Fossil Fungi-feeding Beetle Larvae in Deep Time

Many beetle larvae are common feeders on fungi and molds, and this mycophagous lifestyle is likely ancestral for several beetle lineages. The ecological roles of these beetles are often reflected in their vernacular names, such as handsome fungus beetles, hairy fungus beetles, and silken fungus beetles. Some species display specialized feeding behaviors, including burrowing into fungal fruiting bodies or fungus-infested wood.

Immature stages of handsome fungus beetles, minute bark beetles, and pleasing fungus beetles often possess distinctive setiferous (bristle-bearing) processes, likely linked to their ecological adaptations. These structures may aid in camouflage, defense, or even spore dispersal. In fact, the use of body processes for cloaking is not unique to beetles; it also occurs in other insects, such as some lacewing larvae. Larvae of handsome fungus beetles, for example, may cloak themselves with debris, fungal hyphae, or plant material. In a remarkable case of parental investment, females of Endomychus biguttatus wrap fungal hyphae around their eggs, offering them physical protection.

Despite the ecological importance and widespread occurrence of these larvae, their fossil record remains poorly explored. Reports of fossilized larvae have been limited and sporadic. Our study significantly expands this record by documenting new larval specimens preserved in amber from multiple deposits, spanning several geological periods and diverse geographic regions. These findings provide valuable insights into the deep evolutionary history and ecological continuity of fungus-associated beetle larvae.