Following anti-tourism protests across popular Spanish cities and towns, we are looking for the world's most unwelcome visitor. Our panellists (and producers) are pitching their terrible tourists to see who really is the worst of them all. Some of our contenders include... The wild boars who's unanticipated vacay to Rome has gone on for so long and caused so much carnage that researchers are putting them on birth control. The microbes potentially hitching a ride to the moon via space probes and astronauts' poo The multi-destination parasite who wreaks havoc as it interrails through snails (castrating them on the way), frogs (making them spout multiple limbs) and birds. But there are some instances when tourists can be a good thing - and this is especially the case in the human body when we want to grow a baby. How is in that we are able to protect what should be an 'unwelcome visitor' from a hyperalert, hostile immune system? Our expert Edward Chuong explains. Plus, we uncover the DNA origins of the world's most popular coffee bean, hear the freeloading activities of the male angular fish, and read out a selection of your wonderful emails. Presenter: Caroline Steel Panellists: Phillys Mwatee & Christine Yohannes Producer: Julia Ravey Production team: Emily Knight, Noa Dowling Studio manager: Emma Harth
This summer, I've been endlessly irritated by flies circling round the middle of my kitchen.
I often find myself staring at them, wondering what on earth they're doing.
After years of puzzling, I finally got a chance to solve the mystery when I met a scientist who did a whole PhD on this behavior.
He filmed circling flies in slow motion, only to reveal that they aren't actually flying in circles, they're flying in rectangles and all the flies are male.
They're fighting to be the only fly in the rectangle because at some point, a female will fly in above and the winner will swoop up and mate with her.
Mystery solved.
The flies are still in my kitchen, though.
I'm Caroline Steele from the BBC World Service.
This is unexpected elements.
Joining me in my flies, we have health journalist Christine Johannes in Addis Ababa, Ethiopia.
Christine, you've spoken to us from all over the world, but right now you're back home, right?
Yes, I'm back for the second time this season.
And in Nairobi, in the BBC's Kenya office, we have journalist Phyllis Muati.
Lovely to see you again.
Phyllis Hujian, Bo Karoline.
Lovely to see you again, Phyllis.
Are circling flies a problem for you too?
Currently, no.
But in hotter and warmer months, they really are a nuisance, especially house flies and fruit flies.
But right now it's very cold in Nairobi, so that's not happening.