What do a flea and a louse look like? - briefly
A flea is a tiny, laterally flattened, wingless insect about 1–4 mm long, with a hard dark exoskeleton and strong hind legs for jumping. A louse is a similarly sized, elongated, wingless parasite, 1–3 mm long, with a softer pale body and clawed legs adapted for clinging to hair or feathers.
What do a flea and a louse look like? - in detail
Fleas are laterally compressed insects measuring 1.5–3.5 mm in length. Their bodies are dark brown to reddish, covered with microscopic spines that aid in movement through host fur. The head is short, bearing large, compound eyes and long, serrated antennae. Mouthparts form a piercing‑sucking stylet capable of penetrating skin to ingest blood. Legs are long relative to body size, ending in tiny, hooked claws that grasp hair shafts. The abdomen expands after a blood meal, becoming visibly distended.
Lice are obligate ectoparasites, typically 2–4 mm long for body lice and 1–2 mm for head lice. They possess a dorsoventrally flattened, oval body, uniformly gray‑white to brown, lacking wings. The head bears a pair of small, compound eyes and short antennae concealed in grooves. Mouthparts consist of a narrow stylet adapted for feeding on skin debris or blood, depending on species. Three pairs of legs end in clawed tarsi that cling tightly to hair or clothing fibers. The abdomen is segmented, with visible spiracles along the sides.
Key morphological distinctions:
- Body shape: flea – laterally flattened; louse – dorsoventrally flattened.
- Size range: flea slightly larger on average.
- Leg length: flea’s legs proportionally longer; louse’s legs short and stout.
- Claws: flea claws hook hair; louse claws grip hair or fabric.
- Coloration: flea darker, often reddish; louse lighter, gray‑white to brown.
Both insects lack wings and have specialized mouthparts for hematophagy, but their body plans reflect adaptation to different host environments—fleas to fur and rapid jumps, lice to close contact with hair or clothing.