A British bid for red dye left Australia smothered in prickly pear
In 1788 Captain Arthur Phillip picked up cactus plants crawling with cochineal insects in Brazil, hoping to break the Spanish and Portuguese grip on red dye for British uniforms. The insects died off in Australia, but the cacti flourished and eventually overran about 100,000 square miles of the east until a moth was brought in during the 1920s.
Cochineal is a small scale insect that lives on Opuntia cacti across the Americas, piercing the pads with a beak-like mouth and sipping sap. Wingless females, about 5 mm long, sit almost motionless under a waxy white coating, yet crush one and the inside is dark purple. That colour comes from carminic acid, which puts off other insects and makes up 17 to 24% of the dried body weight.
Newly hatched young, called crawlers, spin long wax threads and wander to the edge of a pad, where wind lifts them to fresh cacti. Males grow wings, stop eating once mature and live only long enough to mate, so they are rarely noticed. Farmers either seed cacti with infested pads or hang little baskets known as Zapotec nests holding fertile females, then hand-pick the insects at around 90 days old in a slow, labour-heavy harvest.
Mixed with aluminium or calcium salts, the acid becomes carmine. Spain began importing it from the New World in the 1520s, replacing the Mediterranean kermes dye, and it became a major colonial export. Synthetic dyes such as alizarin pushed it aside in the late 19th century, but worries about artificial additives brought it back, and today it colours foods and lipstick as E120. Peru is the biggest producer, ahead of Mexico.
Introductions still backfire. Cochineal was brought to northern Ethiopia in the early 2000s for farming; when the business closed after a community dispute, the insect kept spreading, and by 2014 it had infested some 16,000 hectares of cactus.
Source: Cochineal
