head lice off a human head A head louse, as opposed to a body louse, would never knowingly choose to leave a human scalp to travel to an inanimate object, as that would mean death. If head lice could “fall” off of a human scalp, the species would never survive. Here are the adaptations which prevent head lice from falling.
Head lice off a human head. Human head lice differ from body lice, which live off the human body (laying their eggs in the seams of clothing and return to the human host to feed several times per day). Body lice, despite their outward physical similarities to head lice, are adapted to navigate off their human host onto inanimate objects.
Head lice, on the other hand, do not exhibit this capability. Try placing a human head louse on a shirt or sweater and see how it struggles to navigate this foreign environment. In the photographs of a head louse leg and claw I took through our microscope last week in the NitWits office, note the highly adapted and specialized claw at the distal end of the head louse leg. This claw is designed to firmly/hydraulically clamp onto the human hair shaft when the hair is disturbed, (brushing hair, showering, changing shirts, etc) and for rapidly traveling through human hair. This claw is not designed for walking from clothing, couches, stuffed animals, bedding, etc. back to the human host. In addition, without hind legs human head lice do not have the ability to jump, as some other arthropods do. Therefore, if somehow a human head louse finds itself off of a human scalp, that is the end of that louse’s life. Lice know that moving away from their human host would be fatal, so they do everything in their power to stay on the human scalp at all times.