Polish cochineal (Porphyrophora polonica), also known as Polish carmine scales, is a scale insect formerly used to produce a crimson dye of the same name, colloquially known as "Saint John's blood". The larvae of P. polonica are sessile parasites living on the roots of various herbs growing on the sandy soils of Central Europe and other parts of Eurasia. Its primary host plant is the perennial knawel (Scleranthus perennis), but it has also been known to feed on plants of 20 other genera, including mouse-ear hawkweed (Hieracium pilosella), bladder campion (Silene vulgaris), velvet bent (Agrostis canina), Caragana, smooth rupturewort (Herniaria glabra), strawberry (Fragaria), and cinquefoil (Potentilla).
Before the development of aniline, alizarin, and other synthetic dyes, the insect was of great economic importance, although its use was in decline after the introduction of Mexican cochineal to Europe in the 16th century. Polish cochineal was widely traded in Europe during the Middle Ages and the Renaissance. In the 15th and 16th centuries, along with grain, timber, and salt, it was one of Poland's and Lithuania's chief exports, mainly to southern Germany and northern Italy as well as to France, England, the Ottoman Empire, and Armenia. (Full article...)