Do butterflies taste with their feet?

RSPB England's, Beth Markey, explores one of the more unusual side of nature...

Red admiral by Chris Gomersall

If you could choose to taste with any part of your body, your feet would probably be last on your list, right? We can’t imagine that clammy socks and floor tiles have anything on a mouth-watering chilli con carne.

But for some animals, tasting with body parts other than a tongue gives them a distinct evolutionary advantage. Butterflies are one such example. As you might have guessed from the title, their taste receptors are located in their feet. And if that’s not enough to digest, get this …butterflies also smell with their feet too…

Eating and tasting are not one and the same…

Firstly, it’s important to make it clear that butterflies don’t eat with their feet. They simply taste with their feet. To a human, whose ability to eat and taste comes from one orifice, this can seem somewhat mystifying. But it serves a very useful purpose.

Instead of consuming their meals through a big, tooth-lined mouthpiece, like us, butterflies use a straw-like tube, known as a ‘proboscis’.

Painted Lady, Graham Madge

See that long object that looks a bit like a spider leg coming out of the above butterfly’s mouth? That’s a proboscis and it’s used to suck up nectar – a butterfly’s main source of food. You see, aside from being a glamorous addition to the landscape, butterflies are important pollinators too, carrying pollen from plant to plant in their mission to quench their hunger.

Unfortunately, a butterfly’s proboscis doesn’t house taste buds. It’s tiny and, when out of use, it stays safely curled up under the butterfly’s chin. This poses a challenge as it’s important for them to be able to distinguish between a butterfly delicacy and, say, sap or cuckoo spit,  So instead, it uses taste receptors, located on its feet to determine whether a substance is edible or not.

The sciencey bit

Given the seeming absurdity of the idea that any animal can taste with anything other than its mouth, it wasn’t until the late 19^th Century that researchers began to give weight to the idea. In fact, it was originally assumed that butterflies tasted through their antennas or ‘palpi’ – sensory appendages on their faces. These days we know that our ancestors weren’t entirely off base as palps do play a significant role in helping butterflies detect food.

In actual fact, butterflies’ taste through ‘chemoreceptors’ in their feet. As soon as they land on a plant, they can detect whether it is sense sweet, bitter, sour and salty. Interestingly enough, if a butterfly lands on you, it’s normally a sign that they have sensed the sweat on your skin (and not that you’re Disney royalty – sorry...).

  
Peacock butterfly, Graham Madge

Yet, butterflies use taste for more than choosing a snack. Their taste receptors play a big part in choosing a mate and finding a host plant for their eggs.

After mating, a butterfly will hop from leaf to leaf, tasting each one to ensure that it is the right place to lay her eggs. The second her caterpillars hatch, they are ready to eat voraciously in order to reach the next stage in their life journey – the chrysalis.

It’s not just butterflies either

Just when you thought insects couldn’t get any weirder, it turns out that there are lots of creatures who use their senses in very different ways to us. Take crickets and locusts. In order to test the quality of dirt before settling on a location for their offspring, they use taste receptors in their ovipositor (a tubular organ that deposits eggs).

And kicking it up a notch in strangeness, there are some species of moth, like the looper moth, that hear with their bellies. This is used to detect the echolocation of bats hunting them. But the contender by far has to go to yellow-swallowtail butterflies, who not only taste with their feet but can also see with their genitals…

You heard it from us – Nature. Is. Weird.

Find out more about the butterflies you can see in your garden here.