Pearl-bordered Fritillary (Boloria euphrosyne)
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© Nick Greatorex-Davies
The Pearl-bordered Fritillary lives in close-knit colonies requiring short vegetation is sunny situations where there is an abundance of its foodplant, violets, mostly dog Violet (Viola riviniana). Once widespread in coppiced woodland and bracken habitats the species has disappeared from much of its former range in England and Wales. (For further details on this species see http://www.butterfly-conservation.org/).
Status details :
Status since 1976 is Rapid decline with a decrease of -72.3%
Status over the last 20 years is Stable with a decrease of -27.3%
Status over the last 10 years is Stable with a increase of 20%
Log collated index plot
This chart shows the index of abundance (LCI = Log Collated Index) over time. It shows fluctuations in
populations from year to year, and is scaled so that the average index over the whole series is equal to 2
(horizontal line). For greater detail about how this index is derived, click on the green question mark above.
Trend description :
This species has shown a significant long-term decline and it has become extinct at several monitored sites. This corroborates the trends in distribution shown in the atlas datasets. Undoubtedly loss of suitable habitat, often through lack of, or inappropriate, management and the isolation of remaining, often small and vulnerable, colonies is why this species has disappeared from so much of Britain. More recently, abundance on monitored sites has stablised as this species in particular has benefited from recent targeted conservation management.
This map shows the distribution between 1995 and 2016. Data is derived from the Butterflies for the New Millenium dataset via the NBN Gateway
This chart shows the average number of butterflies seen on transects between Arpil and October across all sites (fitted values from a Generalised Additive Model). The blue line gives average counts over the full BMS series (1976 to date) and the red line gives the average for the last year.
This map shows symbols for the mean abundance at transect sites, with the colour of the symbol reflecting the level of abundance. Means are over all years. Grey background squares are the occupied cells as shown by the Butterflies for the New Millenium over the previous ten year period.
In total, Pearl-bordered Fritillary has been recorded from 256 transects in the Butterfly Monitoring Scheme. Of these, annual indices of abundance have been calculated from 207 sites, with an average index of 17 individuals per site.
For 111 of these sites, Pearl-bordered Fritillary has been recorded well enough to calculate annual indices of abundance in more years, allowing trends to be calculated.
In 2017, 1290 individuals were recorded from 53 sites, producing annual indices at 43 of these.
Links to counts
This map shows the trend in abundance at particular transect sites for which data has been received within the last five years. Trends (increasing, declining or stable) are assessed at sites where the species has more than five years of annual index data. Use the option boxes below to view plots for individual sites.
Links to lists of sites with particular statuses
|Colonised sites (2)|
|Extinct sites (10)|
|Stable sites (46)|
|Increasing sites (7)|
|Declining sites (33)|