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Purple prickly pear

The purple variety is called the Santa Rita Prickly Pear. Those white fuzzy patches on the pad in the middle are the nests of the cochineal bug, which produces a bright carmine dye. According to Plants of Arizona, the purple variety is particularly susceptible to this bug. For the insect, it’s not a dye but an ant-repellant.

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About Bill McCallum

I was born in Australia and came to the United States to pursue a Ph. D. in mathematics at Harvard University, met my wife, and never went back. I am a professor at the University of Arizona, working in number theory and mathematics education.


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