Erythropterin is a Pterin derivative that belongs in a group of heterocyclic compounds that are frequently found in biological systems. Pterin derivatives are responsible for the characteristic warning coloration of some Heteroptera and other insects, signaling noxiousness or unpalatability and are used to discourage potential predators from attacking[1].
[1]. KrajÍ?ek J, et al. Capillary electrophoresis of pterin derivatives responsible for the warning coloration of Heteroptera. J Chromatogr A. 2014 Apr 4;1336:94-100.