pedipalpen

Pedipalpen (pedipalps in English) are the second pair of appendages in chelicerates, a major subgroup of arthropods that includes spiders, scorpions, harvestmen, mites, and horseshoe crabs. They arise near the mouth and are distinct from the chelicerae (the mouthparts) and from the first pair of walking legs. Pedipalpen are typically segmented and can vary considerably in size, shape, and specialization among different groups.

In spiders, pedipalpen are often leg-like in adults. In males they are greatly modified to form the copulatory organs; the distal segments house a palpal bulb that delivers sperm to the female during mating via the embolus. In female spiders and many juveniles, pedipalps mainly function in handling prey, sensing the environment, and manipulating objects.

In scorpions, the pedipalpen are large, robust pincers (chelae) used to seize and crush prey and to defend against threats. In other chelicerates such as harvestmen and mites, pedipalps serve mainly as sensory or feeding limbs, sometimes specialized for grasping small prey or for locomotion assistance. Across groups, pedipalps frequently bear sensory hairs and contribute to prey detection and environmental interaction.

Pedipalpen are important in taxonomy and functional morphology, reflecting adaptations to specific ecological roles and mating behaviors across the chelicerates.