In recent years, it has been found that symbiotic microorganisms play important roles in survival and activity of agricultural and hygienic pests, and that intestinal bacteria substantially impact on health and disease of humans. Therefore, various biological functions of symbiotic microorganisms have attracted considerable attention.

In cooperation with the University of Montana, researchers of AIST and the University of Ryukyus examined 24 Japanese cicada species and found that 15 of them are associated with endosymbiotic fungi that are closely related to cicada-parasitizing Cordyceps fungi. In this research, it was demonstrated that evolution from parasitic relationships to symbiotic relationships has occurred repeatedly, which uncovered an unexpectedly close relationship between fungal parasitism and symbiosis. Cordyceps and related fungi are often used in Chinese medicine, and they are also known as producers of bioactive substances including immunosuppressants. Diverse symbiotic fungi associated with tropical/subtropical cicadas also have potential as new biological genetic resources.