Cephalopods, chameleons and some fish camouflage themselves by adapting their color to their surroundings. These animals have a system to perceive color and light independently of the eyes. Some insects, such as caterpillars of the peppered moth (Biston betularia), also match their body color to the twig color of their food plant; although this color change is rather slow compared to other animals. Until now, scientists have not known how insect larvae can perceive the color of their environment and how the color change occurs. Two theories dating back more than 130 years proposed that the color change could be caused by the diet or by the animal seeing the color. As some insects are known to be able to perceive light – but not color – by the skin, researchers from Liverpool University and the Max Planck Institute for Chemical Ecology pursued three different approaches to finally solve the riddle of how caterpillars of the peppered moth match the color of their surroundings.
First, they tested if caterpillars of the peppered moth, whose eyes were painted over with black acrylic paint, could still adjust their color to the background. The blindfolded caterpillars were raised on white, green, brown and black branches and their body color observed. Even without being able to see, the caterpillars changed color to resemble the background to the same extent as caterpillars whose eyes were not covered. "It was completely surprising to me that blindfolded caterpillars are still able to pick a branch that best matches their color. I don’t think my supervisor, Ilik Saccheri, believed me until he saw it by himself”, says Amy Eacock, one of the lead authors of the new study and currently a postdoc at the Max Planck Institute for Chemical Ecology.
In behavioral experiments, blindfolded caterpillars had the choice to move to differently colored twigs. Consistently the caterpillar rested on the twig most similar to their own color.
Read more at: Max Planck Institute for Chemical Ecology
Twig-mimicking caterpillars change their color depending on the background and move to color-matching backgrounds. (Photo Credit: Arjen van't Hof, University of Liverpoool)