page_title: Arthropod leg
section_title: Fundamental morphology of insect legs
hierarchical_section_title: Arthropod leg / Insects / Fundamental morphology of insect legs
caption_attribution_description: English: The ancestral form of the insect leg, showing the five named parts. Evolution has eliminated parts or greatly modified parts in some insects.
context_page_description: The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa, trochanter, femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus, patella.
  Homologies of leg segments between groups are difficult to prove and are the source of much argument. Some authors posit up to eleven segments per leg for the most recent common ancestor of extant arthropods but modern arthropods have eight or fewer. It has been argued that the ancestral leg need not have been so complex, and that other events, such as successive loss of function of a Hox-gene, could result in parallel gains of leg segments.
  In arthropods, each of the leg segments articulates with the next segment in a hinge joint and may only bend in one plane. This means that a greater number of segments is required to achieve the same kinds of movements that are possible in vertebrate animals, which have rotational ball-and-socket joints at the base of the fore and hind limbs.
context_section_description: A representative insect leg, such as that of a housefly or cockroach, has the following parts, in sequence from most proximal to most distal:
  coxa
  trochanter
  femur
  tibia
  tarsus
  pretarsus.
  Associated with the leg itself there are various sclerites around its base. Their functions are articular and have to do with how the leg attaches to the main exoskeleton of the insect. Such sclerites differ considerably between unrelated insects.
caption: Diagram of a typical insect leg
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