Insect Dissection: How Insects Work

Insects. They buzz. They bite.

They bother us.

But for each one of us, there are 200 million of them.

They've conquered nearly every corner of our planet.

This is a bug's world.

So, what's the secret of their success?

I'm James Logan.

And I'm Brendan Dunphy.

We're both entomologists - and we think that to understand insects,

you have to get inside them.

So to unlock their secrets, we've built our own dissection lab,

where we're going to take insects apart bit by bit

to reveal a remarkable hidden world.

Body parts so strange they look almost alien.

Incredible pieces of natural engineering that surpass

the best inventions of humans.

There we go. Oh, fantastic!

We'll explore the insect body in ways even we've never tried before.

Oh! Oh... Ho-ho!

And we'll meet the scientists

who are making new discoveries about how insects work.

This is one of the most amazing things I've ever done.

Taking bug bodies apart will at times be challenging.

Smell that. That doesn't smell good.

Perhaps even gruesome.

But it will be a revelation - as we discover

how their extraordinary anatomy has helped them conquer our planet,

and what we can learn from insects.

This is our dissection table,

where we're going to be taking apart our bug bodies systematically.

In a series of dissections, we're going to use these tools,

and state-of-the-art microscopes,

to reveal the secrets of insects in incredible detail.

And we have some amazing specimens here - living ones,

as well as lab collections that have been put together with

painstaking work over decades.

To begin to understand why they're so successful,

what we want to do first is investigate just how

different their fundamental body plan is from ours.

Now, you might think about this cockroach as a pest in your home.

And you'd be right. But to me and Brendan,

this is an incredibly good specimen of an insect.

We're going to use this microscope, which is going to blow up the image,

and let you see what we're doing. And the place we're going to start

is here, the exoskeleton.

And this external skeleton, which supports and protects the body,

is common to all insects.

And it's also one of the major differences between them and us.

We have a skeleton on the inside of our body,

but they wear theirs on the outside of their bodies.

That's right.

And when you stand on a cockroach and it makes that crunching sound,

that's actually the exoskeleton breaking.

So the first thing I'm going to do is I'm going to take this pin,

which is incredibly fine but very strong, and get it through the neck.

That's a nice anchor point.

It is. Just get a couple of pins in there.

-You can hear it crunch.

-It did crunch when I put it through.

It's actually quite tough to get the pins through.

So I'm now going to chop off the legs.

And obviously they've got six legs, because they're insects.

-There goes six.

-There you go. And I'm going to use some scissors.

I've got these very fine scissors but they're extremely sharp.

They have to be extremely sharp to get through the cuticle,

which is very hard.

So let's give this a go.

All bugs share a basic body plan,

a head,

a thorax - that's the middle section where you find the legs and wings -

and an abdomen.

Covering it all is a layer called the cuticle,

the outer part of the exoskeleton.

It coats the whole insect body...

..from the tips of the antennae to the end of every wing, leg and claw.

I have to be quite careful when I'm doing this,

because obviously I want to preserve the organs inside,

that we're going to have a look at in a second.

I'm about to snap through the thorax,

which is probably one of the thicker parts of the exoskeleton. Listen.

-You hear that crack?

-I can.

It's incredibly thick and tough in this part.

Right, I'm going to try and pull the cuticle from the bottom

of the insect, which is facing upwards, off.

And in theory - in theory - this should come off in a one-er.

This is the bit I love, this is fantastic.

-When you get this open...

-This is the reveal.

..it reveals a hidden world, it really is a hidden world, I think.

I think it's brilliant.

OK, here we go.

-Wow.

-Check that out.

You know, it never ceases to amaze me,

to look inside of an insect body when you dissect it.

I know. But the thing is, when you get to the inside,

the first thing you see is all this sort of white mush,

which is what you see when you stand on them basically, isn't it?

And we don't see any bones.

The skeleton of the insect is on the outside.

That's right, so the body is surrounded by this cuticle,

which basically covers the entire outside of the body.

But it even gets inside as well,

extending inwards as attachment points for muscles.

The cuticle acts as both a skin and a skeleton.

It's like an armoured coating that also supports the bug's bodyweight.

Having an exoskeleton means insects have to

shed their skins as they grow.

But the rigid coating also allows them to construct some of the most

complex and intricate body shapes in nature.

Lightweight, waterproof,

tough yet flexible...

..the cuticle is one of nature's wonder materials.

It's allowed insects to live

and thrive where few other animals can survive.

And to take a closer look at it,

we're going to use this -

the scanning electron microscope.

This allows us to see insects at up to 60,000 times their actual size.

So here I have a mosquito sample.

And mosquitoes are my favourite insects.

So I'm going to put this sample in.

-Hey, James.

-Yeah?

-You should check this out.

OK. What've you got?

Ah, nice. Mosquito?

Yup. Let's change the resolution.

OK, so that's scanning down now and just giving us

a bit more resolution.

Mosquitoes might seem tiny and squashable at our scale.

But magnified hundreds of times we can see the tough exoskeleton

surrounding their body.

What looks smooth to the naked eye becomes incredibly complex.

Here on the wing, we discover microscopic hair-like structures.

These can sense tiny gusts of wind

and help guide the insect through turbulent air.

If you look at any insect at this scale - the cuticle becomes

a dramatic landscape.

These are scales on a butterfly's wing.

Magnifying closer and closer,

we see that each scale is lined with tiny ridges.

These interact with the light that strikes them,

giving the wings their vibrant shifting colours.

The insect exoskeleton is a marvel of animal engineering.

So the exoskeleton is far more than it first appears -

it's an incredibly sophisticated

and versatile piece of the insect's anatomy.

And now that we've peeled away that outer shell,

we can take a look deeper inside.

As we've seen, the first thing you find

when you open up an insect is a kind of white mush.

It's known as "fat body".

So, what I've been doing is teasing away all the fat body.

There's a ton of it here.

You notice this clump that I've been accumulating.

The fat body is like an all-in-one storage tissue -

holding protein, fats and other nutrients.

But to reach the vital body systems that power the insect,

we're going to clear it away.

Now we can delve into the abdomen and see what else we can find.

Now, the next system that we come upon is a really interesting

system in insects. It's the respiratory system.

And it's quite a strange system, isn't it?

-Very.

-I mean they don't have a heart as we know it.

They don't have a heart that pumps oxygen round the body,

and they don't have a circulatory system that feeds

the organs with oxygen, either.

Instead, they have tiny holes along the side of their abdomen

called spiracles.

And oxygen and air enters through these spiracles

into a large network of tubes that extend throughout the body

and surround the vital organs, feeding them with oxygen.

Insects breathe in a very different way from us.

Air entering the body passes into tubes called tracheae.

These divide into smaller and smaller branches,

a network that feeds oxygen to the innermost parts of the insect body.

So it's a direct oxygen delivery system, really brilliant.

And here, you can see how vast that network is.

This is just one forceps-full of tracheae.

-It's quite incredible.

-Branching out like a tree.

-Yeah, or lightning. It's quite beautiful.

-It is, very much.

This efficient breathing system is one of the major keys to

insect success. But it's also a clue to

one of the greatest mysteries of the insect world.

Why are they so small?

-VOICEOVER:

-'I tell you, gentlemen, science is agreed

'that unless something is done, and done quickly,'

man, as the dominant species of life on Earth,

will be extinct within a year.

Giant insects striking terror into us humans - a favourite of the B-movies.

But in reality, even the largest insects on the planet

are only about the size of a clenched fist.

Why don't they grow any bigger?

Why don't B-movie monsters exist in the real world?

At Arizona State University,

a team of scientists are trying to find out.

And they have a theory that it's all to do with the way insects breathe.

To investigate, they're taking some of the biggest

insects on Earth - beetles - and studying their breathing system.

But first they have to persuade them to do some serious exercise.

-Jaco?

-I'm Brendan.

-How are you?

-Good.

So what have we got here?

So, here I have a beetle

set up with two electrodes

implanted in the brain.

And then through these really thin,

silver wires we can deliver

a pre-defined electrical signal across the brain of the beetle.

And that will then stimulate the beetle to fly.

Although it may look a bit extreme, Jaco assures me

it doesn't harm them.

This setup reminds me of human exercise studies in which you

put a person on a treadmill and measure metabolic activity.

-That's what we're doing here, but with insects.

-Yes.

This is basically oxygen, or insect, exercise physiology.

But with humans, when you want someone to exercise you can

say, "OK, please, run. OK, run faster, run slower."

I can tell the beetle, "OK, please, fly. OK, please, fly,"

but it doesn't really work.

I'd love to see this in action.

OK, let's give it a buzz.

Aah, wow! Wow, look at how fast it's flapping.

Yeah. That's 70-75 wing beats per second.

If you hold your hands there,

you can actually feel the down force of wind.

Ah, you can feel the power like that, can't you?

-Yeah, you can definitely feel it.

-Wow.

During this strenuous exercise, Jaco measures the beetle's oxygen intake.

He wants to find out how its air tubes cope with

the insect equivalent of running a marathon.

The beetle's breathing system is very good at getting the air

to where it is needed.

But the trade-off is a lot of internal tubing.

And the bigger you get, the bigger tubes you need.

Especially for the bigger beetles, when you open up one of these

beetles, they're as big as... you can drive a bus through it.

The team have discovered what they think is a vital clue to

the small size of insects.

Scanning insects of different sizes,

they reveal the intricate web of breathing tubes inside.

As insects grow larger, they require more tubes.

The team noticed that the larger the insect,

the higher the percentage of body space taken up by these tubes.

Any bigger than a large beetle, and the theory is an insect would need

so much tubing that there wouldn't be space for other vital organs.

It's a compelling idea. But I'm left with a new mystery.

Because if we look far enough back in history,

we do find much bigger insects.

Fossil records show that when dinosaurs roamed the Earth,

dragonfly-like insects with wingspans nearly a metre long soared the skies.

So how was this possible?

Why didn't they suffer from the tubing problem?

Down the corridor, another researcher may have found the answer.

-John.

-Hey. How are you?

Doing good, how about you? So what's going on here?

Here we have Madagascar hissing cockroaches,

which we're rearing under different oxygen concentrations.

Hyperoxia here being higher than today's levels of oxygen,

and hypoxia being below today's levels of oxygen.

John is testing how big insects can grow with different

amounts of oxygen in the air they breathe.

Over the last 300-400 million years,

the amount of oxygen in the atmosphere has varied quite a bit.

It's gone up as high as 30% and down as low as 12%.

-And what is it right now?

-Right now, it's 21%.

So will we be able to see the effect that oxygen has on insect

body size in here?

Yeah. In fact we have some dragonflies right here.

And we can see that, here's a dragonfly that's been reared

under today's oxygen levels, so 21%.

And here's a dragonfly that's been reared under higher oxygen

levels, of 30%. Which is the highest value that we see in the past.

You can see even in a single generation

-you can get a visible effect on body size.

-Wow!

You can see this dragonfly is almost 20-25% longer than

the dragonfly reared in normal oxygen levels.

So it's amazing to think if that's a single dragonfly's lifetime,

what can happen over the course of hundreds of millions of years.

That's right, and in the geologic past,

we had giant dragonflies with the 70cm wingspans.

There's no question that changing atmospheric oxygen levels

over geologic time would have been influencing their development,

their size and their physiology.

Those ancient dragonflies may have been able to grow so big

because there was more oxygen in the air.

So the insects were less constrained by the problem of tubes.

At today's lower levels of oxygen, insects are destined to stay small.

Paradoxically, this has turned out to be an advantage.

The smaller you are, the more nooks

and crannies you can find to live in, and hide from predators.

Staying small has helped bugs to dominate our planet...

..while giant insects remain in the realm of science fiction.

Now that we've removed most of the breathing system,

we can carry on with our dissection and discover the next hidden

wonder of the bug body - the digestive system.

To get a better look, we need to take it out and unravel it.

And so far it has just been coiled up inside the body,

but we've removed it to one side.

So you can see actually how long this digestive system actually is.

The thing that I find remarkable about insects is that it's

not too dissimilar to our own digestive system.

It is pretty much the same thing.

It's a tube that runs the length of the whole body from the mouth

to the anus. And its job is to

extract nourishment from food and get rid of the waste.

The insect digestive system is simple but remarkably efficient.

Bugs can take nutrition from pretty much anything

in the natural world - from tree bark to rotting flesh.

Nutrients pass through the tube wall,

either straight into tissues that need them,

or into the fat body,

where they're stored for use later.

Along the tube are a set of organs

for breaking down food

and collecting waste.

One that insects have that we don't

is a crop - an expandable sack

that stores food before it gets to the stomach to be digested.

Handy if you're the type of insect

that might only find food every few days.

So there's the crop.

And you see it covered with the air tubes.

And in fact, some of the digestion can even start here.

Yeah, so there's some enzymes that are produced in

the digestive system that help to digest the food.

So let's see what the cockroach has been eating, huh?

It's not every day you get to look inside a cockroach's guts.

Look away now if you're squeamish.

I'm going to stick the digestive system back inside,

because when I cut this open

-it's probably going to make a bit of a mess.

-Right.

-Here we go.

I'm just going to rip it apart with these forceps. There we go.

Well, there we are. Wow.

I can smell that. That doesn't smell good.

What has this cockroach been eating?

-It looks like carrots.

-Doesn't smell like carrots.

-Or baby food.

Smells like dog food.

Yeah, you can really tell that it's partially digested.

It's partly solid yet kind of this slimy consistency.

Yeah. It's not particularly nice, is it?

-No, it's not.

-Could be anything.

They eat anything organic, whether it's plant or animal tissue,

and whether it's living or dead.

and that's one of the reasons that they're so successful as insects,

-is that they can find food virtually anywhere on the planet.

-Absolutely.

Cockroaches have survived largely unchanged for 300 million years

partly thanks to their unfussy diet.

But far richer food sources have appeared

since these omnivores first crawled the Earth.

And many other insects have adopted very specialised diets,

requiring some clever adjustments to their digestive system.

And to show this, I'm going to look at an insect which, like Brendan,

I study in my lab - the mosquito.

And it has a specialised way of feeding on blood -

in this case, mine.

So we've got in this tube a very hungry mosquito.

It's a female, because only the females bite.

And I'm going to place this mosquito on my arm.

There we go.

She's attracted to the chemicals given off in my body odour,

but also attracted to the heat

and the moisture given off by my skin as well.

And now it's feeding, it's not going anywhere.

And what I'm going to do is use this special camera to actually

show you the mosquito feeding.

Her proboscis is now deep inside my skin, sucking on my blood.

Most mosquitoes survive on nectar, but to make their eggs,

these females need the richer nutrients in my red blood cells.

As she takes in my blood,

her digestive system gets to work straight away.

It keeps the red blood cells,

and discards almost everything else as waste.

Even in the few minutes she's been feeding,

a drop of watery liquid oozes out of her back end.

But it's what's happening inside the mosquito that I want to see.

As she feeds, her stomach creates

a special membrane to contain the blood,

keeping it separate from any other food inside her.

This digestive system is very delicate.

But I'm going to try

and separate it from the rest of the body without bursting it.

OK, so here's our mosquito, which is nice and blood-fed.

It's surreal to think that you're actually going to

look at your own life fluid inside of her digestive system.

I know, it's something I've never done before.

We're both mosquito specialists, and neither of us have ever done this.

And I believe it's very difficult. So we'll give it a go anyway.

The next thing I'm going to do is chop its head off

because we'll pull its digestive system out the back end.

So it needs to be detached at the front end.

There we go. So you can see that I've removed the head,

and you can see the blood in the abdomen there.

-That is my blood.

-That is your blood in there.

Right.

There you have it.

So now you're just giving it a tug and seeing if we can pull it out.

OK, something's coming out.

Ah, check it out!

-There it is.

-No way.

-Look at that.

I cannot believe we've actually just done that.

First time, wow. That was amazing technique, by the way,

-so kudos to you.

-Thank you.

Shall we take a look closer in at that? That blood sac.

See whether we can...

-Nice.

-I mean, it really just looks like

we're looking at a blob of blood on the slide, doesn't it?

-It really does.

-But it's actually surrounded by

a peritrophic membrane, which sort of contains the blood,

but also contains any sort of viruses

and bacteria and stops them from getting into the mosquito's body.

But of course some of those things have evolved to get through it.

Like malaria parasites, for example.

So mosquitoes put a lot of time and investment in digesting that blood.

All for reproduction.

The digestive system is a huge factor in insects' global success.

Little more than a simple tube,

it can make a meal out of pretty much anything.

But to truly appreciate the simple efficiency of insect bodies,

you need to look at the next vital body system

we uncover as we continue our dissection.

So notice now we've got a new cockroach.

Because basically we've gone right the way through the anatomy

to the other side.

And the insect's nervous system,

the central nervous system runs down the belly of the insect.

So we have to go in from the back and find it that way.

-We're going to start snipping again.

-We're going to start snipping again.

I don't have to be as careful now

because we've already seen some of the organs.

-Because we know what we're going for.

-Yep. And we know where it is.

The nervous system extends from the head right the way down to

the bottom end of the insect.

So we need to see the whole thing here.

We're aiming for the insect's information highway.

The nervous system gathers the input from the senses

and controls all the body's vital functions and movement.

Now, in us we have a very complex organ in our central nervous system,

the brain, to take care of this.

Well, what does the insect have? That is what we're after now.

It's quite amazing. Insects do have a brain, a very simple brain.

But this is responsible for gathering and processing all

the information from the sensory organs, so the massive big eyes,

and the antennae which is their nose, this is where it is fed into.

So we can actually see now inside the head there.

It just looks like a mass of tissue,

but you can actually see the nerve cord which is running right

the way up the body, right from the bottom of the abdomen,

right the way up through the thorax and into the head to this brain.

Even if insects were the size of humans,

their brains would still be much smaller than ours.

Unlike us, they rely much less on their brains to carry out

vital functions like breathing, moving and eating.

So, what do they use instead? That's what we're looking for next.

Now I'm actually having to be quite careful at this point

because we are down now into the very belly of the insect

right where the nervous system is.

You can see this pair of nerve cords that run the entire

length of the body here.

And what you can see there is a great example of a ganglion,

which is a sort of nerve centre.

There are several of these bundles of nerve cells,

called ganglia, dotted around the insect's body.

Being closer to the organs

and limbs that they control

means that signals have to travel

over a much shorter distance than

going to the brain and back.

So there are actually nerve centres

not just in the head but throughout the entire body.

You sort of have to think of an insect as having its brain

almost all the way down its body.

As opposed to just in one section in the head.

To be dispersed in many different areas.

And these are responsible for

controlling the legs in this species.

With other insects that fly, for example,

they'd be involved in helping to control the wings.

It's amazing to think that this cockroach could keep

moving for weeks without its head

because its body is controlled by nerve centres outside the brain.

It would die only because it couldn't eat and drink.

So we've seen that insects have a set of incredibly efficient

systems for breathing, digestion and body control.

But these systems, in some form, are also found in

almost every other animal on Earth.

So what else about insects has allowed them to become

so successful?

To answer that, we need to look closer

at what they've been able to bolt on

to that basic core.

The specialised tools that have given them the edge.

And we'll start with some of the most impressive.

Insects have evolved an incredible array of mouthparts -

designed to feed on everything from fruit to foliage to flesh.

The longest mouthparts in the insect world

are the sucking tubes

of butterflies and moths,

but it takes a bit of gentle persuasion to see them.

There you go. It's almost doing it for me.

It's like I'm tickling its mouthpart

and it's extending its tongue out for us. What a performer!

It's nice to see at this level, close up, how coiled it is.

Brilliant, yeah.

It is a tube which is used to get into plants to get the nectar out.

I tell you, when I look at mouth structures,

that's when I really realise that the insect exoskeleton

is like a set of building blocks of all various shapes and sizes.

-Absolutely.

-And you see them being used for specific functions.

Most insects have a basic set of biting and chewing tools.

But from here evolution has run wild.

As well as the long sucking tube of the butterfly,

some mouthparts sponge up food, while others pierce

the skin of plants or animals then suck out liquid contents.

And mouthparts aren't always just feeding tools.

Some insects have added an extra function.

Cutting and slicing jaws have become powerful weapons that inflict

painful bites on their enemies.

Some of the most fearsome jaws in the insect world belong to ants.

So, what we've got here is a lovely big soldier ant.

Let's check out the action of these mandibles, shall we?

-Wow. Put it under the scope, let's see it under the scope!

-Agh!

Argh! Wow!

-How does it feel?

-It is kind of painful!

Just kind of? Look at that!

The strength in those mandibles is unbelievable!

Look at that. It's moving its abdomen up and down, too.

-That's what they do when they signal to each other.

-Oh, really?

-So, this ant is signalling for other ants to come and help attack?

-Yeah.

Just give it a good tug.

There we go.

That was pretty gnarly.

But bites bring up a good point, don't they?

-That they're sore?

-That's right.

-Yes, they're incredibly sore.

But that's often the interaction that people can have with insects

and why they often think of insects as pests.

Yup. Because they bite, but they also sting.

BUZZING

Bites can be painful enough,

but the most powerful weapon in the insect armoury is the sting.

Fear of being stung is one of the main reasons we dislike insects.

In fact, only around five per cent of insect species have stings -

the ants, bees and wasps.

But these species are some of the most successful on the planet.

Having a sting to defend themselves

is a huge advantage for these insects.

We're going to look at these powerful weapons in detail.

But first, we want to feel their full force.

And this time, I'm going to put myself in the firing line.

To experience the power of the ultimate insect defence,

I'm meeting the world's expert - Justin Schmidt.

He's been stung by over 150 different insects -

that's a serious amount of pain in the name of scientific research.

What've we got here?

These are harvester ants. They're native to the Sonoran Desert here.

We call them rugged harvester ants. And they collect seeds.

So unlike many predatory ants, they're mostly vegetarian.

But they still pack a wallop for a sting.

OK, so, we have a lot of ants, what's next?

Well, I thought it might be interesting to have you

experience one of these, and you're a hardy soul, so I'm sure...

-"Experience" one of these, huh?

-Yes.

So what we'll do is we'll get one to crawl on you.

They have barbs, just like honeybee stings. That one's stinging you now.

OK, that one's definitely stinging. Look.

-You might actually be able to feel that one.

-I can.

Your skin's is a little bit thinner.

I can already feel the pain increasing,

the burn so to speak. Oop!

It's as if I took a very hot metal,

but small structure, and put it up against my skin.

And it is increasing, I suppose, every minute.

A good sting will last for a number of hours,

and they're just this kind of throbbing, piercing waves of pain.

One of the reasons we most fear stinging insects is that

there's rarely just a single offender.

Like bees and wasps, ants are social insects, living in huge groups.

Only queens lay eggs.

So the role of the other females is limited to supplying

and defending the nest.

And in these females, evolution has adapted the basic insect body plan.

Over time, their egg-laying tube has transformed to deliver not eggs,

but venom.

And it's that venom that causes us pain when we're stung.

Justin has developed his own pain scale to try to understand

why some venoms hurt more than others.

From the mildest pinprick, a number 1, to the most painful - number 4.

So I've experienced a harvester ant, which you rated as a 3,

-and a 4, we have a tarantula hawk wasp.

-Exactly.

The tarantula hawk wasp uses its powerful venom to immobilise

the 12-cm-long tarantulas of the American desert.

As close to maximal pain as you can get, huh?

It's the highest thing in the US. So welcome to the top.

You're in rarefied air.

So, um, what I'm thinking is I'll grab it from the top.

The dorsal side of the body, on the thorax or the abdomen,

-so it can't sting me from underneath.

-That's your best hope.

-OK.

Hoo!

OK. It's trying to sting me through...

It's trying to sting me through my fingernail. Do you see that? Wow!

-Fingernail's the one thing she can't get through.

-OK.

She's going underneath my fingernail.

She might not be able to get through your tough skin there.

She probably needs some place a little more vulnerable.

-Let's give her my arm then, OK?

-She'll get through that.

Can you see this? Ah! Ow!

Wow! Well, I guess she got through something.

She's gone.

-She's gone.

-She's free and you're in pain.

-Aagh!

That hurts. Aagh!

-Where'd she sting? I didn't...

-Right underneath the fingernail,

which is something that I have always not wanted to have happen.

-She did get under your fingernail.

-Whoo!

-Is that more than the...

-Yeah, it's more than the harvester ants.

Whoo! That is, that's...

That was pain. She definitely got underneath.

There's still a great deal of mystery over why some insect

stings hurt more than others.

The pain doesn't closely match their size or how big their colonies are.

But Justin's brave work is at least a starting point

in understanding this incredibly potent insect defence system.

She won, we lost. One for tarantula hawk, zero for scientists.

-So, shall we have a look at some stingers?

-I think so.

I have this hornet here.

And, you can see just how big the body is compared to my finger.

There is something unnerving about the sight of a sting.

It is very long.

It is also incredibly sharp, so if I put this pin,

this is a dissecting pin that we use.

-Look at that.

-And guess which one is sharper? The insect wins!

-Yeah.

So that's a hornet. Let's look at a yellow jacket.

This is a smaller wasp.

-So this is just the sort of wasp in your back garden.

-That's right.

Now something like this would probably

fall at a two on the pain index, which is

kind of a run-of-the-mill sting, a run-of-the-mill painful sting.

Same as honeybees. And its stinger is retracted into its abdomen.

And whenever this thing is not using its stinger, it's held within

the abdomen for safekeeping.

So that's the stinger.

Look at that.

Along with this stinger is a whole sting apparatus,

which includes a venom gland and a venom sac

because we need the glands to secrete that venom

into the sac, and the pumping of the sac is what expels that

through the stinger into some type of predator.

And that's the venom sac.

Yeah. So we have an entire sting apparatus here.

Stings vary in shape.

The straight-needle type of wasps,

and a barbed type we see in honeybees.

The barbs mean that when the honeybee stings,

the stinger stays anchored into our skin.

This kills the bee,

but allows the venom to keep flowing into your body...

..whereas the wasp can remove its straight-edged stinger

and live to sting another day.

BUZZING

So we've looked at the battery of tools that help insects

eat and defend themselves.

But that's not the only way their basic body plan has adapted

to their advantage.

As we saw earlier,

the outer skin of the insect - the cuticle - is extremely

versatile, able to mould itself into endless shapes and forms.

This has allowed insects to evolve a vast variety of highly

specialised body parts on the outside.

Some of their most remarkable innovations are the tools

that sense the world around them.

To see those, we need a fresh specimen.

So, right here I have a dragonfly.

Yeah, and it is a fantastic specimen of a dragonfly.

They have the biggest eyes in the insect world.

In fact, they're these massive big domes

that cover almost the entire head.

And these two big globular eyes in insects are known as compound eyes.

And that is a key sort of feature

of most insects is a compound eye

which is made up of thousands and thousands of individual cylinders

with capped lenses on the top.

Up to 30,000 individual lenses in each dragonfly eye

give an almost 360-degree view

of the world around them.

So, now that we're looking

at the inside of the eye,

we see a bunch of different types of tissue.

Once you get through the soft tissue

and through some of that goop,

you can get to the actual inner surface of that eye.

Can you see these sort of glistening,

sort of diamond-like structures there?

That's clearly the lenses.

You've cleared away the gunk

-and we're seeing the lenses, reflecting the light.

-Yeah, amazing.

But the eyes are only one part

of the insect's sensory toolkit.

What we're going to look at next

is something even more impressive -

the antennae.

Antennae can detect movement, heat,

moisture and sound.

And most importantly,

they detect smells.

The moth antenna is one of the most elaborate examples

in the insect world.

Now, if we actually zoom in further,

so we'll go into about 400x,

there we go, you can actually see

hundreds and hundreds of sensory hairs

which allows the moth to detect

really small amounts of chemicals.

And that is really important,

especially for a male moth.

Because to find a mate,

he has to be able to detect only a few molecules of a chemical

known as a sex pheromone,

emitted by a female.

But insect antennae come in all shapes and sizes,

and that's because odour plays a really, really important part

in their everyday lives.

Right under our noses, in every field and forest,

there's a hidden battle taking place,

move and countermove in a life or death game of chemical warfare.

Smell is everything to insects.

Their incredible antennae put them leagues ahead of us

when it comes to detecting odours.

And they use these volatile cues to find food, a mate,

or even a place to lay their eggs,

all of which are vital to their survival.

Now, in this field,

to me it just smells a little bit earthy,

and beyond smelling like a field should smell

I can't really detect anything else.

What I can't pick up is that each plant is sending out

different chemical messages into the air.

This field is part of a project

at Rothamsted Research Station, in Hertfordshire.

And the insects that live here are some of the most studied on Earth.

Gia Aradottir studies how insects sense smell.

She works on aphids,

a pest that destroys many of our crops.

And she's enlisted the help of a natural aphid enemy

to show me how insects use their sense of smell

to work out their world.

Here, in a little tube,

is a tiny little parasitic wasp.

Excellent, I love these guys.

They actually lay their eggs inside the aphids.

-Yeah, they parasitize the aphids. That's...

-Yeah.

I can't wait to see this.

Yes, and you can see its antennae moving backwards and forwards.

-Yeah, it's really having a good forage around, isn't it?

-Yes.

And it's coming up to the aphids now. It's found...

Oh, my goodness,

it's right in there, isn't it?

It's injecting its egg into the aphid!

-Into the aphid.

-Brilliant, isn't it?

And to think that this is going on right now in our gardens,

on our rose bushes, without us even knowing.

But where it becomes even more interesting

is how the wasps find the aphids.

And this is where the insect's

incredibly powerful sense of smell comes in.

Gia's research suggests

that the wasps aren't directly smelling the aphids,

they're picking up on a completely different chemical clue.

To investigate their extraordinary ability,

the first step is to collect two plants -

one infested by aphids,

the other one free of them.

The chemical odours that they give off are captured overnight,

ready for the next stage.

Now, to see if the wasp's antenna can actually detect

a chemical signal from the damaged plant.

Gia delicately removes the antenna

of an anaesthetised wasp

and places it between a set of electrodes,

primed to pick up any electrical signals.

Now, what we've got here is a gas chromatograph,

and chromatography is a separation process.

Now, I've got two samples here.

One sample which has been collected from an aphid-infested plant,

and another sample which is from a normal plant,

a plant that isn't infested with aphids.

And we're going to inject these samples into this machine,

which will separate the chemicals into their individual components

and then blow them over the antenna of the insect.

It's like being inside the wasp's mind.

Every time the antenna senses a chemical,

we see a response on the computer screen.

These peaks form the message to the insect's brain.

-OK.

-So here's the trace from the sample that we ran,

and on the top, you can see the insect responses.

And all those little peaks are the insect responding

to the plant sample.

And on the bottom here,

-we have the chemicals coming off from the plant.

-Yeah.

This is the air from the plant

that had no aphids.

Many different chemicals pass over the antenna,

but the wasp only pays attention to some of them.

But now, look what happens

when the air from the aphid-infested plant

blows over the antenna.

New chemicals appear,

signals from the damaged plant.

And big new peaks also appear

in the wasp's response.

Its ultra-sensitive antennae

are picking up the new chemicals

and sending a different signal to its brain.

The damaged plants are sending out a distress call.

The chemicals it releases actually attract the wasps -

insects that destroy aphids.

Plant and parasite are working together to get rid of the pest.

Having cracked this chemical conversation,

scientists are now breeding wheat crops that release odours

to attract aphid predators.

If they succeed, they'll be able to reduce the use of pesticides.

As we discover more about the insect's antennae

and its incredible sense of smell,

we're beginning to put it to good use for ourselves.

One hope is that we might be able to develop mosquito repellents

based on the smells from people who rarely get bitten.

We can even train bees

to sniff out chemicals from drugs and explosives,

much better than sniffer dogs.

And the more scientists are able

to translate this hidden world of communication

below each and every leaf,

the more we might be able to turn the insect sense of smell

to our own advantage.

Our insect dissection is nearly complete.

We've gone deep inside the insect body

to reveal an internal structure

that's radically different from our own.

And we've stripped back the specialised body parts

that have made them so successful.

But there's one last challenge.

Our most ambitious dissection.

And the insect's most important evolutionary achievement.

What amazes me is how we look across the diversity of insects,

we see that most of them have wings.

Yeah, and they evolved to fly very early on,

-which has to be key to their success.

-That's right.

It enables them not only to live a lot of their lives up in the air,

but mostly spread throughout the world and dominate it.

Insects are some of nature's most agile fliers.

No man-made machine can match them.

So what's their secret?

The dragonfly is one of the fastest fliers in the insect world.

And the first thing we're going to look at

are the muscles that power their flight.

All right, so we're going to go inside the thorax.

So I'm going to take this pair of scissors

and just make some snips and see what we can find.

And you have to be quite careful,

because obviously the thorax contains massive muscles

that are used to move the wings,

it's like the powerhouse of the insect.

Now, I want to open it up

along that incision that I've made.

And as we open it there... Oh, look at that!

Oh, that is brilliant, isn't it?

You can see all those flight muscles.

So these are the muscle fibres here,

just running up and down.

So we're looking in from the top side,

so these muscles run from the top

-to the bottom of the thorax.

-That's right.

You really get a sense for how big those muscles are

and how powerful they have to be to be able to lift the insect

and sustain flight with a really high wing-beat frequency as well.

-And what a strong flier this one is.

-Yeah, absolutely.

Insects need ultra-fast wing beats to stay in the air.

So their flight muscles have to be huge and powerful.

They make up 60% of body weight in some dragonflies.

And the muscle itself is the most active animal tissue on Earth.

This means it needs a lot of air.

Now, as I'm getting through here, I'm seeing some reflective tissue,

I'm wondering if those are air sacs?

I think they might be air sacs. Give one a poke!

Wow! These are continuations of the respiratory system.

They connect up to all those tubes we saw earlier, OK.

But these are little reservoirs of air that help ventilate the body

and push air through those tubes.

Imagine the amount of oxygen you must need

in those massive muscles to keep them fed with oxygen,

keep them powerful.

These air sacs are wigging me out! These are interesting.

I rarely see these in the course of a dissection.

I was trying to figure out what "wigging me out" meant.

I think I get it!

So, we're probing down into this new tissue

and just making some pokes, which is often what a dissection is.

-You see that?

-Yeah.

So we've gone right the way through the thorax.

We've encountered massive muscles used for flight.

We've got air sacs that help the insect to fly

-because it feeds the muscles with air and oxygen.

-That's right.

We've reached the exoskeleton. It's green on the inside,

-as well as on the outside.

-Look at that!

Now, let's check out the wings

and see what the structure is all about.

And the wings are not like wings of a plane that are really smooth.

-They are actually quite ridgy, aren't they?

-They are, yeah.

And there you can see cross-sections.

It's quite interesting to see this sort of zigzag shape on the wing.

Insect wings might look like haphazard structures -

nothing like the aerodynamic design of a bird.

But insects are incredible aerial acrobats.

They can fly faster than any human can sprint,

turn 180 degrees in a tenth of a second

and land upside down on a flower petal,

all the time compensating for every tiny gust and puff of turbulence.

Human engineers have long dreamt

of being able to build miniature flying machines

that match insects for agility.

To achieve that goal, teams at Harvard University

are trying to find out more about how insect wings work.

They're starting with the most agile

fliers of them all, our old friend the dragonfly.

I'm releasing fruit flies to tempt them into a chase.

There we go.

It's chewing.

Thanks for introducing me to this. These things are amazing creatures.

Absolutely. Perching dragonflies

sit on a perch and wait for a prey to fly over them...

-Usually small insects?

-Usually small insects. Flies, some type of fly.

And insect wings don't just stay flat,

they twist and bend and contort.

What you're looking for in flight is how they do that,

and if certain contortions are important for flight.

Frame by frame, the research forensically analyses each hunt.

Lightning-quick adjustments in the angles of four beating wings

combine into a deadly flight manoeuvre.

Further down the corridor,

fellow flight researcher Andrew Mountcastle is investigating

how the structure of bumblebee wings

helps keep their heavy bodies in the air.

Andrew's experimental method begins with attaching a string of weights

to an anaesthetised bee.

Next, he glues a speck of glitter to each wing.

-That was an amazingly meticulous.

-It is!

And you created that method yourself?

-I did, yes.

-So, what's the glitter for?

So, we're using the glitter

as a microsplint to actually immobilise a joint

in the wing surface itself,

where the wing naturally hinges.

And that immobilises that joint.

Many insect wings bend during each flap.

Andrew wants to discover why this happens.

Is it just an unfortunate trade-off for a lightweight design?

Or does the bend actually help the insect to stay in the air?

Time to see if the bee has woken up.

-So, here's the tethered bee, huh?

-Here's the bee.

-We've attached the string of beads to it.

-Awesome!

-The idea is we're now going to test it.

-Can I hold it?

-Sure.

-OK.

We're now going to test its force production.

You can tell how powerful they are.

You can feel the air currents around the wing beats

as it's flying around you.

That's right, yup.

Oh, lovely!

You know, I've never held a bee on a leash before.

This is one of the most amazing things I've ever done!

Wow, it's amazing. It's just going round in circles, too, huh?

Andrew places the weighted bee in a flight chamber

to see how high it will lift the beads.

It's an experiment he's repeated many times,

with and without the glitter splint on the wing joint.

In the course of an experiment,

I do multiple load-lifting trials for a bee, and...

There it goes. Look at that! It brought all the beads up.

It went right to the light just like you expected.

It's carrying all of the beads.

That's right. So, what this means is I haven't...

Wow! What a strong bee.

That's amazing. That is amazing! That's a strong bee.

Andrew's research shows that having the wing splint

to prevent it from bending

makes the bees about 10% less powerful.

So it does seem that wing bends are a design feature with a purpose.

Elsewhere in Harvard,

teams are learning from insect flight to try and build

the world's smallest flying robots.

It's an ambitious goal.

When the time comes that these robots are fully functional,

what are the various uses you envision?

We envision these things being used for a variety of applications.

Things like search and rescue,

hazardous environment exploration.

Anywhere you wouldn't want to put a human or animal.

In situations where there might be a collapsed building,

a firefighter with a thousand of these,

and sends them in to try and find a survivor.

If 997 failed, but 3 work and sense something

then that is a success.

But as one of Rob's students shows there's still a long way to go.

So, this is the Robobee?

This is a flying Robobee that we're going to test.

Three, two, one. And, go!

Nice! Nice!

-So, it moved.

-Yeah, it did.

-It crashed and burned, but it moved?

-Yup.

The challenges of mimicking nature remain immense.

But the close examination of insect flight

is helping the team get a few steps closer.

Our insect dissection is over.

It's shown how insects have evolved to survive on Earth in ways

that are radically different to us.

And as we've taken bug bodies apart,

we've revealed that their solutions can be more effective than ours.

Now that we've explored the insect body,

we can appreciate one of the best examples

of nature's engineering genius.

And the insect's body plan may seem simple,

but in reality, it's an incredibly successful blueprint.

One that has enabled them to conquer the planet.

Most of us will never learn to love insects.

But perhaps we can learn to respect them.

Subtitles by Red Bee Media Ltd