What do lice like? - briefly
Lice are drawn to human blood and the warm, humid environment of the scalp. They also require close host contact to feed and reproduce.
What do lice like? - in detail
Lice are obligate ectoparasites that survive only on living hosts. Their survival depends on several specific conditions that satisfy nutritional, environmental, and reproductive needs.
Nutritional preference is limited to blood. Adult females ingest blood several times a day to produce eggs; nymphs require frequent feeding to complete development. Blood provides the proteins and iron essential for egg production and growth.
Environmental factors that support their life cycle include:
- Temperature: optimal range 29‑32 °C (84‑90 °F); cooler or hotter conditions reduce feeding activity and increase mortality.
- Humidity: relative humidity above 70 % prevents desiccation; low humidity leads to rapid dehydration and death.
- Darkness and shelter: dense hair or fur creates a protected microhabitat where lice can remain hidden from host grooming and environmental exposure.
Behavioral cues that attract lice involve chemical and tactile signals:
- Sebum and sweat contain fatty acids and volatile compounds that stimulate chemosensory receptors on the insect’s antennae.
- Carbon dioxide exhaled by the host serves as a general cue for locating a suitable feeding site.
- The close contact of hair shafts provides a physical substrate for oviposition; females cement eggs (nits) to the base of hairs near the scalp where temperature and humidity are stable.
Species‑specific variations exist. Human head lice (Pediculus humanus capitis) favor the scalp region with dense hair and high sebum production, whereas body lice (Pediculus humanus humanus) prefer clothing seams and skin folds where sweat accumulates. Animal lice, such as the sheep biting louse (Bovicola ovis), are attracted to species‑specific skin secretions and hair structures.
In summary, lice thrive on a combination of readily available blood, warm and humid microclimates, chemical cues from host secretions, and secure attachment sites for egg laying. Any deviation from these conditions markedly reduces their ability to feed, reproduce, and persist.