Answer:
I believe the answer would be Heredity.
Explanation:
In the experiment, they painted yellow caterpillars green and placed them in a green environment amongst naturally green caterpillars. However, the paint only camouflaged the caterpillars into the environment, not reset their genes. So, the offspring of yellow caterpillars would most likely come out yellow (or green if it's in their genes), resulting in the yellow caterpillar offspring to be picked off more easily than the offspring of the green caterpillars.
(if that was confusing i completely apologize ;-;)