Jack O'Lantern (mushroom)

The Jack O'Lantern mushroom (Omphalotus olearius) is an orange to red gill mushroom that is similar in appearance to the chanterelle, and most notable for its bioluminescence properties. Previous names include Omphalotus illudens and Clitocybe illudens. Unlike the chanterelle, the jack o'lantern mushroom is very poisonous. While not lethal, consuming this mushroom leads to very severe cramps, vomiting, and diarrhea. Complicating its toxicity is the fact that it smells and looks very appealing, to the extent that there are reports of repeat poisonings from individuals who were tempted to try them a second time.

Its bioluminescence is generally only observable in low-light conditions with acclimated eyes. The whole mushroom doesn't glow—only the gills. This is due to luciferase, the same chemical that fireflies use to glow. However, in this case, the luciferase is a waste product, and is transported to the gills to get it out of the mushroom.

Unlike the chanterelle, the jack-o-lantern has true, sharp, non-forking gills; this is the only "simple" trait for distinguishing between the two.