Some stinkbugs’ legs carry a mobile fungal garden

A fascinating discovery has emerged from Japan, where researchers have revealed that the hind legs of certain stinkbugs serve a function quite different from what was previously believed. For years, scientists thought that female stinkbugs from the Dinidoridae family possessed tympanal organs—structures similar to human eardrums—allowing them to detect male courtship songs. However, a team led by evolutionary biologist Takema Fukatsu at the National Institute of Advanced Industrial Science and Technology conducted a detailed examination of the Megymenum gracilicorne, a stinkbug species native to Japan. What they found was unexpected. Instead of tympanal organs, the structures on these insects' hind legs are actually mobile fungal nurseries, a phenomenon never documented before. The Dinidoridae family, which is exclusive to Asia, has not received as much scientific attention as its larger relatives, such as the Pentatomidae family. Previous research on the hind legs of female Dinidoridae had been scant, relying mainly on morphological and taxonomic methods. Researchers had classified the enlarged structures as tympanal organs based on their appearance. Fukatsu's team aimed to investigate the implications of the unusual placement of these organs on sound perception in female stinkbugs. However, they discovered that the enlarged parts on the hind legs had no connection to hearing at all. "We found no tympanal membrane and no sensory neurons," Fukatsu stated. Instead, the team identified thousands of tiny pores filled with harmless filamentous fungi, which are linked to secretory cells that likely provide nutrients for the fungi's growth. This breakthrough opens new avenues for understanding the ecological roles that these fungi may play in the lives of these unique insects.