Editing Parasitoid

{{Use British English|date=January 2017}}
{{good article}}
{{short description|Organism that lives with its host and kills it}}
[[File:CSIRO ScienceImage 2357 Spotted alfalfa aphid being attacked by parasitic wasp.jpg|thumb|upright=1.2|A [[parasitoid wasp]] (''Trioxys complanatus'', [[Aphidiinae]]) [[ovipositing]] into the body of a spotted alfalfa [[aphid]] (''Therioaphis maculata'', [[Calaphidinae]]), a behaviour that is used in [[biological pest control]]{{efn|The species has been introduced to Australia to control the spotted alfalfa aphid.<ref name="WilsonSwincer1982">{{cite journal |last1=Wilson |first1=C. G. |last2=Swincer |first2=D. E. |last3=Walden |first3=K. J. |title=The introduction of ''Trioxys complanatus'' Quilis (Hymenoptera: Aphidiidae), an internal parasite of the Spotted Alfalfa Aphid, into South Australia |journal=Australian Journal of Entomology |volume=21 |issue=1 |year=1982 |pages=13–27 |doi=10.1111/j.1440-6055.1982.tb01758.x|s2cid=84996305 }}</ref>}}<ref>{{Cite web |title=Spotted Alfalfa Aphid / Alfalfa / Agriculture: Pest Management Guidelines / UC Statewide IPM Program (UC IPM) |url=https://ipm.ucanr.edu/agriculture/alfalfa/spotted-alfalfa-aphid/ |access-date=2023-09-22 |website=ipm.ucanr.edu}}</ref>]]

In [[evolutionary ecology]], a '''parasitoid''' is an [[organism]] that lives in close association with its [[host (biology)|host]] at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major [[evolutionarily stable strategy|evolutionary strategies]] within [[parasitism]], distinguished by the fatal [[prognosis]] for the host, which makes the strategy close to [[predation]].

Among parasitoids, strategies range from living inside the host (''endoparasitism''), allowing it to continue growing before emerging as an adult, to [[Paralysis|paralysing]] the host and living outside it (''ectoparasitism''). Hosts can include other parasitoids, resulting in [[hyperparasitism]]; in the case of [[oak gall]]s, up to five levels of parasitism are possible. Some parasitoids [[Behavior-altering parasite|influence their host's behaviour]] in ways that favour the propagation of the parasitoid.

Parasitoids are found in a variety of [[Taxon|taxa]] across the [[insect]] superorder [[Endopterygota]], whose complete [[metamorphosis]] may have [[pre-adapted]] them for a split lifestyle, with parasitoid [[Larva|larvae]] and free-living adults. Most are in the [[Hymenoptera]], where the [[Ichneumonidae|ichneumons]] and many other [[parasitoid wasp]]s are highly specialised for a parasitoidal way of life. There are parasitoids, too, in the [[Diptera]], [[Coleoptera]] and other [[Order (biology)|order]]s of [[endopterygota|endopterygote insects]]. Some of these, usually but not only wasps, are used in [[biological pest control]]. 

The 17th-century zoological artist [[Maria Sibylla Merian]] closely observed parasitoids and their hosts in her paintings. The biology of parasitoidism influenced [[Charles Darwin]]'s beliefs and has inspired [[science fiction]] authors and [[scriptwriter]]s to create numerous parasitoidal aliens that kill their human hosts, such as the [[Alien (creature in Alien franchise)|alien species]] in [[Ridley Scott]]'s 1979 film ''[[Alien (film)|Alien]]''.

==Etymology==

The term "parasitoid" was coined in 1913 by the [[Swedish-speaking population of Finland|Swedo-Finnish]] writer [[Odo Reuter]],<ref>{{cite book |author=Reuter, Odo M. |author-link=Odo Reuter |year=1913 |title=Lebensgewohnheiten und Instinkte der Insekten |trans-title=Habits and instincts of the insects up to the awakening of social instincts |publisher=R. Friedländer und Sohn |language=de}}</ref> and adopted in English by his reviewer,<ref name="Wheeler 1914">{{cite journal | last=Wheeler | first=William Morton | title=Scientific Books {{!}} Lebensgewohnheiten und Instinkte der Insekten bis zum Erwachen der sozialen Instinkte | journal=Science | publisher=American Association for the Advancement of Science (AAAS) | volume=39 | issue=993 | date=9 January 1914 | doi=10.1126/science.39.993.69 | pages=69–71}}</ref> the entomologist [[William Morton Wheeler]].<ref>{{cite book |author=Wheeler, William Morton |author-link=William Morton Wheeler |title=Social life among the insects: being a series of lectures delivered at the Lowell Institute in Boston in March 1922 |publisher=Harcourt, Brace |year=1923 |url=https://archive.org/details/sociallifeamongi00whee}} Previously published in ''Scientific Monthly'', June 1922 to February 1923.</ref> Reuter used it to describe the strategy where the parasite develops in or on the body of a single host individual, eventually killing that host, while the adult is free-living. Since that time, the concept has been generalised and widely applied.<ref name=Godfray1994>{{cite book |last=Godfray |first=H. C. J. |title=Parasitoids: Behavioral and Evolutionary Ecology |url=https://archive.org/details/parasitoidsbehav0000godf |url-access=registration |date=1994 |publisher=Princeton University Press |isbn=978-0-691-00047-3}}</ref>

==Strategies==

===Evolutionary options===

A perspective on the evolutionary options can be gained by considering four questions: the effect on the [[Fitness (biology)|reproductive fitness]] of a parasite's hosts; the number of hosts they have per life stage; whether the host is prevented from reproducing; and whether the effect depends on intensity (number of parasites per host). From this analysis, proposed by K. D. Lafferty and A. M. Kunis, the major evolutionary strategies of parasitism emerge, alongside predation.<ref name=LaffertyKuris2002>{{cite journal |last1=Lafferty |first1=K. D. |last2=Kuris |first2=A. M. |date=2002 |title=Trophic strategies, animal diversity and body size |journal=Trends Ecol. Evol. |volume=17 |issue=11 |pages=507–513 |doi=10.1016/s0169-5347(02)02615-0}}</ref>

{| class="wikitable"
|+ Evolutionary strategies in parasitism and predation<ref name=LaffertyKuris2002/><br/>({{font color|green|intensity-dependent: green, roman}}<!--colour is used redundantly alongside position (above/below), indentation and font-->;<br/>&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;''{{font color|purple |intensity-independent: purple, italics}}'')
! Host fitness !! Single host, stays alive !! Single host, dies !! Multiple hosts
|-
| '''Able to<br/>reproduce<br/>(fitness > 0)''' || {{font color|green|Conventional parasite}}<br/>&nbsp;&nbsp;&nbsp;''{{font color|purple |Pathogen}}'' || {{font color|green|Trophically transmitted parasite}}{{efn|Trophically transmitted parasites are transmitted to their definitive host, a predator, when their intermediate host is eaten. These parasites often modify the behaviour of their intermediate hosts, causing them to behave in a way that makes them likely to be eaten, such as by climbing to a conspicuous point: this gets the parasites transmitted at the cost of the intermediate host's life.}}<br/>&nbsp;&nbsp;&nbsp;''{{font color|purple |Trophically transmitted pathogen}}'' || {{font color|green|Micropredator}}<br/>&nbsp;&nbsp;&nbsp;''{{font color|purple |Micropredator}}''
|-
| '''Unable to<br/>reproduce<br/>(fitness = 0)''' || {{font color|green| &mdash; }}<br/>&nbsp;&nbsp;&nbsp;''{{font color|purple |Parasitic castrator}}'' || {{font color|green|Trophically transmitted parasitic castrator}}<br/>&nbsp;&nbsp;&nbsp;''{{font color|purple | Parasitoid}}'' || {{font color|green|Social predator}}{{efn|The [[wolf]] is a social predator, hunting in packs; the [[cheetah]] is a solitary predator, hunting alone. Neither strategy is conventionally considered parasitic.}}<br/>&nbsp;&nbsp;&nbsp;''{{font color|purple |Solitary predator}}''
|}

Parasitoidism, in the view of [[Robert Poulin (zoologist)|R. Poulin]] and H. S. Randhawa, is one of six main [[evolutionary strategies]] within [[parasitism]], the others being [[parasitic castrator]], directly transmitted parasite, [[wikt:trophic|trophically]] transmitted parasite, [[vector (epidemiology)|vector]]-transmitted parasite, and micropredator. These are [[adaptive peaks]], with many possible intermediate strategies, but organisms in many different groups have consistently [[convergent evolution|converged]] on these six.<ref name=PoulinRandhawa2015>{{cite journal |last1=Poulin |first1=Robert |author1-link=Robert Poulin (zoologist) |last2=Randhawa |first2=Haseeb S. |title=Evolution of parasitism along convergent lines: from ecology to genomics |journal=Parasitology |date=February 2015 |volume=142 |issue=Supplement 1 |pages=S6–S15 |doi=10.1017/S0031182013001674 |pmc=4413784 |pmid=24229807}}</ref><ref name=Rollinson>{{cite book |author=Poulin, Robert |author-link=Robert Poulin (zoologist) |editor1=Rollinson, D. |editor2=Hay, S. I. |title=The Many Roads to Parasitism: A Tale of Convergence |journal=Advances in Parasitology |url=https://books.google.com/books?id=9y4AlXka7t0C&pg=PA28 |year=2011 |volume=74 |publisher=Academic Press |isbn=978-0-12-385897-9 |pages=27–28|doi=10.1016/B978-0-12-385897-9.00001-X |pmid=21295676 }}</ref>

Parasitoids feed on a living host which they eventually kill, typically before it can produce offspring, whereas conventional parasites usually do not kill their hosts, and predators typically kill their prey immediately.<ref name=Stevens2010>{{cite journal |last1=Stevens |first1=Alison N. P. |title=Predation, Herbivory, and Parasitism |journal=Nature Education Knowledge |date=2010 |volume=3 |issue=10 |page=36 |url=https://www.nature.com/scitable/knowledge/library/predation-herbivory-and-parasitism-13261134 |access-date=12 February 2018 |quote=Predation, herbivory, and parasitism exist along a continuum of severity in terms of the extent to which they negatively affect an organism's fitness. ... In most situations, parasites do not kill their hosts. An exception, however, occurs with parasitoids, which blur the line between parasitism and predation.}}</ref><ref>{{cite journal |last1=Møller |first1=A. P. |year=1990 |title=Effects of parasitism by a haematophagous mite on reproduction in the barn swallow |jstor=1938645 |journal=Ecology |volume=71 |issue=6 |pages=2345–2357 |doi=10.2307/1938645|bibcode=1990Ecol...71.2345M }}</ref>

<!--if reorganising, ensure anchors remain with following text-->
{{anchor|Koinobiont}}
{{anchor|Idiobiont}}

===Basic concepts===
[[File:Pteromalid hyperparasitoid.jpg|thumb|upright|A [[hyperparasitoid]] [[chalcid wasp|chalcidoid wasp]] on the cocoons of its host, a [[braconid wasp]], itself a koinobiont parasitoid of [[Lepidoptera]]]]

Parasitoids can be classified as either endo- or ectoparasitoids with '''idiobiont''' or '''koinobiont''' developmental strategies. Endoparasitoids live within their host's body, while ectoparasitoids feed on the host from outside. Idiobiont parasitoids prevent further development of the host after initially immobilising it, whereas koinobiont parasitoids allow the host to continue its development while feeding upon it. Most ectoparasitoids are idiobiont, as the host could damage or dislodge the external parasitoid if allowed to move and [[moult]]. Most endoparasitoids are koinobionts, giving them the advantage of a host that continues to grow larger and avoid predators.<ref name=GullanCranston2010>{{cite book |author1=Gullan, P. J. |author2=Cranston, P. S. |date=2014 |title=The Insects: An Outline of Entomology |publisher=Wiley |edition=5th |isbn=978-1-118-84615-5 |pages=362–370}}</ref>

Primary parasitoids have the simplest parasitic relationship, involving two organisms, the host and the parasitoid. [[Hyperparasitoid]]s are parasitoids of parasitoids; secondary parasitoids have a primary parasitoid as their host, so there are three organisms involved. Hyperparasitoids are either facultative (can be a primary parasitoid or a hyperparasitoid depending on the situation) or obligate (always develop as a hyperparasitoid). Levels of parasitoids beyond secondary also occur, especially among facultative parasitoids. In [[oak gall]] systems, there can be up to five levels of parasitism.<ref>{{cite journal |last=Askew |first=R. R. |date=1961 |title=On the biology of the inhabitants of oak galls of Cynipidae (Hymenoptera) in Britain |url=https://www.researchgate.net/publication/238289888 |journal=Transactions of the Society for British Entomology |volume=14 |pages=237–268}}</ref> Cases in which two or more species of parasitoids simultaneously attack the same host without parasitizing each other are called multi- or multiple parasitism. In many cases, multiple parasitism still leads to the death of one or more of the parasitoids involved. If multiple parasitoids of the same species coexist in a single host, it is called [[superparasitism]]. Gregarious species lay multiple eggs or polyembryonic eggs which lead to multiple larvae in a single host. The end result of gregarious superparasitism can be a single surviving parasitoid individual or multiple surviving individuals, depending on the species. If superparasitism occurs accidentally in normally solitary species the larvae often fight among themselves until only one is left.<ref>{{cite book |author1=Gullan, P. J. |author2=Cranston, P. S. |date=2014 |title=The Insects: An Outline of Entomology |publisher=Wiley |edition=5th |pages=365–369 |isbn=978-1-118-84615-5 }}</ref><ref>{{cite journal  |last=Fisher |first=R. C. |title=A Study in Insect Multiparasitism: I. Host Selection and Oviposition |journal=Journal of Experimental Biology |date=1 June 1961 |volume=38 |issue=2 |pages=267–275 |doi=10.1242/jeb.38.2.267 |url=http://jeb.biologists.org/cgi/reprint/38/2/267.pdf}}</ref>

===Influencing host behaviour===
[[File:Female Apocephalus borealis ovipositing into the abdomen of a worker honey bee.png|thumb|Female [[Phoridae|phorid fly]] ''[[Apocephalus borealis]]'' (centre left) [[ovipositing]] into the abdomen of a worker [[honey bee]], [[Behavior-altering parasites and parasitoids|altering its behaviour]]]]
{{further|Behavior-altering parasite}}

In another strategy, some parasitoids [[Behavior-altering parasite|influence the host's behaviour]] in ways that favour the propagation of the parasitoid, often at the cost of the host's life. A spectacular example is the [[Dicrocoelium dendriticum|lancet liver fluke]], which causes host ants to die clinging to grass stalks, where grazers or birds may be expected to eat them and complete the parasitoidal fluke's life cycle in its [[Host (biology)#Types_of_hosts|definitive host]]. Similarly, as [[strepsiptera]]n parasitoids of ants mature, they cause the hosts to climb high on grass stalks, positions that are risky, but favour the emergence of the strepsipterans.<ref name=Wojcik>{{cite journal |author=Wojcik, Daniel P. |title=Behavioral Interactions between Ants and Their Parasites |journal=The Florida Entomologist |volume=72 |issue=1 |date=March 1989 |pages=43–51 |doi=10.2307/3494966|jstor=3494966 }}</ref> Among pathogens of mammals, the [[rabies virus]] affects the host's [[central nervous system]], eventually killing it, but perhaps helping to disseminate the virus by modifying the host's behaviour.<ref name="pmid7777324">{{cite journal |author=Taylor, P. J. |title=A systematic and population genetic approach to the rabies problem in the yellow mongoose (Cynictis penicillata) |journal=Onderstepoort J. Vet. Res. |volume=60 |issue=4 |pages=379–87 |date=December 1993 |pmid=7777324}}</ref> Among the parasitic wasps, ''[[Glyptapanteles]]'' modifies the behaviour of its host caterpillar to defend the pupae of the wasps after they emerge from the caterpillar's body.<ref>{{cite journal |last1=Grosman |first1=Amir H. |last2=Janssen |first2=Arne |last3=Brito |first3=Elaine F. de |last4=Cordeiro |first4=Eduardo G. |last5=Colares |first5=Felipe |last6=Fonseca |first6=Juliana Oliveira |last7=Lima |first7=Eraldo R. |last8=Pallini |first8=Angelo |last9=Sabelis |first9=Maurice W. |date=4 June 2008 |title=Parasitoid Increases Survival of Its Pupae by Inducing Hosts to Fight Predators |journal=PLOS ONE |volume=3 |issue=6 |pages=e2276 |doi=10.1371/journal.pone.0002276 |pmc=2386968 |pmid=18523578|bibcode=2008PLoSO...3.2276G |doi-access=free }}</ref> The [[phorid fly]] ''[[Apocephalus borealis]]'' oviposits into the abdomen of its hosts, including [[honey bee]]s, causing them to abandon their nest, flying from it at night and soon dying, allowing the next generation of flies to emerge outside the hive.<ref name=Core2012>{{cite journal |last1=Core |first1=Andrew |last2=Runcke |first2=Charles |last3=Ivers |first3=Jonathan |last4=Quock |first4=Christopher |last5=Siapno |first5=Travis |last6=DeNault |first6=Seraphina |last7=Brown |first7=Brian |last8=DeRisi |first8=Joseph |last9=Smith |first9=Christopher D. |last10=Hafernik |first10=John |year=2012 |title=A new threat to honey bees, the parasitic phorid fly ''Apocephalus borealis'' |journal=[[PLoS ONE]] |volume=7 |issue=1 |pages=e29639 |doi=10.1371/journal.pone.0029639 |pmid=22235317 |pmc=3250467|bibcode=2012PLoSO...729639C |doi-access=free }}</ref>

==Taxonomic range==

About 10% of described insects are parasitoids, in the orders [[Hymenoptera]], [[Diptera]], [[Coleoptera]], [[Neuroptera]], [[Lepidoptera]], [[Strepsiptera]], and [[Trichoptera]]. The majority are wasps within the Hymenoptera; most of the others are Dipteran flies.<ref name=Godfray1994/><ref>{{cite journal |last1=Eggleton |first1=P. |last2=Belshaw |first2=R. |year=1992 |title=Insect parasitoids: an evolutionary overview |journal=Philosophical Transactions of the Royal Society B |volume=337  |issue=1279 |pages=1–20 |doi=10.1098/rstb.1992.0079|bibcode=1992RSPTB.337....1E }}</ref><ref>{{cite book |last1=Foottit |first1=R. G. |last2=Adler |first2=P. H. |year=2009 |title=Insect Biodiversity: Science and Society, Volume 1 |page=656 |publisher=Wiley-Blackwell |isbn=978-1118945537}}</ref> Parasitoidism has [[convergent evolution|evolved independently]] many times: once each in Hymenoptera, Strepsiptera, Neuroptera, and Trichoptera, twice in the Lepidoptera, 10 times or more in Coleoptera, and no less than 21 times among the Diptera. These are all [[holometabolous]] insects ([[Endopterygota]], which form a single [[clade]]), and it is always the larvae that are parasitoidal.<ref name="Foottit 2017"/> The metamorphosis from active larva to an adult with a different body structure [[Exaptation|permits]] the dual lifestyle of parasitic larva, freeliving adult in this group.<ref>{{cite web|title=Parasites (Parasitoids)|url=http://www.biology.ualberta.ca/courses.hp/ent207/lec31-32.htm|publisher=University of Alberta|access-date=10 March 2018|archive-date=2 March 2018|archive-url=https://web.archive.org/web/20180302202049/http://www.biology.ualberta.ca/courses.hp/ent207/lec31-32.htm|url-status=dead}}</ref> These relationships are shown on the [[phylogenetic tree]];<ref name=Niehuis2012>{{cite journal |author1=Niehuis, O. |author2=Hartig, G. |author3=Grath, S. |author4=Pohl, H. |author5=Lehmann, J. |author6=Tafer, H. |author7=Donath, A. |author8=Krauss, V. |author9=Eisenhardt, C. |author10=Hertel, J. |author11=Petersen, M. |author12=Mayer, C. |author13=Meusemann, K. |author14=Peters, R.S. |author15=Stadler, P.F. |author16=Beutel, R.G. |author17=Bornberg-Bauer, E. |author18=McKenna, D.D. |author19=Misof, B. | year=2012 |title=Genomic and Morphological Evidence Converge to Resolve the Enigma of Strepsiptera | journal=Current Biology | volume=22 | issue=14 | pages=1309–1313 |doi=10.1016/j.cub.2012.05.018 | pmid=22704986|doi-access=free |bibcode=2012CBio...22.1309N }}</ref><ref name="ColganZhao2014">{{cite journal |last1=Colgan |first1=Donald J. |last2=Zhao |first2=Chenjing |last3=Liu |first3=Xingyue |last4=Yang |first4=Ding |title=Wing Base Structural Data Support the Sister Relationship of Megaloptera and Neuroptera (Insecta: Neuropterida) |journal=PLOS ONE |volume=9 |issue=12 |year=2014 |pages=e114695 |doi=10.1371/journal.pone.0114695|pmid=25502404 |pmc=4263614 |bibcode=2014PLoSO...9k4695Z |doi-access=free }}</ref> groups containing parasitoids are shown in boldface<!--used redundantly alongside bracketed numbers-->, e.g. '''Coleoptera''', with the number of times parasitoidism evolved in the group in parentheses, e.g. '''(10 clades)'''. The approximate number (estimates can vary widely) of parasitoid species<ref name=Mills2009/> out of the total is shown in square brackets, e.g. [2,500 of 400,000].
{{clade
|label1=[[Endopterygota]]
|1={{clade
   |1={{clade
      |label1=[[Neuropterida]]
      |1={{clade
         |1=''[[Raphidioptera]]''
         |2={{clade
            |1=''[[Megaloptera]]''
            |2='''[[Neuroptera]]''' (net-winged insects) '''(1 clade)''' [c. 15 of 6,000]
            }}
         }}
      |label2=[[Coleopterida]]
      |2={{clade
         |1='''[[Coleoptera]]''' (beetles) '''(10 clades)''' [c. 2,500 of 400,000] [[File:Ripiphorid larva on wing of braconid wasp.jpg|alt=[[Ripiphoridae|Ripiphorid]] beetle [[Planidium|triungulin]] larva on the wing of a [[Braconidae|braconid]] wasp|90px]]
         |label2='''(1 clade)'''
         |2='''[[Strepsiptera]]''' (twisted-wing parasites) [600 of 600] [[File:Strepsiptera.png|90px]]
         }}
      }}
   |2={{clade
      |label1=[[Hymenoptera]]
      |1={{clade
         |1=''[[Symphyta]]''
         |label2= '''(1 clade)'''
         |2={{clade
            |1='''[[Orussoidea]]''' (parasitic wood wasps) [75 of 75] [[File:Orussus coronatus.jpg|alt=Parasitic wood wasp|90px]]
            |2='''[[Apocrita]]''' (wasp-waisted insects) [c. 50,000 of 100,000] [[File:Ichneumon_wasp_(Megarhyssa_macrurus_lunato)_(7686081848).jpg|alt=The [[parasitoid wasp]] ''[[Megarhyssa macrurus]]'' ovipositing into host through wood. Her body is c. 50 mm long, her ovipositor c. 100 mm.|90px]]
            }}
         }}
      |label2=[[Panorpida]]
      |2={{clade
         |1={{clade
            |1='''[[Diptera]]''' (true flies) '''(21 clades)''' [c. 17,000 of 125,000] [[File:Stylogaster macalpini (12947561584, cropped) (cropped).jpg|alt=''[[Stylogaster]]'', a [[Conopidae|conopid fly]], showing the long ovipositor|100px]]
             |2={{clade
                |1=''[[Mecoptera]]''
                |2=''[[Siphonaptera]]''
                }}
             }}
          |2={{clade
             |1='''[[Trichoptera]]''' (caddis flies) '''(1 clade)''' [c. 10 of 14,500]
             |2='''[[Lepidoptera]]''' (butterflies, moths) '''(2 clades)''' [c. 40 of 180,000] [[File:Epiricania hagoromo on Euricania facialis (cropped).JPG|alt=Moth ''Epiricania hagoromo'' ([[Epipyropidae]]) feeding on planthopper ''Euricania facialis''|120px]]
             }}
         }}
      }}
   }}
}}

===Hymenoptera===
{{main|Parasitoid wasp}}
[[File:Potter Wasp building mud nest near completion.JPG|thumb|[[Potter wasp]], an idiobiont, building a mud nest; she will [[mass provisioning|provision it]] with paralysed insects, on which she will lay her eggs; she will then seal the nest and provide no further care for her young]]

Within the Hymenoptera, parasitoidism evolved just once, and the many described{{efn|There may be far more species of parasitoid wasp not yet described.}} species of [[parasitoid wasp]]s<ref>{{cite book |title=Hymenoptera of the world : an identification guide to families |date=1993 |publisher=Centre for Land and Biological Resources Research |author1=Goulet, Henri |author2=Huber, John Theodore |isbn=978-0-660-14933-2 |oclc=28024976}}</ref> represent the great majority of species in the order, barring those like the [[ant]]s, [[bee]]s, and [[Vespidae]] wasps that have secondarily lost the parasitoid habit. The parasitoid wasps include some 25,000 [[Ichneumonoidea]], 22,000 [[Chalcidoidea]], 5,500 [[Vespoidea]], 4,000 [[Platygastroidea]], 3,000 [[Chrysidoidea]], 2,300 [[Cynipoidea]], and many smaller families.<ref name=Mills2009/> These often have remarkable life cycles.<ref>{{cite journal |last=Hochberg |first=M. |author2=Elmes, G. W. |author3=Thomas, J. A. |author4=Clarke, R. T. |title=Mechanisms of local persistence in coupled host-parasitoid associations: the case model of Maculinea rebeli and Ichneumon eumerus|year=1996 |volume=351 |issue=1348 |pages=1713–1724 |doi=10.1098/rstb.1996.0153 |journal=Philosophical Transactions of the Royal Society B: Biological Sciences|bibcode=1996RSPTB.351.1713H }}</ref>
They can be classified as either endoparasitic or ectoparasitic according to where they lay their eggs.<ref name="Kapranas2012">{{cite journal |author1=Apostolos, Kapranas |author2=Tena, Alejandro |author3=Luck, Robert F. |title=Dynamic virulence in a parasitoid wasp: the influence of clutch size and sequential oviposition on egg encapsulation |journal=Animal Behaviour |volume=83 |issue=3 |year=2012 |pages=833–838 |doi=10.1016/j.anbehav.2012.01.004|s2cid=54275511 }}</ref> Endoparasitic wasps insert their eggs inside their host, usually as koinobionts, allowing the host to continue to grow (thus providing more food to the wasp larvae), moult, and evade predators. Ectoparasitic wasps deposit theirs outside the host's body, usually as idiobionts, immediately paralysing the host to prevent it from escaping or throwing off the parasite. They often carry the host to a nest where it will remain undisturbed for the wasp larva to feed on.<ref name=Godfray1994/> Most species of wasps attack the eggs or larvae of their host, but some attack adults. [[Oviposition]] depends on finding the host and on evading host defences; the ovipositor is a tube-like organ used to inject eggs into hosts, sometimes much longer than the wasp's body.<ref>{{cite book |author1=Gullan, P. J. |author2=Cranston, P. S. |date=2010 |title=The Insects: An Outline of Entomology |url=https://archive.org/details/insectsoutlineen00pjgu |url-access=limited |publisher=Wiley |edition=4th |pages=[https://archive.org/details/insectsoutlineen00pjgu/page/n388 364], 367 |isbn=978-1-118-84615-5}}</ref><ref name="Gomez, Jose-Maria 2011">{{cite journal | last1=Gomez | first1=Jose-Maria | last2=van Achterberg | first2=Cornelius | year=2011 | title=Oviposition behaviour of four ant parasitoids (Hymenoptera, Braconidae, Euphorinae, Neoneurini and Ichneumonidae, Hybrizontinae), with the description of three new European species | journal=ZooKeys | issue=125 | pages=59–106 | doi=10.3897/zookeys.125.1754| pmid=21998538 | pmc=3185369 | doi-access=free | bibcode=2011ZooK..125U..59V }}</ref><ref name="Quicke Fitton pp. 99–103">{{cite journal | last1=Quicke | first1=D. L. J. | last2=Fitton | first2=M. G. | title=Ovipositor Steering Mechanisms in Parasitic Wasps of the Families Gasteruptiidae and Aulacidae (Hymenoptera) | journal=Proceedings of the Royal Society B: Biological Sciences | publisher=The Royal Society | volume=261 | issue=1360 | date=22 July 1995 | doi=10.1098/rspb.1995.0122 | pages=99–103 | bibcode=1995RSPSB.261...99Q | s2cid=84043987 |quote=The length of the ovipositor compared with the body of the parasitic wasp varies enormously between taxa, from being a fraction of the length of the metasoma to more than 14 times longer than the head and body. (Townes 1975; Achterberg 1986; Compton & Nefdt 1988).}}</ref> Hosts such as ants often behave as if aware of the wasps' presence, making violent movements to prevent oviposition. Wasps may wait for the host to stop moving, and then attack suddenly.<ref name="Achterberg C 1993">Van Achterberg Cornelius; Argaman Q. "Kollasmosoma gen. nov. and a key to the genera of the subfamily Neoneurinae (Hymenoptera: Braconidae)". Zoologische Mededelingen Leiden. 67. (1993):63-74.</ref>

Parasitoid wasps face a range of obstacles to oviposition,<ref name=Godfray1994/> including behavioural, morphological, physiological and immunological defences of their hosts.<ref name="Kapranas2012"/><ref>{{cite journal | last1=Schmidt | first1=O. | last2=Theopold | first2=U. | last3=Strand | first3=M.R. | year=2001 | title=Innate immunity and evasion by insect parasitoids | journal=BioEssays | volume=23 | issue=4| pages=344–351 | doi=10.1002/bies.1049| pmid=11268040 | s2cid=20850885 }}</ref> To thwart this, some wasps inundate their host with their eggs so as to overload its immune system's ability to encapsulate foreign bodies;<ref>{{cite journal |last1=Salt |first1=George | year=1968 | title=The resistance of insect parasitoids to the defense reactions of their hosts | journal=Biological Reviews of the Cambridge Philosophical Society | volume=43 | issue=2| pages=200–232 | doi=10.1111/j.1469-185x.1968.tb00959.x|pmid=4869949 |s2cid=21251615 }}</ref> others introduce a [[Polydnavirus|virus]] which interferes with the host's immune system.<ref>{{cite journal | last1=Summers | first1=M. D. | last2=Dib-Hajj | year=1995 | title=Polydnavirus-facilitated endoparasite protection against host immune defenses | journal=PNAS | volume=92 | issue=1 | pages=29–36 | doi=10.1073/pnas.92.1.29| pmid=7816835 | pmc=42812 | bibcode=1995PNAS...92...29S | doi-access=free }}</ref>
Some parasitoid wasps locate hosts by detecting the chemicals that plants release to defend against insect herbivores.<ref name="Kessler, Andre 2002">{{cite journal | last1=Kessler | first1=Andre | last2=Baldwin | first2=Ian T. | year=2002 | title=Plant Responses to Insect Herbivory: The Emerging Molecular Analysis | journal= Annual Review of Plant Biology  | volume=53 | pages=299–328 | doi=10.1146/annurev.arplant.53.100301.135207| pmid=12221978 }}</ref>

===Other orders===
[[File:Odynerus spinipes^ Vespidae. See parasite note - Flickr - gailhampshire.jpg|thumb|upright|The head of a sessile female [[strepsiptera]]n protruding (lower right) from the abdomen of its wasp host; the male (not shown) has wings]]

The true flies ([[Diptera]]) include several families of parasitoids, the largest of which is the [[Tachinidae]] (some 9,200 species<ref name=Mills2009/>), followed by the [[Bombyliidae]] (some 4,500 species<ref name=Mills2009/>), along with the [[Pipunculidae]] and the [[Conopidae]], which includes parasitoidal genera such as ''[[Stylogaster]]''.  Other families of flies include some [[protelean]] species.<ref name=UWM>{{cite web |url=http://www.entomology.wisc.edu/mbcn/fea506.html |title=Midwest Biological Control News |publisher=Department of Entomology at the University of Wisconsin–Madison |access-date=19 February 2018 |archive-date=5 October 2017 |archive-url=https://web.archive.org/web/20171005235859/http://www.entomology.wisc.edu/mbcn/fea506.html |url-status=dead }}</ref> Some [[Phoridae]] are parasitoids of ants.<ref>{{cite journal |last1=Wuellner |first1=C. T.|display-authors=etal|title=Phorid Fly (Diptera: Phoridae) Oviposition Behavior and Fire Ant (Hymenoptera: Formicidae) Reaction to Attack Differ According to Phorid Species |journal=Annals of the Entomological Society of America |date=2002 |volume=95 |issue=2 |pages=257–266 |doi=10.1603/0013-8746(2002)095[0257:pfdpob]2.0.co;2 |doi-access=free}}</ref><ref>{{Cite journal|last1=Feener |first1=Donald H. Jr.|last2=Jacobs |first2=Lucia F.|last3=Schmidt |first3=Justin O. |date=January 1996 |title=Specialized parasitoid attracted to a pheromone of ants |journal=Animal Behaviour |volume=51 |issue=1 |pages=61–66 |doi=10.1006/anbe.1996.0005|s2cid=16627717|issn=0003-3472}}</ref> Some [[Sarcophagidae|flesh flies]] are parasitoids: for instance ''Emblemasoma auditrix'' is parasitoidal on cicadas, locating its host by sound.<ref>{{cite journal |author1=Köhler, U. |author2=Lakes-Harlan, R. |title=Auditory behaviour of a parasitoid fly (Emblemasoma auditrix, Sarcophagidae, Diptera) |journal=J Comp Physiol A |date=October 2001 |volume=187 |issue=8 |pages=581–587|doi=10.1007/s003590100230 |pmid=11763956 |s2cid=23343345 }}</ref>

The [[Strepsiptera]] (twisted-wing parasites) consist entirely of parasitoids; they usually sterilise their hosts.<ref>{{cite book |author=Whiting, M. F. |editor1=Resh, V. H. |editor2=Cardé, R. T. |year=2003 |title=Encyclopedia of Insects |url=https://archive.org/details/encyclopediainse00resh |url-access=limited |publisher=Academic Press |chapter=Strepsiptera |pages=[https://archive.org/details/encyclopediainse00resh/page/n1122 1094]–1096|isbn=9780125869904 }}</ref>

Two [[Coleoptera|beetle]] families, [[Ripiphoridae]] (450 species<ref name=Mills2009/>)<ref name=ambeetles>{{cite book |author=Falin, Z. H. |year=2002 |chapter=102. Ripiphoridae. Gemminger and Harold 1870 (1853) |pages=431–444 |editor1=Arnett, R.H. Jr |editor2=Thomas, M. C. |editor3=Skelley, P. E. |editor4=Frank, J. H. |title=American beetles. Volume 2. Polyphaga: Scarabaeoidea through Curculionoidea |publisher=CRC Press |isbn=978-0-8493-0954-0 |doi=10.1201/9781420041231.ch6|doi-broken-date=12 November 2024 }}</ref><ref>{{cite book |author1=Lawrence, J. F. |author2=Falin, Z. H. |author3=Ślipiński, A. |year=2010 |chapter=Ripiphoridae Gemminger and Harold, 1870 (Gerstaecker, 1855) |pages=538–548 |editor=Leschen, R. A. B. |editor2=Beutel, R. G. |editor3=Lawrence, J. F. |title=Coleoptera, beetles. Volume 2: Morphology and systematics (Elateroidea, Bostrichiformia, Cucujiformia partim) |place=New York |publisher=Walter de Gruyter |isbn=978-3-11-019075-5 |doi=10.1515/9783110911213.538}}</ref> and [[Rhipiceridae]], are largely parasitoids, as are ''[[Aleochara]]'' [[Staphylinidae]]; in all, some 400 staphylinids are parasitoidal.<ref name=Mills2009/><ref name=UWM/><ref name="YamamotoMaruyama2016">{{cite journal |last1=Yamamoto |first1=Shûhei |last2=Maruyama |first2=Munetoshi |title=Revision of the subgenus ''Aleochara'' Gravenhorst of the parasitoid rove beetle genus ''Aleochara'' Gravenhorst of Japan (Coleoptera: Staphylinidae: Aleocharinae) |journal=Zootaxa |volume=4101 |issue=1 |pages=1–68 |year=2016 |doi=10.11646/zootaxa.4101.1.1|pmid=27394607 }}</ref> Some 1,600 species of the large and mainly freeliving family [[Carabidae]] are parasitoids.<ref name=Mills2009/>

A few Neuroptera are parasitoidal; they have larvae that actively search for hosts.<ref>{{cite book |last=Godfray |first=H. C. J. |title=Parasitoids: Behavioral and Evolutionary Ecology |url=https://archive.org/details/parasitoidsbehav0000godf |url-access=registration |year=1994|publisher=Princeton University Press|isbn=978-0-691-00047-3 |page=[https://archive.org/details/parasitoidsbehav0000godf/page/40 40]}}</ref> The larvae of some [[Mantispidae]], subfamily Symphrasinae, are parasitoids of other arthropods including bees and wasps.<ref name=Mills2009>{{cite encyclopedia |author=Mills, N. |date=2009 |edition=2nd |title=Parasitoids |encyclopedia=Encyclopedia of Insects |editor=V. H. Resh |editor2=R. T. Cardé |pages=748–750 |publisher=Elsevier |isbn=978-0123741448 |url=https://books.google.com/books?id=Jk0Hym1yF0cC&pg=PA749}}</ref>

Although nearly all Lepidoptera (butterflies and moths) are herbivorous, a few species are parasitic. The larvae of [[Epipyropidae]] feed on [[Homoptera]] such as leafhoppers and cicadas, and sometimes on other Lepidoptera. The larvae of [[Cyclotornidae]] parasitise first Homoptera and later [[ant]] brood.<ref>{{cite journal |last1=Pierce |first1=Naomi E. |title=Predatory and Parasitic Lepidoptera: Carnivores Living on Plants |journal=Journal of the Lepidopterists' Society |date=1995 |volume=49 |issue=4 |pages=412–453 |url=http://images.peabody.yale.edu/lepsoc/jls/1990s/1995/1995-49(4)412-Pierce.pdf}}</ref> The [[Pyralidae|pyralid moth]] ''[[Chalcoela]]'' has been used in biological control of the wasp ''[[Polistes]]'' in the [[Galapagos Islands]].<ref name="Foottit 2017">{{cite book |last=Foottit |first=Robert G. |title=Insect Biodiversity: Science and Society |url=https://books.google.com/books?id=V3ItDwAAQBAJ&pg=PA606 |year=2017 |publisher=John Wiley & Sons |isbn=978-1-118-94553-7 |page=606}}</ref>

Parasitism is rare in the Trichoptera (caddisflies), but it is found among the [[Hydroptilidae]] (purse-case caddisflies), probably including all 10 species in the ''Orthotrichia aberrans'' group; they parasitise the pupae of other trichopterans.<ref name="Wells 2005">{{cite journal | last=Wells | first=Alice | title=Parasitism by hydroptilid caddisflies (Trichoptera) and seven new species of Hydroptilidae from northern Queensland | journal=Australian Journal of Entomology | volume=44 | issue=4 | year=2005 | doi=10.1111/j.1440-6055.2005.00492.x | pages=385–391}}</ref>

Mites of the family [[Acarophenacidae]] are ectoparasitoids of insect eggs. Unlike the insect parasitoids, it is the adult stage in Acarophenacidae that acts as a parasitoid. Specifically, adult female mites feed on insect eggs and their body swells up with offspring, which eventually emerge as adults.<ref>{{Citation |title=Acarophenacidae |date=2003-01-23 |work=Mites (Acari) for Pest Control |pages=74–77 |editor-last=Gerson |editor-first=Uri |url=https://onlinelibrary.wiley.com/doi/10.1002/9780470750995.ch5 |access-date=2024-08-28 |edition=1 |publisher=Wiley |language=en |doi=10.1002/9780470750995.ch5 |isbn=978-0-632-05658-3 |editor2-last=Smiley |editor2-first=Robert L. |editor3-last=Ochoa |editor3-first=Ronald|url-access=subscription }}</ref>

=== Entomopathogenic fungi ===
All known fungi in the genera ''[[Cordyceps]]'' and ''[[Ophiocordyceps]]'' are endoparasitic.<ref>{{Cite journal |last1=Qu |first1=Shuai-Ling |last2=Li |first2=Su-Su |last3=Li |first3=Dong |last4=Zhao |first4=Pei-Ji |date=2022-07-24 |title=Metabolites and Their Bioactivities from the Genus Cordyceps |journal=Microorganisms |volume=10 |issue=8 |pages=1489 |doi=10.3390/microorganisms10081489 |issn=2076-2607 |pmc=9330831 |pmid=35893547|doi-access=free }}</ref> One of the most notable fungal parasitoids is ''[[Ophiocordyceps unilateralis|O. unilateralis]]'' which infects carpenter ants by breaching the ant's exoskeletons via their spores and growing in the ant's hemocoel as free living yeast cells. Eventually the yeast cells progress to producing nerve toxins to alter the behaviour of the ant causing it to climb and bite onto vegetation, known as the 'death bite'.<ref>{{Cite journal |last1=Evans |first1=Harry C. |last2=Elliot |first2=Simon L. |last3=Hughes |first3=David P. |date=September 1, 2011 |title=''Ophiocordyceps unilateralis'': A keystone species for unraveling ecosystem functioning and biodiversity of fungi in tropical forests? |journal= [[Communicative & Integrative Biology]] |volume=4 |issue=5 |pages=598–602 |doi=10.4161/cib.16721 |pmid=22046474 |pmc=3204140 }}</ref> This approach is so fine-tuned, it causes the ant to bite down on the adaxial leaf midrib, which is the part of the leaf most optimal for the fungus to fruit. In fact, it has been found that in specific circumstances, the time of the death bite is synchronised to solar noon.<ref>{{Cite journal |last1=Hughes |first1=David P |last2=Andersen |first2=Sandra B |last3=Hywel-Jones |first3=Nigel L |last4=Himaman |first4=Winanda |last5=Billen |first5=Johan |last6=Boomsma |first6=Jacobus J |date=2011 |title=Behavioral mechanisms and morphological symptoms of zombie ants dying from fungal infection |journal= [[BMC Ecology]] |language=en |volume=11 |issue=1 |pages=13 |doi=10.1186/1472-6785-11-13 |issn=1472-6785 |pmc=3118224 |pmid=21554670 |doi-access=free |bibcode=2011BMCE...11...13H }}</ref> As much as 40% of the ant's biomass is fungal hyphae at the moment of the death bite.<ref>{{Cite book |last=Sheldrake |first=Merlin |title=Entangled Life |publisher=Vintage |year=2021 |isbn=9781784708276 |pages=107–119 |language=En}}</ref> After the ant dies, the fungus produces a large stalk, growing from the back of the ant's head<ref>{{Cite journal |last1=Pontoppidan |first1=Maj-Britt |last2=Himaman |first2=Winanda |last3=Hywel-Jones |first3=Nigel L. |last4=Boomsma |first4=Jacobus J. |last5=Hughes |first5=David P. |date=2009-03-12 |editor-last=Dornhaus |editor-first=Anna |title=Graveyards on the Move: The Spatio-Temporal Distribution of Dead Ophiocordyceps-Infected Ants |journal= [[PLOS ONE]] |language=en |volume=4 |issue=3 |pages=e4835 |doi=10.1371/journal.pone.0004835 |issn=1932-6203 |pmc=2652714 |pmid=19279680|doi-access=free |bibcode=2009PLoSO...4.4835P }}</ref> which subsequently releases ascospores. These spores are too large to be wind dispersed and instead fall directly to the ground where they produce secondary spores that infect ants as they walk over them.<ref>{{Cite journal |last1=Pontoppidan |first1=Maj-Britt |last2=Himaman |first2=Winanda |last3=Hywel-Jones |first3=Nigel L. |last4=Boomsma |first4=Jacobus J. |last5=Hughes |first5=David P. |date=2009-03-12 |editor-last=Dornhaus |editor-first=Anna |title=Graveyards on the Move: The Spatio-Temporal Distribution of Dead ''Ophiocordyceps''-Infected Ants |journal= [[PLOS ONE]] |language=en |volume=4 |issue=3 |pages=e4835 |doi=10.1371/journal.pone.0004835 |issn=1932-6203 |pmc=2652714 |pmid=19279680|doi-access=free |bibcode=2009PLoSO...4.4835P }}</ref> ''[[Ophiocordyceps sinesis|O. sinesis]]'' is a parasitoid as well, parasitising ghost moth larvae, killing them within 15-25 days, a similar process to that of ''O. unilateralis''.<ref>{{Cite journal |last1=Zhang |first1=Yongjie |last2=Li |first2=Erwei |last3=Wang |first3=Chengshu |last4=Li |first4=Yuling |last5=Liu |first5=Xingzhong |date=2012-03-01 |title=Ophiocordyceps sinensis, the flagship fungus of China: terminology, life strategy and ecology |journal=Mycology |volume=3 |issue=1 |pages=2–10 |doi=10.1080/21501203.2011.654354 |issn=2150-1203|doi-access=free }}</ref>

== Learning in parasitoids ==
Host location has been studied in ''[[Ormia ochracea]],'' a parasitoid tachinid fly that locates their field cricket host acoustically ([[Taxis|phonotaxis]]).<ref>{{Cite journal |last=Cade |first=W. |date=1975-12-26 |title=Acoustically Orienting Parasitoids: Fly Phonotaxis to Cricket Song |url=https://www.science.org/doi/10.1126/science.190.4221.1312 |journal=Science |language=en |volume=190 |issue=4221 |pages=1312–1313 |doi=10.1126/science.190.4221.1312 |issn=0036-8075|url-access=subscription }}</ref> Preference for the dominant local host species was not explained by DNA analysis. In fact, populations across the southern U.S. were inexplicably closely related, considering rate of range expansion from a presumed Central American origin.<ref>{{Cite journal |last1=Gray |first1=David A. |last2=Banuelos |first2=Christina |last3=Walker |first3=Sean E. |last4=Cade |first4=William H. |last5=Zuk |first5=Marlene |date=2007-01-01 |title=Behavioural specialization among populations of the acoustically orienting parasitoid fly Ormia ochracea utilizing different cricket species as hosts |url=https://www.sciencedirect.com/science/article/pii/S0003347206003939 |journal=Animal Behaviour |volume=73 |issue=1 |pages=99–104 |doi=10.1016/j.anbehav.2006.07.005 |issn=0003-3472|hdl=10211.3/195743 |hdl-access=free }}</ref> A captive population of lab-reared flies were raised on two different host songs (''Gryllus integer'' or ''G. lineaticeps''). Responsive adult females overwhelmingly chose their familiar song, indicating the use of a learned, auditory search image. This [[phenotypic plasticity]] allows such a highly specialized parasitoid to avoid overspecialization disasters. Interestingly, when receptive females only heard silence the night before testing for preference, they chose the host songs equally, 50/50.<ref>{{Cite journal |last1=Paur |first1=Jennifer |last2=Gray |first2=David A. |date=2011-10-01 |title=Individual consistency, learning and memory in a parasitoid fly, Ormia ochracea |url=https://www.sciencedirect.com/science/article/pii/S0003347211002971 |journal=Animal Behaviour |volume=82 |issue=4 |pages=825–830 |doi=10.1016/j.anbehav.2011.07.017 |issn=0003-3472|url-access=subscription }}</ref> This capacity for learning and use of search images paired with a highly specialized morphology and lifestyle (eg. tympana tuned to host sound cues, larviparous) supports the extraordinarily fast range expansion of ''O. ochracea,'' as well as the presence and power of learning in parasitoids.

== Interactions with humans ==

=== In biological pest control ===
{{Main|Biological pest control}}
[[File:Encarsia formosa, an endoparasitic wasp, is used for whitefly control.jpg|thumb|''[[Encarsia formosa]]'', an endoparasitic [[Aphelinidae|aphelinid]] wasp, bred commercially to control whitefly in [[greenhouse]]s]]

Parasitoids are among the most widely used biological control agents. Classic [[biological pest control]] using natural enemies of pests (parasitoids or predators) is extremely cost effective, the cost/benefit ratio for classic control being 1:250, but the technique is more variable in its effects than pesticides; it reduces rather than eliminates pests. The cost/benefit ratio for screening natural enemies is similarly far higher than for screening chemicals: 1:30 against 1:5 respectively, since the search for suitable natural enemies can be guided accurately with ecological knowledge. Natural enemies are more difficult to produce and to distribute than chemicals, as they have a shelf life of weeks at most; and they face a commercial obstacle, namely that they cannot be patented.<ref name="Bale2008">{{cite journal | last1=Bale | first1=J.S | last2=van Lenteren | first2=J.C | last3=Bigler | first3=F | title=Biological control and sustainable food production | journal=Philosophical Transactions of the Royal Society B: Biological Sciences | publisher=The Royal Society | volume=363 | issue=1492 | date=February 2008 | doi=10.1098/rstb.2007.2182 | pmid=17827110 | pages=761–776| pmc=2610108 }}</ref><ref>{{cite web |last1=Legner |first1=Erich F.|title=Economic Gains & Analysis Of Successes In Biological Pest Control |url=http://www.faculty.ucr.edu/~legneref/biotact/bc-5.htm |publisher=University of California, Riverside |access-date=13 February 2018 |archive-url=https://web.archive.org/web/20080623113302/http://www.faculty.ucr.edu/~legneref/biotact/bc-5.htm |archive-date=23 June 2008 |url-status=live}}</ref>

From the point of view of the farmer or horticulturalist, the most important groups are the [[Ichneumon wasp|ichneumonid wasps]], which prey mainly on [[caterpillar]]s of [[butterflies]] and [[moths]]; [[braconid wasp]]s, which attack caterpillars and a wide range of other insects including [[aphid|greenfly]]; [[chalcid wasp|chalcidoid wasps]], which parasitise eggs and larvae of greenfly, [[whitefly]], [[cabbage caterpillar]]s, and [[scale insect]]s; and [[Tachinidae|tachinid flies]], which parasitise a wide range of insects including caterpillars, adult and larval [[beetle]]s, and [[true bugs]].<ref>{{cite web |title=Parasitoid Wasps (Hymenoptera) |url=https://extension.umd.edu/hgic/insects/parasitoid-wasps-hymenoptera |publisher=University of Maryland |access-date=6 June 2016 |archive-date=27 August 2016 |archive-url=https://web.archive.org/web/20160827072031/https://extension.umd.edu/hgic/insects/parasitoid-wasps-hymenoptera |url-status=dead }}</ref> Commercially, there are two types of rearing systems: short-term seasonal daily output with high production of parasitoids per day, and long-term year-round low daily output with a range in production of 4–1000 million female parasitoids per week, to meet demand for suitable biological control agents for different crops.<ref name=smith>{{cite journal |author=Smith, S. M. |date=1996 |title=Biological control with Trichogramma: advances, successes, and potential of their use |journal=Annual Review of Entomology |volume=41 |pages=375–406 |pmid=15012334 |doi=10.1146/annurev.en.41.010196.002111}}</ref><ref>{{cite book |author1=Wajnberg, E. |author2=Hassan, S.A. |title=Biological Control with Egg Parasitoids |publisher=CABI Publishing |year=1994}}</ref>{{-}}

=== Maria Sibylla Merian ===
[[File:Garden Tiger Moth Maria Sibylla Merian.png|thumb|upright|[[Parasitic wasp]]s (centre right) with their [[garden tiger moth]] host, by [[Maria Sibylla Merian]]]]

[[Maria Sibylla Merian]] (1647–1717) was one of the first naturalists to study and depict parasitoids and their insect hosts in her closely-observed paintings.<ref name="Todd2011">{{cite journal |last=Todd |first=Kim |title=Maria Sibylla Merian (1647-1717): an early investigator of parasitoids and phenotypic plasticity |journal=Terrestrial Arthropod Reviews |volume=4 |issue=2 |year=2011 |pages=131–144 |doi=10.1163/187498311X567794}}</ref>

=== Charles Darwin ===

Parasitoids influenced the religious thinking of [[Charles Darwin]],{{efn|Darwin mentions "parasitic" wasps in ''[[On the Origin of Species]]'', Chapter 7, page 218.<ref>''[[On the Origin of Species]]'', Chapter 7, [http://darwin-online.org.uk/content/frameset?pageseq=236&itemID=F373&viewtype=side page 218.]</ref>}} who wrote in an 1860 letter to the American naturalist [[Asa Gray]]: "I cannot persuade myself that a beneficent and omnipotent God would have designedly created parasitic wasps with the express intention of their feeding within the living bodies of Caterpillars."<ref name=Darwin>{{cite web |url=http://www.darwinproject.ac.uk/entry-2814 | title=Letter 2814&nbsp;— Darwin, C. R. to Gray, Asa, 22 May [1860] |access-date=5 April 2011}}</ref> The palaeontologist [[Donald Prothero]] notes that religiously minded people of the [[Victorian era]], including Darwin, were horrified by this instance of evident cruelty in nature, particularly noticeable in the [[Ichneumonidae|ichneumonid]] wasps.<ref name=Prothero2017>{{cite book |last=Prothero |first=Donald R. |title=Evolution: What the Fossils Say and Why It Matters |url=https://books.google.com/books?id=-LIvDwAAQBAJ&pg=PT85 |year=2017 |publisher=Columbia University Press |isbn=978-0-231-54316-3| pages=84–86}}</ref>

===In science fiction===
{{further|Parasites in fiction|Alien (creature in Alien franchise)}}

[[File:Paisley Abbey "Xenomorph" Gargoyle (10317339143) (cropped).jpg|thumb|left|A 1990s [[gargoyle]] at [[Paisley Abbey]], Scotland, resembling a [[Alien (creature in Alien franchise)|Xenomorph]]<ref>{{cite web |last1=Budanovic |first1=Nikola |title=An explanation emerges for how the 12th century Paisley Abbey in Scotland could feature a gargoyle out of the film "Alien" |url=https://www.thevintagenews.com/2018/03/10/alien-gargoyle/ |publisher=The Vintage News |access-date=17 June 2018 |date=10 March 2018}}</ref> parasitoid from the film ''[[Alien (film)|Alien]]''<ref>{{cite web |title='Alien' gargoyle on ancient Paisley Abbey |url=https://www.bbc.co.uk/news/uk-scotland-glasgow-west-23810979 |publisher=[[British Broadcasting Corporation]] |access-date=17 June 2018 |date=23 August 2013}}</ref>]]

Parasitoids have inspired [[science fiction]] authors and screenwriters to create terrifying [[Parasites in fiction|parasitic alien species]] that kill their human hosts.<ref name=Moisseeff2014>{{cite book |last1=Moisseeff |first1=Marika |author-link=Marika Moisseeff |title=Aliens as an Invasive Reproductive Power in Science Fiction |url=https://hal.archives-ouvertes.fr/hal-00935705 |website=HAL Archives-Ouvertes |date=23 January 2014|pages=239–257 |publisher=Polis, Sofia }}</ref> One of the best-known is the [[Alien (creature in Alien franchise)|Xenomorph]] in [[Ridley Scott]]'s 1979 film ''[[Alien (film)|Alien]]'', which runs rapidly through its lifecycle from violently entering a human host's mouth to bursting fatally from the host's chest.<ref name="Pappas2012">{{cite web |last1=Pappas |first1=Stephanie |title=5 Alien Parasites and Their Real-World Counterparts |url=https://www.livescience.com/20624-5-alien-parasites-real-inspiration.html |publisher=Live Science |date=29 May 2012}}</ref><ref>{{cite web |last1=Williams |first1=Robyn |last2=Field |first2=Scott |title=Behaviour, Evolutionary Games and .... Aliens |url=http://www.abc.net.au/science/kelvin/files/s223.htm |publisher=Australian Broadcasting Corporation |access-date=30 November 2017 |date=27 September 1997}}</ref><ref name=Guardian2009>{{cite web |title=The Making of Alien's Chestburster Scene |date=13 October 2009 |work=[[The Guardian]] |url=https://www.theguardian.com/film/2009/oct/13/making-of-alien-chestburster |access-date=29 May 2010| archive-url=https://web.archive.org/web/20100430221033/http://www.guardian.co.uk/film/2009/oct/13/making-of-alien-chestburster| archive-date=30 April 2010 | url-status=live}}</ref> The molecular biologist Alex Sercel, writing in ''Signal to Noise Magazine'', compares "the biology of the [''Alien''] Xenomorphs to parasitoid wasps and [[Nematomorpha|nematomorph worms]] from Earth to illustrate how close to reality the biology of these aliens is and to discuss this exceptional instance of science inspiring artists".<ref name=Sercel2017>{{cite web |last1=Sercel |first1=Alex |title=Parasitism in the Alien Movies |url=http://www.signaltonoisemag.com/allarticles/2017/5/19/parasitism-in-the-alien-movies |archive-url=https://web.archive.org/web/20170705023131/http://www.signaltonoisemag.com/allarticles/2017/5/19/parasitism-in-the-alien-movies |url-status=usurped |archive-date=5 July 2017 |publisher=Signal to Noise Magazine |date=19 May 2017}}</ref> Sercel notes that the way the Xenomorph grasps a human's face to implant its embryo is comparable to the way a parasitoid wasp lays its eggs in a living host. He further compares the Xenomorph life cycle to that of the nematomorph ''[[Paragordius tricuspidatus]]'' which grows to fill its host's body cavity before bursting out and killing it.<ref name=Sercel2017/> [[Alistair Dove]], on the science website ''Deep Sea News'', writes that there are multiple parallels with parasitoids, although in his view, there are more disturbing life cycles in real biology. Dove stated that the parallels include the placing of an embryo in the host; its growth in the host; the resulting death of the host; and [[Heterogamy|alternating generations]], as in the [[Digenea]] (trematodes).<ref name="Dove2011">{{cite web |last1=Dove |first1=Alistair |title=This is clearly an important species we're dealing with |url=http://www.deepseanews.com/2011/05/this-is-clearly-an-important-species-were-dealing-with/ |publisher=Deep Sea News |date=9 May 2011}}</ref> The social anthropologist [[Marika Moisseeff]] argues that "The parasitical and swarming aspects of insect reproduction make these animals favoured [[Villain|villains]] in [[Cinema of the United States|Hollywood]] science fiction. The battle of culture against nature is depicted as an unending combat between humanity and insect-like extraterrestrial species that tend to parasitise human beings in order to reproduce."<ref name=Moisseeff2014/> ''[[The Encyclopedia of Science Fiction]]'' lists many instances of "parasitism", often causing the host's death.<ref>{{cite encyclopedia|title=Parasitism and Symbiosis |url=http://www.sf-encyclopedia.com/entry/parasitism_and_symbiosis |encyclopedia=[[The Encyclopedia of Science Fiction]] |date=10 January 2016}}</ref>

==Notes==
{{notelist}}

==References==
{{reflist|30em}}

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[[Category:Parasitology]]
[[Category:Parasitism]]
[[Category:Biological pest control]]