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Northern Brown Argus (Aricia artaxerxes)
© Nick Greatorex-Davies
The Northern Brown Argus is restricted in the UK to northern Britain where it is very localised occurring in discrete colonies on generally south-facing calcareous grassland slopes where its main foodplant Rockrose (Helianthemum nummularium) grows. (For further details on this species see http://www.butterfly-conservation.org/).
Family: Lycaenidae
Status: Stable
Status details:
Status since 1976 is Stable with a decrease of -17.4%
Status over the last 20 years is Rapid decline with a decrease of -71.7%
Status over the last 10 years is Rapid decline with a decrease of -38.5%
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:
This butterfly is regularly recorded on about seven BMS transects. The data show no significant trend though there appears to have been a general decline since 1993 but only at Smardale Gill in Cumbria is there clear evidence that numbers are declining.
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, Northern Brown Argus has been recorded from 198 transects in the Butterfly Monitoring Scheme. Of these, annual indices of abundance have been calculated from 50 sites, with an average index of 34 individuals per site.
For 24 of these sites, Northern Brown Argus has been recorded well enough to calculate annual indices of abundance in 6 or more years, allowing trends to be calculated.
In 2006, 1087 individuals were recorded from 27 sites, producing annual indices at 22 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
- Stable sites (13)
- Declining sites (6)
