Query: What dye was known as the Blood of Saint John?
Context: For the wealthy, the dye used was Kermes, made from a tiny scale insect which fed on the branches and leaves of the oak tree. For those with even more money there was Polish Cochineal; also known as Kermes vermilio or "Blood of Saint John", which was made from a related insect, the Margodes polonicus. It made a more vivid red than ordinary Kermes.