0:00:37 > 0:00:41Leaf-cutter ants cleaning the refuse out of their nest.
0:00:41 > 0:00:46Every single one of these tiny creatures knows where it's going
0:00:46 > 0:00:49and what it's got to do when it gets there.
0:00:49 > 0:00:56And, furthermore, there are about ten million more of them in this huge underground nest beneath me.
0:00:56 > 0:01:00They are all members of one highly organised society.
0:01:00 > 0:01:07But they're not the blindly mechanical, robotic slaves that we once thought they were.
0:01:07 > 0:01:14Indeed, we now know that every insect society is full of conflict,
0:01:14 > 0:01:17power struggles and mutinies.
0:01:21 > 0:01:27Social insects construct the tallest of all non-human buildings.
0:01:27 > 0:01:33Like these huge termite hills here in Australia.
0:01:33 > 0:01:37They protect their colonies with great ferocity.
0:01:37 > 0:01:41They increase the size of their societies at an alarming rate.
0:01:45 > 0:01:52And they're capable of mobilising huge armies to make wars on their neighbours.
0:01:52 > 0:01:55But how did these great communities develop?
0:01:55 > 0:02:00Most insects, like this little sand wasp here in the deserts of Arizona,
0:02:00 > 0:02:04live solitary lives.
0:02:04 > 0:02:11This one has just dug a hole in which she is going to lay her eggs.
0:02:11 > 0:02:14But then she does something else.
0:02:14 > 0:02:18She will cater for her as yet unhatched young
0:02:18 > 0:02:24by putting a caterpillar inside that hole on which they can feed.
0:02:24 > 0:02:30And that is a very important stage in the development of the social life.
0:02:32 > 0:02:38In fact, it's the very basis on which all the great insect societies are built.
0:02:39 > 0:02:44This species of wasp, however, is still at the stage of working alone.
0:02:47 > 0:02:50After stocking each nest with a caterpillar,
0:02:50 > 0:02:53she blocks the entrance to deter thieves.
0:02:55 > 0:02:58Her burrow may be several centimetres deep.
0:02:58 > 0:03:01At the bottom lies the paralysed caterpillar.
0:03:01 > 0:03:07And on its back, there is now a wasp grub, feeding on it.
0:03:08 > 0:03:13The female wasp makes several of these nests a few feet apart
0:03:13 > 0:03:16and stocks each of them with living food for her young.
0:03:19 > 0:03:23Can there be a more hard-working mother?
0:03:23 > 0:03:26Despite all her attempts at parental care,
0:03:26 > 0:03:30the vast majority of her young will not survive.
0:03:30 > 0:03:34She's too busy hunting for more caterpillars
0:03:34 > 0:03:37to be able to guard all her nest sites.
0:03:39 > 0:03:43Back in the distant evolutionary past,
0:03:43 > 0:03:48other wasps started to build their nests alongside one another.
0:03:48 > 0:03:52And here on the coast of Panama, paper wasps still do so.
0:03:52 > 0:03:56Grouping their cells together means that even though you have
0:03:56 > 0:03:58to leave your eggs to collect food,
0:03:58 > 0:04:01there will always be someone around on guard.
0:04:03 > 0:04:05The wasps are all sisters.
0:04:05 > 0:04:09But, as often happens, one tends to dominate the rest.
0:04:09 > 0:04:12She starts to bite her sisters with great brutality.
0:04:12 > 0:04:15She is the boss, the queen.
0:04:15 > 0:04:19The others may build cells, but only she will lay eggs in them.
0:04:22 > 0:04:25Many of the genes in these eggs are the same as those carried by her
0:04:25 > 0:04:30sisters, and the sisters look after the eggs as if they were their own.
0:04:30 > 0:04:33And now, because the nest is so well guarded,
0:04:33 > 0:04:38the family rears more young than if each female were to nest alone.
0:04:39 > 0:04:44So as each egg is laid, the sisters take steps to protect it.
0:04:44 > 0:04:47To do that they need building material.
0:04:50 > 0:04:54They chew wood into pulp and then use it to build a protective
0:04:54 > 0:05:01wall around each egg, a cell, so a colonial nest begins to grow.
0:05:01 > 0:05:07With more and more young females needing to be fed, the adults go hunting.
0:05:39 > 0:05:44Each returning wasp bringing prey is greeted by the other workers.
0:05:45 > 0:05:48They squabble over food.
0:05:48 > 0:05:50The queen takes the lion's share.
0:05:50 > 0:05:54Those of her sisters and daughters who are high up on the social scale
0:05:54 > 0:05:59also get big helpings, because they bully the junior females.
0:06:07 > 0:06:11In fact, the food isn't eaten by the adult who wins it.
0:06:11 > 0:06:14She feeds it to her developing younger sisters.
0:06:26 > 0:06:29This grouping, an enormous single-sex family,
0:06:29 > 0:06:32was the first step towards the development of
0:06:32 > 0:06:38insect societies containing millions of individuals, and it's still their basic structure.
0:06:42 > 0:06:45The forests in which the first wasps hunted
0:06:45 > 0:06:49were dominated by horsetails and conifers.
0:06:49 > 0:06:53They relied upon the wind to distribute their pollen.
0:06:53 > 0:06:56But then, about a hundred million years ago,
0:06:56 > 0:07:00a new kind of plant appeared which recruited insects to do the job.
0:07:00 > 0:07:04And they did it with nectar-loaded flowers.
0:07:05 > 0:07:09Some of these recruits then abandoned hunting
0:07:09 > 0:07:13and concentrated instead on this new food.
0:07:13 > 0:07:14They became bees.
0:07:17 > 0:07:21Today there are about 20,000 different species of them.
0:07:26 > 0:07:32This queen bumblebee mated at the end of last summer, before she hibernated.
0:07:32 > 0:07:41But now she has gone off to look for a new home, because she's ready at last to lay those eggs.
0:07:43 > 0:07:47She may take some time to find just the right place.
0:07:52 > 0:07:54A deserted mouse hole.
0:07:54 > 0:07:57Ideal!
0:07:58 > 0:08:04First she makes a little wax pot in which she lays a group of fertilised eggs.
0:08:04 > 0:08:07In due time, these hatch into young females.
0:08:07 > 0:08:09The queen now has her subjects.
0:08:09 > 0:08:12A colony has been established.
0:08:12 > 0:08:15From now on she does little building herself.
0:08:15 > 0:08:17Her daughters take on that job
0:08:17 > 0:08:19and they use a material that no wasp ever had.
0:08:19 > 0:08:24It oozes from between their body segments. It's wax.
0:08:26 > 0:08:28The queen also produces a chemical substance
0:08:28 > 0:08:33that permeates the nest and keeps her daughters' sexuality in check.
0:08:33 > 0:08:37Their job is not to produce eggs but to look after their younger sisters.
0:08:42 > 0:08:46More and more young workers are hauling themselves out of their cells.
0:08:55 > 0:08:59They don't have to travel far to find their first adult meal.
0:09:01 > 0:09:04In fact, to begin with, they stay inside the nest,
0:09:04 > 0:09:10helping with nest duties, feeding the young, keeping the place clean, building more cells.
0:09:11 > 0:09:15After a few days, they begin to venture outside the nest,
0:09:15 > 0:09:17to help in collecting food.
0:09:19 > 0:09:22If the colony is to be properly nourished,
0:09:22 > 0:09:25they must gather not only nectar but pollen.
0:09:34 > 0:09:40Nectar they transport in their crops, but pollen is held in a tiny
0:09:40 > 0:09:44ball by a brush of stiff hairs on their two hind legs.
0:09:44 > 0:09:47A worker can carry a lump weighing half as much as she does herself.
0:09:49 > 0:09:54Each bundle is carefully unloaded into one of the storage cells.
0:10:08 > 0:10:11The pollen isn't eaten by workers.
0:10:11 > 0:10:13They unselfishly bring it back for the larvae,
0:10:13 > 0:10:18for it's rich in protein and essential food for their development.
0:10:24 > 0:10:29By the late summer, there may be more than 200 workers in the nest.
0:10:29 > 0:10:34Although the colony is now close to its maximum size,
0:10:34 > 0:10:39the queen is still laying, but these batches of eggs are different.
0:10:39 > 0:10:42She's now stopped producing the chemical substance that
0:10:42 > 0:10:48repressed the sexual development of her daughters, so these eggs will develop into new queens.
0:10:50 > 0:10:56The change affects not just her eggs but her existing daughters, the workers.
0:10:56 > 0:10:59No longer restrained by the queen's chemical control,
0:10:59 > 0:11:01some workers have started laying their own eggs.
0:11:01 > 0:11:05This doesn't suit the queen, and she destroys them.
0:11:12 > 0:11:14The workers haven't mated,
0:11:14 > 0:11:18but their eggs can develop nonetheless and become males.
0:11:18 > 0:11:21The queen eats as many of these eggs as she can find,
0:11:21 > 0:11:23because, as well as queen eggs,
0:11:23 > 0:11:27she's also producing male eggs and can't tolerate the competition.
0:11:31 > 0:11:36She keeps such a close watch that she manages to destroy the workers' eggs almost as soon as they're laid.
0:11:39 > 0:11:42The end of summer approaches.
0:11:44 > 0:11:46There's now anarchy in the colony.
0:11:46 > 0:11:48The social order has collapsed.
0:11:48 > 0:11:53Many of the workers whose eggs are being destroyed by the queen start to attack her.
0:11:55 > 0:11:56The onslaught is brutal.
0:11:56 > 0:11:58No quarter is given.
0:12:20 > 0:12:23Eventually, they sting her to death.
0:12:25 > 0:12:28The end of the colony has come.
0:12:29 > 0:12:33None of the workers will survive the winter,
0:12:33 > 0:12:38but the young queens will have left the nest and found males.
0:12:38 > 0:12:43It's they who will establish new colonies next spring.
0:12:44 > 0:12:47Bumblebees have a particular problem.
0:12:47 > 0:12:53In any given area, there is only a limited number of holes that are suitable for nests.
0:12:53 > 0:12:59European honeybees, which in the wild nest in holes in trees, have similar difficulty.
0:12:59 > 0:13:06But some bees have adopted a very radical solution, a very brave solution, to that difficulty.
0:13:06 > 0:13:09They nest out in the open,
0:13:09 > 0:13:14but at the top of tall trees, sometimes VERY tall trees.
0:13:18 > 0:13:24These are the giant Asiatic bees, the biggest of all honeybees.
0:13:24 > 0:13:28They are found from the Himalayas all the way down to southeast Asia.
0:13:28 > 0:13:31These colonies are in Malaysia.
0:13:32 > 0:13:42They defend themselves with stings, very, very powerful stings, which is why I have to wear a bee suit.
0:13:42 > 0:13:47And it's not just against one bee that you have to guard yourself,
0:13:47 > 0:13:51because if one bee attacks you, it releases a pheromone,
0:13:51 > 0:13:56a chemical signal, which is detected by the others in the comb,
0:13:56 > 0:14:01and within seconds there will be hundreds, indeed, probably thousands, of them
0:14:01 > 0:14:06all around you, launching a mass attack and stinging you.
0:14:06 > 0:14:10And some of those stings can actually go through a bee suit.
0:14:10 > 0:14:13So it's something to be avoided.
0:14:41 > 0:14:45Stinging is a very expensive form of defence,
0:14:45 > 0:14:48because when a bee loses its sting, it dies.
0:14:48 > 0:14:54So it's better for the colony to warn predators off before they have to fight them off.
0:14:54 > 0:14:58And they warn them with some dramatic displays.
0:14:58 > 0:15:01I've got a reproduction of a hornet,
0:15:01 > 0:15:04which is one of the main enemies of bees.
0:15:04 > 0:15:06I'll see if I can get them to do it.
0:15:06 > 0:15:07Just watch.
0:15:07 > 0:15:09There!
0:15:09 > 0:15:14See? There's a moving wave which passes over the surface of the colony,
0:15:14 > 0:15:21and that not only produces an impressive pattern, but it also makes it very difficult for any
0:15:21 > 0:15:30aggressor, like, perhaps, a hornet, which eats bees, to actually land on that moving carpet of wings.
0:15:33 > 0:15:38The colony's great treasure, of course, is its huge store of honey.
0:15:41 > 0:15:48This is produced from nectar, which the bees industriously collect from flowers.
0:15:48 > 0:15:52They systematically expose it to the air so that the water it contains
0:15:52 > 0:15:56evaporates and the nectar becomes sweeter and thicker.
0:15:56 > 0:15:58Eventually it turns into honey.
0:16:07 > 0:16:12The combs in which they store it are continuously guarded by the covering of bees.
0:16:12 > 0:16:16They cling so thickly that it might seem that nothing could get past them.
0:16:16 > 0:16:21But some thieves know how to do so, particularly at night.
0:16:27 > 0:16:31A death's-head hawk moth flies over the surface of
0:16:31 > 0:16:37the colony, and goes so close to it that the bees are alarmed enough to wave their warning.
0:16:42 > 0:16:44But the moth is not put off.
0:16:44 > 0:16:46It wants honey.
0:16:53 > 0:16:59Amazingly, it manages to land on the carpet of bees and quickly pushes its way through them.
0:17:03 > 0:17:05A quick sip of honey, and it's off.
0:17:07 > 0:17:11It succeeds because, although it looks nothing like a bee to our eyes,
0:17:11 > 0:17:15it has camouflaged itself with a smell, a pheromone,
0:17:15 > 0:17:19that convinces the bees that it's one of them.
0:17:19 > 0:17:25But in spite of such raids, bees, thanks to their stings, retain their precious honey, precious
0:17:25 > 0:17:31because it is that that enables them to survive a season without flowers.
0:17:32 > 0:17:39While some descendants of the wasps became flower-foraging bees, others
0:17:39 > 0:17:43remained hunters but went down to the ground to search for their prey.
0:17:43 > 0:17:46There, wings were more of a hindrance than a help,
0:17:46 > 0:17:50and these insects lost their wings for most of their lives.
0:17:50 > 0:17:52They're the ants.
0:17:52 > 0:17:59These are wood ants and they build nests even bigger than those of the giant bees.
0:17:59 > 0:18:02This one is in the pine forests of the Alps.
0:18:06 > 0:18:12Hunting parties go out from the nest along well-established trails to search for prey.
0:18:16 > 0:18:19Anything their own size is quickly overpowered.
0:18:23 > 0:18:29But by working together, wood ants can tackle prey much bigger than themselves.
0:18:29 > 0:18:35Some caterpillars are covered with stinging hairs, but the ants cut these off, one by one.
0:18:35 > 0:18:39And they can slice right through a beetle's hard armour.
0:18:53 > 0:18:57Now they are attacking another hunter, a spider.
0:18:57 > 0:19:01Everything they catch is taken back to the colony to be shared by those workers
0:19:01 > 0:19:04that stayed at home, looking after the young.
0:19:16 > 0:19:19The disadvantage of building a huge nest like this
0:19:19 > 0:19:21is that you're very obvious to predators.
0:19:21 > 0:19:27But these ants have a very effective way of defending themselves. Watch.
0:19:40 > 0:19:45Mmm, the unmistakable, acrid smell of formic acid.
0:19:47 > 0:19:51Most ants, like their wasp ancestors, have stings.
0:19:51 > 0:19:53But not these wood ants.
0:19:53 > 0:19:58Instead of injecting poison, they squirt it, and very accurately too.
0:20:06 > 0:20:09They don't eat just meat.
0:20:09 > 0:20:15They also visit aphids that sit in the branches above drinking the pine tree's sap.
0:20:15 > 0:20:21This contains more sugar than the aphids need, so the ants drink the excess.
0:20:22 > 0:20:26And they collect it just as fast as the aphids excrete it.
0:20:29 > 0:20:30They carry it back to the nest,
0:20:30 > 0:20:34but in this case they transport it inside their swollen stomachs.
0:20:34 > 0:20:39In fact, this liquid, honeydew, makes up more than two thirds of the colony's diet.
0:20:43 > 0:20:49All these wood-ant nests are connected to one another by trails.
0:20:49 > 0:20:53And indeed, they're also genetically related to one another.
0:20:53 > 0:20:57There's some 1,200 of them in this one patch of forest,
0:20:57 > 0:21:03and that makes this what is thought to be the biggest super-colony of ants in the whole world.
0:21:05 > 0:21:10By mid-June the super-colony is ready to reproduce.
0:21:10 > 0:21:14Out of every nest, among the workers, come individuals with wings.
0:21:14 > 0:21:17Some nests produce only males.
0:21:18 > 0:21:21They take off in droves.
0:21:29 > 0:21:32Other nests produce only females.
0:21:34 > 0:21:39Both sexes, now that they're winged, look remarkably like wasps,
0:21:39 > 0:21:40a reminder of their ancestry.
0:21:45 > 0:21:47Unlike wasps, however,
0:21:47 > 0:21:52these flyers are not very confident about getting into the air.
0:22:10 > 0:22:15Males and females assemble in the nearby meadows.
0:22:15 > 0:22:17The queens lay down chemical trails,
0:22:17 > 0:22:21so that the males may quickly discover exactly where they are,
0:22:21 > 0:22:24and the males are quick to take the hint.
0:22:37 > 0:22:39The males only live for a few days,
0:22:39 > 0:22:42and they mate as quickly and as frequently as they can.
0:22:49 > 0:22:53A queen, on the other hand, may live for as long as ten years,
0:22:53 > 0:22:59and a single mating will provide her with enough sperm to last for her entire life.
0:22:59 > 0:23:02For a female, mating is often a bit of a battle.
0:23:02 > 0:23:07Sometimes she has to bite a male to make him release her, sometimes
0:23:07 > 0:23:11she has to hang on to him because he's impatient and wants to move on.
0:23:16 > 0:23:20The newly mated queens gather together in the undergrowth.
0:23:20 > 0:23:23Here they shed their wings.
0:23:23 > 0:23:27They've found their males, so their travelling is over.
0:23:33 > 0:23:38Now each must find an existing nest in which to lay her eggs.
0:23:42 > 0:23:45This one encounters a column of workers.
0:23:45 > 0:23:48A wood-ant nest may contain as many as a thousand queens.
0:23:48 > 0:23:52But will these workers allow her to be one of them?
0:23:52 > 0:23:55If they don't, they will bite her to death.
0:23:57 > 0:23:59She's been accepted.
0:23:59 > 0:24:03The workers have detected chemical clues on her body that tells them
0:24:03 > 0:24:07that she's originally from one of the nests in their super-colony.
0:24:07 > 0:24:08She's large and fat.
0:24:08 > 0:24:10Walking is not easy for her.
0:24:10 > 0:24:14A single worker carries her along the trail back home,
0:24:14 > 0:24:19perhaps even to the same nest in which she started life.
0:24:21 > 0:24:24Ants live almost everywhere.
0:24:24 > 0:24:30The water falling in this mangrove swamp in Australia exposes in the wet mud...
0:24:30 > 0:24:32an ants' nest!
0:24:32 > 0:24:34Every time the tide recedes,
0:24:34 > 0:24:39the ants must repair any damage the water may have caused.
0:24:41 > 0:24:44Collapsed entrances must be re-opened
0:24:44 > 0:24:46and blocked tunnels cleared.
0:24:56 > 0:24:58Now that the mud flats are exposed,
0:24:58 > 0:25:02the ants hurry to collect what food the tide might have delivered.
0:25:05 > 0:25:08But there are still some stretches of water to be crossed.
0:25:16 > 0:25:20The surface tension of the water supports them
0:25:20 > 0:25:22as they dance across it.
0:25:22 > 0:25:25Sometimes they actually swim.
0:25:43 > 0:25:47And there has indeed been a new delivery of food.
0:25:54 > 0:25:56But the tide has also created a problem.
0:25:56 > 0:25:58It has washed away the chemical trails
0:25:58 > 0:26:01that mark the frontiers of their territory,
0:26:01 > 0:26:03so there's now no clear boundary
0:26:03 > 0:26:06between them and ants belonging to a neighbouring colony.
0:26:09 > 0:26:12The interrogation of a stranger is complex and detailed.
0:26:14 > 0:26:16Who are you? Where do you come from?
0:26:19 > 0:26:22Answers are readily given and accepted.
0:26:32 > 0:26:37But every now and then, they have to fight to settle the question.
0:26:47 > 0:26:49They may have sorted out their disagreement,
0:26:49 > 0:26:52but now there is a bigger threat to both of them.
0:26:52 > 0:26:55The tide is turning again.
0:26:55 > 0:26:57They must get back to the safety of their nests.
0:27:08 > 0:27:10While the tide has been out,
0:27:10 > 0:27:13larvae and pupae have been moved around the nest
0:27:13 > 0:27:17to keep them at the temperature needed for their proper development.
0:27:17 > 0:27:20Now they must be moved again, for the nest is not watertight.
0:27:20 > 0:27:24Many of the tunnels and chambers are flooded with every tide.
0:27:24 > 0:27:26There's no time to waste.
0:27:42 > 0:27:45But the water doesn't reach every part of the nest,
0:27:45 > 0:27:49for the ants have constructed bell-shaped chambers
0:27:49 > 0:27:56that trap pockets of air and so create refuges where the adults and the young can sit out the high tide.
0:28:13 > 0:28:14Here in Arizona,
0:28:14 > 0:28:18the problem for an ant is not too much water but too little.
0:28:18 > 0:28:23The rainfall is so low that there's hardly any vegetation and very little to eat,
0:28:23 > 0:28:27so an ant has to be prepared to eat whatever it can find.
0:28:27 > 0:28:34There are seeds, but seeds are very tough and you need very powerful jaws to crack them.
0:28:34 > 0:28:39But then, that's exactly what these harvester ants have got.
0:28:44 > 0:28:47They make an intensive search of the sand.
0:28:47 > 0:28:49Almost any seed will be collected.
0:28:49 > 0:28:52Food around here is very scarce.
0:28:52 > 0:28:54They can't afford to be fussy.
0:29:06 > 0:29:10They carry their gleanings back to the nest to store it in larders,
0:29:10 > 0:29:13many of which are several metres below ground.
0:29:16 > 0:29:20But, like the mangrove ants, they must work fast.
0:29:20 > 0:29:25The desert warms quickly and before long the heat will be intolerable.
0:29:27 > 0:29:32By nightfall, the harvesters are back inside the nest.
0:29:32 > 0:29:36But there's still a lot going on out in the desert.
0:29:36 > 0:29:39There's another ant here too, the night ant.
0:29:39 > 0:29:42This is one of their nests in front of me.
0:29:42 > 0:29:48They normally only come out after dark and they're generalists, they'll eat pretty well anything.
0:29:48 > 0:29:51But they have a particular taste for seeds.
0:29:51 > 0:29:56The trouble is that the harvester ants will have gathered all the seeds during the day,
0:29:56 > 0:29:59unless the night ants can do something about it.
0:30:02 > 0:30:09Just after dark, the night ants start a major spoiling operation against their rivals.
0:30:11 > 0:30:15They start to shift stones and fragments of plants
0:30:15 > 0:30:18to block up some holes near their nest.
0:30:32 > 0:30:35By morning, it's clear what they've done.
0:30:35 > 0:30:40They've trapped the harvesters inside their own nests.
0:30:47 > 0:30:50The harvesters now have a lot of work to do
0:30:50 > 0:30:53before they can get out to collect more seeds.
0:30:53 > 0:30:56They clear away the rubble as quickly as they can.
0:31:06 > 0:31:08But this takes time.
0:31:08 > 0:31:10If they're seriously delayed,
0:31:10 > 0:31:13the day will be too hot for them to spend time out in the open.
0:31:13 > 0:31:17So today, they can't collect as much as they normally do.
0:31:21 > 0:31:26That means that by nightfall there will still be seeds on the ground
0:31:26 > 0:31:28for the night ants to collect.
0:31:34 > 0:31:37Not all ants live in permanent nests.
0:31:37 > 0:31:40In the tropical forests of Africa and South America,
0:31:40 > 0:31:42there are some that are nomads.
0:31:44 > 0:31:49These army ants in the rainforests of central America are camped in the base of a tree.
0:31:49 > 0:31:51They've been there for three weeks.
0:31:51 > 0:31:55During this time, the queen has been laying eggs, several thousand a day.
0:31:55 > 0:32:00The army has also been ransacking the surrounding forest for prey.
0:32:00 > 0:32:04But now it's time for them to find new hunting grounds,
0:32:04 > 0:32:06so once more they start to march.
0:32:18 > 0:32:24The site for the new bivouac has not been picked by the queen but by the workers.
0:32:24 > 0:32:27Scouts have been exploring the neighbourhood,
0:32:27 > 0:32:29and they've decided on a new place.
0:32:29 > 0:32:33And now their chemical trails are leading the whole colony
0:32:33 > 0:32:35from the old bivouac to the new one.
0:32:39 > 0:32:40As in an army,
0:32:40 > 0:32:44the soldiers are prepared to risk their lives for the common good.
0:32:44 > 0:32:48A group of them interlock their bodies to form a safety barrier
0:32:48 > 0:32:53that will catch any of their companions that might slip off this sloping trunk.
0:32:53 > 0:32:55They take everything with them -
0:32:55 > 0:32:59larvae, food and in this case, and very rarely seen, winged males.
0:33:14 > 0:33:19By the time daylight comes, the army has established a new bivouac.
0:33:19 > 0:33:22Its walls and tunnels are formed by the interlinked bodies
0:33:22 > 0:33:25of hundreds and thousands of individuals.
0:33:33 > 0:33:35But this is only a temporary camp.
0:33:35 > 0:33:38They still haven't reached fresh hunting grounds.
0:33:38 > 0:33:42Even so, they must eat, and the workers set off to find food.
0:34:12 > 0:34:16There are probably a million individual ants in this one colony,
0:34:16 > 0:34:22and together they are collaborating and cooperating so that the colony has become one great super-organism.
0:34:22 > 0:34:26There's no central controlling intelligence as such.
0:34:26 > 0:34:31Instead, the behaviour of the super-organism is the cumulative result
0:34:31 > 0:34:35of thousands upon thousands of tiny mini-decisions by individual ants.
0:34:35 > 0:34:39A worker moves forward into new territory, leaving a chemical trail
0:34:39 > 0:34:44behind it, and then another, following in its trail, advances still a little further.
0:34:44 > 0:34:50So the super-organism as a whole is moving through the forest searching for food.
0:34:56 > 0:35:01These hunters can subdue almost any other creature in the undergrowth.
0:35:01 > 0:35:06Some predators may be armed with virulent poisons, but their attackers are too small to sting.
0:35:09 > 0:35:11A lizard has no defence at all.
0:35:31 > 0:35:36A special caste of workers with particularly large jaws
0:35:36 > 0:35:40protect the smaller workers as they sting their prey and butcher it.
0:35:51 > 0:35:56The venom in their stings liquefies the tissues of their victims so that
0:35:56 > 0:36:00the bodies are more easily cut up into smaller pieces to transport.
0:36:19 > 0:36:24The chemical trails laid down by the first scouts have now been
0:36:24 > 0:36:28strengthened and broadened by the passage of many, many more workers.
0:36:28 > 0:36:32And now those trails are serving as highways along which booty
0:36:32 > 0:36:37is being brought back to the bivouac to feed the young brood.
0:36:56 > 0:37:01Remarkably, almost as soon as these workers return with food,
0:37:01 > 0:37:04scouts begin to search for a new bivouac site.
0:37:05 > 0:37:09The colony will move again tonight and every night
0:37:09 > 0:37:13for the next few weeks until the queen is ready to lay more eggs.
0:37:16 > 0:37:20When it comes to creating a permanent home for the colony,
0:37:20 > 0:37:25the champions by far are these tiny creatures, termites.
0:37:26 > 0:37:30Unlike ants, all termites are vegetarians.
0:37:30 > 0:37:34They are, in fact, descended not from wasps but from cockroaches,
0:37:34 > 0:37:39and their huge nests act not only as their fortresses but their food stores.
0:37:41 > 0:37:46They build with nothing but mud and their own excrement, yet their nests are gigantic.
0:37:46 > 0:37:49If termites were our size, some of their homes would be
0:37:49 > 0:37:52four times as tall as New York skyscrapers
0:37:52 > 0:37:56and measure up to five miles across at their base.
0:37:56 > 0:38:00These are not quite so tall, but they are particularly remarkable for another reason.
0:38:03 > 0:38:09Every one of these termite hills points in the same direction, north and south.
0:38:09 > 0:38:13It's as though they were needles in a compass.
0:38:13 > 0:38:17And indeed, they are called magnetic termites.
0:38:17 > 0:38:25They in fact take their cue for building from the magnetism of the earth, but the benefit of
0:38:25 > 0:38:30doing so comes not from that but from the daily movement of the sun.
0:38:41 > 0:38:49In the morning, the rays of the rising sun strike the eastern face of the mound foursquare.
0:38:49 > 0:38:52And the termites, after the cold of the night, need warming up
0:38:52 > 0:38:57and are gathered in galleries immediately below this surface.
0:38:57 > 0:39:02But as the day continues, it warms up, but the termites don't overheat because the rays of the sun only
0:39:02 > 0:39:05strike the surface glancingly
0:39:05 > 0:39:10and by midday the full force of the sun is felt only on the top edge.
0:39:20 > 0:39:23As the sun moves towards the west,
0:39:23 > 0:39:26so this face becomes roastingly hot.
0:39:26 > 0:39:32But the eastern face falls into shadow and remains relatively cool
0:39:32 > 0:39:37and the termites stay at the temperature that suits them best.
0:39:37 > 0:39:40Other termites escape the heat of the day
0:39:40 > 0:39:43by retreating to deep cellars below their mounds.
0:39:43 > 0:39:47But these magnetic termites colonise areas that flood during the
0:39:47 > 0:39:52rainy season, and the ground beneath them is regularly waterlogged.
0:39:52 > 0:39:59So their compass-like mounds are a response not just to the movement of the sun but to badly drained sites.
0:40:01 > 0:40:07Here in South Africa, it can also get very hot, but there's no danger of flooding,
0:40:07 > 0:40:14so termites can take refuge from the heat below ground, where it's cool and relatively stable.
0:40:14 > 0:40:20But two million insects living below ground create a different kind of problem.
0:40:20 > 0:40:23The air around them gets stale.
0:40:23 > 0:40:28So termites need to have a way of linking the underground air
0:40:28 > 0:40:31with the fresh air above, a ventilation system.
0:40:31 > 0:40:34And they do that with this.
0:40:34 > 0:40:39And to see how it works, you've got to look inside.
0:40:41 > 0:40:48Using the latest scanning techniques, we can create a picture of the mound's interior.
0:40:48 > 0:40:52An intricate network of passages lead to a central chimney.
0:40:54 > 0:41:00Hot, stale air from the insect population below rises up through the chimney.
0:41:03 > 0:41:09But the top of the mound is sealed, so how does this stale air escape?
0:41:10 > 0:41:15The mound may look as though it has strong defensive walls like a fortress,
0:41:15 > 0:41:18but in fact these walls are porous
0:41:18 > 0:41:22and their primary purpose is to harness the wind.
0:41:22 > 0:41:27Fresh air, blowing against the side of the mound, is forced through the tiny holes in these walls.
0:41:27 > 0:41:34From there, it travels through the smaller tunnels until it reaches the central chimney.
0:41:34 > 0:41:39Here, the cooler, fresh air mixes with the hot, stale air
0:41:39 > 0:41:42rising from the insect community below.
0:41:42 > 0:41:46Meanwhile, some air is blown around the side of the mound.
0:41:46 > 0:41:54This creates a suction that pulls the stale air out of the chimney and out through the outer walls.
0:41:54 > 0:41:58So an internal air current is created and the whole mound ventilated.
0:42:00 > 0:42:05The mound's inhabitants spend most of their time close to or below ground level.
0:42:07 > 0:42:09Beneath their living quarters,
0:42:09 > 0:42:13there are garden chambers, where the termites cultivate a fungus
0:42:13 > 0:42:17that rots the wood and vegetation they collect and make it digestible.
0:42:18 > 0:42:23Farther down still, the queen lies in her own chamber.
0:42:25 > 0:42:29Her huge body is a gigantic egg-producing factory.
0:42:29 > 0:42:33She is so swollen that she can't look after herself.
0:42:33 > 0:42:40The workers must constantly clean her and feed her with food from their own crops.
0:42:40 > 0:42:44Her partner, with whom she founded the colony maybe 20 years ago,
0:42:44 > 0:42:47is still with her and mates with her throughout her life.
0:42:50 > 0:42:55She lays eggs at an extraordinary rate, as many as 30,000 a day.
0:42:57 > 0:43:03As she produces them, so workers remove them from the royal chamber and take them to nurseries.
0:43:03 > 0:43:09There they'll be fed on compost from the fungus gardens until they turn into adults.
0:43:14 > 0:43:19The super-organism that lives in this great castle
0:43:19 > 0:43:24crops the surrounding vegetation just about as severely as an antelope.
0:43:24 > 0:43:32The density of individual termites around here is extraordinary, over 100,000 per square metre.
0:43:32 > 0:43:39And just as there are lions and leopard that hunt antelope, so in the undergrowth
0:43:39 > 0:43:44there are insect hunters which prey on the tiny herbivores -
0:43:44 > 0:43:47the ants, the termites' ancient enemy.
0:43:49 > 0:43:53Matabele ants, specialist termite hunters.
0:43:59 > 0:44:04A scout has laid down a clear chemical trail,
0:44:04 > 0:44:09and this battalion of workers have picked it up and are following it.
0:44:09 > 0:44:13There may be only a few hundred of them, but they're going to severely
0:44:13 > 0:44:16test the defences of a termite colony.
0:44:23 > 0:44:26The mound has formidable guards, soldier termites.
0:44:39 > 0:44:43The ants have a special technique for dealing with these soldiers.
0:44:43 > 0:44:44They grab the termite's jaw
0:44:44 > 0:44:49and then sting it in the only vulnerable place on its head, in its mouth.
0:44:57 > 0:45:00The ants' front line breaks into the colony.
0:45:00 > 0:45:04Reinforcements for the termite soldiers arrive quickly.
0:45:04 > 0:45:07Already there are casualties on both sides.
0:45:10 > 0:45:13But the invaders overwhelm the defenders.
0:45:19 > 0:45:23It's not to the ants' advantage to kill an entire termite colony,
0:45:23 > 0:45:28any more than it would be sensible for farmers to exterminate their cattle.
0:45:28 > 0:45:32Better to let most survive, so that they can be regularly raided.
0:45:32 > 0:45:36So although there are millions of termites in the colony, the Matabele
0:45:36 > 0:45:39ants rarely go deep into the nest to press home their victory.
0:45:58 > 0:46:00The raid lasts less than 15 minutes.
0:46:01 > 0:46:05Nonetheless, the spoils are impressive.
0:46:14 > 0:46:18Termite bodies are now being piled in dumps outside the nest.
0:46:28 > 0:46:30Many of the casualties are still alive
0:46:30 > 0:46:33but paralysed by the ants' stings.
0:46:33 > 0:46:39Now the raiders have the considerable task of carrying their victims back to their nest.
0:46:41 > 0:46:45They will have to take all their booty with them.
0:46:45 > 0:46:49If any termite bodies are left behind they will be collected by scavengers.
0:46:53 > 0:46:56The termite soldiers certainly fought hard.
0:46:56 > 0:47:00One of their dead still grips a Matabele soldier in its jaws,
0:47:00 > 0:47:04which it killed before it was itself slaughtered.
0:47:12 > 0:47:15Well, it's been a successful raid.
0:47:15 > 0:47:19Many of the bigger ones have got mouthfuls of termites.
0:47:19 > 0:47:23How they manage to hold all of them in one mouthful I don't know,
0:47:23 > 0:47:26but obviously they have got a little way to go now,
0:47:26 > 0:47:32and soon the young ones back in the nest will be getting good food.
0:47:34 > 0:47:38The Matabele ants will use their plunder to raise more workers.
0:47:38 > 0:47:42Ironically, the raid will have the same effect on the termites.
0:47:42 > 0:47:45The queen will detect the loss of her soldiers and workers
0:47:45 > 0:47:49and will increase her output of eggs to repopulate the colony.
0:47:49 > 0:47:54So there will be just as much food for the Matabeles the next time they raid.
0:47:59 > 0:48:01The tiny creatures of the undergrowth
0:48:01 > 0:48:06were the first animals of any kind to colonise the land.
0:48:07 > 0:48:12They established the foundations of the land's ecosystems.
0:48:12 > 0:48:16Ultimately they were able to transcend any limitations of their
0:48:16 > 0:48:21small size by banding together in huge communities of millions
0:48:21 > 0:48:24and putting up buildings like this one.
0:48:24 > 0:48:29If we and the rest of the backboned animals were to disappear overnight,
0:48:29 > 0:48:33the rest of the world would get on pretty well.
0:48:33 > 0:48:35But if THEY were to disappear,
0:48:35 > 0:48:39the land's ecosystems would collapse.
0:48:39 > 0:48:41The soil would lose its fertility.
0:48:41 > 0:48:45Many of the plants would no longer be pollinated.
0:48:45 > 0:48:50Lots of animals - amphibians, reptiles, birds, mammals - would have nothing to eat,
0:48:50 > 0:48:56and our fields and pastures would be covered with dung and carrion.
0:48:56 > 0:49:00These small creatures are within a few inches of our feet
0:49:00 > 0:49:06wherever we go on land, but often they're disregarded.
0:49:06 > 0:49:09We would do very well to remember them.
0:49:20 > 0:49:22Everyone ready?
0:49:24 > 0:49:26Action.
0:49:28 > 0:49:32Throughout Life In The Undergrowth, we've seen the most extraordinary creatures
0:49:32 > 0:49:36living the most remarkable lives right under our noses.
0:49:41 > 0:49:42But what's most remarkable
0:49:42 > 0:49:45is that they are just the tip of the iceberg.
0:49:45 > 0:49:46Of all the animals on the planet,
0:49:46 > 0:49:50land-living invertebrates are the most numerous,
0:49:50 > 0:49:53both in kinds and absolute numbers,
0:49:53 > 0:49:57but, incredibly, we still know the least about them.
0:49:59 > 0:50:02Thankfully, as we've found out in Fly On The Wall,
0:50:02 > 0:50:05behind the scenes there are people out there every day
0:50:05 > 0:50:08pushing the boundaries of our knowledge.
0:50:12 > 0:50:14You might be surprised to hear
0:50:14 > 0:50:19that even the world's largest insect is still almost unknown.
0:50:19 > 0:50:25But in the depths of the Amazon, one man is trying to piece together a picture of its life.
0:50:28 > 0:50:35Scientist Frank Hovore is on the trail of Titanus, the titan beetle.
0:50:35 > 0:50:39Titanus isn't spectacular because of its beautiful colours or ornate structures.
0:50:39 > 0:50:42It's spectacular because it's the size of your shoe.
0:50:42 > 0:50:49There's a magic to that to those people who still have a little child inside them alive at all times
0:50:49 > 0:50:57and are fascinated, moreover thrilled, at the prospect of seeing something like this in the wild.
0:50:57 > 0:51:02But how do you find one particular beetle in the Amazon?
0:51:02 > 0:51:05Frank's answer is light.
0:51:05 > 0:51:09A bright light and a white sheet in a forest clearing is all you need.
0:51:09 > 0:51:16The hope, that if you wait long enough, the titan will be lured into the light and will find YOU.
0:51:16 > 0:51:21But it's not only titans that are attracted to light.
0:51:21 > 0:51:25Frank is a world authority on the insects of the Amazon,
0:51:25 > 0:51:29and so for him this is all part of the thrill of a titan hunt.
0:51:31 > 0:51:34Every night there is something different.
0:51:34 > 0:51:37Among these creatures
0:51:37 > 0:51:42there may well be a dozen or so that no scientist has seen before,
0:51:42 > 0:51:44let alone understood.
0:51:45 > 0:51:49Ten inches...something...
0:51:49 > 0:51:53That's an amazing nectar-gathering tube.
0:51:53 > 0:51:55You would guess there must be a flower out here,
0:51:55 > 0:51:57probably a tree, maybe a big acer,
0:51:57 > 0:52:02something that has an enormous corolla to the flower. Now watch.
0:52:02 > 0:52:04It'll just curl it right back up...
0:52:04 > 0:52:06unharmed, unperturbed.
0:52:12 > 0:52:15It's nearly dawn, and still no titan.
0:52:15 > 0:52:20But beetles love moisture, so the rain is a good omen for tomorrow night.
0:52:24 > 0:52:28The titan lives only for two weeks as a winged adult.
0:52:28 > 0:52:33Like other beetles, it must spend most of its life, possibly years,
0:52:33 > 0:52:36as a larva, but no-one has ever seen it.
0:52:38 > 0:52:42By looking for other beetle larvae,
0:52:42 > 0:52:45Frank can get an idea of how big it must be.
0:52:48 > 0:52:49Well, here we go.
0:52:51 > 0:52:54Here's our larva right here.
0:52:54 > 0:52:56We pop the lid off of him,
0:52:56 > 0:52:58or her, as it were,
0:52:58 > 0:53:00and there we are.
0:53:03 > 0:53:06This would be a harlequin beetle larva.
0:53:06 > 0:53:10The harlequin is a big beetle but nowhere near the size of a Titanus.
0:53:10 > 0:53:15The Titanus larva would be easily, oh, perhaps this much longer
0:53:15 > 0:53:18and considerably greater girth.
0:53:18 > 0:53:23If Titanus were in these logs, which clearly it is not,
0:53:23 > 0:53:26you'd be able to slide your whole arm in there
0:53:26 > 0:53:29and pull these things out like you were catching snakes.
0:53:29 > 0:53:34The problem for Frank is that even after four expeditions in search of titan,
0:53:34 > 0:53:38he's never found where such a giant larva could be hiding.
0:53:38 > 0:53:40Is it this one here?
0:53:40 > 0:53:43But an exciting new discovery gives him a clue.
0:53:43 > 0:53:45Oh, yeah, look at this.
0:53:50 > 0:53:53These great big circular holes there - look at that.
0:53:53 > 0:53:56Holes big enough to put your hand through,
0:53:56 > 0:53:58and they're certainly big enough to be Titanus.
0:54:00 > 0:54:05I'm very, very strongly suspicious that when this tree was much younger
0:54:05 > 0:54:07and this was not a rotted centre to it,
0:54:07 > 0:54:10the Titanus were working up underneath the crown
0:54:10 > 0:54:12and that this is their larval galleries.
0:54:12 > 0:54:19It seems that the titan hides away for most of its life in the heart of living trees.
0:54:19 > 0:54:23The picture of titan is getting clearer.
0:54:25 > 0:54:31Back at the sheet, Frank is hopeful that the rain has had its effect and will bring out the beetles.
0:54:33 > 0:54:35Oh, here we go.
0:54:36 > 0:54:40This one is one of my favourite beetles
0:54:40 > 0:54:44because it was named after me last year...
0:54:44 > 0:54:45..Anicacerus hovori.
0:54:47 > 0:54:51I'm very pleased to see him come into our light tonight.
0:54:51 > 0:54:53Though he's not a Titanus,
0:54:53 > 0:54:55I can live with that.
0:54:57 > 0:54:59And it's biting me -
0:54:59 > 0:55:01that makes it pretty cute.
0:55:02 > 0:55:07And next, the spectacular adult form of that less-than-beautiful grub
0:55:07 > 0:55:11that Frank found in the log, a harlequin beetle.
0:55:14 > 0:55:17It's a female harlequin beetle. BUZZING
0:55:18 > 0:55:20You hear the noise she's making?
0:55:24 > 0:55:26It's a warning sound.
0:55:26 > 0:55:30She's got spines at the side of the thorax,
0:55:30 > 0:55:32spines on the humeri.
0:55:32 > 0:55:36They come together, and if I put my finger in there, she'd poke me.
0:55:36 > 0:55:38Even spines down here on the back side,
0:55:38 > 0:55:44and the legs, like all of these insects, have hooks on 'em sharp enough
0:55:44 > 0:55:48that just to touch your flesh they're immediately hooked in.
0:55:48 > 0:55:51See it pulling me out there? She'd be a tough one.
0:55:51 > 0:55:58The bigger the beetle, the more tempting to predators, and so the tougher it needs to be.
0:55:58 > 0:56:01What the heck was that?
0:56:01 > 0:56:02- Titanus!- Titanus!
0:56:02 > 0:56:04Oh, look at this!
0:56:04 > 0:56:07- Look at this!- Pretty good-sized one.
0:56:07 > 0:56:11Yeah, he's a pretty good size. You gonna try to move that rock?
0:56:11 > 0:56:12Hello!
0:56:12 > 0:56:15Let's not go anywhere, shall we?
0:56:15 > 0:56:17What an incredible beetle.
0:56:18 > 0:56:20He's very strong.
0:56:22 > 0:56:24You can feel his body temperature - he's hot.
0:56:24 > 0:56:27Well hotter than the outside temperature.
0:56:27 > 0:56:29He's ripping my flesh!
0:56:32 > 0:56:36There's something primeval about the movements of this thing.
0:56:36 > 0:56:38Those jaws going...
0:56:41 > 0:56:44When so little is known about the titan,
0:56:44 > 0:56:46just to record the sheer size of it,
0:56:46 > 0:56:52what time it comes out, how warm it is, how strong it is, makes it all worthwhile.
0:56:53 > 0:56:54That is a spectacular beetle.
0:56:55 > 0:56:58All I can say right now is...
0:56:59 > 0:57:01# Da-da-da! Da-da da!#
0:57:01 > 0:57:02Titanus!
0:57:04 > 0:57:09One day, Frank will find his giant larva, and each new encounter will
0:57:09 > 0:57:14help build up a complete picture of the world's largest insect.
0:57:14 > 0:57:17Thanks to people like Frank, we are getting ever closer
0:57:17 > 0:57:21to an understanding of the creatures of the undergrowth.
0:57:25 > 0:57:31But every night on Frank's sheet there are about 500 different kinds of invertebrate.
0:57:33 > 0:57:38And that's just one sheet, in one clearing, in one patch of forest.
0:57:42 > 0:57:49It's thought that there are ten million species of land-living invertebrates on the planet.
0:57:49 > 0:57:53Of those, nine million are yet to be discovered.