The well-known polyesters that have proved so useful for fabrics and other purposes are usually considered to be a man-made product. However, according to Science magazine, researchers have found what “appears to be the first report of a naturally occurring linear polyester.” Bees of the genus Colletes secrete a substance to line cells formed in the earth for housing their eggs. Once the substance is spread, a still unknown process (possibly enzymatic) polymerizes it, and the resulting polyester protects the bee larvae from water, fungi and soil microorganisms. The tough natural polyester is said to resist decay for more than a year.