Most animals that change color to match their surroundings can see what these surroundings look like. But the peppered moth caterpillar can do this with its eyes closed, according to a new study, and scientists have figured out how.
Researchers raised more than 300 larvae of the peppered moth (Biston betularia) in the lab. After the caterpillars grew up a bit, the scientists placed them in different boxes containing artificial sticks painted black, brown, green, and white (pictured). Some of the larvae were blindfolded using black paint.
The blindfolded caterpillars changed their entire body color to match the stick they were sitting on as well as their seeing counterparts did, the team reports in Communications Biology. When the researchers placed the caterpillars in boxes containing different colored sticks, about 80% of the larvae, both blinded and sighted, chose to rest on sticks that matched their body color.
On closer examination, the scientists discovered the peppered moth caterpillar turns on genes responsible for vision not only in its head, but also in its skin. The bugs have rather poor eyesight and sit on branches with their heads tilted away, so their eyes may not always be on the branch. This, along with their very slow color change can make them sitting targets. It’s likely that the caterpillars evolved such a dual mechanism of color sensing to give them a leg up in outwitting their hunters, the team speculates.