Amanita muscaria : American Yellow-warted Fly Agaric

Amanita muscaria
Amanita muscaria
Amanita muscaria


Technical description not yet available.


Amanita muscaria subsp. flavivolvata is the common, bright red fly agaric of North and Central America.

Its red cap is 50 – 215 mm wide. The pigment rapidly fades in sunlight. The volva is distributed over the cap as yellow warts, and these also fade rapidly in sunlight. The last places to find yellow volval material are under the cap edge, under the annulus, and in the soil around the stipe base and bulb.

The gills are free to narrowly adnate, crowded to subcrowded, and pale cream to pale yellowish white to white both in mass and in side view. The short gills are truncate.

The stipe is 45 – 190 x 10 – 25 mm and has a skirt-like annulus and notable bulb of rather variable shape (19 – 61 x 18 – 50 mm). Rings of volval material commonly encircle the top of the bulb and the base of the stipe.

The spores measure (7.5-) 9.0 – 12.9 (-19.0) x (5.5-) 6.5 – 8.6 (-11.5) µm and are broadly ellipsoid to ellipsoid (infrequently elongate, very rarely subglobose or cylindric) and inamyloid.

This subspecies apparently contains the same toxins as Amanita muscaria (L.:Fr.) Pers. subsp. muscaria of Europe,

<img src="" alt="Amanita muscaria" width="150" height="234" class="aligncenter size-full wp-image-1087" /> northern Asia, and far northwestern North America (western Alaska). Amanita muscaria subsp.

flavivolvata occurs from southwestern Canada through the Sierra Nevada and the Rocky Mountains to the mountains of the desert Southwest and at least as far south as the montane oak forests of Costa Rica. There are also significant populations in the U.S. Gulf Coast region. Isolated occurrences have been noted as far north as Massachusetts on the U.S. Atlantic Coast. Colombian material may have been imported with pines. Argentine material that may be this taxon is also, clearly imported, although the symbiont is not known to me. In Argentina, the Euro-Asian A. muscaria var. muscaria has also been imported.

The species is associated primarily with oak and diverse conifers, but can occur with other deciduous tree genera.

As an aside, there is a cistern in a meadow formed by a long-dead crater on the volcano, La Malintzi, in the state of Tlaxcala, Mexico. Picnickers or perhaps those who pasture animals in the meadow make a practice of throwing fruiting bodies of A. muscaria var. flavivolvata into the cistern. See photo at right. [I am grateful to M. en C. Alejandro Kong Luz and M. en C. Adriana Montoya Esquivel (Universidad Autónoma de Tlaxcala) for taking me to the site on La Malintzi and describing to me how the mushrooms get into the cistern.] — R. E. Tulloss

Photos: R. E. Tulloss (top row – Arizona, California, Arizona)