Synonyms: Buellia italica A. Massal.; Buellia italica var. insularis Bagl.; Buellia italica var. lactea (A. Massal.) A. Massal.; Buellia italica var. recobarina (A. Massal.) Körb.; Buellia lactea (A. Massal.) Körb.; Buellia lactea var. olivaceofusca Anzi; Buellia liguriensis B. de Lesd.; Buellia olivaceofusca (Anzi) Zahlbr.; Buellia spuria var. recobarina (A. Massal.) Jatta; Catolechia lactea A. Massal.; Catolechia recobarina A. Massal.
Distribution: N - VG (Scheidegger & al. 2001), Ven (Lazzarin 2000b), TAA, Lomb, Piem (Isocrono & al. 2004), VA (Matteucci & al. 2015c), Emil (Fariselli & al. 2020), Lig (Watson 2014). C - Tosc, Abr (Gheza & al. 2021), Sar (Scheidegger 1993, Rizzi & al. 2011). S - Camp (Ricciardi & al. 2000), Pugl, Si (Nimis & al. 1996b).
Description: Thallus crustose, episubstratic, continuous to usually areolate, up to 1 mm thick, white to whitish grey, epruinose, phenocorticate, delimited by a conspicuous black prothallus which is sometimes visible as a black hypothallus between the areoles. Medulla white, I+ blue. Apothecia lecideine (0.2-)0.4-1(-1.5) mm across, immersed, rarely sessile, often irregular in outline, with a flat to slightly convex, black disc (often grey-pruinose by necrotic remains of thallus) and a thin, usually persistent proper margin. Proper exciple poorly differentiated, aethalea-type, with narrow inner hyphae, prosoplectenchymatous, transient with the deep reddish brown hypothecium, outer hyphae parallel, moderately swollen and strongly carbonized with brown and aeruginose pigments; epithecium greenish brown to olive, N+ pale violet-red; hymenium colourless, not inspersed with oil droplets, 70-90 µm high; paraphyses simple to sparingly branched, apically swollen, with a brown pigment cap; hypothecium dark brown. Asci 8-spored, clavate to cylindrical-clavate, the apical dome K/I+ dark blue with a pale, conical-pointed apical cushion (axial mass), the wall I-, but the thin outer gel I+ blue, Bacidia-type. Ascospores 1-septate, brown, oblong to ellipsoid, usually not constricted at septum, with obtuse ends, (9-)11-15(-17) x 5-7(-8) µm, Buellia-type, the wall thin throughout, smooth to microrugulate. Pycnidia rare, urceolate to globose, unilocular. Conidia bacilliform, 4.5-6 x 0.5-1.5 µm. Photobiont chlorococcoid. Spot tests: thallus K+ yellow-orange, C-, KC-, P- or P+ yellow, UV-; medulla usually K+ yellow turning red. Chemistry: atranorin, stictic or norstictic acid, and traces of different accessory substances.
Note: a mild-temperate to subtropical, chemically variable species growing on different types of siliceous rocks, often found also on walls. For a recent description see Giralt & van den Boom (2011).