antenna

antenna (noun; plural antennae; Latin antenna, feeler): 1. Analogous, unsegmented structures in mollusks, polychaete worms and rotifers.

2. (Arthropoda) A movable sensory appendage of various arthropods; usually segmented and located on the head above the mouth parts; most arthropods bear antennae, although some are greatly reduced; missing in all arachnids.

3. (Arthropoda: Crustacea) The second antennae proper; the second pair of appendages posterior to antennules; primarily sensory in function, but often adapted for other functions; derived from appendages on primitive third preoral somite; postantennal appendages; no homologous appendage in insects

See also: antennua, antennule.