question: Why does lice seem to vanish from the Earth as soon as everyone becomes like 12 years old?
comment: Adult people can generally be trusted not to paw at the heads of their peers and will address any itchy sensations or the feeling of critters running about on their scalp with appropriate medications. There definitely are older people with lice but they tend to be the vagabonds pushing shopping carts down the street full of trash and yelling at the street lamps, not normally functional adults.
passages: According to a scientific paper of Deutsche Bibliothek a ballpark guess of the amount of stone lice in the neighborhood of German libraries amounted to 113.3 billion. The author, Dr. Florian Seiffert, assumes that after the fall of the Berlin Wall, stone lice sought another ecological niche and found it in libraries. The Berlin wall case has been confirmed as well in English sources.
   In April 1800, Benjamin Banneker, who lived near Ellicott's Mills, Maryland, wrote in his record book that he recalled a "great locust year" in 1749, a second in 1766 during which the insects appeared to be "full as numerous as the first", and a third in 1783. He predicted that the insects "may be expected again in the year 1800, which is seventeen years since their third appearance to me".
  
  Section::::Use as human food.
   "D. folliculorum" are not found on newborn babies, but are acquired shortly after birth, most likely due to maternal contact. Few mites are found on children under ten years of age, but nearly all elderly people are infested. The increasing population over time may be due to a small initial infestation gradually growing over time, or may be because levels of the mite's food, sebum, increase with age.
   In April 1800, Benjamin Banneker, who lived near Ellicott's Mills, Maryland, wrote in his record book that he recalled a "great locust year" in 1749, a second in 1766 during which the insects appeared to be "full as numerous as the first" and a third in 1783. He predicted that the insects "may be expected again in the year 1800, which is seventeen years since their third appearance to me".
   It is estimated that the current global population is less than 3,500 members and is declining. The population has decreased by at least 50% over the last 60 years.
  
  Section::::Conservation.:Causes of decline.
   Body lice frequently lay their eggs on or near the seams of clothing. They must feed on blood and usually only move to the skin to feed. They exist worldwide and infest people of all races and can therefore spread rapidly under crowded living conditions where hygiene is poor (homeless, refugees, victims of war or natural disasters).
  
  Section::::Treatment.
   A regressive analysis of historical data of the observation of "P. homerus" indicates that there is no decline in the number of adults found in the wild. However, population size is still facing the great threat of habitat loss, destruction, and climate change.
   Reductions in the size of host populations may cause a long-lasting reduction of louse taxonomic richness, for example, birds introduced into New Zealand host fewer species of lice there than in Europe. Louse sex ratios are more balanced in more social hosts and more female-biased in less social hosts, presumably due to the stronger isolation among louse subpopulations (living on separate birds) in the latter case. The extinction of a species results in the extinction of its host-specific lice. Host-switching is a random event that would seem very rarely likely to be successful, but speciation has occurred over evolutionary time-scales so it must be successfully accomplished sometimes.
   Section::::Development and nymphs.
  
  The hog louse spends its entire life cycle on its host. The life cycle is completed in about 5 weeks. "H. suis" are hemimetabolous (gradual metamorphosis). The metamorphosis of hog lice includes 3 nymphal instars. Once hatched, young lice molt and move to tender areas of the body to feed. Nymphs tend to remain concentrated near the head region. After 10 days, the lice are sexually mature and ready to begin another life cycle.
  
  Section::::Lifespan.
   Lice recorded from impala include "Damalinia aepycerus", "D. elongata", "Linognathus aepycerus" and "L. nevilli"; in a study, ivermectin (a medication against parasites) was found to have an effect on "Boophilus decoloratus" and "Linognathus" species, though not on "Damalinia" species. In a study of impala in South Africa, the number of worms in juveniles showed an increase with age, reaching a peak when impala turned a year old. This study recorded worms of genera such as "Cooperia", "Cooperoides", "Fasciola", "Gongylonema". "Haemonchus", "Impalaia", "Longistrongylus" and "Trichostrongylus"; some of these showed seasonal variations in density.
  
  Section::::Ecology and behaviour.:Diet.
   Section::::Prevention.
   Section::::Alternative medicine.:Gasoline or kerosene.
   Grayling populations have recently begun to decline, and while it is not globally endangered, the species is now considered a priority for conservation efforts in the United Kingdom.
  
  Section::::Geographic range.
   The number of cases of human louse infestations (or pediculosis) has increased worldwide since the mid-1960s, reaching hundreds of millions annually. It is estimated between 1 and 20% of specific groups in Europe are infected.
  
  Despite improvements in medical treatment and prevention of human diseases during the 20th century, head louse infestation remains stubbornly prevalent. In 1997, 80% of American elementary schools reported at least one outbreak of lice. Lice infestation during that same period was more prevalent than chickenpox.
   Section::::Treatment.:Alternative medicine.
   In the nineteenth century, the use of tern feathers and wings in the millinery trade was the main cause of large reductions in common tern populations in both Europe and North America, especially on the Atlantic coasts and inland. Sometimes entire stuffed birds were used to make hats. Numbers largely recovered early in the twentieth century mainly due to legislation and the work of conservation organizations. Although some Eurasian populations are stable, numbers in North America have fallen by more than 70% in the last 40 years, and there is an overall negative trend in the global estimates for this species.
   Lice may reduce host life expectancy if the infestation is heavy, but most seem to have little effect on their host. The habit of dust bathing in domestic hens is probably an attempt by the birds to rid themselves of lice. Lice may transmit microbial diseases and helminth parasites, but most individuals spend their whole life cycle on a single host and are only able to transfer to a new host opportunistically. Ischnoceran lice may reduce the thermoregulation effect of the plumage; thus heavily infested birds lose more heat than others.
   Section::::Interaction with other species.:Invasive species induced population decline.
   The time required for head lice to complete their nymph development to the imago depends on feeding conditions. At minimum, eight to nine days are required for lice having continuous access to a human host. This experimental condition is most representative of head lice conditions in the wild. Experimental conditions where the nymph has more limited access to blood produces more prolonged development, ranging from 12 to 24 days.
   In April 1800, Benjamin Banneker, who lived near Ellicott's Mills, Maryland, wrote in his record book that he recalled a "great locust year" in 1749, a second in 1766 during which the insects appeared to be "full as numerous as the first", and a third in 1783. He predicted that the insects "may be expected again in the year 1800, which is seventeen years since their third appearance to me".
  
  Section::::Popular culture.
   People were expressing concern about the loss of the California condor louse by the 1990s. One 1990 letter to the journal "Nature" began, "In the attempt to save certain species from extinction, for example the California condor, the black-footed ferret and so on, how much attention is being given to the natural parasites?" Another letter to "Nature" closed with "There may be conflicts in conservation needs, forcing us to bid farewell to the gorilla louse or the lice of the Californian condor while retaining their hosts. If so, we should do so in the full knowledge of what is being lost." The "C. californici" extinction is an often-discussed example when emphasizing the importance of parasite conservation both in academic works and elsewhere. One 2011 paper in the "Annual Review of Entomology" called this a "poignant example" of the loss of biodiversity, and noted that the role this species played in its host's ecology was not fully understood. It has also been pointed out that studying the genetics of "C. californici" could have provided information about the California condor's evolutionary history.
   The urbanised camps of cities were noted as succumbing to poisoning during the 1970s to 1980s, identified as the lead in petrol that would accumulate on the fur and enter the body when grooming. The mortality rate from toxic levels of lead in the environment dropped with the introduction of unleaded fuel in 1985.
  
  An introduced plant, the cocos palm "Syagrus romanzoffiana", now banned by some local councils, bears fruit that is toxic to this species and has resulted in their death; the chinese elm "Ulmus parvifolia" and privet present this same hazard. 
   BULLET::::3. The adult body louse is about the size of a sesame seed (2.5–3.5 mm), has six legs, and is tan to greyish-white. Females lay eggs. To live, lice must feed on blood. If separated from their hosts, lice die.
  
  Section::::Origins.
   A study in Japan found that young common cuckoos probably acquire species-specific feather lice from body-to-body contact with other cuckoos between the time of leaving the nest and returning to the breeding area in spring. A total of 21 nestlings were examined shortly before they left their hosts' nests and none carried feather lice. However, young birds returning to Japan for the first time were found just as likely as older individuals to be lousy.
  
  Section::::As a biodiversity indicator.
   Head lice cannot live more than a day or two away from a host. Any remaining eggs will hatch in one to two weeks, and absent a host, the emerging nymphs will die within hours. Thus, simply leaving the school vacant for a week or two is sufficient to disinfect all fomite sources of head louse infection. The return of children to this now-clean environment is an ideal time to check for infestations and attempt to keep the environment lice-free. The California Department of Public Health encourages inspections to be performed on Fridays.
  
presuppositions: Only children have lice. Adults don't get lice.
corrections: Adults can also have lice, but usually have easier access to treat the problem Adults with bad hygiene like homeless people still get lice.
raw_presuppositions: Only children have lice. Adults don't get lice.
raw_corrections: Adults can also have lice, but usually have easier access to treat the problem Adults with bad hygiene like homeless people still get lice.