Bitter bolete

''Caloboletus frustosus'' is a bolete fungus native to North America. Until 2014, it was known as ''Boletus frustosus''. Recent changes in the phylogenetic framework of the family Boletaceae prompted the transfer of this species, along with several other related boletes, including ''Caloboletus calopus'', to the genus ''Caloboletus''. It was first described scientifically in 1941 by mycologists Wally Snell and Esther Dick.