Observation 12136: Amanita frostiana (Peck) Sacc.
When: 2008-08-05
No herbarium specimen

Proposed Names

97% (6)
Eye3 Eyes3
Recognized by sight
-6% (4)
Recognized by sight: see Rod’s post; looks like it can’t be IDed to sp. from the photo alone.

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Eye3 = Observer’s choice
Eyes3 = Current consensus


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I’m glad to hear your experience
By: R. E. Tulloss (ret)
2008-10-09 11:52:36 CDT (-0400)


It’s great to have your personal view on determining this species. I rarely see it in my part of New Jersey. If you run into it again, I would always like to have more dried material. It really should be included in more detail in future DNA work on muscarioid taxa.

Very best,


By: Noah Siegel (Noah)
2008-10-08 22:29:05 CDT (-0400)

When you have a good collection of frostiana it looks different from flavoconia. The best macro differences as Rod eluded to is the ringed bulb, flavoconia is usually (but not always) tapered; the striated cap margin, once again flavoconia can have a striated margin when old or dry but usually isn’t uniform. I have seen both yellowish and white stalks growing together so I don’t think color of stalk is a good feature.
I used to check the spores when I thought I had found A. frostiana and was always right so since have stopped doing it.
Is this a 100% id without doing the microscopic work, no, but I’m still at least 95% sure

okey doke. I’m still struggling with the Eastern amanitas myself.
By: Debbie Viess (amanitarita)
2008-10-08 13:02:42 CDT (-0400)
I guess I wasn’t clear on my opinion of the present collection.
By: R. E. Tulloss (ret)
2008-10-08 11:00:59 CDT (-0400)

I believe that Noah is correct in his determination of this collection. From my personal experience in collecting and traveling with him, I know that he knows many northeastern species well.

Take a look at my caveats. I actually point out that the marginal striations are present on all the mature specimens in this collection. The bulbs are largely recognizable as frostiana bulbs. I rated the likelihood of a correct ID at the top level. (Of course, noone knows who the second voter was, but it was me.) It’s important to consider that we are talking about probabilities here, not absolute certainty. No matter how many odd little macroscopic characters you can absorb into your database. There’s always the thing you never saw before that can throw your judgment into a tizzy.

From a teaching point of view, I would be very happy if a student identified this specimen as a probable A. frostiana. Then I’d ask her/him to check the spores, too. There are several parts to the job, several layers to the tool kit.

Very best,


check Rod’s description for frostiana…
By: Debbie Viess (amanitarita)
2008-10-08 10:29:45 CDT (-0400)

…he claims that the stipe is white, with a disctinctly white bulb. colors in amanita can fool you, and macro-characters can seem to be one thing when its really another. scope work essential to this ID.

nice collection, though!

By: Paul Derbyshire (Twizzler)
2008-10-08 01:21:13 CDT (-0400)

But I have about as much access to Meltzer’s reagent as I do to a microscope (right now, none whatsoever). :-)

I’ll keep the stem base/cap margin in mind. I also have the feeling A. flavoconia tends to be of smaller stature.

recognition without scope
By: R. E. Tulloss (ret)
2008-10-07 21:21:43 CDT (-0400)

Note that only the two youngest specimens lack marginal striations on the cap. [Added: That means the three mature ones HAVE striate margins — a positive for frostiana.] Amanita frostiana is related to A. amerimuscaria. In fact, Peck once called it Agaricus muscarius var. frostianus. Also, the bulb often is ocreate (like pantherina); or the stipe and bulb display a set of rings of volva — as in muscaria. Note, however, that old or whimpy specimens of A. flavoconia can have more or less distinct marginal cap striae. And, on the other hand, some specimens of A. frostiana can have very little volva on the stipe or bulb…depending on environmental conditions or collecting accidents.

One other thing you could check (on the relevant Amanita Studies pages) is whether the shape of the short gills (lamellulae) differ in the two species. I just can’t remember at the moment.

Testing for spore amyloidity (easiest) is very valuable and doesn’t require a microscope if you can gather a little pile of spores from a print (don’t scrape up paper if that is what underlies the spore print (you may well get a positive reaction from fibers of the paper).

Also, the drastic difference in spore shape between the two species (subglobose for frostiana and ellipsoid for flavoconia var. flavoconia) is an additional point to check if you have a scope. With flavoconia var. inquinata, the spore shape difference in comparison to frostiana is NOT so striking.

Remember, when gathering spores to make a little mound for testing with Melzer’s reagent, test on a chemically neutral surface like glass or a ceramic tile (or plate). Paper and wood are likely to produce an amyloid reaction of their own.

Very best,


By: Paul Derbyshire (Twizzler)
2008-10-07 20:55:42 CDT (-0400)

How is this species distinguished from A. flavoconia? Only microscopically?

Created: 2008-10-07 20:17:38 CDT (-0400)
Last modified: 2015-03-12 12:02:54 CDT (-0400)
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