Cornell University

A spider’s nightmare

In the contest for Ickiest Thing, spiders and molds are about neck and neck. Personally, I’m rooting for molds. To demonstrate their clear superiority over spiders, I now present these two tableaux of death, captured in glorious detail by photographer Kent Loeffler.

This first little fungus, a mold called Nomuraea atypicola, is not dangerous to you or I, but as you can see, it is a mortal enemy of spiders. It’s not just growing on the spider, like a bad case of athlete’s foot. No, it has consumed it from the inside, and it is now making a kajillion pinkish spores on the cadaver. Kind of like that old movie, Invasion of the Body Snatchers. This spider is thoroughly dead.

Quicktime 5+ object

Rotatable, zoomable Quicktime object by Kent Loeffler

Here’s another one, related but quite distinct. This is Gibellula pulchra, another spider pathogen. It too kills only spiders, infecting them when fungal spores land on the unfortunate spider. Those spores germinate and directly penetrate through the exoskeleton, then the fungus begins to grow inside the spider. It just grows and grows until it has digested the whole spider. Fungi digest their food by excreting their digestive enzymes right into it, then absorbing the products of digestion–can’t be very nice for the spider. The fungus doesn’t bother to eat the exoskeleton, which is tough and chitinous and hard to digest. That’s why the cadaver is still recognizably a spider.

When all that devouring is done, it’s time to sporulate. Now the fungus erupts from the cadaver and makes the tiny leafy trees you see covering the spider body. The trees (ok, they’re called synnemata) produce vitamin-shaped spores that are presumably carried by the wind to unlucky spiders. Fungi are classified based on how they make their spores. Gibellula species make those tiny trees; Nomuraea species don’t. There are hundreds of mold genera–all make their spores in different ways.

Quicktime 5+ object

Rotatable, zoomable Quicktime object by Kent Loeffler

We don’t know all that much about how these pathogens affect spider ecology. How do they impact spider populations? How often can spiders fight off a fungal infection? How are they transmitted? How many spider species are suceptible? And I can anticipate your inevitable question: How can I use these to kill the spiders in my house? I don’t have answers for you. In the basement of my old house, with no help from me, pholcid spiders often died from fungal infection. They suffered from yet another mold, Engyodontium aranearum, which never managed to kill ALL my spiders, alas.

On days like this I ask myself, how did I get to this strange place? I don’t know, but I love this stuff.

These spiders died under leaves in Florida. Finding them involved sharp eyes and a lot of creeping around and leaf flipping–Mindy Liu did that. The dead spiders now make their home in the Cornell Plant Pathology Herbarium, one of the biggest fungal herbaria in North America. We have all kinds of weird and wonderful fungi, a bunch of plant diseases, and an impressive collection of historic photographs. We’re 99 years old. We’re not open to the public; you’ll have to stay tuned here for more stories.

  • Evans, H. C., and R. A. Samson. 1987. Fungal pathogens of spiders. The Mycologist 1:152-159.



6 Responses to “ A spider’s nightmare ”


Most people don't pay much attention to fungi, which include things like mushrooms, molds, yeasts, and mildews. Here at Cornell we think they're pretty fascinating. In fact, even the most disgusting foot diseases and moldy strawberries are dear to our hearts. We'd like to talk to you about fungi, so that like us, you too can tell gross stories at the dinner table. Afterwards, maybe you'll notice some things you would have overlooked before, and we think this could be good for the planet.

Kathie T. Hodge, Editor

Beneath Notice, our book of borescopic mycology.


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