# Jack-o’-lantern (Omphalotus olearius)

**Omphalotus olearius* and *O. illudens**

**Known today as.** An orange mushroom clustered on the stumps and roots of olive and other hardwood trees.

Kind: Fungus  
Poisoning: Gastrointestinal irritants (https://thethinkingpress.org/materia-medica/poisons/gastrointestinal)  
Toxic: yes

> **Caution.** Poisonous.

## What was it used for?

None, though a derivative of its illudins has been tested against cancer.

## What does modern science say?

Its illudins cause violent vomiting; it is mistaken for the chanterelle.

## Pharmacognosy and toxicology

- **illudin S**: 
- **illudin M**: 

**Mechanism.** The illudins damage DNA; in the gut they cause the vomiting, and a synthetic relative, irofulven, was tried as a cancer drug.

**Dose.** A meal, mistaken for the chanterelle; severe but not typically lethal.

**Standing.** None; the mushroom glows faintly in the dark from its luciferin.

## What lore surrounds it?

Its gills glow faintly green in the dark.

The name these glowing gills share with the pumpkin lantern goes back to the folklore of the will-o’-the-wisp: an Irish legend of Stingy Jack, who outwitted the Devil, was barred from both Heaven and Hell, and was left to wander the earth with a burning coal in a hollowed turnip. The tale is folklore rather than history; the name jack-o’-lantern belonged first to the will-o’-the-wisp, the lights over bogs that learned writers put down to marsh gas, and from that deceptive glow the glowing mushroom takes its name.

## Sources

- Snopes, on Stingy Jack.
- Wikipedia contributors. “Omphalotus olearius.” *Wikipedia, The Free Encyclopedia*. en.wikipedia.org/wiki/Omphalotus_olearius (read 2 October 2026).
- Wikipedia contributors. “Omphalotus illudens.” *Wikipedia, The Free Encyclopedia*. en.wikipedia.org/wiki/Omphalotus_illudens (read 2 October 2026).
- Wikipedia contributors. “Jack-o'-lantern.” *Wikipedia, The Free Encyclopedia*. en.wikipedia.org/wiki/Jack-o'-lantern (read 2 October 2026).
- Kelner, M. J., et al. (1987). “Preclinical evaluation of illudins as anticancer agents.” *Cancer Research* 47.

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*Jack-o’-lantern.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-03. The Thinking Press. https://thethinkingpress.org/materia-medica/jack-o-lantern

Historical description, not medical advice.