Ischnocera

{{Short description|Parvorder of lice}} {{good article}} {{Automatic taxobox | image = Louse (265 05) Columbicola columbae (Mallophaga).jpg | image_caption = ''Columbicola columbae'' under a microscope | image_alt = Columbicola columbae under a microscope | display_parents = 3 | taxon = Ischnocera | authority = Kellogg, 1896 | subdivision_ranks = Families | subdivision = * '''Philopteroidea''' (superfamily) ** Goniodidae ** Heptapsogasteridae ** Lipeuridae ** Philopteridae ** Trichophilopteridae | subdivision_ref = <ref name="PsocodeaSpeciesFile">{{Cite web| website = Psocodea Species File |title = Ischnocera Kellogg, 1896 |last1 = Hopkins |first1 = H. |last2 = Johnson |first2 = K. P. |last3 = Smith |first3 = V. S. |url = https://psocodea.speciesfile.org/otus/879883/overview |access-date=May 16, 2025}}</ref> }}

'''Ischnocera''' is a large parvorder of lice from the infraorder Phthiraptera. The parvorder consists of chewing lice, which feed on the feathers and skin debris of birds. Many species of Ischnocera have evolved an elongated body shape, which allows them to conceal themselves within plumage to avoid being dislodged during preening or flight. Species in Ischnocera spend their entire lives living on a host and attach themselves to hippoboscid flies to help move across individual birds. Ischnocera contain the large family Philopteridae, along with a few other minor families. Ischnocera are distributed globally, with around 3,800 species identified. These lice are very host-specific, and each species rarely parasitizes outside of its preferred bird species. Birds infested by ischnoceran species can experience discomfort and damage to reproductive systems.

==Classification== Ischnocera previously included the mammalian parasitic lice Trichodectera, but phylogenetic studies had found the grouping to be paraphyletic, specifically in regard to the two major families Philopteridae and Trichodectidae. To resolve this, de Moya ''et al.'' proposed retaining the majority of the species (including Philopteridae) within Ischnocera, and then moving Trichodectidae to their own grouping called Trichodectera.<ref name="deMoya2021">{{cite journal |last1=de Moya |first1=Robert S. |last2=Yoshizawa |first2=Kazunori |last3=Walden |first3=Kimberly K. O. |last4=Sweet |first4=Andrew D. |last5=Dietrich |first5=Christopher H. |last6=Kevin P. |first6=Johnson |date=2021-06-16 |editor-last=Buckley |editor-first=Thomas |title=Phylogenomics of Parasitic and Nonparasitic Lice (Insecta: Psocodea): Combining Sequence Data and Exploring Compositional Bias Solutions in Next Generation Data Sets |url=https://academic.oup.com/sysbio/article/70/4/719/5912026 |journal=Systematic Biology |volume=70 |issue=4 |pages=719–738 |doi=10.1093/sysbio/syaa075 |pmid=32979270 |doi-access=free}}</ref>

Below is a cladogram showing the position of Ischnocera within Phthiraptera:<ref name="deMoya2021"/> {{clade |label1='''Phthiraptera''' |1={{clade |1={{clade |label1='''Ischnocera''' |sublabel1=(chewing lice of birds) |1=Philopteridae 40px |label2=(lice of mammals) |2={{clade |1={{clade |1=Anoplura (sucking lice of mammals) 30px |2=Rhynchophthirina (drilling lice of elephants and warthogs) 70px }} |label2=Trichodectera |2=Trichodectidae (chewing lice of mammals) 40px }} }} |2=Amblycera (chewing lice of birds) 25px }} }}

== Characteristics == Ischnoceran lice are characterized by pulvinus-like mandibles thickened at the base, and two tarsal claws on each of their legs.<ref name="Allaby_2020_322">{{harvnb|Allaby|2020|p=322}}</ref><ref name="Allaby_2020_476">{{harvnb|Allaby|2020|p=476}}</ref> Like all chewing lice, they are wingless with dorsoventrally flattened bodies. They are permanent ectoparasites that live all of their lives on a host bird.<ref>{{Cite journal |last=Smith |first=Vincent S. |date=2001-05-01 |title=Avian louse phylogeny (Phthiraptera: Ischnocera): a cladistic study based on morphology |url=https://doi.org/10.1111/j.1096-3642.2001.tb02272.x |journal=Zoological Journal of the Linnean Society |volume=132 |issue=1 |pages=81–144 |doi=10.1111/j.1096-3642.2001.tb02272.x |issn=0024-4082}}</ref> They do not have ocelli, and their antennae are broken into three to five segments.<ref name="Vincent_2009_777">{{harvnb|Resh|2009||p=777}}</ref> The length of adults ranges from 0.3 to 12 mm depending on the species.<ref name="Vincent_2009_777" /> Their heads are typically broad and triangular-shaped, with hook-like structures on the surface. The postclypeus region is broad, with vertical stripes of thin cuticles.<ref name=":0">{{Cite book |last=Manglik |first=Rohit |title=Insect Morphology and Phylogeny |date=July 9, 2024 |publisher=EduGorilla Publication |isbn=9789368176152 |pages=307}}</ref> The head also contains repeating ridges, which is used to help strengthen the exoskeleton.<ref name=":0" /> Unlike their close taxonomic relative Amblycera, Ischnocera lack maxillary palps used to manipulate food.<ref name=":7">{{Cite web |date=2022-02-15 |title=Lice (Phthiraptera) - Factsheet for health professionals |url=https://www.ecdc.europa.eu/en/all-topics-z/disease-vectors/facts/factsheet-lice-phthiraptera |access-date=2025-06-09 |website=www.ecdc.europa.eu |language=en}}</ref> Their color is typically brown, but some species can be black or white, and their rostra are elongated significantly.<ref>{{Cite book |last1=Beutal |first1=Rolf |title=Insect morphology and phylogeny : a textbook for students of entomology |last2=Friedrich |first2=Frank |last3=qin-Ge |first3=Si |last4=Yang |first4=Xingke |publisher=De Gruyter |year=2014 |isbn=9783110264043 |location=Berlin |pages=307 |language=en |doi=10.1515/9783110264043}}</ref> Their abdomens are usually divided into eight segments, with the males characterized by having a large anterior plate, and the females having a continuous plate across their backs.<ref>{{Harvnb|Kumar|Tandan|1971|p=119}}</ref> Younger members of the Ischnocera's evolutionary lineage have paired structures called mycetomes.<ref>{{Cite book |last1=Bourtzis |first1=Kostas |title=Insect Symbiosis, Volume 3 |last2=Miller |first2=Thomas A. |publisher=CRC Press |isbn=978-1040209806 |publication-date=October 28, 2008 |page=168}}</ref> Species of Ischnocera are very host-specific, with some birds receiving their classification based on the individual species of lice they are hosting.<ref>{{Cite news |date=November 17, 1946 |title=Characteristics of Louse Prove Interesting to Scribe |url=https://www.newspapers.com/image/1194112473/?match=1&terms=Ischnocera |work=The Houston Post |pages=24}}</ref>

=== Lifecycle ===

Ischnoceran lice can survive several weeks living off of their hosts.<ref>{{cite web |title=Lice Dogs and Cats: chewing (Mallophaga), and sucking (Anoplura) - Learn About Parasites - Western College of Veterinary Medicine |url=https://wcvm.usask.ca/learnaboutparasites/parasites/lice-chewing-mallophaga,-and-sucking-anoplura.php |access-date=2025-06-09 |website=wcvm-learnaboutparasites |language=en}}</ref> Their lifecycle consists of a simple metamorphosis, with three separate stages. Adult female lice lay eggs (also referred to as "nits") on the bodies of their host, where they develop and hatch within 4-15 days.<ref name=":7" /> This is followed by the nymph stage for around 3-8 days, before finishing development in adults.<ref name=":7" /> After the lice are sufficiently fed, the males use their antennae to touch the heads of females to signal they are ready to mate.<ref>{{cite book |last=Marshall |first=Adrian G. |title=The Ecology of Ectoparasitic Insects |publisher=Academic Press |year=1981 |location=London |page=68|oclc=8166601}}</ref> When the adult females lay eggs, they typically do so in batches of 200 to 300 that are glued onto the feathers of their hosts to repeat the cycle.<ref name="Taylor_Coop_Wall_2013_71">{{harvnb|Taylor|Coop|Wall|2013|p=71}}</ref> The glue is a cement-like material that is excreted from the louse's oviducts.<ref>{{cite journal |last=Ahmad |first=Aftab |date=June 25, 2018 |title=Egg laying pattern and the egg morphology of an ischnoceran louse, Goniocotes jirufti (Ansari, 1947) parasitizing black partridges, Francolinus francolinus (Phthiraptera: Ischnocera) |journal=Journal of Applied and Natural Science |volume=10 |issue=3 |pages=838–840 |doi=10.31018/JANS.V10I3.1714 |s2cid=92446624 }}</ref> Ischnocera are unable to move from the feathers to the skin of their hosts due to their specialized anatomy.<ref name=":3">{{Cite web |last1=T. Atkinson |first1=Carter J. |last2=Thomas |first2=Nancy |last3=Hunter |first3=D. Bruce |year=2008 |title=Parasitic Diseases of Wild Birds |url=https://darwin.biology.utah.edu/PDFs/BC7.pdf |access-date=June 9, 2025 |website=darwin.biology.utah.edu}}</ref> To move across individual birds, ischnocerans "hitchhike" on hippoboscid flies that land on the current host. This is done to avoid competition from other lice by finding a new host on which to feed.<ref>{{Cite journal |last1=Pistone |first1=John P. |last2=Light |first2=Jessica E. |last3=Campbell |first3=Tyler A. |last4=Catanach |first4=Therese A. |last5=Voelker |first5=Gary |year=2021 |title=Restricted Geographic Sampling Yields Low Parasitism Rates but Surprisingly Diverse Host Associations in Avian Lice (Insecta: Phthiraptera) from South Texas |journal= Diversity|volume=13 |issue=9 |pages=430 |doi=10.3390/d13090430|doi-access=free |bibcode=2021Diver..13..430P }}</ref>

[[File:Parasite200132-fig5 Insect ectoparasites from wild passerine birds in the Azores Islands.png|thumb|300x300px|''Guimaraesiella tovornikae'' (A - male, B - female) on the Eurasian blackcap, and ''Sturnidoecus'' (C - male, D - female) on the common blackbird]]

=== Distribution ===

Ischnocera are distributed globally, with 3,800 different species across all the continents except Antarctica.<ref name=":8">{{Cite journal |last1=Takano |first1=Oona M. |last2=Voelker |first2=Gary |last3=Gustafsson |first3=Daniel R. |last4=Light |first4=Jessica E. |year=2019 |title=Molecular phylogeny and novel host associations of avian chewing lice (Insecta: Phthiraptera) from South Africa |url=https://dx.doi.org/10.1111/syen.12319 |journal=Systematic Entomology |volume=44 |issue=2 |pages=289–304 |doi=10.1111/syen.12319 |bibcode=2019SysEn..44..289T |url-access=subscription }}</ref> The majority of species identified reside in Europe, North America, and the Neotropical realm.<ref name=":8" /> They are found in areas where birds suffer from malnutrition and overcrowding, as well, due to the ease of moving across individuals.<ref name=":7" />

== Feeding == Ischnocerans primarily feed on the feathers and skin debris of different species of birds. They are highly host specific, and usually do not deviate from their chosen species.<ref name=":2">{{Cite book |last1=Ricardo Panizzi |first1=Antônio |title=Insect Bioecology and Nutrition for Integrated Pest Management |last2=Parra |first2=José R. P. |date=March 8, 2012 |publisher=Taylor & Francis |isbn=978-1439837085 |page=647}}</ref> They do not consume the blood of their hosts, and are found within the feathers to avoid being dislodged.<ref name=":2" /> The lice have specific areas of the bird on which they prefer to feed and typically do not move away from that area.<ref>{{Harvnb|Lucius|2017|p=418}}</ref> Preferred areas of the birds are the head, neck, and the croup.<ref>{{Harvnb|Samour|2016|p=434}}</ref> Birds in humid regions are more prone to being infested by Ischnocera, with the trend continuing regardless of the species.<ref>{{cite book |last=Marcondes |first=Carlos |title=Arthropod Borne Diseases |publisher=Springer, Cham |year=2017 |isbn=9783319138848 |page=505 |oclc=962834440}}</ref> Species such as the ''Columbicola columbae'' feed mostly on the feather's barbules, as well as keratin-rich skin near the wing and tail feathers.<ref>{{Cite journal |last1=Singh |first1=Suneel Kumar |last2=Arya |first2=Surman |last3=Singh |first3=Sanjay Kumar |last4=Khan |first4=Vikram |date=2010-06-01 |title=Feeding and reproductive behaviour of pigeon slender louse, Columbicola columbae (Phthiraptera, Insecta, Ischnocera) |url=https://journals.ansfoundation.org/index.php/jans/article/view/111 |journal=Journal of Applied and Natural Science |volume=2 |issue=1 |pages=126–133 |doi=10.31018/jans.v2i1.111 |issn=2231-5209}}</ref> The lice also tend to feed on oils secreted by the bird.<ref>{{Harvnb|Carro|Andrés|2015|p=106}}</ref> Members of the Ischnocera contain endosymbiotic bacteria that aid in the digestion of the debris and feathers of their hosts.<ref name=":3" />

== Effects ==

Ischnocera can cause significant irritation and damage to the feathers of their hosts. Infestations can cause damage to egg production and growth in poultry.<ref>{{Cite web |title=Bird louse {{!}} Parasitic, Feather-Feeding, Poultry {{!}} Britannica |url=https://www.britannica.com/animal/bird-louse |access-date=2025-06-09 |website=www.britannica.com}}</ref> The lice can cause preening and scratching in hosts, along with the loss of feathers, potentially resulting in bald spots.<ref name=":4">{{cite web |last=Begazo |first=Alfredo |date=2023-12-21 |title=Feather Lice in Backyard Birds |url=https://avianreport.com/feather-lice/ |access-date=2025-06-09 |website=Avian Report}}</ref> Birds with poor hygiene and weak immune systems are vulnerable to infestations due to a reduced ability to fight them.<ref name=":4" /> Bald patches in birds can result in decreased insulation and disease susceptibility.<ref name=":5">{{Cite web |title=Feather Picking in Pet Parrots |url=https://www.cliniciansbrief.com/article/feather-picking-pet-parrots |access-date=2025-06-09 |website=www.cliniciansbrief.com}}</ref> Self-grooming by the bird can help dislodge some of the infestation, although it is usually not enough to remove them entirely. The ability to remove the lice largely depends on the size of the bird's beak.<ref>{{Cite journal |last1=Galloway |first1=Terry |last2=Lamb |first2=Robert |year=2021 |title=Population Dynamics of Chewing Lice (Phthiraptera) Infesting Birds (Aves) |url=https://www.annualreviews.org/docserver/fulltext/en/66/1/annurev-ento-041420-075608.pdf?expires=1749506228&id=id&accname=guest&checksum=E4E5F3AE0191FB344F4DC0E5464452FC |access-date=June 9, 2025 |journal=Annual Review of Entomology |volume=66 |pages=209–224 |doi=10.1146/annurev-ento-041420-075608 }}</ref> If a bird has a damaged beak, it can become significantly more susceptible to infestations. Some birds use an oil they secrete from their uropygial gland and spread it across their bodies to make the lice's ability to attach themselves more difficult.<ref name=":5" /> Flight performance, lifespan, and sexual selection are negatively affected in infested birds. The host's metabolic rate and overall body mass are lowered during an infestation.<ref name=":6">{{Cite journal |last=Zerek |first=Aykut |title=Chewing Lice (Psocodea: Phthiraptera) Detected in Wild Birds in Hatay, Türkiye, a New Record of the Colpocephalum ecaudati Price and Beer from Black Kite (Milvus migrans) |url=https://vetdergikafkas.org/uploads/pdf/pdf_KVFD_3082.pdf |access-date=June 9, 2025 |journal=Kafkas Universitesi Veteriner Fakultesi Dergisi |date=2024 |doi=10.9775/kvfd.2023.30713}}</ref> The lice can serve as vectors carrying bacterial diseases to the birds.<ref name=":6" /> Infested birds show nervousness and discomfort, especially while they are nesting.<ref>{{Cite news |date=July 16, 1960 |title=No Competition |url=https://www.newspapers.com/image/1113449888 |work=The Grand Rapids Press |pages=16}}</ref> Spraying the infested bird with pesticides can help kill the lice.<ref name=":9">{{Cite book |last=Rezai |first=Nima |title=Encyclopedia of Infection and Immunity |publisher=Elsevier |year=2022 |isbn=9780323903035 |location=Amsterdam |pages=994 |oclc=1397392951}}</ref>

==Families==

Ischnocera comprises these families:<ref name="PsocodeaSpeciesFile"/><ref>{{Cite web |title=Ischnocera Kellogg, 1896 {{!}} COL |url=https://www.catalogueoflife.org/data/taxon/BW9V7 |access-date=2025-06-10 |website=www.catalogueoflife.org}}</ref> * '''Philopteroidea''' Nitzsch, 1938 (superfamily) ** Goniodidae Mjoberg, 1910<ref>Gustafsson, D.R., Li, Z., Tian, C., Ren, M., Sun, X. & Zou, F. (2025) Revision of genera in Goniodidae (Phthiraptera: Ischnocera) parasitising gamefowl (Aves: Galliformes) with descriptions of six new genera, one new subgenus and seven new species. Zootaxa, 5731 (1), 1–99. https://doi.org/10.11646/zootaxa.5731.1.1 </ref> ** Heptapsogasteridae Carriker, 1936 ** Lipeuridae Mjoberg, 1910 ** Philopteridae Nitzsch, 1818 ** Trichophilopteridae Mjoberg, 1919

== References ==

== Sources ==

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Category:Lice Category:Parasitic insects Category:Parasites of birds