Adonis Blue (Polyommatus bellargus)
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© Nick Greatorex-Davies
The Adonis Blue is a scarce butterfly in Britain, and like its relative the Chalkhill Blue, occurs only on herb-rich chalk and limestone grassland where its foodplant Horseshoe Vetch (Hippocrepis comosa) grows, usually on south or south-west facing slopes. It requires shorter turf than the Chalkhill Blue where the microclimate is particularly warm. (For further details on this species see http://www.butterfly-conservation.org/).
Status details :
Status since 1979 is Rapid increase with a increase of 134%
Status over the last 20 years is Stable with a increase of 16%
Status over the last 10 years is Stable with a decrease of -47.0%
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 :
There has been a significant increase in abundance of Adonis Blue on UKBMS transects since monitoring began. This in part has led to its status as a UK BAP priority species being dropped and this butterfly is now a common sight on a number of good quality chalk grassland sites in southern England where numbers regularly reach several thousand on core sites in Sussex and Dorset. Climate change, and the resulting warmer microclimate at ground level, in addition to the increase in rabbit grazing have benefitted this butterfly, making more of its hostplant suitable for breeding. Consequently it has spread onto sites where it used to occur but which had become unsuitable. Data indicate that colonisation has taken place at several scheme sites during the monitoring period.
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, Adonis Blue has been recorded from 247 transects in the Butterfly Monitoring Scheme. Of these, annual indices of abundance have been calculated from 137 sites, with an average index of 149 individuals per site.
For 60 of these sites, Adonis Blue has been recorded well enough to calculate annual indices of abundance in more years, allowing trends to be calculated.
In 2017, 23800 individuals were recorded from 70 sites, producing annual indices at 61 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 (8)|
|Extinct sites (2)|
|Stable sites (50)|
|Increasing sites (11)|
|Declining sites (8)|