The Collaborative International Dictionary of English v.0.48:

Spindleworm \Spin"dle*worm`\, n. (Zool.)
   The larva of a noctuid moth (Achatodes zeae) which feeds
   inside the stalks of corn (maize), sometimes causing much
   damage. It is smooth, with a black head and tail and a row of
   black dots across each segment.
   [1913 Webster]