Insect invasion

Why do ants always find their way onto my picnic plate?
04 August 2020

Interview with 

Eleanor Drinkwater


ants climbing on watermelon slices


If you eat your dinner outside, it’s inevitable that a creepy crawly or two - normally ants or flies or wasps - will want to get a slice of the action. Bug expert Eleanor Drinkwater told Chris Smith why...

Chris - Why have you put it under a glass?

Eleanor - Okay, we have here an absolutely beautiful common or German wasp. They're the gorgeous yellow ones that you see. And they are social creatures, and so they've actually been found to recruit their sisters, their nestmates. The best way to deal with one, if you have it at a picnic, is to get a glass and very gently put it under the glass to stop her from recruiting. If you kill her - which obviously no one should do - they release a pheromone from their head which would attract more. And if you leave her, then she will go and attract more. So really, if you put them under a glass and then very gently release them afterwards, that's probably the best way to deal with it.

Chris - That wasp then can tell its nestmates where the good dinner is to be had. And it will go and get all its mates, which is why you've sequestered it there.

Eleanor - Yes, exactly.

Chris - Do ants do the same thing?

Eleanor - Oh my goodness, yes they do. They are just gorgeous creatures. And what they do is, you'll have a scout who will go and find a food source, and go back to her nest. And as she does, she will leave a pheromone trail. So almost like Hansel and Gretel leaving breadcrumbs. But the amazing thing then is, as it recruits more ants to the source, they also lay the trail. So you get this amazing feedback loop: as more and more ants find the food source, you get a stronger and stronger signal, so as a result you get much greater attraction to the area.

Chris - I like the way you use the word feedback, because that's sort of really what it is!

Eleanor - It is exactly that! They have short-term pheromones - so that one will disintegrate very, very quickly once there's no longer food there - but they have a long term one as well, so the ants will stop being recruited but then occasionally go and check back, which is an amazing adaptation.


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