Police release a swarm of robot-moths to sniff out a distant drug stash. Rescue robot-bees dodge through earthquake rubble to find survivors. These may sound like science-fiction scenarios, but they are the visions of Japanese scientists who hope to understand and then rebuild the brains of insects and programme them for specific tasks. [...] In an example of ’rewriting’ insect brain circuits, Kanzaki’s team has succeeded in genetically modifying a male silkmoth so that it reacts to light instead of odour, or to the odour of a different kind of moth.