Who is larger: a flea or a louse? - briefly
Fleas measure roughly 1.5–3 mm and are bulkier, while head lice are about 2–3 mm long and slimmer. Therefore, fleas are larger overall.
Who is larger: a flea or a louse? - in detail
Fleas are wingless, laterally compressed insects that typically measure between 1.5 mm and 4 mm in length, depending on species. The common cat flea (Ctenocephalides felis) averages about 2.5 mm, while the human flea (Pulex irritans) can reach up to 4 mm. Body width ranges from 0.5 mm to 0.7 mm.
Lice are obligate ectoparasites with a more elongated, dorsoventrally flattened body. Adult head lice (Pediculus humanus capitis) are 2.5 mm to 3 mm long and 0.8 mm wide; body lice (Pediculus humanus corporis) are slightly larger, reaching 3.5 mm in length. Pubic lice (Pthirus pubis) are the smallest, measuring 1.2 mm to 1.8 mm.
Comparing the maximum dimensions, fleas exceed lice in length, especially the larger species that approach 4 mm. Width measurements also favor fleas, whose bodies are generally broader than those of most lice.
Size variation depends on several factors:
- Species: different flea and louse species have distinct size ranges.
- Developmental stage: nymphs are smaller than adults.
- Host environment: nutrient availability from the host can affect growth.
- Sex: in some species, females are larger than males.
Overall, the insect with the greater overall dimensions is the flea, whose maximum length and width surpass those of any louse species.