Michigan
Mushroom Hunters Club

This page is used to feature mushrooms that are prevalent for the particular time of the year or, during the winter months, to feature some of the less desirable or hard to find mushrooms. To see some of our previous stars follow this link to an index of previously featured mushrooms.

 March's Mushroom of the Month

Amanita virosa and A. bisporigera: the Destroying Angels

 Destroying Angel Amanit

The photo above features two bisporigeras and a virosa.

These two species of beautiful white mushrooms are among the most deadly mushrooms known.  According to Heather Hallan-Adams one cubic centimeter (roughly 1/3 cubic inch) of these mushrooms contains enough toxin to kill an adult.  Fortunately in the U.S., mushroom poisonings are rare; on average less than one person per year dies of mushroom poisonings.  In Europe where mushroom hunting is very common, the death rate is higher.  Most mushroom poisonings involve species that cause gastrointestinal distress rather than death.  The destroying angel complex of mushrooms occurs throughout the Northern Hemisphere with A. virosa being the European species, A. bisporigera and A. virosa (until given a new name) in the Eastern United States, A. ocreata in the Western U. S. and A. exitialis in Asia.  All of the species are very similar in appearance and all are deadly poisonous.

Amanita Virosa

An Amanita Virosa (photo above)

The white, convex to flat cap of Amanita virosa ranges from 2 to 5 inches (5 to 12.5 cm) wide.  The white, convex to flat cap of A. bisporigera ranges from 1 to 4 inches (2.5 to 10 cm.) wide.  The caps of both species are somewhat sticky when wet.  The cap of A. virosa is fleshier than the thinner cap of A. bisporigera.  The gills of both species are free of the stem, crowded and white.  The stem of A. virosa ranges from 3 to 10 inches (7.5 to 25 cm) long and 3/8 to 1 inch (1 to 2.5 cm.) wide.  The stem of A. bisporigera ranges from 2 to 6 inches long (5 to 15 cm.) and ¼ to ¾ inches (0.6 to 2 cm.) wide.  The flesh of both species is white.  Both species have a flaring to ragged ring which is ephemeral.  Both species have bulb shaped stem ends with a baglike volva.  The spore print of both species is white.  Generally A. virosa is larger and more robust than A. bisporigera.

Microscopically the two species are easy to distinguish.  The basidia (spore forming cells) of A. virosa usually form four spores whereas the basidia of A. bisporigera form two spores.  Macroscopically A. virosa is a more robust, larger mushroom than A. bisporigera.

Amanita virosa is a European name.  Modern analysis is placing mushrooms called A. virosa into the species A. bisporigera. 

Both species contain deadly amatoxin poisons.  The first symptoms of poisoning are gastrointestinal, vomiting, persistent diarrhea and stomach pains.  The gastrointestinal symptoms begin 6 to 24 hours after eating the mushrooms.  There often is a period of recovery from these symptoms lasting for one or two days.  After that the serious damage occurs as the toxins cause deterioration of liver and kidney functions.  Fortunately, a serum derived from milkweed plants has proven effective against the amatoxins and recently was approved for treatment by the Food and Drug Administration.

 Amanita Bisporigera

     Amanita Bisporigera