The Agricultural Research Service Collection of Entomopathogenic Fungal Cultures is the world's largest, most kaleidoscopic, and most comprehensive collection of living cultures of fungi that are pathogenic to or associated with insects, spiders, mites, ticks, and other invertebrates. Some isolates in the collection are not themselves invertebrate pathogens but are critically important for the improvements of taxonomies and systematics for the many diverse groups of fungi represented here. As of July 2016, ARSEF maintains more than 13000 isolates of more than 700 taxa of fungi isolated from 1300 hosts collected at more than 2400 locations on every continent.