Source : Webster's Revised Unabridged Dictionary (1913)

Jointworm \Joint"worm`\, n. (Zo["o]l.)
   The larva of a small, hymenopterous fly ({Eurytoma hordei}),
   which is found in gall-like swellings on the stalks of wheat,
   usually at or just above the first joint. In some parts of
   America it does great damage to the crop.

Source : WordNet®

jointworm
     n : larva of chalcid flies injurious to the straw of wheat and
         other grains [syn: {strawworm}]