Pearl-bordered Fritillary surveys in Loch Lomond and the Trossachs 2008
The Pearl-bordered Fritillary Boloria euphrosyne has been described as the 'lost butterfly' of Loch Lomond and the Trossachs as it used to be known at a few localities but recent observations are few. One of these localities was the north side of Loch Katrine where it had been seen in the 1980s and 1990s. However, more recent efforts had failed to locate it until May 2007 when a number were seen.
As adult Pearl-bordered Fritillary are only on the wing for a few weeks in May and their caterpillars on Dog Violet are very hard to find, it is quite likely that Pearl-bordered Fritillary is present in parts of Loch Lomond and the Trossachs National Park but is currently being overlooked. So your help is needed to find the 'lost butterfly' of Loch Lomond and the Trossachs
Description
Similar in appearance to Small Pearl-bordered Fritillary (Boloria selene) but Pearl-bordered Fritillary has an earlier flight period commencing late April to early June while the Small Pearl-bordered flies from late May onwards. Both are medium-sized bright orange butterflies with similar markings on the upper wings except for the black chevrons on the upper forewing being more separated from the dark border in Pearl-bordered but joined to the dark border in the case of Small Pearl-bordered. The different markings on the under hind-wings are the best method of distinguishing between these two species. The Pearl-bordered Fritillary has a small dark spot near the base of the hind underwing with two silver/pearl white cells on either side and a generally tawny appearance and the white outer cells are bordered by brown chevrons.
The Small Pearl-bordered Fritillary has a larger black spot near the base of the hindwing surrounded by seven silver/pearl white cells which are bordered by black as are the white cells on the margins of the hindwing. Caution is required though as Small Pearl-bordered Fritillaries are very variable and worn individuals can look very similar to the much rarer Pearl-bordered Fritillary.
CAUTION: These photos represent contrasting examples of these two similar Fritillary species but the markings of some individuals, particularly worn ones, do not make identification easy. Make identifications on the basis of underwings rather than upperwings.
More photos can be seen on UK Butterflies: Pearl-bordered Fritillary; Small Pearl-bordered Fritillary.
Habitat
In Scotland, the Pearl-bordered Fritillary is associated with a distinct habitat-type which partly explains why this species is quite rare: south-facing hillsides with bracken-grass mosiacs which are often adjacent to open birch woodland. These dry sunny bracken hillsides favour both Dog Violet and Pearl-bordered Fritillary but sites can become unsuitable from birch woodland regeneration, dense bracken growth or coniferisation. Nectaring sources including Bugle, Tormentil, Bluebell and Dog Violet are thought to be essential components of the habitat.
There definitely are pockets of south-facing bracken hillside with Dog Violet, Bluebell and Bugle in Loch Lomond and the Trossachs National Park which suggests that Pearl-bordered Fritillary ought to be present in these localities. A number of such sites were identified in spring 2007 and are shaded green in the Table below. Attempts to locate adult butterflies were unsuccessful but weather conditions were marginal. The other sites shaded yellow are sites which have not been visited yet but are considered as possible habitat as they are south facing open hillsides.
When to Do
Volunteers are required to visit all these sites shown in the Table below during the first three weeks of May 2008 when ONLY Pearl-bordered Fritillary are on the wing and before Small Pearl-bordered Fritillary appear. Any individuals seen between 21 May and early June may be either Pearl-bordered or Small Pearl-bordered, hence earlier survey dates are preferred but visits in this period may be undertaken if poor weather or circumstances prevent an earlier visit. These butterflies are easy to spot as both species are bright orange and any seen prior to 21 May are very likely to be Pearl-bordered Fritillary.
Methodology
The relevant OS map for the site you want to survey will be required to do this survey. All these sites are quite close to main roads and therefore do not require a long walk in but these south-facing hillsides are steep so a moderate level of fitness is required to ascend up to 250 m or so. Stout walking boots are recommended.
If you see any Fritillaries, it would be appreciated if you could complete a Pearl-Bordered Fritillary Timed Count Sheet which records some details of habitat characteristics such as abundance of Dog Violet & Bugle as well as numbers of butterflies. And of course, record any other butterflies that you come across.
But if you prefer to send in more limited data by email, then please
with basic information including 6 figure OS map reference, date and counts of Fritillaries.
If you think you might like to participate in this survey during May 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 in May to notify you when Pearl-bordered Fritillary are on the wing.
Sites in Loch Lomond and the Trossachs to be surveyed for Pearl-bordered Fritillary
The map below shows the 12 sites requiring visits in May 2008. If you place your mouse over the site name, a little window with the site name will appear and if you click on the site name, a 2 x 2km OS map will appear in a new window.
Site Name |
Grid Reference
(Click for OS map) |
Description |
Rubha Mor, West Loch Lomond |
NS343998 |
Bracken hillside above steep road escarpment with crawler lane - park at layby to the south of crawler lane, access via style at south end of layby |
Firkin Point, West Loch Lomond |
NN331011 |
South-facing bracken hillside in sw corner of NN3301 - park at Firkin Point |
Glen Croe, Ardgarten, West Loch Lomond |
NN256043 |
S facing slopes of The Cobbler in Ardgarten Forest - park at Ardgarten Visitor Centre |
Beinn Narnain, West Loch Lomond |
NN285053 |
S facing slopes of Beinn Narnain above forestry plantation - park at Loch Long car park |
Inveruglas, West Loch Lomond |
NN305092 |
S facing slopes of Ben Vorlich along track up to Loch Sloy - park at Inveruglas viewpoint |
Creag an Arnain, West Loch Lomond |
NN324108 |
South-facing slopes above viaduct just north of Inveruglas. Park at Inveruglas or at rough layby close to viaduct. |
Ardvorlich, West Loch Lomond |
NN324122 |
100m little hill with S facing hillside just west of railway. |
Ardlui, West Loch Lomond |
NN315158 |
SE facing bracken hillside just north of Ardlui - park beside rd at Ardlui station |
Glen Falloch, West Loch Lomond |
NN319201 |
S facing bracken hillside below pylon line and hillside to NE in NN3220- park just south of bridge over Dubh Eas |
Loch Katrine, Trossachs |
NN476103 |
woodland clearing at NN476103 along forestry track is where Pearl-bordered Fritillary was seen in 2007. Hillsides further east are unsuitable but good open bracken hillsides exist further west which may be suitable habitat - park at Loch Katrine car park |
Duke's Pass, Trossachs |
NN517036 |
South-east facing bracken hillside with abundant Dog Violet & Bugle on the western side of the road opposite the start of the Three Lochs Forest Drive - park at the entrance to the car park. |
Glen Ogle, Breadalbane |
NN564276 |
South-west facing bracken hillside to north of road extending eastwards about 1km and narrow band south of road- park at layby on north side of road. |
Key:
|
| not yet assessed as suitable habitat |
|
| identified as suitable habitat in spring 2007 |
Homepage
