A fungus associated with a spider collected from the Mushroom Research Centre, Chiang Mai, Thailand was found to represent a new species of the genus Cordyceps. It is described as C. mrciensis sp. nov. C. mrciensis differs from other species occurring on spiders in that the stromata have a fertile part with a distinctive sterile appendage, superficial perithecia and ascospores that do not break into secondary partspores.
