The toxic ectomycorhizal fungi Amanita muscaria (Agaricales: Amanitaceae) was first recorded in New Zealand in 1937, and it is now widespread throughout the country. We collected decaying fruiting bodies of the mushroom in 2005 and 2006 and placed them in enclosed emergence traps to determine use by fungivorous insects. This study clarified that the endemic species Mycetophila fagi, M. filicornis (Diptera: Mycetophilidae) and Zedura curtisi (Diptera: Trichoceridae), as well as exotic Drosophila busckii (Diptera: Drosophilidae), utilised the exotic A. muscaria in various vegetation types in the North and South Islands of New Zealand. A significant difference was observed in the number of fungivorous insects found on the mushrooms between North and South Islands; the endemic M. fagi was dominant in South Island, while Psychodidae sp. dominated North Island. A significant difference was observed in the number of fungivorous insects between the exotic and endemic vegetation inhabited by A. muscaria. Furthermore, the biodiversity of fungivorous insects on A. muscaria within endemic Nothofagus vegetation was more than three times greater than that within the exotic Betula, Pinus, Pseudotsuga and Tsuga vegetation. These observations suggest that the greater diversity of fungivorous insects on A. muscaria in natural Nothofagus forests may reflect the higher diversity found in natural forests compared with plantation forests.