What does a flea look like and what does a louse look like? - briefly
A flea is a wing‑less insect 1–3 mm long, laterally flattened, dark reddish‑brown, with powerful hind legs for jumping and a short, stout head. A louse is a wing‑less parasite 2–4 mm long, dorsoventrally flattened, pale gray‑white, with clawed legs adapted to cling to hair or feathers.
What does a flea look like and what does a louse look like? - in detail
Fleas are small, laterally compressed insects measuring 1.5–3.5 mm in length. Their bodies are deep‑brown to reddish‑black, covered with tiny spines that give a rough texture. The head is short, bearing a pair of long, slender antennae that fold backward beneath the eyes. Large, powerful hind legs end in a row of tiny spines, enabling the animal to jump many times its body length. Six legs are present in total, each equipped with comb‑like claws for gripping the host’s hair. The abdomen is segmented, visibly expanding after a blood meal, and the wings are absent, a defining trait of the order Siphonaptera.
Lice are wingless, obligate ectoparasites ranging from 1 to 4 mm, depending on species. Their bodies are dorsoventrally flattened, facilitating movement through hair or clothing fibers. Color varies from grayish‑white in nymphs to brown or dark brown in adults. The head is relatively large, with compound eyes positioned laterally, and a pair of short antennae concealed under a shield‑like labrum. Six legs terminate in sharp claws that cling tightly to individual hairs or fibers. The thorax bears a prominent pronotum, often bearing a distinct pattern of bristles. Abdomen segmentation is visible, with a smooth, often shiny surface. In human head lice, the body appears more elongated, while body lice display a broader, more robust form.
Key visual differences:
- Shape: flea – laterally compressed; louse – dorsoventrally flattened.
- Jumping ability: flea – powerful hind legs for leaping; louse – legs adapted for crawling only.
- Antennae: flea – long, visible; louse – short, hidden.
- Body surface: flea – spiny, rough; louse – smooth, sometimes glossy.
- Size range: overlapping, but flea generally larger in the upper range.
These morphological traits enable each parasite to exploit its specific ecological niche and host‑attachment strategy.