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Amanita muscaria, commonly known as the fly agaric or fly amanita, is a basidiomycete fungus of the genus Amanita. It is a large white-gilled, white-spotted mushroom typically featuring a bright red cap covered with distinctive white warts. It is one of the most recognisable fungi in the world.
A.muscaria exhibits complex genetic diversity that suggests it is a species complex rather than a single species. It is a widely distributed mushroom native to temperate and boreal forests of the Northern Hemisphere, now also naturalised in the Southern Hemisphere, forming symbiotic relationships with various trees and spreading invasively in some regions.
Its name derives from its traditional use as an insecticide. It can cause poisoning, especially in children and those seeking its effects, due to psychoactive compounds like muscimol and the ibotenic acid; however, fatal poisonings are extremely rare. Boiling it reduces toxicity by removing water-soluble ibotenic acid into the discarded water. Drying converts ibotenic acid into muscimol, lowering toxicity but retaining psychoactive effects. Some cultures use it as food after preparation. Indigenous peoples of Siberia used A.muscaria as an inebriant and entheogen. It has been controversially linked to Santa Claus, Viking , Vedic soma, and early Christianity, though evidence is sparse and disputed. Its rise in the 2020s as a legal hallucinogen alternative has led to Food and Drug Administration scrutiny.
A.muscaria has appeared in art and literature since the Renaissance, becoming iconic in , children’s books, and media like the Super Mario games and Disney’s Fantasia. It has also influenced literary depictions of altered perception—most notably in Alice’s Adventures in Wonderland—and has been referenced in novels by writers including Oliver Goldsmith, Thomas Pynchon, and Alan Garner.
The English mycologist John Ramsbottom reported that Amanita muscaria was used for getting rid of bugs in England and Sweden, and bug agaric was an old alternative name for the species. French mycologist Pierre Bulliard reported having tried without success to replicate its fly-killing properties in his work Histoire des plantes vénéneuses et suspectes de la France (1784), and proposed a new binomial name Agaricus pseudo-aurantiacus because of this. One compound isolated from the fungus is 1,3-diolein (1,3-di(cis-9-octadecenoyl)glycerol), which attracts insects. It has been hypothesised that the flies intentionally seek out the fly agaric for its intoxicating properties.
An alternative derivation proposes that the term fly- refers not to insects as such but rather the delirium resulting from consumption of the fungus. This is based on the medieval belief that flies could enter a person's head and cause mental illness. Several regional names appear to be linked with this connotation, meaning the "mad" or "fool's" version of the highly regarded edible mushroom Amanita caesarea. Hence there is oriol foll "mad oriol" in Catalan language, mujolo folo from Toulouse, concourlo fouolo from the Aveyron department in Southern France, ovolo matto from Trentino in Italy. A local dialect name in Fribourg in Switzerland is tsapi de diablhou, which translates as "Devil's hat".
The free gills are white, as is the spore print. The oval spores measure 9–13 by 6.5–9 micrometre; they do not turn blue with the application of iodine. The stipe is white, high
by 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 Amanita 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. A. caesarea is distinguished by its entirely orange to red cap, which lacks the numerous white warty spots of the fly agaric (though these sometimes wash away during heavy rain). 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. Additionally, immature button forms resemble .
However, a 2006 molecular phylogenetic study of different regional populations of A. muscaria by mycologist József Geml and colleagues found three distinct within this species representing, roughly, Eurasian, Eurasian "subalpine", and North American populations. Specimens belonging to all three clades have been found in Alaska; this has led to the hypothesis that this was the centre of diversification for this species. The study also looked at four named varieties of the species: var. alba, var. flavivolvata, var. formosa (including var. guessowii), and var. regalis from both areas. All four varieties were found within both the Eurasian and North American clades, evidence that these morphological forms are polymorphisms rather than distinct subspecies or varieties. Further molecular study by Geml and colleagues published in 2008 show that these three genetic groups, plus a fourth associated with oak–hickory–pine forest in the southeastern United States and two more on Santa Cruz Island in California, are delineated from each other enough genetically to be considered separate species. Thus A. muscaria as it stands currently is, evidently, a species complex. The complex also includes at least three other closely related taxa that are currently regarded as species: A. breckonii is a buff-capped mushroom associated with conifers from the Pacific Northwest, and the brown-capped Amanita gioiosa and A. heterochroma from the Mediterranean Basin and from Sardinia respectively. Both of these last two are found with Eucalyptus and Cistus trees, and it is unclear whether they are native or introduced from Australia.
Amanitaceae.org lists four varieties , but says that they will be segregated into their own taxa "in the near future". They are:
| ! Amanita muscaria var. muscaria | Euro-Asian fly agaric | Bright red fly agaric from northern Europe and Asia. Cap might be orange or yellow due to slow development of the purple pigment. Wide cap with white or yellow warts which are removed by rain. Known to be toxic but used by shamans in northern cultures. Associated predominantly with Birch and diverse conifers in forest. | |
| ! Amanita muscaria subsp. flavivolvata | American fly agaric | Red, with yellow to yellowish-white warts. It is found from southern Alaska down through the Rocky Mountains, through Central America, all the way to Andean Colombia. Rodham Tulloss uses this name to describe all "typical" A. muscaria from indigenous New World populations. | |
| ! Amanita muscaria var. guessowii | American fly agaric (yellow variant) | Amanita muscaria var. formosa | Has a yellow to orange cap, with the centre more orange or perhaps even reddish orange. It is found most commonly in northeastern North America, from Newfoundland and Quebec south all the way to the state of Tennessee. Some authorities (cf. Jenkins) treat these populations as A. muscaria var. formosa, while others (cf. Tulloss) recognise them as a distinct variety. |
| ! Amanita muscaria var. inzengae | Inzenga's fly agaric | It has a pale yellow to orange-yellow cap with yellowish warts and stem which may be tan. |
, A. muscaria forms symbiotic relationships with many trees, including pine, oak, spruce, fir, birch, and Cedrus. 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).
A. muscaria contains several biologically active agents, at least one of which, muscimol, is known to be psychoactive. Ibotenic acid, a neurotoxin, serves as a prodrug to muscimol, with a small amount likely converting to muscimol after ingestion. An active dose in adults is approximately 6 mg muscimol or 30 to 60 mg ibotenic acid; this is typically about the amount found in one cap of A. muscaria. The amount and ratio of chemical compounds per mushroom varies widely from region to region and season to season, which can further confuse the issue. Spring and summer mushrooms have been reported to contain up to 10 times more ibotenic acid and muscimol than autumn fruitings.
Deaths from A. muscaria have been reported in historical journal articles and newspaper reports, but with modern medical treatment, fatal poisoning from ingesting this mushroom is extremely rare. Many books list A. muscaria as deadly,
but according to David Arora, this is an error that implies the mushroom is far more toxic than it is. Furthermore, the North American Mycological Association has stated that there were "no reliably documented cases of death from toxins in these mushrooms in the past 100 years".The active constituents of A. muscaria are water-soluble; boiling and then discarding the cooking water at least partly detoxifies it. Drying may increase potency, as the process facilitates the conversion of ibotenic acid to the more potent muscimol. According to some sources, once detoxified, the mushroom becomes edible. Patrick Harding describes the Sami custom of processing the fly agaric through reindeer.
The major toxins involved in A. muscaria poisoning are muscimol (3-hydroxy-5-aminomethyl-1-isoxazole, an unsaturated cyclic hydroxamic acid) and the related amino acid ibotenic acid. Muscimol is the product of the decarboxylation (usually by drying) of ibotenic acid. Muscimol and ibotenic acid were discovered in the mid-20th century. Researchers in England, Japan In: and Switzerland showed that the effects produced were due mainly to ibotenic acid and muscimol, not muscarine. These toxins are not distributed uniformly in the mushroom. Most are detected in the cap of the fruit, a moderate amount in the base, with the smallest amount in the stalk.Lampe, K.F., 1978. "Pharmacology and therapy of mushroom intoxications". In: Rumack, B.H., Salzman, E. (Eds.), Mushroom Poisoning: Diagnosis and Treatment. CRC Press, Boca Raton, FL, pp. 125–169 Quite rapidly, between 20 and 90 minutes after ingestion, a substantial fraction of ibotenic acid is excreted unmetabolised in the urine of the consumer. Almost no muscimol is excreted when pure ibotenic acid is eaten, but muscimol is detectable in the urine after eating A. muscaria, which contains both ibotenic acid and muscimol.
Ibotenic acid and muscimol are structurally related to each other and to two major of the central nervous system: glutamic acid and GABA respectively. Ibotenic acid and muscimol act like these neurotransmitters, muscimol being a potent GABAA agonist, while ibotenic acid is an agonist of NMDA receptor and certain metabotropic glutamate receptors which are involved in the control of neuronal activity. It is these interactions which are thought to cause the psychoactive effects found in intoxication.
Muscazone is another compound that has more recently been isolated from European specimens of the fly agaric. It is a product of the breakdown of ibotenic acid by ultraviolet radiation. Muscazone is of minor pharmacological activity compared with the other agents. Amanita muscaria and related species are known as effective bioaccumulation of vanadium; some species concentrate vanadium to levels of up to 400 times those typically found in plants. Vanadium is present in fruit-bodies as an organometallic compound called amavadine. The biological importance of the accumulation process is unknown.
In cases of serious poisoning the mushroom causes delirium, somewhat similar in effect to anticholinergic poisoning (such as that caused by Datura stramonium), characterised by bouts of marked agitation with confusion, hallucinations, and irritability followed by periods of central nervous system depression. Seizures and coma may also occur in severe poisonings. Symptoms typically appear after around 30 to 90 minutes and peak within three hours, but certain effects can last for several days. In the majority of cases recovery is complete within 12 to 24 hours. The effect is highly variable between individuals, with similar doses potentially causing quite different reactions.
Some people suffering intoxication have exhibited headaches up to ten hours afterwards. Retrograde amnesia and somnolence can result following recovery.
There is no antidote, and supportive care is the mainstay of further treatment for intoxication. Though sometimes referred to as a deliriant and while muscarine was first isolated from A. muscaria and as such is its namesake, muscimol does not have action, either as an agonist or antagonist, at the muscarinic acetylcholine receptor site, and therefore atropine or physostigmine as an antidote is not recommended.
If a patient is Delirium or agitated, this can usually be treated by reassurance and, if necessary, physical restraints. A benzodiazepine such as diazepam or lorazepam can be used to control combativeness, agitation, muscular overactivity, and seizures. Only small doses should be used, as they may worsen the respiratory depressant effects of muscimol. Recurrent vomiting is rare, but if present may lead to fluid and electrolyte imbalances; intravenous rehydration or electrolyte replacement may be required. Serious cases may develop loss of consciousness or coma, and may need intubation and artificial ventilation. Hemodialysis can remove the toxins, although this intervention is generally considered unnecessary. With modern medical treatment the prognosis is typically good following supportive treatment.
Marija Gimbutas reported to R. Gordon Wasson that in remote areas of Lithuania, A. muscaria has been consumed at , in which mushrooms were mixed with vodka. She also reported that the Lithuanians used to export A. muscaria to the Sami people in the Far North for use in shamanic rituals. The Lithuanian festivities are the only report that Wasson received of ingestion of fly agaric for religious use in Eastern Europe.
The Koryaks of eastern Siberia have a story about the fly agaric ( wapaq) which enabled Big Raven to carry a whale to its home. In the story, the deity Vahiyinin ("Existence") spat onto earth, and his spittle became the wapaq, and his saliva becomes the warts. After experiencing the power of the wapaq, Raven was so exhilarated that he told it to grow forever on earth so his children, the people, could learn from it. Among the Koryaks, one report said that the poor would consume the urine of the wealthy, who could afford to buy the mushrooms. It was reported that the local reindeer would often follow an individual intoxicated by the muscimol mushroom, and if said individual were to urinate in snow the reindeer would become similarly intoxicated and the Koryaks people's would use the drunken state of the reindeer to more easily rope and hunt them.
While Amanita mushrooms are unscheduled in the United States, they are listed as a poison by the FDA.
A recent outbreak of poisonings and at least one death associated with products containing Amanita muscaria extracts has sparked debates regarding the Drug prohibition of Amanita mushrooms and their psychoactive constituents, prompting an FDA ban of their use in food products in December 2024. These products often use misleading advertising, such as erroneous comparisons to Psilocybin mushrooms or simply not disclosing the inclusion of Amanita mushrooms on the packaging.
Mycophilosopher Martijn Benders has proposed a novel evolutionary theory involving Amanita muscaria. In his book Amanita Muscaria – the Book of the Empress, Benders argues that a precursor of ibotenic acid, a compound found in the mushroom, was present in ancient seaweed and played a significant role in the evolution of life. According to this hypothesis, the compound influenced the twitching movements of early aquatic organisms, leading to the development of behaviors such as jumping onto land—a crucial step in the evolution of terrestrial species.
The flying reindeer of Santa Claus, who is called Joulupukki in Finland, could symbolise the use of A. muscaria by Sámi shamans. However, Sámi scholars and the Sámi peoples themselves refute any connection between Santa Claus and Sámi history or culture.
"The story of Santa emerging from a Sámi shamanic tradition has a critical number of flaws," asserts Tim Frandy, assistant professor of Nordic Studies at the University of British Columbia and a member of the Sámi descendent community in North America. "The theory has been widely criticized by Sámi people as a stereotypical and problematic romanticized misreading of actual Sámi culture."
Use of this mushroom as a food source also seems to have existed in North America. A classic description of this use of A. muscaria by an African-American mushroom seller in Washington, D.C., in the late 19th century is described by American botanist Frederick Vernon Coville. In this case, the mushroom, after parboiling, and soaking in vinegar, is made into a mushroom sauce for steak.Coville, F. V. 1898. Observations on Recent Cases of Mushroom Poisoning in the District of Columbia. United States Department of Agriculture, Division of Botany. U.S. Government Printing office, Washington, D.C. It is also consumed as a food in parts of Japan. The most well-known current use as an edible mushroom is in Nagano Prefecture, Japan. There, it is primarily salted and pickled.
A 2008 paper by food historian William Rubel and mycologist David Arora gives a history of consumption of A. muscaria as a food and describes detoxification methods. They advocate that Amanita muscaria be described in field guides as an edible mushroom, though accompanied by a description on how to detoxify it. The authors state that the widespread descriptions in field guides of this mushroom as poisonous is a reflection of cultural bias, as several other popular edible species, notably morels, are also toxic unless properly cooked.
An account of the journeys of Philip von Strahlenberg to Siberia and his descriptions of the use of the mukhomor there was published in English in 1736. The drinking of urine of those who had consumed the mushroom was commented on by Anglo-Irish writer Oliver Goldsmith in his widely read 1762 novel, Citizen of the World. The mushroom had been identified as the fly agaric by this time. Other authors recorded the distortions of the size of perceived objects while intoxicated by the fungus, including naturalist Mordecai Cubitt Cooke in his books The Seven Sisters of Sleep and A Plain and Easy Account of British Fungi. This observation is thought to have formed the basis of the effects of eating the mushroom in the 1865 popular story Alice's Adventures in Wonderland. A hallucinogenic "scarlet toadstool" from Lappland is featured as a plot element in Charles Kingsley's 1866 novel Hereward the Wake based on the medieval figure of the same name. Thomas Pynchon's 1973 novel Gravity's Rainbow describes the fungus as a "relative of the poisonous Destroying angel" and presents a detailed description of a character preparing a cookie bake mixture from harvested Amanita muscaria.
Fly agaric shamanism—in the context of a surviving Dionysus cult in the Peak District—is also explored in the 2003 novel Thursbitch by Alan Garner.
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