Erythrism or erythrochroism refers to an unusual reddish pigmentation of an animal's fur, hair, skin, feathers, or eggshells.Causes of erythrism includeErythrism in katydids has been occasionally observed. The coloring might be a camouflage that helps some members of the species survive on red plants. There is also consensus that the erythristic mutation is actually a dominant trait among katydid species, albeit a disadvantageous one, due to the overwhelmingly green coloration of most foliage. Hence, most pink or otherwise vividly colored katydids do not survive to adulthood, and this observation explains their rarity.