"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift

February 11, 2010

February 11 - Pediculus humanus humanus

In honor of "Fashion Week" in New York this week, six of the posts this coming week will involve parasites that relate to fashion in some way.

Today's: Body lice - I thought it would be fitting to start with these little creatures, which are a little "bonus" that we acquired when humans began to wear clothes.

Body lice, Pediculus humanus humanus (also called clothing lice) are believed to have evolved from head lice, likely invading the body region only recently with the advent of clothing use in modern humans. These wingless insects are found on the body and in clothing and prefer to attach their eggs to clothing rather than body hair. Compared to head lice, body lice are less prevalent parasites, associated mainly with those living in poor conditions in colder climates. Body lice are, however, potentially more harmful because they are known vectors of at least three bacterial pathogens in humans: Rickettsia prowazekii (epidemic or louse-borne typhus), Borrelia recurrentis (louse-borne relapsing fever) and Bartonella quintana (trench fever). Body lice, and the diseases they carry, can be transmitted fairly easily and quickly, especially in crowded situations such as war. In fact, body lice are known to have been prevalent amongst soldiers in Napoleon’s Grand Army and it’s possible that the diseases they carried may have played a role in the French retreat from Russia.

Contributed by Jessica Light.
Image from the CDC Public Health Image Library.


  1. What a lousy post! (Ha, ha, ha, ha, ha, ha, ha...!)
    - sorry, couldn't resist -

  2. Not to nit-pick, but since neither of the two subspecies is monophyletic (and even Jessi has gone over this with a fine toothed comb), can't we accept that the distinction is a lousy taxonomic mistake?

  3. I love the tie-in with fashion week. Will have to retweet for my beauty blogging fans.

  4. Ha! Well written Siddall! The two louse subspecies definitely have their preferred ecological niches and body lice are able to transmit some pretty nasty pathogens to humans. Some head lice have been shown to harbor the pathogens, but it's unclear/unknown if the lice were actually "head" lice (vs body lice found in the head region) and if head lice can actually transmit the pathogens. Recognizing head and body lice as distinct species/subspecies at this point it definitely questionable, but these forms may be on separate evolutionary tracks. Only time will tell!