A sixteenth-century altar in one of Germany's most historically important cathedrals has been saved from woodworm not by the application of chemicals, but by a swarm of wasps. The Cranach altar in the Erfurt Cathedral was being destroyed by the wood-eating insects, but officials delayed taking action because they feared that chemical treatments might damage its 11 painted panels. Instead they adopted a pioneering technique which may now be emulated in historic buildings across Europe: releasing 3,000 parasitic wasps, which feed on woodworm larvae. The towering wooden altar, riddled with holes, and the large painting above it which also showed...