Causes of erythrism include
- genetic mutations which cause an absence of a normal pigment and/or excessive production of others
- diet, as in bees feeding on "bright red (colored) corn syrup" used in maraschino cherry manufacturing 
Erythrism 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.
- Heterochromia iridum
- Red hair
- Dariusz Bukaciński and Monika Bukacińska (1997), "Production of Erythristic Eggs by the Black-Headed Gull in Poland", Willson Bull. (Wilson Ornithological Society) 109 (1): 177–182, JSTOR 4163790
- Helen Hays and Kenneth C. Parkes (1993), "Erythristic Eggs in the Common Tern", J. Field Ornithol (Association of Field Ornithologists) 64 (3): 341–345, JSTOR 4513830
- Sarah Schmidt, Helping Brooklyn's Red Stingers Get Off The Juice, onearth.org, December 1, 2010
- Gary Noel Ross (1 June 2003), "Pretty in pink", Natural History
- Stone, Daniel (March 2013). Easier Being Green. National Geographic. p. 19.
- The Mystery of the Red Bees of Red Hook, New York Times, November 30, 2010
- Rare Pink Katydid Discovered in Northern Illinois, Chicago Tribune Local, August 10, 2011
- Another Nice Example of Erythrism: Grasshopper, August 28, 2009
- Erythrism: Grasshopper in New Zealand, Rod Morris, 2010
- Pink Animal Amazingness, Paula Kashtan, lemondrop.com, December 18, 2008