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Lousology 101

Images & Biology of Head Lice

  • Nits (the eggs of the head louse) are small yellowish-white, oval-shaped eggs that are "to the side of a hair shaft glued" at an angle
  • Nits must be laid by live lice. You cannot "catch nits."
  • Once laid, it takes 7-10 days for a nit to hatch, and another 7-10 days for the female to mature and begin laying her own eggs.
  • Head lice are clear in color when hatched, then quickly develop a reddish-brown color after feeding.
  • Head lice are about the size of sesame seeds.
  • Head lice have six legs equipped with claws to grasp the hair.
  • Head lice are crawling insects. They cannot hop, jump, or fly.
  • Head lice do not thrive on pets.
  • Head lice are small, wingless insects which feed on human blood. They need human blood in order to survive.
  • Head lice live for approximately 30 days on a host and a female louse may lay up to 100 nits (eggs).
  • Head lice off of their human hosts will starve. The NPA suggests that, in most cases, a head louse will not survive for more than 24 hours off of its human host.

More About Lice from

The Louse - An Account of the Lice Which Infest Man, Their Medical Importance and Control
By Patrick A. Buxton, C.M.G., F.R.S. (technical but informative for those doing research)


 click the images below to get a closer look

Lice of different sizes


Head louse

Adult female & adult male

Nymph (newborn louse)

& adult louse

Tarsal claw of the head louse

Nits compared in size to

the head of a pin

Louse egg (nit)

Louse hatching from egg

Nit casings on a hairshaft
  Images below appear courtesy of Iowa State University

Pediculus humanus claw

Dorsal and ventral views

of Pediculus humanus

Dorsal and lateral views

of Pediculus humanus

Whole body view

of Pediculus humanus

Human head louse close-up

Lateral view of
Pediculus humanus

Two head lice with dime

for size comparison

Ventral view of

Pediculus humanus

Next 3 images below appear with permission from Dr. Gaetano Scanni
"Feces of Pediculus capitis humanus as sign of viability of the louse." Eur. J. Ped. Dermatol. 17, 77-80, 2007.


Pediculus & Feces (Faeces)

Dr. Gaetano Scanni

Pediculus & Feces (Faeces)

Dr. Gaetano Scanni

Pediculus & Feces (Faeces)

Dr. Gaetano Scanni

Images below appear courtesy of Rick Speare

human head louse

nit attached to hairshaft

Images below appear courtesy of William B. Swain

Images below appear courtesy of Dr. Gaetano Scanni

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The National Pediculosis Association,® Inc.
A Non-Profit Organization
Serving The Public Since 1983.

2019 marks 36 years of Service.

The NPA is a 501(c)(3) tax-exempt non-profit volunteer organization, including scientific advisors, dedicated since 1983 to protecting children and their environment from the misuse and abuse of prescription and over-the-counter pesticide treatments for lice and scabies.
The LiceMeister comb® was developed by the NPA in 1997 to provide a higher standard for lice combing tools and a safe, cost-effective treatment alternative to pesticides. Proceeds from sales of the LiceMeister comb allow the NPA to be self-sustaining while accomplishing its mission.

©1997-2019 The National Pediculosis Association®, Inc.
All images ©1997-2019 The National Pediculosis Association®, Inc.

The LiceMeister Comb for liceremoval