The migration of the painted lady has long fascinated scientists, artists and nature lovers alike. The longest butterfly migration on earth, it sees millions of these delicate creatures travel from the desert fringes of north Africa, across thousands of miles of land and sea, before settling in the UK. However, the migration has never truly been understood, the mysteries of the painted lady never unravelled - until now. This documentary reveals the secrets of this extraordinary phenomenon. Observed, investigated and analysed by presenter Martha Kearney and entomologist Dr James Logan, it employs groundbreaking techniques to unlock the secrets of the painted ladies.
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00:00:00Every spring, a tiny hero of the insect world undertakes a journey that almost defies belief.
00:00:11Weighing less than a gram, the intrepid Painted Lady Butterfly migrates a staggering 2,000
00:00:17miles from the Atlas Mountains in Morocco all the way to the UK and beyond.
00:00:23Right now, across Britain, hundreds and thousands of butterflies are arriving on our shores
00:00:29after an epic journey.
00:00:32I'll be following that incredible journey as it advances across Europe.
00:00:37Painted Lady.
00:00:40With the help of insect expert Dr James Logan, we'll be unpacking the science behind a migration
00:00:45of immense proportions.
00:00:46Well, that's amazing.
00:00:47It's actually following your finger.
00:00:49And I'm going to be charting the progress of our butterfly spotters from across the
00:00:53country with the help of this fantastic team.
00:00:55Quick, quick, quick.
00:00:56Painted Lady.
00:00:57And we have a dedicated army of butterfly enthusiasts on the ground helping us.
00:01:04Working closely with leading butterfly experts and using high-tech experiments in the very
00:01:10latest science, we're unraveling one of nature's greatest migratory mysteries.
00:01:16And perhaps revealing for the first time the answer to the greatest puzzle of all, just
00:01:21why do they migrate in the first place?
00:01:24This is the story of the greatest insect migration on Earth.
00:01:38Rothamsted Research in Hertfordshire is the world's leading centre in insect science.
00:01:43Here, they unlock mysteries from the insect world with some quite extraordinary technology.
00:01:50So where better to track this year's migration of the Painted Lady?
00:01:55In their grounds, we've set up a special butterfly hub, which we're sharing with more than 700
00:02:02Painted Ladies, so we can really get up close and personal with these extraordinary creatures.
00:02:09Alongside our butterfly hub, James has set up a communication centre to chart their arrival.
00:02:15All over the country, the public are getting involved by sending in their videos and pictures
00:02:20as Painted Ladies appear in Britain.
00:02:22This is the first one we've found in the garden this year.
00:02:25I think it's almost like magical when you actually see one.
00:02:28Two Painted Ladies.
00:02:29And I'm going to be doing some incredible experiments to unlock the secrets of the Painted
00:02:35Lady migration, finding out exactly how and why they do what they do.
00:02:40Yes!
00:02:41Yes, I've done it.
00:02:43Yes.
00:02:44OK.
00:02:45That's absolutely right.
00:02:46Brilliant.
00:02:48This extraordinary migration begins in the North African deserts in winter.
00:02:53After breeding and building up their numbers, they set off in spring, heading across the
00:02:59Mediterranean to Europe and into the UK on a quite remarkable journey for a creature
00:03:05as fragile as a butterfly.
00:03:10The Painted Lady's story is a fascinating one.
00:03:13I came to love butterflies through bees.
00:03:16I kept hives for many years and used to spot them out in wildflower meadows.
00:03:22Like most people, I'm enchanted by their colours and variety.
00:03:25But how many realise what this one species manages to achieve?
00:03:30The Painted Lady is a pretty familiar sight in most of our gardens, which makes it easy
00:03:35to take for granted.
00:03:37So here's everything you need to know about these mini marvels in just a minute.
00:03:46Painted Ladies are five centimetres in length and weigh a mere 200 milligrams, which is
00:03:52a tenth the weight of a paper clip.
00:03:54Yet amazingly, they can fly 100 miles in a single day, the equivalent of us running four
00:04:01marathons, and do so at speeds of up to 30 miles an hour.
00:04:07They lay their eggs on thistles and nettles, the preferred food choice for hatching caterpillars.
00:04:15Painted Ladies are a global phenomenon, the most widely distributed and most successful
00:04:22butterfly in the world.
00:04:26They really are amazing creatures, and supreme travellers, of course.
00:04:31But why do they go on such a long journey, and actually a really dangerous one?
00:04:36I've been to find out where it all begins.
00:04:50I've travelled over 1,200 miles to Morocco in North Africa.
00:04:55Flanked by the Sahara Desert and Atlas Mountains, Morocco is a dry and unforgiving place.
00:05:03It's early March, and the Painted Ladies have been busy mating and laying eggs here.
00:05:09Driving through this incredibly parched landscape, it's just so hard to imagine that this is
00:05:15where the butterflies that we see fluttering around our green English gardens come from.
00:05:22But they do.
00:05:24One man has a special fascination with them.
00:05:27Konstanti Stephanescu is the world's first male butterfly.
00:05:33One man has a special fascination with them.
00:05:36Konstanti Stephanescu is the world's leading expert on Painted Ladies,
00:05:41and has been coming here for many years to find them.
00:05:44He's a Spanish Lipidopterist from the Natural History Museum in Granollers in Catalonia.
00:05:50Konstanti has had many scientific papers published on the Painted Lady,
00:05:54and is working on his latest one.
00:05:57Since I was a boy, I was very interested in animals in general,
00:06:03and butterflies in particular.
00:06:07Well, the Painted Lady is really a very special butterfly,
00:06:12because it's one of the very few that can move long distances.
00:06:17So to understand the butterfly, you have to deal with the populations moving between continents,
00:06:24which is quite exceptional.
00:06:26Konstanti is piecing together why Painted Ladies fly from their breeding grounds here
00:06:32to Northern Europe each year,
00:06:34and is getting close to a breakthrough in understanding why they make the migration.
00:06:39I've come here to find out more, and to help where I can,
00:06:43using essential butterfly technology.
00:06:46I've been issued with some state-of-the-art equipment here.
00:06:50And here we have what every good butterfly collector needs.
00:06:56A good, old-fashioned butterfly net.
00:07:03OK.
00:07:04Well, I'm really hoping that we might see some butterflies today.
00:07:08Do you think there's any chance?
00:07:10The weather is very windy today, so it's not the best time to catch Painted Ladies.
00:07:18But there is still a possibility.
00:07:21The odds are against us.
00:07:23Not only is it windy, but it's also March.
00:07:26Conditions are still good for Painted Ladies, yet they're already beginning to leave.
00:07:31Migration is a risky business, and many will perish along the way.
00:07:36If they're somewhere which seems safe and plenty of plants and so on,
00:07:41why would they take the risk of moving on when so many of them die?
00:07:46Why?
00:07:47Painted Lady.
00:07:48Ah!
00:07:53Two. Two Painted Ladies?
00:07:55One.
00:07:56Is it?
00:08:00There, there, here.
00:08:01Not here.
00:08:03Stop, stop, stop.
00:08:05It was here.
00:08:06I think it went...
00:08:09It was incredibly close.
00:08:11I think I saw it go off that...
00:08:13Oh, there it is, there it is.
00:08:15Is that it?
00:08:17Got it.
00:08:19Fantastic, you got one.
00:08:21I got one, yeah.
00:08:23Brilliant.
00:08:25Brilliant.
00:08:27I've got it.
00:08:29I've got it.
00:08:30I've got it.
00:08:31I've got it.
00:08:32I've got it.
00:08:33Brilliant.
00:08:35So, you see that they exist, eh?
00:08:38They do exist.
00:08:39Oh, can I touch it?
00:08:40Oh, no, no.
00:08:41The wings not, because the scales will be lost.
00:08:45Oh, right, and you need those.
00:08:47Yeah, you only have to touch the body.
00:08:50Oh, that's so brilliant that you got one.
00:08:53Yeah.
00:08:54How did you see that?
00:08:55It's so tiny, that one.
00:08:56Well, I always thinking on the Painted Lady,
00:09:00so I saw the colour passing by
00:09:04and the kind of flight that has these butterflies.
00:09:08So, what are you going to do now?
00:09:10I will keep in this envelope,
00:09:12and the wings will be used for analysis.
00:09:18That really was quite extraordinary,
00:09:21when Constanti just leapt off because he'd seen a Painted Lady.
00:09:24And do you know what?
00:09:25It reminded me of those great butterfly collectors
00:09:28you see in old photos with their nets
00:09:31determined to go anywhere in pursuit of their prey.
00:09:36I leave Constanti to it, but I'll be back in the morning.
00:09:40We'll be going on a hunt for the Painted Lady's archenemy
00:09:43to gather vital evidence,
00:09:44which I hope will help us understand the riddle
00:09:47of why these butterflies migrate in the first place.
00:09:55When I left Morocco,
00:09:56the Painted Ladies were preparing to head off
00:09:59on their extraordinary journey.
00:10:01But how on earth do they know where to go to
00:10:04once they leave Africa?
00:10:06James has been trying to find out.
00:10:08So, how do our Painted Ladies navigate
00:10:11over such incredible distances?
00:10:13Well, scientists here at Rothamsted
00:10:15have been trying to solve that mystery.
00:10:17And apparently, all you need is a barrel,
00:10:20some glue, a computer,
00:10:22and, of course, a Painted Lady butterfly.
00:10:25Rebecca Nesbitt is a scientist
00:10:27with a passion for Painted Ladies.
00:10:29She specialises in butterfly migration,
00:10:32and here at Rothamsted,
00:10:33she's part of an elite entomology team.
00:10:36For this experiment,
00:10:37first you have to prepare your butterfly.
00:10:41This one has been in the fridge.
00:10:43Yeah, nice and cold.
00:10:44Exactly. Sleepy, easy to handle.
00:10:48Get it out of the pot,
00:10:50and butterflies are really obliging,
00:10:52so if you just touch the outside of their thorax,
00:10:55they flick their wings down.
00:10:58Oh, yeah.
00:10:59And we can very gently trap them on this sponge.
00:11:06Just put this mesh over so they're exposed like that.
00:11:13This experiment is going to involve
00:11:15attaching a Painted Lady to a wire
00:11:17suspended in the middle.
00:11:20We're hoping to show that Painted Ladies
00:11:22work out which direction to go when leaving Morocco
00:11:25by using the sun as a compass.
00:11:30But before this can happen, though,
00:11:32you have to do something rather bizarre.
00:11:35Next step is to shave.
00:11:40Shave the butterfly.
00:11:41Shave the butterfly.
00:11:42Just really gently rub my finger across it
00:11:46Just really gently rub my finger across it
00:11:49OK, all right, so there's not a mini butterfly razor blade
00:11:53then that you use, which is what I was expecting,
00:11:55I have to be honest.
00:11:56Sadly not.
00:11:57It's a bit disappointing, but just rub it away,
00:11:59and you're just basically taking the hairs
00:12:01off of the cuticle there,
00:12:03just sort of making a smooth surface,
00:12:06presumably so you can stick the glue on.
00:12:08Exactly.
00:12:09This is just normal contact adhesive.
00:12:11Does it harm the butterfly?
00:12:13No, not at all.
00:12:16A tiny metal rod is glued to the butterfly's back.
00:12:21What are we hoping to get out of this experiment?
00:12:23So what we're hoping to look at is
00:12:26give the butterfly a view of the sky
00:12:28and can it use the sun to find out
00:12:31which direction it's going in,
00:12:33so using the sun as a compass.
00:12:35Painted Ladies might be travelling vast distances
00:12:38by taking cues from the sun's position in the sky
00:12:41and combining it with the time of day.
00:12:43To prove this, we need to go outside.
00:12:47This is the set-up then?
00:12:49Yes.
00:12:50So I think the first thing we'll do,
00:12:52I'll just show you the flight simulator.
00:12:56Yeah, or big white barrel.
00:12:59So how does this work then?
00:13:00That rod we put on the butterfly,
00:13:03that will attach to this really tiny bit of plastic tubing.
00:13:07Once we put it on, it is free to turn,
00:13:09so the butterfly is flapping
00:13:11and it can turn in any direction it likes.
00:13:14So it has to be able to see the sun
00:13:16and then will orientate when it sees the sun.
00:13:18Exactly. It's a bit fiddly.
00:13:21I really need a steady hand to do this.
00:13:23I also need my glasses on.
00:13:29So what we need now is to calibrate it.
00:13:32So if you could just hold on to the butterfly by the rod
00:13:36and come in underneath with a compass.
00:13:38Can I use my phone compass?
00:13:40Please. Yes, that's perfect.
00:13:42I'm holding my mobile phone underneath this tethered butterfly
00:13:45as a compass, which is a little bit strange.
00:13:47I've never done that before.
00:13:49But the idea is that we're going to see
00:13:51where this butterfly heads in relation to the sun.
00:13:54Once I let it go, it should take its lead from the sun
00:13:57and fly in a northerly direction,
00:13:59unless it wants to play a bit first.
00:14:02Sometimes you can get them to follow a finger.
00:14:04Well, that's amazing. It's actually following your finger.
00:14:07Why is it doing that?
00:14:08Yeah, I don't really know. Its legs are out.
00:14:10Maybe it is looking to land.
00:14:12Looking to land, yes.
00:14:13But yeah, they often do follow.
00:14:16Are you sure you haven't trained this one?
00:14:18This is actually my pet butterfly.
00:14:22With the butterfly ready, it's time to do the experiment.
00:14:26So the data's been fed in from the barrel to this box,
00:14:29and then what happens?
00:14:31The information that that box provides,
00:14:33I'm then able to analyse it
00:14:35and plot out the flight path that the butterfly would have taken
00:14:39if it wasn't inside the barrel.
00:14:42These are some migratory flight paths.
00:14:45So you can see that these are relatively straight.
00:14:49So how does that tell you how it uses the sun to navigate?
00:14:52So what I can do is I can compare a situation like this,
00:14:56where it can see the sky,
00:14:58with a situation where I've put a lid on the barrel
00:15:01so the butterfly can't see the sky.
00:15:03And by doing that,
00:15:05you can tell whether it's using the sun to navigate by.
00:15:09Exactly.
00:15:10OK.
00:15:11If it can't see the sun, it doesn't know where it's going,
00:15:14whereas when it can see the sun, it's got a clear flight path,
00:15:18then we know there's a difference.
00:15:21The map on the left clearly shows
00:15:23a painted lady heading in the same general direction,
00:15:26whereas by blocking the sun,
00:15:28the map on the right shows the painted lady moving in random directions.
00:15:33So does this experiment definitively prove
00:15:36that the painted lady butterfly uses the sun to navigate?
00:15:39That's certainly what our evidence is suggesting,
00:15:42that when they can see the sun, then they know where they're going.
00:15:46If you put a lid on the barrel,
00:15:48then they aren't going in the right direction you'd expect,
00:15:51and actually they spin around a bit more, they appear more confused.
00:15:56What a really neat experiment,
00:15:58demonstrating that the sun is like an in-built sat-nav for our butterflies,
00:16:02an essential piece of kit for our painted ladies on the move.
00:16:16They're getting very excited about your experiment as well, aren't they?
00:16:19I mean, it's remarkable, isn't it,
00:16:21the way that they managed to use the sun to travel these immense distances.
00:16:25Yeah, it is, and it's such a simple experiment that we did.
00:16:28We used a barrel and the sun, essentially, to work it out.
00:16:31But what I couldn't quite understand from the experiment is,
00:16:34obviously, so they're using the sun for navigation,
00:16:37but the position of the sun changes all the time.
00:16:39That's right. So as the Earth rotates, the sun moves against the horizon.
00:16:43Now, we don't actually know how these butterflies managed to compensate for that.
00:16:47For other butterfly species, we know that they have an internal clock.
00:16:51I mean, we all have biological clocks.
00:16:53Body clocks. Yeah, body clock, yeah.
00:16:55These guys have a body clock as well,
00:16:57but it's in their antenna, called a circadian clock.
00:17:00And basically, what that allows them to do is to tell what time of day it is.
00:17:04So they can adjust their flight direction based on where the sun is
00:17:08and what time of day it is, essentially. It's very clever.
00:17:11It is incredible. Just think of these tiny creatures here,
00:17:15and yet they have this highly sophisticated navigation system.
00:17:19Yeah, I mean, it's a perfect example of evolution
00:17:22in terms of how to overcome adverse conditions
00:17:25and make the most incredible journey.
00:17:27And every single one of these butterflies has the ability to do that on its own.
00:17:32Well, I think these butterflies' circadian clocks tell them it's breakfast time.
00:17:35They're having a bit of orange juice, aren't they?
00:17:38Back in March, painted ladies were getting ready for their migration.
00:17:43In part two of my Moroccan adventure, I caught up with them before they left.
00:17:49EARLY MORNING
00:17:53Early morning in the Moroccan desert, and the camels are already up.
00:17:58It's late March, the end of the painted lady breeding season
00:18:02and the start of their incredible migration.
00:18:05It's so windy here, and if I'm having to battle against it,
00:18:10what on earth is it like for a butterfly?
00:18:13Yet that's exactly what the painted lady does.
00:18:16They fly over this parched desert terrain and right over those mountains there
00:18:22to make it all the way to Europe and, of course, to Britain.
00:18:31I'm on my way to meet up with Konstanti Stefanescu again.
00:18:35He's the most respected entomologist in his field
00:18:38and has had over 100 scientific papers published.
00:18:42From environmental impacts on butterflies to population declines and painted lady migration,
00:18:48what he doesn't know about butterflies isn't worth knowing.
00:18:52Konstanti's latest work is close to revealing ground-breaking science
00:18:57that will shed new light on why painted ladies migrate.
00:19:02He's collecting painted lady caterpillars.
00:19:05They're under attack from another insect,
00:19:08and it's the relationship between them that he's particularly keen to investigate.
00:19:13To find a caterpillar, first you have to find the plants they live on.
00:19:18This is one of the very good host plants, isn't it?
00:19:22Yeah, look, there are many nests here.
00:19:25Host plants provide food for caterpillars.
00:19:29Each species of butterfly has a specific plant on which they lay their eggs.
00:19:35Are the plants that the painted lady likes?
00:19:38Yeah, in fact, the painted lady is one of the few butterflies
00:19:43that can use many different kinds of plants,
00:19:47even if they prefer the caesars and the mallows.
00:19:51What's that caterpillar doing now?
00:19:53I see with the binoculars that it's producing some silk,
00:19:58and, well, it's building the nest.
00:20:01Once built, the nest will form a snug tent from which the caterpillar emerges to feed.
00:20:07As it grows, so too does the tent.
00:20:10I'll just get this little caterpillar here.
00:20:14It's clinging on.
00:20:16There, is that all right? Not too damaged?
00:20:18And there's another much smaller one over here.
00:20:23There we go.
00:20:26It's astonishing to think that this caterpillar, once turned into an adult,
00:20:32could fly all the way to Britain and, who knows, even end up in my back garden.
00:20:44Collecting painted lady caterpillars is easy when you know where to look.
00:20:48A far greater challenge for Constante is what lurks within them.
00:20:53He's looking for signs that painted lady caterpillars have been attacked.
00:20:58But by what?
00:21:02So this is a mass of cocoons of the main enemy of the painted lady.
00:21:08This tiny wasp, the adult wasp,
00:21:12what it does is to search for the larva of the caterpillar of the painted lady
00:21:18and lay the eggs inside the body of the caterpillar.
00:21:22Once they hatch, the wasp larvae begin eating the painted lady caterpillar from the inside out,
00:21:28eventually forming a silky mass around the caterpillar corpse
00:21:32before finally emerging as adult wasps.
00:21:35I estimate that maybe 60, 70% of the caterpillars of the painted lady
00:21:41are killed by this parasitoid.
00:21:44But I can tell when you found that you were rather excited to find these horrible creatures.
00:21:50So what are you going to do with this now?
00:21:52I will keep this mass of cocoons inside the vial, waiting for the adults to emerge.
00:22:00So our butterflies in Morocco are under serious attack from a deadly parasite.
00:22:05It's the possible link between the parasitic wasps and painted lady migration that Constante is investigating.
00:22:12One main part of the research is to see how many of these caterpillars will die
00:22:18because of the parasities by the wasps.
00:22:21And so every night I have to check if some of them are already dead or not.
00:22:28So actually you're quite interested if one's dead.
00:22:31Yeah, I hope that some of them will die.
00:22:35A curious Constante is compiling his evidence.
00:22:39He'll take the caterpillars home with him to Spain.
00:22:42The wasps they might contain could be a key component in his migration research.
00:22:49I've got to go home soon, but I can't leave without catching at least one painted lady, can I?
00:22:58This morning I'm on a mission. This is my last chance.
00:23:04There's one here.
00:23:09Yeah.
00:23:11Ha, got one.
00:23:12Here's one.
00:23:13Oh, fantastic. I'm so pleased. I'm so pleased.
00:23:17Yeah, this butterfly is more easy to catch than a fresh butterfly.
00:23:23Oh, come on. It's my first painted lady. What are you doing here?
00:23:29Well, there it is. My first painted lady. And it's an incredible experience.
00:23:35I'm glad I'm collecting it for science rather than just for a collection.
00:23:40Painted ladies are definitely out this morning, and my eye is in.
00:23:45Oh, hang on. There it is.
00:23:47Oh, yeah? Here's the painted lady.
00:23:54No, no, no.
00:23:57It's still there?
00:23:59Yeah. Yeah.
00:24:01Oh, yeah.
00:24:03Okay, your second painted lady.
00:24:05Two. That's great. I know my technique was a bit useless, but I got it. I did get it. Number two.
00:24:12Number two, yeah. But you see, again, this is a very, very old butterfly.
00:24:17Show a bit of gratitude. Stop saying it's old and rubbish. Be pleased I'm doing your work for you, for free.
00:24:25Thank you. Thank you so much. It's been a really good day, no?
00:24:30Yeah.
00:24:31Larvae, adults. I think it's time for a tagine, no?
00:24:35Tagine. Now you're talking. We can celebrate the capture of the painted ladies with a nice tagine.
00:24:42Constante managed to collect over 100 caterpillars in Morocco,
00:24:46which, depending on how many develop into butterflies and how many are killed by the wasps,
00:24:51could shed new light on understanding the painted lady migration.
00:24:55Scientists like Constante at the forefront of lepidoptery rely on centuries of research by enthusiastic amateurs.
00:25:02Many of their specimens are now in the Natural History Museum in London,
00:25:07home to the largest collection of painted ladies in the world.
00:25:11This is my very own private night in the museum.
00:25:15The echoing hall is now all the crowds have gone.
00:25:19We normally think of dinosaurs like Diddy in the Natural History Museum,
00:25:23but actually there are more than 30 million insect specimens,
00:25:28as well as a whole load of world-renowned excellence.
00:25:31So where better a place to come than here to find out more about painted ladies,
00:25:37those incredible flying machines.
00:25:39Well I'm really looking forward to being able to find out more about the kind of detail
00:25:45anatomy of the painted lady.
00:25:47Dr Blanca Huertas is the senior curator of the museum's butterfly collection.
00:25:52There are over 4 million butterflies here, including painted ladies from around the globe.
00:26:00So this is where they all are.
00:26:02Yeah, so this is the corner in the world's biggest collection of butterflies
00:26:07where we have the painted ladies.
00:26:10And how many painted ladies have you got here?
00:26:13We have probably about 3,000 specimens.
00:26:16We have specimens from all over the world in here.
00:26:20Painted ladies are found in more countries than any other butterfly,
00:26:24making them also one of the most successful.
00:26:27Just in these six, seven boxes we have specimens from around 40 countries.
00:26:32We've got things from Turkey, we've got things from Morocco,
00:26:36We've got things from Turkey, we've got things from Morocco,
00:26:39Sri Lanka, everywhere.
00:26:42And what kind of time span then do you have?
00:26:45We got collections back into early 1800s in here.
00:26:49Do you notice differences in the patterns?
00:26:52Yeah, that's why we have long series of butterflies.
00:26:55Some have differences, not just on the upper side,
00:26:58but also if you look into the underside.
00:27:01They're very distinctive.
00:27:02They're very different to how they actually look in the upside.
00:27:06The rich colours are used for courtship and camouflage.
00:27:10Open wings display your wares to other painted ladies.
00:27:14Closed, they blend in with the background
00:27:16to help them avoid being eaten by predators like birds.
00:27:20Interestingly enough, the females are much bigger and also kind of fader.
00:27:25So sometimes you see lots of butterflies,
00:27:28really bright colours, and they are only males.
00:27:31The males are the ones who are really, really bright.
00:27:33The females are a little bit more dull.
00:27:36More dull, more faded.
00:27:38It's an expensive business, evolutionarily speaking.
00:27:41Producing colour with all of these pigments implies a lot of energy.
00:27:46So the females need that energy in other things,
00:27:49like giving birth to the next butterflies, to the next generation.
00:27:53So the males still can't afford it,
00:27:55but the females are very careful how they spend their energy.
00:27:57So the males are spending all their energy looking good
00:28:01and the females are back at base breeding.
00:28:04Absolutely, and if they don't do that, they don't succeed finding a mate.
00:28:08The males are the ones showing up
00:28:10and the females are usually the ones who select those good-looking males in butterflies.
00:28:17Our fascination with butterflies goes back centuries.
00:28:22They were valuable and coveted treasures back in the day.
00:28:26Dr Hans Sloane was an Irish-born scientist and keen collector in the 1600s.
00:28:32He amassed one of the greatest collections of plants and animals of his time.
00:28:39His curiosities, as they were known then,
00:28:42are the founding core of the museum's collections.
00:28:47We're now in the historical collections.
00:28:50What a historical collection as well, these incredibly big books.
00:28:53That's the Crown Jewels, actually.
00:28:55We've got the oldest specimens of plants preserved in here.
00:28:59That's not in time.
00:29:01But not only the oldest specimens of plants,
00:29:04but I brought you today because we have in here,
00:29:07pressed in the herbarium sheets of Mr Hans Sloane,
00:29:11we've got the oldest painted lady ever collected
00:29:14and pressed and preserved here in the Natural History Museum.
00:29:17The oldest painted lady?
00:29:19Yes, so we're going back into 1600s,
00:29:21so we're going to see a snap in time with the plants
00:29:24where this butterfly was flying around, and we're going to see in a minute.
00:29:28And this is part of this incredible historical collection which Hans Sloane started?
00:29:32Yes, that was collected by himself
00:29:35and preserved by the Reverend Adam Buddle.
00:29:40OK, let's go and see what Adam Buddle had in his scrapbook.
00:29:45Adam Buddle was a botanist in the 1600s.
00:29:48Amateur collectors were rife in those days.
00:29:51His vast knowledge of plants meant his collections
00:29:54were more respected and relevant than most.
00:29:57At the same time the naturalists were collecting plants,
00:30:00they also pressed some butterflies in here,
00:30:03and this one in particular is a very, very old specimen.
00:30:06That's amazing. How old is that?
00:30:09This was collected back in the late 1600s.
00:30:13This is the oldest painted lady we have knowledge of,
00:30:17and it's in here in the Natural History Museum collections.
00:30:20And did you know it was here?
00:30:22It's kind of a recent discovery for us, and it's very exciting to show you.
00:30:27I can see that it's a painted lady,
00:30:29and it's been pressed in the same way that we press wildflowers.
00:30:34Yeah, and back in the pre-1700s,
00:30:36that was the method to preserve specimens.
00:30:39Collected flowers and plants were pressed onto book pages
00:30:42known as herbarium sheets.
00:30:44Butterflies were preserved with the flowers they feed on,
00:30:47a practice that's still done today.
00:30:50Look here, and we have it written in little shaky, quite shaky handwriting,
00:30:54The Painted Lady.
00:30:56They have a common name, a vernacular name.
00:30:58It is still in use after 300 years.
00:31:01I just love looking at the detail of all of this.
00:31:04It's almost like a work of art, this.
00:31:06It's so beautifully, the way he's placed the butterflies
00:31:09in amongst the grasses.
00:31:11That was preserved by Reverend Adam Badal.
00:31:15You probably have heard of all the butterfly bushes with Badal, yeah?
00:31:19Yes.
00:31:20And that's where that name came from.
00:31:23Over many years, he compiled a definitive English plant guide
00:31:26that was never published.
00:31:28The original manuscript is preserved here.
00:31:31In later years, the well-known Buddleia plant, or butterfly bush,
00:31:35was named in his honour.
00:31:37Do you know, all the time that I've talked about Buddleia,
00:31:40I've got Buddleia in my garden,
00:31:42I didn't realise it came from a person,
00:31:44the person who, all those years ago, collected these butterflies.
00:31:47A great naturalist, as you see.
00:31:49Lots of care, lots of notes,
00:31:51and detail on these collections, well preserved.
00:31:54So a very important snapping time.
00:31:56Absolutely. Probably the only one, really.
00:32:01It really has been so interesting to come behind the scenes
00:32:05at the Natural History Museum,
00:32:07where they've been studying butterflies for generations.
00:32:10And, you know, insects are the most successful animals on the planet,
00:32:16and it's easy to see why painted ladies fall into that category.
00:32:21Back in March, our painted ladies had been breeding in Morocco in large numbers,
00:32:26ahead of travelling across Europe on their epic migration.
00:32:30The life cycle of the butterfly
00:32:32is one of the most fascinating in the natural world.
00:32:36As painted ladies only live for up to three weeks, they breed quickly.
00:32:43When a male finds a female, he has to win her affection.
00:32:48To do this, he uses perfume.
00:32:52Chemicals called pheromones are intoxicating to females at close range.
00:32:59If she likes it, they settle down to mate.
00:33:10They stay locked together for up to an hour, sunbathing at every opportunity.
00:33:18Eggs no bigger than a pinhead are laid on plants the caterpillars feed on.
00:33:24Jewel-encrusted thistles glisten for five days before bursting into life.
00:33:32Caterpillars gorge themselves from the moment they hatch and begin to grow,
00:33:37shedding their skin five times before reaching full size.
00:33:41In just ten days, the caterpillar is a colossal hundred times bigger than when it hatched.
00:33:49Suspended on a silk pad, it splits its skin one last time,
00:33:54revealing a case like chrysalis or pupa.
00:33:57Inside the chrysalis, the caterpillar reduces itself to a DNA soup,
00:34:02reconstructing into something else entirely.
00:34:05Two weeks later, a Painted Lady Butterfly emerges, and the cycle starts all over again.
00:34:20We're following this year's Painted Lady Butterfly migration,
00:34:24and our communication centre is buzzing.
00:34:27Piece by piece, scientific experiments, eyewitness accounts,
00:34:32and the world's leading experts are helping us unravel the mysteries of an extraordinary journey.
00:34:40We know it began in Morocco at the end of the winter breeding season in March.
00:34:45Our Painted Lady is then touched down in Catalonia in June,
00:34:49where she is the first female Butterfly in the world.
00:34:54Our Painted Lady is then touched down in Catalonia in Spain to refuel,
00:34:58and this is where I caught up with them next.
00:35:09To get to Spain, our Painted Ladies have had to overcome extreme desert conditions
00:35:15and to climb to incredible heights, navigating mountains as high as 13,500 feet.
00:35:23Many will have died the voyage taking its toll, or been eaten by predators.
00:35:30An exhausted Painted Lady is easy pickings for a hungry frog.
00:35:35Those that do make it this far are rewarded with better conditions.
00:35:41These beautiful olive groves just brimming everywhere you look with spring wildflowers.
00:35:47I mean, it couldn't be further away, could it, from the mountainous, rocky deserts of Morocco.
00:35:53But Catalonia is the first stop for many of the Painted Ladies we saw.
00:35:58It's 1,500 kilometres from their breeding ground,
00:36:02and they're still only halfway from their final destination.
00:36:10I met up with Constanti at the Granollers Natural History Museum in Catalonia.
00:36:16He's been studying the specimens I helped him collect in Morocco,
00:36:20and I'm keen to discover what he's found out.
00:36:22But not before indulging my passion for all things butterflies with him first.
00:36:27I love these old illustrations.
00:36:30They're incredible, aren't they, the detail on some of these.
00:36:33Yeah, they are. Good meat.
00:36:36Painted Lady and peacock.
00:36:38Do you think it is there's something about the beauty of butterflies that makes people want to study them?
00:36:44Oh, yeah, of course.
00:36:46There are many more people that are attracted by butterflies than by beetles, for example.
00:36:53And you've got quite a few collections here in the museum.
00:36:56Yeah, and one of these collections is my own collection that I did when I was...
00:37:02Is this yours?
00:37:03Yeah, this is mine.
00:37:06Here you are.
00:37:07Oh, gosh.
00:37:09Well, it's very useful to start a butterfly collection, to learn to distinguish the species.
00:37:17Well, even I can get some of these.
00:37:19OK, that's peacock.
00:37:21That's peacock.
00:37:22Red Admiral.
00:37:23Red Admiral.
00:37:24OK, and if I haven't got the Painted Lady by now, you'd be despairing of me, wouldn't you?
00:37:27Yeah.
00:37:29Around the world, it's not Constante's beloved painted ladies that get all the attention.
00:37:35Until recently, it was thought the monarch carried out the longest butterfly migration.
00:37:41Travelling 3,500 kilometres from the US to Mexico, it often returns to the same trees where its ancestors were born.
00:37:51Thousands form a spectacular butterfly blanket in the process, which I've seen myself in a Mexican forest.
00:37:58The monarch might be a headline-grabbing superstar, but it's not a patch on the Painted Lady.
00:38:07I'm amazed by how much material there is about the monarch butterfly, but really comparatively little about the Painted Lady.
00:38:16Well, I'm quite envious about how much has been done and is being done on the monarch
00:38:23and the little research that is being done on the Painted Lady.
00:38:28But on the other hand, this means that we still have many, many things to explore on the Painted Lady, which is nice.
00:38:34But actually, the Painted Lady is the champion, isn't it?
00:38:38I think so.
00:38:39I think, well, I know that for sure the Painted Lady can fly more than 4,000 kilometres in the whole cycle of migration.
00:38:52And the monarch can do as much as 3,500 kilometres, so at least the Painted Lady can win the monarch in this sense.
00:39:06Constante is trying to solve a migration mystery that's occupied his work for the last 10 years.
00:39:12After numerous field trips to Morocco collecting live caterpillars,
00:39:16he's slowly unravelling the effect a sinister parasite might have on the Painted Lady migration.
00:39:22So all those specimens that you collected in the heat of the Moroccan desert, you've brought them back here.
00:39:29What have you been doing with them?
00:39:31I brought back all these larvae until they pupate or until they die because they were attacked by the wasps.
00:39:40I recognise the cocoon from the caterpillars that you showed me in Morocco.
00:39:46And what's emerged from that white mass?
00:39:49Well, inside this mass there are many cocoons, very small cocoons, and from each cocoon will emerge one of these wasps.
00:39:59These are sisters that come from a single female that lay the eggs inside the caterpillar.
00:40:08But are you telling me that all these wasps came from one caterpillar?
00:40:13From one caterpillar, yes.
00:40:15Maybe there can be between 50, 60, 70, depending.
00:40:20Well, it's almost as if each one of these is then able to lay 50 eggs in a caterpillar.
00:40:26I mean, they could wipe out the Painted Lady, couldn't they?
00:40:29Yeah. In Morocco we have seen that most of the populations of Cotasia, of these wasps, are composed only by females.
00:40:38They can reproduce without the males.
00:40:41So every single wasp can parasitise, can attack, and lay eggs in a new Painted Lady caterpillar.
00:40:50So the risk is terribly high.
00:40:53A good Painted Lady breeding season inevitably becomes an even better one for the parasitic wasps.
00:41:00Constanti believes the wasps have a key role to play in Painted Lady migration.
00:41:05It won't be long before he can finally reveal his findings.
00:41:11Outside in Catalonia, the ladies are already here.
00:41:15The ones who managed to escape the parasitic wasps are enjoying the Spanish sun.
00:41:20So why is it you think that the Painted Lady has come to places like this?
00:41:25Well, because here they find exactly what they need to have a big success for reproduction.
00:41:33So you see that everything is green, there are flowers everywhere, there is nectar for the adults, there are food plants everywhere.
00:41:43But this lasts only a short period.
00:41:47So the next generation has to move to the north to track the same situation in Central Europe or Northern Europe.
00:41:57So it's the strategy of this long-range migrant, which is the Painted Lady.
00:42:05So not all Painted Ladies fly to Britain in one go.
00:42:08Many stop over somewhere like this to feed and breed,
00:42:12their offspring emerging hardwired to continue migrating to Britain and beyond.
00:42:17It's a relay race, with one generation passing the baton to the next and so on.
00:42:23Some, however, emerge from a chrysalis in Spain and don't migrate any further at all,
00:42:29choosing instead to stay and spend their short three-week life breeding while food is abundant.
00:42:37Their main food plant, thistles, are seasonal.
00:42:40As they die off in one country, they bloom in another.
00:42:43So it makes sense for some Painted Ladies to migrate and follow them.
00:42:48Much of what Constanti had shown me in Spain involved the Painted Lady's arch-enemy wasp.
00:42:54What he'd kept from me was worth the wait.
00:42:57So here I have some of the butterflies that I raised from the caterpillars that we collected in Morocco.
00:43:06So these are all... right, OK.
00:43:10One of the caterpillars Constanti brought back from Morocco didn't fall foul of the Cortesia wasps
00:43:16and instead went through its full transformation into a butterfly in his office.
00:43:21Oh, yes, I can see them. Still the legs are moving.
00:43:24That's a male, so we can release this male at the hilltop.
00:43:29Oh, great.
00:43:30Probably he will enjoy the place.
00:43:32I'm very nervous about doing this because they're so delicate.
00:43:36OK, all right.
00:43:38OK, like this?
00:43:39Just here, yeah.
00:43:41Yeah.
00:43:42OK, that's incredible.
00:43:44This butterfly, which came from a caterpillar we picked up in Morocco, has never flown before.
00:43:50I'm just going to let it go.
00:43:52Off you go, off you go.
00:43:54Oh, look, it needs to warm its wings up a little bit first, do you think?
00:43:58Well, I think it's more or less ready.
00:44:01OK, I'm going to let you take your time.
00:44:04A virgin flight is a big deal.
00:44:09It's really fluttering.
00:44:12Come on.
00:44:13Oh, there he goes.
00:44:16He's doing quite well, eh?
00:44:18Not bad for a first flight.
00:44:20A hesitant start, maybe,
00:44:22but this butterfly will be migrating north to the UK alongside the others within days,
00:44:28unless, of course, it decides to stay and breed for its short life instead.
00:44:39So why are some painted ladies driven to migrate and others not?
00:44:44James is getting exclusive access behind the scenes here at Rothamsted to find out.
00:44:50I've been given special permission to get inside this high-security facility here at Rothamsted
00:44:56to find out some of the latest cutting-edge research on insect migration.
00:45:01I feel quite privileged.
00:45:08This is pretty awesome.
00:45:10It's like being in a spaceship in a sci-fi movie or something like that.
00:45:13It's also a little bit spooky, but I believe this is where the magic happens.
00:45:20Here they are studying migratory moths to understand
00:45:23what makes some insects of the same species migrate and others not.
00:45:27The results should apply to migrating butterflies as well.
00:45:33What on earth is going on in this experiment?
00:45:35Well, we use a number of techniques in our lab to study insect migration,
00:45:39and these are our roundabout-style tethered flight mills.
00:45:42OK, roundabouts for moths.
00:45:45That's right, yeah.
00:45:46So, basically, we use this technique to investigate the flight capability
00:45:50of different individuals of the same species,
00:45:53using this technique to identify good flyers and poor flyers
00:45:57so we can try to understand the genetic control of migration.
00:46:01The moths on the roundabouts are flying on their own accord.
00:46:04It's their natural flight driving them,
00:46:06and their every move is being measured.
00:46:09OK, so how do you define a good flyer and a poor flyer?
00:46:12Is it just all to do with how far they fly, or...?
00:46:14We place the moth onto this roundabout,
00:46:17and then we just allow the moths to fly overnight,
00:46:19and then those individuals which have flown a long way,
00:46:22which might be 30 kilometres in a single night,
00:46:24we can put into one category,
00:46:26and then we might have others that only fly a few hundred metres.
00:46:29And why do they do that?
00:46:31Why do you have some long-haul and some short-haul flyers?
00:46:34Some individuals can be highly migratory, and others hardly move at all,
00:46:38and they do this in response to different conditions
00:46:41that promote migration, or not, as the case may be.
00:46:44OK, but something in the environment or something can change
00:46:47and trigger them to become a long-haul flyer.
00:46:50That is exactly what happens,
00:46:51and so it might be the environmental conditions, the weather,
00:46:54it might be the quality of the host crops that they're feeding on.
00:46:58It can turn them into a migratory, or it can turn off the migratory genes.
00:47:01What are those genes actually doing physically to the insect?
00:47:04How do they help with the migration?
00:47:06Well, there's a whole number of genes that are being overexpressed,
00:47:09but some of them are involved with the availability of flight fuel,
00:47:12which in these insects is body fat.
00:47:14And so there are a number of genes that are associated
00:47:17with turning fat into a fuel that they can use.
00:47:20There are also genes which are associated
00:47:22with the production of strong, very active flight muscles.
00:47:26And so, again, those long flyers, they have the strongest muscles.
00:47:30The genes associated with those are turned up to maximum, if you like.
00:47:34Wow. Does this apply to other insects?
00:47:37Whatever we learn here would be perfectly transferable
00:47:40to all butterflies and moths that migrate,
00:47:42and so it would be relevant to the Painty Lady story.
00:47:45So what this research is revealing is that variations in environmental conditions
00:47:49appear to switch certain migratory genes on or off.
00:47:53Some are fatter, some are fitter,
00:47:55some develop bigger flight muscles and so on.
00:47:58Fatter ones with stronger muscles
00:48:00are likely to continue migrating to the next country,
00:48:03while others are better equipped to stay in one place and breed.
00:48:15We're monitoring the 2016 migration at Rothamsted
00:48:19and know that Painted Ladies left Morocco in March.
00:48:22By April, they were breeding in Catalonia.
00:48:25I came back from there expecting them to be navigating through France
00:48:29and hitting our shores in early May.
00:48:32May came, but not many Painted Ladies.
00:48:38Brutal weather in northern Europe earlier this year
00:48:41hit them from all sides,
00:48:43so it's no surprise then that the class of 2016 is late arriving.
00:48:50In May and early summer,
00:48:52northern Europe had its highest rainfall for over 100 years.
00:48:57Rising river levels threatened to decimate towns in Germany.
00:49:01Paris flooded, and the UK had one of its wettest Junes ever.
00:49:06An average Painted Lady weighs 200 mg.
00:49:09Large raindrops can weigh more than 70 mg,
00:49:13so flying through rain is virtually impossible.
00:49:16Added to that, butterflies need to warm up in the sun to fly efficiently,
00:49:21so bad weather is bad news for Painted Ladies.
00:49:35Back at Rothamsted, the Painted Ladies in our hub
00:49:39are making the most of what we put out for them.
00:49:42The butterflies love the sugar that they get from the oranges,
00:49:45and that's one reason why they migrate, why they go from Morocco to Spain,
00:49:50is because the food plants dry up in one country
00:49:53and they need to move on to find fresh plants like these here,
00:49:57the buddleia which you may have in your garden that the butterflies enjoy so much.
00:50:02But not all of them travel up through the western Mediterranean.
00:50:06Some head east instead, as we're going to see.
00:50:11When Painted Ladies leave Morocco,
00:50:13they don't all head one way to northern Europe.
00:50:16Some embark on a route to eastern Europe instead.
00:50:20Each year, the different routes have varying degrees of success.
00:50:24Through April and May this year,
00:50:26great numbers descended on Corfu and Crete via the eastern route,
00:50:30but comparatively few arrived in northern Spain and Britain due to bad weather.
00:50:35By expanding their distribution across different routes,
00:50:39the butterflies breed successfully in enough countries to keep their overall numbers up.
00:50:48While some emerge from their cocoons and continue migrating,
00:50:52others emerge and don't travel on, staying instead to breed a further generation.
00:50:58That's why we see more and more Painted Ladies as the summer progresses.
00:51:04In the communications centre,
00:51:07James has been mapping the progress of our Painted Lady migration as it's unfolded.
00:51:13What have you been looking at?
00:51:15Well, I'm just mapping out the routes, actually, of some of these butterflies.
00:51:19You started off here, didn't you, in Morocco?
00:51:22South of Marrakesh, really near to the Sahara Desert.
00:51:25So, of course, they can start off pretty much anywhere across this northern African belt here
00:51:31and sort of head northwards.
00:51:33Let's draw this out. So you started about here and then you moved up to Catalonia, didn't you?
00:51:38Yeah, it's the kind of north of Spain.
00:51:41Imagine being the size of a butterfly and having to fly that far.
00:51:44You'd think it would take a long time, but actually scientists have modelled it
00:51:47and they reckon that it could take as little as 20 to 36 hours.
00:51:50And that's with a tailwind, obviously, and then flying at an average 15 kilometres per hour.
00:51:55And then they head on, they just carry the drive northwards.
00:51:58That's right. So the ones that you saw in Catalonia probably will make their way
00:52:03or already have made their way or are starting to make their way up here.
00:52:07But over here, on the other hand, let's do this in a different colour
00:52:10because it kind of seems to be a second route, certainly with the sightings.
00:52:13The butterflies seem to be heading up perhaps from Libya here,
00:52:16maybe the coast of Egypt, up to Crete.
00:52:19So lots of sightings in Crete and other parts of Greece as well.
00:52:22So this seems to be a bit of a hot spot this year with our butterfly spotters.
00:52:26I love the idea that there are all these butterfly enthusiasts
00:52:30who are sitting there waiting in their gardens for the arrival of the Painted Lady.
00:52:34The eastern route, having benefited from good weather throughout the year,
00:52:38is reaping rewards and none more so than Crete.
00:52:42So Crete has been an absolute hot spot and let me prove it to you actually
00:52:45because one of our butterfly spotters has sent us in a video.
00:52:49This is from a guy called David Cook who is on holiday in Crete at the moment
00:52:55and he sent in this footage of Painted Ladies.
00:52:58Hi, I'm Dave Cook. I'm holidaying on the Greek island of Crete.
00:53:03It's a bit like a motorway service station for butterflies.
00:53:06I've never seen so many Painted Ladies in one place.
00:53:09So he's counted them and there's between 50 and 100 per bush.
00:53:14That's amazing.
00:53:16He's only ever seen one or two in the UK.
00:53:19So he's booked this holiday to Crete hoping that the Painted Ladies were going to be there
00:53:22and lo and behold they're here so he's ditched his family.
00:53:25They're on the beach. They're on the beach just having a holiday.
00:53:28He's out butterfly spotting for us. It's brilliant.
00:53:31I'm feeling a butterfly divorce coming on.
00:53:34That's exactly what I would do on holiday.
00:53:36Really?
00:53:37Absolutely. That's my wife.
00:53:39I'm not going on holiday with you.
00:53:42Coming out of such a horrendous June,
00:53:45it's no surprise our British spotters didn't have as much luck as Dave Cook in Crete.
00:53:52So how can scientists detect when Painted Ladies do arrive in the UK?
00:53:57James has the answer.
00:53:59We know that thousands upon thousands of our Painted Lady butterflies
00:54:03make this incredible journey every single year
00:54:06but it's not as if we see them sort of flocking past our heads
00:54:09and that's because they do it in a rather efficient way.
00:54:12I like to think of it as the insect highway in the sky
00:54:15flying at these incredible heights at incredible wind speeds
00:54:18and these things can survive this. It's actually amazing.
00:54:21And the way that scientists know this is by using this,
00:54:24the vertical looking radar.
00:54:27It might appear little more than a satellite dish
00:54:30but as the old saying goes, never judge a book by its cover.
00:54:34Insect migration expert Dr. Jason Chapman
00:54:37is the custodian of this cutting edge piece of kit.
00:54:40So this dish is basically reflecting a beam up into the sky?
00:54:44That's right, yeah. It's like shining a searchlight into the sky.
00:54:47So basically we're hoping that insects will pass through that beam
00:54:50so we can detect them.
00:54:52So it's kind of a cone shape as it's going up into the sky?
00:54:54Yes, so it's a very narrow cone. It just spreads out a little bit
00:54:57but by the time it gets to our highest altitude, which is 1.2 kilometres,
00:55:01it's still only 30 metres wide.
00:55:03So it is really quite a narrow sliver of the sky that we're sampling.
00:55:06On a sunny summer's day like today,
00:55:08we might expect maybe 2, 3, 4, 5 thousand individual insects.
00:55:11Thousand?
00:55:12Yes.
00:55:13Different insect species fly at different heights.
00:55:15Painted ladies pass through the beam
00:55:17at a much higher altitude than most butterflies.
00:55:19But it takes more than just the height they fly at
00:55:22to confirm they're painted ladies.
00:55:24The reason that we can identify and classify different kinds of insects
00:55:28is because the different shapes and sizes
00:55:30and the different wing beating frequencies
00:55:32produce very different signals.
00:55:34So when you see a butterfly in the sky with the radar,
00:55:36how do you know it's on the migration?
00:55:38When you see hundreds of individuals
00:55:40flying over on the same day in the same direction,
00:55:42then you can see that there must be, you know,
00:55:44a population-level migration going on.
00:55:46For us to see what the vertical radar sees at altitude,
00:55:49we need to go inside.
00:55:51So this is the computer that controls the operation of the radar.
00:55:55As insects pass through,
00:55:57we'll get a peak as an individual flies through the beam.
00:56:00Ah, yes.
00:56:01Yeah, so you can see the sort of peaks happening.
00:56:03They're quite quick, though, just within a couple of seconds.
00:56:07This graph represents a painted lady butterfly.
00:56:10That's right.
00:56:11It's a signal that we recorded from a painted lady flying over the radar.
00:56:15So that peak tells you how big the insect is?
00:56:18Yes.
00:56:19So the magnitude of the peak,
00:56:21the amount of power that's being reflected,
00:56:23that will give you some indication about the overall size of the insect.
00:56:26OK.
00:56:27And along this bottom axis, we've got time.
00:56:29And it's three seconds here.
00:56:31So within a couple of seconds,
00:56:32that insect of that size passed through the beam.
00:56:34That's right.
00:56:35And so in two seconds, it passed through our beam,
00:56:37which is about 20 metres diameter.
00:56:39Yeah.
00:56:40So a very quick calculation tells you it was travelling at 10 metres per second.
00:56:44That's about 40 kilometres an hour.
00:56:46This one clearly was on the move.
00:56:48This must have been part of the migration.
00:56:50Incredibly, they do so at heights of over 1,000 metres.
00:56:54Only one type of butterfly travels north in large numbers
00:56:57and at that height this time of year.
00:57:00So they can only be painted ladies.
00:57:02Maps from previous years provide confirmation.
00:57:06Each of those black bars is related to the numbers of individuals
00:57:10that were flying in that direction.
00:57:12And that's what we would expect during the early spring migration
00:57:15as these butterflies are travelling northwards.
00:57:18If the painted ladies were not migrating north,
00:57:20the map would look something like this.
00:57:23Multi-directional flight paths indicate an insect
00:57:26with no particular place to go.
00:57:29I've had an insight into what's normally a completely hidden part
00:57:33of the painted lady butterfly's migration and its world.
00:57:37It's allowed scientists to unravel and unlock some of the amazing secrets
00:57:42of this incredible migration that these tiny, fragile butterflies make.
00:57:47When our painted ladies do finally arrive,
00:57:50they're going to need refreshment.
00:57:52So how can we prepare for their arrival?
00:57:56Long-distance athletes need regular refuelling,
00:58:00otherwise it affects their endurance.
00:58:02And you know it's exactly the same thing with painted ladies.
00:58:06When they come here after that monumental journey,
00:58:09they're hungry.
00:58:11They need nectar, sugar, for energy.
00:58:13And there are all sorts of things that we can do in our own gardens
00:58:17to help them prepare for their arrival.
00:58:20Patrick Barkham is going to show me how.
00:58:24Patrick is a natural history journalist and author.
00:58:27He's so obsessed with butterflies that in the space of one year,
00:58:32he tracked down every British species for a book.
00:58:36He's turned his Suffolk garden into a wildlife haven.
00:58:41Why is this so particularly good for butterflies?
00:58:44Well, it's because they have a lot of energy.
00:58:47Why is this so particularly good for butterflies?
00:58:50Well, it's very simple really.
00:58:52I planted some typical wildflower mixes.
00:58:54I tried to find mixes that use native species to Britain,
00:58:57not just exotic mixes.
00:58:59It looks like a sort of fairly scruffy lawn to some eyes,
00:59:03but there's loads of grass-feeding butterflies
00:59:06that actually lay their eggs.
00:59:07The caterpillars feed on the grasses.
00:59:09And then of course you chuck in a load of wildflower mix
00:59:11and you get these lovely wildflowers on which the butterflies can nectar.
00:59:14And you've got some fantastic daisies here.
00:59:16These are great, and these surprised me
00:59:19because I saw 19 painted ladies on these a couple of weeks ago,
00:59:23just round the corner.
00:59:24So the painted ladies come in on this enormous journey
00:59:27and it's seeing my oxeye daisies and it's dropping down to refuel.
00:59:30You know, it's a lovely thing.
00:59:32And then I went to look for them the next day
00:59:34and they'd all disappeared again,
00:59:35so they'd all just continued their journey north.
00:59:37So all that effort, you've planted these fantastic wildflowers
00:59:41and then they just disappear.
00:59:43They race through your garden in 30 seconds
00:59:45and have a quick fuel stop and then zoom off again.
00:59:48To me that's great and that's enough,
00:59:51but the next thing is you want them breeding in your garden.
00:59:55You really want their food plant, thistle.
00:59:57And thistle's not such an easy sell, is it?
00:59:59No.
01:00:00I've got these enormous thistles by my front door.
01:00:03It's quite hard, isn't it, to ask keen gardeners to let thistles grow.
01:00:08It's a real struggle. Even I struggle with thistles.
01:00:10This is a lovely example of how if you do something for butterflies,
01:00:13it helps all kinds of wildlife because I found another caterpillar
01:00:17and it's somewhere on this plant here.
01:00:19And it's a caterpillar of an angle-shades moth.
01:00:22I did a little picture of it
01:00:24and hopefully someone identified it for me.
01:00:26And it's this wonderful insect
01:00:28and this caterpillar comes out at night and munches away at the thistle
01:00:32and soon it will pupate and become this beautiful, beautiful moth.
01:00:36Patrick's garden is full of low-maintenance plants
01:00:40that we can all easily grow in our own gardens.
01:00:43So, we've got some buddleias here
01:00:46and some slightly smelly gardening gloves.
01:00:49Oh, don't worry, they can't be any worse than mine, I can promise you.
01:00:52And there's a trowel and some spades and here's our buddleias.
01:00:57I'm not averse to a bit of gardening
01:00:59and I'm keen to lend Patrick a hand replenishing his butterfly oasis.
01:01:04So, where do you want me to start?
01:01:07So, I'd just stick one at the back of the lavender,
01:01:10more or less where that spade is will be fine.
01:01:12You can dig up these, these are just little weeds.
01:01:15Don't get stung by the nettle that I've left there for the small tortoise shells.
01:01:19Do you know, my garden is... I've left a lot of nettles for butterflies
01:01:24but blimey, they do spread, don't they?
01:01:26Yeah, yeah, they do.
01:01:27I really love the idea that you can look out in your garden
01:01:29and you can see that you've got nettles and thistles
01:01:32and all sorts of things like that.
01:01:34I'm not a lazy gardener, I'm doing something that's incredibly moral,
01:01:37I'm saving butterflies.
01:01:38Yeah, exactly.
01:01:39So, are you happy for this to go in here?
01:01:41Yeah, yeah.
01:01:42Buddleia is by far the most popular nectar plant of British butterflies.
01:01:46A favourite of 18 species, including the Painted Lady,
01:01:50it's not called the butterfly bush for nothing.
01:01:53I just took these from cuttings and I just literally take a cutting of buddleia,
01:01:57stick it in a pot like this, leave it for a few months
01:02:00and then you get a buddleia and you don't have to spend
01:02:02£10 at a garden centre on one.
01:02:05It's really important to think about plants that will keep going
01:02:08right through the year, particularly when there aren't so many other flowers around.
01:02:12That's right, the nectar sources at the end of the summer
01:02:14when everything else has died back, they're there, the real key.
01:02:19Butterflies in the garden are a marker of a healthy ecosystem.
01:02:23Get things right for them, you get things right for other wildlife.
01:02:28The value of caterpillars as a high-protein food source
01:02:31for breeding birds, for example, is invaluable.
01:02:34Butterflies are also effective pollinators.
01:02:38When feeding, pollen sticks to hairs that cover their body
01:02:41and is passed from flower to flower.
01:02:44But they're in decline.
01:02:46Industrial agriculture, habitat loss and changes to the weather
01:02:50have seen their numbers drop by 70% in recent years.
01:02:54Anything we can do for butterflies in our gardens might help buck the trend.
01:02:59The butterfly flower I wanted to show you, Martha, is this.
01:03:03Ivy? Yeah.
01:03:05One of the best things you can have are butterflies in your garden.
01:03:08It flowers really late in the season, doesn't it?
01:03:11Yeah, and that's perfect for the butterflies like the red admiral
01:03:14that need energy late in the summer to hibernate through the winter.
01:03:17And the other thing that's brilliant, this is another great thing
01:03:19for the lazy gardener, isn't it?
01:03:21I guess it is, yeah.
01:03:24All around, Patrick's garden is a one-stop butterfly buffet.
01:03:28So this is garlic mustard or jack-by-the-hedge.
01:03:32This is a weed you'll see under almost any hedgerow
01:03:35and it's a food plant for the orange tip.
01:03:37If it has butterflies on it, then it becomes a really beautiful thing.
01:03:42Yeah, and it becomes a precious thing and you start thinking,
01:03:45well, I'd better not cut that back because there might be a butterfly egg on it,
01:03:49you know, and it does start making you think.
01:03:54MUSIC
01:03:59With the UK now basking in summer sunshine,
01:04:03conditions are perfect for painted ladies.
01:04:06And after such a long wait, they've finally made it here.
01:04:12MUSIC
01:04:19They will be hungry, and with flowers up and down the country in full bloom,
01:04:24painted ladies made it just in time.
01:04:30It took a while, but in late June, early July,
01:04:33the class of 2016 eventually hit our shores in significant numbers.
01:04:41MUSIC
01:04:47Around the country, our spotters are on a winning streak.
01:04:51Marie and David Law found their painted lady on the busy streets of Skageness.
01:04:57It's in the right way round.
01:04:59Oh, yeah.
01:05:03We have two today. Two painted ladies.
01:05:07Tell me facts about painted lady butterflies.
01:05:10Fly from Morocco.
01:05:12Well done. Yeah, yeah.
01:05:14To here, some of them.
01:05:16OK, they fly from Morocco.
01:05:18Yeah.
01:05:19Through Spain.
01:05:21Yeah.
01:05:22Through to France.
01:05:23Sometimes, yeah.
01:05:24Then here.
01:05:25Yeah.
01:05:26Or they can fly straight from Morocco to here.
01:05:29Yeah.
01:05:30Come to me, butterfly. Land on my hand.
01:05:33Wouldn't that be nice?
01:05:34It would.
01:05:35Marie and David have a knack for being in the right place
01:05:38at the right time for painted ladies.
01:05:41Oh, no, there's one up there.
01:05:43Oh, no, there's one there.
01:05:45Yeah, there is.
01:05:46Very top.
01:05:48Right there.
01:05:50Oh, another one.
01:05:52Painted lady butterfly, definitely.
01:05:54It's definitely painted lady, yeah.
01:05:56It's definitely painted lady.
01:05:57It's not a cabbage white.
01:05:58No.
01:05:59Go on, run off and see if it's a brown one.
01:06:01No, it's not.
01:06:03It's speckled wood.
01:06:05Speckled wood, yeah?
01:06:06That was speckled wood.
01:06:07Last year, they witnessed something
01:06:09even the most experienced butterfly scientists
01:06:12would be lucky to see.
01:06:14We're at Skegness, Gibraltar Point Nature Reserve.
01:06:16Yeah.
01:06:17We're here at the top.
01:06:19We are here because in June,
01:06:23we saw two painted lady butterflies
01:06:26that was just about to mate.
01:06:28It was one of those moments where you just happen to walk about
01:06:31and you just notice, you just notice that one little thing
01:06:33that's different.
01:06:35Just that one, they're acting a bit unusual.
01:06:37That's not normally what butterflies do.
01:06:39And then you take a closer look.
01:06:41Oh, there's two of them.
01:06:42Oh, there's two of them here.
01:06:43They could be just about to mate.
01:06:45They were very close though.
01:06:47He was getting closer and closer and closer to her
01:06:50and then they just flew off.
01:06:55They both landed together, got some shots.
01:06:57Both flew off and back to exactly the same spot.
01:06:59They did.
01:07:00Which means it was probably the male's territory.
01:07:02It was down here.
01:07:05Back at Rothamsted, butterfly migration specialist Rebecca Nesbitt
01:07:10has worked with an incredible piece of kit
01:07:12that can help us understand what painted ladies get up to
01:07:16now that they're here.
01:07:18To do this, she tracks painted lady flight patterns using radar
01:07:23and is going to show James how to do it.
01:07:26Hi, Rebecca.
01:07:27Hello.
01:07:28So tell me, how on earth do you put a radio antenna
01:07:31onto the back of a butterfly?
01:07:34So first, we have to trap it down.
01:07:39As with the flight simulator experiment,
01:07:41you have to shave a painted lady before attaching anything to it.
01:07:45Rebecca showed me earlier, so now it's my turn.
01:07:49Here's your butterfly.
01:07:50Yeah.
01:07:51Oh, no.
01:07:52Is that OK?
01:07:53Oh, no.
01:07:54Come back.
01:07:55Give it a go.
01:07:56Got it, got it.
01:07:57What a lively butterfly.
01:07:58Now, you can do this.
01:07:59Behave.
01:08:01There we go.
01:08:02Oh, no.
01:08:03This is embarrassing.
01:08:04I've made such a mess of it.
01:08:06Yes!
01:08:07Yes, I've done it.
01:08:08I handle insects all the time,
01:08:10but I don't know why my hands are completely shaking.
01:08:12So now, I think because you did it so professionally,
01:08:14I'm so nervous about doing this badly.
01:08:17If you think about it too much, your hands definitely start shaking.
01:08:20OK, brilliant.
01:08:22A gentle rub, and my first butterfly haircut is done.
01:08:27Once glued on, this tiny radio antenna weighs almost nothing.
01:08:31What it lacks in size, it makes up for with what it can do.
01:08:36This technology is the creation of Dr. Jason Lim,
01:08:39one of the world's leading experts in insect tracking devices.
01:08:43Called a harmonic radar,
01:08:45it is able to pick up the antenna attached to the painted lady's back
01:08:49using a specific wavelength.
01:08:52It's then able to track the painted lady as it flies.
01:08:55So does it come off eventually?
01:08:57It will just fall off after a few days.
01:09:03This may look heavy, but it's extremely lightweight and harmless,
01:09:07and doesn't affect the painted lady's ability to fly.
01:09:14Butterflies require energy to fly,
01:09:16so topping my one up beforehand is a good idea.
01:09:21Unravelling the proboscis takes not only skill,
01:09:24but also a willing participant.
01:09:29The proboscis is a long, narrow tube, a feeding straw,
01:09:32designed to get deep into nectar-rich flowers.
01:09:37In this instance, sugar water on a cloth will do.
01:09:42It takes a while, but we do eventually get the butterfly to eat something.
01:09:48Having had its pre-flight meal, my butterfly is now ready for take-off.
01:09:55MUSIC
01:10:06We're heading out to that release box. Yeah.
01:10:09And then, if it's OK, if you could just whip the string off...
01:10:12OK. ..and that lets the butterfly go free.
01:10:15Conditions are good.
01:10:17Absolutely perfect, particularly when the sun comes out.
01:10:20Well, this one seems OK, perfectly happy, looks quite calm.
01:10:23You put the pot right down on the floor,
01:10:25tip the butterfly out, and then I will close it.
01:10:27Gosh, she's really active now, isn't she?
01:10:29Yes, that heat has instantly brought her out.
01:10:33As the sun comes out, so do a painted lady's wings.
01:10:37Acting like solar panels,
01:10:39they absorb sunlight to warm up flight muscles, ready for action.
01:10:45With my butterfly poised and Jason Lim's tracking radar
01:10:48spinning into action, we're ready.
01:10:53OK, you can release the butterfly now. Over.
01:10:57Excellent. OK, he's ready. He's ready. Great. He's ready.
01:11:00OK, stand back. Stand back.
01:11:02Just so we don't shade it. OK, and the sun is out.
01:11:05How perfect is this? Quick.
01:11:07And I just pull? Pull. Yeah, pull.
01:11:12I obviously peaked too early.
01:11:14Taking this chance to sunbathe while I can,
01:11:17my painted lady needs a little encouragement.
01:11:21Fly. Come on.
01:11:23The sun is out. Oh, it's going away again.
01:11:26Fly. Come on.
01:11:29And then she's off.
01:11:31Jason, the butterfly is on the move.
01:11:34OK. Over.
01:11:36Butterfly is moving quite fast.
01:11:39Now it's flying towards the manor garden. Over.
01:11:46My painted lady stops for a refuel.
01:11:49Back in the van, Jason tracks it as it moves around Rothamsted.
01:11:53The radar can keep tabs on it for up to a kilometre away.
01:11:57So, where's our butterfly?
01:11:59That is the butterfly flying from here, so it's moving slowly.
01:12:03Yes. Excellent.
01:12:05This is a 100-metre wing,
01:12:07so we know the butterfly is about 100 metres away from us.
01:12:11Away from us right now. Yeah, so here is our release point.
01:12:14So we can see the butterfly flown about 50 metres away from that.
01:12:18So it's on the move then, clearly.
01:12:20That's brilliant that we're able to see this. It's stopped now, though.
01:12:23Yeah, it's stopped now, so we just have to wait.
01:12:25Maybe it's just following below the radar, under the radar,
01:12:29where the radar couldn't pick up the signal from there.
01:12:32The machine allows us to track the position of the butterflies every three seconds.
01:12:37So the butterfly could do what they normally do,
01:12:41sunbathing to warm up the body,
01:12:43and then they'll forage, flying around different patches of flowers
01:12:47and potentially looking for mates as well.
01:12:51What a great piece of technology this is,
01:12:53allowing us to see into the life of a Painted Lady butterfly.
01:12:56And who knows what the future might hold for this.
01:12:59It might even allow us to unlock even more secrets
01:13:02of the Painted Lady butterfly migration.
01:13:05Tracking technology will no doubt advance,
01:13:08and so too the distances that can be covered.
01:13:11You never know, one day we might be able to track a Painted Lady
01:13:14all the way from Morocco to here.
01:13:25Our butterfly spotters don't need tracking devices.
01:13:29Now that it's July, Painted Ladies are coming to them.
01:13:32Dave Cook is back from Crete and out doing what he loves best.
01:13:38I've come here to the location of the Ditchley Common
01:13:41with the specific intention of finding the Painted Lady
01:13:44that I found here this morning.
01:13:48She's still here, and she's still nectaring.
01:13:52That's great. That's absolutely brilliant.
01:13:58Result.
01:14:01That's what it's all about.
01:14:04And Darcia from Wiltshire is equally pleased to be out and about
01:14:08spotting her favourite butterfly.
01:14:11I'm Darcia Gingell, and this is Morgansill Nature Reserve,
01:14:14which is a Wiltshire Wildlife Trust site in North Wiltshire.
01:14:17And it's a gorgeous morning this morning,
01:14:20and we're here to hopefully try and find some Painted Ladies.
01:14:25It's actually quite difficult to get hold of a picture of a Painted Lady
01:14:28unless they're actually still and nectaring,
01:14:31because a lot of the time they're quite fast flyers.
01:14:34So they'll zoom into view, maybe come around you,
01:14:37circle around you, take a look at you, and then they're off.
01:14:40Unless you find them, as I said, nectaring,
01:14:43and once they're in one place, maybe on an ice thistle,
01:14:46they tend to stay there, and you might get a chance
01:14:49to take a glimpse of one for a few seconds,
01:14:52and they're off again.
01:14:54Quite a big butterfly there, isn't it?
01:14:56It's in your torch there.
01:14:58Got my hopes up.
01:15:00There we go. Me and my partner were at a place called Raven's Roostwood.
01:15:03We're just walking along the track.
01:15:06Next minute, whizz, round your head.
01:15:09Really, really shocked and surprised to actually see it was a Painted Lady.
01:15:12Just come and landed and settled on the floor in front of us.
01:15:15Here's the beautiful butterfly.
01:15:18There we go.
01:15:21It's just flown along behind us and come and landed and settled.
01:15:24I think it's quite fascinating to think
01:15:27where this beautiful butterfly has come from.
01:15:30I think it's almost magical when you actually see one,
01:15:33and I think it reminds you of those fairy tales when you're a child
01:15:36and you're imagining what a fairy really would be like.
01:15:39I think the butterflies are the closest you can get to that.
01:15:43With Painted Ladies now being seen all over the country,
01:15:46how do we know just how successful the migration has been this year overall?
01:15:50Richard Fox is part of Butterfly Conservation,
01:15:53a definitive authority on British butterflies.
01:15:56His migratory maps tell a fascinating story.
01:15:59He's been a pioneer in the conservation of butterflies
01:16:02since the early 1900s.
01:16:05He's been a pioneer in the conservation of butterflies
01:16:08since the early 1900s.
01:16:11He's been a pioneer in the conservation of butterflies
01:16:14since the early 1900s.
01:16:16We've got some maps here of sightings of Painted Ladies from this year.
01:16:20We've got some maps here of sightings of Painted Ladies from this year.
01:16:24Each Painted Lady picture represents a place
01:16:27where members of the public have reported seeing Painted Ladies.
01:16:30This is from... It was January and February.
01:16:33I'm amazed there are any Painted Ladies at all.
01:16:36You often wouldn't see any Painted Ladies in Britain at all
01:16:39over that January, February period in a normal year.
01:16:43But this year wasn't normal.
01:16:44We had a very, very mild spell over New Year
01:16:47and winds from the South bringing Painted Ladies
01:16:50from North Africa, where they normally are
01:16:52at that time of year,
01:16:53these pioneering Painted Ladies coming up
01:16:55into South West England, South Wales.
01:16:57But not just the South.
01:16:58I mean, there's the Isle of Man, Northern Ireland.
01:17:01Yes, and Cumbria as well.
01:17:02So really, yeah, amazing influx at that time of year.
01:17:07Painted Ladies normally start arriving here in May,
01:17:10but a very warm January meant one bucked the trend.
01:17:16They react very quickly to conditions around them.
01:17:20Tropical air blowing in from Africa
01:17:22saw Britain bask in unseasonably warm weather
01:17:25at the beginning of the year.
01:17:27With the warm winds came the first Painted Lady sighting
01:17:30in Somerset in South West England
01:17:33as early as January the 3rd this year.
01:17:37It had flown the 2,500 kilometres
01:17:40from where I was in Morocco to here in a matter of days.
01:17:45But that's not the earliest on record.
01:17:48Remarkably, one was spotted on New Year's Day in 2013.
01:17:53Painted Ladies that fly here early
01:17:55in a single journey are known as pioneers.
01:17:59Unfortunately, these pioneers will perish
01:18:02once the weather turns cold again.
01:18:07And then we come on to the spring, a few more.
01:18:11Yes, there are a few more,
01:18:13but the weather really wasn't very good this spring.
01:18:16It was colder than usual, it was very wet in some places.
01:18:19So although we're seeing more butterflies, as you'd expect,
01:18:22there's nothing very much going on.
01:18:24So we move on to the next ones, the summer.
01:18:28And what a summer, albeit delayed.
01:18:31In late June through July,
01:18:34sightings erupted across the country.
01:18:37So these are Painted Ladies
01:18:39not coming direct from North Africa,
01:18:41but coming up from Spain, Portugal, Southern France.
01:18:44It's an explosion of Painted Ladies.
01:18:46I mean, there's barely a part of the country
01:18:48that doesn't have Painted Ladies.
01:18:49No, that's right.
01:18:50And indeed, even in the places
01:18:51where they haven't been recorded,
01:18:52they may well have been there,
01:18:53just not been spotted by people.
01:18:56These Painted Ladies aren't coming from North Africa
01:18:58as the ones in January and February were.
01:19:00These are moving up from southern parts of Europe,
01:19:03so they're kind of generation on.
01:19:05But really, all over the country, as you can see.
01:19:08Yeah, they're far north of Scotland, out in the Hebrides.
01:19:10Really good concentrations down in the southwest.
01:19:13We had people on the Isles of Scilly and in West Cornwall
01:19:16who saw 50 or even 100 Painted Ladies in a single day.
01:19:20So there were some quite good numbers around in this time.
01:19:23So we hear so much about the kind of problems,
01:19:26the troubles that butterflies are in.
01:19:28What about Painted Ladies?
01:19:30Well, Painted Ladies are very adaptable species.
01:19:33They're obviously highly mobile,
01:19:35they're nomadic, they don't live in particular places.
01:19:37And most importantly, I guess,
01:19:39the food that their caterpillars need
01:19:42is mainly thistles in this country.
01:19:44That's mainly what the caterpillars are eating.
01:19:45And of course, thistles are very common and widespread.
01:19:48So actually, Painted Ladies have done really well
01:19:49in Britain over the past 40 years.
01:19:51Oh, that's really good to hear.
01:19:53To get here, Painted Ladies started out from Morocco
01:19:56in late March, following the appearance
01:19:59of the foods they feed on.
01:20:01They arrived in Spain in April to breed,
01:20:04a new generation carrying out the next stage of the journey
01:20:07through France in May.
01:20:09Few made it to Britain in May,
01:20:11but the Painted Ladies have made it to Britain
01:20:13in late March, following the appearance
01:20:16of the foods they feed on.
01:20:18They arrived in Spain in April to breed,
01:20:21few made it to Britain in May,
01:20:23bad weather delaying their arrival in significant numbers
01:20:26until late June, early July.
01:20:29The Painted Ladies we see now are the grandchildren
01:20:32of ones that left Morocco.
01:20:34Generations born in this country will then continue
01:20:37to push further north towards the Arctic
01:20:40before the summer is out.
01:20:41BIRDS CHIRP
01:20:48Basking in the British sunshine in July,
01:20:51Painted Ladies are a welcome sight.
01:20:53This is what our spotters have been waiting for.
01:20:58Like Dave and Agnes in Dorset, who found a beauty.
01:21:07Come on.
01:21:12Oh, it's very cut, yes.
01:21:16Yeah, but you can see how fresh she is.
01:21:17She's got that metallic glow on her.
01:21:19She's only been out a day, if not this morning.
01:21:23Fantastic.
01:21:31The numbers are definitely starting to build.
01:21:35She's warming up really nicely, isn't she?
01:21:37Yeah.
01:21:38Brilliant.
01:21:39Dave and Agnes are just the tip of the iceberg.
01:21:42Spotters from all over the country
01:21:44are seeing our ladies regularly now,
01:21:47and the pictures are rolling in.
01:21:49People have been sending in all sorts of pictures,
01:21:51not all of them butterflies,
01:21:52but this one is a really good one.
01:21:54And do you know what?
01:21:54This is a guy, he's called Adam Middleton,
01:21:56and guess what?
01:21:57He's only 14 years old.
01:21:58That's so...
01:21:59Because the image is so sharp,
01:22:00you can really see the antennae.
01:22:02It is absolutely brilliant.
01:22:04You can see the eye here, the antennae,
01:22:06and it's got its proboscis out,
01:22:07so it's obviously trying to feed on nectar there.
01:22:10You know, it's really hard to get a picture like this
01:22:12of a butterfly in the wild,
01:22:14and he's 14 years old,
01:22:15so not only is he a fantastic butterfly spotter,
01:22:18he's a pretty good photographer as well.
01:22:20He's a young man who'll be after your job
01:22:22one of these days.
01:22:23Yeah, probably.
01:22:24And it's so important that people do this.
01:22:27You know, scientists are relying on data
01:22:28from people that are doing all of this,
01:22:31taking pictures, sightings,
01:22:33and so that they can record them
01:22:34and see what's happening with the migration
01:22:36from a conservation point of view.
01:22:38And what I really like is the way
01:22:39that people have been doing it in our country
01:22:41for hundreds of years.
01:22:42So we have the best biological data, don't we?
01:22:45That's right, yeah.
01:22:46Because we've lived for so long.
01:22:47We're a nation of butterfly spotters.
01:22:52All the painted ladies our spotters are seeing
01:22:54are this year's Moroccan descendants.
01:22:57When I joined the world's leading painted lady expert,
01:23:00Constanti Stefanescu, earlier in the year,
01:23:03he was piecing together the puzzle
01:23:05of why painted ladies migrate in the first place.
01:23:09It's taken him 10 years of extensive research
01:23:13to establish the facts and reach a definitive conclusion.
01:23:17After countless expeditions to Morocco
01:23:20and painstaking data analysis in Spain,
01:23:24what has he found out?
01:23:29Well, the butterflies are going absolutely crazy in here,
01:23:33and it's rather perfect for us to be able
01:23:36to welcome Dr. Constanti, who it seems a long time ago
01:23:39since we were filming together in Morocco, doesn't it?
01:23:42Yeah, yeah.
01:23:43He's far away at that time, yeah.
01:23:45But they clearly found you as a butterfly fan.
01:23:49Now tell me about your discovery
01:23:51and all the work that you've been doing,
01:23:53which I was happy to be a part of.
01:23:56Well, I started to collect caterpillars
01:24:00of the painted lady to see.
01:24:03We were the natural enemies many years ago,
01:24:06maybe 10 years ago.
01:24:08Immediately, I realized that these wasps
01:24:12can be very, very important.
01:24:14And then I thought that maybe migration could be
01:24:19a way to escape this mortality due to these little wasps.
01:24:25Constanti's research indicates
01:24:27that painted ladies leave Morocco
01:24:30at a specific time of year
01:24:31to escape from their deadly enemy, the Cortesia wasp.
01:24:35If they don't, they die.
01:24:38When I collected the caterpillars in Morocco,
01:24:40I was afraid that maybe the results
01:24:44would not support the idea.
01:24:47But when I brought back these caterpillars to Catalonia,
01:24:51immediately they started to die because of this parasite.
01:24:56So yeah, I'm very happy about that, yeah.
01:24:59So how would you sum up your discovery this year?
01:25:03Well, I would say that the data that we gathered this year
01:25:08is the first clear demonstration
01:25:12that natural enemies is also one of the factors
01:25:17that are important for migration.
01:25:20Still analyzing some data,
01:25:22but the results are very clear.
01:25:24So I'm absolutely confident
01:25:27about what we found.
01:25:31Constanti has cracked it.
01:25:33His 10-year investigation has revealed astonishing new facts
01:25:38about the painted lady migration.
01:25:41Tiny wasps are the painted lady's nemesis in Morocco,
01:25:45laying eggs inside caterpillars
01:25:47and subsequently killing them on a grand scale.
01:25:51As painted ladies breed,
01:25:53so too do the wasps in huge numbers.
01:25:57At some point during the breeding season,
01:25:59painted ladies have to leave Morocco to survive.
01:26:03This is groundbreaking news,
01:26:06a scientific first for Constanti.
01:26:08His dedicated research has paid off
01:26:12and added another reason why painted ladies
01:26:14migrate in the first place.
01:26:17Not only do they move to follow their food source
01:26:20as previously known,
01:26:23but they also migrate because they're driven out.
01:26:28Well, that's great that we're able to break the news
01:26:31of your discovery in our film.
01:26:34You will appear in the acknowledgements of this paper.
01:26:38Oh, well, I never thought I'd end up as a footnote
01:26:41in a scientific paper. That's fantastic.
01:26:47But just as suddenly as they appear, usually in May,
01:26:51painted ladies disappear in late October.
01:26:55For years, it was thought they simply hibernated
01:26:58like many other British butterflies, but they don't.
01:27:01In fact, they don't stop doing anything.
01:27:05Feeding and breeding throughout the year,
01:27:08albeit on different continents, they are always on the move.
01:27:12As Northern Europe gets colder, they seek warmer climes.
01:27:16And where better than where it all began?
01:27:20Morocco.
01:27:21Incredibly, a final generation makes the 2,500-kilometre journey
01:27:27from Britain back to Morocco in just a few days.
01:27:31And it's not just from here.
01:27:33They do so from wherever they've travelled across Europe each year.
01:27:37In six generations, painted ladies move up to 5,000 kilometres
01:27:43in one direction, towards the Arctic Circle,
01:27:46and 5,000 kilometres back to Morocco.
01:27:50In a truly remarkable voyage, they return to Africa
01:27:55to start their life cycle and the extraordinary migration
01:28:00all over again.
01:28:09We've learnt so much about the painted lady,
01:28:12and there could be more of a contrast
01:28:14between the lush green gardens here at Rothensted
01:28:17and those rocky deserts in Morocco.
01:28:19But, you know, I think it's about time that we let these creatures go free.
01:28:24And there's enough food plants around here that they could breed
01:28:27and maybe even send a next generation of butterflies
01:28:31going back all the way to Morocco.
01:28:34Right, I think we should go for it.
01:28:36Set the butterflies free.
01:28:38One, two, three, go.
01:28:40Oh, look, they've been trying to get out all day, I think.
01:28:43Fantastic. There we go.
01:28:46Morocco's that way. Go.
01:28:48Yes.
01:28:49There we go. Oh, look, there we go.
01:28:52Be free.
01:29:18Stay with us here on BBC4.
01:29:21A picture of Victorian domestic bliss.
01:29:24Jeremy Paxman explores the era through art,
01:29:28starting with the Royal Family's paintings at Osborne House.
01:29:32Next.
01:29:48.