Opuntia demand is making cultivation of the insect an attractive opportunity in other regions, such as in Mexico, where cochineal production had declined again owing to the numerous natural enemies of the scale insect. Apart from cochineal, the red dye betanin can be extracted from some "Opuntia" plants themselves. Fluid ("cactus juice") extracted from "Opuntia" pads and stems, especially "O. ficus-indica", is one of the most commonly used additives in earthen plaster. The flesh ("mucilage") of the cactus has been found to purify water. A project at the University of South Florida is investigating its potential for low-cost, large-scale water purification.
Opuntia readily between species. This can make classification difficult, yielding a reticulate phylogeny where different species come together in hybridization. Also, not all species listed here may actually belong in this genus, meaning that "Opuntia" is not a monophyletic group. "Opuntia" also has a tendency for polyploidy. The ancestral diploid state was 2n=22, but many species are hexaploid (6n = 66) or octaploid (8n = 88). Chollas, now recognized to belong to the distinct genus "Cylindropuntia", are distinguished by having cylindrical, rather than flattened, stem segments with large barbed spines. The stem joints of several species, notably the jumping cholla ("Cylindropuntia