TheEuropean Peacock(Inachis io), more commonly known simply as thePeacockbutterfly, is a colourfulbutterfly, found inEuropeand temperateAsiaas far east asJapan. Classified as the only member of thegenusInachis(the name is derived from Greek mythology, meaningIo, the daughter ofInachus). It should not be confused or classified with the "American peacocks" in the genusAnartia; these are not close relatives of the Eurasian species. The Peacock butterfly is resident in much of its range, often wintering in buildings or trees. It therefore often appears quite early in spring. The Peacock butterfly has figured in research where the role of eye-spots as an anti-predator mechanism has been investigated.[1]

In the British Isles, the butterfly is found inEngland,Scotland(includingOrkneyandShetland),Wales, andIreland. The Peacock is expanding its range[2][3]and is not known to be threatened.[2]

Characteristics

The butterfly has a wingspan of 50 to 55mm. The base-colour of the wings is a rusty red, and at each wingtip it bears a distinctive, black, blue and yelloweyespot. The underside is a cryptically coloured dark-brown or black. There are twosubspecies,I. io caucasica(Jachontov, 1912) found inAzerbaijanandI. io geisha(Stichel, 1908) found in Japan and theRussian Far East.

Natural history

The Peacock can be found in woods, fields, meadows, pastures, parks, and gardens, and from lowlands up to 2,500 metres (8,200ft) elevation. It is a relatively common butterfly seen in many European parks and gardens. The Peacock male exhibits territorial behaviour, in many cases territories being selected en route of the females to oviposition sites.[4]

The butterflyhibernatesover winter before laying its eggs in early spring, in batches of up to 400 at a time.[3]The eggs are ribbed and olive-green in colour and laid on the upper parts, and, the undersides of leaves ofnettleplants[5]andhops. Thecaterpillars, which are shiny black with six rows of barbed spikes and a series of white dots on each segment, and which have a shiny black head, hatch after about a week. The chrysalis may be either grey, brown, or green in colour and may have a blackish tinge.[5]Thecaterpillarsgrow up to 42mm in length.

The recorded foodplants of the European Peacock areStinging Nettle(Urtica dioica),Hop(Humulus lupulus), and the Small Nettle (Urtica urens).[3]

The adult butterflies drink nectar from a wide variety of flowering plants, includingbuddleia,willows,dandelions, wildmarjoram,danewort,hemp agrimony, andclover; they also utilize tree sap and rotten fruit.

Behavior

Mating system and territorial behavior

Inachis ioemploys amonandrousmating system, which means that they only mate with one partner for a period of time. This is due to their life cycle in which female are receptive only available during aneclosionperiod, afteroverwintering. The pairs only mate once after overwintering, as it is very difficult to find a receptive female after that period.[6]In species where the range of the females is not defensible by a male, the males must defend a single desirable area that females will come through, such as dense food areas, watering holes, or favorable nesting sites. The males then attempt to mate with the females as they are passing through. Holding a desirable territory increases the male’s likelihood of finding a mate and therefore increases his reproductive success. However, each individual needs to weigh the benefits of mating with the costs of defending a territory.[7]Inachis ioexhibits this type of territorial behavior, and must defend a desirable territory from other males. If only one of the males knows the territory well, he will successfully chase off any intruders. On the other hand, if both males are familiar with the territory, there will be a contest between the two to determine which of them stays in the territory. The most desirable sites are those that will increase the male’s quota of females. These sites are generally feeding and oviposition sites, which are sough after by females. This territorial behavior is reinforced by the fact that these sites are all concentrated. If the valuable resources were dispersed, there would be less observable territorial behavior.[8]In order to find mates and defend their territory,Inachis ioexhibits perching behavior.The male butterflies will perch on an object at a specific height where they can observe passing flying objects. Every time they see a passing object of their own species or of a relevant species, they will fly straight towards the object until they are approximately 10cm away. If they encounter a male, the resident male will chase him off his territory. If the resident male encounters a female, he will pursue her until she lands and mating will occur.[9]The courtship is extended in this species. The male goes through a long chase before the female allows him to mate. He must demonstrate high performance flight.[10]

The monandrous mating system has caused the evolution of a shorter life span in males of this species. Inpolygynousbutterflies, the male’s reproductive success is largely dependent on life span. Therefore, the longer a male lives, the more he can reproduce, so he has a higher fitness. Therefore, males tend to live as long as the females. InInachis iothe synchronous eclosion at the end of winter cause males to only mate once. Their reproductive success is therefore not linked to how long they live, and there is no selective pressure to live longer. Therefore, the life span of males is shorter than the lifespan of the females.[6]

Anti-predator defense mechanisms

The Peacock butterfly’s mainanti-predator defense mechanismcomes from the four largeeyespotsthat it has on its wings. These eyespots are brilliantly colored concentric circles. Like many other butterflies thathibernate, the Peacock butterfly exhibits many lines of defense against would-be predators. Avian predators of the butterfly includeblue tits, pied flycatchers and other smallpasserinebirds. The first line of defense against these predators for many hibernating butterflies iscrypsis, a process in which the butterflies blend into their environment by mimicking a leaf and staying immobile.[11]Some hibernating butterflies such as the Peacock have a second line of defense: when attacked, they open their wings, expose their eyespots and perform an intimidating display of threat.[11]The intimidating visual display shown by the Peacock butterfly gives it a much better chance at escaping predators than butterflies that rely solely on leaf mimicry.[11]While the main targets of these anti-predation measures are small passerine birds, even larger birds such as chickens have been shown to react to the stimuli and avoid the butterfly when exposed to eyespots.[12]

Avian predators

Research has shown that avian predators attempting to attack a butterfly hesitate for a much longer time if they encounter butterflies that display their eyespots than if they encounter butterflies whose eyespots are covered. In addition, the predators delay their return to the butterfly if it displays eyespots[12][13]and some predators even flee before attacking the butterfly.[13]By intimidating the predator so that it delays or gives up its attack, the Peacock butterfly has a much greater chance of escaping predation.

According to the eye mimicry hypothesis, the eyespots serve an anti-predatory purpose by imitating the eyes of the avian predators' natural enemies.[12]In contrast, the conspicuousness hypothesis posits that rather than recognition of the eyespots as belonging to an enemy, the conspicuous nature of the eyespots, which are typically large and bright, causes a response in the visual system of the predator that leads to avoidance of the butterfly.[14]

In one experiment, observed responses of the avian predators to the eyespots included increased vigilance, a delay in their return to the Peacock butterfly, and the production ofalarm callsassociated with ground-based predators.[12]These responses to the eyespot stimuli lend support to the eye mimicry hypothesis as they indicated that the avian predator sensed that the eyespots belonged to a potential enemy. When faced with avian predators like the blue tit, the Peacock butterfly makes a hissing noise as well as threateningly displaying its eyespots. However, it is the eyespots that protect the butterfly the most; Peacock butterflies that have had their sound production capability removed still defend themselves extremely well against avian predators if their eyespots are present.[15]

Rodent predators

While hibernating in dark wintering areas, the Peacock butterfly frequently encountersrodentpredators such as smallmice. Against these predators, however, the visual display of eyespots is ineffective due to the darkness of the environment. Instead, these rodent predators show a much stronger adverse reaction to the butterfly when it is producing its auditory hissing signal. This indicates that for rodent predators, it is the auditory signal produced by the butterfly that serves as a deterrent.[16]

PO POLSKU

Rusałka pawik(Inachis io) –gatunekmotylaz rodzinyrusałkowatych. Występuje w Azji i Europie po Japonię[1], w Polsce jest jednym z najbardziej pospolitych motyli.

Morfologia

Długość ciała 35 mm, rozpiętość skrzydeł 50–55 mm. Ma skrzydła ubarwione w intensywnie brązowo-czerwonym kolorze. Najbardziej charakterystyczną cechą tego gatunku, po której łatwo odróżnić go od innych gatunków motyli są duże, wielokolorowe (niebiesko-czarne) plamki („pawie oczka”) na końcach przednich i tylnych skrzydeł. Plamki te to mechanizm obronny; imitując oczy mają zasugerować ewentualnemu napastnikowi, że czai się tutaj groźny drapieżnik[1].

Siedlisko

Występuje na polanach i skrajach lasów, w ogrodach, sadach, na nieużytkach i w wielu innych miejscach. Wszędzie jest bardzo pospolita. Postać dorosła występuje przez całe lato, można ją spotkać na różnych kwiatach, z których spija nektar.

Rozwój

  • Postać dorosła. Zazwyczaj w ciągu jednego roku występują 2 pokolenia, a jedynie na obszarach o cięższym klimacie i wyżej w górach jedno pokolenie. Zimuje w różnego rodzaju kryjówkach, preferuje wilgotne i ciemne miejsca, np. jaskinie, szczeliny w skałach, nory ssaków.Okres godowyprzypada na wiosnę, potem drugi raz w lecie.
  • Jaja. Zapłodniona samica składa jaja na spodniej stronie liścipokrzyw. Są one delikatnie żeberkowane i tworzą duże pakiety.
  • Larwa. Wylęgające się z jaj po 2–3 tygodniach zielonkawobiałegąsieniceo długości 2–3 mm mają czarną, błyszczącą głowę. Od razu przystępują do żerowania, po kilku dniachliniejąi wspólnie okrywają całą pokrzywę dużym białymoprzędem. Dorosłe gąsienice mają na grzbiecie rozgałęzione, długie kolce, a całe ich ciało pokryte jest białymi kropkami. Po 3–4 tygodniach od wylęgu opuszczają roślinę, na której żerowały i szukają kryjówek, np. na gałązkach innych roślin, szczelinach w korze, drewnie lub murze, itp. Gąsienica wykonuje nieduży oprzęd, do którego przyczepia się ostatnią parą odnóżyodwłokowychi lekko wygięta zawisa głową w dół.
  • Poczwarka.Przepoczwarczenietrwa kilka dni. Już po 1–2 dniach nieruchomego zawisu pęka jej skóra na grzbiecie i stopniowo wyłania siępoczwarka. Falistymi skurczami zsuwa onaoskórekgąsienicy do tyłu. Teraz następuje najtrudniejszy dla niej moment: wydobycie z oskórka zakończonego haczykiem końca ciała i zaczepienie tym kolcem o oprzęd. Poczwarka wygina się tak długo, aż pozbędzie się oskórka. Przez następne 2 tygodnie jest nieruchoma, otoczona własnym oskórkiem i zachodzą w niej bardzo duże zmiany w budowie narządów wewnętrznych i zewnętrznej budowie ciała. W tym czasie przeobraża się wpostać dorosłą– motyla ze skrzydłami. Gdy to nastąpi, w ciągu kliku sekund motyl wyślizguje się z dolnej części oskórka i rozprostowuje skrzydła pompując do ich żyłekhemolimfę.