Godzilla vs. Megaguirus is a 2000 film directed by Masaaki Tezuka and written by Hiroshi Kashiwabara and Wataru Mimura. Japan is threatened not only by Godzilla, but by a gigantic flying monster and its legions of hungry larva. As the monsters go at it, the Japanese military scrambles to destroy all them all.
An experimental satellite-based weapon that fires miniature black holes, called the Dimension Tide, opens a wormhole through which a giant prehistoric dragonfly enters the present and deposits a single egg before exiting through the wormhole. A boy finds the egg and takes it with him when he moves to Tokyo. The egg starts oozing a strange liquid, so the boy throws the egg in the sewer. The egg, actually a mass of hundreds of eggs, splits up and starts growing when exposed to water, hatching into giant dragonfly larva called Meganulon that come out of the sewer to feed. They flood a portion of the city and moult on the sides of buildings, becoming adult Meganula.