Boletus luridus

Cap	Immature specimens, such as the one shown here, are downy and pale yellow. As the fruiting body matures, the cap, which expands to between 8 and 14 cm (exceptionally 20 cm) in diameter, becomes dull yellow-brown. The yellow cap flesh turns blue-black if it is cut or bruised.
Tubes and Pores	Beneath the cap, yellow spore tubes terminate in tiny circular pores that are at first yellow but eventually turn orange-red. When cut or bruised, the tubes and pores rapidly turn blue-black before fading to pale blue.
Stipe	1.5 to 4 cm in diameter and 5 to 10 cm tall, the swollen stem turns dark blue when cut and then fades back to a light blue colour, as seen here. The flesh near the base of the stem is deep yellow with red tinges. The surface of the stem is yellow, covered with a red mesh patterning everywhere except for the top of the stem, which remains yellow.
Spore print	Olive-brown.
Odour/taste	Not distinctive.
Habitat	Most commonly found under beech trees on calcareous soil, this species is also occasionally seen beneath oak trees and limes.
Season	July to late October.
Occurrence	Infrequent.
Similar species	Boletus satanus, a dangerously poisonous species, has a deep red and very swollen stem with a chalky-white cap. Boletus erythropus has a less swollen stem that is covered in tiny red dots.