Dave: There’s various things we call ice ages. Strictly speaking we’re actually in an ice age now. Over the last few tens of millions of years we’ve had periods when the north and south poles have been frozen but there’ve been other periods in the Earth’s history when they haven’t been frozen at all. Over the long period we are in an ice age at the moment. People aren’t quite sure why that’s been happening. It’s been suggested it might be something to do with the Himalayas growing and altering he climate patterns in the world. I’m not entirely sure of the reasons for that. On the shorter scale there’s various other things that will affect the climate: one of them is we get cycles of exactly where the Earth’s pole is pointing. Sometimes it’s almost vertical at which point the seasons are very weak. Some times it’s keeled over more.

Chris: It’s the Earth’s tilt, isn’t it? It’s about 23.5? and it wobbles a bit, doesn’t it? The planet sort of wobbles backwards and forwards a little bit on its orbit. I think it’s over 30,000 years or something like that.

Dave: Yeah, there’s various different cycles on different forms of vibration.

Chris: Why should that make an ice age?

Dave: If you suddenly have stronger seasons that will affect it, the way water and air flows around the world. Subtle changes like that can affect the temperature of the whole world. That could be creating ice ages.

Chris: It’s a sort of positive feedback loop too, isn’t it? There’s this thing called a Milankovic cycle because where the Earth doesn’t go round the sun in a perfect circle it’s an ellipse over time you get more of an ellipse than other times. This means that more energy reaches the Earth sometimes from the sun than other times and this means the planet goes into phases of cooling and warming but once you’re into cooling it makes it easier for ice to form. Once you have ice forming it means you can have more ice. More ice reflects more light back, because it’s very white, back into space so the Earth cools a bit more and it goes into a positive feedback loop: making it very cold. When something breaks that cycle we warm up again.

Dave: That’s right and that’s why we should be so worried about human-led climate change because if we make a small effect you never know, there might be a load of other positive feedback. You might find that there’s less snow on the ground so the world heats up even more than it would do just with carbon dioxide.

Chris: It’s not just as simple as carbon dioxide in the air?

Dave: Yeah, basically it’s all just horribly complicated. 

Chris: Yes, my wife does this: chocolate! Lots of women say their intakes of certain foods change menstrually. Favourites are chocolate around day 14 and also around day 28 when you’re about to start your period. It could be that the reason for this is similar to a woman who’s pregnant craves things, allegedly. The reason that’s suggested is that if you have certain cravings it could be that your body is deficient in certain things. When you’re going to get pregnant you must make sure that you have a ready supply with lots to spare of every single kind of micronutrient you might need in the body. So if you have a craving it makes sure that you binge on lots of things at the end of the month so that when you’re about to fall pregnant your body’s already replete with everything you might need.

Dave: So it’s a bit like if you’re short of water you get thirsty?

Chris: I guess so but what you’re basically doing is overeating in preparation for a pregnancy because that way you eat lots of green leafy vegetables and you have lots of folate; you have lots of B vitamins and iron. Basically you need lots of things because the foetus is like a parasite, it’s going to steal lots of things from your body and if you haven’t got enough to spare the baby’s health can suffer. But then, so could yours.

It’s all down to an immune response. People think that when you react it’s something that the mosquito’s done to you: a bit like a sting. That’s not the case. It’s in fact what your immune systems doing that’s making the mosquito’s bite unpleasant. It’s only the females because they need the blood when they want to lay eggs, they need a high protein meal: that means you. When a mosquito bites you what it does is to insert the proboscis, their mouth parts, into the skin and they probe around until they find a blood vessel. Usually a capillary which they get into and then they can start drawing blood. To stop the blood from clotting and also to ward off your immune system while they’re doing that they inject a cocktail of about 20 proteins that go into the local tissue. They keep the mosquito having a nice dinner without harm coming to it and it also means you don’t know it’s there, immunologically speaking. The problem is that it leaves the vestiges of its saliva in the wound site. This means that when the mosquito’s flown away your immune system flocks in and begins to react to it. It’s reacting to that foreign protein and that means as you get more bites over your lifetime you get better and better at responding. That means some people get quite vigorous reactions to mosquitoes; other people the immune system tends to damp down its effect. It’s a bit like having injections to damp down allergies, for example. It just depends on how your immune system is rigged up and some people have a form of their immune system that means they react more and more vigorously, sometimes until it gets really quite severe as James was saying earlier. In other people it tends to become less severe. Maybe you’re of the latter type and your wife is of the former. I hope that answers your question.

I think there what was happening was the mosquito was providing a route of entry to a bacterial infection. It was probably Staphylococcus aureus or strep can sometimes do that.

We put this question to James Logan:

There’s lots of different species of mosquitoes and they are found right across the world. Whether they’re bothersome or not: I think they are bothersome because they all bite. If they bite humans then clearly there’s a problem but in terms of diseases they don’t spread diseases everywhere. For example, in the UK we don’t currently have diseases spread by mosquitoes.

We put this question to James Logan:

There are some compounds in Listerine such as menthol which does have a repellent effect against quite a lot of insects, actually. Perhaps it does have some sort of effect. I’m not sure if they’re saying it’s repellent by using it in their mouth or whether it’s repellent by putting it on their arms. I’m not sure but it’s certainly a new one. I hadn’t heard of that before.

We put this question to James Logan:

Well we have tested these repellent chemicals [those that people produce naturally, see James' interview] against different species of mosquito and also against midges, and currently we have some trials going on in Kenya to see if these chemicals repel ticks.  Ticks are probably more related to chiggers than to mosquitoes, because they're actually arachnids.  We don't have the results yet, but hopefully these chemicals will repel Chiggers too.

This boils down to having an 'adaptive' immune system.  A mosquito will inject a cocktail of 20 or so proteins, including something to block platelets, something to block your immune system and something to stop your blood from clotting.  The immune system is very good at reacting to foreign proteins, and the more you are exposed, the better your immune system can react.  This means your immune system gets 'tuned up' to react, and so you can get a stronger reaction more quickly.  But not everyone's immune system will adapt in the same way.

We put this question to James Logan:

There is anecdotal evidence to suggest so, however there is also anecdotal evidence to suggest the opposite, or that fatter people are bitten more than thinner or older people more than younger.  One thing we do know is that women change in their attractiveness to mosquitoes throughout their menstrual cycle, which we assume is related to hormonal changes.  Likewise, pregnant women attract more bites.

We put this question to Tony Hooper:

You certainly wouldn't want to try to grow anything under a pine tree, as they drop resins which are poisonous to other plants, as do walnut trees.

With regards arable crops, rather than gardens, wheat produces chemicals in the soil that are generally toxic both to other plants and to insects that may

attempt to colonise them.  We're working on getting this respondse 'on demand', to protect crops from attack.