Pedipalps

Definition

The second pair of appendages on the cephalothorax of chelicerate arthropods (arachnids, horseshoe crabs, and sea spiders), positioned lateral to the chelicerae and anterior to the walking legs. In arachnids, pedipalps are highly variable in form and function: scorpion pedipalps terminate in chelae (pincers) used for prey capture and defense; spider pedipalps resemble small walking legs in females and juveniles, while adult males possess enlarged, modified pedipalps that serve as intromittent organs for sperm transfer during mating. The term is also applied more loosely to the segmented, palp-like appendages of insect mouthparts (labial and maxillary palps), though these are not homologous to chelicerate pedipalps.

Etymology

From Latin pedi- (foot) + palpus (touching, stroking)

Example

Male wolf spiders (Lycosidae) can be distinguished from females by their swollen, bulbous pedipalp tips, which they charge with sperm prior to seeking mates; in contrast, the Mexican red-kneed tarantula (Brachypelma smithii) shows little sexual dimorphism in pedipalp structure, with both sexes bearing leg-like pedipalps used primarily for sensory exploration and manipulating prey.

Synonyms

• palps (loose)

Related Terms

• chelicerae
• Cephalothorax
• chelae
• labial palps
• maxillary palps
• intromittent organ
• Spermatophore
• arachnid
• chelicerata

Usage Notes

Specialists reserve 'pedipalps' for chelicerate appendages; insect mouthpart palps are termed 'labial palps' or 'maxillary palps' to avoid confusion. The singular 'pedipalp' is rarely used in practice; 'pedipalps' predominates even when referring to a single appendage. Sexual dimorphism in arachnid pedipalps is a key diagnostic character in spider taxonomy. Not to be confused with antennae or true legs—pedipalps lack the intrinsic musculature for walking and are innervated differently.