The Collaborative International Dictionary of English v.0.48:

caddis fly \caddis fly\, caddisfly \caddisfly\n.
   same as caddice fly.

   Syn: caddice fly, caddicefly.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

caddis fly
    n 1: small moth-like insect having two pairs of hairy membranous
         wings and aquatic larvae [syn: caddis fly, caddis-fly,
         caddice fly, caddice-fly]