The Collaborative International Dictionary
bait bug
Hippa \Hip"pa\, Hippe \Hip"pe\, n. (Zo["o]l.) A genus of marine decapod crustaceans, which burrow rapidly in the sand by pushing themselves backward; -- called also bait bug. See Illust. under Anomura.
Wiktionary
bait bug
n. A crustacean of the genus ''Hippa'' found burrowing in sandy beaches.