The lifecycle of Pediculus humanus can be quite rapid and exhibit only sexual reproduction.  This lifecycle contains three stages: nit, nymph, and adult.  For a single louse, the lifecycle usually lasts 30 days.

Stage 1- Eggs (also known as nits): The adult females lay these nits, which are then attached to the hair shaft by a gluey substance produced by the louse.  Nits range in color white to yellow, and tan to gray, depending on the stage of the development and whether or not they have been killed by a treatment or are hatched.  These eggs also obtain an oval or teardrop shape. 

Stage 2 - Nymphs (immature louse): The nits are usually found to incubate (sit upon for the purpose of hatching) for seven to 14 days.  Then, they hatch to release the nymph.  The nymph continues to grow and mature for the next seven to ten days.  Throughout this period, the nymph goes through three molts until it becomes an adult louse.

Stage 3 - Adults: The adult louse has the lifespan of about 30 days and it the size of a sesame seed.  The adult louse needs to feed on human blood every three to six hours, and can not survive away from the human host for more than approximately 24-36 hours.  The female is generally larger than the male and can lay five nits per day.  This means about 150 nits throughout their lifespan!

As these insects reproduce, the ideal temperature is about room temperature, give or take a couple degrees.  They are unable to reproduce in hot temperatures.  This is why many people suffering from head lice pour hot water on their head and body.  Lice are found to be repelled by the heat.

Good thing these critters only live for about 30 days. Let's learn about the adaptations and interactions that lice are associated with...