Before the discovery of the microscope, and before "ecological observation" became popular, when our ancestors saw these insects emerge from soft earth and light up, they imagined that the firefly was a metamorphosis from rotting leaves or decaying bamboo. The saying, "On summer nights, rotting grass turns into fireflies," was a natural result of observing transformations as the weather changed from season to season.
放大鏡尚未發明，老祖先也不流行所謂「生態觀察」之前，古人見到腐土中飛出流螢，就想像螢是腐草及爛竹根幻化而來，固有「季夏之夜，腐草為螢」的說法，並以之為觀察四時節氣變化的自然景象。