Caterpillar with a 'hat' of discarded heads uses it to fend off attackers, study finds

Scientists have found that the caterpillar may use its unusual hat to protect itself from predators

An Uraba lugens caterpillar with a tower of discarded skulls still attaches to its head (John Tann/Flickr (Published under CC BY 2.0 license))

A species of caterpillar uses a stack of its old discarded skulls as an armoured 'helmet' to help fend off predators, scientists have found.

The Uraba lugens, commonly found in Australia and New Zealand, is usually known as the 'gum leaf skeletoniser' for its habit of eating eucalyptus leaves and leaving behind only the stems.

It's also nicknamed the 'Mad Hatterpillar', for an unusual protrusion which appears while it's still a larva.

As the creature grows, it sheds its exoskeleton, like many other insects.

However, the head part of the exoskeleton remains attached to the body during shedding. Over the course of multiple sheds, the collection of heads grows, piling on top of each other and forming a horn-shaped protrusion.

It's an interesting spectacle, but there hasn't been much research into why they hold on to their heads.

These video screenshots show the caterpillar using its 'horn' to fend off an attacker (Pic: Petah Low) (Petah Low)

Now, a study published in PeerJ, conducted by the University of Syndney's Petah Low, has suggested that the 'skull helmet' may help them survive attacks by predators.

Low and her team took a number of these caterpillars and removed some of their helmets. The caterpillars then faced off against a larger insect, and their survival times were measured.

They found that caterpillars equipped with the helmets were more than twice as likely to survive their battles than those without, possibly because they used the appendages as weapons, or because they acted as a false target for the predators.

As the BBC reports, the sample size of the study was small, but it does shed some light on the behaviours of one of the most unusual insects in the animal kingdom.