0:00:03 > 0:00:07Insects. They buzz. They bite.
0:00:07 > 0:00:10They bother us.
0:00:10 > 0:00:14But for each one of us, there are 200 million of them.
0:00:16 > 0:00:20They've conquered nearly every corner of our planet.
0:00:20 > 0:00:22This is a bug's world.
0:00:25 > 0:00:28So, what's the secret of their success?
0:00:29 > 0:00:30I'm James Logan.
0:00:30 > 0:00:33And I'm Brendan Dunphy.
0:00:33 > 0:00:38We're both entomologists - and we think that to understand insects,
0:00:38 > 0:00:40you have to get inside them.
0:00:43 > 0:00:48So to unlock their secrets, we've built our own dissection lab,
0:00:48 > 0:00:51where we're going to take insects apart bit by bit
0:00:51 > 0:00:55to reveal a remarkable hidden world.
0:00:55 > 0:01:00Body parts so strange they look almost alien.
0:01:00 > 0:01:04Incredible pieces of natural engineering that surpass
0:01:04 > 0:01:06the best inventions of humans.
0:01:06 > 0:01:08There we go. Oh, fantastic!
0:01:08 > 0:01:13We'll explore the insect body in ways even we've never tried before.
0:01:13 > 0:01:15Oh! Oh... Ho-ho!
0:01:17 > 0:01:19And we'll meet the scientists
0:01:19 > 0:01:23who are making new discoveries about how insects work.
0:01:23 > 0:01:27This is one of the most amazing things I've ever done.
0:01:27 > 0:01:31Taking bug bodies apart will at times be challenging.
0:01:31 > 0:01:34Smell that. That doesn't smell good.
0:01:34 > 0:01:36Perhaps even gruesome.
0:01:36 > 0:01:40But it will be a revelation - as we discover
0:01:40 > 0:01:44how their extraordinary anatomy has helped them conquer our planet,
0:01:44 > 0:01:47and what we can learn from insects.
0:01:57 > 0:01:59This is our dissection table,
0:01:59 > 0:02:04where we're going to be taking apart our bug bodies systematically.
0:02:04 > 0:02:08In a series of dissections, we're going to use these tools,
0:02:08 > 0:02:10and state-of-the-art microscopes,
0:02:10 > 0:02:14to reveal the secrets of insects in incredible detail.
0:02:14 > 0:02:19And we have some amazing specimens here - living ones,
0:02:19 > 0:02:21as well as lab collections that have been put together with
0:02:21 > 0:02:24painstaking work over decades.
0:02:26 > 0:02:30To begin to understand why they're so successful,
0:02:30 > 0:02:32what we want to do first is investigate just how
0:02:32 > 0:02:35different their fundamental body plan is from ours.
0:02:44 > 0:02:46Now, you might think about this cockroach as a pest in your home.
0:02:46 > 0:02:49And you'd be right. But to me and Brendan,
0:02:49 > 0:02:51this is an incredibly good specimen of an insect.
0:02:51 > 0:02:55We're going to use this microscope, which is going to blow up the image,
0:02:55 > 0:02:58and let you see what we're doing. And the place we're going to start
0:02:58 > 0:03:01is here, the exoskeleton.
0:03:01 > 0:03:04And this external skeleton, which supports and protects the body,
0:03:04 > 0:03:07is common to all insects.
0:03:07 > 0:03:10And it's also one of the major differences between them and us.
0:03:10 > 0:03:12We have a skeleton on the inside of our body,
0:03:12 > 0:03:15but they wear theirs on the outside of their bodies.
0:03:15 > 0:03:16That's right.
0:03:16 > 0:03:19And when you stand on a cockroach and it makes that crunching sound,
0:03:19 > 0:03:22that's actually the exoskeleton breaking.
0:03:22 > 0:03:25So the first thing I'm going to do is I'm going to take this pin,
0:03:25 > 0:03:29which is incredibly fine but very strong, and get it through the neck.
0:03:29 > 0:03:31That's a nice anchor point.
0:03:31 > 0:03:33It is. Just get a couple of pins in there.
0:03:33 > 0:03:36- You can hear it crunch. - It did crunch when I put it through.
0:03:36 > 0:03:40It's actually quite tough to get the pins through.
0:03:40 > 0:03:44So I'm now going to chop off the legs.
0:03:44 > 0:03:48And obviously they've got six legs, because they're insects.
0:03:48 > 0:03:51- There goes six.- There you go. And I'm going to use some scissors.
0:03:51 > 0:03:53I've got these very fine scissors but they're extremely sharp.
0:03:53 > 0:03:56They have to be extremely sharp to get through the cuticle,
0:03:56 > 0:03:58which is very hard.
0:03:58 > 0:04:00So let's give this a go.
0:04:04 > 0:04:08All bugs share a basic body plan,
0:04:08 > 0:04:10a head,
0:04:10 > 0:04:13a thorax - that's the middle section where you find the legs and wings -
0:04:13 > 0:04:15and an abdomen.
0:04:16 > 0:04:20Covering it all is a layer called the cuticle,
0:04:20 > 0:04:23the outer part of the exoskeleton.
0:04:23 > 0:04:25It coats the whole insect body...
0:04:26 > 0:04:31..from the tips of the antennae to the end of every wing, leg and claw.
0:04:38 > 0:04:40I have to be quite careful when I'm doing this,
0:04:40 > 0:04:43because obviously I want to preserve the organs inside,
0:04:43 > 0:04:47that we're going to have a look at in a second.
0:04:47 > 0:04:49I'm about to snap through the thorax,
0:04:49 > 0:04:52which is probably one of the thicker parts of the exoskeleton. Listen.
0:04:52 > 0:04:54- You hear that crack?- I can.
0:04:54 > 0:04:56It's incredibly thick and tough in this part.
0:04:56 > 0:05:00Right, I'm going to try and pull the cuticle from the bottom
0:05:00 > 0:05:03of the insect, which is facing upwards, off.
0:05:03 > 0:05:07And in theory - in theory - this should come off in a one-er.
0:05:07 > 0:05:10This is the bit I love, this is fantastic.
0:05:10 > 0:05:12- When you get this open... - This is the reveal.
0:05:12 > 0:05:15..it reveals a hidden world, it really is a hidden world, I think.
0:05:15 > 0:05:16I think it's brilliant.
0:05:18 > 0:05:20OK, here we go.
0:05:21 > 0:05:23- Wow.- Check that out.
0:05:23 > 0:05:25You know, it never ceases to amaze me,
0:05:25 > 0:05:29to look inside of an insect body when you dissect it.
0:05:29 > 0:05:32I know. But the thing is, when you get to the inside,
0:05:32 > 0:05:34the first thing you see is all this sort of white mush,
0:05:34 > 0:05:37which is what you see when you stand on them basically, isn't it?
0:05:37 > 0:05:39And we don't see any bones.
0:05:39 > 0:05:42The skeleton of the insect is on the outside.
0:05:42 > 0:05:45That's right, so the body is surrounded by this cuticle,
0:05:45 > 0:05:48which basically covers the entire outside of the body.
0:05:48 > 0:05:49But it even gets inside as well,
0:05:49 > 0:05:52extending inwards as attachment points for muscles.
0:05:59 > 0:06:03The cuticle acts as both a skin and a skeleton.
0:06:03 > 0:06:07It's like an armoured coating that also supports the bug's bodyweight.
0:06:09 > 0:06:12Having an exoskeleton means insects have to
0:06:12 > 0:06:14shed their skins as they grow.
0:06:18 > 0:06:21But the rigid coating also allows them to construct some of the most
0:06:21 > 0:06:24complex and intricate body shapes in nature.
0:06:33 > 0:06:35Lightweight, waterproof,
0:06:35 > 0:06:37tough yet flexible...
0:06:38 > 0:06:41..the cuticle is one of nature's wonder materials.
0:06:44 > 0:06:46It's allowed insects to live
0:06:46 > 0:06:49and thrive where few other animals can survive.
0:06:55 > 0:06:58And to take a closer look at it,
0:06:58 > 0:07:00we're going to use this -
0:07:00 > 0:07:03the scanning electron microscope.
0:07:03 > 0:07:08This allows us to see insects at up to 60,000 times their actual size.
0:07:10 > 0:07:12So here I have a mosquito sample.
0:07:12 > 0:07:15And mosquitoes are my favourite insects.
0:07:15 > 0:07:17So I'm going to put this sample in.
0:07:17 > 0:07:20- Hey, James.- Yeah? - You should check this out.
0:07:20 > 0:07:23OK. What've you got?
0:07:24 > 0:07:27Ah, nice. Mosquito?
0:07:27 > 0:07:29Yup. Let's change the resolution.
0:07:29 > 0:07:31OK, so that's scanning down now and just giving us
0:07:31 > 0:07:32a bit more resolution.
0:07:36 > 0:07:40Mosquitoes might seem tiny and squashable at our scale.
0:07:40 > 0:07:44But magnified hundreds of times we can see the tough exoskeleton
0:07:44 > 0:07:46surrounding their body.
0:07:47 > 0:07:51What looks smooth to the naked eye becomes incredibly complex.
0:07:53 > 0:07:58Here on the wing, we discover microscopic hair-like structures.
0:07:58 > 0:08:00These can sense tiny gusts of wind
0:08:00 > 0:08:04and help guide the insect through turbulent air.
0:08:04 > 0:08:07If you look at any insect at this scale - the cuticle becomes
0:08:07 > 0:08:08a dramatic landscape.
0:08:14 > 0:08:17These are scales on a butterfly's wing.
0:08:17 > 0:08:20Magnifying closer and closer,
0:08:20 > 0:08:22we see that each scale is lined with tiny ridges.
0:08:25 > 0:08:27These interact with the light that strikes them,
0:08:27 > 0:08:31giving the wings their vibrant shifting colours.
0:08:39 > 0:08:43The insect exoskeleton is a marvel of animal engineering.
0:08:49 > 0:08:53So the exoskeleton is far more than it first appears -
0:08:53 > 0:08:55it's an incredibly sophisticated
0:08:55 > 0:08:57and versatile piece of the insect's anatomy.
0:08:57 > 0:09:00And now that we've peeled away that outer shell,
0:09:00 > 0:09:02we can take a look deeper inside.
0:09:04 > 0:09:06As we've seen, the first thing you find
0:09:06 > 0:09:09when you open up an insect is a kind of white mush.
0:09:09 > 0:09:11It's known as "fat body".
0:09:12 > 0:09:15So, what I've been doing is teasing away all the fat body.
0:09:15 > 0:09:17There's a ton of it here.
0:09:17 > 0:09:20You notice this clump that I've been accumulating.
0:09:20 > 0:09:23The fat body is like an all-in-one storage tissue -
0:09:23 > 0:09:27holding protein, fats and other nutrients.
0:09:28 > 0:09:31But to reach the vital body systems that power the insect,
0:09:31 > 0:09:33we're going to clear it away.
0:09:33 > 0:09:36Now we can delve into the abdomen and see what else we can find.
0:09:36 > 0:09:39Now, the next system that we come upon is a really interesting
0:09:39 > 0:09:42system in insects. It's the respiratory system.
0:09:42 > 0:09:44And it's quite a strange system, isn't it?
0:09:44 > 0:09:46- Very.- I mean they don't have a heart as we know it.
0:09:46 > 0:09:49They don't have a heart that pumps oxygen round the body,
0:09:49 > 0:09:52and they don't have a circulatory system that feeds
0:09:52 > 0:09:53the organs with oxygen, either.
0:09:53 > 0:09:56Instead, they have tiny holes along the side of their abdomen
0:09:56 > 0:09:57called spiracles.
0:09:57 > 0:10:01And oxygen and air enters through these spiracles
0:10:01 > 0:10:05into a large network of tubes that extend throughout the body
0:10:05 > 0:10:08and surround the vital organs, feeding them with oxygen.
0:10:12 > 0:10:16Insects breathe in a very different way from us.
0:10:16 > 0:10:20Air entering the body passes into tubes called tracheae.
0:10:20 > 0:10:24These divide into smaller and smaller branches,
0:10:24 > 0:10:28a network that feeds oxygen to the innermost parts of the insect body.
0:10:29 > 0:10:33So it's a direct oxygen delivery system, really brilliant.
0:10:33 > 0:10:36And here, you can see how vast that network is.
0:10:36 > 0:10:40This is just one forceps-full of tracheae.
0:10:40 > 0:10:42- It's quite incredible. - Branching out like a tree.
0:10:42 > 0:10:45- Yeah, or lightning. It's quite beautiful.- It is, very much.
0:10:56 > 0:10:59This efficient breathing system is one of the major keys to
0:10:59 > 0:11:01insect success. But it's also a clue to
0:11:01 > 0:11:05one of the greatest mysteries of the insect world.
0:11:05 > 0:11:06Why are they so small?
0:11:09 > 0:11:12- VOICEOVER:- 'I tell you, gentlemen, science is agreed
0:11:12 > 0:11:14'that unless something is done, and done quickly,'
0:11:14 > 0:11:17man, as the dominant species of life on Earth,
0:11:17 > 0:11:20will be extinct within a year.
0:11:23 > 0:11:28Giant insects striking terror into us humans - a favourite of the B-movies.
0:11:30 > 0:11:33But in reality, even the largest insects on the planet
0:11:33 > 0:11:35are only about the size of a clenched fist.
0:11:37 > 0:11:39Why don't they grow any bigger?
0:11:39 > 0:11:42Why don't B-movie monsters exist in the real world?
0:11:47 > 0:11:49At Arizona State University,
0:11:49 > 0:11:52a team of scientists are trying to find out.
0:11:52 > 0:11:56And they have a theory that it's all to do with the way insects breathe.
0:11:58 > 0:12:01To investigate, they're taking some of the biggest
0:12:01 > 0:12:05insects on Earth - beetles - and studying their breathing system.
0:12:06 > 0:12:10But first they have to persuade them to do some serious exercise.
0:12:10 > 0:12:12- Jaco?- I'm Brendan.
0:12:12 > 0:12:13- How are you?- Good.
0:12:13 > 0:12:15So what have we got here?
0:12:15 > 0:12:16So, here I have a beetle
0:12:16 > 0:12:18set up with two electrodes
0:12:18 > 0:12:19implanted in the brain.
0:12:19 > 0:12:21And then through these really thin,
0:12:21 > 0:12:22silver wires we can deliver
0:12:22 > 0:12:26a pre-defined electrical signal across the brain of the beetle.
0:12:26 > 0:12:29And that will then stimulate the beetle to fly.
0:12:30 > 0:12:34Although it may look a bit extreme, Jaco assures me
0:12:34 > 0:12:36it doesn't harm them.
0:12:36 > 0:12:39This setup reminds me of human exercise studies in which you
0:12:39 > 0:12:42put a person on a treadmill and measure metabolic activity.
0:12:42 > 0:12:45- That's what we're doing here, but with insects.- Yes.
0:12:45 > 0:12:49This is basically oxygen, or insect, exercise physiology.
0:12:49 > 0:12:52But with humans, when you want someone to exercise you can
0:12:52 > 0:12:56say, "OK, please, run. OK, run faster, run slower."
0:12:56 > 0:13:00I can tell the beetle, "OK, please, fly. OK, please, fly,"
0:13:00 > 0:13:02but it doesn't really work.
0:13:02 > 0:13:04I'd love to see this in action.
0:13:04 > 0:13:05OK, let's give it a buzz.
0:13:11 > 0:13:17Aah, wow! Wow, look at how fast it's flapping.
0:13:17 > 0:13:21Yeah. That's 70-75 wing beats per second.
0:13:21 > 0:13:23If you hold your hands there,
0:13:23 > 0:13:26you can actually feel the down force of wind.
0:13:26 > 0:13:28Ah, you can feel the power like that, can't you?
0:13:28 > 0:13:31- Yeah, you can definitely feel it. - Wow.
0:13:35 > 0:13:41During this strenuous exercise, Jaco measures the beetle's oxygen intake.
0:13:41 > 0:13:44He wants to find out how its air tubes cope with
0:13:44 > 0:13:47the insect equivalent of running a marathon.
0:13:47 > 0:13:50The beetle's breathing system is very good at getting the air
0:13:50 > 0:13:53to where it is needed.
0:13:53 > 0:13:56But the trade-off is a lot of internal tubing.
0:13:56 > 0:13:59And the bigger you get, the bigger tubes you need.
0:13:59 > 0:14:02Especially for the bigger beetles, when you open up one of these
0:14:02 > 0:14:05beetles, they're as big as... you can drive a bus through it.
0:14:08 > 0:14:12The team have discovered what they think is a vital clue to
0:14:12 > 0:14:14the small size of insects.
0:14:14 > 0:14:16Scanning insects of different sizes,
0:14:16 > 0:14:20they reveal the intricate web of breathing tubes inside.
0:14:22 > 0:14:25As insects grow larger, they require more tubes.
0:14:28 > 0:14:31The team noticed that the larger the insect,
0:14:31 > 0:14:34the higher the percentage of body space taken up by these tubes.
0:14:38 > 0:14:42Any bigger than a large beetle, and the theory is an insect would need
0:14:42 > 0:14:47so much tubing that there wouldn't be space for other vital organs.
0:14:48 > 0:14:52It's a compelling idea. But I'm left with a new mystery.
0:14:53 > 0:14:55Because if we look far enough back in history,
0:14:55 > 0:14:57we do find much bigger insects.
0:15:00 > 0:15:03Fossil records show that when dinosaurs roamed the Earth,
0:15:03 > 0:15:08dragonfly-like insects with wingspans nearly a metre long soared the skies.
0:15:10 > 0:15:13So how was this possible?
0:15:13 > 0:15:17Why didn't they suffer from the tubing problem?
0:15:17 > 0:15:21Down the corridor, another researcher may have found the answer.
0:15:22 > 0:15:24- John.- Hey. How are you?
0:15:24 > 0:15:29Doing good, how about you? So what's going on here?
0:15:29 > 0:15:32Here we have Madagascar hissing cockroaches,
0:15:32 > 0:15:35which we're rearing under different oxygen concentrations.
0:15:35 > 0:15:39Hyperoxia here being higher than today's levels of oxygen,
0:15:39 > 0:15:43and hypoxia being below today's levels of oxygen.
0:15:43 > 0:15:46John is testing how big insects can grow with different
0:15:46 > 0:15:49amounts of oxygen in the air they breathe.
0:15:49 > 0:15:52Over the last 300-400 million years,
0:15:52 > 0:15:55the amount of oxygen in the atmosphere has varied quite a bit.
0:15:55 > 0:15:59It's gone up as high as 30% and down as low as 12%.
0:15:59 > 0:16:02- And what is it right now? - Right now, it's 21%.
0:16:02 > 0:16:05So will we be able to see the effect that oxygen has on insect
0:16:05 > 0:16:06body size in here?
0:16:06 > 0:16:10Yeah. In fact we have some dragonflies right here.
0:16:10 > 0:16:14And we can see that, here's a dragonfly that's been reared
0:16:14 > 0:16:16under today's oxygen levels, so 21%.
0:16:16 > 0:16:20And here's a dragonfly that's been reared under higher oxygen
0:16:20 > 0:16:23levels, of 30%. Which is the highest value that we see in the past.
0:16:23 > 0:16:25You can see even in a single generation
0:16:25 > 0:16:27- you can get a visible effect on body size.- Wow!
0:16:27 > 0:16:31You can see this dragonfly is almost 20-25% longer than
0:16:31 > 0:16:33the dragonfly reared in normal oxygen levels.
0:16:33 > 0:16:36So it's amazing to think if that's a single dragonfly's lifetime,
0:16:36 > 0:16:39what can happen over the course of hundreds of millions of years.
0:16:39 > 0:16:42That's right, and in the geologic past,
0:16:42 > 0:16:45we had giant dragonflies with the 70cm wingspans.
0:16:45 > 0:16:48There's no question that changing atmospheric oxygen levels
0:16:48 > 0:16:51over geologic time would have been influencing their development,
0:16:51 > 0:16:53their size and their physiology.
0:16:53 > 0:16:58Those ancient dragonflies may have been able to grow so big
0:16:58 > 0:17:01because there was more oxygen in the air.
0:17:01 > 0:17:04So the insects were less constrained by the problem of tubes.
0:17:06 > 0:17:10At today's lower levels of oxygen, insects are destined to stay small.
0:17:12 > 0:17:15Paradoxically, this has turned out to be an advantage.
0:17:16 > 0:17:19The smaller you are, the more nooks
0:17:19 > 0:17:22and crannies you can find to live in, and hide from predators.
0:17:23 > 0:17:27Staying small has helped bugs to dominate our planet...
0:17:32 > 0:17:35..while giant insects remain in the realm of science fiction.
0:17:45 > 0:17:48Now that we've removed most of the breathing system,
0:17:48 > 0:17:52we can carry on with our dissection and discover the next hidden
0:17:52 > 0:17:55wonder of the bug body - the digestive system.
0:17:57 > 0:18:00To get a better look, we need to take it out and unravel it.
0:18:03 > 0:18:06And so far it has just been coiled up inside the body,
0:18:06 > 0:18:08but we've removed it to one side.
0:18:08 > 0:18:14So you can see actually how long this digestive system actually is.
0:18:14 > 0:18:16The thing that I find remarkable about insects is that it's
0:18:16 > 0:18:19not too dissimilar to our own digestive system.
0:18:19 > 0:18:20It is pretty much the same thing.
0:18:20 > 0:18:23It's a tube that runs the length of the whole body from the mouth
0:18:23 > 0:18:25to the anus. And its job is to
0:18:25 > 0:18:28extract nourishment from food and get rid of the waste.
0:18:29 > 0:18:34The insect digestive system is simple but remarkably efficient.
0:18:35 > 0:18:38Bugs can take nutrition from pretty much anything
0:18:38 > 0:18:42in the natural world - from tree bark to rotting flesh.
0:18:46 > 0:18:48Nutrients pass through the tube wall,
0:18:48 > 0:18:50either straight into tissues that need them,
0:18:50 > 0:18:52or into the fat body,
0:18:52 > 0:18:54where they're stored for use later.
0:18:57 > 0:18:59Along the tube are a set of organs
0:18:59 > 0:19:00for breaking down food
0:19:00 > 0:19:03and collecting waste.
0:19:03 > 0:19:06One that insects have that we don't
0:19:06 > 0:19:08is a crop - an expandable sack
0:19:08 > 0:19:12that stores food before it gets to the stomach to be digested.
0:19:12 > 0:19:13Handy if you're the type of insect
0:19:13 > 0:19:16that might only find food every few days.
0:19:18 > 0:19:20So there's the crop.
0:19:20 > 0:19:22And you see it covered with the air tubes.
0:19:22 > 0:19:25And in fact, some of the digestion can even start here.
0:19:25 > 0:19:27Yeah, so there's some enzymes that are produced in
0:19:27 > 0:19:29the digestive system that help to digest the food.
0:19:29 > 0:19:32So let's see what the cockroach has been eating, huh?
0:19:32 > 0:19:35It's not every day you get to look inside a cockroach's guts.
0:19:35 > 0:19:38Look away now if you're squeamish.
0:19:38 > 0:19:40I'm going to stick the digestive system back inside,
0:19:40 > 0:19:41because when I cut this open
0:19:41 > 0:19:45- it's probably going to make a bit of a mess.- Right.- Here we go.
0:19:45 > 0:19:48I'm just going to rip it apart with these forceps. There we go.
0:19:48 > 0:19:50Well, there we are. Wow.
0:19:50 > 0:19:53I can smell that. That doesn't smell good.
0:19:53 > 0:19:54What has this cockroach been eating?
0:19:54 > 0:19:58- It looks like carrots.- Doesn't smell like carrots.- Or baby food.
0:19:58 > 0:19:59Smells like dog food.
0:19:59 > 0:20:02Yeah, you can really tell that it's partially digested.
0:20:02 > 0:20:05It's partly solid yet kind of this slimy consistency.
0:20:05 > 0:20:08Yeah. It's not particularly nice, is it?
0:20:08 > 0:20:10- No, it's not.- Could be anything.
0:20:10 > 0:20:13They eat anything organic, whether it's plant or animal tissue,
0:20:13 > 0:20:15and whether it's living or dead.
0:20:15 > 0:20:18and that's one of the reasons that they're so successful as insects,
0:20:18 > 0:20:22- is that they can find food virtually anywhere on the planet.- Absolutely.
0:20:26 > 0:20:30Cockroaches have survived largely unchanged for 300 million years
0:20:30 > 0:20:33partly thanks to their unfussy diet.
0:20:35 > 0:20:38But far richer food sources have appeared
0:20:38 > 0:20:41since these omnivores first crawled the Earth.
0:20:41 > 0:20:45And many other insects have adopted very specialised diets,
0:20:45 > 0:20:49requiring some clever adjustments to their digestive system.
0:20:49 > 0:20:52And to show this, I'm going to look at an insect which, like Brendan,
0:20:52 > 0:20:56I study in my lab - the mosquito.
0:20:56 > 0:20:59And it has a specialised way of feeding on blood -
0:20:59 > 0:21:01in this case, mine.
0:21:01 > 0:21:05So we've got in this tube a very hungry mosquito.
0:21:05 > 0:21:07It's a female, because only the females bite.
0:21:07 > 0:21:09And I'm going to place this mosquito on my arm.
0:21:12 > 0:21:14There we go.
0:21:15 > 0:21:18She's attracted to the chemicals given off in my body odour,
0:21:18 > 0:21:19but also attracted to the heat
0:21:19 > 0:21:22and the moisture given off by my skin as well.
0:21:22 > 0:21:24And now it's feeding, it's not going anywhere.
0:21:24 > 0:21:28And what I'm going to do is use this special camera to actually
0:21:28 > 0:21:31show you the mosquito feeding.
0:21:34 > 0:21:38Her proboscis is now deep inside my skin, sucking on my blood.
0:21:40 > 0:21:44Most mosquitoes survive on nectar, but to make their eggs,
0:21:44 > 0:21:48these females need the richer nutrients in my red blood cells.
0:21:49 > 0:21:51As she takes in my blood,
0:21:51 > 0:21:53her digestive system gets to work straight away.
0:21:55 > 0:21:56It keeps the red blood cells,
0:21:56 > 0:21:59and discards almost everything else as waste.
0:22:00 > 0:22:03Even in the few minutes she's been feeding,
0:22:03 > 0:22:06a drop of watery liquid oozes out of her back end.
0:22:10 > 0:22:13But it's what's happening inside the mosquito that I want to see.
0:22:19 > 0:22:21As she feeds, her stomach creates
0:22:21 > 0:22:24a special membrane to contain the blood,
0:22:24 > 0:22:27keeping it separate from any other food inside her.
0:22:30 > 0:22:33This digestive system is very delicate.
0:22:33 > 0:22:34But I'm going to try
0:22:34 > 0:22:37and separate it from the rest of the body without bursting it.
0:22:37 > 0:22:41OK, so here's our mosquito, which is nice and blood-fed.
0:22:41 > 0:22:44It's surreal to think that you're actually going to
0:22:44 > 0:22:47look at your own life fluid inside of her digestive system.
0:22:47 > 0:22:49I know, it's something I've never done before.
0:22:49 > 0:22:52We're both mosquito specialists, and neither of us have ever done this.
0:22:52 > 0:22:55And I believe it's very difficult. So we'll give it a go anyway.
0:22:56 > 0:22:59The next thing I'm going to do is chop its head off
0:22:59 > 0:23:02because we'll pull its digestive system out the back end.
0:23:02 > 0:23:04So it needs to be detached at the front end.
0:23:05 > 0:23:08There we go. So you can see that I've removed the head,
0:23:08 > 0:23:10and you can see the blood in the abdomen there.
0:23:10 > 0:23:14- That is my blood. - That is your blood in there.
0:23:14 > 0:23:16Right.
0:23:16 > 0:23:17There you have it.
0:23:17 > 0:23:21So now you're just giving it a tug and seeing if we can pull it out.
0:23:27 > 0:23:29OK, something's coming out.
0:23:29 > 0:23:31Ah, check it out!
0:23:31 > 0:23:33- There it is.- No way. - Look at that.
0:23:33 > 0:23:36I cannot believe we've actually just done that.
0:23:36 > 0:23:38First time, wow. That was amazing technique, by the way,
0:23:38 > 0:23:40- so kudos to you.- Thank you.
0:23:40 > 0:23:44Shall we take a look closer in at that? That blood sac.
0:23:46 > 0:23:47See whether we can...
0:23:47 > 0:23:49- Nice.- I mean, it really just looks like
0:23:49 > 0:23:52we're looking at a blob of blood on the slide, doesn't it?
0:23:52 > 0:23:54- It really does.- But it's actually surrounded by
0:23:54 > 0:23:58a peritrophic membrane, which sort of contains the blood,
0:23:58 > 0:24:00but also contains any sort of viruses
0:24:00 > 0:24:03and bacteria and stops them from getting into the mosquito's body.
0:24:03 > 0:24:06But of course some of those things have evolved to get through it.
0:24:06 > 0:24:09Like malaria parasites, for example.
0:24:09 > 0:24:13So mosquitoes put a lot of time and investment in digesting that blood.
0:24:13 > 0:24:15All for reproduction.
0:24:21 > 0:24:26The digestive system is a huge factor in insects' global success.
0:24:26 > 0:24:28Little more than a simple tube,
0:24:28 > 0:24:32it can make a meal out of pretty much anything.
0:24:32 > 0:24:36But to truly appreciate the simple efficiency of insect bodies,
0:24:36 > 0:24:39you need to look at the next vital body system
0:24:39 > 0:24:41we uncover as we continue our dissection.
0:24:51 > 0:24:54So notice now we've got a new cockroach.
0:24:54 > 0:24:57Because basically we've gone right the way through the anatomy
0:24:57 > 0:24:59to the other side.
0:24:59 > 0:25:00And the insect's nervous system,
0:25:00 > 0:25:03the central nervous system runs down the belly of the insect.
0:25:03 > 0:25:06So we have to go in from the back and find it that way.
0:25:06 > 0:25:09- We're going to start snipping again. - We're going to start snipping again.
0:25:09 > 0:25:11I don't have to be as careful now
0:25:11 > 0:25:13because we've already seen some of the organs.
0:25:13 > 0:25:17- Because we know what we're going for.- Yep. And we know where it is.
0:25:19 > 0:25:23The nervous system extends from the head right the way down to
0:25:23 > 0:25:25the bottom end of the insect.
0:25:25 > 0:25:26So we need to see the whole thing here.
0:25:28 > 0:25:31We're aiming for the insect's information highway.
0:25:31 > 0:25:34The nervous system gathers the input from the senses
0:25:34 > 0:25:38and controls all the body's vital functions and movement.
0:25:38 > 0:25:41Now, in us we have a very complex organ in our central nervous system,
0:25:41 > 0:25:44the brain, to take care of this.
0:25:44 > 0:25:46Well, what does the insect have? That is what we're after now.
0:25:48 > 0:25:51It's quite amazing. Insects do have a brain, a very simple brain.
0:25:51 > 0:25:54But this is responsible for gathering and processing all
0:25:54 > 0:25:57the information from the sensory organs, so the massive big eyes,
0:25:57 > 0:26:02and the antennae which is their nose, this is where it is fed into.
0:26:02 > 0:26:07So we can actually see now inside the head there.
0:26:07 > 0:26:09It just looks like a mass of tissue,
0:26:09 > 0:26:12but you can actually see the nerve cord which is running right
0:26:12 > 0:26:15the way up the body, right from the bottom of the abdomen,
0:26:15 > 0:26:20right the way up through the thorax and into the head to this brain.
0:26:23 > 0:26:25Even if insects were the size of humans,
0:26:25 > 0:26:28their brains would still be much smaller than ours.
0:26:29 > 0:26:32Unlike us, they rely much less on their brains to carry out
0:26:32 > 0:26:37vital functions like breathing, moving and eating.
0:26:37 > 0:26:41So, what do they use instead? That's what we're looking for next.
0:26:42 > 0:26:45Now I'm actually having to be quite careful at this point
0:26:45 > 0:26:48because we are down now into the very belly of the insect
0:26:48 > 0:26:50right where the nervous system is.
0:26:50 > 0:26:55You can see this pair of nerve cords that run the entire
0:26:55 > 0:26:59length of the body here.
0:26:59 > 0:27:02And what you can see there is a great example of a ganglion,
0:27:02 > 0:27:03which is a sort of nerve centre.
0:27:06 > 0:27:09There are several of these bundles of nerve cells,
0:27:09 > 0:27:12called ganglia, dotted around the insect's body.
0:27:14 > 0:27:15Being closer to the organs
0:27:15 > 0:27:17and limbs that they control
0:27:17 > 0:27:18means that signals have to travel
0:27:18 > 0:27:20over a much shorter distance than
0:27:20 > 0:27:21going to the brain and back.
0:27:24 > 0:27:26So there are actually nerve centres
0:27:26 > 0:27:28not just in the head but throughout the entire body.
0:27:28 > 0:27:31You sort of have to think of an insect as having its brain
0:27:31 > 0:27:34almost all the way down its body.
0:27:34 > 0:27:36As opposed to just in one section in the head.
0:27:36 > 0:27:38To be dispersed in many different areas.
0:27:38 > 0:27:40And these are responsible for
0:27:40 > 0:27:42controlling the legs in this species.
0:27:42 > 0:27:44With other insects that fly, for example,
0:27:44 > 0:27:47they'd be involved in helping to control the wings.
0:27:51 > 0:27:53It's amazing to think that this cockroach could keep
0:27:53 > 0:27:55moving for weeks without its head
0:27:55 > 0:28:00because its body is controlled by nerve centres outside the brain.
0:28:00 > 0:28:04It would die only because it couldn't eat and drink.
0:28:12 > 0:28:16So we've seen that insects have a set of incredibly efficient
0:28:16 > 0:28:20systems for breathing, digestion and body control.
0:28:22 > 0:28:26But these systems, in some form, are also found in
0:28:26 > 0:28:29almost every other animal on Earth.
0:28:31 > 0:28:34So what else about insects has allowed them to become
0:28:34 > 0:28:35so successful?
0:28:37 > 0:28:39To answer that, we need to look closer
0:28:39 > 0:28:40at what they've been able to bolt on
0:28:40 > 0:28:42to that basic core.
0:28:44 > 0:28:47The specialised tools that have given them the edge.
0:28:50 > 0:28:53And we'll start with some of the most impressive.
0:29:03 > 0:29:07Insects have evolved an incredible array of mouthparts -
0:29:07 > 0:29:11designed to feed on everything from fruit to foliage to flesh.
0:29:14 > 0:29:16The longest mouthparts in the insect world
0:29:16 > 0:29:18are the sucking tubes
0:29:18 > 0:29:20of butterflies and moths,
0:29:20 > 0:29:22but it takes a bit of gentle persuasion to see them.
0:29:22 > 0:29:26There you go. It's almost doing it for me.
0:29:26 > 0:29:28It's like I'm tickling its mouthpart
0:29:28 > 0:29:30and it's extending its tongue out for us. What a performer!
0:29:30 > 0:29:33It's nice to see at this level, close up, how coiled it is.
0:29:33 > 0:29:35Brilliant, yeah.
0:29:36 > 0:29:40It is a tube which is used to get into plants to get the nectar out.
0:29:40 > 0:29:45I tell you, when I look at mouth structures,
0:29:45 > 0:29:47that's when I really realise that the insect exoskeleton
0:29:47 > 0:29:51is like a set of building blocks of all various shapes and sizes.
0:29:51 > 0:29:55- Absolutely.- And you see them being used for specific functions.
0:29:55 > 0:29:58Most insects have a basic set of biting and chewing tools.
0:30:00 > 0:30:04But from here evolution has run wild.
0:30:04 > 0:30:07As well as the long sucking tube of the butterfly,
0:30:07 > 0:30:12some mouthparts sponge up food, while others pierce
0:30:12 > 0:30:14the skin of plants or animals then suck out liquid contents.
0:30:17 > 0:30:20And mouthparts aren't always just feeding tools.
0:30:22 > 0:30:24Some insects have added an extra function.
0:30:27 > 0:30:31Cutting and slicing jaws have become powerful weapons that inflict
0:30:31 > 0:30:35painful bites on their enemies.
0:30:35 > 0:30:39Some of the most fearsome jaws in the insect world belong to ants.
0:30:39 > 0:30:44So, what we've got here is a lovely big soldier ant.
0:30:44 > 0:30:47Let's check out the action of these mandibles, shall we?
0:30:49 > 0:30:51- Wow. Put it under the scope, let's see it under the scope!- Agh!
0:30:51 > 0:30:53Argh! Wow!
0:30:53 > 0:30:55- How does it feel? - It is kind of painful!
0:30:57 > 0:31:00Just kind of? Look at that!
0:31:00 > 0:31:02The strength in those mandibles is unbelievable!
0:31:02 > 0:31:05Look at that. It's moving its abdomen up and down, too.
0:31:05 > 0:31:08- That's what they do when they signal to each other.- Oh, really?
0:31:08 > 0:31:11- So, this ant is signalling for other ants to come and help attack?- Yeah.
0:31:12 > 0:31:14Just give it a good tug.
0:31:14 > 0:31:16There we go.
0:31:18 > 0:31:20That was pretty gnarly.
0:31:20 > 0:31:22But bites bring up a good point, don't they?
0:31:22 > 0:31:25- That they're sore?- That's right. - Yes, they're incredibly sore.
0:31:25 > 0:31:28But that's often the interaction that people can have with insects
0:31:28 > 0:31:30and why they often think of insects as pests.
0:31:30 > 0:31:34Yup. Because they bite, but they also sting.
0:31:40 > 0:31:42BUZZING
0:31:42 > 0:31:44Bites can be painful enough,
0:31:44 > 0:31:47but the most powerful weapon in the insect armoury is the sting.
0:31:47 > 0:31:52Fear of being stung is one of the main reasons we dislike insects.
0:31:54 > 0:31:59In fact, only around five per cent of insect species have stings -
0:31:59 > 0:32:02the ants, bees and wasps.
0:32:03 > 0:32:07But these species are some of the most successful on the planet.
0:32:09 > 0:32:11Having a sting to defend themselves
0:32:11 > 0:32:13is a huge advantage for these insects.
0:32:15 > 0:32:18We're going to look at these powerful weapons in detail.
0:32:20 > 0:32:22But first, we want to feel their full force.
0:32:24 > 0:32:27And this time, I'm going to put myself in the firing line.
0:32:33 > 0:32:37To experience the power of the ultimate insect defence,
0:32:37 > 0:32:40I'm meeting the world's expert - Justin Schmidt.
0:32:41 > 0:32:45He's been stung by over 150 different insects -
0:32:45 > 0:32:49that's a serious amount of pain in the name of scientific research.
0:32:49 > 0:32:51What've we got here?
0:32:51 > 0:32:55These are harvester ants. They're native to the Sonoran Desert here.
0:32:55 > 0:32:58We call them rugged harvester ants. And they collect seeds.
0:32:58 > 0:33:03So unlike many predatory ants, they're mostly vegetarian.
0:33:03 > 0:33:06But they still pack a wallop for a sting.
0:33:06 > 0:33:09OK, so, we have a lot of ants, what's next?
0:33:09 > 0:33:12Well, I thought it might be interesting to have you
0:33:12 > 0:33:16experience one of these, and you're a hardy soul, so I'm sure...
0:33:16 > 0:33:18- "Experience" one of these, huh?- Yes.
0:33:18 > 0:33:20So what we'll do is we'll get one to crawl on you.
0:33:22 > 0:33:27They have barbs, just like honeybee stings. That one's stinging you now.
0:33:27 > 0:33:29OK, that one's definitely stinging. Look.
0:33:29 > 0:33:31- You might actually be able to feel that one.- I can.
0:33:31 > 0:33:34Your skin's is a little bit thinner.
0:33:34 > 0:33:38I can already feel the pain increasing,
0:33:38 > 0:33:40the burn so to speak. Oop!
0:33:40 > 0:33:42It's as if I took a very hot metal,
0:33:42 > 0:33:46but small structure, and put it up against my skin.
0:33:46 > 0:33:51And it is increasing, I suppose, every minute.
0:33:51 > 0:33:55A good sting will last for a number of hours,
0:33:55 > 0:34:00and they're just this kind of throbbing, piercing waves of pain.
0:34:04 > 0:34:08One of the reasons we most fear stinging insects is that
0:34:08 > 0:34:10there's rarely just a single offender.
0:34:12 > 0:34:16Like bees and wasps, ants are social insects, living in huge groups.
0:34:18 > 0:34:20Only queens lay eggs.
0:34:20 > 0:34:23So the role of the other females is limited to supplying
0:34:23 > 0:34:25and defending the nest.
0:34:25 > 0:34:30And in these females, evolution has adapted the basic insect body plan.
0:34:30 > 0:34:36Over time, their egg-laying tube has transformed to deliver not eggs,
0:34:36 > 0:34:37but venom.
0:34:40 > 0:34:43And it's that venom that causes us pain when we're stung.
0:34:45 > 0:34:49Justin has developed his own pain scale to try to understand
0:34:49 > 0:34:51why some venoms hurt more than others.
0:34:51 > 0:34:56From the mildest pinprick, a number 1, to the most painful - number 4.
0:34:58 > 0:35:02So I've experienced a harvester ant, which you rated as a 3,
0:35:02 > 0:35:05- and a 4, we have a tarantula hawk wasp.- Exactly.
0:35:05 > 0:35:10The tarantula hawk wasp uses its powerful venom to immobilise
0:35:10 > 0:35:14the 12-cm-long tarantulas of the American desert.
0:35:14 > 0:35:17As close to maximal pain as you can get, huh?
0:35:17 > 0:35:19It's the highest thing in the US. So welcome to the top.
0:35:19 > 0:35:23You're in rarefied air.
0:35:23 > 0:35:30So, um, what I'm thinking is I'll grab it from the top.
0:35:30 > 0:35:32The dorsal side of the body, on the thorax or the abdomen,
0:35:32 > 0:35:35- so it can't sting me from underneath. - That's your best hope.- OK.
0:35:37 > 0:35:38Hoo!
0:35:44 > 0:35:47OK. It's trying to sting me through...
0:35:47 > 0:35:51It's trying to sting me through my fingernail. Do you see that? Wow!
0:35:51 > 0:35:54- Fingernail's the one thing she can't get through.- OK.
0:35:54 > 0:35:56She's going underneath my fingernail.
0:35:56 > 0:35:59She might not be able to get through your tough skin there.
0:35:59 > 0:36:02She probably needs some place a little more vulnerable.
0:36:02 > 0:36:05- Let's give her my arm then, OK? - She'll get through that.
0:36:05 > 0:36:07Can you see this? Ah! Ow!
0:36:07 > 0:36:10Wow! Well, I guess she got through something.
0:36:14 > 0:36:16She's gone.
0:36:16 > 0:36:20- She's gone.- She's free and you're in pain.- Aagh!
0:36:22 > 0:36:23That hurts. Aagh!
0:36:23 > 0:36:26- Where'd she sting? I didn't... - Right underneath the fingernail,
0:36:26 > 0:36:29which is something that I have always not wanted to have happen.
0:36:29 > 0:36:32- She did get under your fingernail.- Whoo!
0:36:32 > 0:36:36- Is that more than the...- Yeah, it's more than the harvester ants.
0:36:36 > 0:36:38Whoo! That is, that's...
0:36:41 > 0:36:44That was pain. She definitely got underneath.
0:36:44 > 0:36:47There's still a great deal of mystery over why some insect
0:36:47 > 0:36:50stings hurt more than others.
0:36:50 > 0:36:54The pain doesn't closely match their size or how big their colonies are.
0:36:54 > 0:36:57But Justin's brave work is at least a starting point
0:36:57 > 0:37:01in understanding this incredibly potent insect defence system.
0:37:02 > 0:37:08She won, we lost. One for tarantula hawk, zero for scientists.
0:37:13 > 0:37:16- So, shall we have a look at some stingers?- I think so.
0:37:16 > 0:37:17I have this hornet here.
0:37:17 > 0:37:22And, you can see just how big the body is compared to my finger.
0:37:22 > 0:37:24There is something unnerving about the sight of a sting.
0:37:24 > 0:37:26It is very long.
0:37:26 > 0:37:29It is also incredibly sharp, so if I put this pin,
0:37:29 > 0:37:32this is a dissecting pin that we use.
0:37:32 > 0:37:36- Look at that.- And guess which one is sharper? The insect wins!- Yeah.
0:37:36 > 0:37:40So that's a hornet. Let's look at a yellow jacket.
0:37:40 > 0:37:41This is a smaller wasp.
0:37:41 > 0:37:46- So this is just the sort of wasp in your back garden.- That's right.
0:37:46 > 0:37:48Now something like this would probably
0:37:48 > 0:37:52fall at a two on the pain index, which is
0:37:52 > 0:37:55kind of a run-of-the-mill sting, a run-of-the-mill painful sting.
0:37:55 > 0:38:02Same as honeybees. And its stinger is retracted into its abdomen.
0:38:02 > 0:38:05And whenever this thing is not using its stinger, it's held within
0:38:05 > 0:38:08the abdomen for safekeeping.
0:38:08 > 0:38:09So that's the stinger.
0:38:11 > 0:38:12Look at that.
0:38:12 > 0:38:15Along with this stinger is a whole sting apparatus,
0:38:15 > 0:38:18which includes a venom gland and a venom sac
0:38:18 > 0:38:21because we need the glands to secrete that venom
0:38:21 > 0:38:23into the sac, and the pumping of the sac is what expels that
0:38:23 > 0:38:26through the stinger into some type of predator.
0:38:26 > 0:38:27And that's the venom sac.
0:38:27 > 0:38:30Yeah. So we have an entire sting apparatus here.
0:38:32 > 0:38:35Stings vary in shape.
0:38:35 > 0:38:37The straight-needle type of wasps,
0:38:37 > 0:38:41and a barbed type we see in honeybees.
0:38:41 > 0:38:43The barbs mean that when the honeybee stings,
0:38:43 > 0:38:46the stinger stays anchored into our skin.
0:38:49 > 0:38:50This kills the bee,
0:38:50 > 0:38:54but allows the venom to keep flowing into your body...
0:38:56 > 0:38:58..whereas the wasp can remove its straight-edged stinger
0:38:58 > 0:39:00and live to sting another day.
0:39:02 > 0:39:05BUZZING
0:39:08 > 0:39:11So we've looked at the battery of tools that help insects
0:39:11 > 0:39:12eat and defend themselves.
0:39:12 > 0:39:16But that's not the only way their basic body plan has adapted
0:39:16 > 0:39:18to their advantage.
0:39:20 > 0:39:22As we saw earlier,
0:39:22 > 0:39:25the outer skin of the insect - the cuticle - is extremely
0:39:25 > 0:39:31versatile, able to mould itself into endless shapes and forms.
0:39:31 > 0:39:35This has allowed insects to evolve a vast variety of highly
0:39:35 > 0:39:38specialised body parts on the outside.
0:39:38 > 0:39:42Some of their most remarkable innovations are the tools
0:39:42 > 0:39:45that sense the world around them.
0:39:45 > 0:39:48To see those, we need a fresh specimen.
0:39:55 > 0:39:57So, right here I have a dragonfly.
0:39:57 > 0:40:00Yeah, and it is a fantastic specimen of a dragonfly.
0:40:00 > 0:40:02They have the biggest eyes in the insect world.
0:40:02 > 0:40:05In fact, they're these massive big domes
0:40:05 > 0:40:08that cover almost the entire head.
0:40:08 > 0:40:12And these two big globular eyes in insects are known as compound eyes.
0:40:12 > 0:40:14And that is a key sort of feature
0:40:14 > 0:40:16of most insects is a compound eye
0:40:16 > 0:40:20which is made up of thousands and thousands of individual cylinders
0:40:20 > 0:40:23with capped lenses on the top.
0:40:24 > 0:40:28Up to 30,000 individual lenses in each dragonfly eye
0:40:28 > 0:40:31give an almost 360-degree view
0:40:31 > 0:40:33of the world around them.
0:40:33 > 0:40:34So, now that we're looking
0:40:34 > 0:40:36at the inside of the eye,
0:40:36 > 0:40:38we see a bunch of different types of tissue.
0:40:38 > 0:40:40Once you get through the soft tissue
0:40:40 > 0:40:42and through some of that goop,
0:40:42 > 0:40:44you can get to the actual inner surface of that eye.
0:40:44 > 0:40:46Can you see these sort of glistening,
0:40:46 > 0:40:48sort of diamond-like structures there?
0:40:48 > 0:40:49That's clearly the lenses.
0:40:49 > 0:40:51You've cleared away the gunk
0:40:51 > 0:40:54- and we're seeing the lenses, reflecting the light.- Yeah, amazing.
0:41:01 > 0:41:03But the eyes are only one part
0:41:03 > 0:41:05of the insect's sensory toolkit.
0:41:09 > 0:41:11What we're going to look at next
0:41:11 > 0:41:13is something even more impressive -
0:41:13 > 0:41:15the antennae.
0:41:15 > 0:41:18Antennae can detect movement, heat,
0:41:18 > 0:41:20moisture and sound.
0:41:20 > 0:41:21And most importantly,
0:41:21 > 0:41:23they detect smells.
0:41:25 > 0:41:28The moth antenna is one of the most elaborate examples
0:41:28 > 0:41:30in the insect world.
0:41:30 > 0:41:32Now, if we actually zoom in further,
0:41:32 > 0:41:34so we'll go into about 400x,
0:41:34 > 0:41:36there we go, you can actually see
0:41:36 > 0:41:39hundreds and hundreds of sensory hairs
0:41:39 > 0:41:41which allows the moth to detect
0:41:41 > 0:41:43really small amounts of chemicals.
0:41:45 > 0:41:46And that is really important,
0:41:46 > 0:41:48especially for a male moth.
0:41:48 > 0:41:50Because to find a mate,
0:41:50 > 0:41:53he has to be able to detect only a few molecules of a chemical
0:41:53 > 0:41:55known as a sex pheromone,
0:41:55 > 0:41:58emitted by a female.
0:42:01 > 0:42:03But insect antennae come in all shapes and sizes,
0:42:03 > 0:42:07and that's because odour plays a really, really important part
0:42:07 > 0:42:08in their everyday lives.
0:42:14 > 0:42:17Right under our noses, in every field and forest,
0:42:17 > 0:42:20there's a hidden battle taking place,
0:42:20 > 0:42:24move and countermove in a life or death game of chemical warfare.
0:42:26 > 0:42:29Smell is everything to insects.
0:42:29 > 0:42:32Their incredible antennae put them leagues ahead of us
0:42:32 > 0:42:34when it comes to detecting odours.
0:42:34 > 0:42:37And they use these volatile cues to find food, a mate,
0:42:37 > 0:42:39or even a place to lay their eggs,
0:42:39 > 0:42:42all of which are vital to their survival.
0:42:42 > 0:42:44Now, in this field,
0:42:44 > 0:42:46to me it just smells a little bit earthy,
0:42:46 > 0:42:49and beyond smelling like a field should smell
0:42:49 > 0:42:51I can't really detect anything else.
0:42:53 > 0:42:57What I can't pick up is that each plant is sending out
0:42:57 > 0:42:59different chemical messages into the air.
0:43:02 > 0:43:04This field is part of a project
0:43:04 > 0:43:08at Rothamsted Research Station, in Hertfordshire.
0:43:08 > 0:43:12And the insects that live here are some of the most studied on Earth.
0:43:15 > 0:43:19Gia Aradottir studies how insects sense smell.
0:43:19 > 0:43:21She works on aphids,
0:43:21 > 0:43:24a pest that destroys many of our crops.
0:43:24 > 0:43:27And she's enlisted the help of a natural aphid enemy
0:43:27 > 0:43:30to show me how insects use their sense of smell
0:43:30 > 0:43:32to work out their world.
0:43:33 > 0:43:35Here, in a little tube,
0:43:35 > 0:43:37is a tiny little parasitic wasp.
0:43:37 > 0:43:40Excellent, I love these guys.
0:43:40 > 0:43:42They actually lay their eggs inside the aphids.
0:43:42 > 0:43:44- Yeah, they parasitize the aphids. That's...- Yeah.
0:43:44 > 0:43:46I can't wait to see this.
0:43:46 > 0:43:50Yes, and you can see its antennae moving backwards and forwards.
0:43:50 > 0:43:52- Yeah, it's really having a good forage around, isn't it?- Yes.
0:43:52 > 0:43:55And it's coming up to the aphids now. It's found...
0:43:55 > 0:43:56Oh, my goodness,
0:43:56 > 0:43:58it's right in there, isn't it?
0:43:58 > 0:44:00It's injecting its egg into the aphid!
0:44:00 > 0:44:02- Into the aphid.- Brilliant, isn't it?
0:44:02 > 0:44:05And to think that this is going on right now in our gardens,
0:44:05 > 0:44:08on our rose bushes, without us even knowing.
0:44:08 > 0:44:10But where it becomes even more interesting
0:44:10 > 0:44:12is how the wasps find the aphids.
0:44:17 > 0:44:18And this is where the insect's
0:44:18 > 0:44:21incredibly powerful sense of smell comes in.
0:44:23 > 0:44:25Gia's research suggests
0:44:25 > 0:44:28that the wasps aren't directly smelling the aphids,
0:44:28 > 0:44:31they're picking up on a completely different chemical clue.
0:44:33 > 0:44:36To investigate their extraordinary ability,
0:44:36 > 0:44:39the first step is to collect two plants -
0:44:39 > 0:44:41one infested by aphids,
0:44:41 > 0:44:42the other one free of them.
0:44:45 > 0:44:48The chemical odours that they give off are captured overnight,
0:44:48 > 0:44:49ready for the next stage.
0:44:53 > 0:44:56Now, to see if the wasp's antenna can actually detect
0:44:56 > 0:44:59a chemical signal from the damaged plant.
0:45:00 > 0:45:03Gia delicately removes the antenna
0:45:03 > 0:45:05of an anaesthetised wasp
0:45:05 > 0:45:07and places it between a set of electrodes,
0:45:07 > 0:45:10primed to pick up any electrical signals.
0:45:12 > 0:45:14Now, what we've got here is a gas chromatograph,
0:45:14 > 0:45:17and chromatography is a separation process.
0:45:17 > 0:45:20Now, I've got two samples here.
0:45:20 > 0:45:25One sample which has been collected from an aphid-infested plant,
0:45:25 > 0:45:28and another sample which is from a normal plant,
0:45:28 > 0:45:30a plant that isn't infested with aphids.
0:45:30 > 0:45:32And we're going to inject these samples into this machine,
0:45:32 > 0:45:36which will separate the chemicals into their individual components
0:45:36 > 0:45:39and then blow them over the antenna of the insect.
0:45:40 > 0:45:44It's like being inside the wasp's mind.
0:45:44 > 0:45:46Every time the antenna senses a chemical,
0:45:46 > 0:45:48we see a response on the computer screen.
0:45:48 > 0:45:51These peaks form the message to the insect's brain.
0:45:54 > 0:45:57- OK.- So here's the trace from the sample that we ran,
0:45:57 > 0:46:00and on the top, you can see the insect responses.
0:46:00 > 0:46:05And all those little peaks are the insect responding
0:46:05 > 0:46:06to the plant sample.
0:46:06 > 0:46:08And on the bottom here,
0:46:08 > 0:46:11- we have the chemicals coming off from the plant.- Yeah.
0:46:14 > 0:46:15This is the air from the plant
0:46:15 > 0:46:17that had no aphids.
0:46:17 > 0:46:20Many different chemicals pass over the antenna,
0:46:20 > 0:46:24but the wasp only pays attention to some of them.
0:46:24 > 0:46:26But now, look what happens
0:46:26 > 0:46:29when the air from the aphid-infested plant
0:46:29 > 0:46:31blows over the antenna.
0:46:31 > 0:46:33New chemicals appear,
0:46:33 > 0:46:35signals from the damaged plant.
0:46:35 > 0:46:36And big new peaks also appear
0:46:36 > 0:46:38in the wasp's response.
0:46:38 > 0:46:41Its ultra-sensitive antennae
0:46:41 > 0:46:43are picking up the new chemicals
0:46:43 > 0:46:46and sending a different signal to its brain.
0:46:49 > 0:46:53The damaged plants are sending out a distress call.
0:46:53 > 0:46:57The chemicals it releases actually attract the wasps -
0:46:57 > 0:46:59insects that destroy aphids.
0:46:59 > 0:47:04Plant and parasite are working together to get rid of the pest.
0:47:06 > 0:47:09Having cracked this chemical conversation,
0:47:09 > 0:47:12scientists are now breeding wheat crops that release odours
0:47:12 > 0:47:14to attract aphid predators.
0:47:15 > 0:47:20If they succeed, they'll be able to reduce the use of pesticides.
0:47:20 > 0:47:23As we discover more about the insect's antennae
0:47:23 > 0:47:25and its incredible sense of smell,
0:47:25 > 0:47:28we're beginning to put it to good use for ourselves.
0:47:28 > 0:47:31One hope is that we might be able to develop mosquito repellents
0:47:31 > 0:47:34based on the smells from people who rarely get bitten.
0:47:34 > 0:47:36We can even train bees
0:47:36 > 0:47:39to sniff out chemicals from drugs and explosives,
0:47:39 > 0:47:41much better than sniffer dogs.
0:47:41 > 0:47:43And the more scientists are able
0:47:43 > 0:47:46to translate this hidden world of communication
0:47:46 > 0:47:48below each and every leaf,
0:47:48 > 0:47:51the more we might be able to turn the insect sense of smell
0:47:51 > 0:47:52to our own advantage.
0:47:56 > 0:47:59Our insect dissection is nearly complete.
0:47:59 > 0:48:02We've gone deep inside the insect body
0:48:02 > 0:48:04to reveal an internal structure
0:48:04 > 0:48:06that's radically different from our own.
0:48:07 > 0:48:10And we've stripped back the specialised body parts
0:48:10 > 0:48:12that have made them so successful.
0:48:12 > 0:48:15But there's one last challenge.
0:48:15 > 0:48:17Our most ambitious dissection.
0:48:17 > 0:48:21And the insect's most important evolutionary achievement.
0:48:29 > 0:48:31What amazes me is how we look across the diversity of insects,
0:48:31 > 0:48:33we see that most of them have wings.
0:48:33 > 0:48:35Yeah, and they evolved to fly very early on,
0:48:35 > 0:48:38- which has to be key to their success.- That's right.
0:48:38 > 0:48:40It enables them not only to live a lot of their lives up in the air,
0:48:40 > 0:48:44but mostly spread throughout the world and dominate it.
0:48:44 > 0:48:48Insects are some of nature's most agile fliers.
0:48:48 > 0:48:51No man-made machine can match them.
0:48:51 > 0:48:52So what's their secret?
0:48:52 > 0:48:58The dragonfly is one of the fastest fliers in the insect world.
0:48:58 > 0:49:00And the first thing we're going to look at
0:49:00 > 0:49:03are the muscles that power their flight.
0:49:03 > 0:49:06All right, so we're going to go inside the thorax.
0:49:06 > 0:49:08So I'm going to take this pair of scissors
0:49:08 > 0:49:11and just make some snips and see what we can find.
0:49:11 > 0:49:13And you have to be quite careful,
0:49:13 > 0:49:16because obviously the thorax contains massive muscles
0:49:16 > 0:49:18that are used to move the wings,
0:49:18 > 0:49:20it's like the powerhouse of the insect.
0:49:21 > 0:49:23Now, I want to open it up
0:49:23 > 0:49:26along that incision that I've made.
0:49:26 > 0:49:29And as we open it there... Oh, look at that!
0:49:29 > 0:49:31Oh, that is brilliant, isn't it?
0:49:31 > 0:49:33You can see all those flight muscles.
0:49:33 > 0:49:36So these are the muscle fibres here,
0:49:36 > 0:49:38just running up and down.
0:49:38 > 0:49:40So we're looking in from the top side,
0:49:40 > 0:49:42so these muscles run from the top
0:49:42 > 0:49:44- to the bottom of the thorax. - That's right.
0:49:44 > 0:49:47You really get a sense for how big those muscles are
0:49:47 > 0:49:50and how powerful they have to be to be able to lift the insect
0:49:50 > 0:49:53and sustain flight with a really high wing-beat frequency as well.
0:49:53 > 0:49:56- And what a strong flier this one is. - Yeah, absolutely.
0:49:59 > 0:50:02Insects need ultra-fast wing beats to stay in the air.
0:50:03 > 0:50:07So their flight muscles have to be huge and powerful.
0:50:08 > 0:50:11They make up 60% of body weight in some dragonflies.
0:50:13 > 0:50:18And the muscle itself is the most active animal tissue on Earth.
0:50:18 > 0:50:20This means it needs a lot of air.
0:50:20 > 0:50:24Now, as I'm getting through here, I'm seeing some reflective tissue,
0:50:24 > 0:50:26I'm wondering if those are air sacs?
0:50:26 > 0:50:31I think they might be air sacs. Give one a poke!
0:50:31 > 0:50:35Wow! These are continuations of the respiratory system.
0:50:35 > 0:50:38They connect up to all those tubes we saw earlier, OK.
0:50:38 > 0:50:41But these are little reservoirs of air that help ventilate the body
0:50:41 > 0:50:43and push air through those tubes.
0:50:43 > 0:50:45Imagine the amount of oxygen you must need
0:50:45 > 0:50:48in those massive muscles to keep them fed with oxygen,
0:50:48 > 0:50:50keep them powerful.
0:50:50 > 0:50:52These air sacs are wigging me out! These are interesting.
0:50:52 > 0:50:55I rarely see these in the course of a dissection.
0:50:55 > 0:50:58I was trying to figure out what "wigging me out" meant.
0:50:58 > 0:50:59I think I get it!
0:51:01 > 0:51:03So, we're probing down into this new tissue
0:51:03 > 0:51:08and just making some pokes, which is often what a dissection is.
0:51:08 > 0:51:10- You see that?- Yeah.
0:51:10 > 0:51:12So we've gone right the way through the thorax.
0:51:12 > 0:51:15We've encountered massive muscles used for flight.
0:51:15 > 0:51:18We've got air sacs that help the insect to fly
0:51:18 > 0:51:21- because it feeds the muscles with air and oxygen.- That's right.
0:51:21 > 0:51:24We've reached the exoskeleton. It's green on the inside,
0:51:24 > 0:51:27- as well as on the outside. - Look at that!
0:51:27 > 0:51:29Now, let's check out the wings
0:51:29 > 0:51:31and see what the structure is all about.
0:51:31 > 0:51:35And the wings are not like wings of a plane that are really smooth.
0:51:35 > 0:51:39- They are actually quite ridgy, aren't they?- They are, yeah.
0:51:39 > 0:51:41And there you can see cross-sections.
0:51:41 > 0:51:46It's quite interesting to see this sort of zigzag shape on the wing.
0:51:53 > 0:51:57Insect wings might look like haphazard structures -
0:51:57 > 0:52:00nothing like the aerodynamic design of a bird.
0:52:01 > 0:52:05But insects are incredible aerial acrobats.
0:52:05 > 0:52:08They can fly faster than any human can sprint,
0:52:08 > 0:52:12turn 180 degrees in a tenth of a second
0:52:12 > 0:52:14and land upside down on a flower petal,
0:52:14 > 0:52:19all the time compensating for every tiny gust and puff of turbulence.
0:52:23 > 0:52:25Human engineers have long dreamt
0:52:25 > 0:52:28of being able to build miniature flying machines
0:52:28 > 0:52:30that match insects for agility.
0:52:32 > 0:52:35To achieve that goal, teams at Harvard University
0:52:35 > 0:52:39are trying to find out more about how insect wings work.
0:52:50 > 0:52:52They're starting with the most agile
0:52:52 > 0:52:55fliers of them all, our old friend the dragonfly.
0:52:57 > 0:53:00I'm releasing fruit flies to tempt them into a chase.
0:53:02 > 0:53:03There we go.
0:53:09 > 0:53:11It's chewing.
0:53:11 > 0:53:15Thanks for introducing me to this. These things are amazing creatures.
0:53:15 > 0:53:17Absolutely. Perching dragonflies
0:53:17 > 0:53:21sit on a perch and wait for a prey to fly over them...
0:53:21 > 0:53:25- Usually small insects?- Usually small insects. Flies, some type of fly.
0:53:25 > 0:53:27And insect wings don't just stay flat,
0:53:27 > 0:53:30they twist and bend and contort.
0:53:30 > 0:53:33What you're looking for in flight is how they do that,
0:53:33 > 0:53:36and if certain contortions are important for flight.
0:53:42 > 0:53:46Frame by frame, the research forensically analyses each hunt.
0:53:48 > 0:53:52Lightning-quick adjustments in the angles of four beating wings
0:53:52 > 0:53:54combine into a deadly flight manoeuvre.
0:53:56 > 0:53:58Further down the corridor,
0:53:58 > 0:54:01fellow flight researcher Andrew Mountcastle is investigating
0:54:01 > 0:54:03how the structure of bumblebee wings
0:54:03 > 0:54:06helps keep their heavy bodies in the air.
0:54:08 > 0:54:12Andrew's experimental method begins with attaching a string of weights
0:54:12 > 0:54:14to an anaesthetised bee.
0:54:16 > 0:54:18Next, he glues a speck of glitter to each wing.
0:54:22 > 0:54:25- That was an amazingly meticulous. - It is!
0:54:25 > 0:54:27And you created that method yourself?
0:54:27 > 0:54:29- I did, yes. - So, what's the glitter for?
0:54:29 > 0:54:31So, we're using the glitter
0:54:31 > 0:54:34as a microsplint to actually immobilise a joint
0:54:34 > 0:54:36in the wing surface itself,
0:54:36 > 0:54:39where the wing naturally hinges.
0:54:39 > 0:54:41And that immobilises that joint.
0:54:43 > 0:54:46Many insect wings bend during each flap.
0:54:46 > 0:54:50Andrew wants to discover why this happens.
0:54:50 > 0:54:53Is it just an unfortunate trade-off for a lightweight design?
0:54:53 > 0:54:57Or does the bend actually help the insect to stay in the air?
0:54:57 > 0:54:59Time to see if the bee has woken up.
0:54:59 > 0:55:02- So, here's the tethered bee, huh? - Here's the bee.
0:55:02 > 0:55:07- We've attached the string of beads to it.- Awesome!
0:55:07 > 0:55:11- The idea is we're now going to test it.- Can I hold it?- Sure.- OK.
0:55:13 > 0:55:16We're now going to test its force production.
0:55:17 > 0:55:19You can tell how powerful they are.
0:55:19 > 0:55:22You can feel the air currents around the wing beats
0:55:22 > 0:55:23as it's flying around you.
0:55:23 > 0:55:24That's right, yup.
0:55:29 > 0:55:30Oh, lovely!
0:55:33 > 0:55:36You know, I've never held a bee on a leash before.
0:55:36 > 0:55:40This is one of the most amazing things I've ever done!
0:55:40 > 0:55:44Wow, it's amazing. It's just going round in circles, too, huh?
0:55:45 > 0:55:48Andrew places the weighted bee in a flight chamber
0:55:48 > 0:55:51to see how high it will lift the beads.
0:55:51 > 0:55:53It's an experiment he's repeated many times,
0:55:53 > 0:55:56with and without the glitter splint on the wing joint.
0:55:58 > 0:56:00In the course of an experiment,
0:56:00 > 0:56:04I do multiple load-lifting trials for a bee, and...
0:56:04 > 0:56:08There it goes. Look at that! It brought all the beads up.
0:56:08 > 0:56:10It went right to the light just like you expected.
0:56:10 > 0:56:12It's carrying all of the beads.
0:56:12 > 0:56:16That's right. So, what this means is I haven't...
0:56:17 > 0:56:19Wow! What a strong bee.
0:56:19 > 0:56:23That's amazing. That is amazing! That's a strong bee.
0:56:26 > 0:56:29Andrew's research shows that having the wing splint
0:56:29 > 0:56:31to prevent it from bending
0:56:31 > 0:56:34makes the bees about 10% less powerful.
0:56:34 > 0:56:38So it does seem that wing bends are a design feature with a purpose.
0:56:48 > 0:56:49Elsewhere in Harvard,
0:56:49 > 0:56:53teams are learning from insect flight to try and build
0:56:53 > 0:56:55the world's smallest flying robots.
0:56:55 > 0:56:57It's an ambitious goal.
0:57:03 > 0:57:06When the time comes that these robots are fully functional,
0:57:06 > 0:57:08what are the various uses you envision?
0:57:08 > 0:57:11We envision these things being used for a variety of applications.
0:57:11 > 0:57:14Things like search and rescue,
0:57:14 > 0:57:15hazardous environment exploration.
0:57:15 > 0:57:18Anywhere you wouldn't want to put a human or animal.
0:57:18 > 0:57:21In situations where there might be a collapsed building,
0:57:21 > 0:57:23a firefighter with a thousand of these,
0:57:23 > 0:57:25and sends them in to try and find a survivor.
0:57:25 > 0:57:28If 997 failed, but 3 work and sense something
0:57:28 > 0:57:29then that is a success.
0:57:31 > 0:57:35But as one of Rob's students shows there's still a long way to go.
0:57:37 > 0:57:39So, this is the Robobee?
0:57:39 > 0:57:43This is a flying Robobee that we're going to test.
0:57:43 > 0:57:47Three, two, one. And, go!
0:57:50 > 0:57:52Nice! Nice!
0:57:52 > 0:57:54- So, it moved.- Yeah, it did.
0:57:54 > 0:57:56- It crashed and burned, but it moved?- Yup.
0:57:59 > 0:58:02The challenges of mimicking nature remain immense.
0:58:03 > 0:58:06But the close examination of insect flight
0:58:06 > 0:58:08is helping the team get a few steps closer.
0:58:13 > 0:58:16Our insect dissection is over.
0:58:16 > 0:58:20It's shown how insects have evolved to survive on Earth in ways
0:58:20 > 0:58:22that are radically different to us.
0:58:23 > 0:58:26And as we've taken bug bodies apart,
0:58:26 > 0:58:30we've revealed that their solutions can be more effective than ours.
0:58:31 > 0:58:34Now that we've explored the insect body,
0:58:34 > 0:58:36we can appreciate one of the best examples
0:58:36 > 0:58:38of nature's engineering genius.
0:58:38 > 0:58:41And the insect's body plan may seem simple,
0:58:41 > 0:58:45but in reality, it's an incredibly successful blueprint.
0:58:45 > 0:58:48One that has enabled them to conquer the planet.
0:58:50 > 0:58:53Most of us will never learn to love insects.
0:58:53 > 0:58:55But perhaps we can learn to respect them.
0:59:21 > 0:59:24Subtitles by Red Bee Media Ltd