To better understand the caterpillar's impressive ability to blend in, scientists at the Max Planck Institute for Chemical Ecology in Germany blindfolded caterpillars and placed them on different colored twigs. The blindfolded caterpillars were able to match their body color to that of the twig.
The findings, published this month in the journal Communications Biology, showed the caterpillars sense the color of the twig via their skin.
Previous studies have shown that sensory components in skin cells of cephalopods, chameleons and some fish power camouflaging abilities.
Until now, scientists weren't sure how caterpillars sensed color and changed their appearance. Some researchers previously hypothesized the larva change color as a result of their diet. Others suggested the caterpillars "see" colors and adapt accordingly.
The new study showed the caterpillars do indeed see color, just not with their eyes.
Scientists used black acrylic paint to block the caterpillars' vision. Even without their visions, the insect larva raised on white, green, brown and black branches adapted the appearance to blend in.
"It was completely surprising to me that blindfolded caterpillars could still change their color and match it to the background," Amy Eacock, a postdoctoral researcher at the Max Planck Institute for Chemical Ecology, said in a news release.
In a second experiment, scientists allowed blindfolded caterpillars to choose which twig they wanted to hang out on and eat the leaves of. The caterpillars chose the twigs closest in color to the color of their bodies.
Genomic analysis showed the caterpillars expressed vision-related genes in not only their eyes, but in their skin and throughout all body segments.
Researchers suggest the pepper moth caterpillars change their appearance for the same reason other animals do, to avoid getting eaten.
"We constructed a computer model that can 'see' the same way birds do, so we are able to conclude that these adaptations -- color change, twig-mimicking, behavioral background-matching -- likely evolved to avoid visual detection by predators," researcher Amy Eacock said.