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]
Niagara Falls
Niagara Falls (/naɪˈæɡrə/ ny-ag-ra) is a city in Niagara County, New York, United States. As of the 2010 census, the city had a total population of 50,193, down from the 55,593 recorded in the 2000 census. It is adjacent to the Niagara River, across from the city of Niagara Falls, Ontario, and named after the famed Niagara Falls which they share. The city is within the Buffalo–Niagara Falls Metropolitan Statistical Area as well as the Western New York region.
While the city was formerly occupied by Native Americans, Europeans who migrated to the Niagara Falls in the mid-17th century began to open businesses and develop infrastructure. Later in the 18th and 19th centuries, scientists and businessmen began harnessing the power of the Niagara River for electricity and the city began to attract manufacturers and other businesses that were drawn by the promise of inexpensive hydroelectric power. After the 1960s, however, the city and region witnessed an economic decline following an attempt at urban renewal under then Mayor Lackey, consistent with the rest of the Rust Belt as industries left the city old line affluent families relocated to nearby suburbs and out of town.
Despite the decline in heavy industry, Niagara Falls State Park and the downtown area closest to the falls continue to thrive as a result of tourism. The population, however, has continued to decline from a peak of 102,394 in the 1960s due to the loss of manufacturing jobs in the area.