Also known as pixie(小妖精)rings, fairy circles, and elf circles, fairy rings are naturally occurring rings or arcs(円弧)of mushrooms found in forested areas or grasslands. The rings are formed when a spore(胞子)grows underground and pushes out mycelia(菌糸体)- fungal threads - in all directions, eventually producing a ring of mushrooms or a dark circle of grass. In English folklore, fairy rings were said to be caused by elves, fairies, or pixies dancing in a circle.