Red Admiral overwintering 2017-2018

[Paul Harfield]

I Visited my Red Admiral site at Southwick (Hampshire) on 20th (in the rain) and 28th January in far better conditions to check on progress:
Saturday 20.1.2018 - Unfortunately I am restricted mainly to weekend visits and the weather does not always play ball. This visit was accompanied by persistant rain making searching for eggs a little tricky. I did not spend too long on site. Many of the eggs I found looked close to hatching and I was able to locate 1 quite large larva which I would consider to be 5th instar.

20.1.2018 - 5th? instar Red Admiral larva - Southwick

28.1.2018 - Typical condition of 'last seasons' Nettles. I think the small larva in the central tip will struggle to survive.

Sunday 28.1.2018 - Weather conditions were far better today. Mild and sunny but a steady breeze. As the WInter progresses the eggs and larvae are decreasing in numbers as one would expect. Despite the decreasing numbers they are still fairly easy to locate. There is plenty of new Nettle growth. The older Nettles are becoming increasingly straggly, old and leafless though they are still supporting some larvae. Where 1st/2nd instar larvae are currently on old Nettles with few leaves I think their survival is questionable.

28.1.2018 - Typical location of newer Nettle growth close to the bottom of the wall. The plant in the centre is currently supporting at least 5 1st/2nd instar larvae.

4 of the only 5 eggs found on 28.1.2018

Very few eggs were found at this visit, a total of 5 in fact and 4 of those were on one leaf. Many of the eggs that looked close to hatching last week have hatched. There now seems to be a high number of 1st instar larvae some of these were not immediately apparent until I checked photos.
The 5th instar larvae spotted at last visit was not found this time so hopefully it has gone to pupate. I was surprised to find leaves with several 1st/2nd instar larvae that had made a home inbetween the leaf veins under a thick silk pad without any leaf folding evident.
A bonus this visit was my first butterfly of 2018, at least 1 Red Admiral and possibly 3 but no photo.

28.1.2018 - 3 small larvae all living on one leaf in dense silk constructions without leaf folding.

28.1.2018 - Here 2 larvae share the underside of the leaf

28.1.2018 - Close examination of leaves revealed a high number of young larvae. Here 2 share a leaf in close proximity. One just disappearing over the edge of the leaf and one just poking its head through from underneath.

[bugboy]

Bookham 6/2/18
a day wandering Bookham Commons gave me the chance to check on the 4 eggs I've been keeping an eye on, all still eggs and not looking like they're going to hatch anytime soon (which given the current forecast is probably wise!)

This single egg is now at least 59 days old

The three on a neighboring leaf I only discovered on the 12th January, but do seem to be at a similar developmental stage, all four eggs are now definitely taking on a pale olive tinge suggesting that something is developing inside, albeit extremely slowly!

[Pete Eeles]

I would just like to say that, since I posted a link to this thread on Twitter, there has been nothing but positive feedback. So keep up the good work everyone - excellent field observations!

Cheers,

- Pete

[Paul Harfield]

Southwick 11.2.2018 - My most recent visit to this site was made in pleasant sunshine. However, conditions were not good enough to tempt out any adult Red Admirals. I was also unable to locate any of the larger larvae seen on previous recent visits. All larvae seen at this visit were either 1st or 2nd instar and again there were plenty of them. As noted previously some leaves are supporting several larvae in close proximity.

11.2.2018 - This leaf appears to be supporting 5 1st instar larvae.

At my last visit only 5 eggs were seen, 4 of which were on the same leaf. 2 weeks on 3 of these eggs remain unhatched but look close to hatching. The fourth egg would appear to have gone. Interestingly there now appears to be an extra egg on a different leaf that was not there 2 weeks ago. So, as noted elsewhere, it would appear that there is still active egg laying.

The same plant 28th January above and 11th February below. The lower photo shows an extra egg on the leaf top left

[NickMorgan]

This is all really interesting. What sort of temperatures have you been experiencing over the last couple of months?
We certainly appear to have Red Admirals over-wintering up here these last few years and we had hundreds of them later on last year. I haven't seen any eggs anywhere I have looked so far, but I'll keep looking.

[Vince Massimo]

Absolutely fascinating observations by Paul Harfield

Egg laying was also noted on 2nd February in Taunton, Somerset. (As reported on the Somerset and Bristol Branch BC Twitter feed) https://twitter.com/BCSomerset/status/9 ... pdates.php

An update from the Cemetery Wall site in Crawley:
Eggs continue to hatch, with the latest emergence being this morning.

Red Admiral egg (preparing to hatch) - Crawley, Sussex 16-Feb-2018

Red Admiral egg (hatched) - Crawley, Sussex 17-Feb-2018

However, some eggs are presumed dead when the larvae failed to fully emerge from their shells during a spell of cold weather.

Open egg with unhatched larva- Crawley, Sussex 4-Feb-2018

The remaining eggs (numbering approximately 13) are now at least 90 days old, but are becoming increasingly difficult to monitor because the leaves bearing them are shriveling and dropping from the plants.

2 Red Admiral eggs - Crawley, Sussex 17-Feb-2018

Vince

[Pete Eeles]

Excellent observations Paul and Vince; I am in awe!

The small number of larvae I have are still in place, but developing very very slowly. As Vince hints at, the biggest challenge is maintaining viable foodplant which really seems to suffer in the freezing temperatures.

Cheers,

- Pete

[Paul Harfield]

This is all really interesting. What sort of temperatures have you been experiencing over the last couple of months?

Hi Nick
The temperatures of the general area around Southwick in Hampshire were above average during December and January. The lowest nightime recorded temp was -4 in both months but generally for the most part it was above freezing. February has been more consistently cold with frost most nights. Hopefully the link tells you what you need to know:

https://www.accuweather.com/en/gb/south ... view=table

Saturday 17.2.2018 Southwick - Friday had been a Beautiful sunny day and Saturday looked to be much the same. This weather gave me a bit of hope of finding some adult Red Admiral activity at Southwick. On arrival at 11.45 air temp was about 10 degrees and surface temp on leaves was about 19 degrees. I saw a Brimstone as soon as I arrived and it was not long before a Red admiral appeared. I first saw this Red Admiral at 12.25 after a nervous few minutes of settling briefly then moving and settling again several times it started egglaying at 12.35. I watched as it laid half a dozen or so eggs before basking for longer periods. It was on the wing until about 2pm by which time the clouds were starting to fill the sky.
I was also able to pick out several eggs that had appeared since my last visit.

This female Red Admiral crawled around on small Nettle shoots laying several eggs. The resulting egg of this captured moment shown below 17.2.2018

I have now started to focus on one particular stretch of wall which seems like a hotspot. There are already a concentration of young larvae in this area, it is where I noted the first eggs laid today and this Red Admiral was noted to be basking in this area several times during my visit.
The leaf pictured in my last post with 5 1st instar larvae under it appears to now have one dead larva still on the leaf with the other live ones still in situ. The eggs that were close to hatching at my last visit are no longer evident on that leaf.

New egg since last visit. On a leaf that already supports a 1st instar larva.

Female Red Admiral at rest after egg laying 17.2.2018

[Jack Harrison]

This research suggests that Red Admirals, probably in all stages, are capable of surviving UK winters, at least in the less cold places. But the problem seems to be the shrivelling up of the main larval food plant, Nettle. I have to wonder if other known food plants, eg Mallow, are better able to withstand our winters.

I draw a parallel with the Comma. A century ago, it was more-or-less confined to using Hop (wild or cultivated) a plant that as best I understand, is restricted in its distribution. Then the Comma adapted to using nettles and look how it has spread in the past hundred years?

Red Admiral is clearly a tough species. I speculate that it only a matter of time that before it finds a plant other than Nettle, that is better at remaining in leaf through our winters. I offer no ideas what that plant might be.

Finally a question. The coasts of the main Channel Islands are virtually frost-free all year; for example, Pelargoniums (Geraniums to most of us) can grow into quite substantial bushes (as they do in the Mediterranean). I am not of course suggesting that Red Admirals might use Pelargonium as food plant, but how well do Nettles survive in coastal Guernsey/Jersey? I ought to be able to answer that myself having spent quite a lot of my working life staying in the Channel Islands, but I never thought to look for nettles in the winter

Does anyone know how Red Admirals are doing in the Channel Islands?

Jack

[peterc]

To take Jack's point further I suspect that any feeding damage on nettles weakens the foodplant and hence more likely to shrivel up and die during the winter. Just my opinion.

When I searched the Knebworth Park nettle patch early in January I was shocked to find that most of the nettles including those which previously had Red Admiral eggs on them had perished. However, the Ground Ivy was still growing well, and although an RA egg was laid on this plant it was in very close proximity to some nettles so I don't think the hatched larva would necessarily feed on the ivy leaves. Perhaps it is an adaptation strategy by female Red Admirals to lay eggs on alternative plants in winter providing they are close enough to nettles to increase the likelihood of eggs hatching.

At the Fairlands Valley Park site the nettles are still relatively fresh but there is far less competition from other plants such as Ground Ivy as at the Knebworth site. On the other hand, there were no Red Admiral immature stages here either when I searched last week.

By the way, excellent stuff, Paul.

Peter

[Vince Massimo]

Just to clarify things regarding the state and supply of the winter food plant. The particular issue I am having is that the leaves that the eggs were laid on are now 3 months old and are dying and falling from the plants. This is how I am losing track of the final few eggs. However there is no problem with the supply of fresh nettle, because the site I am monitoring is very sheltered, so nothing is getting frosted and there is fresh growth everywhere.

Fresh nettle growth - Crawley, Sussex 20-Feb-2018

Even on less sheltered sites where the top growth has been frosted, there should be some regrowth at the base of the plants which should be able to sustain the early instars.

Now down to the last 7 unhatched eggs, one of which I have a definite date for, (laid on 21st November 2017) thus making it 91 days old.

91-day old egg (plus hatched egg) - Crawley, Sussex 20-Feb-2018

Vince

[David M]

Fantastic observations once again, Vince. I need to find my own sheltered nettle patch to see if I can find RA larvae like you and others.

It's incredible how the early stages can suspend time and develop at a pace one would think would be impossible for this ostensibly mediterranean species.

[Pete Eeles]

I agree - excellent data and observations, Vince!

Cheers,

- Pete

[bugboy]

I went to Bookham today so was able to check on the few eggs I've been monitoring, albeit less intensively as Paul & Vince. Sadly the first egg which was known to be at least 59 days old on my last visit two weeks ago has been predated/destroyed since the part of the leaf it was laid on was missing. I've put the first picture I took last year next to today's image so you can see where it was. It also shows how the condition of the leaf has deteriorated over the winter.

The other 3 eggs which I first discovered on the 12th January are still attached but their leaf has suffered even more and is now essentially dead. The 3 images below show this clearly.

Indeed as I was inspecting them the leaf detached itself leaving me with a minor predicament. I had no way of safely getting them home which would in any case defeat the object of monitoring them so I found a fresh shoot poking up through the leaf litter and wedged it under. Hopefully it wont get dislodged and any larvae that hatch will be able to find a fresh leaf to make their home.

[millerd]

Fascinating to see how all these early stages are doing. However, they have yet to get through the next week of weather, which promises at least a covering (maybe more) of snow across Southern England and very low temperatures for the time of year. Let's see how they manage...

Dave

[bugboy]

Fascinating to see how all these early stages are doing. However, they have yet to get through the next week of weather, which promises at least a covering (maybe more) of snow across Southern England and very low temperatures for the time of year. Let's see how they manage...

Dave

I was thinking the same thing at work today as we prepared for the cold snap. With temperatures predicted to 'plummet' to -5 in London this is likely to be the real test for these young Red Admirals out in the sticks, where it's likely to drop several degrees lower. Maybe the Snow will help protect them from the worst of the cold.

[Vince Massimo]

An update from Crawley.

At the time of my last post on 20th February I was monitoring 7 un-hatched eggs. These were all on dead or dying leaves which I collected in order to continue making observations. In an effort to try to replicate the sheltered environment from which they came, the eggs were kept on potted plants which were given a good deal of protection. (This, after taking daytime and night time temperature readings from the wild site). Bearing this in mind, and the resultant reduction in the risk of predation, here are my observations.

One particular pair of eggs appeared ready to hatch on 23rd February. By 25th the larvae had chewed through the tops of the eggs, but this is when the really cold weather hit the UK. For 5 days and 6 nights the temperature here did not get above freezing, with a low of minus 5C on 27th and 28th February (minus 2C in the plant protection area). The last sub-zero day was 2nd March (and the early hours of the 3rd). By 4th March the open eggs, were still un-hatched and therefore presumed dead. However, on 6th March one was found to have hatched (this possibly happened on 5th March) and the larva was found the following day at the top of the plant. The egg was estimated to be at least 104 days old. At the same time the other larva was found to be slumped inside its egg and so is presumed to have died.

Fully developed eggs, ready to hatch - Crawley, Sussex 23-Feb-2018

Eggs now open - Crawley, Sussex 25-Feb-2018

Eggs still open - Crawley, Sussex 4-March-2018

Egg found hatched (after approx 8 days) - Crawley, Sussex 6-March-2018

Newly emerged larva - Crawley, Sussex 7-March-2018

The eggs remained open for approximately 8 days before one hatched and I now realise that I actually observed the beginning of something similar in the wild. One egg was seen to be open for 4 days during a cool spell, but I then lost track of it and presumed that the larva had died at the point of emergence.

Despite the protection the eggs are being given, some are still dying. They get to the point of hatching then stop. If the head is no longer at the top of the egg or the body of the larva starts to darken to yellow/brown, then it has died.

Dead egg - Crawley, Sussex 6-March-2018

One egg hatched yesterday, after approximately 106 days.
Of the two remaining eggs, one is at the point of hatching and the other has a least a week to go.

Developing egg - Crawley, Sussex 8-March-2018

Developing egg (and dead larva) - Crawley, Sussex 8-March-2018

The previous image also shows a larva which seems to have died a few days after emerging. However, in the garden I have a potted plant out in the open (albeit in a sunny spot). In the crown of this plant is a larva which hatched from a captive egg around 11th February (but put outside on 17th). I checked the plant after the freezing weather had passed and found that the larva had happily survived the snow and temperatures of minus 5C.

First instar larva - Crawley, Sussex 5-March-2018

Over at the Cemetary Wall site yesterday there were low numbers of (mainly first instar) larval tents to be found.

First instar larval tents - Crawley, Sussex 7-March-2018

Vince

[bugboy]

Fascinating stuff Vince. It shows just how resilient these little guys are. Like most of our wildlife, a lot tougher than we give them credit for, 'Life finds a way'

[NickMorgan]

It is really interesting to know that the eggs and larvae are able to survive sub zero temperatures. That gives me hope to keep looking at the nettles up here.

[Pete Eeles]

Have to say that I'm gobsmacked at many of the observations being made here ... this really is rewriting the books! My own personal observations have been curtailed since the Beast from the East, where the foodplant has really taken a battering and I wonder if this is limiting factor in the wild (i.e. a lack of nearby foodplant), rather that the ability of larvae to survive. Thoughts welcome.

Cheers,

Pete