How do lice move on the head? - briefly
Lice navigate the scalp by walking with six clawed legs that grip individual hair shafts, enabling rapid forward and backward progression. Their movement is also assisted by the host’s hair sway, which can transport them short distances without active locomotion.
How do lice move on the head? - in detail
Lice travel across the scalp by employing a combination of anatomical adaptations and behavioral strategies. Their six legs end in claws that lock onto individual hair shafts, allowing secure anchorage while the insect advances. Movement proceeds through a series of rapid, alternating leg motions that generate a crawling gait; each step lifts a pair of legs, propels the body forward a few millimeters, and then places the lifted legs onto the next segment of hair.
The body’s ventral side remains in contact with the hair, providing stability. Muscular contractions within the thorax coordinate leg movements, while sensory receptors on the legs detect hair diameter and surface texture, guiding the insect toward optimal grip. Lice can traverse hair lengths ranging from 1 mm to over 30 mm without detaching, because the claws adjust to varying shaft thicknesses.
When the host’s hair is dense, lice often follow the natural direction of hair growth, moving from the scalp outward toward the crown or vice versa, depending on the availability of food and favorable microclimate. In sparse regions, the insect may climb the hair shaft, pause to feed, and then resume crawling.
Key mechanisms of locomotion include:
- Claw‑to‑shaft attachment: curved claws fit around the hair cuticle, preventing slippage.
- Coordinated leg rhythm: alternating tripod gait ensures continuous contact with the substrate.
- Sensory feedback: mechanoreceptors sense changes in hair angle and tension, prompting directional adjustments.
- Body flexibility: a slender, dorsoventrally flattened body reduces resistance and allows navigation through tight hair bundles.
Temperature and humidity influence movement speed; higher temperatures increase metabolic rate, resulting in faster crawling, while optimal humidity maintains cuticular elasticity, preserving claw grip. Lice can remain motionless for extended periods, conserving energy until favorable conditions arise, then resume active locomotion to locate blood meals or suitable oviposition sites.