It is known today that 'hiochi bacteria' which cause the phenomenon called hiochi live on Mevalonic acid (MVA, also known as hiochi acid) created by Aspergillus oryzae.
火落ちという現象を起こす「火落ち菌」はコウジカビが生成するメバロン酸（通称「火落ち酸」）を主食とすることが今日ではわかっている。