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[[File:Ichneumon_wasp_(Megarhyssa_macrurus_lunato)_(7686081848).jpg|thumb|upright=1.2|''[[Megarhyssa macrurus]]'' ([[Ichneumonidae]]), a [[parasitoid]], ovipositing into its host through the wood of a tree. The body of a female is c. {{convert|2|inch|mm|sigfig=1}} long, with an ovipositor c. {{convert|4|inch|mm}} long.]]
[[File:Neoneurus vesculus ovipositing in workers of the ant Formica cunicularia.ogv|thumb|Females of the parasitoid wasp ''[[Neoneurus vesculus]]'' ([[Braconidae]]) [[ovipositing]] in workers of the ant ''[[Formica cunicularia]]''.]]
[[File:White cabbage paraistiized larvae.webm|right|thumb|thumbtime=45|Parasitized white cabbage larvae showing wasp larvae exiting its body, spinning cocoons. Playback at double speed. Adult wasps at normal speed.]]
'''Parasitoid wasps''' are a large group of [[hymenoptera]]n [[Superfamily (zoology)|superfamilies]], with all but the wood wasps ([[Orussoidea]]) being in the wasp-waisted [[Apocrita]]. As [[parasitoid]]s, they lay their eggs on or in the bodies of other [[arthropod]]s, sooner or later causing the death of these [[host (biology)|hosts]]. Different species specialise in hosts from different insect orders, most often [[Lepidoptera]], though some select [[Coleoptera|beetles]], [[Diptera|flies]], or [[Hemiptera|bugs]]; the spider wasps ([[Pompilidae]]) exclusively attack [[spider]]s.
Parasitoid wasp species differ in which host life-stage they attack: eggs, larvae, pupae, or adults. They mainly follow one of two major strategies within [[parasitism]]: either they are endoparasitic, developing inside the host, and koinobiont, allowing the host to continue to feed, develop, and moult; or they are ectoparasitic, developing outside the host, and idiobiont, paralysing the host immediately. Some endoparasitic wasps of the superfamily Ichneumonoidea have a [[mutualism (biology)|mutualistic relationship]] with [[polydnavirus]]es, the viruses suppressing the host's immune defenses.<ref>{{Cite journal |last1=Herniou |first1=Elisabeth A. |last2=Huguet |first2=Elisabeth |last3=Thézé |first3=Julien |last4=Bézier |first4=Annie |last5=Periquet |first5=Georges |last6=Drezen |first6=Jean-Michel |date=2013-09-19 |title=When parasitic wasps hijacked viruses: genomic and functional evolution of polydnaviruses |journal=Phil. Trans. R. Soc. B |
Parasitoidism evolved only once in the Hymenoptera, during the [[Permian]], leading to a single [[clade]] called Euhymenoptera,<ref name=":0">{{Cite journal |last1=Zhang |first1=Qi |last2=Kopylov |first2=Dmitry S. |last3=Rasnitsyn |first3=Alexandr P. |last4=Zheng |first4=Yan |last5=Zhang |first5=Haichun |date=November 2020 |editor-last=Smith |editor-first=Andrew |title=Burmorussidae, a new family of parasitic wasps (Insecta, Hymenoptera) from mid-Cretaceous Burmese amber |url=https://onlinelibrary.wiley.com/doi/10.1002/spp2.1312 |journal=Papers in Palaeontology |volume=6 |issue=4|pages=593–603|doi=10.1002/spp2.1312 |s2cid=219039881 |issn=2056-2802}}</ref> but the parasitic lifestyle has secondarily been lost several times including among the [[ant]]s, [[bee]]s, and [[Vespidae|
Host insects have evolved a range of defences against parasitoid wasps, including hiding, wriggling, and camouflage markings.
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== Parasitoidism ==
[[File:Parasitoid Strategies Koinobiont Compared to Idiobiont.svg|thumb|left|upright=2|Two strategies found among parasitoidal wasps: Ectoparasites are usually idiobiont, endoparasites koinobiont.]]
{{further|Parasitoid}}
Parasitoid wasps range from some of the smallest species of insects to wasps about an inch long. Most females have a long, sharp ovipositor at the tip of the abdomen, sometimes lacking [[venom]] glands, and almost never modified into a [[stinger|sting]].<ref name=GullanCranston2010/>
Parasitoids can be classified in a variety of ways. They can live within their host's body as endoparasitoids, or feed on it from outside as ectoparasitoids: both strategies are found among the wasps. Parasitoids can also be divided according to their effect on their hosts. Idiobionts prevent further development of the host after initially immobilizing it, while koinobionts allow the host to continue its development while they are feeding upon it; and again, both types are seen in parasitoidal wasps. Most ectoparasitoid wasps are idiobiont, as the host could damage or dislodge the external parasitoid if allowed to move or [[Moulting|moult]]. Most endoparasitoid wasps are koinobionts, giving them the advantage of a host that continues to grow larger and remains able to avoid predators.<ref name=GullanCranston2010>{{cite book |author1=Gullan, P. J. |author2=Cranston, P. S. |date=2010 |title=The Insects: An Outline of Entomology |publisher=Wiley |edition=5th |isbn=978-1-118-84615-5 |pages=362–370}}</ref>
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=== Hosts ===
Many parasitoid wasps use larval Lepidoptera as hosts, but some groups parasitize different host life stages (egg, larva or nymph, pupa, adult) of nearly all other orders of insects, especially [[Coleoptera]], [[Diptera]], [[Hemiptera]] and other Hymenoptera. Some attack arthropods other than insects: for instance, the [[Pompilidae]] specialise in catching [[spider]]s: these are quick and dangerous prey, often as large as the wasp itself, but the spider wasp is quicker, swiftly stinging her prey to immobilise it. Adult female wasps of most species oviposit into their hosts' bodies or eggs.
More rarely, parasitoid wasps may use plant seeds as hosts, such as ''[[Torymus druparum]]''.<ref>{{cite journal |author=Cushman R. A. |title=''Syntomaspis druparum'', the apple-seed chalcid |journal=Journal of Agricultural Research |year=1916 |volume=7 |pages=487–502 |url=https://naldc.nal.usda.gov/download/IND43965627/pdf}}</ref> Some also inject a mix of secretory products that paralyse the host or protect the egg from the host's immune system; these include [[polydnavirus]]es, ovarian proteins, and venom. If a polydnavirus is included, it infects the nuclei of host hemocytes and other cells, causing symptoms that benefit the parasite.<ref name="MillerBall1998">{{cite book |author1=Miller, Lois K. |author2=Ball, Laurence Andrew |title=The insect viruses |url=https://books.google.com/books?id=QAwsTrfwSgMC |year=1998 |publisher=Springer |isbn=978-0-306-45881-1}}</ref><ref>{{Cite journal |last1=Strand |first1=Michael R. |last2=Burke |first2=Gaelen R. |date=May 2015 |title=Polydnaviruses: From discovery to current insights |journal=Virology |volume=479-480 |pages=393–402 |doi=10.1016/j.virol.2015.01.018 |pmc=4424053 |pmid=25670535}}</ref> {{multiple image
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Host size is important for the development of the parasitoid, as the host is its entire food supply until it emerges as an adult; small hosts often produce smaller parasitoids.<ref>{{cite journal |last1=Cohen |first1=J. E.|last2=Jonsson |first2=T. |last3=Muller |first3=C. B. |last4=Godfray |first4=H. C. J. |last5=Savage |first5=V. M. |title=Body sizes of hosts and parasitoids in individual feeding relationships |journal=Proceedings of the National Academy of Sciences|date=12 January 2005 |volume=102 |issue=3 |pages=684–689 |doi=10.1073/pnas.0408780102|pmid=15647346|bibcode=2005PNAS..102..684C|pmc=545575 |doi-access=free}}{{oa}}</ref> Some species preferentially lay female eggs in larger hosts and male eggs in smaller hosts, as the reproductive capabilities of males are limited less severely by smaller adult body size.<ref>{{cite journal |last1=Jones |first1=W. Thomas |title=Sex Ratio and Host Size in a Parasitoid Wasp |journal=Behavioral Ecology and Sociobiology |date=1982 |volume=10 |issue=3 |pages=207–210 |jstor=4599484 |doi=10.1007/bf00299686|s2cid=28101144 }}</ref>
[[File:Hornworm with parasitic wasp coccoons.jpg|alt=Hornworm with parasitic wasp cocoons|thumb|Hornworm with parasitic wasp cocoons]]
Some parasitoid wasps mark the host with chemical signals to show that an egg has been laid there. This may both deter rivals from ovipositing, and signal to itself that no further egg is needed in that host, effectively reducing the chances that offspring will have to compete for food and increasing the offspring's survival.<ref name="CouchouxSeppä2015">{{cite journal |last1=Couchoux |first1=Christelle |last2=Seppä |first2=Perttu |last3=van Nouhuys |first3=Saskya |title=Behavioural and genetic approaches to evaluate the effectiveness of deterrent marking by a parasitoid wasp |journal=Behaviour |volume=152 |issue=9 |year=2015 |pages=1257–1276 |doi=10.1163/1568539X-00003277}}</ref><ref name="NufioPapaj2001">{{cite journal |last1=Nufio |first1=César R. |last2=Papaj |first2=Daniel R. |title=Host marking behavior in phytophagous insects and parasitoids |journal=Entomologia Experimentalis et Applicata |volume=99 |issue=3 |year=2001 |pages=273–293 |doi=10.1046/j.1570-7458.2001.00827.x|doi-access=free }}{{oa}}</ref>
=== Life cycle ===
[[File:Potter Wasp building mud nest near completion.JPG|thumb|[[Potter wasp|Potter wasp (Eumeninae)]], an idiobiont, building mud nest; she will then [[mass provisioning|provision it]] with paralysed insects, on which she lays her eggs; she then seals the nest and provides no further care for her young.]]
On or inside the host the parasitoid egg hatches into a larva or two or more larvae ([[polyembryony]]). Endoparasitoid eggs can absorb fluids from the host body and grow several times in size from when they were first laid before hatching. The first [[instar]] larvae
[[File:Pdv-host.svg|thumb|upright=1.4|[[Polydnavirus]]-wasp [[Mutualism (biology)|mutualism]]: the virus protects koinobiont wasp eggs and larvae from [[immune system|immune suppression]] by the host's [[hemocyte]]s.]]
=== Mutualism with polydnavirus ===
{{main|Polydnavirus}}
[[Polydnavirus]]es are a unique group of insect viruses that have a mutualistic relationship with some parasitic wasps. The polydnavirus replicates in the oviducts of an adult female parasitoid wasp. The wasp [[Mutualism (biology)|benefits from this relationship]] because the virus provides protection for the parasitic larvae inside the host, (i) by weakening the host's immune system and (ii) by altering the host's cells to be more beneficial to the parasite. The relationship between these viruses and the wasp is obligatory in the sense that all individuals are infected with the viruses; the virus has been incorporated in the wasp's genome and is inherited.<ref>{{cite journal |
== Host defenses ==▼
▲==Host defenses==
[[File:Parasitoid wasp pointing ovipositor at cinnabar moth larva.jpg|thumb|left|upright|Parasitoid wasp ([[Ichneumonidae]]) pointing ovipositor at [[cinnabar moth]] larva, just after ovipositing. The larva wriggles vigorously to try to avoid the attack.]]
The hosts of parasitoids have developed several levels of defence. Many hosts try to hide from the parasitoids in inaccessible habitats. They may also get rid of their [[frass]] (body wastes) and avoid plants that they have chewed on as both can signal their presence to parasitoids hunting for hosts. The egg shells and cuticles of the potential hosts are thickened to prevent the parasitoid from penetrating them. Hosts may use behavioral evasion when they encounter an egg laying female parasitoid, like dropping off the plant they are on, twisting and thrashing so as to dislodge or kill the female and even regurgitating onto the wasp to entangle it. The wriggling can sometimes help by causing the wasp to "miss" laying the egg on the host and instead place it nearby. Wriggling of pupae can cause the wasp to lose its grip on the smooth hard pupa or get trapped in the silk strands. Some caterpillars even bite the female wasps that approach them. Some insects secrete poisonous compounds that kill or drive away the parasitoid. Ants that are in a symbiotic relationship with caterpillars, aphids or scale insects may protect them from attack by wasps.<ref name=Strand1995>{{Cite journal |
Hosts can kill endoparasitoids by
Certain caterpillars eat plants that are toxic to both themselves and the parasite to cure themselves.<ref>{{Cite journal |
== Evolution and taxonomy ==
=== Evolution ===
Based on genetic and fossil analysis, parasitoidism has evolved only once in the Hymenoptera, during the [[Permian]], leading to a single [[clade]]
The [[phylogenetic tree]] gives a condensed overview of the positions of parasitoidal groups ('''boldface'''), amongst groups (''italics'') like the Vespidae which have secondarily abandoned the parasitoid habit. The approximate numbers of species estimated to be in these groups, often much larger than the number so far described, is shown in parentheses, with estimates for the most populous also shown in '''boldface''', like "('''150,000''')". Not all species in these groups are parasitoidal: for example, some Cynipoidea are [[phytophagous]].
{{clade |
|label1=[[Hymenoptera]]
|1={{clade
Line 85 ⟶ 95:
|label2='''[[Apocrita]]''' |sublabel2=''wasp waist''
|2={{clade
|1='''[[Ichneumonoidea]]''' ('''150,000''') [[File:Ichneumon wasp (Ichneumonidae sp) female (cropped).jpg|80px
|2={{clade
|1={{clade
Line 100 ⟶ 110:
|1= '''[[Chrysididae]]''' (jewel wasps, 3000) [[File:Chrysididae jewel wasp.jpg|60px]]
|2={{clade
|1='''[[Vespidae]]''' (wasps, hornets, 5000)
|2={{clade
|1={{clade
Line 110 ⟶ 120:
|1='''[[Scoliidae]]''' (560) [[File:Black-Flower-Wasp.jpg|90px]]
|2={{clade
|1='''[[Formicidae]]''' (ants, 22,000)
|label2=[[Apoidea]]
|2={{clade
|1='''[[Sphecidae]]''' (700) [[File:Specimen of Podalonia tydei (Le Guillou, 1841).jpg|60px]]
|2={{clade
|1='''[[Bembicinae|Bembicidae]]''' (1800) [[File:Bembix sp.jpg|60px]]
|2={{clade
|1=other families
|2={{clade
|1={{clade
|1='''[[
|2='''[[Philanthinae|Philanthidae]]''' (1100) [[File:Dorsal view cerceris.jpg|60px]]
}}
|2={{clade
|2='''[[Ammoplanidae]]''' (aphid wasps, 130)
}}
▲ |2=''[[Anthophila]] (bees, 22,000)'' [[File:Apis mellifera (in flight) (cropped).jpg|60px]]
}}
}}
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===Taxonomy===
[[File:Trissolcus on Chinavia eggs.jpg|thumb|''[[Trissolcus]]'' (family Platygastridae) on ''[[Chinavia]]'' eggs]]
[[File:Housefly pupae killed by wasp larvae.jpg|thumb|[[Housefly]] pupae killed by parasitoid wasp larvae (probably [[Pteromalidae]]). Each pupa has one hole through which a single adult wasp has emerged after feeding on the housefly larva.]]
The parasitoid wasps are [[paraphyletic]] since the [[ant]]s, [[bee]]s, and non-parasitic wasps such as the [[Vespidae]] are not included, and there are many members of mainly parasitoidal families which are not themselves parasitic. Listed are Hymenopteran families where most members have a parasitoid lifestyle.<ref>{{Cite book |title=Hymenoptera of the world : an identification guide to families |editor-last1=
{{div col|colwidth=22em}}
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===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]][[File:CSIRO ScienceImage 2357 Spotted alfalfa aphid being attacked by parasitic wasp.jpg|thumb|''Trioxys complanatus'', ([[Aphidiidae]]) ovipositing into a spotted alfalfa [[aphid]], a commercial pest in Australia.{{efn|''Trioxys complanatus'' 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}}</ref>}}]]▼
[[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]]
▲
{{further|Biological pest control}}
Parasitoid wasps are considered beneficial as they naturally control the population of many [[pest insect]]s. They are widely used commercially (alongside other parasitoids such as [[Tachinidae|tachinid flies]]) for [[biological pest control]], for which 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.<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>
One of the first parasitoid wasps to enter commercial use was ''[[Encarsia formosa]]'', an endoparasitic [[Aphelinidae|aphelinid]]. It has been used to control whitefly in [[greenhouse]]s since the 1920s. Use of the insect fell almost to nothing, replaced by [[chemical pesticide]]s by the 1940s. Since the 1970s, usage has revived, with renewed usage in Europe and Russia.<ref name="HoddleVan Driesche1998">{{cite journal |last1=Hoddle |first1=M. S. |last2=Van Driesche |first2=R. G. |last3=Sanderson|first3=J. P.|title=Biology and Use of the Whitefly Parasitoid Encarsia Formosa |journal=Annual Review of Entomology |volume=43 |issue=1 |year=1998 |pages=645–669 |doi=10.1146/annurev.ento.43.1.645|pmid=15012401 }}</ref> In some countries, such as New Zealand, it is the primary biological control agent used to control [[greenhouse]] whiteflies, particularly on crops such as [[tomato]], a particularly difficult plant for predators to establish on.<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 parasitoids for different crops.<ref name=smith>{{cite journal |
===In culture===
Parasitoid wasps influenced the 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
==Notes==
{{notelist}}
== References ==
{{reflist|30em}}
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