The citizens of Tokyo thought that Mothra was evil because of her rampage through their city. Because of this, they made a mechanic (but still living and thinking) version of her to destroy the giant moth. This mech had the DNA of Mothra in her body so she wouldn't be ripped apart, and would be durable and strong. Her name was MechaMothra, and was sent out right when Mothra came back. Mothra was almost killed by the horrible mech, but her friend, Godzilla, came and made MechaMothra retreat.
MechaMothra has a rocket engine at the end of her, making her able to fly at mach 4.9! Her arms are grappling hooks that can reach up to 100 meters, can shoot electricity from her "eyes", her antennae can track down Mothra, and she can breathe in air, water, and outer space.
MechaMothra looks mainly just like Mothra, except she is robotic, her eyes are durable lights, her arms are grappling hooks, and she has a rocket engine. Her length is 80 meters (not including the flame from the engine), but her wings are smaller than the regular Mothra's.