Trichosia (Baeosciara) sinuata Menzel & Mohrig, previously known only from the holotype from Austria, is redescribed and its biology discussed. Individuals of the species were reared from an old-growth forest bracket fungus Fomitopsis rosea (Alb. & Schw.: Fr.) P. Karst from eastern Finland. We suggest that B. sinuata might be parasitised by the ichneumonid wasp Stenomacrus curvulus (Thomson). none