How much does a louse weigh? - briefly
A single head louse typically weighs about 0.5 mg (0.0005 g). This corresponds to roughly five‑ten thousandths of a gram per insect.
How much does a louse weigh? - in detail
The adult human head louse (Pediculus humanus capitis) typically has a mass of about 0.5 mg, equivalent to 5 × 10⁻⁴ g. Measurements using analytical microbalances place the weight between 0.4 mg and 0.6 mg for fully fed individuals. Body lice (Pediculus humanus humanus) are slightly larger, averaging 0.7 mg, while crab lice (Pthirus pubis) weigh roughly 0.6 mg. Nymphal stages range from 0.1 mg in early instars to 0.4 mg in later stages.
Key points for accurate determination:
- Use a calibrated microbalance with a resolution of 0.01 mg.
- Record weight immediately after removal to avoid post‑mortem dehydration.
- Separate specimens by developmental stage and feeding status; a fed adult can weigh up to 20 % more than a starved one.
Conversions for reference:
- 0.5 mg ≈ 0.000018 oz (avoirdupois).
- 0.5 mg ≈ 0.0000011 lb.
Aggregated masses illustrate scale: a collection of 1 000 adult head lice would total roughly 0.5 g, comparable to the weight of a single grain of rice. Variability among populations reflects differences in host blood availability, ambient temperature, and genetic factors.