There are three stages that complete the life cycle of Head Lice; they are the nit, nymph and the adult. 

Nit:  Nits are the eggs of the Lice. They are attached with glue like substance on the hair shaft close to the scalp.Nits are equipped with ventilation slit at the top of the egg to provide air.  These nits are small oval cylinders approximately 1/16th of an inch in length. They can be a variety of colors ranging from a light, whitish color to a dark brown. Once hatched, it becomes transparent. It usually takes 7-10 days for the larva to mature and hatch.  Nits can survive 4-10 days off of a human host.

Nymph: Upon hatching the baby Louse is considered a nymph.  The nymph looks similar to an adult Head Louse but smaller. After hatching, the Louse needs a blood meal within 45 minutes in order to survive. A young Louse will molt three times before it reaches sexual maturity. This process takes 7-12 days.

Adult:  The adult Louse is approximately 2 millimeters long, with six legs that are designed to cling to hair shafts. The Head Louse and Body Louse almost identical; however, the Head Louse is smaller in comparison. Head Lice are dependant upon a daily blood meal for survival.  The adult Head Louse is bluish-gray to whitish or brown in color. They are round to oval in shape and are longer than they are wide.