A new study has shown that the caterpillars of the peppered moth are able to slowly change colour to match the twig they sit on, a phenomenon known as phenotypic plasticity.
Previous work showed that the larvae could change colour to match two coloured backgrounds, but the recently published study from the University of Liverpool has shown that they can actually select colours from a continuous scale of shades and brightness.
“Originally it was thought that they could only switch between brown and green,” says Amy Eacock, a PhD student at the University of Liverpool, and lead author of the paper.
“After presenting the larvae with a range of artificial twigs of different colours also varying in brightness, we found that they can match colours in between green and brown, as well as black and white”.
The story of peppered moths has become a famous case study in natural selection, where darker morphs of the adult moth survived better in industrial areas where trees were covered in soot.
The new research indicates the larvae of this species have taken predator avoidance to the next level by being able to change their coloration.
Colour plasticity has been observed in a variety of animals from amphibians to cuttlefish, however the peppered moth is the first species of Lepidoptera (butterflies and moths) known to use this strategy to avoid being eaten.
Though the full extent of the camouflage capabilities of moths is currently poorly understood, Eacock is confident there is much more to be discovered.
“We also think that there is something unusual about the way these caterpillars perceive their visual environment, but that’s coming up in the next paper!”