Rubroboletus demonensis

What You Should Know

Rubroboletus demonensis is an intermediate species between Rubroboletus legaliae and Rubroboletus rubrosanguineus. It can be defined as R. rubrosanguineus with habitat in thermophilic broad-leaved woods. It is distinguished by the color of the cap which is soon extensively purple-red, with a tendency to darken when bruised, the red pores, the red stem with yellow apex, covered by a red grid with evident large meshes, the flesh turning blue in the entire section.

Rubroboletus demonensis Mushroom Identification

1. Cap

   60‒150 mm broad, initially hemispherical, then convex, pulvinate, at the end almost applanate in mature basidiomes. Margin ± regular in young, soon uneven, ± undulate-lobate, sometimes distinctly lobate in mature specimens. The color at the very beginning whitish, pale grey, pale ochre, soon, starting from the margin, dirty pale pink-lilac, then strongly variable from light grey, to pink-lilac, to purple-red depending on environmental conditions; with wet weather or in shady woods, the pileus shows particularly bright colors, tending to purple-blood red, quite uniformly distributed on the pileus surface. In some occurrences, the red color seems not to develop completely both in pores and stipe, and in meantime also the pileus color stabilizes on pink-lilac uniform color, that becomes blood red when bruised. Conversely, in dry weather or areas exposed to the sun, pileus color is much more variable, with flesh pink colors sometimes fading to brownish-gray or paler tone tending to cream-whitish. However, in most of the basidiomes observed, large intensely reddish areas or wide blood-red spots persist, even more, intense following scrubbing, touching, or other manipulation. Surface typically tomentose and dry at the beginning, sometimes smooth and viscous in wet weather; the cuticle is not detachable from the underlying flesh. Often, in mature large basidiomes, the pileus appears pleasantly bright shining red, darker when bruised. Looking closely at the pileus surface, also with the aid of a lens, minute, in relief, concolorous scales can be noticed.

2. Stipe

   80‒120 × 40‒80 mm, bulky, robust and wide, cylindrical, often gradually enlarged or clavate towards the base, sometimes also obese, not root. Surface in rare case yellow-orange at the very beginning, with purplish base, then, passing through intermediate orange-red tones, at the end bright red, blood red, purple-red, often darker at the base, often with an evident deep yellow, or orange-yellow band (5–15 mm wide) in the upper part. In some xanthoid aspects stipe does not develop red tones in the upper half, remaining yellow or orange-yellow, but the stipe base is anyway red, purple-red blood red. The extreme base of the stipe is covered with a whitish grainy, furfuraceous over layer, particularly evident in basidiomes collected on moist grounds.

3. Tubes

   5‒12 (‒20) mm, having average length, free at the stipe, from deep yellow to olive green, discoloring blue when cut.

4. Pores

   Small, round, usually from the beginning purple-red, dark red, dull blue when touched, in aged basidiomes orange-yellow towards the margin of the pileus. In some collections, young specimens have yellow pores, that with age develop only an orange, red-orange color, reminiscent that one of typical R. legaliae.

5. Flesh

   Firm, yellow, deep yellow, lemon yellow, particularly intensive in both stipe and pileus wounds; when exposed, quickly turning sky-blue, blue, deep blue, due to discoloring not particularly intensive, sometimes weak, then fading to a pale gray-cream color. In some cases, in the exposed pileus or mostly in the lower part of the stipe some beetroot shades may appear. Sub-hymenophoral layer is concolorous.

6. Taste

   Sweetish, slightly acidic.

7. Smell

   Weak, fungal, and pleasant.

8. Spore Print

   Tobacco-brown.

9. Chemical Reactions

   Amyloid reaction in the flesh at the stipe base, according to Imler’s procedure (Imler 1950): the tissues at the stipe base are not amyloid in all the collections if examined microscopically.

10. Microscopic Features

    Basidia mostly 4-spored, hyaline, (23.8‒) 31.3‒47.7 (‒62.6) × (4.2‒) 7.7‒12.7 (‒13) µm (34/2/2). Facial cystidia fusiform, versiform, sometimes lageniform, hyaline, (15.5‒) 29.5‒44.7 (‒50.7) × (4.2‒) 5.3‒7.7 (‒9.5) (64/2/2). Marginal cystidia similar to facial cystidia but smaller, mostly versiform than fusiform or lageniform, hyaline (15.8‒) 20‒29 (37.2) × (3.5‒) 4.3‒6.3 (‒7.9) (46/2/2). Pileipellis an entangled trichodermium, tending to a cutis, often gelatinized in mature individuals, consisting of thin, cylindrical elements, collapsing gradually during the development of the basidiomes. Terminal elements (33.3‒) 32.9‒42.9 (‒44.3) × (5‒) 5.2‒5.9 (‒6.9) µm (138/5/5), Q = (6.6‒) 6.4‒8.1, Qm = 7.3, with a rounded or tapered tip, sometimes clavate, rarely capitulate or pear-shaped, with pale yellow vacuolar pigment and incrusted pigmented here and there, mostly in the deeper and closer to hypoderma hyphae. Hymenophoral trama boletoid in the sense of Singer (1965, 1967). Clamp connections absent.

11. Habitat

    In acid and silicic soils, thermophilic, in summer. It grows in groups of small basidiomes in warm deciduous forests, in mountains, or some cases in mixed deciduous and coniferous woods (Pinus nigra and Taxus baccata), never with pure conifers. It prefers mesic forests of deciduous oaks (Quercus pubescens sensu lato, Q. cerris, Q. congesta and Q. virgiliana), rarely with holm (Q. ilex). It is common in chestnut woods (Castanea sativa), pure or mixed, and at higher elevations with beech (Fagus sylvatica). It is usually collected in June after the late spring rains and, not liking the summer drought, it disappears during the hottest period of July and August, then appears again in September. During the warmer autumns, it can be observed until the first half of October.

12. Distribution

    It was found in a rather delimited area of South Italy and Sicily, where it inhabits the mesomediterranean and supramediterranean zone of the mountain strip, characterized by a humid Mediterranean climate, with large rainfalls and Mediterranean humid forest well represented by deciduous forests of oak (Q. pubescens s.l.) and chestnut (C. sativa).

Rubroboletus demonensis Look-Alikes

1. Rubroboletus legaliae

   Can get confused in the first stages of growth when the cuticle is whitish, subsequently it retains these colors of the hat even if at times localized and it is difficult for the cuticle to become entirely red. The stem has a red color up to the apex, without a yellow apical zone and the reticulum has a tight and dense mesh.

2. Rubroboletus rubrosanguineus

   Has similar colors to the cap but is smaller and grows mainly in coniferous mountain forests. The stem has a network with particularly dense and elongated meshes that give a uniform blood red color to the whole stem, without a yellow apical area.

3. Boletus rhodopurpureus

   Has a strong dark blue toning when cut or even when manipulated on all surfaces, in such a way as to become entirely black with intense manipulation.

4. Rubroboletus rhodoxanthus

   Has no color change in the flesh of the stem and the pileus color does not reach an intense red color.

Rubroboletus demonensis Etymology

The specific epithet of the name of the taxon comes from the Latin word “demonensis” and refers to the ancient name “Valdemone”, which was one of the three valleys (“valli”) or real domains (“reali dominii”) in which the region Sicily was subdivided from the Muslim domination to the Bourbon period; the “Valdemone”, concerning the “Val di Noto” and the “Val di Mazzara”, constitutes the north-eastern part of the Sicily, an area that closely corresponds to the actual habitat of R. demonensis.

Furthermore, the epithet “demonensis” well reminds the peculiar features of the species, i.e. the flaming red color of the cap and the pores, features shared with other close “devilish” species, belonging to the same genus (Rubroboletus satanas).