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Butterfly Conservation- Glasgow & South West Scotland Branch

Speckled Wood (Pararge aegeria)

Description

The Speckled Wood is a medium sized chocolate and cream-coloured woodland butterfly (wingspan 46-56 mm). The females are larger than the males with larger creamy-white patches and eyespots on their wings. The pale spotted oblita form found in Argyll in South West Scotland is larger than the yellow-orange spotted tircis form found in England. The wings of freshly emerged individuals have a beautiful sheen as they bask in sunny woodland glades or sun-dappled forest gullies.

Credit: Scott Shanks
Credit: Scott Shanks
Credit: Scott Shanks

Life Cycle

The Speckled Wood tends to emerge in late April or early May in Scotland and fly until September with two broods. Males defend temporary territories in sunny glades or near sunspots on woodland paths that they use to bask, briefly chasing off intruding males. Females tend to spend most of their time in the canopy of trees such as ash, oak and alder, where both sexes feed on aphid honeydew left on leaves. Following mating the females seek out warm sheltered areas where the pale yellow eggs are laid singly on the leaves of a variety of grasses. Suitable grasses include false brome (Brachypodium sylvaticaum), Cockís foot (Dactylis glomerata) and common couch grass (Elytrigia repens). Later broods in high summer may use grasses in shadier spots within the woodland. The pale green caterpillars are well camouflaged while they feed from the underside of the grass blades. The green pupa is formed near the base of the food plant or on nearby vegetation. The later broods of Speckled Wood may overwinter as either a larva or pupa, with the larvae awakening to feed on milder days when they can. The larval development rates vary with temperature and their location, so emergence after pupation can be quite variable.

Flight Times

In South West Scotland the Speckled Wood can be seen on the wing from late April through to September, with population peaks in late May, mid July and early September.

Habitat & Distribution in SW Scotland

Distribution map 2010

The Speckled Wood can be found in open deciduous woodland, rides along conifer plantations and along hedgerows & roads. It is the only British butterfly which seems to prefer the shady habitat provided by trees and is a therefore a species which can benefit from a lack of woodland management unlike the Pearl-bordered Fritillary & Chequered Skipper which require open sunny glades to survive. Indeed, Speckled Wood numbers tend to increase in cooler wetter summers and decline in drier warmer summers. The Speckled Wood can be encouraged to breed in urban locations by leaving tall grass in shady areas of parks or gardens.

The Speckled Wood has a very curious distribution in Scotland with a western population on mainland Argyll and on some of the western isles including Mull, Jura, Colonsay & further south on Arran and a northern population around the Moray Firth. Both these populations have been expanding in recent years with particularly dramatic expansions of the northern population into Moray & Aberdeenshire, Lochaber, Loch Ness-side and north into Caithness & Sutherland. There are even a few colonies in Perthshire suggesting it has flown over the Grampians to establish new colonies.

The Speckled Wood in South West Scotland is mainly confined to Argyll and its Islands, with colonies recorded down to the Isle of Arran and a few colonies in Dumfries & Galloway near Stranraer. However, the woodland of the central lowlands and around Loch Lomond ought to be perfect habitat for the Speckled Wood but the lack of suitable habitat between western Argyll and north Loch Lomond may be a barrier which the butterfly cannot cross - the eastern most population in Argyll is on the lower slopes of Ben Cruachan.

The Speckled Wood was more widespread in the 19th century being found in much of eastern Scotland from the borders in the south, around Edinburgh, in Perthshire and north to Aberdeen. However, it was not known from the central Highlands and north in to the Moray Firth such that there were well-separated eastern and western populations. By the late 19th century, the Speckled Wood was in decline in Scotland and the eastern populations became extinct in the early 20th century. Indeed, this occurred throughout the British Isles with Speckled Wood populations becoming restricted to south-west England, lowland Wales & western Scotland. It is thought that the eastern populations in Scotland were of the tircis sub species which occurs in England which would explain why these populations died out like those in England but the oblita populations in Argyll persisted. In recent decades, the tircis sub species has been expanding dramatically northwards into the far north of England with a few scattered records into southern Scotland so it can now be said that the tircis sub-species has arrived back in Scotland

References

  • Barbour, D., Moran, S, Mainwood, T & Slater, B 2008. Atlas ofr Butterflies in Highland & Moray. Big Sky.
  • Futter, K., Sutcliffe, R., Welham, D., Welham, A., Rostron, A., MacKay, J., Gregory, N., McCleary, J., Tait, T., Black, J. & Kirkland, P. 2006. Butterflies of South West Scotland. Argyll Publishing. (see Atlas page)
  • Asher, J., Warren, M, Fox, R., Harding, P., Jeffcoate, G., Jeffcoate, S. 2001. The Millennium Atlas of Butterflies in Britain & Ireland. Oxford University Press.
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  • Fox, R., Asher, J., Brereton, T., Roy, D., Warren, M. 2006. The State of Butterflies in Britain and Ireland. Pisces Publications.
  • Thomson, G. 1982. The Butterflies of Scotland. Croom Helm London.
  • Tomlinson, D. & Still, R. 2002. Britainís Butterflies. WILDGuides.

Written by Scott Shanks & Andrew Masterman


 
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