Bolbitius titubans: The Ultimate Mushroom Guide
About The Bolbitius titubans Mushroom
Bolbitius titubans (Bolbitius vitellinus) is a widespread species of mushroom found in America and Europe. It is a small, yellow, attractive mushroom that is easily recognized by its viscid, striate cap, yellow-brown gills, rust-brown spores, lack of a ring, and habit of growing either on dung or grass. It grows chiefly on dung or heavily fertilized soil, and sometimes on grass.
Like many small Coprinus (s.l.) species, fruitings are ephemeral, mushrooms opening in the morning, then shriveling by the end of the day. Occasionally, unusually robust specimens are found which may persist for several days.
Bolbitius titubans is generally regarded as inedible, and its small size and thin flesh mean that there is little temptation to try eating this insubstantial mushroom.
Other names: Yellow Fieldcap.
Bolbitius titubans Identification
Saprobic, growing alone, scattered, or gregariously on dung and in fertilized grass; summer and fall (and winter in warm climates); widely distributed in North America.
1.5-5 cm; egg-shaped or nearly round when young, expanding to broadly bell-shaped or broadly convex, and eventually flat with a depressed central bump; fragile; slimy when fresh; yellow or greenish-yellow (sometimes brownish or grayish), often fading to grayish or pale tan but (usually) retaining a yellowish center; smooth; usually strongly lined by maturity, often nearly all the way to the center. Specimens developing a pocketed or veined cap surface as the slime dries out are not infrequent. Young specimens sometimes display a felty, whitish cap margin, but this appears to be the result of contact with the stem (which also features the feltiness) in the button stage, rather than remnants of a true partial veil.
Free from the stem or narrowly attached to it; close; fragile and soft; whitish or pale yellowish, becoming rusty cinnamon; often gelatinizing somewhat in wet weather.
3-12 cm long; up to nearly 1 cm thick; equal or tapering to the apex; hollow; fragile; finely scaly, powdery, or finely hairy--or more or less smooth; white with a yellowish apex and/or base, or yellowish overall.
Odor and Taste
KOH on cap surface negative to dark gray.
Spores 10-16 x 6-9 µ; more or less elliptical, with a truncated end; smooth; with a pore. Brachybasidioles and cheilocystidia are present. Basidia abruptly clavate. Pileipellis a hymeniform trichoderm.
Bolbitius titubans Look-Alikes
A tropical species in the Bay Area occurs mostly in greenhouses, is similar in size and cap color but the cap is not viscid, the gills are free, there is a ring, and the spores are white.
A longer-lasting mushroom; it grows on wood rather than on grass, and its spores are pink rather than cinnamon brown.
Bolbitius titubans Taxonomy & Etymology
Described in 1789 by French mycologist Jean Baptiste Francois Pierre Bulliard, who gave it the scientific name Agaricus titubans, this little mushroom was renamed Bolbitius titubans in 1838 - a time when most gilled fungi were initially placed in a giant Agaricus genus, now redistributed to many other genera - by Swedish mycologist Elias Magnus Fries. A very rare variety Bolbitius titubans var. olivaceus was defined in 2000, and so the nominate variety of the Yellow Fieldcap is now formally referred to as Bolbitius titubans var. titubans.
Synonyms of Bolbitius titubans include Agaricus fragilis L., Agaricus equestris Bolton, Agaricus titubans Bull., Agaricus flavidus Bolton, Agaricus boltonii Pers., Agaricus vitellinus Pers., Prunulus boltonii (Pers.) Gray, Prunulus titubans (Bull.) Gray, Bolbitius boltonii (Pers.) Fr., Bolbitius fragilis (L.) Fr., Bolbitius titubans (Bull.) Fr., Bolbitius vitellinus (Pers.) Fr., Bolbitius flavidus (Bolton) Massee, Bolbitius vitellinus var. fragilis (L.) M.M. Moser ex Bon & Courtec., and Bolbitius vitellinus var. titubans (Bull.) Bon & Courtec.
Bolbitius, the genus name, means 'of cow dung', although note that the Yellow Fieldcap prefers well-rotted dung and tends to shun fresh cow pats.
The specific epithet titubans means staggering or wavering.
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