Paleontologists have long wondered how aquatic creatures such as water beetles end up fossilized in amber, a material derived from hardened tree sap. One exotic suggestion was that the creatures had lived in water-filled clefts in trees, says Alexander R. Schmidt, a biologist at the Museum of Natural History in Berlin.
However, field tests in a swamp by Schmidt and paleobotanist David L. Dilcher of the University of Florida in Gainesville provide a simpler explanation. Within hours of resin dropping into water from a damaged pine tree, a variety of organisms—including the water beetle shown here—became stuck. The resin solidified when the swamp dried out, the researchers report in an upcoming Proceedings of the National Academy of Sciences.