Pseudoboletus parasiticus - Parasitic Bolete

Taxonomy

Phylum: Basidiomycota

Class: Agaricomycetes

Pseudoboletus parasiticus (synonym Xerocomus parasiticus) is unlikely to be confused with any other species, because it occurs only with the Common Earthball, Scleroderma citrinum. It is a rare bolete, and most of the earthballs you come across are not accompanied by this dull-looking fungus. At one time thought to be parasitic on the earthballs, these boletes are now thought to do little or no damage to their 'partners' - but just look at the shrivelled form of the earthball in this picture!

Identification Guide

Cap	Young caps are hemispherical and downy, becoming smooth and expanding as the fruiting bodies mature. When fully expanded, the caps of Xerocomus parasiticus range from 2 to 6cm in diameter. The cap surface often becomes cracked in dry weather, revealing the thick pallid flesh beneath the cuticle.
Tubes and Pores	Large tubes terminate in angular olive pores that are at first yellow but darken through olive to olive-brown as the fruiting body matures. When cut or bruised, neither the tubes nor the pores change colour appreciably, and there is no hint of bluing.
Stem	Because it emerges from beneath a Common Earthball, the stipe of the Parasitic Bolete is invariably curved. There is no stem ring. Olive or sienna, the stem tapers in towards the base and its pale lemon flesh does not change colour upon exposure to air. Between 1 to 2cm in diameter at the mid point, the stem is typically 3 to 6cm long.
Spore print	The spores are olive-brown.
Odour/taste	Not distinctive.
Habitat	Found only as a parasite of the Common Earthball, Scleroderma citrinum. This species is more likely to occur in regions where the soil is calcareous.
Season	August to October.
Occurrence	Rare.
Similar species	Boletus Chrysenteron has a reddish stem, usually untapered, and its cap cracks to reveal red flesh immediately below the skin.