We conducted field and laboratory observations of the life histories and fungal hosts of the darkling beetle, Platydema nigroaeneum Motschulsky. P. nigroaeneum, a fungivorous tenebrionid beetle, was a widespread inhabitant of fungi on deciduous trees (Quercus, Salix, Alnus and Carpinus etc.) in Korea. Development from egg to adulthood took $4sim11$ months in nature and about 66 days in the laboratory at $25.5{sim}26.1^{circ}C$ and $63.5sim64.5%$ relative humidity. Both larvae and adults overwintered in their host fungi or beneath the bark of the host tree near the host fungi. Sporophores of Coriolus $Qu{acute{e}}let$, Bjerkandera Karst., Daedaleopsis Schroet. and Merulius were common feeding and breeding sites in Korea.