Phthiraptera - The Parasitic Lice
The Phthiraptera were once treated as two separate orders (Anolplura and Mallophaga) but are now recognized as one. The ordinal name Phthiraptera is derived from the Greek words "phthir" (lice) and "aptera" (wingless). Calling them “wingless lice” is appropriate, for no member of this order requires these appendages. Living on the skin of their many hosts, ranging from birds to humans, parasitic lice live very specialized existences. There are many, many different kinds of lice, the most well known (of course) being those that live on humans. The three species that live on humans have been able to divide the human body up amongst themselves; one species living in the hair on the head, one crawling about on the body and one living in the pubic region. Human body lice are actually closely related to human head lice; the two species diverged when humans began to wear clothing, therefore creating a new habitat niche! Lice can be divided into two groups: those that have mandibles and chew (Mallophaga) and those that have mouthparts designed to suck body fluids (Anolplura), the former probably giving rise to the latter. Anolplura is now considered a suborder within Phthiraptera. The old taxon Mallophaga is paraphyletic and now recognized as three suborders: Ischnocera, Amblycera and Rhyncophtherina. Unlike many other ectoparasites, the Phthiraptera cannot survive long if separated from the body of their host. Eggs (nits) are glued directly to hair or feathers and nymphs hatch and feed on the parental host. Since lice have no wings, dispersal to new host animals is limited solely to occasions when members of the host species come into direct contact. A close association with its food supply means that most lice are limited to a very narrow host range - often only a single species. Through speciation, there are now about 3,000 species of parasitic lice. Parasitic lice appear to be a recent phenomenon, geologically speaking. Until quite recently, the oldest specimens known were removed from the hair of 10,000-year-old wooly mammoths frozen in Siberian permafrost. An exceptionally preserved, 44 million year-old fossil louse was recently discovered in Germany. Remains of the louse’s last meal, feathers, can be seen preserved within its gut. The fossil louse is remarkably similar to feather-eating lice found on some modern-day aquatic birds. This fossil shows that birds have been infested with parasitic lice since at least the Eocene epoch, raising the possibility that lice were passed on to birds from early, feathered dinosaurs.