The Life Cycle Of Head Lice
(Pediculus Humanus Capitis)

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The Life Cycle of head lice is approximately 35-40 days. Which is a great deal of time for them to create, several communities, all, at various stages of the cycle.

As always, it takes two, to tango. Within 24 hours of mating the female lays her eggs, and the start of another cycle is under way.


The Eggs

  • The eggs are white or brown in color and laid on strands of hair close to the scalp.
  • Warmth from their human host's head will aid in the incubation process.
  • Once laid, the egg will incubate for
    approximately 7 days. After which time, it
    will hatch and begin it's new life as a "Nymph"

Nymphal Stage 1. (9 days old)

  • As the nymph grows, it sheds it's skin every three days. This is the first moult, two days after hatching
  • Five days after hatching, it will shed it's skin for a second time. This is the 2nd moult.

Nymphal Stage 3. (15 days old)

  • Eight days after hatching, the third and final time the skin is shed. This is the 3rd moult.

The visible change between each Nymphal Stage, is the length of the abdomen, which increases each time it's skin is shed.


15-16 Days

At this stage, the nymph's have reached maturity and are now adults. Mating can occur approx 10 hours after final moult with each attachment lasting at least one hour.


16-18 Days

  • 1-2 days after mating the female lays her first eggs.
  • Laying up to 4-6 eggs a day during her life-time, but fewer eggs will be laid as she gets older.

18-34 Days

  • For the next 16 days the female will continue to feed, mate and lay more eggs each day.


35-40 Days

After starting it's life as an egg, the demise of the head louse is inevitable, as it's life cycle finally comes to an end.

Consider this

  • One female, laying one egg
  • 7 days later, egg hatches, now called a nymph
  • 3 days later, nymph sheds it's skin for the first time. Nymph's age is now approx 9 days old.
  • 3 days later, nymph sheds it's skin for the second time. Nymph's age is now 12 days old
  • 3 days later, nymph sheds it's skin for the third and last time. Nymph's age is now 15 days old. At this stage of it's life, it is now a mature and sexually active adult. Mating can occur 10 hours after reaching maturity, during which time they will mate frequently, several times each day.
  • Between 16-18 days old, the female will lay the first of her eggs.
  • 18-34 days old the female will continue to fornicate and lay approx 4-6 eggs each day
  • 35-40 days old. Since beginning life as an egg, the head louse eventually dies.

This analysis is based on one head louse, laying one egg, and progressing through the life cycle. Multiply that by 10 head louse or even more, each laying 4-6 eggs at one time, and progressing through to the end of it's cycle! Scary Stuff, isn't it?

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