How many leg pairs do lice have? - briefly
Lice possess three pairs of legs, giving them a total of six legs. This trait is typical of all members of the order Phthiraptera.
How many leg pairs do lice have? - in detail
Lice belong to the order Phthiraptera, an assemblage of obligate ectoparasites that includes both sucking and chewing forms. Every adult specimen possesses three pairs of legs, totaling six limbs. This configuration is consistent across all species, whether the parasite infests humans, birds, or mammals.
The three leg pairs are structurally identical on each side of the body. Each leg comprises the following segments:
- Coxa – attaches the leg to the thorax.
- Trochanter – a short joint linking coxa and femur.
- Femur – the longest segment, providing leverage.
- Tibia – a slender section ending in the tarsus.
- Tarsus – subdivided into multiple tarsomeres, concluding with pretarsal claws.
The pretarsal claws are curved and enable the insect to grasp hair shafts or feathers securely. Nymphal stages retain the same six‑leg arrangement; no additional limbs appear during development, and the number does not change during molting.
Comparatively, six legs constitute the standard for all insects, distinguishing them from arachnids, which bear four pairs. Lice therefore conform to the typical insectary body plan, with their leg morphology specialized for a parasitic lifestyle.