Wall (Lasiommata megera) - PRIORITY SPECIES

Description

The Wall Brown is a medium sized orange and brown butterfly (wingspan 45-53 mm), named for its habit of basking on walls, rocks and stony places. The wings are beautifully marked with brown lines and eye spots. Females are larger and brighter than the males, which have a line of black pheromone scales (sex-brand) across their forewings. The flight of the males is fast and low over the ground as they patrol their territories for females or rival males.

Credit: Scott Shanks

Credit: Jim Black

Credit: Neil gregory

Life Cycle

The Wall Brown generally has two broods per year in South West Scotland. The adults begin to emerge from mid May and set about forming territories and finding mates. The pale yellow spherical eggs are laid singly on a variety of grasses including Tor-grass (Brachypodium pinnatum), False Brome (B. sylvaticum), Cock’s foot (Dactylis glomerata), Yorkshire fog (Holcus lanatus) and bents (Agrostis Spp.). The green caterpillars are nocturnal feeders and rapidly grow to full size (~24 mm) before forming a green or brown pupa attached to grass stems. The second brood caterpillars overwinter while still small, before resuming feeding during warm days in Spring.

Flight Times

In South West Scotland the Wall brown flies in two generations from mid May to late June, then the larger second brood appears from early August to mid September.

Habitat & Distribution in SW Scotland

Distribution map 2010

The Wall Brown favours short open grassland with stony or bare areas that the warmth-loving adults use for basking. In South West Scotland, the Wall Brown can be found along the coast of Dumfries & Galloway and South Ayrshire, with recent records from Mull and the coasts of Argyll. It can also be found at a few inland sites including the Butterfly Conservation reserve at Mabie Forest, near Dumfries. The Wall Brown has suffered a severe decline over most of it’s range in southern Britain with many colonies being lost, particularly at inland sites. This is in contrast to a notable northward expansion along the coasts of South West Scotland. The coastal distribution of the species may relate to higher mean winter temperatures at coastal sites compared to inland sites, as the survival of the second brood of larvae appears to be dependent on the recent milder winters associated with climate change. At inland sites the Wall Brown is sensitive to agricultural intensification or changes in grazing practice. The presence of rabbits is often associated with good sites, as they create bare patches where the females can bask between egg laying.

References

• 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.
• Fox, R., Asher, J., Brereton, T., Roy, D., Warren, M. 2006. The State of Butterflies in Britain and Ireland. Pisces Publications.
• Tomlinson, D. & Still, R. 2002. Britain’s Butterflies. WILDGuides

Written by Scott Shanks