In At Last

Today (Sun Nov 27th) my last two captive iris larvae went into hibernation. This is the latest I've recorded them go into hibernation in some 25 years of intermittent breeding - though I've seldom bred more than 3-4 at a time and the sample size is probably <100. They seem to wait for their seat leaves to be completely dry before they move (though I've seen them crawling around quite happily in wet conditions in the wild). Wish I could conk out for four months too... .

Wont Go To Bed!

Iris larvae remain loath to go into hibernation in this mild autumn, though they are actually going in now.

In Savernake, six out of nine had gone into hibernation by Fri Nov 18th. The first went in between the 5th and 12th.

However, in 2009, one was hibernating by Oct 23rd and the last by Nov 15th. In 2010 one went in between 17th and 23rd Oct, and all were in by Nov 13th. And those were fairly mild autumns.

In captivity this autumn, on a 'late' tree, four out of seven are now in hibernation but two are still on green leaves, as below.

'I refuse to hibernate!' Culkerton, Glos, 20/11/11

'Done it!' Savernake, Wilts, 18/11/11

How not to look after your Emperors

This is what we saw as we walked through a wood in central Herts yesterday. Woodland grant in place and rideside sallows removed as was rideside honeysuckle. And for info its not without continually telling this particular government body to manage the sallows in the Hertfordshire woods for Emperors. Purple Emperor is a Hertfordshire SAP species to which this particular government body is signed up as a partner. Our taxes paid for this! Copy and paPhotos by Andrew M




And the last one standing - its was so tall it wouldn't fit in the view finder


And yes we have told them how important sallows are!

Hubris

Delighted to find an iris egg case base in Marlpost Wood, West Sussex, on Sat Nov 5th. The same leaf also held a 1st & 2nd instar seat pad, with the silk still fully visible, and distinctive feeding marks either side of the leaf tip. Sadly, no sign of the larva.

Egg case bases can persist into the autumn - if your eyesight is up to spotting them - but I don't think I've found one later than late Sept before. This may then be some sort of record, of which I'm proud - so nemesis will duly follow. The drama took place in the very spot where I saw (and caught) my first Duke of Burgundy Fritillary, in 1968.

Earlier that day, two out of nine wild larvae in / around Savernake were in hibernation, with a third thinking about it (i.e. it was watched spinning a silk pad on a twig, before returning to its seat pad). All bar two were fully coloured up. As in previous autumns, these larvae are on a mix of 'early', 'middle' and 'late' trees in terms of timing of leaf fall.

Meanwhile, back at the ranch, two out of seven larvae are in hibernation and the remainder fully coloured up. They are somewhat ahead of their wild cousins - or rather, their wild cousins are behind their wild fathers and grandfathers.

My long-haired cat, Flea, seems to have grown a relatively short and thin winter coat this autumn, perhaps suggesting a mild winter....

Larval Diapause

Probably the most thorough, although not entirely scientifically accurate article relating to Iris diapause was published in “The Entomologist's record and journal of variation” back in 1954, by F.V.L. Jarvis. The article was quite comprehensive and can be read via the “Biodiversity Heritage Library” website at the following URL:

http://www.biodiversitylibrary.org/page/30077952#page/296/mode/1up

Pages 212-217 and 234-240.

Similar articles associated with the subject matter (amongst many others, I am sure) were also published by, C.J. Luckens (1976) and H.G.Short (1977) also in “The Entomologist's record and journal of variation” and can also be read at the following ULR’s respectively:

http://www.biodiversitylibrary.org/item/93925#page/44/mode/1up

http://www.biodiversitylibrary.org/page/30001812

In spite of the findings reported in these articles however, more accurate research has shown that larval diapause is actually controlled by photoperiod and temperature in an absence of the normal ‘moulting’ hormone ecdysone.
Larval pigmentation/camouflage in response to diapause is a subject matter which is still under debate, although it is again thought to be under hormonal control. Consistent with the findings reported by Jarvis (and also Dennis, below), however there is still some evidence (Chippendale, 1972) which supports the idea that pigmentation is influenced by hydration levels and ingested host/food plant material(s). Chippendale 1972, abstract URL link as follows:

http://www.ingentaconnect.com/content/esa/aesa/1972/00000065/00000004/art00021

In contrast to the statement by Dennis however regarding the irreversibility of larval pigmentation, his statement (unless I have misunderstood it?) is unfortunately not correct (otherwise the larvae would never rouse from their diapausal states) and has been documented by many researchers (such as Bell 1983 and Rock 1983). Again the factors controlling arousal from diapause, are known to be temperature and photoperiod influencing hormonal balances. Bell 1983 and Rock 1983 abstract links can also be read at the following ULR’s respectively:

http://www.sciencedirect.com/science/article/pii/0022474X83900024

http://www.ingentaconnect.com/content/esa/envent/1983/00000012/00000001/art00013

I hope the information above is of interest to some of you?


Mark

autumn larvae November 2nd

Matthew's blog on the factors influencing survival is interesting. They certainly seem to like sitting in a water globule at the leaf apex. In these photos [November 2nd], you see two captive larvae on the same Sallow, just a few cms apart; one is still in green summer livery, while the other has coloured up, even though its leaf is still green. Two others have also coloured up, one on a green leaf, whereas the other is in its hibernation position on a branch near a bud. Past experience indicated that larvae remain green until the leaf changes colour; apparently not the case here. However, the two brown larvae on green leaves had been transferred, one week ago, from a branch [same Sallow] where the leaves had turned yellow [and the larvae had started to assume their hibernation livery] onto this branch where the leaves are still fresh and green. I think this shows that the colour change is determined by the leaf background, and that it is not reversible!