Once known S.microhaema is unmistakeable and instantly recognisable, and could not be confused with any other lichen, except perhaps for Piccolia (formerly Strangospora) ochrophora, which has much larger, c. to 0.5mm diam., rusty-ochraceous, orange-pruinose, K+ purple (K- in S.microhaema), fragile apothecia, crumbling when prodded with a needle tip, and occurring on drier, base-rich bark. Biatoridium species have generally paler apothecia and a different layered structure to the ascus apex. Biatorella and Sarcosagium both have bacilliform ascospores and are terricolous. Microscopically S.microhaema has golden-reddish-orange hymenial tissues and its multispored asci, containing a frogspawn-like mass of simple, tiny, round ascospores, are similarly yellow-orange (-red) internally, as are the tips of the paraphyses. Prematurely released immature ascospores can also sometimes have orange contents.
S.microhaema was discovered new to Wales in 1994 in Cwm Llyfnant, v.c. 46, Cardiganshire (Chambers, 1994), since when it has been found at two more sites, a second site in Cardiganshire in the old walled garden at the Hafod estate and on an old Fraxinus excelsior in wood-pasture at Dol-y-cae at the foot of Cadair Idris in v.c. 48, Merionethshire. Being unobtrusive S.microhaema could well be overlooked in northwest Wales in suitable wet, old woodland and likely awaits discovery in v.c. 49 Caernarfonshire.