**Taxonomy:**
– Named as Boletus castaneus badius in 1818 by Elias Magnus Fries
– Reclassified in the genus Xerocomus by Edouard-Jean Gilbert in 1931
– Stickiness of wet cap distinguishes it from other Xerocomus species
– Placed in its own genus by Alfredo Vizzini in 2014
– Common and scientific names refer to the bay cap color
**Description:**
– Chestnut to dark brown cap, spherical when young
– Cap surface velvety and sticky when wet or old
– Pores initially cream to pale yellow, turning greenish yellow with age
– Flesh whitish or yellowish, staining pale blue when injured
– Stipe 4–9cm long, similar color to cap but paler, with fine ridges and mycelium at the base
**Similar Species:**
– Boletus projectellus is more robust with a reticulated stipe
– Austroboletus gracilis lacks blue bruising reaction and has white pore surface
– Boletus subtomentosus has narrower stipes and wider pores that do not stain blue
– In western North America, replaced by Boletus zelleri
– Boletus projectellus has the largest spores in the Boletaceae, up to about 30µm in diameter
**Conservation Status:**
– Least Concern according to IUCN 3.1
– First described by Elias Fries in 1818
– Reclassified as Xerocomus badius in 1931
– Bay bolete is not closely related to species in the Xerocomus genus
– Considered a choice edible mushroom, less infested by maggots, but can bioaccumulate trace metals
**Varieties:**
– Varieties glaber and macrostipitatus described from Nova Scotia, Canada, in 1976
– Taxon name comes from the Latin limatulus, meaning polished or refined
– Starting date of fungal taxonomy set to coincide with works of Elias Magnus Fries
– Species name badia means chestnut brown
– Common name derived from the color of the cap, likened to a bay horse’s coat
**Ecology, Distribution, and Habitat:**
– Mushrooms appear in huge numbers
– Bay bolete is mycorrhizal with some saprophytic tendencies
– Ectomycorrhizae formed with spruce have high nutrient storage potential
– Distribution in Europe, Asia, North America, and Mexico
– Fruiting peak after rain in warm weather
**Uses:**
– Highly regarded as an edible mushroom
– Can cause allergic reactions in some individuals
– Mild flavor compared to other mushrooms
– Can be eaten raw or cooked in various ways
– Fruit bodies used for making dyes
**Research:**
– Fruit bodies have antioxidative properties
– Contains theanine and indole compounds
– Studies on tumor cell growth inhibition
– Bioaccumulation of mercury, cobalt, and organochlorine compounds
– Bioaccumulation of radioactive caesium post-Chernobyl