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Psocoptera are an order of insects that are commonly known as booklice, barklice or barkflies.〔http://www.brc.ac.uk/schemes/barkfly/introduction.htm〕 They first appeared in the Permian period, 295–248 million years ago. They are often regarded as the most primitive of the hemipteroids. Their name originates from the Greek word ψῶχος, ''psokos'' meaning gnawed or rubbed and πτερά, ''ptera'' meaning wings. There are more than 5,500 species in 41 families in three suborders. Many of these species have only been described in recent years. They range in size from 1–10 millimeters (0.04–0.4 in) in length. The species known as booklice received their common name because they are commonly found amongst old books—they feed upon the paste used in binding. The barklice are found harmlessly on trees, feeding on algae and lichen. No member of this order is currently considered endangered; in fact, in 2007, ''Atlantopsocus adustus'', a species native to Madeira and the Canary Islands, was found to have colonized the mild Cornish coast of southwest England.〔(BBC News, "New insect species arrives in UK" ) 8 November 2007〕 In the 2000s, morphological and molecular evidence has shown that the parasitic lice (Phthiraptera) evolved from within the psocopteran suborder Troctomorpha. In modern systematics, Psocoptera and Phthiraptera are therefore treated together in the order Psocodea.〔Bess, Emilie, Vince Smith, Charles Lienhard, and Kevin P. Johnson (2006) Psocodea. Parasitic Lice (=Phthiraptera), Book Lice, and Bark Lice. Version 8 October 2006 (under construction). http://tolweb.org/Psocodea/8235/2006.10.08 in The Tree of Life Web Project, http://tolweb.org/〕 == Anatomy and biology == Psocids are small, scavenging insects with a relatively generalized body plan. They feed primarily on fungi, algae, lichen, and organic detritus. They have chewing mandibles, and the central lobe of the maxilla is modified into a slender rod. This rod is used to brace the insect while it scrapes up detritus with its mandibles. They also have a swollen forehead, large compound eyes, and three ocelli. Some species can spin silk from glands in their mouth. The forewings are up to 1.5 times as long as the hindwings, and all four wings have a relatively simple venation pattern, with few cross-veins. The legs are slender and adapted for walking, rather than gripping, as in the true lice. The abdomen has nine segments, and no cerci.〔 There is often considerable variation in the appearance of individuals within the same species. Many have no wings or ocelli, and may have a different shape to the thorax. Other, more subtle, variations are also known, such as changes to the development of the setae. The significance of such changes is uncertain, but their function appears to be different from similar variations in, for example, aphids. Like aphids, however, many psocids are parthenogenic, and the presence of males may even vary between different races of the same species.〔 Psocids lay their eggs in minute crevices or on foliage, although a few species are known to be viviparous. The young are born as miniature, wingless versions of the adult. These nymphs typically molt six times before reaching full adulthood. The total lifespan of a psocid is rarely more than a few months.〔 Booklice range from approximately 1mm to 2mm in length (1/25" to 1/13"). Some species are wingless and they are easily mistaken for bedbug nymphs and vice versa. Booklouse eggs take 2 to 4 weeks to hatch and can reach adulthood approximately 2 months later. Adult booklice can live for six months. Besides damaging books, they also sometimes infest food storage areas, where they feed on dry, starchy materials. They are scavengers and do not bite humans.〔US Army Public Health Command fact sheet. http://phc.amedd.army.mil/PHC Resource Library/BookliceFSMar08WestFinal.pdf〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「psocoptera」の詳細全文を読む スポンサード リンク
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