Previously grown as Nopalea cochenillifera

This is the host to the cochineal scale insect, Dactylopius coccus. The insect produces the scarlet dye carminic acid, which has a chemical structuyre similar to alizarin - see Rubia tinctorum. The carboxylic acid group in carminic acid makes it bond well with protein fibres, although aluminium slats can be used as a mordant to give better colour fastness.