Tuesday, July 25, 2017

Iris broods – a question for the ‘Empire fraternity!


Hi folks,

I have a quick question for the 'Empire's experts as I think it is unlikely I'll bump into Neil or Matthew for a year or so! Is a second iris brood a total impossibility? Does this happen elsewhere in the world where there may be longer periods of warmth and light? Or do the larvae universally require sustained periods of low light and cold to develop properly and pupate? Thank you.


7 comments:

Liz Goodyear said...

I think the chances of a second brood quite high considering such an early emergence. However the subsequent rubbish weather might cause a negative effect. Who knows?

Matthew Oates said...

Apparently there's already a 2nd instar larva at Knepp!!!!!!! I haven't seen it yet. Neil saw a female egg laying there on June 16th.

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

'Climate change is an invention of the Chinese to disadvantage American industry'. Trump.

Neil Hulme said...

Yes, the species is bivoltine within the southern part of its wider range. As far as I'm aware there's currently just a single record of a second brood adult in the UK - a September sighting at Wiston in West Sussex. As the flight season has come forwards to meet White Admiral, we must be in with a chance!

Southsea Si said...

Liz, Matthew, Neil, thank you all.

I don't know whether to be excited at the (very slight) prospect of a second brood, or worry for the implications this could have for next season. I guess we'll have to wait and see before we start down that path. Many a slip and all that.

And butterflying advice always goes well with a bit of political satire. :)

laurence.d said...

I think our hearts would like an October iris, but our heads know it would not be good for the species.

Tony Baines said...

Given that in most places iris is very difficult to spot at low densities (even when you know it's probably present) it's quite likely that 2nd brood specimens have been missed in the past. Would have thought the chances of a few emerging this year must be quite high.

Guy said...

I'm not aware of iris being habitually double-brooded anywhere in Europe and the literature, so far as I know, insists it is strictly monovoltine in the wild. Its close cousin ilia is bivoltine in much of its range, though. If iris did produce a partial second brood this year I would not necessarily fear for the offspring. I have several times seen evidence of second instar larvae hibernating, and the usual third instar larvae do spend a lot of time in August and September just sitting around killing time.

Here in the mountains (I live in the Swiss Alps) I always see females well into August (I found a freshly laid egg today). In the hottest part of the Rhône Valley, however, where there is a Mediterranean climate, I usually see the species until mid-September - males included. Assuming the species is strictly monovoltine (which I realise might be a false assumption) I had wondered if the season there was either prolonged by aestivation - a well-recorded phenomenon for some other species - or delayed at some stage, to avoid their emerging in the hottest part of the year.

All very interesting.

Guy