Aglais io, the European peacock, or the peacock butterfly, is a colourful butterfly, found in Europe and temperate Asia as far east as Japan. It was formerly classified as the only member of the genus Inachis (the name is derived from Greek mythology, meaning Io, the daughter of Inachus). It should not be confused or classified with the "American peacocks" in the genus Anartia; while belonging to the same family as the European peacock, Nymphalidae, the American peacocks 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 in which the role of eyespots as an anti-predator mechanism has been investigated. The peacock is expanding its range and is not known to be threatened.
Characteristics
The butterfly has a wingspan of . The base colour of the wings is a rusty red, and at each wingtip it bears a distinctive, black, blue and yellow eyespot. The underside is a cryptically coloured dark brown or black.
There are two subspecies: A. io caucasica (Jachontov, 1912), found in Azerbaijan, and A. io geisha (Stichel, 1908), found in Japan and the Russian Far East.
Natural history
The peacock can be found in woods, fields, meadows, pastures, parks, and gardens, from lowlands up to 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.
The butterfly hibernates over winter before laying its eggs in early spring, in batches of up to 400 at a time. The olive green eggs are ribbed. They are laid on both the upper parts and the undersides of leaves of nettle plants and hops. The caterpillars hatch after about a week. They are shiny black with six rows of barbed spikes and a series of white dots on each segment. The chrysalis may be either grey, brown or green, and may have a blackish tinge. The caterpillars grow up to in length.
The recorded food plants of the European peacock are stinging nettle (Urtica dioica), hop (Humulus lupulus), and the small nettle (Urtica urens).
The adult butterflies drink nectar from a wide variety of flowering plants, including buddleia, willows, dandelions, wild marjoram, danewort, hemp agrimony, and clover; they also use tree sap and rotten fruits.
Behaviour
Mating system and territorial behaviour
Aglais io employs a monogamous mating system, which means that they only mate with one partner for a period of time. This is due to their life cycle in which females are receptive only during an eclosion period, after overwintering. The pairs only mate once after overwintering, as it is very difficult to find a receptive female after that period. 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 favourable 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. Aglais io exhibits this type of territorial behaviour, 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 sought after by females. This territorial behaviour is reinforced by the fact that these sites are all concentrated. If the valuable resources were dispersed, there would be less observable territorial behaviour.