The Peacock butterfly (Inachis io) is one of the most easy to recognise with its large eye like coloured makings. It is one of the ‘Aristicrat’ family. It is common throughout the UK and has enjoyed an increase in numbers over the last few years possibly helped by the warming climate in the UK. Some Peacock adults hibernate throughout the winter and can be seen as early as March if the weather is warm. By May eggs can be found on the underside of stinging nettles but as the climate warms they may start to appear even earlier. This plant is the main food source of the caterpillar which is black with white spots and has soft spines emerging from each of its body segments. There may be dozens of caterpillars on a plant where they weave a kind of web for protection. They have voracious appetites and soon consume the leaves on which the eggs were laid moving on to find fresh ones. After a few days the damage they cause to the plant and the webs they spin for protection are quite easy for predators to see.
Many of the caterpillars fall victim to parasitic wasps and flies like the Ichneumon fly (Apanteles glomeratus) which is actually a wasp which is widespread and can some years account for the deaths of up to eighty percent of all caterpillars. These predators lay their own eggs inside the caterpillars where they eat it alive then hatch out through the skin forming a row of pupa along both sides of the corpse. Providing the caterpillar survives it will pupate and hatch out into a beautiful Peacock butterfly. If the weather is warm enough to allow the new butterflies to mature quickly enough there may be a second brood as late as August. The butterflies from this second brood along with some from the first will overwinter in hibernation making them the longest lived butterflies as some will have a lifespan of almost a full year.
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