How do lice live on a person? - briefly
Lice reside in the hair or eyelashes, feeding on tiny blood meals multiple times daily and depositing eggs (nits) that cement to the hair shaft near the skin. They persist by remaining on the host, relying on the body’s warmth, moisture, and continuous blood supply.
How do lice live on a person? - in detail
Lice are obligate ectoparasites that complete their entire life cycle on a human host. Adult females lay 6‑10 eggs (nits) per day, attaching them with a cement‑like secretion to the base of hair shafts or eyelashes. The eggs hatch after 7‑10 days, releasing nymphs that resemble miniature adults. Nymphs undergo three molts over 9‑12 days before reaching reproductive maturity.
Feeding occurs exclusively on blood. Mouthparts are adapted for piercing the epidermis and drawing plasma, which provides the nutrients required for growth and egg production. A single blood meal may last several minutes, after which the louse returns to its resting site.
Preferred habitats differ among species:
- Head lice (Pediculus humanus capitis) remain on the scalp, congregating near the nape, behind the ears, and along hair shafts where temperature and humidity are optimal.
- Body lice (Pediculus humanus corporis) inhabit clothing seams, moving to the skin only to feed, and lay eggs on fabric fibers.
- Pubic lice (Pthirus pubis) occupy coarse hair in the genital region, attaching eggs close to the skin surface.
Environmental conditions on the host are tightly regulated. Lice thrive at temperatures of 30‑35 °C and relative humidity of 70‑90 %. Deviations outside this range reduce activity and survival; prolonged exposure to temperatures below 20 °C or humidity under 50 % can be lethal.
Reproduction is rapid. Under optimal conditions, a female can produce 150‑200 eggs during her 30‑day lifespan, leading to exponential population growth if unchecked. The life cycle’s short duration enables a new generation to appear within two weeks of initial infestation.
Mobility is limited to crawling. Lice lack wings and cannot jump, relying on direct contact between hosts for transmission. Transfer occurs through head-to-head contact, shared clothing, or bedding, allowing the parasite to locate a new environment that meets its thermal and humid requirements.
In summary, lice depend on a human body for shelter, nutrition, and reproduction. Their life stages, feeding behavior, habitat preferences, and environmental tolerances combine to create a self‑sustaining population that persists as long as suitable conditions remain.