How did lice bite? - briefly
Lice pierce the skin with their sharp mandibles, creating a tiny wound that allows them to draw blood. Their saliva contains anticoagulants that keep the blood flowing while they feed.
How did lice bite? - in detail
Lice are obligate ectoparasites that obtain nutrients by piercing the host’s skin and consuming blood. Their mouthparts consist of a pair of slender, sclerotized maxillae and a mandible modified into a stylet. The stylet forms a narrow, needle‑like tube approximately 0.2 mm in length, capable of penetrating the epidermis and reaching superficial capillaries.
When a louse initiates feeding, it anchors its forelegs to the host’s hair or clothing, then extends the stylet toward the skin surface. Muscular contractions drive the stylet forward, creating a micro‑incision that bypasses the stratum corneum. Saliva is injected simultaneously; it contains anticoagulants (e.g., apyrase) and anesthetic proteins that prevent clotting and reduce the host’s sensation of the puncture.
The louse then draws blood through the stylet by creating negative pressure with its cibarial pump, a muscular chamber located in the head. Blood flow is continuous until the insect’s abdomen expands to its capacity, typically 0.5–1 µL per feeding bout. After engorgement, the louse retracts the stylet, releases the saliva, and may move to another site.
Key physiological steps:
- Penetration: Stylet pierces epidermis and reaches capillary.
- Saliva delivery: Anticoagulants and anesthetics are secreted.
- Blood uptake: Negative pressure generated by cibarial pump draws blood.
- Termination: Abdomen fills, stylet withdraws, feeding ends.
The bite often appears as a small, red papule that may develop a wheal or secondary irritation due to the host’s immune response to the salivary proteins. Repeated feeding can lead to localized inflammation, itching, and, in severe cases, secondary bacterial infection.