Holy shit... it's technically a shit-bot.
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.
Not so strange perhaps, considering this year's big toy, Robosapien, is famous for farting.