Cordyceps is a genus of ascomycete fungi (sac fungi) with about 400 species. Most "Cordyceps" species are parasitoids. They are parasitic mainly on insects and other arthropods. A few are parasitic on other fungi. The generic name "Cordyceps" is taken from the Greek word κορδύλη "kordýlē", meaning "club", and the Latin stem "-ceps", meaning "head".