The red admiral (Vanessa atalanta) is a familiar butterfly, and is easy to identify thanks to its striking patterning; the black forewings feature prominent red bars and white spots. The undersides of the hindwings are delicately patterned with brown and black (1), which provides excellent camouflage when this butterfly is roosting on tree trunks (2). The caterpillar grows to 3.5 centimetres in length, and occurs in a number of forms of varying colour. Dark forms are greyish-black, and have black spines and yellow patches along each side. Various pale forms also occur; they are either green or yellowish with pale spines and black markings (3).
Red admirals arriving in Britain following migration have usually mated before commencing their journey. Those that have overwintered in Britain mate after emergence.
Females lay their eggs singly on nettle leaves, and after about a week the eggs hatch (3). The caterpillars create a tent-like shelter from nettle leaves, in which they feed and pupate(3). The adults emerge after two to three weeks (3); they either hibernate or migrate southwards towards the end of summer. In southern Britain, it has been discovered that eggs and caterpillars are able to survive the winter, and emerge in the adult form in spring (2).
This common migratory species has a wide distribution throughout Britain. Adults emerge after hibernation in January and March, and are joined by butterflies that have migrated from North Africa and southern Europe between May and August. As the summer progresses, further immigrants arrive from Spain and Portugal, and later still from central Europe and France (2). After mid-August red admirals in Britain begin to move southwards and the majority spend the winter in warmer climes (2). Globally, this butterfly has a wide distribution, and is known across central and southern Europe, Asia, North Africa and North America (2).
Occurs in a huge range of habitats, usually where the most important caterpillar foodplant, the common nettle (Urtica dioica) occurs (2). Adults are often seen in gardens feeding on nectar on buddleias (such as Buddleja davidii), or feeding on rotten fruit (2).
A winter survival strategy characteristic of some mammals in which an animal's metabolic rate slows down and a state of deep sleep is attained. Whilst hibernating, animals survive on stored reserves of fat that they have accumulated in summer. In insects, the correct term for hibernation is 'diapause', a temporary pause in development and growth. Any stage of the lifecycle (eggs, larvae, pupae or adults) may enter diapause, which is typically associated with winter.
The process of forming a pupa, the stage in an insect's development, when huge changes occur that reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.
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