Knepp 2024

Here's the data from the Purple Emperor transect at Knepp, which runs for 2km down an oak-lined green lane bordered by sallow thickets. It's a single species transect (ignoring all other species), which is walked once a week during the PE season, in afternoons only (from about 12.20), in decent weather (wind is a problem at Knepp), when males are on territory and, crucially, has a massive recording box, and takes about 3 hours:-  

 

This is good data. The UKBMS data is restricted to the standard 5m recording box and largely records males feeding on dog poo. 

The Knepp data suggests that PE had an 'average' year in 2025. However, counts during Week 1 and Week 2 were relatively high. Indeed, the 2024 Week 2 tally was the second highest for that week in the whole data set, only bettered by Week 2 of the 2018 annus mirabilis. 

What happened in 2024 is that the butterfly got systematically blasted away by spells of foul and abusive weather after Week 2. The Week 3 count was way below what it should have been. This is largely because the numpties insist in roosting in sprays in the oak tops, rather than on the leeward side of limbs... Had the weather not broken the annual total would have been in the region of 150-160.

Below are the PE season start and end dates at Knepp. Again, this is seriously good data, derived from diligent recording. This site is very well monitored.

First & Last Sightings at Knepp  2014 - 2024

        (earliest & latest dates in bold)

        2014    18th June     31st July

        2015    30th June     >21st July

        2016    27th June    3rd Aug

        2017    15th June    25th July

        2018    17th June    26th July

        2019    25th July    31st July

        2020    13th June  23rd July

        2021    2nd July     19th Aug

        2022    16th June    29th July

        2023    20th June    25th July

        2024    17th June    1st Aug

Just note how early PE starts there in this modern era, and ignore what the books say. Sooner rather than later a May iris will be recorded at Knepp...  

Only 2021 was a traditional year, with old-fashioned start and end dates.

Also note that PE has only been recorded in August during three of the 11 years.

Purple Emperor pages are being updated on the Knepp websites.