Cyclocybe erebia (Fr.) Singer - Dark Fieldcap

Phylum: Basidiomycota - Class: Agaricomycetes - Order: Agaricales - Family: Strophariaceae

Distribution - Taxonomic History - Etymology - Identification - Culinary Notes - Reference Sources

An occasional find but then often gregarious, the Dark Fieldcap, Cyclocybe erebia, is a woodland fungus; its cap colour is very variable, sometimes with a centre so dark that it appears to be almost jet black. (The rings are not yet evident because the partial veils are still intact in the young and untypically lightish brown specimens shown here.)

Many of the fieldcaps can have darkish caps when young, but Agrocybe erebia is the only one that remains mid to dark brown through to maturity rather than fading to buff.

Distribution

An uncommon find in most parts of Britain and Ireland, Cyclocybe erebia occurs also throughout mainland Europe and in North America.

Taxonomic history

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 m2014 its 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.

Etymology

Not all fieldcap fungi occur in open fields, and the Dark Fieldcap is definitely a mushroom of field margins, hedgerows, woodlands and other shady places near trees. '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'.

Identification guide

	Cap 4 to 7cm across, hemispherical becoming broadly umbonate; the mid to dark brown cap surface usually pales somewhat towards the margin but does not fade, as other fieldcaps do, at maturity.
	Gills Adnate or very slightly decurrent; initially pale brown, turning dark brown as the spores mature. Stem 5 to 10cm long and 0.7 to 1.2cm diameter; cylindrical; whitish streaked with brown, darker towards base; retaining a persistent, pendulous pale brown ring with radial striations.
	Spores Ellipsoidal, smooth, 9.5-13 x 5.5-7.1µm, with a shallow snout-like protrusion. Show larger image Spores of Cyclocybe erebia, Dark Fieldcap  X  Spore print Dark brown.
	Basidia Usually with two spores per basidium.
Odour/taste	Not distinctive.
Habitat & Ecological role	In tufts or small groups, rarely solitary, saprobic on the litter of hardwood and softwood forest floors, hedgerows and sometimes under trees in parkland; occasionally on well-rotted woodchip mulch.
Season	June to October in Britain and Ireland.
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.

Culinary Notes

Agrocybe erebia is easily confused with any number of seriously poisonous brownish mushrooms - for example Hebeloma mesophaeum - and so is best considered inedible and therefore avoided when gathering mushrooms to eat.

Reference Sources

Fascinated by Fungi, 2nd Edition, Pat O'Reilly 2016, reprinted by Coch-y-bonddu Books in 2022.

BMS List of English Names for Fungi

Marcel Bon, 1980: Revision du Genre Agrocybe Fayod. Bulletin trimestriel de la Fédération Mycologique Dauphiné-Savoie, 76: 32-36. Bulletin de la Fédération trimestriel Mycologique Dauphiné-Savoie, 76: 32-36.

Funga Nordica: 2nd edition 2012. Edited by Knudsen, H. & Vesterholt, J. ISBN 9788798396130

Dictionary of the Fungi; Paul M. Kirk, Paul F. Cannon, David W. Minter and J. A. Stalpers; CABI, 2008

Taxonomic history and synonym information on these pages is drawn from many sources but in particular from the British Mycological Society's GB Checklist of Fungi.

Acknowledgements

This page includes pictures kindly contributed by David Kelly.

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