2 Metaphors for twitch

The forgotten training soon comes back to our invaluable auxiliary; a mere twitch of the ear is a sufficient hint for her to retire at the right moment, and wait for the corn that is in variably given in exchange for the cryptogam.

There was mockery in every glance of his dull eyes; every twitch of his mouth was a fleer; with each gesture he seemed making game of one; sneering incredulity was stamped all over him.

2 Metaphors for  twitch