What are lice and how do they live? - briefly
Lice are tiny wingless insects that survive by feeding on the blood or skin secretions of mammals and birds. Their life cycle occurs entirely on the host: females attach eggs to hair shafts, which hatch into nymphs that undergo several molts before reaching adulthood.
What are lice and how do they live? - in detail
Lice are obligate ectoparasites belonging to the order Phthiraptera, divided into two suborders: Anoplura (sucking lice) that feed on blood, and Mallophaga (chewing lice) that consume skin scales, hair, and secretions. All species are wingless insects, flattened laterally to navigate the host’s fur or feathers, and possess piercing‑sucking or mandible‑type mouthparts adapted to their diet.
Adult females lay 1–10 eggs (nits) per day, attaching them firmly to hair shafts or feathers with a cementing secretion. The egg stage lasts 6–10 days, depending on temperature and species. Upon hatching, the nymph undergoes three molts (first, second, and third instar), each lasting 2–5 days. The complete development from egg to reproductive adult typically requires 10–14 days under optimal conditions. Adult lice live 20–30 days on the host, during which they mate repeatedly; females can produce several hundred offspring over their lifespan.
Feeding behavior differs between the two suborders. Blood‑sucking lice insert their proboscis into the host’s skin, drawing blood and causing irritation, anemia, or disease transmission. Chewing lice scrape epidermal debris and sebaceous secretions, leading to itching and secondary infections. Both groups rely on close contact for transmission; direct physical interaction, shared bedding, or fomites facilitate spread among humans, livestock, or birds.
Environmental tolerance is limited. Lice cannot survive more than 24–48 hours off a living host because they lack functional respiratory spiracles for atmospheric oxygen and cannot regulate temperature or humidity. Consequently, control measures focus on eliminating the parasite from the host and its immediate surroundings. Effective strategies include:
- Mechanical removal of nits with fine-tooth combs.
- Application of approved pediculicides (e.g., permethrin, ivermectin) following label instructions.
- Washing clothing, bedding, and personal items at ≥60 °C or sealing them in airtight containers for two weeks.
- Regular inspection of high‑risk groups (schoolchildren, livestock herders) to detect infestations early.
Understanding the biology, reproductive cycle, and host dependence of lice is essential for developing targeted interventions and preventing reinfestation.