Cortinarius semisanguineus (Fr.) Gillet - Surprise Webcap

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

Cortinarius semisanguineus - Surprise Webcap

The pale colour of both cap and stem lead you to expect the gills to be pallid. Not so! The gills are blood red - hence the rather fanciful common name given recently to this species. (The specific epithet semisanguineus means half blood-red; a related species, Cortinarius sanguineus, has blood-red cap and gills and is known as the Bloodred Webcap).

The Surprise Webcap is found mainly in coniferous forests, but occasionally it also occurs in deciduous woodland under birches.

Wool dyed using Cortinarius semisanguineus

Here is another surprise: this webcap's gills can be used to produce a beautiful brown-orange dye. In Nordic countries this abundant mushroom was traditionally used to produce coloured wool like the sample of dyed yarn shown above. (Picture courtesy J Padatsu; Finland.)


An occasional find in conifer forests throughout Britain, the Surprise Webcap is locally common particularly in spruce plantations where the trees are fairly mature. (Most mycorrhizal fungi will not fruit until their tree partners are well established, and some require ancient trees.) This webcap also occurs with birch trees in mixed woodland.

The Surprise Webcap occurs throughout most of northern and central mainland Europe and is a particularly common sight in the conifer forests of Scandinavia. Cortinarius semisanguineus occurs also in parts of North America.

Taxonomic history

This webcap was described in 1821 by the great Swedish mycologist Elias Magnus Fries, who gave it the name Agaricus cinnamomeus a semisanguineus and so established its basionym - the base name of its specific epithet. (In the early days of fungal taxonomy most gilled mushrooms were initially placed in a gigantic Agaricus genus; most of its contents have since been redistributed to other newer genera.) It was the French mycologist Claude-Casimir Gillet (1806 - 1896) who transferred this species to its current genus, thereby renaming it Cortinarius semisanguineus.

Synonyms of Cortinarius semisanguineus include Agaricus cinnamomeus a semisanguineus Fr., Cortinarius cinnamomeus ß semisanguineus (Fr.) Sacc., and Dermocybe semisanguinea (Fr.) M.M. Moser.

Cortinarius semisanguineus - Surprise Webcap, New Forest, England


The generic name Cortinarius is a reference to the partial veil or cortina (meaning a curtain) that covers the gills when caps are immature. In the genus Cortinarius most species produce partial veils in the form of a fine web of radial fibres connecting the stem to the rim of the cap rather than a solid membrane. The blood-red colour of the gills contrasting with the much paler colour of the cap is the basis of the specific epithet semisanguineus, which comes from Latin and simply means 'half blood red'.

Cortinarius semisanguineus - Surprise Webcap, New Forest, southern England


This mushroom is regarded as 'suspect' and may contain dangerous toxins; it should not be gathered for eating. Some reddish Cortinarius species with which the Bloodred Webcap could be confused contain the toxin orellanine, which if eaten destroys human kidneys and liver.

Identification guide

A pale cap of Cortinarius semisanguineus


Yellow or pale-to-mid olive-brown; convex, flattening with a distinct umbo; surface dry with fine fibrils or tiny scales; 3 to 6cm across. The cap surface turns instantly dark purple in reaction to a spot of KOH.

The pale-capped example shown on the left was seen in a Swedish spruce forest.

Cortinarius semisanguineus, a darke cap

The more olive-brown-capped specimen shown here was photographed in the New Forest, southern England

Blood-red gills of Cortinarius semisanguineus


The adnate gills are close, and both the gill faces and the gill edges are initially blood red.

Mature gills of Cortinarius semisanguineus in cross section

As the spores mature the gill faces turn brownish red while the gill edges become reddish brown.


Pale olive-yellow surface covered with light brown fibrils; cylindrical, often curved; 4 to 9cm long, 0.5 to 1.2cm diameter. The stem flesh is light ochre.

Cortinarius semisanguineus spores


Ellipsoidal, with a rough surface, 6-8 x 4-5µm; inamyloid.

Show larger image

Spore print

Rusty brown.


Odour and taste slight, when cut or crushed, of radish.

Habitat & Ecological role

Ectomycorrhizal, in coniferous woodland; sometimes also under birches; singly or in scattered groups, very often in moss.


August to October in Britain and Ireland.

Similar species

Cortinarius sanguineus, the Bloodred Webcap, has a blood-red cap as well as blood-red gills and stem.

Reference Sources

Fascinated by Fungi, Pat O'Reilly 2016.

Funga Nordica, Henning Knudsen and Jan Vesterholt, 2008.

Fungi of Switzerland Agarics, part 3: Cortinariaceae, Breitenbach, J., Kränzlin, F.

British Mycological Society, English Names for Fungi

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 and (for basidiomycetes) on Kew's Checklist of the British & Irish Basidiomycota.

Cortinarius semisanguineus - Surprise Webcap, New Forest, Hampshire, southern England


This page includes pictures kindly contributed by David Kelly.

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