The Zombie Wasp Fungus - Ophiocordyceps humbertii

My first time seeing the Zombie Wasp fungus, Ophiocordyceps humbertii. On Polistes sp. Etowah County, Alabama, May 16, 2023.

Around a month ago, while on a jaunt adjacent to the creek on my land in Northeast Alabama, I was overjoyed to accidentally stumble across such a bizarre and fascinating find. If my friend, Cassie, hadn’t stopped for photos of some Stemonitis sp., I don’t think I ever would have noticed the tiny monstrosity attached to the lower branches of a beech tree. The photos alone may evoke a visceral sense of unease and foreboding, and I can guarantee that reading the remainder of this blog post will only validate that intuition.

Ophiocordyceps humbertii is a parasitic, entomopathogenic fungus which specializes on wasps. The cycle of this particular infection likely begins on the forest floor, where wasps spend much of their days foraging. After initially being exposed to spores, a wasp is in all likelihood oblivious to the grim reality that its bodily tissues will be usurped by a vegetative mycelium over the course of a couple of weeks. In this covert-yet-hostile takeover, the mycelium hijacks the nervous system of its host, fully exploiting and manipulating the behaviors of the wasp in order to improve its own fitness.

At around 10-15 days post-infection, the wasp feels compelled to climb to an open, elevated position in which it can enhance both spore production and dispersal. Once it reaches its destination, it performs what its called “the death grip” (see photo #3 above for a closeup of this), clasping itself with its mandibles (and sometimes legs) to a nearby surface like a branch or a leaf. In some cases, a wasp will even cling to its own nest in order to directly infect the colony!

Having carried out this fungal directive, the wasp soon succumbs to death, meeting a brutal yet dramatically beautiful end. Fruiting bodies called stromata burst from every joint and suture of its exoskeleton, and the fungus concludes the mummification of the wasp’s body. At this point, the stromata mature, developing sexual structures called ascomata which will ultimately will release hundreds of thousands of spores into the forest understory. The cycle may then be repeated with the reinfection of new hosts.

If ever you are in need of a reminder of both our interconnectedness and vulnerability to nature, the Ophiocordcyeps genus is most assuredly a good place to start.

Born of Rain, Dressed in Flame

During late August 2022, only a few weeks after we had moved back to Alabama following a year-long journey to New England and back down through the mid-Atlantic, the entire family fell ill with the Omicron variant. I’m not exactly sure why, but I was the last to start exhibiting symptoms or test positive for the infection. It was pretty much impossible to isolate myself from my infected partner inside a 36’ RV, but I tried my best to spend as much time as I could sitting outside when I wasn’t providing him with fever reducers, water, and moral support.

Fortunately for me, the unusually balmy and mild summer (for Northeast Alabama standards) made it a lot easier for me sit outside for most of the day without overheating . The torrential rains that have become the norm these days in the Southeast served as a regular reminder that many fungi were flourishing out in the forest at that time—and that there was not much I could do to break myself away from my caretaker role to take advantage of that. What I didn’t realize at the time was that there were some very interesting fungi within just a few footsteps of where I had been sitting.

A few days passed, and my partner began to stir from his fevered state—while I had begun to feel more foggy and flushed (and panicked that I wasn’t actually going to escape this virus). My energy levels had dropped to well below my usual by that point—which is A LOT. Despite this, I was still trying to convince myself that I was going to magically evade getting “the full-on ickies”. I willed my wobbly body to amble around the RV in search of interesting things—anything—to distract me from what was on the way. In my restrained meanderings, I noticed long, rain-soaked grooves had formed in the iron-rich soil below the pole barn (due to the heavy rains and the gutter positioning). My eyes reflexively searched the still-damp soil for signs of fungal life.

And there they were—unapologetically announcing their existence—born by rain, dressed in flame. I dizzily stooped to admire them, photograph them, and probably even said a “hello” and a “thank you” before my analytical brain began to take the reigns.

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Surely this was something in the Pezizales order. The only thing that came to my mind at the time was Aleuria aurantia, the Orange Peel Fungus. The habit was right, but these were much more tiny than any of those that I had encountered. I definitely need the help from the mushroom community to figure these out!

I vaguely remember posting my photos on iNaturalist, tentatively labeling them as “Family Pyronemataceae”, before finally succumbing to “the full-on ickies” for several days. Even in my delirious state, my brain continued to try to piece it all together, but true progress would just have to wait for another day.

Once I began to recover, I posted my photographs to several mushroom identification groups and even my own personal Facebook page, stating that I thought these were possibly some “weird Aleuria”. Fellow enthusiasts were pretty quick to correct this thought or suggest other genera. Being an RSDer, I felt pretty embarrassed by my mistake—and quickly thanked everyone for their suggestions. They had to be right. How could I possibly be right? My experience surely pales in comparison to theirs.

Whilst having these online interactions, I was contacted by Rosanne Healy from the University of Florida, who researches fungi from the Pezizales order—and it turned out that she wanted to take a closer look at them (via DNA sequencing and microscopy). Once I had achieved a negative rapid test result, I collected some fungi samples from the original location, packaged them carefully, and shipped them off to her address in Florida. In the meantime, I decided to leave my ID at “Family Pyronemataceae” due to a split in community suggestions. The following are from my followup conversations with Rosanne:

9/13/22: Microscopically, it looks like Melastiza. Beautiful spores. I'll keep you posted when I get sequences.

11/15/22: I am sorry for not getting back to you - because your fungus is rather unique for GenBank submissions! The ITS was only 94% similar to Aleuria cestrica, and the LSU was 98% similar to Aleuria bicucullata. In the Pezizales, the ITS sequence should be at least 97% similar to be regarded as conspecific, so yours is pretty different! LSU is a more conserved region, so sequences should be at least 99% similar to be conspecific. Sooooooo, we need to do more work on yours to compare to species in the Aleuria and Melastiza genera to see if it morphologically matches one of those.

04/07/23: Hi Flown, I finally figured this one out! It is Aleuria cestrica! Pretty rarely found, but described from Pennsylvania. Such a great find!

Upon hearing the final verdict this past month, I was excited—but honestly a bit shocked to hear that my first reflexive ID was the best guess out of any. A wave of emotions passed over me—the most noteworthy of them being something akin to self-abandonment.

What makes me so quick to deny my own instincts? Why do I hold so strongly to the false belief that other people are less capable of making mistakes—and why am I so quick to fawn to anyone and everyone who challenges my thoughts or perceptions? Isn’t being wrong a part of being human? Isn’t it also an integral part of learning and discovery and science in general? Why do I always feel like an impostor? Would it be so bad if I were to place some faith in myself at the risk of being wrong?

Like most strong emotions, it’s been really hard to get these dislodged from my brain. I know that many scientists cringe at the anthropomorphization of nature, but I find a lot of comfort and connection in this practice. I could not help but imagine what Aleuria cestrica would say to me if it had a voice:

I will not extinguish my flame for anyone. I do not require discovery to affirm my existence, and I am extraordinary even when I am overlooked.