It's difficult to make an insect-like flying robot -- realistic four-winged bots are typically too heavy, while lighter two-winged models tend to fly erratically. USC researchers have edged one step closer to the dream machine, however. They've created Bee+, a four-winged bot (pictured at right) that flies with more of the agility and poise of real insects while weighing just over 0.003oz. The trick was to drop earlier bimorph actuators, cantilevers made of two layers of piezoelectric material with a passive layer in between, with unimorphs that only have one piezoelectric layer. The four actuators combined weigh half as much as bimorphs would at just under 0.002oz, reducing the wing loading and significantly improving control.