The Collaborative International Dictionary of English v.0.48:

Muckworm \Muck"worm`\ (m[u^]k"w[^u]rm`), n.
   1. (Zool.) A larva or grub that lives in muck or manure; --
      applied to the larvae of the tumbledung and allied
      beetles.
      [1913 Webster]

   2. One who scrapes together money by mean labor and devices;
      a miser. "Misers are muckworms." --Pope.
      [1913 Webster]