Video Extras 3: Call of the Wild Transcript

Kate and Ellen look at the mosquitoes

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Follow Ellen as she makes mosquito repellent, as part of the BBC/OU's programme website for Rough Science 5

[ELLEN SIGHS, WATER SOUNDS.]
Ellen	I want to prove to Kate that I've actually made mosquito repellent. And so the easiest way to do that is to catch the larvae and the pupae of mosquitoes, raise them up to adults and then I'll make a cage full of mosquitoes. Kate can put one arm in, with the repellent. And one arm in, without. Only this arm, without the repellent, should get bit.
[BACKGROUND SOUNDS]
Kate	If you tell me that I only have to drink that twice a day and a mosquito will never bite me again, I will not believe you!
[LAUGHTER]
Ellen	I was thinking of something else!
[LAUGHTER]
Kate	Why have you got a pot full of wriggly things?
Ellen	Well, because we need adult mosquitoes, -
Kate	Hang on, hang on, hang on, hang on - no. We need a mosquito repellent, we don't need any more mosquitoes! We've got plenty of mosquitoes!
Ellen	But if I'm going to make a repellent, I want to prove to you that it works.
Kate	Right.
Ellen	Therefore I need adult mosquitoes.
Kate	Mmm-huh.
Ellen	And I want adult mosquitoes that are disease free. Because - the way you get all these diseases, malaria, falaria - all the rest of them.
Kate	Mmm-huh.
Ellen	Is when an adult mosquito bites somebody that has a disease. And then bites another person who doesn't and it infects them.
Kate	Oh right.
Ellen	Okay? So the mosquito is basically the vector of all these diseases but it's got to bit someone with it and then someone without.
Kate	Okay. Sooo - where do these things come in then?
Ellen	Well, okay. So mosquitoes have laid their eggs in the water that I collected from today.
Kate	Yeah.
Ellen	They've developed into these larvae.
Kate	Those are the wiggly ones?
Ellen	Uh-huh.
Kate	Yeah.
Ellen	And then into the pupae, which are the little comma shaped ones.
Kate	Okay.
Ellen	And in the next couple of days adult mosquitoes will emerge, come out of, the pupae - the comma shaped ones.
Kate	Yeah.
Ellen	And I'll catch them in the cage.
Kate	And they are presumably totally disease free, because they haven't had a chance to bite anybody yet?
Ellen	Exactly.
Kate	So the first person they get to bite is me?
Ellen	Exactly! So I will put mosquito repellent on one arm.
Kate	Yeah.
Ellen	And not on the other.
Kate	Okay.
Ellen	And we'll compare. And what we should find is the one with repellent - no mosquito bites…
Kate	Doesn't get bitten. And this one gets bitten to death.
Ellen	Yes. And this way we do it safely for you.
Kate	Great! I'm going to remove all their teeth!
Ellen	They don't have teeth, Kate!