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00:30There's an insect in this garden that all gardeners loathe, aphids.
00:47They've made enemies of gardeners, but in the undergrowth they have friends, ants.
00:59Ants herd aphids to the best possible feeding places, just as human shepherds will herd
01:05their sheep to the best pastures.
01:08And just as shepherds protect their flocks against wolves, so ants protect the aphids
01:13against their insect enemies.
01:18Ladybirds are among the most dangerous.
01:20They after all eat aphids, so the ants must get rid of them.
01:25That's not easy.
01:26It's quite hard to get a grip on the polished shell of a ladybird.
01:35But eventually, success.
01:39Aphids excrete a liquid that ants relish, honeydew.
01:43That's why ants protect them.
01:45Such close relationships are frequent among insects, perhaps because they've had so long
01:49to develop them.
01:51They appeared on land, after all, about 100 million years before any backbone animal.
01:57And they can also evolve much faster, because they can produce several generations within
02:02a single year.
02:03So perhaps it's not surprising that they have developed relationships between one another
02:09of a complexity that blows the mind.
02:22These associations extend not only to other insects, but to plants.
02:27They were established at a very early period.
02:30Plants are the basis of all life, for only they can combine minerals in the ground with
02:35gases from the air and produce something worth eating.
02:39Insects, however, not only eat them, they also exploit them in much more devious ways.
02:52Tropical rainforests are famous for being thick, tangled masses of vegetation.
03:01But in this one in Peru, there are mysterious clearings where only one or at most two kinds
03:10of trees will grow.
03:12The local people call such places as this devil's gardens and believe that spirits
03:19kill other kinds of trees.
03:22And the real killers of those trees, well, they've only just been discovered.
03:29The leaves of the surviving trees all have these swellings on their stems, and going
03:36in and out are armies of tiny, tiny ants.
03:42The swellings are their homes, specially developed for them by the tree.
03:48And in them, safe from predators, the ants keep their eggs and larvae.
03:52They even keep domestic livestock, white scale insects, which, like aphids, supply the ants
03:58with drinks of honeydew.
04:03Producing this accommodation also benefits the tree, for the ants provide their landlord
04:08with a valuable service.
04:10They guard it against its enemies.
04:16All kinds of insects will eat a plant's leaves, given the chance.
04:21But they don't get a chance, not on this tree.
04:28So the caterpillar goes elsewhere.
04:33This is a more formidable leaf muncher, a kind of giant grasshopper, several thousand
04:39times bigger than any individual ant.
04:44That is not so easy to shift.
04:50But it does have a weak spot.
04:53If you can say that any insect has a heel, then this one has an Achilles heel.
05:03And the ants seem to know it.
05:14Enough is enough.
05:19The ants not only repel their host's animal enemies, they also, perhaps more remarkably,
05:25keep competing plants at bay.
05:28A squad of them leaves the barracks and sets out on one of their regular patrols of the
05:33neighbourhood.
05:39They found a newly sprouted sapling.
05:42Perhaps it's grown from one of their landlord's seeds, in which case all well and good.
05:48But this one hasn't.
05:50It's an intruder.
05:52They go into action, biting its stems.
05:59Reinforcements arise.
06:02Hundreds of tiny jaws cut into its stems.
06:06The sapling begins to wilt.
06:23But bites alone are not enough for the ants to achieve their ends.
06:28They lift their abdomens and inject formic acid into the crippled plant's wounds.
06:39The poison spreads through the plant's tissues, hastening its death.
06:45And within a few days of being comprehensively stung, all these plants are dead.
06:52And the ants, or the devils, have extended their garden still further.
07:00But the benefit of this drastic gardening, of course, is not restricted to the plants.
07:05The ants also profit.
07:08They have ensured that their plant landlord can extend its territory without competition.
07:13And that provides them with more homes.
07:16So they too can increase their numbers.
07:29It's one thing to provide food and shelter in return.
07:34It's one thing to provide food and shelter in return for protection.
07:39But it's quite another thing to be compelled to provide a home where before there was none.
07:45But some insects have the ability to force a plant to do just that.
07:50They're called gall-makers.
07:52And this oak tree is infested with them.
07:56This odd, wrinkled object at the base of an acorn is known as a nopper gall.
08:03Inside, there's the tiny grub of a minute wasp.
08:08To understand how it got there, we have to go back to last spring.
08:19This tiny insect, scarcely bigger than a mosquito, is one of these gall wasps.
08:25There are lots of them flying around the oak flowers.
08:32Most of the flowers by now have been pollinated and are about to develop into acorns.
08:38The gall wasps too have mated, and this female is looking for a place to lay her eggs.
08:46She thrusts her ovipositor into the base of the fertilised flower and injects an egg.
08:53And that triggers a profound genetic change in the growing oak bud.
09:00It develops not into an acorn, but into something very different.
09:04A gall.
09:08Within, the tiny larva whose secretions have caused the change feeds on the oak tree's tissues.
09:15As summer proceeds, the galls become increasingly hard and woody.
09:23Autumn comes, and the oak tree starts to shed its leaves.
09:27It's shutting down for the winter.
09:29And with its leaves go both acorns and galls.
09:34Plant and insect life is suspended.
09:40But other insects are still there.
09:45The gall wasp is a very special species.
09:48It's the only one of its kind in the world.
09:53It's a very special species.
09:55It's a very special species.
09:57It's a very special species.
09:59Spring is suspended.
10:03But unseen changes are nevertheless taking place.
10:10Spring comes at last.
10:20Inside the gall, something starts moving.
10:25The larva has turned into an adult wasp.
10:30It has spent nine months within the oak tree's tissues.
10:34It has only a few weeks of its life left.
10:44Now, as an adult, it must look for another oak to inject with eggs.
11:00A single oak tree may be afflicted by 70 different kinds of gall,
11:04each produced by a different species of wasp
11:07and each with its own particular contorted shape.
11:15These hard shells may seem to be effective defences
11:18for the little grub inside them, but not necessarily so.
11:25This is another kind of gall wasp,
11:27and she's not a genetic engineer, she's a burglar.
11:31Behind her, she trails her equipment for breaking and entering, a drill.
11:36She carefully selects a site for her operations and takes aim.
11:44She flits away the drill's sheath and starts work.
11:49Her aim has to be very accurate if she's to strike her target,
11:53the larva at the gall's centre.
11:57The tip of her drill has a sharp cutting edge of metallic zinc
12:01which pierces the gall tissues with ease.
12:05When she detects that she's reached the central chamber,
12:08a microscopic egg travels down the centre of the drill and into the larva.
12:16The operation is over.
12:18Her offspring will now hatch in the gall's centre,
12:21consume the flesh of the resident larva and take over the gall.
12:28Galls are worldwide.
12:30California, for example, has other species of oak tree and other kinds of gall.
12:38These particular ones are relatively tiny, the size of peppercorns.
12:42You'd hardly notice them, except for one thing.
12:46They jump.
12:48And not only do they jump, they jump for three days.
12:52The tiny larvae within flip themselves about inside their minute chambers.
12:57Why they should do so is not clear.
12:59Perhaps it's a way of moving their homes into cracks and crevices
13:03where they're out of the reach of predators and parasites
13:06and shaded from the hot Californian sun.
13:10Another gall in Hungary protects itself in a more complex fashion.
13:15It recruits insect guardians.
13:18This gall is producing nectar.
13:24It's sweet.
13:26And it's producing it not for the benefit of the oak tree,
13:30but for the benefit of the tiny grub that lies within the gall.
13:35Because the nectar attracts ants.
13:38And ants serve as defenders against predators.
13:43And if you want to see how valuable they are, let me remove some.
13:52Within a few minutes, a different kind of gall wasp appears.
13:56It's another of those burglars,
13:58looking for an existing gall into which it can inject its egg.
14:03But the ants have now returned,
14:05and the gall wasp is no longer a threat.
14:09Away it goes.
14:12The ants, having driven off the wasp,
14:15take their reward of nectar.
14:21In the normal course of events, oak trees don't produce nectar,
14:25but many plants certainly do.
14:27It's a way of attracting predators.
14:30It's a way of attracting predators.
14:33And the colourful flowers are advertisements
14:36proclaiming that nectar is there for the taking.
14:44But the plants must also ensure
14:46that visiting insects collect the pollen, as well as nectar.
14:50And that leads to all kinds of complexities.
14:55The plants must also ensure
14:57that visiting insects collect the pollen, as well as nectar.
15:01And that leads to all kinds of complexities.
15:08Like many plants, the pyramidal orchid
15:11has a way of ensuring that they do.
15:14A burnet moth probes into the orchid's nectar store,
15:18and as it does so, a horseshoe-shaped mass of pollen
15:21clips onto its long proboscis.
15:26Inconvenient it may be, but the moth can't shift it.
15:32Away it goes to another flower, taking the pollen with it.
15:37And this time, as it probes for a drink,
15:40a speck of pollen is transferred to the female part of the flower.
15:47The job is done.
15:51The traffic of insect pollinators to and from flowers
15:55is so heavy and, in particular, so predictable
15:58that it's not surprising
16:00that some invertebrates have learned to exploit it.
16:04A white crab spider sits almost invisible on a white flower,
16:09waiting in ambush.
16:12And it catches a bee.
16:19The spider is clearly taking advantage of the flower's advertising.
16:24It looks superbly camouflaged to our eyes,
16:27but insect eyes are different to ours
16:29and see parts of the light spectrum invisible to us.
16:33Under ultraviolet light,
16:35we can get a better idea of how they see things.
16:38And most surprisingly,
16:39the spider looks more obvious to them than it does to us.
16:43Why should that be?
16:45Perhaps it's because ultraviolet markings on some flowers
16:49serve to guide insects to nectar.
16:52So maybe the spider's colour
16:54is a positive attraction for bees.
17:00Certainly, honeybees seem more likely to visit flowers
17:03with crab spiders on them than those without,
17:06often with fatal consequences.
17:15The relationships between the animals that live in the undergrowth
17:18are full of such deceits and impostures.
17:21Here in Australia, there's an intriguing example
17:24that has only just been discovered.
17:27This...
17:31..is a feather-legged bug.
17:36It too manages to persuade prey to come close.
17:40But its invitations are aimed not at bees, but ants.
17:44And what the ants get is a very nasty surprise.
17:51Like all members of the bug family,
17:54this one has a long tube for a mouth.
17:57Most stick it into plants to suck sap.
18:01Using it to eat an ant is more difficult.
18:05The bug starts by waving to passing ants.
18:09The feathery flanges on its legs are so large
18:12they can be seen from quite a distance.
18:16The ants are visibly intrigued,
18:19but they're not yet close enough for the bug to attack,
18:22so it reinforces its gestures by producing a chemical perfume
18:27that the ants find irresistible.
18:30They come closer still.
18:35They climb all over the bug,
18:37trying to find the source of this strange compulsive smell.
18:41And the bug does nothing to stop them.
18:54Where does that smell come from?
18:57Is it on the bug's legs?
19:12The bug now answers the ants' questions.
19:16It lifts itself up and reveals a gland on its underside.
19:20That's what's producing the smell.
19:26The ant presses its head against the bug's chest
19:29to actually taste the gland.
19:31It's the perfect position for its own execution.
19:36The bug stabs its mouth into the back of the ant's head.
19:45So a tube can be used to suck nourishment from an insect
19:49as well as from a plant.
19:52This is the rogue of the bug family, a killer.
19:57Ants are among the most numerous, widespread
20:00and frequently exploited members of the undergrowth.
20:04These, in Australia, collect seeds and store them underground.
20:09Plants encourage them to do so
20:12by adding a tasty capsule to their seeds.
20:15That may seem odd,
20:17but these ants don't eat all the seeds they store.
20:20In fact, they only eat a few.
20:23These ants don't eat all the seeds they store.
20:26In fact, seeds are more likely to germinate below ground than above.
20:31But not everything on this forest floor is what it seems.
20:36When it comes to putting your eggs in a suitable place,
20:41some insects persuade other insects to do the job for them.
20:46This little object looks like a seed
20:49and certainly it's fallen from above
20:52and that ant seems to think it's worth eating.
20:55But actually, it hasn't come from a plant.
20:58It's come from another insect.
21:03And this is it.
21:05It's rather difficult to see
21:07because it looks exactly like a dry leaf,
21:10but it's a stick insect.
21:12There's its head, antennae,
21:15and that's the tip of its abdomen.
21:19As an adult like this, it spends all its time up in the trees eating leaves.
21:24And when the time comes to lay, and this one is doing so,
21:28all she does is simply to flick away the egg
21:32and let it fall to the ground.
21:34But that's not quite as risky as you might think.
21:41Whenever you are, you can be pretty sure
21:44that some ants will turn up looking for food.
21:47And that is exactly what the stick insect's eggs look like,
21:50a nutritious seed complete with that fatty capsule at the tip.
21:56So the ants start to haul them away.
22:00CHIRPING
22:16Although the ants certainly eat a great number of the seeds they store,
22:20stick insect eggs don't seem to be quite as tempting.
22:23At any rate, the ants, after all their labour,
22:26usually leave their stick insect eggs untouched.
22:34While the seasons pass, the eggs lie underground,
22:37hidden from birds and any other predators that might eat them.
22:40They may remain there, safe, for up to three years,
22:44but eventually they hatch.
22:52It's only at this early stage of its life
22:55that a stick insect actually runs.
23:00The youngsters positively scamper up into the tree branches.
23:10There they will take up their adult life of leisure,
23:13well camouflaged, stolidly chewing leaves.
23:18Giving your offspring a good start in life can take a lot of effort,
23:22so some insects have evolved highly complex strategies
23:26to induce other species to become nursemaids on their behalf.
23:33This Californian desert hardly seems to be the best place to find nursemaids,
23:38but blister beetles have an amazing way of discovering them.
23:46It starts, simply enough, with the female beetle.
23:49She has dug a hole and is now laying her eggs in it.
23:57That done, she abandons them.
24:03A few centimetres below the surface of the sand conditions are good for eggs.
24:07Not too cold, neither too hot, even in the heat of the day.
24:14Six weeks later, they hatch.
24:18But these sands are very barren and scorching hot.
24:21Somehow, the tiny larvae have got to find food,
24:24and they won't find it here.
24:30Their survival depends on teamwork.
24:37Together, as a closely coordinated group,
24:40they climb up a stem of withered grass.
24:48When they get to the top, there's nowhere else to go.
24:52They look dangerously exposed to the sun and to other predators,
24:56but there they stay, in a tight, squirming mass.
25:04For those that can get there, the top of this stem
25:07has become a stage for a remarkable piece of deception.
25:11What they've discovered is that,
25:13What these larvae want is a lift, a ride,
25:16and they want it so badly
25:18that sometimes they'll even try and get it from a human finger.
25:23But what they're really searching for is not a human finger.
25:27They're searching for another insect.
25:31Here it comes, a female digger bee,
25:34leaving a tunnel that she's just dug for her own young.
25:38She's off to gather pollen.
25:47She packs it into baskets on her back legs
25:50and takes it back to her burrow.
25:54It'll provide valuable food for her young when they eventually hatch.
26:00And here comes a male.
26:02He's on the lookout for a female.
26:09To him, the cluster not only looks like a female,
26:13it smells like a female,
26:15for the beetle larvae are producing a perfume, a pheromone,
26:18that is exactly like that emitted by a female bee.
26:22He alights in order to mate,
26:24and in seconds is covered by the larvae that swarm all over him.
26:31At first, he seems stunned by the shock of his sudden increase in weight.
26:37But then he's off again.
26:41Now, his luck improves.
26:43This really is a male bee.
26:45But then he's off again.
26:49Now, his luck improves.
26:51This really is a female.
26:55And while he mates, his passengers jump ship.
27:16Now they're all on board a female bee.
27:27She, having mated, goes back to her nest to lay,
27:31taking the larvae with her.
27:36At last, the young beetle larvae have reached safety,
27:40and food, the sort of pollen
27:42that the female digger bee worked so hard to collect for her own young.
27:47So they hop off and tuck in.
27:56Not only do they consume the pollen,
27:58when that runs out, they will eat the young bee larvae too.
28:05Blister beetles are not alone in using couriers
28:08to take their offspring to food.
28:12The young of this botfly, here in Brazil,
28:15feed on the blood and tissues of living cows.
28:18But how is a female to get them there?
28:21She is a big insect, so big that cows would notice if she landed on them
28:26and would probably flick her off.
28:28She needs a lightweight courier.
28:32A housefly, a fraction of her weight.
28:35That would do nicely.
28:38She drops down to stalk it.
28:43She's got it.
28:45She manipulates the housefly into the right position.
28:49And now, one by one,
28:51she glues her eggs onto the housefly's abdomen.
28:59Within a few seconds,
29:01the housefly has been coated by about 30 cream-coloured eggs.
29:07The botfly is ready.
29:10The botfly releases its hapless messenger.
29:15The housefly seems well aware that it's carrying an extra load,
29:19but it can't get rid of it.
29:30So it goes back to its normal business,
29:33which includes visiting cows to drink their sweat.
29:40A small fly, unlike the lumbering botfly,
29:43is no real irritation and is able to feed largely unhindered.
29:53The fly mops up the sweat with its pad-shaped mouthparts.
29:57But as it feeds,
29:59so the warmth of the cow's body causes the botfly's eggs to hatch.
30:10The larvae are armed with tiny hooks,
30:14which help them to get a grip on a cow's skin and bore into it.
30:24So, in a few minutes,
30:26a cow can acquire a dozen botfly larvae,
30:29feeding away beneath its skin.
30:32Licking won't get rid of them now.
30:36A couple of months later,
30:38the full-grown larvae emerge and drop to the ground.
30:43There, they will burrow into the soil, pupate and turn into adults.
30:51All kinds of creatures, great and small,
30:54are exploited by insect parents in this kind of way.
30:58This is Costa Rica,
31:00and here lives a species of orchard spider.
31:03They construct horizontal orb webs,
31:06as lovely as those made by any spider.
31:10But one individual has a hanger-on.
31:14An anonymous-looking grub is clinging to her abdomen.
31:24She seems little affected by having a passenger,
31:27and every day, as usual,
31:29and every day, as usual,
31:31she builds a new and perfect web.
31:36She is just as efficient a hunter as ever,
31:39but every catch she makes,
31:41she shares, in effect, with her passenger,
31:44for the grub is sucking her juices.
32:00Her passenger stays with her for some two weeks,
32:03slowly growing in size at her expense.
32:08And still, daily, she constructs a new web.
32:14Then, one evening, when, as usual, she starts to spin,
32:17something seems to have gone dramatically wrong.
32:21She seems incapable of making her normal, beautiful orb.
32:25What she produces has no shape,
32:27no radiating spokes, no sticky spiral.
32:30It's just an untidy tangle.
32:33The grub is responsible.
32:36It has injected her with a hormone
32:38that has spread to her brain and deranged her.
32:42She has only an hour or so to live.
32:45This is her last act.
32:48Small claspers inflate on the grub's back.
32:51With these, it grasps the wreckage of the web
32:54so that it will not fall as the dying spider loses her grip.
33:02It sucks the remaining fluid from the spider's body.
33:07Slowly, the liquid is withdrawn.
33:15Even the spider's legs are emptied
33:18until the corpse is no more than a husk.
33:24The grub has no further use for her.
33:27And now the grub, clinging to the spider's last tangled web,
33:31starts to spin for itself.
33:41It needs a shelter in which to reorganise its body.
33:45A place where it can breathe.
33:48A place where it can breathe.
33:51A place where it can breathe.
33:54In which to reorganise its body.
33:57A cocoon.
34:02Inside the lacy walls, its body is breaking down,
34:06for it has to be reassembled in a very different form.
34:15At last, the killer is about to reveal its true identity.
34:25It's a wasp.
34:28Now it must fly off to find a mate
34:31so that another wasp egg may be attached to another orchid spider.
34:46The opportunity to find creatures to parasitise
34:49is a rare opportunity.
34:52The opportunities to find creatures to parasitise
34:55in the undergrowth seem almost endless.
34:58And yet, surprisingly, there are some parasitic wasps
35:01that find their victims in water,
35:04in lakes and ponds like this one.
35:07They're extremely small, about a quarter of a millimetre long.
35:11In fact, one of the smallest of all insects.
35:14And I've got some in this test tube.
35:17And to give you an idea of just how small they are,
35:20you can in, alongside them, give a sense of scale.
35:25Yet these tiny specks have eyes, legs, feelers,
35:29just like any other insect.
35:40They're known as fairy wasps
35:42and spend nearly all their lives underwater.
35:46They make a tiny water flea,
35:48if only of the size of a grain of sand, look like a giant.
35:52They're so minute,
35:54they can lay their eggs inside the eggs of other insects,
35:58and they choose those laid by water beetles.
36:04Water beetles lay their eggs inside plant stems.
36:09A female fairy wasp, having located one,
36:13uses its microscopically thin ovipositor
36:16to inject up to 100 or so eggs into just one of the beetles.
36:29And here they hatch.
36:35The young wasps feed and grow,
36:38consuming the water beetle's undeveloped young.
36:43Not only that, they mate here.
36:55Then, at last, they leave the shell of the beetle's egg.
37:12The females must now lay,
37:14and some will be able to do so in other ponds,
37:17because, in spite of everything, they still have wings.
37:24Other, bigger parasitic wasps have totally lost their wings.
37:29You can find them on many a British heath.
37:32This one, methotra, looks rather like an ant,
37:36and insects that live by hunting ants easily mistake it for one.
37:41The tiger beetle is a very active ant hunter.
37:45It chases them and runs them down.
37:56And very successful it is.
38:01Earlier in its life, of course, as a larva,
38:04a tiger beetle can't run around.
38:07Instead, the larva catches ants by waiting in ambush.
38:12It plugs the entrance to its burrow with its armoured, plate-like head.
38:17If an ant touches that, it's as good as dead.
38:32It works every time.
38:38Methotra, however, is a more awkward customer.
38:51The beetle larva is waiting with jaws agape.
39:01But methotra is not afraid of ants.
39:05But methotra is more agile than the usual ant,
39:09and it manages to slip out between the beetle larva's jaws.
39:16It grabs the larva's soft body and pulls.
39:26And now it stings it.
39:30Methotra climbs out of the tunnel, waiting for the poison to take effect.
39:41The sting has only paralysed the larva,
39:44and the wasp drags the helpless creature farther down its burrow.
39:50Now she lays her egg onto it.
40:00To prevent anything interfering with her grub while it stays underground,
40:04feeding on the paralysed beetle larva, she blocks out the entrance.
40:10This is the longest and most laborious part of her motherly duties.
40:15But now, without any more work from her,
40:18her young will have all the food it needs to develop into an adult.
40:25Methotra, however, is not afraid of ants.
40:30She is not afraid of ants.
40:33She is not afraid of ants.
40:36Her young will have all the food it needs to develop into an adult.
40:45Underground nests are certainly among the best protected of all insect nurseries,
40:50and indeed, they're very difficult for parasites to break into.
40:56Ants defend their colonies against intruders with great ferocity.
41:02And yet, here in this meadow in central Europe,
41:05there are ant nests where intruders live undetected.
41:10And there's one right here.
41:20This is the caterpillar of a blue butterfly.
41:26And it's lived in this nest, undetected and protected by the ants,
41:31and fed by them for the last two years.
41:35Indeed, it's been so thoroughly accepted by the ants
41:39that they will try and rescue it in preference to the young of their own queen,
41:45as, in fact, they're doing right now.
41:52But how do these caterpillars get into the ant's nest in the first place?
42:02Alcon blue butterflies begin their courtship in June and July.
42:08They're surely one of the lovely sights of a European summer
42:12as they flutter and flirt among the flowers of the meadow.
42:25Male and female meet and join.
42:32Once they have mated, the female alcon blue must find a gentian plant.
42:46Here she lays her eggs.
43:02The caterpillars, when they hatch,
43:05stay feeding on the gentian for a couple of weeks.
43:09But eventually they fall to the ground.
43:14There are ants everywhere in a meadow like this and they soon find it.
43:21It smells just like one of their own larvae
43:24and they start to haul it back to where one of their larvae should be,
43:28in their nest.
43:32Other foragers from the same nest have found another.
43:38During the next few weeks, as many as half a dozen may be taken back to the nest.
43:49Here they're hauled down to the nursery chambers
43:52and put with the ants' other eggs and larvae.
43:57And because the caterpillars continue to produce a pheromone
44:00exactly like that produced by the young ants themselves,
44:04they're treated as if they were young ants,
44:06even though they're bigger and a different colour.
44:11The caterpillars even mimic the sound the ants make when they beg for food,
44:16so the workers dutifully feed and clean them.
44:21You might think that this caterpillar has protected itself very well
44:26by deceiving these ants,
44:28but life in the undergrowth is full of surprises.
44:35An ignumen wasp, it too, like the blue butterfly,
44:39wants to get its young into an ant's nest.
44:42But not merely as lodgers, it has a more sinister intention.
44:47Somehow or other, in a meadow full of ant's nests,
44:50it can detect which one harbours a butterfly caterpillar,
44:54and this, it decides, is one of those.
44:58Once inside, the ants start to attack it, as you might expect,
45:02but then the ants' behaviour changes.
45:05There's pandemonium.
45:06The wasp has released a pheromone that makes the ants attack one another.
45:12With the defenders fighting among themselves,
45:15the wasp is able to go deeper into the nest.
45:20It's reached the nursery, and here lie the caterpillars.
45:23Now they are defenceless.
45:33The caterpillars are now in the nest.
45:37The wasp sets about injecting each of them with an egg.
45:44A few ants do their best to prevent this,
45:47but there is no real opposition.
45:58While most of the ants continue to fight among themselves,
46:02the wasp finds a second caterpillar.
46:08Another egg is laid.
46:21The wasp leaves.
46:26With the wasp gone, the caterpillar is left alone.
46:32The ant colony slowly returns to normal.
46:35The caterpillars are still there, alive and apparently well,
46:39and the ants continue to care for them.
46:42Once the caterpillars are fully grown,
46:45each starts to construct the chrysalis,
46:48which all butterflies need as a protection
46:50while they turn themselves into adults.
46:56Each chrysalis is cleaned and protected by the ants
46:59as if it were one of their own pupae.
47:05One begins to hatch.
47:19Out of it comes, yes, a blue butterfly.
47:24It leaves its foster home.
47:29Out in the open, its limp wings can expand.
47:36And now it's ready to flutter and flirt, just as its parents did.
47:43And the ants are still bewitched by the traces of pheromone
47:47clinging to the empty shell the butterfly leaves behind.
47:54But there are still others in the nest, as yet unhatched.
48:05And out of this one comes not a butterfly, but a wasp.
48:11Hard-wired into the microscopic brain of this ordinary-looking insect
48:16are a whole series of skills, sensitivities and reactions
48:20that will enable it, in its turn,
48:23to give its own offspring a special start in life.
48:26It can detect what the ants themselves find undetectable.
48:31It can tell the difference between a butterfly and a wasp.
48:35It can detect what the ants themselves find undetectable.
48:39It can tell the difference between an ant larva and the butterfly larva.
48:45What is more, in a meadow of 100 ants' nests,
48:48it will be able to find the one that contains the butterfly caterpillar.
48:53How it does it, we have no idea.
48:56So it seems that among the animals of the undergrowth,
49:00there are many beneficial partnerships,
49:03but exploitation and deception can work just as well.
49:33Transcription by ESO. Translation by —