The Jack-o'-lantern mushroom (Omphalotus olearius) is a common wild mushroom which may be distinguished by its funnel-shaped cap and its bright yellow to orange color. It is usually found from July to November in woodland areas of North America, where it grows on decaying stumps, buried roots or at the base of hardwood trees, especially oaks. The mushrooms are produced in clusters of various size and they emit a sweet fruity aroma, attractive to some and offensive to others. The Jack-o'-lantern mushroom should not be eaten because it is poisonous to humans. It contains toxic chemicals that can cause severe stomach upset accompanied by vomiting, diarrhea and headache. This mushroom also produces other substances similar to those found in fireflies and glowworms, which cause the gills to emit a greenish glow in the dark, known as fox fire. This light emission phenomenon is called bioluminescence, and even though its role in the animal world is quite well understood, its function in the Jack-o'-lantern mushroom is not yet clear.
Medicinal properties have been attributed to this mushroom. In fact, some of its toxic substances have been found to be a source of an anticancer agent known as irofulven. The mechanism by which these agents destroy cancer cells is not yet well understood, but it seems to be different from that of other anticancer drugs.
The Jack-o'-lantern mushroom may be confused with another woodland species, the sulfur mushroom (Laetiporus sulphureus), which also grows on trees, and it is edible for some people during its early stages of growth. One may differentiate the two species by looking at the underside of the caps. The Jack-o'-lantern mushroom has long thin gills that run down to the stalk, whereas the sulfur mushroom has a smooth surface scattered with microscopic pores.
Another common and extremely delicious mushroom that somewhat resembles a jack-o'-lantern in its color is the chanterelle (Cantharellus cibarius). The chanterelle, however, grows scattered singly on the ground, and has a thicker flesh. Needless to say, when in doubt, it is always advisable to consult with a mushroom expert before bringing your mushroom to the table.