Lice Life Cycle: Introduction to Lice, Stages in the Lice Life Cycle, the Egg

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Introduction to Lice

  • Louse (plural: lice) is the common name for members of the order Phthiraptera.

  • Lice were ubiquitous in human society until at least the middle ages.

  • They contain 5,000 species of wingless insect.

  • They are obligate parasites living externally on warm-blooded hosts.

  • This includes every species of bird and mammal, except for monotremes, pangolins, and bats.

  • They are vectors of diseases such as typhus.

Head Louse

Head Louse

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Life Cycle Stages

Life Cycle Stages

Life Cycle Stages

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Stage 1

The Egg

  • The eggs are tiny particles and known as nits.

  • The egg can measure up to 0.8 mm, oval-shaped and yellow or white colored.

  • It takes around one week at least for the egg to hatch into nymphs.

Stage 2

The Nymph

  • Lice undergo three stages of moulting.

  • These are the tiny versions of lice.

  • It is yellow to white colored.

Stage 3

The Adult

  • The adult lice measure up to 2 mm in length.

  • The life span of adult lice is 30 days that too if it is fed frequent blood meals on a regular basis.

Evolution

Anoplura

  • Sucking lice

  • Occurring on mammals exclusively.

Rhynchophthirina

Parasites of elephants and warthogs.

Ischnocera

  • Mostly avian chewing lice.

  • One family parasitizes mammals.

Amblycera

  • A primitive suborder of chewing lice.

  • Widespread on birds.

  • They live on South American and Australian mammals as well.

Other Important Points

  • Humans host two species of louse namely the head louse and the body louse.

  • The body louse has the smallest genome of any known insect.

Chewing lice:

  • Live among the hairs or feathers of their host.

  • Feed on skin and debris.

Sucking lice:

  • Pierce the host’s skin.

  • Feed on blood and other secretions.

They usually spend their whole life on a single host.

Colour of the Lice:

  • Usually cryptically colored.

    • To match the fur or feathers of the host.

    • Colour varies from pale beige to dark grey.