20 June 2022
By 20 June Purple Emperor numbers were increasing rapidly, with more than 20 individuals seen by Matthew, Karl or me. Even better, the males were regularly coming down to collect salts from the tracks. Most were lured down to my belachan & pickled gourami baits, which have proven particularly effective this year, although a couple came down to piles of horse dung. I baited the same spots daily, often finding them topped off by a fox scat, laid overnight. Over the next couple of weeks I reckon that more than 100 visitors managed to photograph Emperors on my baits.
Groundings at Knepp used to be very rare events, despite the vast population, but have slowly increased year-on-year. But this year the floodgates have opened and we've enjoyed what must be a tenfold increase. It's difficult to explain this trend, but I've long suspected that it may be due to the very different biochemistry of the soils and sallows, compared to 'typical' Emperor sites (with a long history of woodland cover). In the earlier years, were the males able to assimilate the required salts in the larval stage, as the sallow foliage would have been rich in the nutrients derived from once heavily fertilised farmland? If this were the case, changes in the biochemistry of the sallows, with each growing season and leaf-fall, might have led to an increasing need to seek out salts from more typical sources.
My brother, Mark, joined me for the day (the last two images are his), but sadly had to return to Antwerp the following morning. He would be back in mid-July, when the Emperors were still going well - at the time of posting, this is already looking like an unusually long flight season.