Four species are known in Europe. Fruitbody boletoid with partial veil, leaving a fibrillose ring. Cap fibrillose scaly. Stipe hollow or solid. Tubes decurrent (running down the stipe). There is strong molecular evidence that this genus must be integrated in Suillus; here for practical purposes, I would prefer to list it as a genus on it own. Note also that the genus Fuscoboletinus is also kept separately, although it also must be integrated in Suillus.
Boletinus asiaticus Singer
Cap up to 10 cm, at first hemispherical then expanding to convex or almost flat, fibrillose-scaly, crimson red to vinaceous red. Stipe cylindrical, hollow in the lower part, concolorous with the cap, below the tubes with fibrillose ring. Flesh whitish to yellowish, unchanging when exposed to air. Tubes short, decurrent, pale yellow to olivaceous yellow, unchanging when exposed to air. Pores large, angular, pale yellow to olivaceous yellow, unchanging when bruised. Smell not distinctive. Taste not distinctive. Spores 11–12 × 4.5–5 μm.
Habitat. Coniferous forests, mycorrhizal with larch (Larix).
Distribution. In Europe mostly within the northern parts of the natural range of larch. Until recently records were available only from Finland and European Russia (Perm Krai), but there are recent collections from France (see Robin 2012). It should be looked further in areas with native or planted larch as it may occur elsewhere.
I am not currently having images of Boletinus asiaticus, but there are some on the internet. Please, follow the links below (opening in new window).
Engel, H., Dermek, A., Klofac, W., Ludwig, E. & Brückner, T. 1996. Schmier – und Filzröhrlinge s. l. in Europa. Die Gattungen Boletellus, Boletinus, Phylloporus, Suillus, Xerocomus. Verlag Heinz Engel, Weidhausen b. Coburg.
Knudsen, H. & Vesterholt, J. [eds.]. 2008. Funga Nordica. Nordsvamp, Kopenhagen.
Robin, C. 2012. Boletinus asiaticus Singer [= Suillus asiaticus (Singer) Kretzer & T. D. Bruns] Première récolte française. – Bulletin de la Fédération Mycologique et Botanique Dauphiné-Savoie 207: 21–24.
Переведенцева, Л.Г. 1999. Биота и экология агарикоидных базидиомицетов Пермской области. Диссертация на соискание ученой степени “доктор биологических наук”. Москва. [Perevedenceva, L.G. 1999. Biota and ecology of the agaricoid basidiomycetes of Perm Oblast. Doctoral thesis.] (abstract in Russian available online)