Scotch Argus Surveys in Loch Lomond and the Trossachs 2008
The Scotch Argus Erebia aethiops sub-species caledonia is a Scottish speciality which is widespread and abundant in the highlands of Scotland but largely absent from the lowlands where most grassland is improved and unsuitable. While Scotch Argus is not currently a species of conservation concern, it is considered vulnerable to climate change with higher summer temperatures likely to dry out the wet grassland habitats it prefers, especially in the southern part of its range. There is some evidence of declines in southern and eastern Scotland but it is not clear whether this can be linked to warmer temperatures of recent years or habitat change.
Habitat
The Scotch Argus is found in areas of unimproved damp grassland including upland grasslands but in Argyll where the Scotch Argus is the most common butterfly, it is widespread at sea level as well as at altitude. Like other butterflies of unimproved grassland such as the Pearl-bordered, Small Pearl-bordered Fritillary and the Chequered Skipper, the Scotch Argus is most abundant on sunny slopes where birch woodland and bog myrtle provide warmth & shelter and mineral flushing provide an abundance of nectaring sources.
Methodology
One curious feature of the distribution of the Scotch Argus is that it is present in the north and west (west and east side of Loch Lomond) of the Loch Lomond and Trossachs National Park but absent from the east and south (from Glen Ogle, Strathyre & most of the Trossachs) even though there is suitable habitat. It used to be present in Glen Dochart east of Crianlarich but was not seen here in 2007, perhaps because most of this Glen is now intensively grazed. Another characteristic of this butterfly is that at some sites, it can be amazingly abundant with hundreds of individuals appearing to rise out of the ground.
A survey was attempted in August 2007 to check each 5km square within Loch Lomond and the Trossachs National Park for the presence of Scotch Argus but this was not completed. It would be great if volunteers can be recruited to complete this survey and to study this butterfly and to understand why it can be so abundant at some sites but absent from others with seemingly appropriate habitat. It is thought that wet south-facing bottom of slope habitats with bog myrtle and birch woodland to provide shelter are favoured by Scotch Argus. For analytical purposes, it would be good to obtain data from such favourable sites and for other bottom of slope habitats with a different aspect and drier more open character. The Scotch Argus Survey form should be used to record habitat data and counts of Scotch Argus. A spreadsheet of the surveyed 5 x 5 km squares and perhaps a map also will be available nearer the time.
Description
The Scotch Argus when newly emerged is a stunningly beautiful butterfly which has dark brown or almost black velvety wings with orange bands on the upperwings containing conspicuous eye spots. The sub species which occurs in Scotland is called caledonia which has a narrowing of the orange band on the upper forewing between the top two and bottom eyespots. During the latter half of the flight period, most individuals do have a worn tatty appearance in contrast to the stunning newly emerged individuals.
The underside of both the male and female are variable: the female has the lower hindwing as either pale-yellow-brown or dark brown with a grey-violet band; the male hindwings can be a striking dark chocolate brown with a broad grey-violet band or paler brown.
When to Do
The flight period is from late July to early September with the main peak during the first two weeks of August when it is recommended surveys are undertaken.
If you think you might like to participate in the Scotch Argus survey during August 2008, it would be appreciated if you could
just to register an interest without any obligation and then an email reminder can be sent to you later in the summer.
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