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Jack-o-lantern Mushrooms

October Nature Notes: Luminescent cells of one mushroom set the woodland aglow.

Appearing in October, orange as a pumpkin and emitting an eerie Halloween glow, Omphalotus illudens is associated with the supernatural cavortings of witches, goblins, and other spooks, earning it the common name jack-o-lantern mushroom. The striking pumpkin-hued mass of mushrooms erupts from the ground as a cluster that springs from a central point in a tangle of long, tapered, pale orange stems, each competing for space to expand its cap. They emerge as an abundance of umbrella-like fruits, then mature to sunken, vase-shaped forms; margins are incurved at first, becoming upturned and wavy. Narrow, sharp-edged gills crowd the cap and descend the stalk.           

Luminescent cells in the gills on the underside of the cap emit an eerie lime green glow that is observable in low-light conditions with acclimated eyes. Known as “foxfire,” the phosphorescence is produced by the enzyme luciferase, the same chemical that allows fireflies to glow. Bioluminescence benefits the firefly in attracting a mate, but luciferase is believed to be a waste product for the mushroom, transported to the gills to eliminate it.          

Although it looks and smells appealing, the jack-o-lantern mushroom is toxic.

Carol McFeeters Thompson is a regular contributor to OutdoorIllinois and the site interpreter at Weldon Springs State Recreation Area.  

By: Carol McFeeters Thompson