Metatarsus

Definition

In arthropods, the penultimate segment of the leg, located between the tarsus and the tibia. In arachnids, the metatarsus is particularly conspicuous as a long, often slender segment that precedes the multiarticulate tarsus; it is absent or indistinct in many insects, where the tarsus attaches directly to the tibia. The term derives from mammalian anatomy but was extended to arthropod leg segmentation by analogy of position.

Etymology

From Greek meta- (after, beyond) + tarsos (the ankle or tarsus), referring to its position distal to the tarsal region in the original mammalian usage

Example

In spiders (Araneae), the metatarsus is typically the longest leg segment and bears critical sensory structures such as trichobothria and lyriform organs used for vibration detection; its length and setation pattern are important taxonomic characters distinguishing families such as Lycosidae from Salticidae.

Related Terms

• Tarsus
• tibia
• Femur
• patella
• Coxa
• Trochanter
• pretarsus
• podomere
• Trichobothrium
• leg segmentation

Usage Notes

In arachnology, 'metatarsus' is unambiguous and universally applied to the segment between tibia and tarsus. In entomology, usage is more variable: many insects lack a distinct metatarsus, and some authors restrict the term to groups where a recognizable penultimate segment exists (e.g., some Heteroptera, Odonata nymphs). When describing insect legs, specialists often prefer 'basitarsus' for the proximal tarsomere rather than 'metatarsus' to avoid confusion with the arachnid structure. The plural 'metatarsi' follows standard Latin/Greek arthropod anatomical convention.