Bolbitius titubans, commonly known as the Yellow Fieldcap, is a small, delicate agaric mushroom often appearing in grassy areas such as lawns, pastures, and meadows, particularly after rainfall. Distinguished by its bright yellow, slimy cap when fresh, which soon fades and becomes fragile, this species is notable for its short-lived nature, sometimes collapsing within hours of emerging. The stem is slender and hollow, supporting pale gills that quickly turn brown as the spores mature. As a saprobic fungus, it contributes to the decomposition of organic matter in soil and grass. Its sudden appearance and rapid disappearance make it a fascinating, fleeting find for both mycologists and casual observers alike.

Cap bright yellow when young, egg-shaped to conical, soon expanding to convex or flat and quickly fading to whitish or pale tan. The surface is smooth, viscid when fresh, often becoming lined or striate with age. Gills narrowly attached or almost free, fragile and soft, starting pale yellowish and turning cinnamon to rusty brown as the spores mature. Stem slender, hollow, white to yellowish, finely powdery or downy near the apex and base, very delicate and easily collapsing. The stem has no ring. Spore print cinnamon to rusty brown.

Microscopic Features: Spores are ellipsoidal, smooth, measuring 11–15 × 6–9 µm.

Bolbitius titubans on the First Nature Web site.
Bolbitius titubans on the MushroomExpert.Com Web site.