The eggs, laid on the hairs, and known as "nits," hatch in about eight days, and the lice are full grown in about a month.
The pair sat for hours in Knowsley Safari Park, picking nits out of each other's hair.
They lay eggs, called nits, which they stick to the shafts of your hair with a very strong glue.
You can work out when the lice first moved in by judging how many centimeters from the scalp you find the nits.
Which is not to say that I don't have some nits to pick.