Social Insects, Biting Bugs and a Potted History of Honey
This week we get bitten by the bug as Ian Burgess talks about the nasties that nibble us in the night, William Foster discusses social insects and how individuals in colonies communicate, Bee Wilson describes the useful properties of honey, and Megan Frederickson reveals how Amazonian ants use formic acid to create Devil's Gardens.
In this episode
Catch The Buzz About Nature's Elastic Band
In a move that could signal an end to bad backs, writing in last week's edition of Nature a team of Australian scientists led by the Queensland researcher Dr Chris Elvin have successfully copied the insect gene that enables the wings of a bee to flap at least 500 million times during its life, and has catapulted "frog hoppers" into the Guinness Book of Records as the world's greatest jumpers. Resilin is essentially Nature's elastic band. It's extremely tough, it can store energy like a spring, which is how blood-hungry fleas bounce from one tasty host to another, and it can expand and contract very fast withour wearing out. Until now it has been impossible to produce this substance artificially, but Chris Elvin's team have successfully persuaded bacteria to do it for them. They suggest that the protein's resilience means that it might make a perfect replacement for spinal discs. And since we move out backs only about 100 million times over the average human lifespan, if it lasts as long as it does in a bumblebee, we should be laughing, rather than grimacing!
The Good Cop With a Sting in his Tail
Scientists in America have been training 'sniffer wasps' to sniff out explosives, dead bodies and mouldy corn. They trained parasitic wasps, living in a small cup called a 'wasp hound', to respond to certain smells by using a food reward. After a five minute training session, wasps were put into a wasp hound detector and presented with the evidence - potentially mouldy corn. If the wasps became agitated, researchers knew that the wasps had discovered a batch of mouldy corn. Besides fungus, these brightly coloured coppers have also been trained to detect explosives and dead bodies. Maybe in future airports will be hiring sniffer wasps instead of sniffer dogs.
- Biting Insects
Biting Insects
with Ian Burgess from Insect Research and Development, Cambridge
Kat - Why do horseflies hurt so much when they bite you?
Ian - Normally, horseflies bite very large animals such as deer and cattle. These animals can't turn round and smack them one. Therefore they don't really have to creep up on you. They have very large mandibles and actually make a big hole in you! They then lap the blood up as it starts to flow out. With a thick skinned animal like a cow, they have to chew quite a big hole, but they don't adjust this when they're biting human skin. This means that it hits the nerves rather quicker.
Kat - Is it true that you can get bitten by spiders in the UK, because I'm sure I've been bitten at night by spiders.
Ian - there are several spiders that can bite in this country. There are a couple that live mostly in the south of England that are moderately venomous. Even the big house spiders can bite, particularly if you annoy them. In fact one of the house spiders we have in this country has been accidentally imported to the western seaboard of the USA, where it's spread further north every year. It's known as he hobo spider as it catches lifts on trains. Now it's reached Alaska, where it isn't nice to live outdoors, it lives in houses all the time. As it's quite venomous, there are lots of websites looking at the hobo spider and how it attacks people.
Chris - Do you know roughly how many of these spiders get shipped in each year?
Ian - Oh into this country, it's probably thousands but most of them don't survive. They come on chilled ships or aeroplanes, and it's too cold for them. But some of them do creep through. The ones that we get are mostly widow spiders.
Chris - They're lethal aren't they?
Ian - Only if you're under five or have a weak heart. Mostly they'll just make you feel really awful for about 24 to 48 hours.
Chris - What actually is it in the venom of a spider that actually makes those symptoms?
Ian - Widow spiders have what is known as a neurotoxic venom, which is one that attacks the central nervous system. It gives you shakes, tremors, vomiting and things like that. Some of the other spiders have what is called a cytolytic venom, and that causes tissue to break down, so you get a really nasty gangrenous reaction.
Kat - How aggressive are insects generally? We all know not to annoy a wasp because it'll come and sting you, but are there any really aggressive insects in the world?
Ian - Well I would probably say that bees are worse. Wasps are actually quite docile, except perhaps for the Asiatic hornet.
Bee - I think that William would know more about the Africanised killer bees, but domestic bees vary hugely. You can get all sorts of bees specially bred for different temperaments.
Chris - Is it true that when you blow smoke into a bee hive that it genuinely calms them down?
Ian - Oh yeah. Their response to a forest fire is to engorge on their honey so that they can then move out and save some of their food reserves. So if you blow the smoke in, they think it's a forest fire, they fill themselves up and get a bit dopey and drunk. So that's why they're less likely to be aggressive.
Chris - So that's a bit like us when we've had a massive Sunday lunch and just want to slump in the armchair.
Ian - Pretty much so, yes.
- The Horticulturalist Behind Devil's Gardens
The Horticulturalist Behind Devil's Gardens
with Megan Frederickson from Stanford University, California
Chris - Now tell us about your story.
Megan - I've been studying a phenomenon called the devil's garden.
Chris - That sounds scary. What's a devil's garden?
Megan - A devil's garden is a very unusual kind of growth of trees in the Amazon. They are very unusual because in this growth of trees there is only one, or at most a few species of trees. This is very unusual for the rainforest because usually there are many species of trees growing in a very small area.
Chris - So how big do these gardens get?
Megan - They get to be about 1300 square metres, which is about half the size of a soccer field.
Chris - That's a pretty big area to have just one kind of tree. What kind of thing was going through your mind when you were thinking what might be causing this?
Megan - Well there were basically two ideas about how it is that devil's gardens are formed, and how it is that there's only one kind of tree there. The first idea proposed was that maybe the tree that grows in devil's gardens produces some kind of toxin in its roots.
Chris - That kills everything else off?
Megan - Yes, that kills everything else off, and prevents other trees from growing in the area.
Chris - How did you prove that that wasn't the case then?
Megan - I did an experiment where I planted a bunch of saplings of a very common Amazonian tree species inside and outside devil's gardens.
Chris - So these are trees that are not normally found in devil's gardens?
Megan - That's correct. It was a different kind of tree species.
Chris - And don't tell me, they all died.
Megan - No actually they didn't. When I planted them inside devil's gardens I did two things. One was that I planted them as is, and I also planted some with a kind of sticky goo round the bottom to prevent insects from climbing up the trunks and getting at the leaves.
Chris - Right, and which ones survived.
Megan - Only the trees without the sticky substance around the trunk died after a couple of days in a devil's garden. So I showed that some kind of insect was attacking the trees in devil's gardens.
Chris - And what was that insect then?
Megan - It turns out that that insect is a species of ant.
Chris - So these ants are selectively homing in on plants they don't want and killing them.
Megan - That's correct.
Chris - How are they doing that?
Megan - That is something the is really fascinating. What they do is start by crawling up the tree, and then each worker ant starts by biting a small hole in the leaf tissue or the stem tissue with its mandibles, or jaws. Then it flips its abdomen underneath its body and it sticks the tip of its belly into the hole it's made and it releases a few drops of a very nasty chemical substance called formic acid.
Chris - And this just poisons the tree?
Megan - Yes.
Chris - But how does the ant know one tree species from another?
Megan - Well that's an excellent question. The tree species that they don't kill turn out to have a very special relationship with the ants. The ants live in the hollow stems of this tree species and make their nests in them. I first thought that they decided by seeing whether a tree had any good nesting space for them. And I did an experiment, and it turned out that that's not true.
Chris - So how do you think they do it then?
Megan - My best guess is that they distinguish between the tree that they live in and all the trees that they kill by some sort of chemical cue. They basically smell the difference between these types of trees.
Kat - So it's like recognising your favourite food by the smell of it. Can I also just ask really quickly, why are they called devil's gardens?
Megan - They're called devil's gardens after an Amazonian legend, which says that these gardens are cultivated by an evil forest spirit. So that's how they get their name.
- The Useful Properties of Honey
The Useful Properties of Honey
with Bee Wilson, historian, food columnist and author of The Hive
Kat - So what first interested you in bees? What do you find so fascinating about them?
Bee - Well I have to admit that I absolutely love honey, and I am a food writer. It seems quite silly someone called Bee writing a book about bees. That was actually part of it. As a child I was often given little presents with pictures of Winnie the Pooh and honey on them. As I got older, I suddenly realised that there's a huge amount of sentimentality for bees that doesn't really exist for any other insect. We certainly don't feel it about wasps or ants. When I grew up and became a historian, I found out that we used to think, and still do think, all kinds of weird passionate things about bees that again I don't think apply to other insects.
Kat - They are fascinating animals. We've heard a little bit about how insects are useful, but could you talk a little bit about honey? Does honey actually have any useful properties?
Bee - It tastes delicious and therefore makes us feel good! It is a sugar, but it's probably a bit better for you than refined sugar because it has a slightly different composition of glucose and fructose in it. Over the years, all kinds of claims have been made about honey. People have said that it could cure baldness if you smeared it on the top of your head, that it could cure infertility, and all kinds of other things. A lot of it is rubbish, but it turns out that there are quite a lot of things it can do. It's been used for years as a wound dressing, and scientists in New Zealand are working on that. They are especially looking at manuka honey, which comes from a tree that is the same as the one we call tea tree, and that has been proved to have higher antibacterial properties than other honey.
Kat - Does it have the chemicals from the tree in the honey, because you get different types of honey, such as heather honey, don't you?
Bee - You do. They smell different and they have different textures. Heather honey is amazing. It's called fixatropic, which means it has the same consistency as non-drip paint. It's all to do with the different chemical make up of different nectars.
- Social Insects And How They Communicate
Social Insects And How They Communicate
with Dr William Foster from the Department of Zoology, University of Cambridge
Chris - Most people are probably fascinated to see how organised colonies of ants and bees are. How do they actually talk to each other and decide who does what?
William - Well I think this shows that actually ants do have a big intellect. We said earlier that wasps and things can be trained, so insects do have massive brains and they can do all sorts of things. They organise their colonies by a system of chemicals, which they release to each other and keep in touch about what's happening in the colony. For example, if the queen starts to fail, then the workers can pick this up and react accordingly. They don't smell her so much.
Chris - When you say fail, do you mean get old?
William - Yes, they get old and weak, and not able to pump out as many babies for them all. They pick that up and start producing new individuals, and new reproductives.
Chris - So how do ants, say, get told today that they're going to go and get food and come back and tell everyone else where the food is? How is that achieved?
William - Well I think it's a sort of stable system. Let's say to start that they're all feeding. Then if suddenly more food comes, more of them will go and come back, and they'll all get agitated, making even more of them go and get food. So there are very simple rules that they are following; nothing very complicated. If they come back and they're full of food, all the other ants will pick that up and follow them.
Kat - How do they know where to go? You see them marching in a line around the edge of the kitchen. What are they following?
William - It varies, but in ants there's a trail which they leave. Again it's a chemical smell that they smear along the ground and all the ants can follow that and see where they've been.
Kat - Can you rub it to get rid of it?
William - Yes, maybe if you just brush it away, they might not go there. Sometimes the ants just do it individually, by looking at the sun or at landmarks, so they don't need a chemical trail. So if you brushed in that case, it wouldn't make any difference. You'd have to have the right kind of species if you wanted to brush it away.
Chris - I was reading the other day about bees, and they have a pecking order in the hive. Some bees that are in charge of housekeeping duties are confined to barracks, and as they mature, they're allowed to go out and collect things. How's that actually achieved? How do they decide when they've become old enough to get more responsible duties?
William - Well the general idea is that as you get older, if you're a bee, you get to do different things. So you start doing things near the queen, which is where you're maybe born originally and you help the queen. This is certainly true if you're an ant. You help the queen and move eggs, and then as you get older, you move further and further away from the centre of the hive and then eventually, towards the end of your life, you do risky things. It would be a bad idea if you're a young be to go out fighting because you're liable to die. So it's only when you're quite old that you go out and fight. This is opposite to what we do in humans when we send young people out to fight.
Chris - It's not just bees and ants that are social in this way because spiders are too aren't they?
William - Yes there are a lot of social insects. Spiders are only just social. You don't get worker spiders as far as I know that don't reproduce. I think the real test of sociality is is there a group of individuals which are sterile, which do not reproduce. Aphids are like that rather surprisingly. There are some aphids, greenfly, which are permanently sterile and just fight and don't do anything else.
Chris - I know a few people at college from my medical school days who were a bit like that.
William - What, permanently sterile?!
Chris - No, just falling out and fighting all the time.
- Is it true that talking to plants helps them grow better?
Is it true that talking to plants helps them grow better?
In 1948, a man called Gustav Fechner thought that plants had emotions, so talking tot hem would help you get in touch with your plants and encourage them to grow. Studies also show that music might help plants, especially classical music. However, rock music is supposed to make plants wither away. But apparently this is not the case. If you talk to your plants, you're giving them lots of attention and probably looking after them a lot better. There's also some scientific truth in it. If you got right up close to your plants and talked to them for several hours a day, they'd probably get more carbon dioxide.
- Are fluorescent lights more efficient than incandescent tungsten lamps?
Are fluorescent lights more efficient than incandescent tungsten lamps?
The way fluorescent lights work is that they contain gas at a certain low pressure, and you fire that gas up by putting a high frequency electrical signal through there. The electricity passing a current through the gas excites the atoms and they lose some of their electrons. The electrons are flicked up to a higher energy level, and then they fall back again to a normal energy level. When they do so, they emit some UV light, which strikes a phosphor, which is on the inside of the tube. That phosphor turns those UV rays into a second form of energy, which is visible white light. This process is very efficient. Tungsten light bulbs work by heating up a piece of metal in a tiny filament until it becomes white hot. Only about 20% of anything they actually use is turned into anything useful.
- What's the difference between fuel sold in the winter and in the summer?
What's the difference between fuel sold in the winter and in the summer?
Fuel is different between winter and summer because the conditions it is used in are different. The starting conditions are particularly different, as engines have to get going from a much lower temperature. What you can do to winter fuel is add chemicals that make the petrol vaporise at a lower temperature, which facilitates cold starting. Using a better mix makes it easier for your car to start on a very cold day.
- Why can't I grow a new finger?
Why can't I grow a new finger?
That's a really interesting question, and it explains why humans are different from things like amphibians. If you cut the tail off a newt, newts can grow back their tails and their limbs. But human cells can't do this, mostly. We do have some cells within our bodies such as in our brain and cells in our skin that do keep on growing. That's why we can heal small wounds. But with something like a finger, there are so many different types of complicated cells, that our stem cells are not capable of making them. They just don't have it left in them to do it. We basically don't have the genes and genetic programme to do it.
- Does saliva have healing properties?
Does saliva have healing properties?
Yes, saliva does have some beneficial properties because it contains a number of proteins. Those proteins include antibodies, and we make a lot of antibodies when we are infected with various things, and they can mop up bugs and viruses. That's one bonus of saliva. It also contains another protein called lysozyme, and this is an enzyme that can break down some types of bacterial cell walls. When you lick something that has bacteria on it, those lysozymes attack the bacteria and help to neutralise them. Antibodies and lysozyme are also in your tears. Also in your saliva is mucus. Mucus is a protein that forms a sort of meshwork, and it traps things and stops them moving away too fast. So yes, saliva does have a medicinal role too.
Why does the flu jab only last one year?
The flu is a nasty virus. It tends to make mistakes when it copies itself, so that when the virus made in one person is passed onto someone else, it is slightly different to the one you were infected with. As the flu goes around the world every year, by the time it's got back to where it started, it looks very different from the version that was here before. When you get the flu the next year, your immune system cannot recognise it because it looks completely different. So a vaccine is only good until the flu changes, which is why you have to have a new jab every year.
- Why do insects have more legs than humans?
Why do insects have more legs than humans?
I think if you're small animal, it's quite hard not to fall over. So if you have a large number of legs you can stay on the ground more of the time. So essentially, insects have more legs than humans because if they had less legs, they would fall over very easily.
- Is propolis beneficial for rheumatoid arthritis?
Is propolis beneficial for rheumatoid arthritis?
Actually rheumatoid arthritis is the immune system attacking joint tissue, which it shouldn't do. So it's the immune system going out of control. I don't think it would do him any harm at all. Whether it would do him any good, I couldn't really say. There have been many claims made, but not many have been substantiated I don't think.
- What is the most powerful insect, and can fly the furthest?
What is the most powerful insect, and can fly the furthest?
In a single stretch, I probably think it's the dragonfly. These animals spend most of their life on the wing and they just come down to settle to look to see where the prey is. They can fly for quite long periods. There are many insects that have been found several hundred miles off of the coast, so lots of things can fly for long distances if they get caught by the wind. I think the insect that can fly the furthest under its own steam is probably the little biting black flies, which you get in West Africa. They can do 300 kilometres while looking for prey. The most famous migrating insect is the monarch butterfly, which flies across North America to special roosting sites in Mexico. That's a very famous, powerfully flying migrating butterfly.
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