Sunday, June 30, 2013

Sexing Pupae

Iris pupae are quite easy to sex, like most hawkmoths.  The larger, broader, lower one here is an Empress (and I think she's going to be a lady of no small consequence, she was a huge larva) -

I saw only one purple emperor in my local woods last year and found just one egg - which hatched out into a caterpillar called Tiberius, which in turn I lost when he went into hibernation. So it is with great pleasure I introduce you to Trajan, whom I found today, lurking in a different corner of the woods. He is the third wild pupa I have found. Of the last two, one died before emergence and the other was presumed taken by human or animal, as his pupa (but not its leaf) simply disappeared one day.

Here is Trajan:

I will keep tabs on him and if he colours up will be down there at the crack of dawn to watch him emerge.


Saturday, June 29, 2013

Checked on my captive larvae today to find that 2 have pupated and 2 have turned a very pale green and have positioned themselves under a leaf in preparation to pupate . The last larva I have which is at least a week behind the others , and is of particular interest due to the unusual colouration of the head capsule . I have only ever seen them with green heads with a red tinge to the tip of the horns , never with such distinct black markings . Is this unusual or just a normal variation ? I have a planned 3 day visit to Fermyn on 8/9/10th of July .Fingers crossed its not too early .

Many thanks

Dave Law  

Tuesday, June 25, 2013

As we wait with bated breath for the first report of iris on the wing, here's a link to some interesting and relevant reading matter. Dennis Dell's paper on emergence dates of the Purple Emperor is now available for free download (as are a large number of other fascinating publications) from the European Journal of Entomology site.

Sunday, June 23, 2013


This may be the first photo taken of an iris pupa in the wild in the UK.  The pupa was found a short distance from where the larva had been seen last weekend and was approx 4m above ground level.

Alternatively, try spotting the pupa in this photo -

I also found a full grown larva today, 23rd June, so they haven't all pupated -

In 1977 I found a full grown larva in Alice Holt on 24th June.  That year the adults started there on 23rd July.

I think that, given relatively decent weather, the first adults will start at the earlier sites around 5th July and a few days later (maybe the 10th) elsewhere.  If we get prolonged good weather they will appear earlier.  Alternatively, they may not appear before mid July...

Sunday, June 16, 2013

Flight Season Delayed

Last Tuesday I was of the opinion that the first Purple Emperors will appear at the very end of June at the early sites and around July 7th at later sites.  That was based partly on last Sunday's Countryfile weather forecast, which predicted high pressure pushing in from the Azores.  Unfortunately that bit of the forecast was wrong, badly...

I now need to revise my prediction, backwards.  This is because none of my captive larvae have pupated, though they are ready to do so, and also because none seem to have pupated in the wild.  Yesterday I managed to find four wild larvae, two of which were full to bursting point and turning pale, as they do prior to pupation.  The other two were almost full fed.  The forecast for the coming week, which is not a high confidence forecast, suggests that they should start pupating this week. 

At this stage, it looks as if iris will not be out anywhere in June this year, though it should begin at the start of July at early sites such as Bookham Common.  Elsewhere, it may not appear before July 7th at the earliest, more likely the 10th. 

My advice is to book your hols for the second and third week of July. 

Meanwhile, here's a game of Spot The Iris.  There are two full grown larvae in the picture, taken yesterday near Savernake.  See if you can spot them -

Tuesday, June 11, 2013

When Will They Be Out???

That's the question you're all asking...  It's not really possible to give an answer as the timing of the flight season depends heavily on weather during the pupal stage: they can shoot through this in 16 days (or perhaps less in very hot weather) or get stuck in it for 26 days, as happened last year.  Also, the process of pupation can be prolonged by cool wet weather.

At present, wild larvae in and around Savernake Forest in Wilts are in exactly the same state they were in this time last year, and only fractionally behind this time in 2010: some are fully grown, though their feet haven't turned pale yet (which happens immediately prior to pupation), some are in the mid-final instar stage, but one late one has only just entered the final instar.  Savernake is a 'late' iris site, the insect will be more advanced at 'early' sites in Sussex and Surrey.  Here's two final instar larvae (one late-final, one mid-final) that have fed close together all spring (spot the caterpillars):-

My guess is that iris will start in Savernake around July 7th but will be out in early sites such as Bookham Common at the very end of June - but so much depends on weather during the second half of June.  My advice is to book your holiday week for the second week of July (that's what I'm doing). 

Watch this space...