How to identify slime molds

I am one of those observers who gets bothered when my observation sits too long unidentified. It motivates me to learn something new so that I can proactively move the ID forward myself.

Tonight, the observations bothering me is a slime mold. I am looking through pages of other slime mold observations, trying to find the nearest match. The problem is, of the ones that look most like mine, some are identified as a rarely-observed species, and others are not identified to species. Complicating this, there is a very commonly-observed species which at some stages looks kind of like mine, although most observations of it are at a stage that does not.

My Google search “slime mold identification” is just silly – mostly, the results are about how to tell if something is a slime mold. Is there a better source than just guessing which iNat observation is the best match?


I’m a newly minted slime mold enthusiast, and I’m struggling with this, too.

I’ve begun bringing samples home with me from the woods in hopes that they’ll develop into something recognizable. I’ve had mixed results, so far.

I joined the Slime Mold Identification & Appreciation group on Facebook and getting to look at lots of posts every day has been educational. I’ve posted photos a few times and gotten suggestions, too.

One of that group’s administrators, Peta McDonald, has put together a
dichotomous identification key and I’m optimistic that it will help once I get a microscope.

Best wishes!


Here is a website
The Editor in Chief is the author of Myxomycetes A Handbook of Slime Molds.
Hope this helps.


Is there an iNat project for slimemoulds? That would bring together people who are interested in observing with taxon specialists.

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Yes, World Mycetozoa RG
It was built as part of an umbrella project. It could be modified to not just RG if that is a desire.


There would be several more observations if it were not restricted to RG.


…a phrase one would probably only find on iNaturalist!


…which means I’m not optimistic about it helping with my existing observations.

I regularly identify slime moulds (molds) on iNat, and usually check the observations every day.

Some species are quite easy to identify, especially if the photos are good enough and they capture the various features necessary for identification, but many require microscopic examination, or SEM.

One of the problems with identifying even the common species is that they change shape and colour as they develop and progress from the plasmodium to the fruiting body stage. If people post only one photo that captures one moment in the development of a slime mould, it makes it very difficult to identify.

I have been observing and photographing slime moulds in northern Tasmania since 2010. I have a website that includes posts with ‘time lapse’ photos that show the development of some species to give an idea of how they change over time. (Stemonitis, Arcyria, Paradiachea), plus it has an illustrated glossary and a key.
The website also includes pdfs of many of the species I have found at my study site.

I have just published the fourth edition of my book “Where the Slime Mould Creeps” and will update details of availability on my website.
I hope it is useful.


I had wanted good examples for the original umbrella project but I’m fine to alllow Needs ID in the project. Especially when considering that there are many that do not move on to RG. I’m just going to wait a bit after putting a comment about it in the project journal to see if I get feedback to the contrary.


Oh my, what gorgeous photos! Your site is a great resource. :star_struck:


So I take it that you were unable to identify mine – assuming that you saw them shortly after I uploaded them.

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I was unable to identify your photo of the plasmodium. Identifying myxomycetes at the plasmodial stage is a bit like expecting people to identify plants from a photo of their roots.
I identified your observation of Fuligo septica. F. septica is probably the most common myxomycete observed on iNat. I do not spend a lot of time identify the species as it is one that other people can easily identify.


Well, seeing as that is standard iNat procedure – one organism at one moment in time – that raises a question: if the “time lapse” series are linked via comments, would that help to get all of them identified? I ask because that didn’t work with a moth.

Oh, wow, you’re the slime mould lady! I have heard about you on the radio, and probably saw you on GA as well.

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Interesting question. If I take time lapse series I tend to include them in one observation, despite that not being standard iNat procedure.
If ‘time lapse’ are posted as per standard procedure and linked by comments, this poses particular challenges for people in my position i.e. living relatively remotely with very slow internet. I spend a lot of time as it is identifying myxos on iNat.
To answer your question: No it would not necessarily help to get them all identified. Many require microscopic examination and specialised texts to compare; species in the Stemonitidacea sometimes require SEM. Cribraria are known to be impossible to identify in some cases.
And then there is the problem of the great variety of form you see in fruiting bodies that arise from the same plasmodium.
There is an additional problem of finding undescribed species, as I have done at my study site. They include 4 now described, one in the process of being described and 3 awaiting DNA to confirm that they are undescribed species.
Most of the work on myxos has been in the northern hemisphere and south America, with little work on Australian species that resemble but don’t match published descriptions.

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I removed the RG restriction and added Needs ID

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