Head lice / louse
The head louse (Pediculus humanus capitis) is an obligate ectoparasite of humans that causes head lice infestation (pediculosis capitis).[1]
Head lice are wingless insects spending their entire lives on the human scalp and feeding exclusively on human blood.[1] Humans are the only known hosts of this specific parasite, while chimpanzees host a closely related species, Pediculus schaeffi. Other species of lice infest most orders of mammals and all orders of birds,[1] as well as other parts of the human body.
Lice differ from other hematophagic ectoparasites such as fleas in spending their entire lifecycle on a host.[2] Head lice cannot fly, and their short, stumpy legs render them incapable of jumping, or even walking efficiently on flat surfaces.[2]
The non-disease-carrying head louse differs from the related disease-carrying body louse (Pediculus humanus humanus) in preferring to attach eggs to scalp hair rather than to clothing. The two subspecies are morphologically almost identical, but do not normally interbreed, although they will do so in laboratory conditions. From genetic studies, they are thought to have diverged as subspecies about 30,000–110,000 years ago, when many humans began to wear a significant amount of clothing.[3][4] A much more distantly related species of hair-clinging louse, the pubic or crab louse (Pthirus pubis), also infests humans. It is visually different from the other two species and is much closer in appearance to the lice which infest other primates.[5] Lice infestation of any part of the body is known as pediculosis.[6]
Head lice (especially in children) have been, and still are, subject to various eradication campaigns. Unlike body lice, head lice are not the vectors of any known diseases. Except for rare secondary infections that result from scratching at bites, head lice are harmless, and they have been regarded by some as essentially a cosmetic rather than a medical problem. Head lice infestations might be beneficial in helping to foster a natural immune response against lice which helps humans in defense against the far more dangerous body louse, which is capable of transmission of dangerous diseases.[7]
Edmonds
Edmonds is a city in Snohomish County, Washington, United States, and is a Northern Suburb of Seattle located 11 miles (18 km) north of the city. Edmonds has a view of Puget Sound and both the Olympic Mountains and Cascade Range. The third most populous city in Snohomish County after Everett and Marysville, the population was 39,709 according to the 2010 census and the estimated population in 2015 was 40,490.[3] Based on per capita income, one of the more reliable measures of affluence, Edmonds ranks 20th of 281 areas in the state of Washington.[5]
Edmonds is a port in the Washington State Ferries system. Currently, the only ferry from Edmonds is a run to Kingston, Washington; in the past, there have been much longer routes from Edmonds to Port Townsend, Washington.[6]
Edmonds is the oldest incorporated city in Snohomish County. Logger George Brackett founded Edmonds in 1890, naming the city either for Vermont Sen. George Franklin Edmunds[7] or in association with the nearby Point Edmund, named by Charles Wilkes in 1841 and later changed to Point Edwards.[8] Brackett came to the future site of Edmonds while paddling a canoe north of Seattle, searching for timber. When a gust of wind hit his canoe, Brackett beached in a location later called “Brackett’s Landing”.[9]
The town was named Edmonds in 1884, but was not incorporated until 1890 as an official “village fourth class” of Snohomish County. In that same year, Brackett sold 455 acres (1.84 km2) to the Minneapolis Realty and Investment Company. The town was plotted and a wharf was added along the waterfront. Modest houses and commercial structures sprouted up with a row of shingle mills dominating the cityscape.