This caterpillar uses a pile of disused heads as a sword
If I were to walk down the street wearing a Jenga tower of human skulls on my head, I don’t imagine I’d run into many people wanting to start a fight. The same, it seems, is true in the animal kingdom, where the Uraba lugens caterpillar pulls off a similar party trick to keep predators at bay.
It’s not quite the same thing – and not just because my jaunt down Oxford Street would probably be cut short by a police intervention. The caterpillar in question uses its own discarded heads, rather than other caterpillars’. Which is far less creepy.
Basically, when Uraba lugens’ (“gum leaf skeletoniser” to its friends – no, really) head grows, the molted skin is discarded. Rather than just letting go and moving on, this particular caterpillar is a hoarder. If you or I tried to balance skulls on our heads, we’d quickly fall foul to gravity, but researchers believe that tiny hairs help the stack stay stable.
Why would the caterpillars want to keep their old heads? To try and answer this question, a new study put the gum leaf skeletonisers in the gladiatorial arena of the Petri dish. Its opponent: a predatory stink bug, which has a pretty nasty attack of its own – it injects poisonous toxins via its pointy proboscis.
The fight, predictably, didn’t end well for any of the caterpillars, but tellingly those with the macabre head gear lasted markedly longer than those without. Death mercifully came to the unprotected caterpillars after 14 seconds, while those with literal skull caps survived for around two minutes each time.
Why? Because the stinkbug was wasting its time attacking the decoy heads, which were obviously unaffected by the toxin. The caterpillars were also able to swing their head stack in a sword-like manner, deflecting the stinkbugs’ attacks.
You can see more clips of the fights in the video below, but evolutionarily, it seems the strange hobby of collecting old body parts may have its uses after all.
Image: John Tann used under Creative Commons