Cyclocybe erebia

What You Should Know

Cyclocybe erebia (Agrocybe erebia) has a dark brown, sticky cap that is often a little bit wrinkled. Its gills run down the stem by a decurrent tooth, there is a flimsy, flaring ring on the stem, and the spore print is brown. Many of the fieldcaps can have darkish caps when young, but C. erebia is the only one that remains mid to dark brown through to maturity rather than fading to buff.

While edible, it should be avoided as it can be confused with deadly poisonous species.

Other names: Dark Fieldcap.

Cyclocybe erebia Mushroom Identification

1. Ecology

   Saprobic; growing scattered or gregariously on the ground in woods under hardwoods or conifers, and sometimes found in urban settings like gardens and parks; summer and fall; in North America widely distributed east of the Rocky Mountains, but also reported from the Pacific Northwest; also found in Europe and Oceania.

2. Cap

   1.5–5 cm; nearly round in the button stage, expanding to convex and eventually planoconvex, sometimes with a low central bump; dark brown when fresh; fading to dull tan; sticky when fresh; bald; often a little wrinkled, especially over the center when young; with whitish partial veil remnants on the margin; margin sometimes becoming lined with maturity.

3. Gills

   Beginning to run down the stem with a decurrent tooth; close; whitish at first, maturing to pale brown; short-gills frequent. At first, the gills are covered by a white partial veil.

4. Stem

   4–8 cm long; 3–10 mm thick; more or less equal; bald or finely pruinose; whitish, becoming brownish from the base up; with a white, flaring ring that may collapse or disappear by maturity.

5. Flesh

   White to brownish; not changing when sliced.

6. Odor and Taste

   Odor not distinctive; taste slightly bitter.

7. Chemical Reactions

   KOH gray or negative on cap surface.

8. Spore Print

   Brown.

9. Microscopic Features

   Spores 10–15 x 5–7 µm; subellipsoid to subamygdaliform, often with a narrowed, "snout-like" end; smooth; brownish to brownish-yellow in KOH; orangish-brownish in Melzer's reagent. Basidia 2-sterigmate. Cheilocystidia 25–40 x 5–7.5 µm; narrowly lageniform or subcylindric; smooth; thin-walled; hyaline in KOH. Pleurocystidia 30–75 x 7.5–12.5 µm; lageniform; smooth; thin-walled; hyaline in KOH. Pileipellis hymeniform; brownish to brown in KOH. Clamp connections not found.

10. Similar Species

    Agrocybe praecox, which occurs in spring and early summer, often grows in woodchip mulch; it is typically smaller than Agrocybe erebia and usually has a yellowish buff cap that becomes even paler with age.

Cyclocybe erebia Taxonomy and Etymology

When Christiaan Hendrik Persoon described this mushroom in 1801 he named it Agaricus denigratus, which twenty years later the great Swedish mycologist Elias Magnus Fries changed to Agaricus erebius. Until 2014 it's accepted scientific name was Agrocybe erebius, which dated from 1939, when German-born mycologist Rolf Singer transferred it to the genus Agrocybe. Based on the results of recent DNA analysis, in 2014 Italian mycologist Alfredo Vizzini and American P. Brandon Matheny transferred it to the genus Cyclocybe, establishing the currently-accepted scientific name Cyclocybe erebia.

Synonyms of Cyclocybe erebia include Agaricus denigratus Pers., Agaricus erebius Fr., Agaricus leveillianus Dozy & Molk., Agaricus jecorinus Berk. & Broome, Armillaria denigrata (Pers.) P. Kumm., Pholiota erebia (Fr.) Gillet, Togaria erebia (Fr.) W.G. Sm., and Agrocybe erebia (Fr.) Singer.

'Fieldcap' is derived from Agro-, of fields, and -cybe, head or cap, and is, therefore, a direct translation of the generic name Agrocybe.

The specific epithet erebia simply means 'dark'.

Sources:

Photo 1 - Author: Heather Waterman (ripkord) (Creative Commons Attribution-Share Alike 3.0 Unported)

Photo 2 - Author: Sava Krstic (sava) (Creative Commons Attribution-Share Alike 3.0 Unported)