This order of fungi contains more than 2,000 species, parasitic to different arthropods. These are ectoparasites living on the cuticle of their host. The host insect/arthropod is not killed by the fungus. However, the fungus penetrates the cuticle and obtains nutrients. The fitness of the parasitized host is reduced. The hosts are often beetles (e.g. from the families Coccinellidae, Carabidae, or Staphylinidae), but include also other insects and arthropods like mites.
The fungi do not form vegetative hyphae but produce male (antheridia) and female (perithecia) fruiting bodies. When the spores from the male fruiting bodies reach the flask-shaped female structures a sexual reproduction cycle is initiated and elongated or egg-shaped asci and ascospores are formed. Each ascus contains 4 two-celled ascospores.
The following genera and individual species of entomopathogens are currently entered in the system: