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]
Butler
Butler is a city and the county seat of Butler County in the U.S. state of Pennsylvania.[2] It is located 35 miles (56 km) north of Pittsburgh and part of the Pittsburgh metropolitan area. As of the 2010 census, the city population was 13,757.[3] Butler was named the 7th best small town in America by Smithsonian magazine in May 2012.[4]
Butler was named for Maj. Gen. Richard Butler,[5] who fell at the Battle of the Wabash, also known as St. Clair’s Defeat, in western Ohio in 1791.
In 1803 John and Samuel Cunningham became the first settlers in the village of Butler. After settling in Butler, the two brothers laid out the community by drawing up plots of land for more incoming settlers.[5] By 1817, the community was incorporated into a borough.[5]The first settlers were of Irish or Scottish descent and were driving westward from Connecticut. In 1802 the German immigrants began arriving, with Detmar Basse settling in Jackson Township in 1802 and founding Zelienople the following year. After George Rapp arrived in 1805 and founded Harmony, larger numbers of settlers followed. John A. Roebling settled Saxonburg in 1832, by which time most of the county was filled with German settlers.