"Cuspidia cernua" has bristle-like pappus on top of the fruitlets and the fruiting head remains intact, while both "Didelta"-species have chaffy pappus and the fruiting head breaks into several triangular segments when ripe.The first to describe species that are nowadays included in the genus "Didelta" was Carl Linnaeus the Younger in 1781 and he named them "Polymnia carnosa" and "Polymnia spinosa".