Polyphenism
Polyphenic pigmentation is adaptive for species which reproduce several times a year. Different pigment patterns provide camouflage throughout the seasons, and alter heat retention as temperatures change. Because insects cease growth and development after they are adults, their pigment pattern is set in adulthood. In the case of the peppered moth, Biston betularia, the caterpillars are polyphenic. Their trigger is switched by the colour of the plants they are eating: see this.