Observation 23767: Amanita frostiana (Peck) Sacc.

When: 2009-07-31

Collection location: Forest near Elgin St., Pembroke, Ontario, Canada [Click for map]

Who: Paul Derbyshire (Twizzler)

No specimen available

Found in Zone 07, but by no means the most interesting observation from Zone 07 today.

Species Lists



Proposed Names

-8% (3)
Recognized by sight: Yellow patches, stipe, etc.; the usual
63% (4)
Eye3 Eyes3
Recognized by sight: striated cap margin is ONE of the features of frostiana but without pictures of the bulb and seeing if the spores are amyloid or not it’s just a Could Be

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Eye3 = Observer’s choice
Eyes3 = Current consensus


Add Comment
Don’t know how it got the rep.
By: R. E. Tulloss (ret)
2012-08-30 20:57:12 CDT (-0400)

However, if someone were to ask me if a species of sect. Amanita were toxic and I had morphological evidence of close relationship to muscaria or pantherina, my response would be to encourage a great deal of caution.

In New Jersey we so rarely see frostiana that there is no opportunity to collect sufficient material for a chemical assay for ibotenic acid or related compounds.

If frostiana is to be studied chemically, it will have to rely on collectors to our north, where the species seems a bit more frequent.


By: Erlon (Herbert Baker)
2012-08-30 19:18:36 CDT (-0400)

I see NAMA has placed A. frostiana in the group of mushrooms containing isoxazole derivatives along with A. muscaria. Yet, I can find no documented cases of any poisonings with this mushroom. In fact, some have claimed that it is completely edible.

I suppose this is due to Atkinson labeling it as poisoness because he believed it to be a variety of A. muscaria.

Yes, all in one (mixed) collection.
By: R. E. Tulloss (ret)
2012-08-30 18:19:45 CDT (-0400)

Remember that cap color was probably the dominating feature; frostiana was originally considered a small variety of muscaria. A striate cap margin was not considered a significant character of a muscarioid group—in fact lepidellas and the Validae were mixed with what we now think of as the muscarioid group.

The modern sections were undefined. In fact contemporary section were totally mixed in the subdivisions that existed at the time. Presence or absence of an annulus and the form of the volva (in a very simplified classification) were common methods of breaking up the genus into subgroups.

As an example, take a look at Gilbert’s 1917 summary of the state of knowledge in Amanita and compare Gilbert’s 1940-41 masterwork (“Amanitaceae”). A big change had occured between those years.


type collection
By: Erlon (Herbert Baker)
2012-08-30 17:14:40 CDT (-0400)

strange that the type collection would have both species, were they collected at the same time and location?

I am very fond of old hand-written notes in herbaria.
By: R. E. Tulloss (ret)
2012-08-30 12:35:45 CDT (-0400)

It’s like finding someone else’s buried treasure. In this case, the non-striate margin probably means that the collector found A. flavoconia. In 1906, the latter species had not been described and was often mistaken for frostiana. In fact (I think it was David Jenkins) some reported that even Peck’s type collection of frostiana includes a mixture of flavoconia. The amyloid reaction was not used in taxonomy until the 1920s. Also, the idea of measuring spores in lateral view only was not common at all until recently. For example, even in the 1980s and 1990s Reid and others clearly measured spores however they presented themselves. Even now, we all use field guides that say or imply that some amanitas have perfectly globose spores. When I was starting out in the 1970s and 1980s, it was very common to provide only a single dimension for spores of species like “A. virosa” (really A. bisporigera) because of the way spores were measured.


Thank you.
By: R. E. Tulloss (ret)
2012-08-30 12:27:12 CDT (-0400)

Microscopic characters vary, but within a range. For example, the range of variation of spore size for a species with mostly subglobose spores is much smaller than the range of variation for the spore size for a species with mostly cylindric spores. I’ll take a look at the link.


Rod [edit]
By: Erlon (Herbert Baker)
2012-08-30 12:12:59 CDT (-0400)

sorry to hear about your health problems. :(

If i come across some “frostiana” like specimens I will send them off to you.

Thanks for everything, you’re the best!

I found these notes ffrom the University of Michigan Herbarium, not sure if it is helpful at all. http://quod.lib.umich.edu/f/fuwatic/x-008/WN16 collection date 1906, herbarium number 1939. It is interesting that they show in the drawing just the very base of the bulb is white and the stipe is yellow.

Is it possible that the microscopic features could be variable as well?


I see frostiana rather rarely.
By: R. E. Tulloss (ret)
2012-08-30 11:49:00 CDT (-0400)

It is very uncommon in the areas in which I collect; and my work and diabetes has greatly reduced the time spent collecting. It is plausible that a species with a yellow volva would sometimes have yellow on the stem. Off the top of my head, this is the only strongly yellow stem I’ve ever seen on a possible/probable frostiana. There’s no herbarium specimen, right? So we can’t do the obvious things to check our guesses regarding the photo. Unfortunately.


yellow stipe
By: Erlon (Herbert Baker)
2012-08-30 09:56:28 CDT (-0400)

is this something you typically see in A. frostiana?

from your website Rod, regarding A. frostiana. "The white stipe is “47- 62 × 4 – 11” mm (94 × 6 mm in my only annotated collection) and bears a persistent annulus. The distinct and starkly white bulb (e.g., 17 × 15 mm) bears a white or yellow-white collar that is somewhat similar to the collar seen in the exannulate Amanita albocreata G. F. Atk."

another reason so say “frostiana”
By: R. E. Tulloss (ret)
2009-08-01 11:29:55 CDT (-0400)


I think that the fact that the short gills are squarely truncate is another point in favor of A. frostiana; also, the two-color pigmentation of the cap is more typical of frostiana than flavoconia.

Very best,


Created: 2009-08-01 02:08:52 CDT (-0400)
Last modified: 2014-12-08 21:18:35 CST (-0500)
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