Iridoids are a type of monoterpenoids found in a wide variety of plants and some animals. They are biosynthetically derived from 8-oxogeranial and are typically found in plants as glycosides, most often bound to glucose. Structurally, they are bicyclic cis-fused cyclopentane-pyrans. The iridoids produced by plants act primarily as a defence against herbivores or against infection by microorganisms. The variable checkerspot butterfly gets iridoids in his diet and they act as a defence mechanism against avian predators. Humans and other mammals often perceive the iridoids as having a deterrent bitter taste.