Antennarity

Antenarity is the biological condition of possessing antennae, the paired sensory appendages that arise on the heads of many arthropods. The term is used in morphology and systematics to describe the presence, absence, and variation of these structures across groups such as insects, crustaceans, and myriapods.

In insects, antennae are typically a single pair located on the head and serve as a principal sensory organ for chemoreception and mechanoreception, assisting in locating food, mates, and environmental cues. Their shape and segmentation can vary widely, with forms ranging from threadlike to clubbed, and from simple to highly elaborate antennal surfaces equipped with sensory sensilla.

In crustaceans, antennae can include two functional pairs: the larger antennae and the smaller antennules. These structures are often prominent in feeding, navigation, and chemical sensing in aquatic environments. Some crustaceans and early arthropod lineages show extensive diversification or reduction of antennal structures.

Not all animals with sensory heads have antenarity as defined for arthropods. For example, arachnids lack true antennae, and other coastal or fossil groups may exhibit modified or reduced antenna-like structures. In taxonomic descriptions, antenarity is a key character for identifying and comparing species and higher taxa, and its evolution reflects ecological adaptations and sensory requirements.

In summary, antenarity describes the presence and form of antennae, a central feature in the morphology and taxonomy of many arthropods.