Coceus cacti, an insect used as a dye, is found on several species of cactus, but particularly on one, which is thence called Cactus cochineellifer. This plant is cultivated largely for the purpose in Mexico and in Honduras; and also on a small scale in Tenerife, Java, &c. The insects are scraped off the plants into bags; and killed either in hot air ovens or by immersion in boiling water; then dried in the sun, and put up for exportation in serons (skin bags).
The cochineal yields a brilliant crimson dye, which is highly esteemed and extensively used in this country. The methods of preparing the different tints are described under Dyeing. The English market is almost entirely supplied from Honduras, Mexico, and Tenerife. Honduras produces the best, Mexico that of least value. The insect, as imported, resembles in bulk and shape a full-sized grain of barley. There are two varieties, distinguished in commerce as "silvers" and "blacks." Of these, the black is the more valuable—the finer kind usually exceeding the silver in price by 1s., and the inferior by a few pence per lb. respectively. The silver kind, said to be the female insect, constitutes fully two-thirds of the imports into Britain. Its back presents a rugose or ribbed appearance, and is covered over with a fine dust of a bright silvery lustre. The most esteemed are large, plump, and dry. They are less prized when dull or dark-coloured; and still less valuable when they have the bad qualities of being small, of a pink tint, clammy, or adulterated by the admixture of paste.
The black kind, said to be the male insect, is either dark brown or gray, and about the same size as the silver. The finest exhibit a shelly appearance, have a dark shining lustre, and are large, but at the same time light.
On its arrival in this country, cochineal is usually taken out of the serons and "garbled" (sifted) in order to separate the dust, &c. It is afterwards repacked in linen or cotton bags, instead of in the serons.
Granilla, a very inferior kind of cochineal, consists of small insects collected from wild uncultivated plants. According to Humboldt (Essai Polit. on N. Spain), the plants on which the two kinds of cochineal live are essentially different, and the species of insect is probably also different.
About a century ago, cochineal and silver bullion were often classed together as articles of equal value. Extended cultivation, however, in Honduras and elsewhere, more especially in Mexico, has wrought a wonderful change in the value of cochineal. This once precious article of commerce has of late years fluctuated in value between 3s. and 6s. per lb., its average price being from about 4s. to 5s. In 1814 the price rose to 36s. and 39s.; but afterwards it gradually declined, till in 1852, when the imports greatly exceeded the average quantity (having amounted to no less than 22,042 cwts.), the price of silver cochineal fell below 3s. a lb. The duty on cochineal was abolished in 1845.