Lac is the scarlet resinous secretion of a number of species of lac insects, of which the most commonly cultivated species is Kerria lacca.Cultivation begins when a farmer gets a stick (broodlac) that contains eggs ready to hatch and ties it to the tree to be infested.ac for dye has been somewhat replaced by the emergence of synthetic dyes, though it remains in use, and some juices, carbonated drinks, wine, jam, sauce, and candy are colored using it. Lac is used in folk medicine as a hepatoprotective and anti-obesity drug.