Invertebrate Zoology: A Study Guide - T. A. Dauda 2014

Metazoa
Arthropods
Subphylum Tracheata - Class Insecta - Orders with Incomplete Metamorphosis - Order Anoplura

There are about 300 known species of lice—Blood-sucking insects equipped with a piercing-sucking mouthpart shaped like a retractable proboscis. They are permanent parasites of mammals and humans.

The thoracic segments of lice are fused, and their eyes are either very tiny or entirely absent. Each two-jointed tarsus terminates in a powerful, well-developed claw that can fold back against the preceding segment, enabling the louse to grip tightly to Hair or cling to fabric fibers.

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Fig. 67 Body louse (1) and hog louse (2)

Three species of lice are known to parasitize humans: the HEAD louse (Fig. 67), the body louse, and the pubic louse, or crab louse. Lice lay relatively few eggs: the head louse produces 3–4 eggs per day, while the body louse lays 6–14. Over its lifetime, a head louse lays about 140 eggs, and a body louse no more than 300. Enclosed in a protective shell, louse eggs are called nits. Nits are securely cemented to human hair or the threads of clothing.

The maximum lifespan of a female body louse is approximately 46 days. Their development involves incomplete metamorphosis and takes several days, depending on environmental temperatures.

Pediculosis causes intense, distressing itching and Skin conditions triggered by the parasites' bites. Furthermore, lice pose a severe threat as vectors of epidemic typhus and relapsing fever.

The primary defenses against pediculosis are personal hygiene, sanitary awareness, and cleanliness. Consequently, lice are far less common in highly developed, civilized nations than among underprivileged and backward populations. Various societal disasters (such as wars or mass Migrations), which force large groups of people to crowd together in squalor without the means to maintain bodily and clothing hygiene, are invariably accompanied by a surge in pediculosis. Lice are highly host-specific parasites, with distinct species infesting specific hosts (e.g., hog lice, dog lice, cattle lice, etc.).