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Silver-studded Blue (Plebeius (Plebejus) argus)
© 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/).
Family: Lycaenidae
Status: Stable
Status details:
Status since 1976 is Stable with an increase of 10.7%
Status over the last 20 years is Stable with a decrease of -3.9%
Status over the last 10 years is Stable with an increase of 70%
Back to the topLog 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:
The Silver-studded Blue is recorded regularly on just four BMS transects and the data show no significant trend. At the site level the data show that the butterfly is increasing at Studland Heath but probably declining at Tadnol (both in Dorset). The large population at Great Orme in north Wales has only been monitored for six years. RSPB South Stack Ranges on Anglesey was monitored for a few years early on in the scheme and recently came back into the scheme. Data indicate little change here.
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.
Distribution...
This map shows the distribution between 1995 and 1999. Data is derived from the Butterflies for the New Millenium dataset via the NBN Gateway (www.searchnbn.net).
View the distribution on the NBN GatewayPhenology...
Phenology plot
Phenology plot
This chart shows the average number of butterflies seen on transects between Arpil and October. The black line gives average counts over the full BMS series (1976 to date) and the red line gives the average for the last year.
Abundance...
Abundance
This map shows symbols for the mean abundance at transect sites, with the size of symbol reflecting the level of abundance. Means are over all years.
Coverage
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 6 or more years, allowing trends to be calculated.
In 2006, 7543 individuals were recorded from 22 sites, producing annual indices at 19 of these.
This map shows the trend in abundance at particular transect sites. Trends (increasing, declining or stable) are assessed at sites where the species has more than five years of annual index data. Click on the green question mark next to the species name above for more details on how trends are calculated.
Links to lists of sites with particular statuses
• Extinct sites (2)
- Stable sites (12)
- Declining sites (5)
- Increasing sites (1)
