The forewings of the scarce Square-spotted Clay moth vary in colour from pale reddish brown to almost black (4), and the hindwings are generally paler (5). The velvety caterpillar grows to a maximum of 38 mm in length (6), is purplish- brown with darker brown chevrons, and has a bright white line passing along the side (4). Below this line the caterpillar is a rosy pink, giving a two-tone effect. The final stage of the caterpillar (the last 'instar') is more uniformly coloured (6).
One generation is produced each year (1), adults fly at night (3) in July and August and can be seen feeding from the flowers of burdock (Arctium spp.). Unlike other members of this genus, the caterpillars of this species are unusual in that they do not climb shrubs and trees in spring (2). Instead they are present on low plants, especially stinging nettles (Urtica dioica) between September and May, and can be found after overwintering (2). They burrow into the soil a few weeks before the pupal stage develops (1).
This moth has a wide distribution in Britain (6), and occurs more widely than formerly thought (6); indeed it is fairly common in parts of East Anglia (6). It can be found in England and Wales, and reaches as far north as Morayshire (3). Elsewhere it is found in hilly areas of Europe from the Pyrenees and becomes increasingly common further north. The species occurs as far east as Italy, Sicily and Greece and is also known in Turkey and parts of Iran (3).
Found in a broad variety of habitats, including open meadows next to gravel workings, scattered copses, ancient woodland with a coppiced understory, emergent forest and mixed conifer woodlands with an understory of broadleaved trees (6).
The species currently occurs within a number of protected areas such as nature reserves and Sites of Special Scientific Interest (SSSIs). Targeted as a priority for conservation action by the UK Biodiversity Action Plan, the Square-spotted Clay is the subject of a Species Action Plan, which aims to maintain all current populations as well as enhance these populations by 2010 (3). Possible conservation action may include managing all occupied sites in ways beneficial to this moth, as well as increasing the area of suitable habitat available in areas next to occupied sites. This may also facilitate the linking of fragmented patches of habitat (3).
Coppicing is a traditional form of woodland management in which trees are cut close to the base of the trunk. Re-growth occurs in the form of many thin poles. Coppiced woodlands are cut in this way on rotation, producing a mosaic of different stages of re-growth.
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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