MOTHRA.

Mothra is believed to be a species of prehistoric insect. A Moth, of course.
Her first film was in 1961 and it was entitled, simply "MOTHRA" (no suprise)
Mothra was the third major addition to the Toho Studios' giant-monster stable after Godzilla and Rodan, and the first female beast in the series. The creature begins Ishiro Honda's entertaining film as a giant larva worshipped by island tribesmen and guarded by twin sisters (Emi and Yumi Ito) who stand only a few inches high. Eventually, the larva metamorphoses into a giant female moth and panic ensues as the creature attempts to regain her tiny protectors. The usual pandemonium and destruction is tempered here by a softer edge which would come to dominate the genre for much of the decade. (source: RottenTomatoes.com)

Mothra was always portrayed as a "good Kaiju" (monster in Japanese) Even in the first film, though she lays waste to two cities (Japan and the fictional country Rolithica) Mothra only did so to save the two tiny sisters who as mentioned were her gaurdians or, priestesses, who were kidnapped from the island (known as "Infant Island" in most films) by greedy buisness people. Once Mothra recovers the fairy girls she returns peacefuly to Infant Island.

Mothra reappears in the 1964 film "Mosura Tai Gojira" (Mothra vs. Godzilla) In this film, Mothra's egg is washed away from Infant Island in a typhoon, only to float ashore in Tokyo. Where, right on que, Godzilla awakens (after his 1962 bout with King Kong) Well, evidently, Godzilla wakes up hungry and decides he wants an EGG for breakfast. How convinient that Motra's egg is available (Saves Godzilla a trip to Denny's, I guess) At any rate, Godzilla begins to once again destroy cities in Japan, Mothra is called upon to save Japan (and possibly the world) from the marauding Godzilla. PLUS She has to try to save her EGG in the process! Fortunately, Mothra is able to defeat Godzilla in the end, as she is killed by the surly saurian, but 2 larva Mothras hatch from the egg and cacoon Godzilla in their silk webs. Godzilla stumbles off a cliff returning him to the ocean forever. (No, Not really, Godzilla and Mothra both appear in the next film "GHIDRA the 3 headed monster" in which Godzilla and Mothra actually become allies (along with Rodan) to defeat Ghidora.)
Mothra went on to do other films later, and in the 1990's had her very own trilogy of films.
Although she is sort of a "goofy" monster, Mothra was and still is popular amoung Kaiju fans.

NOTE: While stated earlier that Mothra was a prehistoric insect, it's un clear how she reached such gargantuan size. Some speculate that she was mutated and grew much larger than normal by atomic bomb tests, near by her Island, much in the same way Godzilla was created.



depictions of MOTHRA. below is from the 1960's. the one above is a later depiction from the 1990's.