The Collaborative International Dictionary of English v.0.48:

Hellgamite \Hell"ga*mite\, Hellgramite \Hell"gra*mite\, n.
   (Zool.)
   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.
   [1913 Webster]