antenna (biology)

One of a pair of specialized sensory appendages on the head of an invertebrate animal; insects typically have one pair, crustaceans two pairs; varies in shape and size: long and thin in shrimps, feather-like in moths, club-shaped in weevils.

Antennae (singular antenna) are paired appendages connected to the front-most segments of arthropods. In crustaceans, they are biramous and present on the first two segments of the head, with the smaller pair known as antennules. All other arthropod groups, except chelicerates and proturans which have none, have a single, uniramous pair of antennae.

In insects, olfactory receptors on the antennae bind to odour molecules, including pheromones.

The three basic segments of the typical insect antenna are the scape (base), the pedicel (stem), and finally the flagellum, which often comprises many units known as flagellomeres (the number of flagellomeres can vary greatly, and is often of diagnostic importance). True flagellomeres have a membranous articulation between them, but in many insects, especially the more primitive groups, the flagellum is entirely or partially composed of a flexible series of small annuli, which are not true flagellomeres. In many beetles and in the chalcidoid wasps, the apical flagellomeres form a club, and the collective term for the segments between the club and the antennal base is the funicle (or funiculus); for traditional reasons, in beetles it is the segments between the club and the scape, but in wasps, it is the segments between the club and the pedicel. In the groups with more uniform antennae (for example: Diplopoda), all segments are called antennomeres.