Bleeding Fairy Helmet
Mycena haematopus
Also called bleeding mycena, burgundydrop bonnet, bleeding bonnet
A delicate reddish-brown bonnet that exudes dark blood-red latex from its hollow stipe when broken, growing in tight clusters on rotting hardwood.
Overview
The Bleeding Fairy Helmet is the best known of the "bleeding" bonnets, a small group within the huge genus Mycena whose fruiting bodies contain a coloured latex held in the hollow stipe. Snap a fresh stipe and a dark burgundy droplet wells out within seconds — a reaction so distinctive that it settles the identification of an otherwise nondescript little brown mushroom on the spot.
Mycena is one of the largest genera of gilled fungi, with several hundred described species, most of them small, conical or bell-shaped, white-spored and thin-fleshed. M. haematopus is placed in section Lactipedes, the latex-bearing bonnets, and is among the most frequently photographed woodland fungi because of the drama of its coloured sap against pale gills.
It is a wood-inhabiting species of the northern temperate zone, fruiting in tight tufts on well-rotted hardwood. The specific epithet haematopus means "blood-foot", referring to the reddish stipe and the latex it carries.
How to identify it
Cap
The cap is 1–4 cm across, at first narrowly egg-shaped or conical, then expanding to a broad bell with a low umbo. The colour is a distinctive vinaceous or wine-brown, often reddish-brown at the centre and paler pinkish-grey towards the rim, fading as the cap dries. The surface is dry, faintly powdery-bloomed when young, and radially striate or grooved from the margin inwards. A key detail is the margin itself: it is minutely scalloped and hung with tiny pale teeth or fringing veil remnants that are visible with a hand lens and often even to the naked eye.
Gills
The gills are adnate, sometimes with a very short decurrent tooth, moderately close, and white to pale greyish-pink. With age or handling they develop reddish-brown spots and stains from the latex, which is one of the surest field confirmations.
Stipe
The stipe is 3–10 cm long and only 1–3 mm thick, hollow, equal, and coloured the same reddish or wine-brown as the cap, usually paler at the apex. It is finely powdery above and clothed at the base with stiff whitish hairs that bind the substrate. Snapping or squeezing the stipe releases a dark blood-red to purplish-red latex.
Flesh and spore print
The flesh is very thin and watery, reddish in the stipe, with no distinctive odour. The spore print is white.
Where and when it grows
This species fruits on decaying hardwood: logs, stumps, large fallen branches and occasionally buried wood, most often at a moderately advanced stage of decay when the bark is loosening. Beech, oak, maple, birch and poplar are all frequent hosts. It grows in tight caespitose clusters of a handful to twenty or more fruiting bodies joined at the base, rather than scattered singly.
It is widespread and common across temperate North America, Europe and northern Asia, in deciduous and mixed woodland. Fruiting runs from early summer into late autumn, peaking during cool, damp spells in late summer and early autumn.
Ecological role
The Bleeding Fairy Helmet is a saprotroph that decays hardwood, contributing to the white-rot breakdown of fallen trunks and branches. It typically arrives after the wood has been softened by earlier colonists, working through the residual cellulose and lignin of the outer sapwood.
The coloured latex is thought to function as a chemical defence against invertebrate grazing, a role played by latex in several unrelated fungal lineages, notably Lactarius. Fruiting bodies are short-lived, often collapsing within a few days, and the tight clustering habit reflects a mycelium fruiting from a small number of favourable points where it reaches the log surface.
Similar species
Mycena sanguinolenta also bleeds dark red but is markedly smaller and more slender, grows singly or scattered in leaf litter, needles and moss rather than clustered on logs, and has gill edges marked with a fine dark reddish-brown line. Mycena crocata releases a bright orange latex instead of wine-red, and stains everything it touches saffron. Mycena galericulata, a similar-sized bell on the same logs, is grey-brown, has pink-tinged gills with cross-veins, a tough cartilaginous stipe and releases no latex at all.
Mycena inclinata shares the clustered habit on hardwood but has a straw-yellow to rusty-brown stipe base, a conspicuously toothed cap margin and no latex. Mycena pura is pinkish-lilac, grows on the ground in litter, and has a stouter build with no coloured sap.