In a lab at the University of Wyoming, some silkworms are spinning cocoons of silk, just as every silkworm has done for millions of years. But these insects are special. They have been genetically engineered to spin a hybrid material that’s partly their own silk, and partly that of a spider. With spider DNA at their disposal, they can weave fibres that are unusually strong and tough. It’s the latest step in a decades-long quest to produce artificial spider silk.

Spider silk is a remarkable material, wonderfully adapted for trapping, crushing, climbing and more. It is extraordinarily strong and tough, while still being elastic enough to stretch several times its original length. Indeed, the toughest biological material ever found is