PE Distribution Map 1960-2025

 Here's a still photo of Martin Partridge's map of PE records 1960-2025, derived from BC / UKBMS data. Much of Norfolk is mysteriously missing from the video version previously published (with apols to Martin and Norfolk)!  

Autumn Larvae in Savernake Forest

For the last seventeen years standardised counts of autumn larvae have been conducted in Savernake Forest, Wiltshire. Here's the data - 

 

The table shows that autumn larval numbers mostly bumble along at a low ebb, but erupt spectacularly in good summers. These eruptions are highlighted in purple. 2025 was one of them.  It may well have been better than the data suggest, so don't take the data too literally - it merely shows trends.

The work is based on the assumption that the females lay a comparable percentage of eggs within reach each year, though there is no actual evidence for this either way... (searching is done from the ground only, using a shepherd's crook and binoculars - anything else would require a risk assessment the size of War and Peace). 

What's missing here is annual assessment of the quantity and quality of the sallow resource. These are not easy to quantify, particularly foliage quality (e.g. many of the Forest's sallows were afflicted by Melampsora Willow Rust during the wet summers of 2023 and 2024). 

Suffice it that the number of sallows in the Forest fluctuates considerably but is generally in decline, due to increasing squirrel damage ('bark stripping'), ride trimming (which renders many sallows unsearchable by removing lower limbs) and random felling during timber harvesting. 

Also, Savernake is not on particularly 'sallowiferous' soils, lying mainly on Clay with Flints of varying thickness overlying chalk. There has a paucity of sallow regeneration since the early 2000s.  

Remarkable Changes in iris distribution since 1960

This video makes clear how distribution has changed over the last sixty-five years, illustrating how much more of England is now "Purple"!

Mapped by Martin Partridge in Yorkshire. 

Best Dangle Leaf + 'pillar Photo Ever!

Check this out! Definitive photo of an Emperor cattie in hibernation by a bud, with the old feeding leaves dangling close by. 

Congrats to Mark Tutton for taking this photo, in Straits Inclosure, Alice Holt Forest, Hampshire, 11/11/25.   

 

PS 1) that catterpillar will change colour to match its background, and may well move position in this mild weather; 2) those dangles will soon blow or wash off!  

Dangle Leaf Update

The 2025 Dangle Leaf Season is now underway, though it is being delayed and hampered by unusually mild weather.

The impacts of mild November weather are:- 

1) most broader-leaved sallows remain green, with larvae lingering on the leaves, or being hard to find in hibernation because of the amount of leafage; 

2) in mild weather larvae can wander far and wide whilst seeking a hibernation spot (many wanderers seem to get predated, but this is hard to prove or disprove). 

In Savernake Forest yesterday, one nice broad-leaved sallow was completely bare of leaves and had already gone through the dangle leaf phase, just 2-3 sallows were in prime Dangle Leaf condition (having shed about 75% of their leaves), but the vast majority of broad-leaved sallows were still in green leaf. The narrow-leaved sallows (Rusty Sallow-types mainly) were more advanced, but there aren't many of these in Sav. One narrow-leaved was in prime Dangle Leaf condition, and revealed 5 larvae.  

Of 25 larvae seen, 14 were still on the leaf, though most of these were ready to quit; 10 were in hibernation, by buds or in forks or twig scars; one was wandering about. 

Several more known larvae were listed as Missing In Action, but may yet be found. We also found a few dangles without being able to locate the larva, which had wandered off.

Every autumn I pray for cold weather in early November, to encourage larvae to crawl just a few centimetres from their vacated feeding leaves before conking out... but every early November, it's mild (ridiculously so this year)...

Here's one of yesterday's larvae in hibernation on a twig scar - 

And here's a pair of classic Dangle Leaves, + silk -