Cochineal (Dactylopius coccus)
COCCIDAE, Scale Insect Family
Cochineal is a traditional red dye of pre-Hispanic Mexico. This precious dyestuff was obtained not from a plant, but from an insect that lives its life sucking on a plant. The host plants are the flattened stems (pads or cladodes) of certain prickly pear cacti (platyopuntias, Opuntia), especially the species called nopales. The animal is a scale insect that manufactures a deep maroon pigment and stores this pigment in body fluids and tissues. Early Mixtec Indians required dyestuffs because the color of daily attire was carefully codified to signal social status. They required fast colors, i.e., those that would not fade, and Mixtecs heavily used indigo, derived from native legumes, for blues and cochineal for various shades of red.
Scale insects are lazy creatures. A cactus pad is colonized by a female, who produces some new females that settle around the mother and set up housekeeping. A female inserts the proboscis, a tube, into the pad for obtaining nourishment, and secretes a white, web-like, wax-based material over the area for camouflage and to prevent desiccation. Males are small and live for only a week, just long enough to mate with as many females as possible. Females, which are about one-quarter inch long, are purplish-black inside and silvery outside.
The pigmentation is a bitter, astringent chemical called carminic acid (10% total dry weight), which is extremely effective in repelling potential predators, such as ants; ants find this anthraquinone to be unpalatable. Interestingly, the caterpillar of a pyralid moth (Laetilia coccidivora) eats cochineal scale and stores carminic acid from the scale in its gut, to be used later against its natural enemy ant, Monomorium destructor.
Mixtexs and their successors in southern Mexico farmed cochineal with great skill. They reproduced the plant by planting pads already inoculated with scale; they fertilized the cactus with wood ashes and garbage; they removed competing plants from around the cactus; they kept domesticated animals away by building walls and hedges; they lit fires on cold nights to prevent the insects from freezing; and they even built temporary shelters to shield the insects from heavy rains. Through this process, they also selected for a domesticated form of the scale insect, a form that produce the best dye but was also more susceptible to stress from cold and rain than the wild form.
When Spaniards arrived in Mexico, they were fascinated by the intense scarlet color of cochineal dye, which was brighter and better than anything in the Old World. Upon first observing the dyeing process, Spaniards thought that the pigment was ground from a gray seed, not an insect, and called these grana (seeds). Textiles dyed with cochineal were shipped to Europe and became the rage; in fact, next to gold cochineal was the most desired import commodity from Middle America, and Spain established a monopoly in its trade and placed an embargo on the export of live insects from Mexico. Spain produce huge trade profits from cochineal in agreements with their friends, but enemy England was excluded, and, consequently, England's textile industry also suffered proportionately.
The Spaniards permitted cochineal production to remain in the hands of the Indian population, encouraged by the Dominican monks at the missions. Unexpectedly, small land owners became very wealthy in producing cochineal, and this upset the large land owners (haciendas), who feared competition and social change from a potentially wealthy lower class. Hacienda owners therefore tried to limit propagation of fresh cactus pads, but their efforts were undermined because the export demands were too great and encouraged by viceroys and governors.
After 250 years, the Spanish monopoly on cochineal production was broken when in 1777 a French naturalist smuggled Mexican cactus pads with scale insects to Haiti. Later, pads were transported to South America, India, the Canary Islands, and Portugal. Nonetheless, cochineal textiles were much in demand. For example, in the Southwest United States in the 1800s, the Navajo, who had no red in their original weavings, traded for cochineal-dyed flannel blankets (bayetas) of Spanish soldiers; the bayetas were unraveled, and threads were then reused in Navajo textiles. When used with the mordant nitromuriate of tin, cochineal produced a vivid scarlet color for dyeing silk, thus replacing the traditional European red scale dye call Kermes red (the scale insect Kermococcus vermilis on Mediterranean oak, Quercus).
Cochineal production became an important export from the Canary Islands, where three tons of the powder was produced in 1875. However, there was a setback in the 1870s when synthetic red aniline dyes (from coal tar) were starting to be used instead of cochineal. Aniline dyes essentially replaced cochineal by the early 1900s. Fortunately, cochineal dyeing continued in its homeland, and this pigment began to appear in commercial products of the United States primarily as a food dye, as in pork sausage, pies, dried fish and shrimp, candies, pills, jams, lipstick and rouge, and the brightly colored maraschino cherries. Here too cochineal was replaced by red dye numbers 2 and 40, which are believed now to be carcinogenic, and cochineal is being reconsidered as a safe food dye.
Cochineal dyeing in southern Mexico is now folk art and practiced by the natives. The female insects are hand-picked and dried in the sun, interrupted by periods in shade. The finest form is called silver cochineal (plateada). Also collected are the leaves of a special tree of Oaxaca, the tejuté (Miconia argentea, Family Melastomataceae), which grows in lowland forests near the Isthmus of Tehuantepec. Well water is heated in a large aluminum pot over a wood fire while skeins of woolen thread are soaked in a tub of clear, cool water. When the water starts to steam, the dyer throws in several handfuls of dried, crumbled tejuté leaves (the mordant and color intensifier; oxalic acid). Cochineal powder (1/2 pound to 15 gallons of water) is added to the boiling water, and juice from fresh limes (80 per 15 gallons) are also added and stirred in. Then the wet skeins of wool are placed into the pot and boiled for more than an hour. During this time an acrid odor comes from the hot acid in the pot. After soaking in the dye, the skeins are hung to cool on nearby branches and permitted to dry overnight. The next day the skeins are washed in a sudsy water and rinsed thoroughly in a flowing stream, to bring back the intense red color. Then the skeins are dried for two to three days. The resultant color is dependent on the duration of soaking, the amount of the pigment used, and the chemicals added to the boiling water for the mordant process.