Editing Tick (section)

==Biology==
===Taxonomy and phylogeny===
[[File:Tick in amber carrying spirochetes.jpg|thumb|left|Fossilized tick in Dominican [[amber]]]]

Ticks belong to the [[Parasitiformes]], a distinctive group of mites that are separate from the main group of mites, the [[Acariformes]]. Whether the two groups are more closely related to each other than to other arachnids is uncertain, and studies often recover them as not closely related.<ref>{{Cite journal|last=Giribet|first=Gonzalo|date=March 2018|title=Current views on chelicerate phylogeny—A tribute to Peter Weygoldt|url=https://linkinghub.elsevier.com/retrieve/pii/S0044523118300044|journal=Zoologischer Anzeiger|language=en|volume=273|pages=7–13|doi=10.1016/j.jcz.2018.01.004|bibcode=2018ZooAn.273....7G |s2cid=90344977 |url-access=subscription}}</ref> Within the Parasitiformes, ticks are most closely related to the [[Holothyrida]], a small group of free living scavengers with 32 described species confined to the landmasses that formed the supercontinent [[Gondwana]].<ref name=":0" />

Relationships among members of the Parasitiformes, after Klompen, 2010:<ref>{{Cite journal |last=Klompen |first=H. |date=2010-06-30 |title=Holothyrids and ticks: new insights from larval morphology and DNA sequencing, with the description of a new species of Diplothyrus (Parasitiformes: Neothyridae) |url=http://www1.montpellier.inra.fr/CBGP/acarologia/article.php?id=1970 |journal=Acarologia |volume=50 |issue=2 |pages=269–285 |doi=10.1051/acarologia/20101970 |issn=0044-586X |s2cid=55284869 |doi-access=free}}</ref>
{{clade
|label1=Parasitiformes
|1={{clade
   |1=[[Opilioacarida]]     
   |2={{clade
      |1=[[Mesostigmata]]
      |2={{clade
         |1=[[Holothyrida]]
         |2='''Ixodida''' (ticks)
         }}
      }}
   }}
}}

Fossilized ticks have been discovered from the end of the Early Cretaceous onwards, most commonly in amber. The oldest discovered tick fossils are an argasid bird tick from Late Cretaceous ([[Turonian]] ~94-90 million years ago) aged [[New Jersey amber]],<ref name="KlompenGrimaldi" /> and various ticks found in [[Burmese amber]], including ''[[Khimaira fossus|Khimaira]]'' which does not belong to any living family of tick, the living genus ''[[Nuttalliella]]'' and the possible [[Nuttalliellidae|nuttalliellid]] genera ''[[Deinocroton]]'' and ''[[Legionaris]]'',<ref name=":3">{{Cite journal |last1=Chitimia-Dobler |first1=Lidia |last2=Handschuh |first2=Stephan |last3=Dunlop |first3=Jason A. |last4=Pienaar |first4=Ronel |last5=Mans |first5=Ben J. |date=2024-04-16 |title=Nuttalliellidae in Burmese amber: implications for tick evolution |journal=Parasitology |volume=151 |issue=9 |language=en |pages=891–907 |doi=10.1017/S0031182024000477 |issn=0031-1820 |doi-access=free|pmid=38623697 |pmc=11770530 }}</ref> as well as the members of the living ixodid genera ''[[Amblyomma]]'', ''[[Ixodes]]'', ''[[Haemaphysalis]], [[Bothriocroton]]'' and ''[[Archaeocroton]]'' dating the earliest [[Cenomanian]] stage of the Late Cretaceous, around {{Ma|99}}.<ref name="PeñalverArillo2017">{{cite journal|vauthors=Peñalver E, Arillo A, Delclòs X, Peris D, Grimaldi DA, Anderson SR, Nascimbene PC, Pérez-de la Fuente R|date=December 2017|title=Ticks parasitised feathered dinosaurs as revealed by Cretaceous amber assemblages|journal=Nature Communications|volume=8|issue=1|pages=1924|bibcode=2017NatCo...8.1924P|doi=10.1038/s41467-017-01550-z|pmc=5727220|pmid=29233973}}</ref><ref name=":0" /><ref>{{Cite journal |last1=Chitimia-Dobler |first1=Lidia |last2=Mans |first2=Ben J. |last3=Handschuh |first3=Stephan |last4=Dunlop |first4=Jason A. |date=n.d. |title=A remarkable assemblage of ticks from mid-Cretaceous Burmese amber |journal=Parasitology |volume=149 |issue=6 |language=en |pages=820–830 |doi=10.1017/S0031182022000269|pmid=35241194 |pmc=10090602 |s2cid=247227499 |issn=0031-1820|doi-access=free }}</ref><ref>{{Cite journal |last1=Chitimia-Dobler |first1=Lidia |last2=Dunlop |first2=Jason A. |last3=Pfeffer |first3=Timo |last4=Würzinger |first4=Felix |last5=Handschuh |first5=Stephan |last6=Mans |first6=Ben J. |date=February 2023 |title=Hard ticks in Burmese amber with Australasian affinities |journal=Parasitology |language=en |volume=150 |issue=2 |pages=157–171 |doi=10.1017/S0031182022001585 |issn=0031-1820 |pmc=10090639 |pmid=36341553}}</ref> An undescribed juvenile tick is known from late [[Albian]] [[amber]], dating to 105 million years ago.<ref name="PeñalverArillo2017" /> The younger [[Baltic amber|Baltic]] and [[Dominican amber]]s have also yielded examples that can be placed in living genera.<ref>{{cite journal | vauthors = Dunlop JA, Apanaskevich DA, Lehmann J, Hoffmann R, Fusseis F, Ehlke M, Zachow S, Xiao X | title = Microtomography of the Baltic amber tick Ixodes succineus reveals affinities with the modern Asian disease vector Ixodes ovatus | journal = BMC Evolutionary Biology | volume = 16 | issue = 1 | pages = 203 | date = October 2016 | pmid = 27724841 | pmc = 5057450 | doi = 10.1186/s12862-016-0777-y | doi-access = free | bibcode = 2016BMCEE..16..203D }}</ref> A phylogenetic analysis suggests that the last common ancestor of all living ticks likely lived around 195 million years ago in the Southern Hemisphere, in what was then Gondwana.<ref name=":0">{{Cite journal|last1=Beati|first1=Lorenza|last2=Klompen|first2=Hans|date=2019-01-07|title=Phylogeography of Ticks (Acari: Ixodida)|url=https://www.annualreviews.org/doi/10.1146/annurev-ento-020117-043027|journal=Annual Review of Entomology|language=en|volume=64|issue=1|pages=379–397|doi=10.1146/annurev-ento-020117-043027|pmid=30354695|s2cid=53023797|issn=0066-4170|url-access=subscription}}</ref>

Ticks belong to three different families. The majority of tick species belong to the two families: Ixodidae (hard ticks) and Argasidae (soft ticks). The third living family is [[Nuttalliellidae]], named for the bacteriologist [[George Nuttall]]. It comprises a single species, ''Nuttalliella namaqua'',<ref name="list">[[#Guglielmone|Guglielmone et al. (2010)]]</ref><ref>[[#Goddard|Goddard (2008)]]: [https://books.google.com/books?id=f-huycwyEvwC&pg=PA80 p. 80]</ref> and as such is a [[monotypic taxon]]. ''Nuttalliella namaqua'' is found in southern Africa ranging from [[Tanzania]] to [[Namibia]] and [[South Africa]].<ref name="list" /><ref>[[#Keirans|Keirans et al. (1976)]]</ref>

Relationships of living and extinct tick families, after Chitimia-Dobler et al. 2022:<ref>{{Cite journal |last1=Chitimia-Dobler |first1=Lidia |last2=Mans |first2=Ben J. |last3=Handschuh |first3=Stephan |last4=Dunlop |first4=Jason A. |date=May 2022 |title=A remarkable assemblage of ticks from mid-Cretaceous Burmese amber |journal=Parasitology |language=en |volume=149 |issue=6 |pages=820–830 |doi=10.1017/S0031182022000269 |issn=0031-1820 |pmc=10090602 |pmid=35241194}}</ref>{{clade
|label1='''Ixodida'''
|1={{clade
|1={{clade
|1={{extinct}}[[Deinocrotonidae]]
|2=[[Nuttalliellidae]]
}}
|2={{clade
|1=[[Ixodidae]]
|2=[[Argasidae]]
|3={{extinct}}[[Khimairidae]]
}}}}}}The Ixodidae contain over 700 species of hard ticks with a [[scute|scutum]] or hard shield, which the Argasidae lack. The Argasidae contain about 200 species; the genera accepted {{as of|2010|lc=y}} are ''[[Antricola]]'', ''[[Argas]]'', ''[[Nothoaspis]]'', ''[[Ornithodoros]]'', and ''[[Otobius]]''.<ref name="list" /> They have no scutum, and the [[Gnathosoma|capitulum]] (mouth and feeding parts) is concealed beneath the body.<ref name="Molyneux" /> The [[phylogeny]] of the Ixodida within the Acari is shown in the cladogram, based on a 2014 [[maximum parsimony]] study of [[amino acid]] sequences of 12 [[mitochondria]]l proteins. The Argasidae appear [[Monophyly|monophyletic]] in this study.<ref>{{cite journal | vauthors = Gu XB, Liu GH, Song HQ, Liu TY, Yang GY, Zhu XQ | title = The complete mitochondrial genome of the scab mite Psoroptes cuniculi (Arthropoda: Arachnida) provides insights into Acari phylogeny | journal = Parasites & Vectors | volume = 7 | pages = 340 | date = July 2014 | pmid = 25052180 | pmc = 4223567 | doi = 10.1186/1756-3305-7-340 | doi-access = free }}</ref>

===Anatomy and physiology===
[[File:Amblyomma americanum tick.jpg|thumb|left|A hard-bodied tick of the family Ixodidae, [[Amblyomma americanum|the lone star tick]]]]

Ticks, like [[mites]], belong to the subclass Acari that lack their primary somatic segmentation of the [[Abdomen#Arthropoda|abdomen]] (or [[opisthosoma]]), rather these parasitic [[arachnid]]s present a subsequent fusion of the abdomen with the [[cephalothorax]] (or [[prosoma]]).<ref name=Ruppert/> The [[Tagma (biology)|tagmata]] typical of other [[Chelicerata]] have developed into the [[gnathosoma]] (head), which is retractable and contains the mouthparts, and idiosoma (body), which contains the legs, digestive tract, and reproductive organs.<ref name="Wall-55" /> The gnathosoma is a feeding structure with mouthparts adapted for piercing skin and sucking blood; it is the front of the head and contains neither the brain nor the eyes.<ref name=Ruppert>{{cite book |title=Invertebrate Zoology | edition = 7th | vauthors = Ruppert EE, Fox RS, Barnes RD |year=2004 |publisher=Cengage Learning |isbn=978-81-315-0104-7 |pages=590–595 }}</ref> Features of the gnathosoma include two [[palp]]s, two [[chelicera]]e, and [[hypostome]]. The hypostome acts as stabilizer and helps to anchor the tick's mouthparts to the host.<ref>{{cite journal | vauthors = Richter D, Matuschka FR, Spielman A, Mahadevan L | title = How ticks get under your skin: insertion mechanics of the feeding apparatus of Ixodes ricinus ticks | journal = Proceedings. Biological Sciences | volume = 280 | issue = 1773 | pages = 20131758 | date = December 2013 | pmid = 24174106 | pmc = 3826218 | doi = 10.1098/rspb.2013.1758 | issn = 0962-8452 }}</ref> The chelicerae are specialized appendages used for cutting and piercing into the host's skin while palps are leglike appendages that are sensory in function.

The ventral side of the idiosoma bears [[sclerite]]s, and the gonopore is located between the fourth pair of legs. In the absence of segmentation, the positioning of the eyes, limbs, and [[gonopore]] on the idiosoma provide the only locational guidance.<ref name=Ruppert/>

Larval ticks hatch with six legs, acquiring the other two after a blood meal and [[molting]] into the nymph stage.<ref name=illinois>{{cite web |title=Common Ticks |url=http://www.idph.state.il.us/envhealth/pccommonticks.htm |website=Illinois Department of Public Health |access-date=11 April 2014}}</ref> In the nymphal and adult stages, ticks have eight legs, each of which has seven segments and is tipped with a pair of claws. The legs are sometimes ornamented and usually bear sensory or tactile hairs.<ref name=CVBDlegs>{{cite web |url=http://www.cvbd.org/en/tick-borne-diseases/about-ticks/general-morphology/locomotion/ |title=Soft ticks |work=CVBD: Companion Vector-Borne Diseases |access-date=6 December 2016}}</ref> In addition to being used for [[Animal locomotion|locomotion]], the [[Arthropod leg#Tarsus|tarsus]] of leg I contains a unique sensory structure, [[Haller's organ]], which can detect odors and chemicals emanating from the host, as well as sensing changes in temperature and air currents.<ref name="Sonenshine-2005-p14" /><ref name="nicholson-486" /><ref>For Haller's organ, see also: [[#Mehlhorn|Mehlhorn (2008)]]: [https://books.google.com/books?id=Jpg1ysgVn-AC&pg=PA582 p. 582].</ref> Ticks can also use Haller's organs to perceive [[infrared]] light emanating from a host.<ref>{{cite journal | vauthors = Mitchell RD, Zhu J, Carr AL, Dhammi A, Cave G, Sonenshine DE, Roe RM | title = Infrared light detection by the haller's organ of adult american dog ticks, Dermacentor variabilis (Ixodida: Ixodidae) | journal = Ticks and Tick-Borne Diseases | volume = 8 | issue = 5 | pages = 764–771 | date = August 2017 | pmid = 28647127 | pmc = 5588665 | doi = 10.1016/j.ttbdis.2017.06.001 }}</ref>  When stationary, their legs remain tightly folded against the body.<ref name="Sonenshine-2005-p14">[[#Sonenshine|Sonenshine (2005)]]: [https://books.google.com/books?id=dKlUARLKT9IC&pg=PA14 p. 14]{{Dead link|date=March 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name="nicholson-486">[[#Nicholson|Nicholson et al. (2009)]]: [https://books.google.com/books?id=6R1v9o-uaI4C&pg=PA486 p. 486]</ref>

Ticks are extremely resilient animals. They can survive in a near vacuum for as long as half an hour.<ref>{{cite web|url=http://blogs.discovermagazine.com/notrocketscience/2012/03/15/tick-vacuum-electron-microscope/|title=Stuffed in a vacuum and bombarded by electrons, a tick waves hello|date=15 March 2012|vauthors=Yonge|publisher=Discover|access-date=1 May 2019|archive-date=1 May 2019|archive-url=https://web.archive.org/web/20190501045656/http://blogs.discovermagazine.com/notrocketscience/2012/03/15/tick-vacuum-electron-microscope/|url-status=dead}}</ref> Their slow metabolism during their [[diapause|dormant periods]] enables them to go prolonged durations between meals.<ref>{{cite web|url=https://www.uc.edu/news/articles/2018/11/n2048879.html|title=UC study: Hungry ticks work harder to find you|publisher=UC Cincinnati| vauthors = Miller M |date=20 November 2018}}</ref> Even after 18 weeks of starvation, they can endure repeated two-day bouts of dehydration followed by rehydration, but their survivability against dehydration drops rapidly after 36 weeks of starvation.<ref>{{cite journal | vauthors = Rosendale AJ, Dunlevy ME, Fieler AM, Farrow DW, Davies B, Benoit JB | title = Dehydration and starvation yield energetic consequences that affect survival of the American dog tick | journal = Journal of Insect Physiology | volume = 101 | pages = 39–46 | date = August 2017 | pmid = 28648807 | doi = 10.1016/j.jinsphys.2017.06.012 | doi-access = free | bibcode = 2017JInsP.101...39R }}</ref> To keep from dehydrating, ticks hide in humid spots on the forest floor<ref>{{cite web|url=https://www.outsideonline.com/1915071/rise-tick|title=The Rise of the Tick | vauthors = Zimmer C |publisher=Outside|date=30 April 2013}}</ref> or absorb water from subsaturated air by secreting [[Hygroscopy|hygroscopic]] fluid produced by the [[salivary gland]]s onto the external mouthparts and then reingesting the water-enriched fluid.<ref>{{cite journal | vauthors = Gray JS, Kahl O, Lane RS, Levin ML, Tsao JI | title = Diapause in ticks of the medically important Ixodes ricinus species complex | journal = Ticks and Tick-Borne Diseases | volume = 7 | issue = 5 | pages = 992–1003 | date = July 2016 | pmid = 27263092 | pmc = 5659180 | doi = 10.1016/j.ttbdis.2016.05.006 }}</ref>

Ticks can withstand temperatures just above {{convert|0|°F|°C|order=flip}} for more than two hours and can survive temperatures between {{convert|20 and 29|F|C|order=flip}} for at least two weeks. Ticks have even been found in Antarctica, where they feed on penguins.<ref>{{cite web|url=https://www.sciencedaily.com/releases/2017/09/170925133016.htm|title=Ticks are even tougher and nastier than you thought|date=25 September 2017|website=Science Daily}}</ref>

Most ticks are plain brown or reddish brown. However, the scuta of some species are decorated with white patterns.<ref>{{cite book|title=Laboratory Procedures for Veterinary Technicians| vauthors = Sirois M |publisher=Elsevier|year=2015|isbn=978-0-323-16930-1|location=St. Louis, MO}}</ref>

====Ixodidae====

In [[Nymph (biology)|nymphs]] and adults, the {{lang|la|capitulum}} is prominent and projects forwards from the body. The eyes are close to the sides of the scutum and the large [[Spiracle (arthropods)|spiracle]]s are located just behind the [[Arthropod leg|coxae]] of the fourth pair of legs.<ref name="Molyneux">[[#Molyneux|Molyneux (1993)]] [https://books.google.com/books?id=jj18axV3TTAC&pg=PA6 p. 6]</ref> The hard protective [[scutellum (insect anatomy)|scutellum]], a characteristic of this family, covers nearly the whole dorsal surface in males, but is restricted to a small, shield-like structure behind the capitulum in females and nymphs.<ref name="Walker">{{cite book | vauthors = Walker JB, Keirans JE, Horak IG |title=The Genus ''Rhipicephalus'' (Acari, Ixodidae): A Guide to the Brown Ticks of the World |url=https://books.google.com/books?id=M9fLCgAAQBAJ&pg=PA39 |year=2005 |publisher=Cambridge University Press |isbn=978-1-316-58374-6 |page=39}}</ref> When an ixodid attaches to a host the bite is typically painless and generally goes unnoticed. They remain in place until they engorge and are ready to [[Moulting|molt]]; this process may take days or weeks. Some species drop off the host to molt in a safe place, whereas others remain on the same host and only drop off once they are ready to lay their eggs.<ref name=Salman>{{cite book| vauthors = Salman MD, Tarrés-Call J, Estrada-Peña A |title=Ticks and Tick-borne Diseases: Geographical Distribution and Control Strategies in the Euro-Asia Region |url=https://books.google.com/books?id=mN4gCC81XHcC&pg=PA6 |year=2013 |publisher=CABI |isbn=978-1-84593-853-6 |pages=6–12}}</ref>[[File:Argas spec columbidae.jpg|thumb|A soft-bodied tick of the family Argasidae, beside eggs it has just laid]]

====Argasidae====

The body of a soft tick is pear-shaped or oval with a rounded anterior portion. The mouthparts cannot be seen from above, as they are on the ventral surface. A centrally positioned dorsal plate with ridges projecting slightly above the surrounding surface, but with no decoration is often present. Soft ticks possess a leathery [[cuticle]] as well. A pattern of small, circular depressions expose where muscles are attached to the interior of the [[integument]]. The eyes are on the sides of the body, the spiracles open between legs 3 and 4, and males and females only differ in the structure of the genital pore.<ref name="CVBDsoft">{{cite web |url=http://www.cvbd.org/en/tick-borne-diseases/about-ticks/general-morphology/soft-ticks/ |title=Soft ticks |work=CVBD: Companion Vector-Borne Diseases |access-date=6 December 2016|archive-url=https://web.archive.org/web/20190124004932/http://www.cvbd.org/en/tick-borne-diseases/about-ticks/general-morphology/soft-ticks/|archive-date=24 January 2019|url-status=live}}</ref>

====Nuttalliellidae====

Nuttalliellidae can be distinguished from both ixodid and argasid ticks by a combination of a projecting gnathosoma and a soft leathery skin. Other distinguishing characteristics include the position of the [https://web.archive.org/web/20181112221807/http://idtools.org/id/mites/invasive_mite/Invasive_Mite_Identification/key/Major_Mite_taxa/Media/Html/21_Peritremes.htm stigmata], the lack of setae, the strongly corrugated integument, and the form of the fenestrated plates.<ref>[[#Roshdy|Roshdy et al. (1983)]]</ref><ref>{{cite news |title=Long Lost Relative of Ticks Pops Up Again | vauthors = Brouwers L | url=http://blogs.scientificamerican.com/thoughtomics/a-long-lost-relative-of-ticks-pops-up-again/ |newspaper=Scientific American |date=30 August 2011 |access-date=4 December 2016}}</ref>

===Diet and feeding===
[[File:20140704-TickWaitingOnGrassBlade-CentralMA-USA.JPG|left|thumb|A questing tick, fingers for scale]]

Ticks are [[Parasitism#Types|ectoparasites]] and consume [[blood]] to satisfy all of their nutritional requirements. They are obligate [[hematophagy|hematophages]], and require blood to survive and move from one stage of life to another. Ticks can fast for long periods of time, but eventually die if unable to find a host.<ref name=cdcticklife >{{cite web |url=https://www.cdc.gov/ticks/life_cycle_and_hosts.html |title=Life cycle of Hard Ticks that Spread Disease |website=Centers for Disease Control and Prevention |access-date=22 June 2013}}</ref> Hematophagy evolved independently at least six times in arthropods living during the late [[Cretaceous]]; in ticks it is thought to have evolved 120 million years ago through adaptation to blood-feeding.<ref name="KlompenGrimaldi">{{cite journal |title=First Mesozoic Record of a Parasitiform Mite: a Larval Argasid Tick in Cretaceous Amber (Acari: Ixodida: Argasidae) |vauthors = Klompen H, Grimaldi D |journal=Annals of the Entomological Society of America |volume=94 |issue=1 |pages=10–15 |year=2001 |doi=10.1603/0013-8746(2001)094[0010:FMROAP]2.0.CO;2 |url=http://www.nhm.ac.uk/hosted_sites/acarology/saas/e-library/pdf000200/a000130.pdf?origin=publication_detail|doi-access=free }}</ref><ref name="Mans_2002">{{cite journal|vauthors=Mans BJ, Louw AI, Neitz AW|date=October 2002|title=Evolution of hematophagy in ticks: common origins for blood coagulation and platelet aggregation inhibitors from soft ticks of the genus Ornithodoros|journal=Molecular Biology and Evolution|volume=19|issue=10|pages=1695–705|doi=10.1093/oxfordjournals.molbev.a003992|issn=1537-1719|pmid=12270896|doi-access=free}}</ref> This behavior evolved independently within the separate tick families as well, with differing host-tick interactions driving the evolutionary change.<ref name="KlompenGrimaldi" />
 	
Some ticks attach to their host rapidly, while others wander around searching for thinner skin, such as that in the ears of mammals. Depending on the species and life stage, preparing to feed can take from ten minutes to two hours. On locating a suitable feeding spot, the tick grasps the host's skin and cuts into the surface.<ref name=cdcticklife /> It extracts blood by cutting a hole in the host's [[Epidermis (zoology)|epidermis]], into which it inserts its [[hypostome (tick)|hypostome]] and prevents the blood from clotting by excreting an [[anticoagulant]] or [[Platelet#Aggregation|platelet aggregation]] inhibitor.<ref>[[#Goddard|Goddard (2008)]]: [https://books.google.com/books?id=f-huycwyEvwC&pg=PA82 p. 82]</ref><ref name = "Mans_2002" />

Ticks find their hosts by detecting an animals' breath and body odors, sensing body heat, moisture, or vibrations.<ref name=CVBDhost/> A common misconception about ticks is they jump onto their host; however, they are incapable of jumping, although [[static electricity]] from their hosts has been shown to be capable of pulling the tick over distances several times their own body length.<ref>[https://www.cell.com/current-biology/fulltext/S0960-9822(23)00772-8 Static electricity passively attracts ticks onto hosts]</ref> Many tick species, particularly Ixodidae, lie in wait in a position known as "questing". While questing, ticks cling to leaves and grasses by their third and fourth pairs of legs. They hold the first pair of legs outstretched, waiting to grasp and climb on to any passing host. Tick questing heights tend to be correlated with the size of the desired host; nymphs and small species tend to quest close to the ground, where they may encounter small mammalian or bird hosts; adults climb higher into the vegetation, where larger hosts may be encountered. Some species are hunters and lurk near places where hosts may rest. Upon receiving an [[olfactory]] stimulus or other environmental indication, they crawl or run across the intervening surface.<ref name=CVBDhost>{{cite web |url=http://www.cvbd.org/en/tick-borne-diseases/about-ticks/tick-feeding/host-seeking/ |title=Host seeking |work=CVBD: Companion Vector-Borne Diseases |access-date=8 December 2016}}</ref>

Other ticks, mainly the Argasidae, are [[nidicolous]], finding hosts in their nests, burrows, or caves. They use the same stimuli as non-nidicolous species to identify hosts, with body heat and odors often being the main factors.<ref name=CVBDhost/> Many of them feed primarily on [[bird]]s, though some ''Ornithodoros'' species, for example, feed on small [[mammal]]s. Both groups of soft tick feed rapidly, typically biting painfully and drinking their fill within minutes. Unlike the Ixodidae that have no fixed dwelling place except on the host, they live in sand, in crevices near animal dens or nests, or in human dwellings, where they come out nightly to attack roosting birds or emerge when they detect [[carbon dioxide]] in the breath of their hosts.<ref name="SamuelPybus2001">[[#Allan|Allan (2001)]]</ref>

Ixodidae remain in place until they are completely engorged. Their weight may increase by 200 to 600 times compared to their prefeeding weight. To accommodate this expansion, cell division takes place to facilitate enlargement of the cuticle.<ref name=CVBDhard>{{cite web |url=http://www.cvbd.org/en/tick-borne-diseases/about-ticks/general-morphology/hard-ticks/ |title=Hard ticks |work=CVBD: Companion Vector-Borne Diseases |access-date=6 December 2016}}</ref> In the Argasidae, the tick's cuticle stretches to accommodate the fluid ingested, but does not grow new cells, with the weight of the tick increasing five- to tenfold over the unfed state. The tick then drops off the host and typically remains in the nest or burrow until its host returns to provide its next meal.<ref name=CVBDsoft />

Tick saliva contains about 1,500 to 3,000 proteins, depending on the tick species. The proteins with anti-inflammatory properties, called [[evasin]]s, allow ticks to feed for eight to ten days without being perceived by the host animal. Researchers are studying these evasins with the goal of developing drugs to neutralise the chemokines that cause [[myocarditis]], heart attack, and stroke.<ref>{{cite web|url=https://phys.org/news/2017-06-bug-drugtick-saliva-key-heart.html|title=From bug to drug—tick saliva could be key to treating heart disease|date=27 June 2017|publisher=Phys.org|author=University of Oxford}}</ref>
The saliva of ticks also contains [[anticoagulant]] and [[antiplatelet|antiplatelet]] proteins (integrin inhibitors), to stop the blood from coagulating while they suck.<ref>{{Cite journal |last1=van den Kerkhof |first1=Danique L. |last2=van der Meijden |first2=Paola E. J. |last3=Hackeng |first3=Tilman M. |last4=Dijkgraaf |first4=Ingrid |date=2021-03-25 |title=Exogenous Integrin αIIbβ3 Inhibitors Revisited: Past, Present and Future Applications |journal=International Journal of Molecular Sciences |volume=22 |issue=7 |pages=3366 |doi=10.3390/ijms22073366 |doi-access=free |issn=1422-0067 |pmc=8036306 |pmid=33806083}}</ref>

[[File:Oocysts of ticks and their endosymbionts.jpg|thumb|Mature oocysts of the seabird soft tick ''Ornithodoros maritimus'' and their ''Coxiella'' endosymbionts (labelled in yellow).]]
Ticks do not use any other food source than vertebrate blood and therefore  ingest high levels of protein, iron and salt, but few carbohydrates, lipids or vitamins.<ref name="tickconv">{{cite journal | vauthors = Duron O, Gottlieb Y | title = Convergence of Nutritional Symbioses in Obligate Blood Feeders | journal = Trends in Parasitology | volume = 36 | issue = 10 | pages = 816–825 | date = October 2020 | pmid = 32811753 | doi = 10.1016/j.pt.2020.07.007 | s2cid = 221181791 | url = https://hal.archives-ouvertes.fr/hal-03000781/file/Duron%20%26%20Gottlieb%20TIP%20May11_edited_revised.pdf }}</ref> Ticks’ genomes have evolved large repertoires of genes related to this nutritional challenge, but they themselves cannot synthesize the essential vitamins that are lacking in blood meal. To overcome these nutritional deficiencies, ticks have evolved obligate interactions with nutritional [[endosymbionts]].<ref name="tickconv" /> The first appearance of ticks and their later diversification were largely conditioned by this nutritional endosymbiosis lasting for millions of years. The most common of these nutritional endosymbionts belong to the ''Coxiella'' and ''Francisella'' bacterial genera.<ref>{{cite journal | vauthors = Binetruy F, Buysse M, Lejarre Q, Barosi R, Villa M, Rahola N, Paupy C, Ayala D, Duron O | title = Microbial community structure reveals instability of nutritional symbiosis during the evolutionary radiation of Amblyomma ticks | journal = Molecular Ecology | volume = 29 | issue = 5 | pages = 1016–1029 | date = March 2020 | pmid = 32034827 | doi = 10.1111/mec.15373 | bibcode = 2020MolEc..29.1016B | s2cid = 211065648 | url = https://hal.archives-ouvertes.fr/hal-03001756/file/MS-Binetruy_15-01-Revised%20version.pdf }}</ref><ref name="Duron_2017">{{cite journal | vauthors = Duron O, Binetruy F, Noël V, Cremaschi J, McCoy KD, Arnathau C, Plantard O, Goolsby J, Pérez de León AA, Heylen DJ, Van Oosten AR, Gottlieb Y, Baneth G, Guglielmone AA, Estrada-Peña A, Opara MN, Zenner L, Vavre F, Chevillon C | title = Evolutionary changes in symbiont community structure in ticks | journal = Molecular Ecology | volume = 26 | issue = 11 | pages = 2905–2921 | date = June 2017 | pmid = 28281305 | doi = 10.1111/mec.14094 | bibcode = 2017MolEc..26.2905D | hdl = 10067/1422810151162165141 | s2cid = 40962020 | url = https://hal.inria.fr/hal-01523998/file/Duron_et_al-2017-Molecular_Ecology.pdf | hdl-access = free }}</ref> These intracellular symbiotic microorganisms are specifically associated with ticks and use [[transovarial transmission]] to ensure their persistence.<ref>{{cite journal | vauthors = Buysse M, Plantard O, McCoy KD, Duron O, Menard C | title = Tissue localization of Coxiella-like endosymbionts in three European tick species through fluorescence in situ hybridization | journal = Ticks and Tick-Borne Diseases | volume = 10 | issue = 4 | pages = 798–804 | date = June 2019 | pmid = 30922601 | doi = 10.1016/j.ttbdis.2019.03.014 | url = https://hal.archives-ouvertes.fr/hal-03012100/file/Buysse.pdf | doi-access = free }}</ref><ref name="Duron_2018">{{cite journal | vauthors = Duron O, Morel O, Noël V, Buysse M, Binetruy F, Lancelot R, Loire E, Ménard C, Bouchez O, Vavre F, Vial L | title = Tick-Bacteria Mutualism Depends on B Vitamin Synthesis Pathways | journal = Current Biology | volume = 28 | issue = 12 | pages = 1896–1902.e5 | date = June 2018 | pmid = 29861133 | doi = 10.1016/j.cub.2018.04.038 | s2cid = 44095809 | doi-access = free | bibcode = 2018CBio...28E1896D }}</ref><ref name="Lalzar_2014">{{cite journal | vauthors = Lalzar I, Friedmann Y, Gottlieb Y | title = Tissue tropism and vertical transmission of Coxiella in Rhipicephalus sanguineus and Rhipicephalus turanicus ticks | journal = Environmental Microbiology | volume = 16 | issue = 12 | pages = 3657–68 | date = December 2014 | pmid = 24650112 | doi = 10.1111/1462-2920.12455 | bibcode = 2014EnvMi..16.3657L | issn = 1462-2920 }}</ref> Although ''Coxiella'' and ''Francisella'' endosymbionts are distantly related bacteria, they have converged towards an analogous B vitamin-based nutritional mutualism with ticks.<ref name="tickconv" /> Their experimental elimination typically results in decreased tick survival, molting, fecundity and egg viability, as well as in physical abnormalities, which all are fully restored with an oral supplement of B vitamins.<ref name="Duron_2018" /><ref name="Guizzo_2017">{{cite journal | vauthors = Guizzo MG, Parizi LF, Nunes RD, Schama R, Albano RM, Tirloni L, Oldiges DP, Vieira RP, Oliveira WH, Leite MS, Gonzales SA, Farber M, Martins O, Vaz ID, Oliveira PL | title = A Coxiella mutualist symbiont is essential to the development of Rhipicephalus microplus | journal = Scientific Reports | volume = 7 | issue = 1 | pages = 17554 | date = December 2017 | pmid = 29242567 | pmc = 5730597 | doi = 10.1038/s41598-017-17309-x | bibcode = 2017NatSR...717554G | issn = 2045-2322 }}</ref><ref>{{cite journal | vauthors = Ben-Yosef M, Rot A, Mahagna M, Kapri E, Behar A, Gottlieb Y | title = Rhipicephalus sanguineus Is Required for Physiological Processes During Ontogeny | journal = Frontiers in Microbiology | volume = 11 | pages = 493 | date = 2020-04-22 | pmid = 32390951 | pmc = 7188774 | doi = 10.3389/fmicb.2020.00493 | issn = 1664-302X | doi-access = free }}</ref> The genome sequencing of ''Coxiella'' and ''Francisella'' endosymbionts confirmed that they consistently produce three B vitamin types, biotin (vitamin B<sub>7</sub>), riboflavin (B<sub>2</sub>) and folate (B<sub>9</sub>).<ref name="Duron_2018" /><ref name="Guizzo_2017" /><ref>{{cite journal | vauthors = Smith TA, Driscoll T, Gillespie JJ, Raghavan R | title = A Coxiella-like endosymbiont is a potential vitamin source for the Lone Star tick | journal = Genome Biology and Evolution | volume = 7 | issue = 3 | pages = 831–8 | date = January 2015 | pmid = 25618142 | pmc = 4994718 | doi = 10.1093/gbe/evv016 }}</ref> As they are required for tick life cycle, these obligate endosymbionts are present in all individuals of the tick species they infect, at least at early stages of development since they may be secondarily lost in males during nymphal development.<ref name="Duron_2017" /><ref name="Duron_2018" /><ref name="Lalzar_2014" /> Since ''Coxiella'' and ''Francisella'' endosymbionts are closely related to pathogens, there is a substantial risk of misidentification between endosymbionts and pathogens, leading to an overestimation of infection risks associated with ticks.<ref>{{cite journal | vauthors = Duron O, Sidi-Boumedine K, Rousset E, Moutailler S, Jourdain E | title = The Importance of Ticks in Q Fever Transmission: What Has (and Has Not) Been Demonstrated? | journal = Trends in Parasitology | volume = 31 | issue = 11 | pages = 536–552 | date = November 2015 | pmid = 26458781 | doi = 10.1016/j.pt.2015.06.014 | s2cid = 25636125 | issn = 1471-4922| url = https://hal.inrae.fr/hal-02637724/file/1-s2.0-S1471492215001518-main.pdf }}</ref><ref>{{cite journal | vauthors = Duron O | title = The IS1111 insertion sequence used for detection of Coxiella burnetii is widespread in Coxiella-like endosymbionts of ticks | journal = FEMS Microbiology Letters | volume = 362 | issue = 17 | pages = fnv132 | date = September 2015 | pmid = 26269380 | doi = 10.1093/femsle/fnv132 | issn = 0378-1097 | doi-access = free }}</ref>

===Range and habitat===
Tick species are widely distributed around the world.<ref>[[#Magnarelli|Magnarelli (2009)]]</ref> They tend to flourish more in warm, humid climates, because they require a certain amount of moisture in the air to undergo [[metamorphosis]], and low temperatures inhibit their development of eggs to larvae.<ref name="London1905">[[#Nuttall|Nuttall (1905)]]</ref> 
The occurrence of ticks and tick-borne illnesses in humans is increasing.<ref name="CDC">{{cite web |title=Lyme and Other Tickborne Diseases Increasing |url=https://www.cdc.gov/ncezid/dvbd/media/lyme-tickborne-diseases-increasing.html |website=Centers for Disease Control |access-date=4 March 2022 |language=en-us |date=21 October 2021}}</ref> Tick populations are spreading into new areas, due in part to the warming temperatures of [[climate change]].<ref name="Chrobak"/><ref name="Gilbert">{{cite journal |last1=Gilbert |first1=Lucy |title=The Impacts of Climate Change on Ticks and Tick-Borne Disease Risk |journal=Annual Review of Entomology |date=7 January 2021 |volume=66 |issue=1 |pages=373–388 |doi=10.1146/annurev-ento-052720-094533 |pmid=33417823 |s2cid=231300522 |issn=0066-4170|doi-access=free }}</ref>

Tick parasitism is widely distributed among host taxa, including marsupial and placental mammals, birds, reptiles (snakes, iguanas, and lizards), and amphibians.<ref>{{cite journal | vauthors = Dantas-Torres F, Oliveira-Filho EF, Soares FA, Souza BO, Valença RB, Sá FB | title = Ticks infesting amphibians and reptiles in Pernambuco, Northeastern Brazil | journal = Revista Brasileira de Parasitologia Veterinaria | volume = 17 | issue = 4 | pages = 218–21 | date = 2008 | pmid = 19265581 | doi = 10.1590/S1984-29612008000400009 | doi-access = free }}</ref> [[Ticks of domestic animals]] cause considerable harm to livestock through pathogenic transmission, causing anemia through blood loss, and damaging wool and hides.<ref>{{cite web |url=http://www.butox-info.com/ectoparasites/ticks.asp |title=Ticks of Livestock |work=Ectoparasites of Livestock |publisher=Butox |access-date=14 January 2017 |archive-date=16 January 2017 |archive-url=https://web.archive.org/web/20170116162859/http://www.butox-info.com/ectoparasites/ticks.asp |url-status=dead }}</ref> The [[Amblyomma variegatum|Tropical Bont tick]] wreaks havoc on livestock and wildlife in Africa, the Caribbean, and several other countries through the spread of disease, specifically [[Ehrlichia ruminantium|heartwater]] disease.<ref>{{cite web|title=tropical bont tick - Amblyomma variegatum|url=http://entnemdept.ufl.edu/Creatures/livestock/ticks/tropical_bont_tick.htm|access-date=2020-11-29|website=entnemdept.ufl.edu}}</ref> The [[Otobius megnini|spinose ear tick]] has a worldwide distribution, the young feed inside the ears of cattle and various wildlife.<ref name="Texas">{{cite web |url=http://livestockvetento.tamu.edu/insectspests/ticks/ |title=Ticks |work=Livestock Veterinary Entomology |publisher=Texas A&M AgriLife |access-date=14 January 2017}}</ref>

A habitat preferred by ticks is the interface where a lawn meets the forest,<ref>{{cite web|url=https://www.npr.org/sections/health-shots/2016/07/20/486635116/taking-the-battle-against-lyme-disease-ticks-to-the-backyard|title=Taking The Battle Against Lyme Disease Ticks To The Backyard| vauthors = Beans C |date=20 July 2016|publisher=NPR}}</ref> or more generally, the [[ecotone]], which is unmaintained transitional edge habitat between woodlands and open areas. Therefore, one tick management strategy is to remove leaf litter, brush, and weeds at the edge of the woods.<ref>{{cite web|url=http://www.millis.org/Pages/MillisMA_BComm/Boh/Tick%20Management.PDF|title=Integrated Tick Management|publisher=Connecticut Agricultural Experimental Station|access-date=2 May 2019|archive-date=4 December 2022|archive-url=https://web.archive.org/web/20221204060757/http://www.millis.org/Pages/MillisMA_BComm/Boh/Tick%20Management.PDF|url-status=dead}}</ref> Ticks like shady, moist leaf litter with an overstory of trees or shrubs and, in the spring, they deposit their eggs into such places allowing larvae to emerge in the fall and crawl into low-lying vegetation. The 3 meter boundary closest to the lawn's edge are a tick migration zone, where 82% of tick nymphs in lawns are found.<ref name="dirt" />

=== Ecology ===
In general, ticks are found wherever their host species occur. Migrating birds carry ticks with them on through their migrations; a study of migratory birds passing through Egypt discovered more than half the bird species examined were carrying ticks. It was also observed the tick species varied depending on the season of migration, in this study it is spring and autumn migrations, this is thought to occur due to the seasonal periodicities of the different species.<ref name="Hoogstraal">{{cite journal | vauthors = Hoogstraal H, Kaiser MN, Traylor MA, Guindy E, Gaber S | title = Ticks (Ixodidae) on birds migrating from Europe and Asia to Africa 1959-61 | journal = Bulletin of the World Health Organization | volume = 28 | issue = 2 | pages = 235–62 | year = 1963 | pmid = 13961632 | pmc = 2554471 }}</ref>

For an ecosystem to support ticks, it must satisfy two requirements; the population density of host species in the area must be great enough and it must be humid enough for ticks to remain hydrated.<ref name="Wall-55">[[#Wall|Wall & Shearer (2001)]]: [https://books.google.com/books?id=AMljlwB0ej0C&pg=PA55 p. 55]</ref> Due to their role in transmitting [[Lyme disease]], Ixodid ticks, particularly the North American [[Ixodes scapularis|''I.&nbsp;scapularis'']], have been studied using [[geographic information system]]s to develop predictive models for ideal tick habitats. According to these studies, certain features of a given microclimate – such as sandy soil, hardwood trees, rivers, and the presence of deer – were determined to be good predictors of dense tick populations.<ref name="SamuelPybus2001" />

Mites and nematodes feed on ticks, which are also a minor nutritional resource for birds. More importantly, ticks act as a disease vector and behave as the primary hosts of many different [[pathogen]]s such as [[spirochaete]]s. Ticks carry various debilitating diseases therefore, ticks may assist in controlling animal populations and preventing overgrazing.<ref>{{cite news |title=The mighty tick | vauthors = Ray CC |url=https://www.nytimes.com/2012/05/29/science/would-eradicating-deer-ticks-hurt-the-ecosystem.html?_r=0 |newspaper=New York Times |date=28 May 2012 |access-date=15 December 2016}}</ref>

Ticks can transmit an array of infectious diseases that affect humans and other animals.<ref name="Australia">{{cite journal | year=2005 | volume=26 | issue=2 | first3=Elizabeth | first1=Marie | first2=Julie | last3=Deane | page=76 | issn=1324-4272 | journal=[[Microbiology Australia]] | publisher=[[CSIRO Publishing]] | last1=Vilcins | last2=Old | s2cid=81977091 | doi=10.1071/ma05076 | title=The impact of ticks and tick-borne diseases on native animal species in Australia| doi-broken-date=23 March 2025 | doi-access=free }}</ref> Ticks that carry [[Zoonosis|zoonotic]]  pathogens often tend to have a wide host range. The infective agents can be present not only in the adult tick, but also in the eggs produced plentifully by the females. Many tick species have extended their ranges as a result of the movements of people, domesticated pets, and [[livestock]]. With increasing participation in outdoor activities such as [[hiking|wilderness hikes]], more people and their dogs may find themselves exposed to ticks.<ref name="CVBDtransmission">{{cite web |url=http://www.cvbd.org/en/tick-borne-diseases/disease-transmission/ |title=Disease transmission |work=CVBD: Companion Vector-Borne Diseases |access-date=9 December 2016}}</ref>

===Life cycle===
[[File:Life-cycle-of-ixodid-tick.jpg|thumb|Life-cycle of an ixodid tick ([[Rhipicephalus appendiculatus]], all to same scale); E=eggs, L=larvae, N=nymphs, F=adult female, M=adult male; upper row are unfed ticks, lower row are fully engorged larvae, nymphs, and a female.]]
[[File:Klopa med parjenjem-fotoBlazVerbic.jpg|thumb|Two ticks mating. The smaller tick is the adult male.  The larger is the adult female, who is engorged after feeding.]]
All three tick families ticks have four life cycle stages: egg, [[larva]], [[Nymph (biology)|nymph]], and adult.<ref>[[#Dennis|Dennis & Piesman (2005)]]: [https://books.google.com/books?id=dKlUARLKT9IC&pg=PA5 p. 5]{{Dead link|date=March 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

====Ixodidae====
{{main|Ixodidae}}
Ixodidae ticks have three different life cycles. Depending on the species, Ixodids can either possess a one-host life cycle, two-host life cycle, or three-host life cycle.

===== One-host ticks =====
In one-host ticks the tick remains on the host through the larval, nymphal, and adult stages, only to leave the host to lay eggs. Eggs laid in the environment hatch into larvae, which immediately seek out a host in which to attach and feed. Fed larvae molt into unfed nymphs that remain on the host. After engorging on the host's blood, the nymphs molt into sexually mature adults that remain on the host in order to feed and mate. Once a female is both fed and ready to lay eggs, only then does she leave the host in search of a suitable area to deposit her eggs. Ticks that follow this life cycle are called one-host ticks. The winter tick ''Dermacentor albipictus'' and the cattle tick ''Boophilus microplus'' are examples of one-host ticks.<ref name="Sonenshine_1991">{{cite book | vauthors = Sonenshine D | date = 1991| title = Biology of Ticks | publisher = Oxford University Press | location = New York }}</ref>

===== Two-host ticks =====
The life cycle of a two-host tick often spans two years.<ref name="CDC - DPDx - Ticks"/> During fall the pregnant female tick will drop off her second host and lay her eggs. The eggs hatch during winter, the following spring the larvae emerge and attach to their first host. Newly hatched larvae attach to a host in order to obtain a blood meal. They remain on the host then develop into nymphs. Once engorged, they drop off the host and find a safe area in the natural environment in which to molt into adults, this typically occurs during the winter. Both male and female adults seek out a host on which to attach, which may be the same body that served as host during their early development but is often a larger mammal. Once attached, they feed and mate. [[mwod:gravid|Gravid]] females drop from the host to [[Oviparity|oviposit]] in the environment. Ticks that complete their life cycle in this manner are called two-host ticks, like ''Hyalomma anatolicum excavatum''.<ref name="Sonenshine_1991" />

===== Three-host ticks =====
Most ixodid ticks require three hosts, and their life cycles typically span three years. The female tick drops off its host, often in the fall, and lays thousands of eggs.<ref name="CDC - DPDx - Ticks"/> The larvae hatch in the winter and emerge in the spring. When the larvae emerge, they attach and feed primarily on small mammals and birds. During the summer the larvae become engorged and drop off the first host to molt and become nymphs, this often occurs during the fall. The following spring the nymphs emerge and seek out another host, often a small rodent. The nymphs become engorged and drop off the host in the fall to molt and become adults. The following spring the adult ticks emerge and seek out a larger host, often a large mammal such as cattle or even humans.  Females will mate on their third host. Female adults then engorge on blood and prepare to drop off to lay her eggs on the ground, while males feed very little and remain on the host in order to continue mating with other females.<ref name="SamuelPybus2001" /><ref name="Sonenshine_1991" />

====Argasidae====
{{main|Argasidae}}

Argasid ticks, unlike ixodid ticks, may go through up to seven nymphal stages (instars), requiring a meal of blood each time.<ref name="Aeschlimann-182">[[#Aeschlimann|Aeschlimann & Freyvogel, 1995]]: [https://books.google.com/books?id=YwJF6qzhrbkC&pg=PA177 p. 182]</ref> Often, egg laying and mating occurs detached from the host in a safe environment.<ref name="CDC - DPDx - Ticks"/> The eggs hatch and the larvae feed on a nearby host for anywhere from a few hours to several days, this depends on the species of tick. After they feed the larvae drop and molt into their first nymphal instars, then the nymph seeks out and feeds on its second host, often this is the same as the first host, within an hour. This process occurs repeatedly and until the last nymphal instar occurs, thus allowing the tick to molt into an adult. Once an adult these ticks feed rapidly and periodically their entire life cycle. In some species an adult female may lay eggs after each feeding. Their life cycles range from months to years. The adult female argasid tick can lay a few hundred to over a thousand eggs over the course of her lifetime. Both male and female adults feed on blood, and they mate off the host. During feeding, any excess fluid is excreted by the coxal glands, a process that is unique to argasid ticks.<ref name="SamuelPybus2001"/>

====Nuttalliellidae====
{{Main|Nuttalliella}}

Nuttalliellidae is an elusive monotypic family of tick, that is, possesses a single species, ''Nuttalliella namaqua''. There is little to nothing known about the life cycle and feeding habits of ''N. namaqua'' but it is speculated this species of tick has multiple different hosts.<ref>{{cite journal | vauthors = Mans BJ, de Klerk D, Pienaar R, Latif AA | title = Nuttalliella namaqua: a living fossil and closest relative to the ancestral tick lineage: implications for the evolution of blood-feeding in ticks | journal = PLOS ONE | volume = 6 | issue = 8 | pages = e23675 | date = 2011-08-17 | pmid = 21858204 | pmc = 3157464 | doi = 10.1371/journal.pone.0023675 | bibcode = 2011PLoSO...623675M | issn = 1932-6203 | doi-access = free }}</ref>