Much like chameleons and certain fish, a new study now finds that caterpillars of the Peppered Moths (Biston betularia) also can change their body colour, matching it to the twig colour of their food plant. However, the change in colour is slower compared to other animals. Notably, scientists have not known, till now, how insect larvae can perceive the colour of their environment and how the colour change occurs. However, 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 colour of their surroundings.
According to the researchers, they first tested if caterpillars of the peppered moth, whose eyes were painted over with black acrylic paint, could still adjust their colour to the background.
Thus, the blindfolded caterpillars were raised on white, green, brown and black branches and their body colour observed. The study experts found that even without being able to see the colour, the caterpillars changed colour to resemble the background to the same extent as caterpillars whose eyes were not covered.
Speaking about it, one of the lead authors of the study, Amy Eacock said, "It was completely surprising to me that blindfolded caterpillars could still change their colour and match it to the background. I don't think my supervisor, Ilik Saccheri, believed me until he saw it by himself."
In the second behavioral experiment, blindfolded caterpillars had the choice to move to differently coloured twigs. Consistently the caterpillar rested on the twig most similar to their own colour.
Finally, in the third approach, they examined in which parts of the body, genes related to vision were found. They saw them not only in the head of the caterpillars, where the eyes are, but also in the skin of all body segments.
Speaking about the same, Hannah Rowland, second lead author of the study spoke about one visual gene which was even more expressed in the skin than head and said that they assume it is this gene that is involved in the perception of background colour-skin.
According to Rowland, one of the major challenges animals face is how to avoid being eaten by predators. She further added, "Numerous species have evolved camouflage to avoid being detected or recognised. A considerable problem, however, is how prey animals can match the range of visual backgrounds against which they are often seen. Colour change enables animals to match their surroundings and potentially reduce the risk of predation."
According to researchers, Caterpillars with better colour-sensing may have been eaten less by birds, while birds with improved vision may prey more upon these larvae, continuing the evolutionary predator-prey arms race.