Head Lice Size: Facts About Pediculus humanus capitis

Head lice (Pediculus humanus capitis) are small, wingless, blood-feeding insects.

Size

• Adults: 2.0–3.5 mm long (≈ sesame seed). Females slightly larger than males.
• Nymphs: 1–2 mm (pinhead), translucent until first blood meal.
• Nits (eggs): 0.8 mm × 0.3 mm, teardrop-shaped.

Key Features

• 6 legs with claws adapted for gripping hair shafts.
• Piercing mouthparts for blood feeding (4–5x/day).
• Color: Grayish-white to reddish-brown (after feeding).
• No wings, no jumping ability – crawl rapidly.

Not "Bugs" in the Colloquial Sense

"Bug" technically refers to Hemiptera (true bugs). Lice are Phthiraptera (order). But "head lice bugs" is common parlance.

Detection

Best found by wet combing with fine-tooth metal comb on conditioned hair. Nits glued near scalp are more visible than mobile adults.