This week’s podcast is guaranteed to make your scalp crawl—but don’t worry, it’s most likely all in your head, and not on it. We’ll visit entomologist Richard Pollack to learn about an insect that’s the bane of parents and school principals everywhere—or is it? Ari Daniel Shapiro explains. Photo Credit: Gilles San Martin, CC BY-SA Download a transcript of this podcastread moreDuration: 5:04Published: Wed, 08 Aug 2012 13:52:49 +0000
Centers for Disease Control/Division of Parasitic Diseases and Malaria
EOL staff
Life cycle of the Head Louse (Pediculus humanus capitis), an ectparasite of humansThe life cycle of the Head Louse (Pediculis humanus capitis) has three stages: egg, nymph, and adult. Eggs: Nits are Head Lice eggs. They are hard to see and are often mistaken for dandruff or hair spray droplets. Nits are laid by the adult female and are cemented at the base of the hair shaft nearest the scalp (1). They are 0.8 mm by 0.3 mm, oval and usually yellow to white. Nits take about 1 week to hatch (range 6 to 9 days). Viable eggs are usually located within 6 mm of the scalp. Nymphs: The egg hatches to release a nymph (2). The nit shell then becomes a more visible dull yellow and remains attached to the hair shaft. The nymph looks like an adult head louse, but is about the size of a pinhead. Nymphs mature after three molts (3, 4) and become adults about 7 days after hatching. Adults: The adult louse is about the size of a sesame seed, has 6 legs (each with claws), and is tan to grayish-white (5). In persons with dark hair, the adult louse will appear darker. Females are usually larger than males and can lay up to 8 nits per day. Adult lice can live up to 30 days on a person’s head. To survive , adult lice need to feed on blood several times daily. Without blood meals, the louse will die within 1 to 2 days off the host.From Centers for Disease Control Parasites and Health website.
Centers for Disease Control/Division of Parasitic Diseases and Malaria
EOL staff
Life cycle of the Pubic (or Crab) Louse (Pthirus pubis), an ectoparasite of humansPubic lice (Pthirus pubis) have three stages: egg, nymph and adult. Eggs (nits) are laid on a hair shaft (1). Females will lay approximately 30 eggs during their 3-4 week life span. Eggs hatch after about a week and become nymphs, which look like smaller versions of the adults. The nymphs undergo three molts (2, 3, 4) before becoming adults (5). Adults are 1.5-2.0 mm long and flattened. They are much broader in comparison to head and body lice. Adults are found only on the human host and require human blood to survive. If adults are forced off the host, they will die within 24-48 hours without a blood feeding. Pubic lice are transmitted from person to person most commonly via sexual contact, although fomites (bedding, clothing) may play a minor role in their transmission.From Centers for Disease Control Parasites and Health website.
Figure 10.Drawing of hypandrium of Libanopsyllipsocus alexanderasnitsyni gen. et sp. n., holotype, male; par = paraproct, ep = epiproct, trich = trichobothria; scale bar = 0.3 mm.
