American researchers are breeding moths that can be steered by radio control. Next they may attempt to develop tiny cameras and sensors light enough to be fitted to the bugs.

The purpose? "Urban espionage," says Mandyam Srinivasan, a professor of visual neuroscience at the University of Queensland.

"They would be able to fly inside buildings, entering through windows and doors inconspicuously." Perching on a wall they could "take movies, record sounds" without raising suspicion.