Head louse
The human head louse, scientifically known as *Pediculus humanus capitis*, is a small, wingless insect that primarily inhabits the hair on the scalp, where it feeds on human blood. This louse is typically one to three millimeters long and comes in colors ranging from white to brown. Its presence causes symptoms such as redness and itching due to its feeding process, which involves using a sharp proboscis to pierce the skin and inject a fluid that keeps the blood flowing.
Head lice are not known to transmit diseases, unlike their relative, the body louse, which can carry pathogens. Transmission of head lice commonly occurs through close contact, such as sharing hats or combs, as they are unable to jump or fly. Female lice can lay up to 150 eggs, known as nits, which adhere firmly to hair follicles. Treatments for head lice usually involve maintaining cleanliness and using specialized shampoos, creams, or powders. While head lice can be a nuisance, they are not considered a threat to public health and are found on every continent except Antarctica.
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Human head louse
Among the three lice which may infect a person is the head louse. This tiny insect makes its home only in the hair on top of a person's head and sucks blood. This action causes redness of skin and itching. A close relative, the body louse, lives elsewhere on the body. The head louse lives on every continent except Antarctica.
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Psocodea
Family: Pediculidae
Genus: Pediculus
Species: Humanus Capitis
The head louse is a common and familiar insect to people around the world. This tiny insect lives amid the hairs on top of a person's head and sucks blood. It does not have wings to fly, and its short legs are not strong enough for jumping, and so it likely lives its entire life on one person except in a few situations. It may leave its home if the person dies, has a high fever, or the person comes in close contact with another person. Familiar examples of this are when children share hats and combs and transfer the louse's eggs. If it does not eat, the louse may die within 12 hours or after two or three days.
This louse is white, yellow, or brown. It has a long, slender, oval body with bumpy edges and is one to three millimeters long. Its head has one pair of short antennae, which are important for sensing its surroundings. Six short, stout legs extend from its thorax, the mid-body section just behind the head. Many short sensory hairs cover its legs and segmented body and take the place of its poor eyesight or blindness. A claw on each leg anchors the louse while it feeds and prevents it from being torn from its hairy home.
From the louse's head extends a proboscis, or snout, which is sharp and pointed for piercing skin. When it feeds, the louse grabs hold of hairs with its claws, stands on its head, and drives its proboscis into its victim. A fluid which the louse secretes keeps the person's blood flowing freely while the louse sucks. This fluid also causes the skin to become red and to itch.
When a person is infected with this louse it is called pediculosis. Water alone is not usually enough to remove the louse since it can hold on tightly and survive underwater for one to two days. Treatment for head louse includes basic hygiene, or cleanliness, and special soaps, shampoos, creams, and powders.
Over multiple days, the female louse attaches up to 150 eggs to hairs on the head. She uses a special fast-drying cement to hold the eggs in place. The nits, or eggs, have very hard shells which withstand pressure and being crushed. The young hatch eight days after being laid. The young lice make small holes in the tops of their shells. They then breathe in air and release it through their anuses, or rear ends, into the shells beneath their bodies. This builds air pressure in the shells which propel the young from the shells. After eight more days, during which they molt, or shed their skins, the young become adults. From the time they hatch, the young live around one month.
This species of louse is not to be confused with its close relatives, the body louse (Pediculus humanus) and the crab louse (Phthius pubis). These two species live on every part of the human body except in the hair on top of the head. The crab louse receives its name for its crab-shaped body, which is about one millimeter long. Although the body louse may carry diseases, the other two species do not carry any known diseases. The head louse is not a threatened species.
Bibliography
“Head Lice - Symptoms & Causes.” Mayo Clinic, 2024, www.mayoclinic.org/diseases-conditions/head-lice/symptoms-causes/syc-20356180. Accessed 12 Apr. 2024.
Hunter, Garry. “Head Louse.” National Geographic Kids, 2024, kids.nationalgeographic.com/animals/invertebrates/facts/head-louse. Accessed 12 Apr. 2024.