Lice, the parasitic insects eternally need a host to clutch the nourishment from it. Lice share a parasitic relationship with their hosts, which are humans for the utmost time, especially for the head lice. Humans are regarded as their hosts because; lice suck blood from their scalp for their nourishment and fulfill their living requirements. Hence, it is quite inevitable that they cannot survive without a proper host.
According to a survey, it has been proven that a mature louse couldn’t survive more than 24 hours if it is separated from a host. Though, head lice could spread in the eyelashes or eyebrows too, besides hair shaft, so they could feed without a scalp but, they cannot live completely without a host, and that’s for sure! Though mature lice could live in nonhuman surfaces like floors, clothing, furniture, hat, helmet, hair accessories, etc. for a few hours, but they will die naturally, if it couldn’t find proper blood resources soon.
On the other hand, nits can’t survive more than a few minutes, if they get separated from the human scalp; because the warmth of human scalp is necessary for their incubation before hatching.