On The Move!

The current mild spell hasn't just woken hibernating butterflies, like the Brimstone and Red Admiral, but Emperor caterpillars.

Emperor catties are now waking on mass, and are relocating themselves to align alongside swelling sallow buds. A surprising number of them have hibernated in forks and on twig scars this winter, some distance from the buds. We don't know why. 

It is, of course, unusual for them to waken this early, and they're going to get stuck in the caterpillar equivalent of the dreaded airport Departures lounge for ages, waiting for the sallow leaf buds to start to open.

This is a hazardous time for them, as they can be picked off by predators, birds especially, when moving. Here's one moving up-stem, yesterday, a journey of at least 2m (he's just above the upper fork) -

Also, many are greening up, early, like this one below - 

Watch this space...

 

The 1970s

Here are the known start and end dates for Emperor seasons between 1975 - 1980 in and around Alice Holt Forest, East Hampshire. This is quite accurate data.

Year        First Sighting        Last Sighting        

1975        5th July                   2nd Aug        

1976        25th June                17th July                 

1977        23rd July                11th Aug                 

1978        15th July                13th Aug

1979        17th July                18th Aug                  

1980        20th July                25th Aug                  

What's interesting - beside the obvious fact that most of those seasons didn't start before mid-July - is how short most were.  

This is because most seasons were curtailed by either extreme heat (1976) or by adverse weather events (in 1977, the adults were knocked out by very cold nights at the start of August; in 1978, they were knocked out by a returning Polar Maritime depression). 

Times have changed...

 

 

Fingers Crossed...

 

Emperor larvae seem to be surviving their five month long winter hibernation period relatively well. 

Over the weekend, three of us checked 56 hibernating larvae in Savernake Forest, finding 47. Losing just nine out of 56 during the January and early February period isn't too bad - in fact, it's almost as good as it gets...

At this stage, it looks as though winter predation is only going to be in the Modest bracket, and not High. However, February and early March is the main period for losses. So, fingers crossed...

Some larvae, like the one above, are starting to green up. Now, that's early, very early, but this has so far been a very mild winter. Also, two had moved, up to buds.

If (underlined and italicised) winter losses remain in the Modest bracket and if (ditto) the weather is fine during the crucial pupation and pupal periods, 2026 could (ditto) see a sizeable Purple Emperor emergence - the two key stage periods of loss which seem to determine adult numbers are 1) winter and 2) pupation / pupal time (+ flight season weather, of course).  

Watch this space. We're not there yet, but we seem to be heading there... 

All things are for the best with this the best of all possible butterflies.