When news broke of a row between Marks and Spencer and Aldi over caterpillar cakes, everyone at Butterfly Conservation thought one thing – if only real caterpillars got as much publicity.

We weren’t alone. Soon our vice-president, Chris Packham, took to Twitter to share his outrage:

The shocking decline of the world’s wildlife has been widely reported over the past year, helped by our own president, Sir David Attenborough. Butterfly Conservation’s own research shows that two-thirds of Britain’s butterfly species and 33% of larger moths are facing devastating declines.

Keen to turn the conservation to trouble real species are facing, Butterfly Conservation’s Head of Engagement, Kate Merry, joined the Jeremy Vine show for a scientific, yet slightly tongue-in-cheek chat.

Together they discussed how anatomically accurate these cakes were: 

  • The cakes have long, cylindrical body shapes like actual caterpillars. This is because they have long stomachs to match their large appetites! 
  • Each cake has three sets of legs, which we call the ‘true legs’ of a caterpillar. However, they’re missing the ‘prolegs’, which are critical in helping caterpillars cling to its foodplant when feeding.
  • The colourful spots over the body are true to real life. Caterpillars employ all sorts of wonderful tactics to avoid predation, whether through bright warning colouration or through hairs. 
  • All cakes feature large eyes, and why caterpillars do have sensory organs for detecting light and dark, they’re much smaller and are made up of multiple structures.
  • Finally, all cakes have large grins, and while the jaws of a caterpillar are a really important feature for eating, we’re not sure we’ve seen any breakout into a cheeky grin.

Before ending the conservation, Kate said: “The cakes are caricatures of these much loved creatures, but there is an important message here – butterflies and moths are massively in decline and I would really hope that anyone that got drawn into this debate would be inspired and want to learn more about caterpillars.”

You can listen to the full interview here (around 1 hour 14 minutes in) until May 16th. 

That interview sparked an idea at BC HQ – what would an anatomically correct caterpillar cake look like? The result was our very own Clara the Conservation Caterpillar, which is based on the Comma butterfly. Its caterpillars can be found feeding on nettles in gardens and greenspaces now. If you want to make your own edible version, follow our how-to guide here.

Clara the Conservation Caterpillar

Meanwhile Chris Packham was continuing the conversation on Twitter, determined to use the story to raise funds for real caterpillars. To mark Earth Day, he posted an open letter to supermarkets in which he offered to design each supermarket a new cake, based on a real species, and asked for a profit donation to Butterfly Conservation in return. In a video he said: “Let’s not fight but unite this ecology of caterpillar cakes for the benefit of real insects.”

Later that day Iceland announced they would investigate creating a new celebration cake with over 10% of the profits going to Butterfly Conservation. 

We are now delighted to say that idea will be coming to life as Iceland launches Bonny the Butterfly cakes, of which ALL PROFITS will come to Butterfly Conservation. You can read more about Bonny here.

Bonnie the Butterfly Cakes

As well as creating a new, profitable partnership for Butterfly Conservation, the caterpillar cake wars have also helped expose millions of people to our message around protecting these declining yet critical species through both social media sharing and media coverage, including national radio stations like BBC Radio 1 and 2 and national newspapers like The Mirror and iPaper. 

We will continue to champion these wonderful creatures and encourage you to do so too. To help, we’ve put together 10 almost unbelievable facts about caterpillars (we promise they’re true though!).

10 facts about caterpillars

  • Goat Moth Caterpillars actually smell like goats. 
  • Alder Moth caterpillars disguise themselves as bird poo when they are small, but when they get larger they have warning colours and paddles.
  • Ringed China-mark moth caterpillars have feathery gills that allow them to breathe underwater and feed on aquatic plants
  • Puss Moths can squirt formic acid at attackers if provoked.
  • The White Admiral caterpillar piles up its own poo to create a defensive wall to stop it being eaten by predators.
  • The Four-dotted Footman and Dingy Footman moth caterpillars shed their skin an amazing 12 times! Most species only shed it 4-5 times.
  • Orange-tip butterflies can be cannibalistic, sometimes eating the eggs of unhatched Orange-tips.
  • Six-spot Burnet moth caterpillars feed on Bird's-foot-Trefoil which contains cyanide-based toxins. The caterpillars are unharmed by this chemical and use it to make themselves taste awful - putting off potential predators.
  • The Arctic Woolly Bear moth’s range extends to the Arctic Circle, where it survives temperatures as low as -70 below freezing. Summers are so short and food so scare that it spends about 90% of the time inactive and remains in the caterpillar stage for up to seven years.
  • And lastly, but certainly not least - the Large Blue caterpillars closely mimic the appearance and sounds of the red ant larvae and secrete chemicals that make the ants believe that the caterpillar is one of their offspring. Ants will then carry the caterpillars underground and into the nest. Once inside the caterpillar hangs out around the outskirts of the nest, where it is protected from predators, occasionally venturing into the centre of the nest to feast on ant larvae. The Large Blue went extinct in the UK in 1979, but it has since been re-introduced. You can read more about our work on this here.