How quickly do lice run? - briefly
«Lice crawl at roughly 0.2 cm s⁻¹, about one meter per hour». This speed limits rapid movement across a host, so transmission depends on direct contact.
How quickly do lice run? - in detail
Lice are obligate ectoparasites that move primarily by crawling rather than flying. Their locomotion speed has been measured in laboratory settings using high‑speed video analysis on transparent substrates.
Typical velocity ranges from 0.02 m s⁻¹ to 0.05 m s⁻¹ (approximately 1–3 cm s⁻¹). This corresponds to about 0.07–0.15 km h⁻¹, far slower than most insects that can run or fly at several meters per second.
Key factors influencing movement speed include:
- Species: head lice (Pediculus humanus capitis) exhibit slightly faster crawling than body lice (Pediculus humanus humanus) due to differences in leg morphology.
- Temperature: ambient temperatures above 30 °C increase metabolic activity, raising speed by up to 20 %.
- Substrate texture: smooth surfaces such as hair shafts allow more rapid progression than coarse fabrics.
- Life stage: nymphs move slower than mature adults because of smaller muscle development.
Experimental observations show that lice can traverse the length of an average human scalp (≈20 cm) in roughly 30–60 seconds under optimal conditions. Their movement is characterized by a “tripod” gait, with alternating bouts of leg extension and retraction that generate a maximum stride length of 0.5 mm per cycle.
Comparative data place lice among the slowest terrestrial arthropods. For reference, houseflies can achieve speeds up to 5 m s⁻¹, while ants may reach 0.1 m s⁻¹. The limited speed of lice reflects their adaptation to a stable host environment where rapid escape is unnecessary.
Overall, lice locomotion is constrained to a few centimeters per second, with variations driven by species, temperature, surface characteristics, and developmental stage.