Host and geographical ranges are updated for the microsporidium Paranosema locustae; this pathogen was developed in the USA as a long-term microbial control agent of grasshoppers. Currently known to be susceptible to P. locustae, either naturally or experimentally, are 121 species of Orthoptera from North and South America, Africa, Australia, China, and India. Most belong to the Acrididae (112), and within this family, to the Melanoplinae (36), Oedipodinae (35), and Gomphocerinae (35). The host range of P. locustae, as presently understood, is based largely on morphology and could change if molecular techniques revealed cryptic species. The North American isolate is not only the best studied, but the one established after its introduction into Argentina, and produced and used in China: it can be considered a generalist pathogen. As such, P. locustae may have the ability to alter, through differences in host susceptibilities, the structure of grasshopper assemblages in areas where it was not present before. Long-term careful monitoring of key grasshopper species in areas of pathogen introduction/establishment may reveal such effects.