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Butterfly Conservation- Glasgow & South West Scotland Branch


Clouded Yellow (Colias croceus)

Description

The Clouded Yellow is a beautiful orange-yellow and black migratory butterfly (wingspan 52-62 mm). From a distance the lemon-yellow underwings could be confused with a brimstone (not resident in SW Scotland) or yellow forms of Small White or Green-Veined White, but on closer inspection this butterfly is unmistakeable. The upperwings are a rich orange-yellow with a thick trim of black along the edges. There is a black spot on the forewing and an orange spot on the hindwing. The underwings are edged with pink and there are pink or black spots along the outer edge. The hindwing has a distinctive pair of white spots surrounded by a halo of pink. The front of the head and antennae are also pink while the eyes are a brilliant green. Approximately 10% of females are of the form Helice where the upper surface is pale lemon-yellow or even white. Numbers of Clouded Yellows reaching south west Scotland from southern Europe and north Africa varies enormously each year.

Credit: Jim Black
Credit: Jim Black
Credit: Keith Warmington

Life Cycle

Our winter conditions prevent the Clouded Yellow from becoming resident. Each year gregarious waves of Clouded Yellows spread out from breeding grounds in the North of Africa or Southern Europe and make their way Northwards, breeding as they go. In most years, a few migratory individuals arrive in south west Scotland about mid June. The females make use of a range of leguminous plants such as clovers (Trifolium Spp), Lucerne (Medicago sativa) and Birds-foot trefoil (Lotus corniculatus) on which to lay their eggs. The pearly-white rugby ball-shaped eggs are laid singly on the upper surface of the leaves of the food plant. The yellow-striped green caterpillar grows rapidly and forms a yellow-striped green pupa on a stem of the food plant. The adults emerge in August & September and may be joined from further migrants.

Flight Times

Adults can be found on the wing from mid June through to mid October, with numbers peaking in late August and September.

Habitat & Distribution in SW Scotland

Distribution map 2010

The Clouded Yellow is much less common in Scotland than the other migrants, the Red Admiral & the Painted Lady, but is more commonly seen around the coasts of SW Scotland than in NW Scotland. However, individuals have been seen in the northern and western Isles. Years such as 1877, 1900, 1947, 1992, 1998, 2000 and 2006 were notable for the large numbers of migrant Clouded Yellows that reached Scotland with subsequent breeding giving large populations in August & September.

The Clouded Yellow can potentially be found throughout south west Scotland, but like other migratory butterflies it is more commonly found along the coast. The adults are highly mobile and donít form colonies but they travel widely over the countryside looking for breeding sites and occasionally stopping to nectar at thistles, composites or clovers. If large groups of Clouded Yellows are seen at inland sites it can be assumed that they are from recently-emerged locally-bred population.

There is a strong drive for Clouded Yellows to migrate northwards from their permanent breeding grounds in North Africa & Southern Europe during spring and summer but numbers are always much larger in southern counties of England than further north. In the autumn, smaller groups have been observed migrating southwards. In late summer the locally-bred generations are bolstered by further migrants from continental Europe. The arrival of large numbers of Clouded Yellows is often synchronous with the arrival of other migrants such as Painted lady butterflies or Silver-Y Moths.

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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