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How do body heat and light affect where lice move on a host?
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louse
Human head louse (Pediculus humanus).
Lice are highly adapted to maintain close contact with their hosts, and their movement is significantly influenced by environmental cues. Specifically, lice are attracted to body heat and are repelled by light.1
These behavioral responses serve as a survival mechanism, causing the insects to remain within the warmth and darkness provided by the host’s plumage or pelage. By staying in these protected areas, lice are able to maintain the close proximity to the host necessary for their survival, as they are unable to live away from the host for more than short periods.1