Adult large heath butterflies always have their wings closed when at rest; males are smoky orange-brown in colour, and females are paler (1). Both sexes have pale brown undersides featuring a creamy white band and a number of eyespots (1). The green caterpillar is around 2.5 centimetres in length and has two white bands along its sides (3).
The flight period occurs between mid-June and early August. The large heath is single-brooded; eggs are laid singly at the base of the foodplant on dead stems. The larvaehibernate when still small, and emerge in March to complete their development (2). Pupae develop towards the end of April or early May and are attached to stems. Adults emerge around a month later (3).
Found in Europe, Asia, Canada and western USA, the large heath has undergone serious declines throughout much of Europe. In Britain, it is largely restricted to Scotland and the far north of England with a few small populations persisting in central and eastern England (2) and north Wales (4).
Inhabits wet, boggy habitats such as lowland raised bogs, upland blanket bogs and damp acidic moorland where the main foodplant, hare's tail cottongrass (Eriophorum vaginatum) occurs (2). Abundant sources of the most important adult nectar source, cross-leaved heath (Erica tetralix) are also essential (2).
Huge losses of suitable habitat have occurred throughout Europe as a result of large-scale drainage works, commercial forestry plantations and peat extraction. Inappropriate habitat management, such as overgrazing, may be degrading once suitable habitat and causing losses (2).
Lowland raised bogs and blanket bogs are listed under the EC Habitats Directive, and peatland habitats have been the focus of a number of conservation campaigns. Despite this, peat is still extracted for use in gardens and in horticulture. As large populations of species are more resistant to local extinctions, it is important that large areas of remaining habitats must be conserved and suitable management practices encouraged. Homeowners can help by choosing to use peat-free alternatives in their gardens (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.
Stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
Stage in an insect's development when huge changes occur, which reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.
Also known as ‘univoltine’. Referring to an organism which has just one brood each year.
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