The Collaborative International Dictionary of English v.0.48:

Tumbledung \Tum"ble*dung`\, n. (Zool.)
   Any one of numerous species of scaraboid beetles belonging to
   Scarabaeus, Copris, Phanaeus, and allied genera. The
   female lays her eggs in a globular mass of dung which she
   rolls by means of her hind legs to a burrow excavated in the
   earth in which she buries it.
   [1913 Webster]