Cyathus stercoreus, commonly known as the dung-loving bird's nest or the dung bird's nest, is a species of fungus in the genus Cyathus, family Nidulariaceae. Like other species in the Nidulariaceae, the fruiting bodies of C. stercoreus resemble tiny bird's nests filled with eggs. The fruiting bodies are referred to as splash cups, because they are developed to use the force of falling drops of water to dislodge and disperse their spores. The species has a worldwide distribution, and prefers growing on dung, or soil containing dung; the specific epithet is derived from the Latin word stercorarius, meaning "of dung". Description The fruiting bodies, or perida, are funnel- or barrel-shaped, 6–15 mm tall, 4–8 mm wide at the mouth, sometimes short-stalked, golden brown to blackish brown in age. The outside wall of the peridium, the ectoperidium, is covered with tufts of fungal hyphae that resembles shaggy, untidy hair. However, in older specimens this outer layer of hair (technically a tomentum) may be completely worn off. The internal wall of the cup, the endoperidium, is smooth and grey to bluish-black. The 'eggs' of the bird's nest – the peridioles – are blackish, 1–2 mm in diameter, and there are typically about 20 in the cup. Peridioles are often attached to the fruiting body by a funiculus, a structure of hyphae that is differentiated into three regions: the basal piece, which attaches it to the inner wall of the peridium, the middle piece, and an upper sheath, called the purse, connected to the lower surface of the peridiole. In the purse and middle piece is a coiled thread of interwoven hyphae called the funicular cord, attached at one end to the peridiole and at the other end to an entangled mass of hyphae called the hapteron. However, Brodie reports that sometimes C. stercoreus is found without a funiculus, which has led some authors to misidentify this species with the genus Nidula. The spores of C. stercoreus are roughly spherical and relatively large, with typical dimensions of 20–35 x 20–25 µm, although great variability in spore size has been noted. The spores are sessile (growing directly from the surface of the basidium, without attachment via a sterigmata), and are separated from the basidia after it collapses and gelatinizes. This is accompanied by the gelatinization of the inner walls of the peridiole. Ultrastructure Examination of fruiting bodies using scanning electron microscopy and transmission electron