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Purple Emperor (Apatura iris)
© Nick Greatorex-Davies
In Britain the Purple Emperor is an elusive and generally rare butterfly that is confined to well wooded areas in southern England usually where Goat Willow (Salix caprea) (its chief main foodplant) grows in abundance. (For further details on this species see http://www.butterfly-conservation.org/).
Family: Nymphalidae
Status: Stable
Status details:
Status since 1976 is Stable with an increase of 31.8%
Status over the last 20 years is Stable with an increase of 91.3%
Status over the last 10 years is Stable with an increase of 114.3%
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 very localised canopy species is rarely seen and the transect method is not suitable for monitoring it. It is only recorded regularly at West Dean Wood in West Sussex but only in very low numbers. The highest count was 10 in 1997. Occasional individuals are recorded on several other transects, notably Shabbington Wood in Oxfordshire.
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, Purple Emperor has been recorded from 79 transects in the Butterfly Monitoring Scheme. Of these, annual indices of abundance have been calculated from 120 sites, with an average index of 0 individuals per site.
For 30 of these sites, Purple Emperor has been recorded well enough to calculate annual indices of abundance in 6 or more years, allowing trends to be calculated.
In 2006, 49 individuals were recorded from 15 sites, producing annual indices at 14 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 (1)
- Stable sites (3)
- Declining sites (1)
- Increasing sites (2)
