Grave of the Fireflies
Two Japanese species of "Luciola", collectively known as "hotaru" (蛍), are highly significant in Japanese culture and folklore. They are symbols of the "hitodama" (人魂 or 人玉), the souls of the newly dead. See also the explanations at the article on the movie "Hotaru no Haka" ("Grave of the Fireflies") for a discussion of the cultural significance of the "hotaru".