Cordyceps: The Myth and the Mushroom

contributed by Glenn Kotnik (Zaleski, OH)

I’ll start by saying that I have more questions than answers about this elusive fungus. Cordyceps is listed in many “mushroom books,” yet it’s a matter of opinion as to whether or not the fruiting bodies of an Ascomycete, or “sac fungus” should really be called a mushroom. Purists often deny Ascomycetes the label mushroom, however in my neck of the woods, come April, the forest is packed with people hunting “mushrooms” using the term as though Carl Linnaeus himself had created the term mushroom as a royal taxon containing only the Ascomycete the morel. Still stranger is the question as to how the Cordyceps fungus became entwined with predictions of a dystopian future for humanity. So we wonder, what’s a nice mushroom like the morel doing in a Phylum with a harbinger of our dystopian future, Cordyceps? I’m afraid I’m getting ahead of myself here so I’ll back up.

It seems that every time I go on a hike in the woods with my friend Martha Bishop, I learn
something new. For example, early last fall we were out searching for the last mushrooms of summer and Martha showed me something she had excavated from a decaying log. Not really mushroom-looking at all. She explained that species of fungi in the genus Cordyceps are parasitic and have unsavory dietary preferences. They grow into, and then out of, the bodies of living insects, usually larvae or pupae which are in rotten logs or underground. Only the ascocarp, the slender fruiting body of the fungus is visible above the surface of a rotten log or the earth.

Of the 600 or so species of Cordyceps found worldwide, some of these, especially tropical
species, parasitize the living adult insect. As Cordyceps mycelium grows into the live insect, the fungus doesn’t kill the insect immediately. The pupa, larva, or adult insect retains vital functions needed for life but ceases its normal insect behavior. In the case of certain adult insects, it may climb up a plant or tree, seemingly to a microenvironment where temperature, humidity and light are most favorable to the Cordyceps. Here is where science becomes entwined with mythology, scenarios evolve that would cause Kafka to lose sphincter control, our dystopian future looms.

It’s not hard to understand how fungal mycelium growing inside the living organism disrupts
metabolic, neurologic and muscular function with the final result being, as one would expect,
death. To complicate matters, a variety of chemicals are released inside the insect by the
Cordyceps mycelium. Many of these chemicals have been studied for their medical potential. Traditional Chinese medicine has used extracts of Cordyceps fungus for centuries and as with most folk medicine pharmaceuticals, have been said, at various points in time, to cure virtually all human ailments. In the minds of the hopeful, “used to treat” equals “proven to cure”.

One can see how slowly growing mycelium in one’s innards can cause strange muscle movements and very strange behavior as the hyphae enter and begin to digest the brain and neurons. The digestive process is what it’s all about, really; the Cordyceps just wants a bite to eat — it’s a parasite, after all. The disrupted movements of the insect as it is being slowly digested from the inside out have led to the name “Zombie Fungus.” Imagine a world populated by zombie insects, and from there it’s a short leap of the imagination to consider humans becoming infected with Zombie Fungus. Now you can glimpse the occupants of our dystopian future, animated not by their own brains but by Cordyceps hyphae controlling all of their synapses. A grisly future at best.

Hard to believe? For anyone with too much time on their hands, check out the video game from 2013, “The Last of Us” and its sequel, “The Last of Us: Left Behind.” For those who prefer to get their myco-mythology in a print version, try “The Girl With All The Gifts,” a novel available in Kindle or traditional book form. It’s about a young girl, but a girl living in our dystopian future of course, a future which is dystopian because, among other reasons, almost everyone has had their central nervous systems taken over by a mythical species of Cordyceps fungus.

Back to reality, dystopian as it may seem at times. My hiking companion Martha Bishop was
generous enough to give me the Cordyceps specimen she had excavated from a decayed log in a deep Appalachian hollow. First, I did some photographs of the wasp with the ascocarps growing from its head. (Figure1) Ascocarps are the fruiting bodies of Ascomycetes, like the frying pan part of a morel. The ascocarps contain perithecia, a structure which in turn houses asci, the finger-like projections which contain spores. When the spores are released from the ascocarp, some will find their way by chance to another insect host which will be parasitized as well.

Parasitized wasp with ascocarps

The wasp after the ascocarps fell off is shown in Figure 2; mycelium can be seen on the
exoskeleton, presumably Cordyceps mycelium.

Wasp with external mycelium

The dried, shriveled ascocarp is seen in Figure 3.


Next, I attempted to cut thin sections of the wasp after embedding it in paraffin. I put some of these on microscopes slide and stained them with phloxine. I don’t claim to be a trained
microscopist; although I did view many specimens with a microscope in college, my
technique for preparing specimens is poor. It does appear that fungal hyphae can be seen both inside, and external to, the exoskeleton of the wasp. Note the bristles which identify the

Thin slice of Infected wasp
Thin slice of Infected wasp
Thin slice of Infected wasp

There is much more that can be learned about Cordyceps and other closely related fungi.
Those who have not been frightened away or who dread the night when their dreams will be
visited by hungry mycelia can find a huge amount of information available, some reliable,
some more prone to myth. I hope that anyone who hikes the mushroom woods will become
aware of the possibilities of finding extremely interesting and unexpected mysteries below the most banal and unpromising little sprouts. Always consider that it could be the ascocarp of Cordyceps.

The most interesting part of a fungus may be underground.
These little stalks, similar to Cordyceps, grow from a fallen plant seed. They are probably a species of Xylaria.