Recent Sightings Late June and July - The Amazing Painted Lady - a report and photos from volunteer Phil.

While walking between Canterbury and Dover on the North Downs Way on 21st June I started to become aware of several very faded painted lady butterflies in some large wildflower meadows crossed by the path. The following day while exploring some of the fortifications at Dover several more faded painted ladies could be seen, By all accounts around this time several more faded specimens were seen at Pulborough Brooks.  On returning there after a 3 week break on 28th June I found several more such butterflies and one in rather better condition feeding on the bramble in front of West Mead hide.

A few days later they all seemed to have disappeared.

I have long been aware that some butterflies are migratory, red admiral being a common and prime example. However, for migratory habits nothing can beat the amazing painted lady.  Every year these butterflies weighing less than a gram set out from North Africa on an epic migration to Northern Europe and even Iceland, sometimes crossing seas such as the Mediterranean, the English Channel and the North Sea, 

If this wasn’t interesting enough what I find even more fascinating is the story of the epic migration seems to have several somewhat conflicting variations.  I have gleaned these from various sources on the Internet, supplemented  by 2 books at home and a recently repeated BBC programme entitled “The Great Butterfly Adventure: Africa to Britain with the Painted Lady”. So let’s start with some facts that I think all sources agree on. 

The painted lady (Vanessa cardui meaning thistle butterfly) is found on most continents of the world but not Antarctica. In all places it is strongly migratory and its rather long pointed wings help it to achieve direct gliding flight in which it can travel at up to 30 mph. This will be particularly useful for some epic sea crossings for a creature that weighs less than 1 gram.

The main foodplant for caterpillars is the thistle, hence its Latin name but sometimes nettles and viper’s bugloss are used.

The population we see in Britain originates in North Africa and it annually migrates to Northern Europe, and even Iceland where it is the only recorded butterfly species. This takes place not in the shape of individuals flying huge distances, although most sources agree that some do, but rather in steps where the butterflies rest for a few weeks to produce new broods. Sources agree that the annual migration takes place in up to 6 broods.

Painted ladies cannot in any form survive the winters of Northern Europe and are therefore forced at some point to head back south. For some of their journey they fly very high and cannot easily detected by casual observers.

So far so good but here accounts start to differ.

While all sources agree that there is one other continent where painted ladies do not occur, most quote this as being Australia whereas one I found quoted South America. There is a very closely related species in Australia (Vanessa kershawi) which undertakes a southerly migration from Queensland to New South Wales.  There is another related species in South America Vanessa carye called the Western Painted Lady but I have yet to discover a source that suggests the presence of Vanessa cardui in the Americas south of Panama. It is from Central America and Mexico that similar epic annual migrations of painted ladies north through US and Canada occur. 

I have seen 3 different answers to the question of why they migrate. One suggests that the African summers are simply too hot and another postulates that more butterflies emerge in Africa and throughout their migration routes than food sources will support. However the BBC programme features a leading researcher who has demonstrated that one very important reason for migration is the need to escape a parasitic wasp present in North Africa which attacks painted lady caterpillars and is capable of completely wiping out whole broods.

A particularly important difference in accounts is the length of the brood cycle. Some sources quote just 4 weeks while others go for nearer 2 months with the main difference being in how long the caterpillar stage lasts. This can be seen to have an important bearing on the question of numbers of broods and the return migration

Then there is an important difference in views about a return migration to Africa from Northern Europe. Some sources suggest that the butterfly reaches N Europe in up to 6 broods, the last of which will attempt a very long migration back to North Africa.   Others say that the Northerly migration will take perhaps 3-4 broods but that further broods will occur on a return migration with a total of 6 in the whole migration cycle.

The one month brood cycle seems to fit well with idea of painted ladies spreading North in 6 broods whereas the 2 month cycle seems to fit better with the idea of some broods occurring on the Southerly migration

So what to make of all this? As a complete layman on this subject my preference is to believe the following.

·         The principal species of painted lady (Vanessa cardui) does not occur in South America or Australia but these do have closely related species

·         Migration for most of the annual cycle is primarily about availability of food but is started by the initial need to escape the parasitic wasp in North Africa. 

·         The 2 month brood cycle seems nearer the mark as this seems based on solid observation rather than presumptions about how quickly a brood needs to turn round to continue the annual migration. My Butterflies of Sussex book suggests that the egg to adult emergence part of the lifecycle takes about 5 weeks which leaves about 3 weeks for the adult stage

·         The idea that some of the broods occur on the return migration seems more likely and in effect means that the butterfly is in a perpetual cycle of migration.

·         Mating and broods are occurring all the time during the migration lifecycle along its route and it is the availability of food that will determine how far North the migration will spread in any one year.  

·         It seems vitally important that some viable adults make it back to North Africa to carry on the cycle while we are all shivering in a cold European winter.

The June influx of painted ladies has been likened to an invasion but I have been rather sceptical about this. Nevertheless, a recent news article on the BBC website suggested that up to 11 million painted ladies had been spotted recently heading in the direction of the UK so I’m reserving judgement. Maybe the June sightings were of an advance raiding party.

In some years these invasions do happen, so in 2009 for example millions of painted ladies reached the UK causing some amazing spectacles with caterpillars stripping huge numbers of thistle leaves. Anyone with access to The Butterflies of Sussex book by Michael Blencowe and Neil Hulme should read the chapter about the painted lady there. This has an account of an amazing mass emergence in late July 2009 of a new brood in a set aside field full of thistles near Ditchling Beacon, estimated to comprise some ¼ million butterflies.

Last year I visited Shetland in late June and early July. Shetland is not known for its butterflies – only 5 species have ever been recorded there - but on Yell, one of the most northerly isles, I duly came across a painted lady feeding on a yellow flowered shrub.

A few days later about 50 miles further south I was walking round a remote headland on St Ninians Isle with very close-cropped turf, grazed by sheep and very few wildflowers in sight. To my amazement I spotted 2 butterflies in a typical spiralling sparring match. They turned out to be painted ladies but why on earth were they there with no flowers to feed on and no thistles on which to lay eggs?  This seemed a rather strange and magical experience. However, the more I think about it the more likely it seems that they were briefly “resting” on their way further North.  Maybe they were going all the way to Iceland. Certainly, if they were on the move, the next step of the journey would be yet another sea crossing. And the sea crossing just to reach Shetland would have been quite an undertaking for such a small creature.

Back at Pulborough in 2019 I spent a whole day on Friday 5th July with the whole reserve positively teeming with butterflies and not a painted lady to be seen. Maybe the advance party had mated, laid eggs and then expired. If so maybe we will see another brood emerging in August or might it be the end of July? And might we see a lot more painted ladies descending on our now very prominent thistles very soon if the recent invasion reports prove to be accurate?

The mystery surrounding this astonishing butterfly lives on.

Anonymous