Red Admirals, Vanessa atalanta

2017 was generally not a  good year for butterflies here in South East Scotland, but strangely it was a very good year for Red Admirals, Vanessa atalanta.

In previous years the Red Admiral was considered to be a summer visitor to Scotland. They would arrive here from May to July from the continent and would lay eggs to produce the next generation, which it was thought either perished or returned south for the winter. However, over the last few years there have been a number of early sightings of Red Admirals here, suggesting that they are able to survive the milder winters we have had recently. Sadly, the long cold winter we have just had appears to have killed off all of the Red Admirals, but I notice that in southern England enthusiasts have found eggs and caterpillars throughout the winter.

The caterpillars nip the stems of nettles, causing the top to wilt over and then they create a little tent for themselves by stitching the edges of a leaf together.

Last year there were a lot of caterpillar tents seen and I decided to collect a couple to watch the caterpillars' development. I picked two nettles containing caterpillars on 22nd August and put them in a pot of water with other nettles for the caterpillars to feed on. It turned out the caterpillars were very close to forming into chrysalises.

Two days later, on 24th August, I noticed that one had formed a chrysalis on roof of the container. 

The other caterpillar had made its way to the top of the container and woven silk to form netting on the plastic window. The next day this caterpillar was hanging by its tail end from its silk pad.

The following day, the 26th August, the second caterpillar was still hanging by its tail end. I took the cage outside and within 30 minutes saw it was now forming a chrysalis.

It was a further 28 days before a butterfly emerged from the first chrysalis on 20th September. The second chrysalis also took 28 days to eclose, with the butterfly emerging two days later.

Unfortunately, they both emerged while I was at work, so I didn't see the adult butterflies. I was interested that they both chose to form their chrysalises on the roof of the cage. As far as I am aware they normally form the chrysalis within the tent they have made out of nettle leaves. Maybe the shelter of the cage made them feel secure.

The Peacock - Aglais io

The Peacock butterfly is reasonably common here in East Lothian. They over-winter as adult butterflies, seeking out dark places, such as old sheds and buildings, or deep in log piles in which to hibernate.

They are often the first butterfly of the year to be seen, appearing on a sunny day in February or March. The adults go on to breed and lay their eggs in large clusters on the underside of nettle leaves in May or June. Depending on the weather the eggs will go on to hatch about two weeks later. The caterpillars will take about four or five weeks before they pupate. They will remain as chrysalises for somewhere around two to four weeks, depending on the temperature.

So, there is one generation of this butterfly each year. The adult butterflies emerge here in August and their numbers peak around the middle of the month. They slowly reduce in numbers as they start to hibernate and by October we only see the odd sighting. However, after hibernation these same butterflies will be on the wing until June the following year. So, potentially, an adult can survive for up to ten months.

Last year I found an enormous group of caterpillars in a patch of nettles in a field where I walk our dog. I estimate that there must have been over 200 caterpillars there. I took this picture with my phone on 19th July, just as the weather took a turn for the worst.

The following day (the 20th) I collected three caterpillars and put them on some nettles I had picked, which I placed in a cage in the garage next to the window. They were at least out of the rain and protected from predators.

By the following evening, they were all hanging upside down from the nettles, looking as though they were about to pupate. They remained like that all day on Saturday 22nd, which was particularly wet and cold.

On Sunday morning, when I took a look, they had all turned into chrysalises.

During that period we had torrential rain for three days and when I took a look at the nettle patch I couldn't find any of the other caterpillars. I don't know if they had perished, or if they had also turned into chrysalises, which I couldn't find.

I had to wait for 24 days for my three chrysalises to emerge into butterflies on 15th August. I took the picture below before I went to work. You can see the pattern of the wing showing through the chrysalis.

And when I arrived home later that day, I was lucky enough to see the butterfly that had emerged.

The under-side of their wings is really well camouflaged among the dead nettle leaves, unlike the upper-side which is so beautiful.

The Gatekeeper - Pyronia tithonus

What with one thing and another I didn't manage to keep my blog up to date last year, so my next few posts are from 2017.

Back in July last year I took the train down to Mansfield to pick up an old Triumph 1300 (one of my other hobbies is messing about with old cars!). I thought that there may be an opportunity to see some new species of butterflies while I was down in that area, so I e-mailed the Yorkshire branch of Butterfly Conservation. The Chairman, kindly responded, suggesting that I should call into Brockdale Nature Reserve, where I could see Marbled Whites, Melanargia galathea, and Gatekeepers, Pyronia tithonus, both species that don't occur in Scotland.

Picking up the car took a little longer than expected, but I managed to drive north for about 60 miles to Brockdale. As I arrived the car stuttered slightly, but then seemed fine. Unfortunately, by now it was 4pm and it started to cloud over.

I followed a path from the car park to what looked like a promising area, and after half an hour I had only seen a couple of Ringlets, a Large White and some Green-veined Whites.  I walked back to the car a little disappointed, but as I arrived back at the car park I saw a little brown butterfly in the grass.

I was delighted see that it was a Gatekeeper and while I was watching it I discovered that there were four of them there.

It was quite overcast by then, so my pictures are a little fuzzy.

This is the first time I have seen this little butterfly, which is common in much of England and Wales. For some reason, it doesn't appear to be moving northwards as so many other species have done, so is absent from Scotland.

The rest of the day didn't go quite as planned. The Triumph only made it about another mile before grinding to a halt. So, it took me longer to get home, with the car on the back of two recovery lorries. 

At least it saved me some petrol!

More Graphs!

In my previous post I compared last year's butterfly records with the average for the previous five years.

I then realised that back in 2001 I had a job as a seasonal countryside ranger at John Muir Country Park, here in East Lothian. I used to keep a record of the butterflies I saw each day and I also walked a transect. So, I thought that it would be interesting to compare my 2001 records with the last five years.

I know it is not very scientific to compare the results of one person from one site with those of several people from all of East Lothian, but nonetheless I have noticed some interesting results.

These first few graphs don't show anything too remarkable ...

... as I expected saw fewer butterflies than the current 20 or so recorders, although I was outside all day five days a week. However, what I notice is that my records from 2001 appear to be about two weeks later than the average over the last five years. John Muir Country Park is coastal and well known for its sunny weather, so if anything I would expect butterflies to appear there earlier than much of the rest of East Lothian.

Could this possibly be a sign of climate change?

The Green-veined White seems to be a remarkably consistent butterfly. Year on year its numbers don't appear to change much.

And I was interested to see how few Large Whites I saw. They certainly seem to be more common these last couple of years than I remember them being in the past.

The Red Admiral has certainly become more common over the last few years. It now appears to be able to survive the winter here, but in 2001 I didn't see any until the end of June.

And I had the impression that there are fewer Small Coppers around these days than there used to be. My records from 2001 appear to confirm this.

The Small Heath intrigued me when I worked at John Muir Country Park. They appeared to have a very much shorter season there than elsewhere in East Lothian where I was surprised to see them several weeks after they had finished at John Muir Country Park. Checking the more recent records, from 2010 Small Heaths appear to have a much longer season. It makes me wonder if they used to have one generation a year, but now can manage two.

The Small Tortoiseshell used to be a very common butterfly, which has declined quite seriously in numbers over the last few years. It is amazing to see how many more there were in 2001.

In contrast it appears that the Small White is more common these day than it was back then.

I also notice that back in 2001 I didn't record any Commas, Small Skippers, Speckled Woods or Wall Browns, as they hadn't arrived here then. In 2001 I didn't record any Painted Ladies, either, although I do remember seeing several in 2000. So, 2001 was obviously not a year when they arrived here in large numbers.

I was wondering if my mind was playing tricks on me, but my recollections appear to be backed up by the figures. What we can't be clear about is the cause of these changes. It is easy to jump on the climate change bandwagon, but it might just be the cause.

I promise, there will be no more posts containing graphs this year!!

5-Year Comparisons

I have mentioned in my previous couple of posts how things have changed for Speckled Woods and Wall Browns over the last five years in East Lothian. These two species have both extended their range northwards and only arrived in the county within the last ten years.

I have been comparing 2017 figures with the previous four years for all of the species occurring here and it is apparent that some species have done very much better than others. I had my own perceptions of how well each species had done, but it is interesting to see the combined records from all of the volunteers.

The problem with doing a comparison like this is that each year I have had more people send in their records  to me, so you would expect to see more records for each species. However, this hasn't been the case with many of them.

For instance, when looking at the Large White, Small White and Green-veined White, there is a marked difference in how they did in 2017. These three species that share very similar life cycles, with a spring generation and a summer generation. It is odd that the Small White apparently had a poor second generation, but the other two species did as well as ever.

In the graphs below the red line shows the 2017 records. The blue line is the average figure for the last five years.

I had thought that there had been fewer than normal  Peacocks around in 2017, but when I looked at the records received they appeared to have done better than normal.

This is in contrast with the Small Tortoiseshell, which seemed to have a very poor year. I was surprised to see that there were more records than I expected.

2017 was an amazing year for Red Admirals. They have been increasing in numbers over the last few years and it is thought this is because they are now able to survive the winter in the UK. Whether this is because the temperatures are warmer than in previous years, or if they have adapted to our climate is unknown. It will be interesting to see how the very cold winter we are experiencing just now will impact on their numbers later this year.

What I find most interesting is that the species, such as the Wall Brown, Speckled Wood and Small Skipper, which have all moved into East Lothian in the last nine or ten years, have continued to increase in numbers, while some long-established species have been declining.

Most people who submit butterfly records to me it was felt that 2017 was a poor year for butterflies. As I mentioned previously we may be showing a falsely rosy picture of how the butterflies did, as we had more people sending in records. However, the differences between the species is valid. 

It will be interesting to see what happens in the years to come.

The Fall and Rise of the Wall Brown

While I was delighted to see the arrival of the Wall Brown, Lasiommata megera, in 2010 and its subsequent spread across East Lothian I note that it has declined severely in Southern England. Strangely, it is hanging on around the coast of England, but since the mid-1980s, what was once a very common butterfly has become a rare sight in an area centred around Buckinghamshire and Oxfordshire.

The Wall Brown normally produces two generations of butterflies a year. The first generation emerges in May and June and a second generation occurs in August and September. This species over-winters as a caterpillar.

A study, published in December 2014, The lost generation hypothesis: could climate change drive ectotherms into a developmental trap? By Hans Van Dyck, Dries Bonte, Rik Puls, Karl Gotthard and Dirk Maes looked at the declining number of Wall Browns in Belgium.

Their theory is that due to climate change the season for this butterfly is extending. If the first generation is emerging earlier and the subsequent generation is therefore appearing earlier then there is a potential for a third generation to emerge late in the season. However, there is not enough time for this third generation to breed, or for their eggs to hatch in time to make it through the winter. Presumably, eggs and chrysalises can’t survive frosts. It would be interesting to know if all instars of the caterpillar can survive cold weather.

This theory sounds very plausible to me and it could also help to explain why the Wall Brown is now spreading north into East Lothian. We have certainly been experiencing less severe winter weather here over the last 20 years. Possibly before that our season wasn’t long enough for two complete generations to survive and go on to produce caterpillars before the winter set in. In effect we are now experiencing the sort of weather that was once more common in the Home Counties.

Number of Wall Brown records received over the last five years
2013	2014	2015	2016	2017
54	78	70	129	273

2017 was the best year we have had for Wall Browns. The number of records I have received has increased each year since they were first recorded in East Lothian in 2010. Last year we recorded more than twice as many Wall Browns as we had in 2016. They have now made their way right around the coast and to various inland sites.

They are a very welcome addition to the butterflies of East Lothian.