Head lice live for approximately 30 days and a female louse may lay between 50 – 150 eggs, we refer to these as nits!
The nits are an oval shape and are between 0.5 millimetres and 2 millimetres in length. When laid they are a yellow / white colour but can turn to a tan or coffee like colour as the embryo grows, once hatched the shell appears white.
Head lice can only survive on human blood, the lice feed from the scalp 3 to 4 times a day.
Image courtesy of headlice.org