Bleeding Bonnet

Mycena sanguinolenta is among the smallest of the bleeding bonnets, a delicate litter species whose entire fruit body would fit comfortably under a fingernail. Despite its size it is one of the easier Mycena to name, because two characters coincide: a dark red-brown latex that beads from any break in the wiry stipe, and gill edges lined with the same dark colour, visible with a hand lens as a fine dark thread running along each gill.

The species belongs to Mycena section Lactipedes, the small group of bonnets that produce coloured juice. Unlike its larger cousins that colonise logs, M. sanguinolenta is a creature of the ground layer, threading its mycelium through moss cushions, conifer needles and fragmentary leaf debris.

It is one of the most frequently encountered small fungi in northern woodlands, often appearing in scattered troops of dozens of fruit bodies across a single mossy bank, yet routinely overlooked because of its size.

Cap

The cap is only 3–10 mm across, conical to bell-shaped, sometimes flattening slightly with age but rarely fully expanding. It is translucent-striate when damp, so the gills show through as radiating lines, and coloured reddish-brown to purplish-brown, usually darkest at the centre and fading to pinkish-buff at the thin margin.

Gills

Gills are adnate or narrowly attached, fairly widely spaced, and pale pinkish-white to pale greyish. The diagnostic feature is the gill edge: a distinct dark red-brown to blackish-red marginal line runs along every gill, best seen with a hand lens against the light.

Stipe

The stipe is 2–6 cm tall and hair-thin — often under 1 mm — hollow, smooth, and coloured reddish-brown, darker below and paler near the apex. The very base carries a few sparse pale fibrils. Snapping the stipe releases small beads of dark blood-red to purplish-red juice, sparse but reliable in fresh material.

Flesh & spore print

The flesh is almost non-existent, watery and reddish. There is no distinctive smell. The spore print is white, from smooth amyloid ellipsoid spores; the dark gill edge results from pigmented cheilocystidia.

This bonnet grows on the woodland floor among mosses, fallen conifer needles, matted leaf litter and small buried twigs. It shows no strong tree preference, appearing under spruce, pine, birch, oak and beech alike, and also colonises mossy banks, heathland margins and the mossy skirts of old stumps.

Fruiting runs from mid-summer through to the first hard frosts of late autumn, peaking in the damp weeks of September and October. It is common and widespread throughout the temperate and boreal Northern Hemisphere, including much of Europe, northern Asia and North America, and is generally more abundant in cool, high-rainfall regions.

Mycena sanguinolenta is a saprotroph of fine ground litter, decomposing needles, moss stems, leaf fragments and slender woody debris. Its extremely fine mycelium permeates the humus and moss layer, where it plays a part in the early and middle stages of litter breakdown alongside other small bonnets and Marasmius species.

The fruit bodies are short-lived, often collapsing within a few days, but the mycelium can flush repeatedly through a wet autumn. Because the species colonises moss carpets so readily, it is frequently found in the same square metre as bryophyte-associated fungi, and its troops can serve as an easy visual marker of a consistently damp, undisturbed litter layer.

Mycena haematopus bleeds a similar dark red juice but is several times larger, has a scalloped or toothed cap margin, and grows in tight clusters on rotting hardwood logs rather than singly in litter; its gill edges lack the sharp dark marginal line. Mycena crocata exudes saffron-orange rather than blood-red latex and is a much taller, beech-litter species.

Mycena galopus is superficially similar in size and litter habitat but releases white, milky juice and has a greyer cap without a coloured gill edge. Among non-bleeding species, Mycena filopes and other small grey bonnets can be excluded quickly: neither shows the dark red gill margin, and neither produces coloured juice when the stipe is snapped.