Eightlegged

Eightlegged is an adjective used to describe organisms that have eight legs. In formal scientific writing, the hyphenated form eight-legged is standard; eightlegged without a hyphen is far less common and typically appears in nontechnical contexts or as a brand or product name. The term emphasizes leg count as a key identifying feature, but does not by itself determine taxonomy.

The concept primarily applies to the class Arachnida, whose best-known eight-legged members are spiders (Araneae) and scorpions (Scorpiones). Other eight-legged arachnids include harvestmen or daddy longlegs (Opiliones) and the mites and ticks (Acari). While all adult arachnids generally have eight legs, larval stages of some groups may start with six legs and gain the remaining pairs after metamorphosis or molting (notably in Acari).

Anatomy and variation: Most eight-legged arachnids have a two-part body, the cephalothorax and the abdomen, and use their eight legs for locomotion, sensing the environment, and manipulating prey. Pedipalps and chelicerae serve sensory, feeding, and reproductive roles. In Opiliones the body appears broadly fused, giving a single, capsule-like appearance, whereas spiders and scorpions show more distinct segmentation.

Ecology and behavior: Eight-legged arachnids occupy a wide range of habitats, from leaf litter to the forest canopy, deserts to wetlands. Many spiders spin silk for prey capture or shelter; scorpions use pincers and a stinger for defense. Despite their diversity, eight-legged animals share a common limb plan that shapes their interactions with ecosystems.