Omphalotus olearius

The jack o'lantern mushroom (Omphalotus olearius) is an orange to yellow gill mushroom that to an untrained eye appears similar to some chanterelles, and is most notable for its bioluminescent properties. Previous names include Omphalotus illudens and Clitocybe illudens. Unlike the chanterelle, the jack o'lantern mushroom is 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 only observable in low-light conditions when the eye develops night vision. The whole mushroom doesn't glow&mdash;only the gills. This is due to an enzyme, called luciferase, acting upon an unspecifed chemical, leading to the emission of light much as do fireflies when glowing.

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

Description
The Jack-o-Lantern mushroom's fruiting body (its stem and cap) is an orange color. Underneath the cap is its well known glowing color, which glows in a blue-green color.

Similar Species
The similarly poisonous mushroom Tsukiyotake (Omphalotus japonicus (Kawam.) Kirchm. & O.K. Mill., aka Lampteromyces japonicus (Kawam.) Sing.) found in Japan and eastern Asia emits light similar to that of the jack o'lantern mushroom, and contains the same poison (Illudin). It was confirmed that Tsukiyotake was a companion of jack o'lantern mushroom in 2003. The poisonous Western jack o'lantern mushroom, Omphalotus olivascens is abundant in South & Central California, it is also similar to the chanterelle but can be distinguished as its flesh is never white.