antennula

from The Century Dictionary.

• noun A little antenna.
• noun A filiform appendage of an antenna, as in some crustaceans.
• noun The appendage of the segment or somite of the head of an arthropod in advance of that bearing the antennæ proper; one of the anterior of the two pairs of feelers of the head of a crustacean. Commonly called the short feeler. See cuts under Copepoda, Cyclops, and Cythereidæ.
• noun Also antennule.