A blowfly can detect the chemical signature of death from several kilometres away. Within minutes of an animal or human dying, the first female lands, finds a moist cavity, and lays a clutch of eggs. She is not acting on instinct alone in any vague sense, she is responding to a precise blend of volatile compounds, primarily putrescine and cadaverine, that the body begins releasing as cellular membranes break down. What follows her arrival is not chaos but a tightly ordered biological sequence that forensic scientists have spent decades learning to read.
