Silver-studded Blue (Plebejus argus)
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© Nick Greatorex-Davies
In Britain the Silver-studded Blue is a rare and very sedentary butterfly of heathland, calcareous grassland and sand dunes where it occurs in discrete colonies that can sometimes number many thousands, breeding on areas where the vegetation is short or sparse. Foodplants include Heather (Calluna vulgaris), Heaths (Erica spp.), Bird's-foot Trefoil (Lotus corniculatus) and Rockose (Helianthemum nummularium). The butterfly has undergone a major decline through much of its range in Britain due to habitat destruction and lack of grazing. (For further details on this species see http://www.butterfly-conservation.org/).
Status details :
Status since 1979 is Stable with a increase of 12%
Status over the last 20 years is Stable with a decrease of -31.2%
Status over the last 10 years is Stable with a decrease of -6.4%
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 butterfly was originally recorded regularly on just four BMS transects from which the data show no significant trend. It has now been recorded at over 50 sites, albeit not regularly for many, and the overall population trend since 1976 is stable though there has been a slight decline in the last decade or so. At the site level the data show that the butterfly is stable at most sites with sufficient data to calculate trends, but is doing especially well at Prees Heath in Shropshire, where habitat has been managed for it, and at Studland Heath in Dorset, both sites at which it has increased in the long-term.
In Britain this butterfly is highly dependent on very short vegetation where the microclimate is warm, and it has been lost from many sites not only because of direct habitat destruction but because of lack of appropriate grazing and burning management that maintain the required short vegetation with appropriate foodplants and ant species with which it is associated.
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, Silver-studded Blue has been recorded from 182 transects in the Butterfly Monitoring Scheme. Of these, annual indices of abundance have been calculated from 92 sites, with an average index of 130 individuals per site.
For 27 of these sites, Silver-studded Blue has been recorded well enough to calculate annual indices of abundance in more years, allowing trends to be calculated.
In 2016, 7543 individuals were recorded from 22 sites, producing annual indices at 19 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
|Extinct sites (2)|
|Stable sites (30)|
|Increasing sites (6)|
|Declining sites (6)|