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Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Protostomia
Cladus: Ecdysozoa
Cladus: Panarthropoda
Phylum: Arthropoda
Subphylum: Hexapoda
Classis: Insecta
Cladus: Dicondylia
Subclassis: Pterygota
Cladus: Metapterygota
Infraclassis: Neoptera
Cladus: Eumetabola
Cladus: Paraneoptera
Superordo: Psocodea
Ordo: Psocoptera
Subordines: PsocomorphaTroctomorphaTrogiomorpha

Genera incertae sedis: Lacroixiella – †Beipiaopsocus – †Empheriopsis

Psocoptera Shipley, 1904
Primary references

Shipley A.E., 1904. The orders of insects. Psyche: A Journal of Entomology.

Additional references

García Aldrete, A.N. 2009. New species and records of Psocoptera (Insecta) from Argentina). Zootaxa 2219: 1–17. Abstract & excerpt PDF. Reference page.
Anonby, J.E. 2019. Psocoptera of Canada. Pp 295–299 In Langor, D.W. & Sheffield, C.S. (eds.). The Biota of Canada – A Biodiversity Assessment. Part 1: The Terrestrial Arthropods. ZooKeys 819: 520 pp. Reference page. . DOI: 10.3897/zookeys.819.27640 Reference page.
Lienhard, C. 2003: Nomenclatural amendments concerning Chinese Psocoptera (Insecta), with remarks on species richness. Revue suisse de zoologie 110(4): 695–721. BHL Reference page.
Lienhard, C.; Smithers, C.N. 2002: Psocoptera (Insecta): world catalogue and bibliography. Instrumenta biodiversitatis, (5) Reference page.
Li, F. 2002: Psocoptera of China. Science Press, Beijing. ISBN 7030091736 [2 volumes, July 2002, not seen].
Mockford, E.L., Lienhard, C. & Yoshizawa, K. 2013. Revised classification of Psocoptera from Cretaceous amber, a reassessment of published information. Insecta matsumurana (n.s.) 69: 1–26. Abstract and full article (PDF). Reference page.
Smithers, C.N. 1967: A catalogue of the Psocoptera of the World. Australian zoologist 14(1): 1-145. BHL Reference page.
Smithers, C.N. 1969: The Psocoptera of New Zealand. Records of the Canterbury Museum 8(4): 259-344. BUGZ. Reference page.
Smithers C.N., 1972. The classification and phylogeny of the Psocoptera. Australian Museum memoirs, (14 ) DOI: 10.3853/j.0067-1967.14.1972.424.
Smithers C.N., 1990. Keys to the families and genera of Psocoptera (Arthropoda: Insecta). Technical reports of the Australian Museum, (2 ) ISBN 0 7305 7440 7 DOI: 10.3853/j.1031-8062.2.1990.77.
Smithers C.N., O'Connor J.P. & Peters J.V., 1999. A list of Irish Psocoptera (Insecta) (booklice, barklice, psocids). Irish naturalists' journal, 26 (7/8): 228–235 (JSTOR).


Psocid News, nos 4-7. -
Psocoptera – Taxon details on Fauna Europaea.
Psocoptera – Taxon details on Interim Register of Marine and Non-marine Genera (IRMNG).
Psocoptera – Taxon details on Integrated Taxonomic Information System (ITIS).
Psocoptera – Taxon details on National Center for Biotechnology Information (NCBI).
Psocoptera – Taxon details on New Zealand Organisms Register (NZOR).
Psocoptera - Taxon details on Psocodea Species File.

Psocoptera in the World Register of Marine Species

Vernacular names
Alemannisch: Staublyys
беларуская: Сенаеды
čeština: Pisivky
dansk: Barklus
Deutsch: Staubläuse
English: Barkfly
eesti: Kõdutäilised
français: Psoque
magyar: Fürgetetvek
日本語: チャタテムシ目 (噛虫目)
한국어: 다듬이벌레목 (교충목)
lietuvių: Šiengraužiai
latviešu: Ķērpjutis
Nederlands: Stofluis
norsk: Støvlus
polski: Psotniki
русский: Сеноеды
slovenščina: Prašne uši
中文: 嚙蟲目

Psocoptera are a paraphyletic group of insects that are commonly known as booklice, barklice or barkflies.[1] The name Psocoptera has been replaced with Psocodea in recent literature, with the inclusion of the former order Phthiraptera into Psocodea (as part of the suborder Troctomorpha).[2][3][4][5]

These insects first appeared in the Permian period, 295–248 million years ago. They are often regarded as the most primitive of the hemipteroids.[6] Their name originates from the Greek word ψῶχος, psokhos meaning gnawed or rubbed and πτερά, ptera meaning wings.[7] There are more than 5,500 species in 41 families in three suborders. Many of these species have only been described in recent years.[8] They range in size from 1–10 millimetres (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 on trees, feeding on algae and lichen.

Anatomy and biology

Psocids are small, scavenging insects with a relatively generalized body plan. They feed primarily on fungi, algae, lichen, and organic detritus in nature but are also known to feed on starch-based household items like grains, wallpaper glue and book bindings.[9] 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. Their bodies are soft with a segmented abdomen.[10] Some species can spin silk from glands in their mouth.[11] They may festoon large sections of trunk and branches in dense swathes of silk.[12]

Some psocids have small ovipositors that 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 wings, if present, are held tent-like over the body.[10] The legs are slender and adapted for jumping, rather than gripping, as in the true lice. The abdomen has nine segments, and no cerci.[11]

There is often considerable variation in the appearance of individuals within the same species. Many have no wings or ovipositors, 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.[11]

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.[11]

Booklice range from approximately 1 mm to 2 mm 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 two to four weeks to hatch and can reach adulthood approximately two 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. Although some psocids feed on starchy household products, the majority of psocids are woodland insects with little to no contact with humans, therefore they are of little economic importance. They are scavengers and do not bite humans.[13]

Psocids can affect the ecosystems in which they reside. Many psocids can affect decomposition by feeding on detritus, especially in environments with lower densities of predacious micro arthropods that may eat psocids.[14] The nymph of a psocid species, Psilopsocus mimulus, is the first known wood-boring psocopteran. These nymphs make their own burrows in woody material, rather than inhabiting vacated, existing burrows. This boring activity can create habitats that other organisms may use.[15]
Interaction with humans

Some species of psocids, such as Liposcelis bostrychophila, are common pests of stored products.[16] Psocids, among other arthropods, have been studied to develop new pest control techniques in food manufacturing. One study found that modified atmospheres during packing (MAP) helped to control the reoccurrence of pests during the manufacturing process and prevented further infestation in the final products that go to consumers.[17]

In the 2000s, morphological and molecular phylogenetic evidence has shown that the parasitic lice (Phthiraptera) evolved from within the psocopteran suborder Troctomorpha, thus making Psocoptera paraphyletic with respect to Phthiraptera.[18][19] In modern systematics, Psocoptera and Phthiraptera are therefore treated together in the order Psocodea.[20]

Here is a cladogram showing the relationships within Psocodea, with the former grouping Psocoptera highlighted:[2]











"National Barkfly (Outdoor Psocoptera) Recording Scheme".
De Moya, Robert S.; Yoshizawa, Kazunori; Walden, Kimberly K. O.; Sweet, Andrew D.; et al. (2021). "Phylogenomics of Parasitic and Nonparasitic Lice (Insecta: Psocodea): Combining Sequence Data and Exploring Compositional Bias Solutions in Next Generation Data Sets". Systematic Biology. 70 (4): 719–738. doi:10.1093/sysbio/syaa075. PMID 32979270.
Johnson, Kevin P.; Smith, Vincent S. (2021). "Psocodea species file online, Version 5.0". Retrieved 2021-11-01.
"Psocodea". GBIF. Retrieved 2021-11-01.
"Psocodea". ITIS. Retrieved 2021-11-01.
Christopher O'Toole (2002). Firefly Encyclopedia of Insects and Spiders. Toronto: Firefly Books. ISBN 978-1-55297-612-8.
John R. Meyer (5 March 2005). "Psocoptera". North Carolina State University. Archived from the original on 5 February 2007.
Alfonso N. García Aldrete (2006). "New genera of Psocoptera (Insecta), from Mexico, Belize and Ecuador (Psoquillidae, Ptiloneuridae, Lachesillidae)" (PDF). Zootaxa. 1319: 1–14. doi:10.11646/zootaxa.1319.1.1.
Green, P.W.C.; Turner, B.D. (January 15, 2004). "Food-selection by the booklouse, Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae)". Journal of Stored Products Research. 41 (1): 103–113. doi:10.1016/j.jspr.2004.01.002.
Gullan & Granston (2005). The Insects: An Outline of Entomology 3rd Edition. pp. 499–505.
Hoell, H.V., Doyen, J.T. & Purcell, A.H. (1998). Introduction to Insect Biology and Diversity, 2nd ed. Oxford University Press. pp. 404–406. ISBN 978-0-19-510033-4.
"Psocoptera - Barklice, Booklice, Psocids -- Discover Life".
"Stored Product Pests: Booklice (Psocids) FAC". US Army Public Health Command fact sheet.
Whitford, W.G. (2000). Invertebrates as webmasters in ecosystems: Keystone arthropods as webmasters in desert ecosystems. UK: CAB International. pp. 25–43. ISBN 0-85199-394-X.
Smithers, C.N. (1995). "Psilopsocus mimulus Smithers (Psocoptera: Psilopsocidae), The first known wood boring psocopteran". Australian Journal of Entomology. 34 (2): 117–120. doi:10.1111/j.1440-6055.1995.tb01299.x.
Stejskal, V.; Hubert, J.; Aulicky, R.; Kucerova, Z. (October 2015). "Overview of present and past and pest-associated risks in stored food and feed products: European perspective". Journal of Stored Products Research. 64: 122–132. doi:10.1016/j.jspr.2014.12.006.
Riudavets, Jordi; Castañé, Cristina; Alomar, Oscar; Pons, María José; Gabarra, Rosa (April 2009). "Modified atmosphere packaging (MAP) as an alternative measure for controlling ten pests that attack processed food products". Journal of Stored Products Research. 45 (2): 91–96. doi:10.1016/j.jspr.2008.10.001.
Yoshizawa, K.; Johnson, K. P. (2006). "Morphology of male genitalia in lice and their relatives and phylogenetic implications". Systematic Entomology. 31 (2): 350–361. doi:10.1111/j.1365-3113.2005.00323.x.
Johnson, K. P.; Yoshizawa, K.; Smith, V. S. (2004). "Multiple origins of parasitism in lice". Proceedings of the Royal Society of London. 271 (1550): 1771–1776. doi:10.1098/rspb.2004.2798. PMC 1691793. PMID 15315891.
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). in The Tree of Life Web Project,

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