in angling. See {Hellgamite}.

Hellgamite \Hell"ga*mite\, Hellgramite \Hell"gra*mite\, n.
   (Zo["o]l.)
   The aquatic larva of a large American winged insect
   ({Corydalus cornutus}), much used a fish bait by anglers; the
   dobson. It belongs to the Neuroptera.

Source : WordNet®

Corydalus cornutus
     n : large soft-bodied insect having long slender mandibles in
         the male; aquatic larvae often used as bait [syn: {dobson},
          {dobsonfly}, {dobson fly}]