Neoboletus luridiformis
Description
Neoboletus luridiformis is a yellow stem well-coated mushroom with orange-brown powder/spots, blues when bruised. Blue-bruising yellow baby pores soon age to orange/red. Yellow to greenish flesh quickly blues.
It is found in Northern Europe and North America and is commonly known as the scarletina bolete, for its red pores (yellow when young).
Whilst edible when cooked properly, it can cause gastric upset if raw. Where the two species coincide it can be confused with the poisonous Rubroboletus satanas, which has a paler cap.
The European species are formerly known as Boletus discolor, and Boletus luridiformis, Boletus erythropus, and Boletus queletii have been merged into a single species that is now called Neoboletus.
Boletes of Eastern North America follows this by merging the American “discolor” into “luridiformis” (using Neoboletus as the genus) and then continuing to use the European name until a replacement is settled. The bottom line is this: it is a beautiful mushroom with massive flexibility in how it appears.
In 1796, Christian Hendrik Persoon named Boletus erythropus, referencing its "red foot." This name was widely used for a mushroom with red pores and a red stalk, though it was later found Persoon’s original Boletus erythropus had orange pores and likely referred to Suillellus queletii, making this usage invalid.
In 1844, Friedrich Rostkovius properly described the red-pored mushroom as Boletus luridiformis, the valid basis for its current name. Genetic studies in 2013 showed B. luridiformis belonged in a new genus, Neoboletus, established in 2014. The name reflects its difference from the Boletus core group and similarity to Suillellus luridus.
Common names: Red Foot Bolete, Dotted Stemmed Bolete, Dotted Stem Bolete, Slender Red-Pored Bolete.
Mushroom Identification
Cap
The cap color of this often massive bolete is very variable. It can be dark chocolate brown, pale brown, or even, as in this fine specimen, coppery bronze. The cap flesh is yellow, rapidly bluing when cut or bruised.
Caps of Neoboletus luridiformis are initially downy and convex, becoming flatter, smooth, and shiny as the fruitbody matures. The diameter at maturity varies between 8 and 20 cm.
Tubes and Pores
Orange at first, the round, crowded pores soon become bright red and then rusty brown with age.
The spore tubes are lemon yellow, but they very quickly turn blue-green when cut or bruised.
Stem
Apart from a pale area near the apex, a pattern of tiny red dots covers most of the stem of Neoboletus luridiformis. (A hand lens may be necessary to distinguish the separate dots on some specimens.)
Typically 2 to 4cm in diameter and more or less parallel-sided, stems of the Scarletina Bolete range between 7 and 15cm tall and have yellow flesh that instantly turns blue-green when cut or bruised.
Spores
Sub-fusiform (broadly spindle-shaped) to broadly ellipsoidal, 12-16 x 4.5-6µm.
Spore Print
Olive-brown.
Look-Alikes
-
Similar but has a red net pattern on its stem.
-
Has a chalky white cap and a bulbous stem covered in a bright red net pattern on a yellow background; it is poisonous.
-
Has a reticulate stipe, and is larger.
-
Has a reddish cap.
-
Prefers neutral soil.
Synonyms
Boletus erythropus Persoon (1795)
Suillus erythropus (Persoon) Poiret (1806)
Boletus luridus var. ß erythropus (Persoon) Fries (1821)
Boletus luridus subsp.* erythropus(Persoon) Persoon (1825)
Boletus miniatoporus Secretan (1833)
Tubiporus luridus subsp.* erythropus (Persoon) P. Karsten (1882)
Dictyopus erythropus (Persoon) Quélet (1886)
Tubiporus erythropus (Persoon) Ricken (1918)
Photo sources:
Photo 1 - Author: George Chernilevsky (Public Domain)
Photo 2 - Author: George Chernilevsky (Public Domain)
Photo 3 - Author: mangoblatt (Public Domain)
Photo 4 - Author: agujaceratops (CC BY-SA 4.0)
Photo 5 - Author: roberto-rizzi (Public Domain)