Midden Inkcap

Coprinus sterquilinus is one of the small handful of species left in Coprinus once the genus was dismantled and most of its members moved into Coprinopsis, Coprinellus and Parasola. What holds the remaining group together is a shared structure: a tall cylindrical cap clothed in coarse, upturned veil scales, free crowded gills that pass from white through pink to black, and a movable ring on the stipe.

The Midden Inkcap looks very much like a scaled-down Shaggy Inkcap, and inexperienced eyes often assume it simply is one. The differences are in size, proportion and habitat: it is a smaller, more delicate fungus, and it is firmly attached to manure and old dung heaps rather than roadside verges and disturbed grassland. Its English name comes directly from that habitat, a midden being a refuse or manure heap.

Microscopically it is unmistakable within the group because its spores are exceptionally large, among the biggest of any inkcap, a feature that has long been used to confirm collections. In the field it is best treated as the dung-heap shaggy inkcap, distinguished by substrate and stature.

Cap

2-6 cm tall and 1-3 cm wide, at first a narrow white cylinder or ellipsoid closely pressed to the stipe, later expanding to bell-shaped and finally splitting. The surface is white to cream, broken into soft fibrillose to slightly upturned scales, usually smoother and more ochre-tinged over the very apex. As the spores mature the lower margin darkens to grey then black, rolls upward and dissolves.

Gills

Free from the stipe and extremely crowded, very narrow, white when young, then flushing pink or pinkish-grey and finally turning inky black from the margin inward as they deliquesce.

Stipe

5-15 cm long, slender, white, smooth to slightly silky, hollow, and fragile. It carries a narrow, movable ring that in this species usually sits low down, often near the base, and is easily lost. The base is slightly swollen and frequently drawn out into a short tapering root that penetrates the substrate.

Flesh & spore print

Flesh thin, white, soft, without notable odour. The spore print is black. Under the microscope the smooth blackish spores are unusually large and broadly ellipsoid with a prominent germ pore, which separates the species decisively from its larger relative.

This is a dung and manure specialist, found on old horse dung, cattle manure heaps, rotted straw bedding, and the manure-rich ground around stables, byres and farmyards. It particularly favours heaps that have already stood for some weeks and have begun to break down and settle, rather than fresh droppings.

It is widespread across Europe and North America and has been recorded on other continents wherever livestock are kept, though it is nowhere abundant and is often overlooked because the fruit bodies collapse within hours of opening. Fruiting runs from spring through autumn, with the heaviest flushes after warm, wet spells.

The Midden Inkcap is a saprotroph living on herbivore dung and manure-enriched plant fibre. It arrives in the succession after the fast-growing moulds and dung-loving ascomycetes have taken the simplest sugars, and works instead on the tougher cellulose left in the digested plant material, contributing to the final breakdown of the heap.

Deliquescence is central to its life cycle. The liquefying cap concentrates spore release into a short window and spreads spores in a fluid that is easily splashed by rain or carried off by the many flies attracted to manure. Some spores are taken in with vegetation by grazing animals, pass through the gut intact, and germinate in freshly deposited dung, so the fungus effectively hitchhikes between heaps inside the animals that create them.

Coprinus comatus, the Shaggy Inkcap, is by far the closest match in shape but is much larger, commonly 10-20 cm tall, with coarser, more shaggily recurved scales and a stouter stipe, and it grows in grass, on verges and on disturbed ground rather than on dung heaps. Coprinopsis nivea shares the manure habitat but is coated in a chalky white powder rather than fibrous scales and has no ring.

Coprinopsis cinerea also fruits on manure and rotted straw, but its cap is grey rather than white, its veil is woolly and flaky rather than forming discrete scales, and it lacks a movable ring. Coprinopsis lagopus is greyer still, with a hare's-foot texture of loose hairs, and prefers woodchip and leaf litter.