Monday, May 30, 2011

Here We Go!

This is Aaron, seen yesterday afternoon leaving his feeding spray 2m above ground, crawling at speed down branch, ascending a main stem, and vanishing into the canopy 4 mins later. The pale tip and feet indicate that he is ready to pupate.

It seems that most full grown iris larvae ascend to the tops before pupating, but they are annoyingly difficult to spot there (if you think watching the adults gives you neck ache, try scanning sallow crowns for pupae - you need to lie down on the ride and scan with binoculars, which seriously upsets dog walkers...).

Yesterday, two out of six wild larvae had already ascended, Aaron went up whilst I was watching, and the other three will probably start to pupate midweek. So, it looks as though most will have pupated by next weekend. At home, two-thirds have pupated and the others are pupating.

As Dennis's data indicate, the time spent in the pupal state is determined by June weather, and the insect can get trapped in the pupal stage by poor weather (I recorded pupae lasting 28 days during the Silver Jubilee Rains of 1977).

We have an anticyclone coming over this week, which suggests that we should start looking for adults over the weekend of June 18th-19th, but that might change as much depends on the second week of June.

There is, at this range, a serious chance of breaking the record for the earliest ever iris appearance, and the hunt is on. Early betting is as follows -

6-4 on Favourite: Bookham Common & Ken Willmott

3-1 Southwater Woods & Neil Hulme + friends.

4-1 Alice Holt & Tony Baines, Ashley Whitlock

10-1 Somewhere and Someone else...

It could be you... The Heslop Cup will be awarded to the winner.

Follow me on twitter on

Friday, May 27, 2011

More Captive-rearing Input

Just to add to Matthew's observations. I have several larvae this year (as posted previously) and one pupated over 2 weeks ago! However, that seems to have been the exception. The remainder are either in a position to pupate (i.e. under a sallow leaf, head toward the leaf tip) or have pupated in the last 2 days. As mentioned, the cooler weather has certainly slowed things down considerably, thank goodness!

Thursday, May 26, 2011

Panic Receding

Looked at 6 wild iris on Monday 23rd. They'd made little progress since my last visit on the 15th, due to cool weather. None had started pupating, though two were full to bursting point and the others weren't far behind. They should be starting to pupate now, but they can take several days to pupate in cool showery weather, and the insect can last for a good three weeks in the pupal state when the weather's poor - as Dennis data show.

Also, at home, I've still only got one pupa, though all the others are on the leaf undersides, pupating.

So, the chances of iris emerging in mid June are receding fast, though we are still likely to have an early season and it will only take another good anticyclone to speed things up again. The forecast for the next few days is poor though, and we are due a poor June...

Watch this space...

Friday, May 20, 2011


Photographed this evening (Fri 20th May) in a garden in the Strong country (Heslop's phrase) - Looks male to me... Even if he spends 3 weeks as a pupa he's going to emerge in mid June...

Meanwhile the others are not far behind -

These guys are well synchronised with their wild Wiltshire cousins...

The race is on to smash the all-time record for the earliest UK Purple Emperor, only a foul June can stop us...

Follow me on Twitter at

Thursday, May 19, 2011

larvae May 2011

I agree with Matthew: it looks as if we might have an earlier season than average, which is bad news for my annual field meeting in Bernwood Forest, arranged for 9th/10th July; it might well be almost all over by then!
Just one of my 3 larvae is on the underside [yesterday]; the other two got close together, which was a good photo opportunity. you can see quite a difference in size. Statistics are boring, but Matthew insists that I put this on the website [I can see your eyes closing as you read this!]. This is what I found in Switzerland [well, Roger Dennis actually did the statistics from my data]: The mean time spent as pupa was 19 days for females [range 14-31 days, n=88], and 21 days for males [range 14-28 days, n=114]. A tendency existed for the earlier the pupation date, the longer the pupation period; this was significant only for females [males: r= - 0.08, P=0.28; females r= -0.29, P=0.0001]. There you are: has that put you all to sleep?

Wednesday, May 18, 2011


This photo was taken this morning in my garden. Note that my captive larvae are nicely in harmony with their wild cousins in this part of the world, in terms of timing of development, and are not early birds.

Wild cousins in Sussex and Surrey will be further advanced.

Unless we get a cold wet late May (which isn't forecast) and a cold wet early June THE PURPLE EMPEROR WILL BE ON THE WING IN MID JUNE...

There have been summers when the insect has got stuck either pupating or in the pupal stage or both (1977, 1980 and 1990). I'll post some info about this later.

But we are panicking...

Sunday, May 15, 2011

Panic Stations!

Despite a cool, grey week we are hurtling towards the 2011 Purple Emperor season. Six larvae were observed in the wild in Wiltshire today. All were in the final instar. One was just about full grown (tail turning pale) and another two were extremely large. Given the week's weather forecast, it seems likely that the first pulse of the 2011 iris emergence will be pupating shortly (it may already be doing so at 'early' sites in Surrey and Sussex).

Unless late May and the first half of June are cold and wet (as happened after the wonderful spring of 2007) the Purple Emperor is going to emerge in mid June, maybe earlier. My prediction is 14th / 15th June (when I'm scheduled to suffer two days of corporate bollox). The insect usually lasts about 18 days in the pupal state in the wild.

So, if you've booked leave / accommodation for early July think again. If you've booked this for mid July cancel, you'll be too late.

Meanwhile, here is Lot's Wife, who should be full fed in 2-4 days.

And here is Joshua son of Nun who should be pupating next weekend. Both pictures were taken today.

Coming soon to a forest near you, the White Admiral...

Saturday, May 7, 2011

State of the Nation's Caterpillars

Recent lack of Purple doings due entirely to sublime spring, with definitive emergence of Pearl-bordered Fritillary etc.

Today, I visited and refound all six wild larvae. Of these, four were in the final instar and two were in the final skin change. Two of the four finals (Lot's Wife and Joshua son of Nun) were half way through the final instar. Here's Joshua, feeding.

My nine captive larvae (on a late-leafing tree) are in a similar advanced state.

All this means that the Monarch of All Butterflies is, at this stage, set to take to the air circa 7th-10th June - certainly by mid June - unless the jet stream jumps south (which it may be doing now) and slows them down. This would smash the all-time known record for the earliest purple appearance (though we do not know how early iris appeared in the amazing summer of 1893).

Larvae of other high summer species are similarly advanced. Brother Quercus has largely pupated, Sister w-album is pupating now, and camilla of the woodland rides is full fed and about to pupate.

If you've booked holidays for mid July Think Again...

Watch this space, closely ...