Someone asked, so here it is: The key for identifying Opuntia species
Not all species, but a fair number. Feel free to merge this with the parent thread if you like.

To my knowledge, no Opuntia species has ever been confirmed as an hallucinogen either alone or with MAOI. The possibility remains that some could find utility in mixes with a different hallucinogenic component tho. As various plant parts of various species are used as medicine its conceivable it could be used in medicinal hallucinogenic preparations to add activities such as antioxidant, anti-hyperglycemic, anti-inflammatory, a urinary tonic, etc. Preparations of flower or fruit have been used and clinically confirmed as improving inflammatory (CRP) mediated side effects of alcohol intoxication such as nausea, dry mouth, and anorexia [1] It might be interesting to experiment with fruit and flower of various Opuntia in combination with hallucinogenic preparations.