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, hadnβt stopped for photos of some Stemonitis sp., I donβt 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 βthe death gripβ (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 waspβs 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.
