Palmerworm \Palm"er*worm`\, n. (Zool.)
   (a) Any hairy caterpillar which appears in great numbers,
       devouring herbage, and wandering about like a palmer. The
       name is applied also to other voracious insects. --Joel.
       i. 4.
   (b) In America, the larva of any one of several moths, which
       destroys the foliage of fruit and forest trees, esp. the
       larva of Ypsolophus pometellus, which sometimes appears
       in vast numbers.
       [1913 Webster]

Palmer-worm
   (Heb. gazam). The English word may denote either a caterpillar
   (as rendered by the LXX.), which wanders like a palmer or
   pilgrim, or which travels like pilgrims in bands (Joel 1:4;
   2:25), the wingless locusts, or the migratory locust in its
   larva state.