Flesh bluing quickly; stem red below, yellow above; under hardwoods; cap yellow-brown with KOH; spores 9-12 x 3-3.5 µ. (1/7)

Boletus carminipes

Cap usually with yellow powder; flesh sometimes bluing slowly or not bluing; stem reddish over yellow base color, sometimes with yellow powder; under pine; chemical reactions not recorded; spores 6-9 x 2.5-4 µ. (2/7)

Buchwaldoboletus hemichrysus

Flesh bluing quickly; stem yellow above, dark red to brownish red below; under hardwoods or conifers; chemical reactions not recorded; spores 12-17 x 4-6 µ. (3/7)

Boletus luridellus

Flesh bluing slowly and weakly; stem yellowish to brownish yellow, often white at apex; under hardwoods; cap margin pale blue-green, center dark brown with ammonia; spores 8.5-11.5 x 3.5-5 µ. (4/7)

Boletus melleoluteus

Flesh staining reddish, then bluish "within five minutes"; stem yellow, staining reddish in age; under hardwoods or conifers; cap reddish brown with ammonia; spores 10-14 x 4.5-6 µ. (5/7)

Boletus ochraceoluteus

Flesh bluing quickly; stem yellow, sometimes with reddish tints near base; under hardwoods or conifers; blued flesh orange with KOH; spores 10-16 x 4-6 µ. (6/7)

Boletus pseudosulphureus

Flesh bluing, but sometimes slowly or weakly; stem yellow, without red shades; "on sawdust, or on stumps or the surrounding soil"; chemical reactions not recorded; spores 7-9 x 3-4 µ. (7/7)

Boletus sphaerocephalus

> Cap pale (whitish, light tan, buff, etc.) in all stages of development. (1/2)

° Blue staining typically weak and erratic (or absent); cap 4.5-15 cm; stem whitish, developing brownish streaks (rarely developing reddish tones near base); cap rusty orange with ammonia; found under hardwoods. (1/4)

Imleria pallida

° Blue staining typically pronounced, though not strong; cap 4-12 cm; stem pale to yellowish, becoming reddish; cap negative with ammonia; found under oak and hemlock. (2/4)

Caloboletus inedulis

° Blue staining typically weak and erratic (or absent); cap 5-25 cm; stem yellowish to whitish (rarely developing dull reddish tones); cap orange with ammonia; found under hemlock. (3/4)

Boletus huronensis

° Blue staining typically pronounced, though not strong; cap 6-13 cm; stem yellowish to whitish, with red areas, and with a narrow red zone at the apex; cap reaction to ammonia not recorded; found under oak. (4/4)

Boletus glabellus

> Cap more highly colored. (2/2)

° Easily recognized species: (1/2)

~ Growing on or near conifer stumps; blue staining typically weak and erratic or absent; stem with yellow basal mycelium; spores 6-10 x 3-4 µ. (1/5)

Boletus lignicola

~ Cap dark brown to olive brown, becoming cracked in age and revealing reddish flesh in the cracks; spores 9-13 x 3.5-4.5 µ . (2/5)

Xerocomellus chrysenteron

~ Cap chestnut brown to cinnamon brown, smooth; stem yellowish, adorned with tiny red fibers, dots, or spots; blue staining weak and erratic or absent. (3/5)

Boletus subglabripes

~ Cap chestnut brown to cinnamon brown, conspicuously corrugated and rugged. (4/5)

Boletus hortonii

~ Cap smoky buff to yellowish brown; stem whitish to yellowish or reddish, with a red zone near the apex; pore surface bruising blue, but then brown; flesh blue on exposure but soon fading to white. (5/5)

Boletus glabellus

° Not as any of the above species: (2/2)

~ Blue staining or bruising faint and/or erratic. (1/2)

* Cap surface turning green, blue or olive with a drop of ammonia--or with a flash of green before turning some other color. (1/2)

-- Flashing green with ammonia and then resolving to another color. (1/2)

Cap color dull brownish; cap surface orange with ammonia (after the green flash); stem yellow above, whitish below, occasionally with reddish tints. (1/2)

Boletus huronensis

Cap color dark olive to yellowish brown or brown, sometimes with reddish tints; cap surface reddish brown with ammonia (after the green flash); stem yellowish and whitish, sometimes staining brownish but never with reddish colorations. (2/2)

Xerocomus ferrugineus

-- Remaining greenish, bluish, or olive with ammonia; not merely flashing. (2/2)

Cap color reddish to yellowish brown, sometimes with olive shades; cap surface green to blue with ammonia; flesh white when fresh; stem brownish or reddish brown; under hardwoods or conifers; northern in distribution. (1/2)

Imleria badia

Cap color tawny brown to yellowish brown; cap surface blue to greenish blue with ammonia; flesh yellowish; stem yellow to tawny or brownish; under hardwoods; southern in distribution. (2/2)

Boletus hypoxanthus

* Cap surface turning some other color with a drop of ammonia, and not flashing green at first. (2/2)

Cap surface reddish brown with ammonia; cap color reddish to purplish brown; spores 7-10 µ long; under hardwoods or conifers; Texas. (1/3)

Boletus lewisii

Cap surface yellowish with ammonia; cap color variable--from yellowish brown to reddish brown or brownish; spores 10-13 µ long; under hardwoods; probably widely distributed east of the Rocky Mountains. (2/3)

Boletus rufomaculatus

Cap surface reddish brown with ammonia; cap color olive-brown to yellow-brown; spores 10-15 µ long; under hardwoods or conifers; widely distributed. (3/3)

Xerocomus subtomentosus

~ Blue staining or bruising consistent and fairly strong. (2/2)

* Cap surface bruising bluish or brownish. (1/2)

-- Pore surface intially yellowish, but soon yellow-brown. (1/2)

Boletus subgraveolens

-- Not as above. (2/2)

Cap surface yellowish with ammonia; flesh bluing when sliced, then slowly changing to to reddish brown; smell not distinctive; known only from Mississippi. (1/3)

Boletus mahoganicolor

Cap surface flashing green with ammonia; flesh bluing when sliced, but not changing to reddish brown; smell not distinctive; widely distributed east of the Rocky Mountains. (2/3)

Boletus pulverulentus

Cap surface yellow with ammonia; flesh bluing when sliced, but not changing to reddish brown; smell distinctively fragrant/spicy; widely distributed east of the Rocky Mountains. (2/3)

Boletus sensibilis

* Cap surface not bruising. (2/2)

-- Spores reaching lengths of 16-19 µ or more. (1/2)

Cap yellowish to brownish yellow, or streaked brownish over a yellow base color; stem not bruising when handled; spores 12-17 x 4-6 µ. (1/2)

Boletus luridellus

Cap reddish brown to tawny, fading to dull brown; stem bruising blue when handled; spores 13-19 x 5-8 µ. (2/2)

Boletus rubricitrinus

-- Not as above; spores typically shorter than 16 µ. (2/2)

Flesh whitish, turning yellow then bluish near the tubes on exposure; cap reddish brown to yellow brown; stem brown to reddish brown, without yellow shades; cap surface green to blue with ammonia; widely distributed ERM (east of the Rocky Mountains). (1/8)

Imleria badia

Flesh pale yellow, bluing on exposure; cap reddish brown becoming yellow brown; stem yellow above, carmine red below; cap surface ammonia reaction not recorded; northeastern in distribution. (2/8)

Boletus carminipes

Flesh pale yellow, bluing on exposure but sometimes slowly; cap brownish to pale brownish; stem yellow at apex, yellowish or whitish overall; cap surface flashing green, then resolving to orange with ammonia; northeastern in distribution. (3/8)

Boletus huronensis

Flesh yellow, bluing quickly on exposure but slowly resolving to reddish brown; cap mahogany brown; stem yellow above, orange-red to brownish red below; cap surface yellowish with ammonia; recorded from Mississippi. (4/8)

Boletus mahoganicolor

Flesh pale yellow to whitish, red under the cap skin, bluing on exposure (the species name refers to the red, white and blue flesh); cap olive becoming reddish or brownish red; stem with red and olive shades over a yellow base color; cap surface olive amber with ammonia; widely distributed ERM. (5/8)

Boletus patrioticus

Flesh bright yellow, bluing quickly on exposure; cap reddish brown fading to cinnamon or yellow-brown; stem yellow, with reddish tinges; cap surface flashing blue, then dull purple with ammonia; probably widely distributed ERM. (6/8)

Boletus pseudosensibilis

Flesh whitish to pale yellow, bluing on exposure; cap olive brown to grayish brown, fading in age; stem yellow at apex, red or yellow with red areas below; cap surface dark olive green with ammonia; northeastern in distribution. (7/8)

Boletus roseipes

Flesh pale yellow, slowly bluing on exposure (at least above the tubes) but sometimes weakly; cap color variable--typically rusty brown to brownish, with paler areas that predominate in age; stem yellow at apex, yellowish or reddish below; cap surface yellowish with ammonia; probably widely distributed ERM. (8/8)

Boletus rufomaculatus