Amanita muscaria, commonly known as the fly agaric or fly amanita, is a basidiomycete of the genus Amanita. It is also a muscimol mushroom. Native throughout the temperate and boreal regions of the Northern Hemisphere, Amanita muscaria has been unintentionally introduced to many countries in the Southern Hemisphere, generally as a symbiont with pine and birch plantations, and is now a true cosmopolitan species. It associates with various deciduous and coniferous trees.
Arguably the most iconic toadstool species, the fly agaric is a large white-gilled, white-spotted, usually red mushroom, and is one of the most recognizable and widely encountered in popular culture.
Despite its easily distinguishable features, Amanita muscaria is a fungus with several known variations, or subspecies. These subspecies are slightly different, some have yellow or white caps, but they are all usually called fly agarics, and they are most of the time recognizable by their notable white spots. Recent DNA fungi research, however, has shown that some of these variations are not muscarias at all, such as peach-colored fly agaric for example, but the common name 'fly agaric' clings on.
Although classified as poisonous, reports of human deaths resulting from A. muscaria ingestion are extremely rare. After parboiling twice with water draining—which weakens its toxicity and breaks down the mushroom's psychoactive substances—it is eaten in parts of Europe, Asia, and North America. All Amanita muscaria varieties, but in particular A. muscaria var. muscaria, are noted for their hallucinogenic properties, with the main psychoactive constituents being the neurotoxins ibotenic acid and muscimol. A local variety of the mushroom was used as an intoxicant and entheogen by the indigenous peoples of Siberia and by the Sámi, and has a religious significance in these cultures. There has been much speculation on possible traditional use of this mushroom as an intoxicant in other places such as the Middle East, Eurasia, North America, and Scandinavia.
Description & appearance
A large, conspicuous mushroom, Amanita muscaria is generally common and numerous where it grows, and is often found in groups with basidiocarps in all stages of development. Fly agaric fruiting bodies emerge from the soil looking like white eggs. After emerging from the ground, the cap is covered with numerous small white to yellow pyramid-shaped warts. These are remnants of the universal veil, a membrane that encloses the entire mushroom when it is still very young. Dissecting the mushroom at this stage reveals a characteristic yellowish layer of skin under the veil, which helps identification. As the fungus grows, the red colour appears through the broken veil and the warts become less prominent; they do not change in size, but are reduced relative to the expanding skin area. The cap changes from globose to hemispherical, and finally to plate-like and flat in mature specimens. Fully grown, the bright red cap is usually around 8–20 cm (3–8 in) in diameter, although larger specimens have been found. The red colour may fade after rain and in older mushrooms. The free gills are white, as is the spore print. The oval spores measure 9–13 by 6.5–9 μm; they do not turn blue with the application of iodine. The stipe is white, 5–20 cm (2.0–7.9 in) high by 1–2 cm (0.5–1 in) wide, and has the slightly brittle, fibrous texture typical of many large mushrooms. At the base is a bulb that bears universal veil remnants in the form of two to four distinct rings or ruffs. Between the basal universal veil remnants and gills are remnants of the partial veil (which covers the gills during development) in the form of a white ring. It can be quite wide and flaccid with age. There is generally no associated smell other than a mild earthiness.
Although very distinctive in appearance, the fly agaric has been mistaken for other yellow to red mushroom species in the Americas, such as Armillaria cf. mellea and the edible Amanita basii—a Mexican species similar to A. caesarea of Europe. Poison control centres in the U.S. and Canada have become aware that amarill (Spanish for 'yellow') is a common name for the A. caesarea-like species in Mexico. Amanita caesarea is distinguished by its entirely orange to red cap, which lacks the numerous white warty spots of the fly agaric. Furthermore, the stem, gills and ring of A. caesarea are bright yellow, not white. The volva is a distinct white bag, not broken into scales. In Australia, the introduced fly agaric may be confused with the native vermilion grisette (Amanita xanthocephala), which grows in association with eucalypts. The latter species generally lacks the white warts of A. muscaria and bears no ring.
Distribution & habitat
Amanita muscaria is a cosmopolitan mushroom, native to conifer and deciduous woodlands throughout the temperate and boreal regions of the Northern Hemisphere, including higher elevations of warmer latitudes in regions such as Hindu Kush, the Mediterranean and also Central America. A recent molecular study proposes that it had an ancestral origin in the Siberian–Beringian region in the Tertiary period, before radiating outwards across Asia, Europe and North America. The season for fruiting varies in different climates: fruiting occurs in summer and autumn across most of North America, but later in autumn and early winter on the Pacific coast. This species is often found in similar locations to Boletus edulis, and may appear in fairy rings. Conveyed with pine seedlings, it has been widely transported into the southern hemisphere, including Australia, New Zealand, South Africa and South America, where it can be found in the southern Brazilian states of Paraná and Rio Grande do Sul.
Ectomycorrhizal, Amanita muscaria forms symbiotic relationships with many trees, including pine, spruce, fir, birch, and cedar. Commonly seen under introduced trees, A. muscaria is the fungal equivalent of a weed in New Zealand, Tasmania and Victoria, forming new associations with southern beech (Nothofagus).The species is also invading a rainforest in Australia, where it may be displacing the native species. It appears to be spreading northwards, with recent reports placing it near Port Macquarie on the New South Wales north coast. It was recorded under silver birch (Betula pendula) in Manjimup, Western Australia in 2010. Although it has apparently not spread to eucalypts in Australia, it has been recorded associating with them in Portugal.