The EcoBot II uses human sewage as bait to catch the insects. It then digests the flies, before their exoskeletons are turned into electricity, which enables the robot to function.

Bacteria in the sewage eats the flies' soft tissues, which releases enzymes that break down the hardened shell.

Sugar molecules released from the broken-down shell are then absorbed and used as energy by the bacteria.

"The robot then has the energy to carry out some example tasks which in this case include moving towards light, measuring temperature. It has a temperature sensor. It could be anything, but we have chosen temperature," Melhuish said.

"Then it transmits that temperature information over a radio link to a base station a couple of meters away and it does that all using the energy from insect or plant material."