Sunday, May 23, 2021

Progress Report...

This is is an unusually wet May, and Purple Emperor larvae get held up badly by wet weather. They don't like wet foliage, though they are adept at making the most of dry weather windows, feeding up fast when the foliage is dry. Wet (and cold) weather holds up skin changing, which in months like this can take well over a week.  

One of my wild larvae, 'Boris', seemed to be about to start skin changing (to L4) on May 9th and was stuck changing on May 22nd. Here he is, taken yesterday:-

All the other larvae seen yesterday were in the mid-L4 stage, including one who was still in hibernation (though green) on April 30th. He's since caught up spectacularly, and has overtaken 'Boris'. 

All this means that wild larvae are not behind schedule - yet. The season is actually tracking that of 2010, when the first Emperor took to the air on June 26th (after a good June). Here's a typical mid-L4 larva, from yesterday:-

This is the infamous 'Priti', and she's on the march... Be very worried... 

Late May is a key time of year for Emperor larvae, with them feeding up in their final instar and preparing to pupate. It looks as though the weather is going to improve after tomorrow (it can hardly get worse...) - in which case, they'll catch up fast...

Provisionally, I guess that the first male will be seen on June 26th, but I'll make my formal prediction at the end of this month, as usual. But please don't think that Emperors wont start before mid-July this year - at least, not yet....  Neil's going for June 28th, at this stage. 

Watch this space... ... ...  

For the record, of the 20 larvae I have followed since last autumn, six are still extant: 'Boris', 'Jacob', 'Liz' (Truss), 'Margaret Hilda', 'Sir Nick' and 'Priti'. I may yet refind one or two others, notably Andrea (Leadsom). Winter larval survival was relatively good, though at least three were predated during the cold April, including 'Donald', my favourite.

Tuesday, May 11, 2021

Skin Changing

Purple Emperor larvae continue to develop slowly, held up by cold weather and now, by rain (which is probably a greater hindrance to them).  

At present, early larvae have just entered the 4th instar (L4) and the majority are skin changing, or about to. This means that they are not yet that far behind the modern norm, but a wet May (which seems likely) will delay them significantly.

Rather chuffed to witness a skin change yesterday, and manage to photograph it (note the wobbly horns) -

Unfortunately, I lost a few wild larvae during April (and early May) to predation. This is annoying as my winter larval survival rate was 60-65% (depending on whether I refind one missing 'pillar), which is the best I've recorded from a decent sample size. This suggests that 2021 could yet see a good emergence - but a great deal depends on June weather...

Watch this space, and enjoy the Painted Ladies, which have just arrived...


Saturday, May 1, 2021

Slow Spring Progress

Purple Emperor larvae are developing slowly in this cold, late spring (I recorded frosts in my garden on 27 nights during April). 

One larva in Savernake Forest was still on its winter hibernation pad on 30th April, though it had greened up nicely and would have found eadible leaves within half a metre had it bothered to move (oddly, it is in a south-facing position).

Most wild larvae have fed a fair bit, post-hibernation, and will be seeking to change skins into L4 within a few days. This means that they are not that far behind the modern norm. The three I have in captivity (an outdoor sleeve) are all skin changing now, as are one or two early-birds in West Sussex.

Nomally, Emperor larvae are held up by early spring rains - but this time it's cold drought...

I'm not yet able to give a final reading on winter survival / predation percentage, and wont now be able to before mid-May. However, the predation / loss rate is likely to be between 40-50%, which is actually about as good as it gets (last year the winter loss rate in W Sussex was 85%). 

Unfortunately, though, both Ben Greenaway in W Sussex, and me in N Wilts & SW Oxon, seem to have lost some feeding larvae during April, to predation. We may yet refind some of these lost souls, as post-hibernation L3 larvae can at times wander quite far (I've recorded 6m, but 1m is normally plenty). Sadly, at this stage 'Donald', 'Priti' and 'Andrea' (Leadsom) are missing-presumed-crunched. They have a huge following on Twitter.

But 'Boris' and 'Margaret Hilda' are feeding well, and are set to change into the 4th instar very soon (weather permitting). Here's 'Boris' from April 30th:-

The question readers want answering is when will iris start to emerge this year? That's always hard to answer before late May but at this range it's unlikely that the butterfly will start to emerge before June 21st this year - but a warm, dry May could bring that forward.  Watch this space...