If, at various stages of your life, you needed to do something with your old head, how would you dispose of it? Deep in the eucalyptus forests of Australia lives a caterpillar with an answer to this rather unique question. The caterpillar keeps its old heads and with them forms a glorious but rather morbid top-hat.
Uraba lugens is the larvae of the gum leaf skeletoniser moth, though some have called it The Mad Haterpillar, which seems a wonderfully appropriate alternative name. Its towering headwear stems from the caterpillar’s need to grow. As it sheds its exoskeleton, for some reason it keeps its old head, and it is added to the teetering collection.
What is the benefit? This peculiar head-stacking may be a cost-effective form of defence, say researchers from the University of Sydney. Rather than invest in other costly strategies – deadly toxins or unpleasant smells, for example – why not just use some cast-off body parts to act as a distraction? A recent study suggests it does sometimes work. The protruding pile of heads appears to act as a false target, and caterpillars wearing the hat survive more often while those without succumb to predators. While results suggest it isn’t anywhere near a perfect defence, and isn’t going to keep motivated predators at bay for long, there does indeed seem to be at least some benefit to keeping one’s (old) head.
Originally published as News In Brief in Biosphere Magazine Issue 15.
Low, P, McArthur, C, & Hochuli, D. (2016) Head capsule stacking by caterpillars: morphology complements behaviour to provide a novel defence. PeerJ. 10.7717/peerj.1714