Megaguirus is the queen of an insect race called Meganulon which thrives by parasitically siphoning energy from larger creatures. As such, she is one of few decidedly female creatures of the genre.
Megaguirus was created when a weapon that would send Godzilla into another dimension allowed a giant insect to arrive on Earth and lay an egg which would later be discovered by a young boy and then hatch into a Meganulon. Megaguirus has numerous abilities. At top flight speed she vanishes into a blur, enabling her to surprise an opponent from an unexpected quarter. This high-speed flight also produces high frequency sonic waves capable of shorting out nearby electrical equipment. Her sharp wings can even cut steel and concrete. Her large abdomen ends in a vicious stinger used to pierce into an opponent's hide and drain energy from it. During this process, the opponent is incapable of launching any additional energy-based attacks upon her. She is an Insect Monster, like Mothra, Mothra Leo, Battra, Megalon, Kumonga and Kamacuras. She is the main antagonist of the microgame with the same name, Megaguirus.