Two new species of Nubenocephalus (Apicomplexa: Eugregarinida: Actinocephalidae) are described from adult damselflies sampled in Cayo District, Belize, Central America. Nubenocephalus nickoli n. sp. is described from the American Rubyspot damselfly, Hetaerina americana, and the Smoky Rubyspot damselfly, Hetaerina titia (Odonata: Zygoptera: Hetaerinidae), and Nubenocephalus xunantunichensis n. sp. is described from the Comanche Dancer, Argia chelata (Odonata: Zygoptera: Coenagrionidae). New, complete morphological data sets are reported for populations of Nubenocephalus nebraskensis and Nubenocephalus secundus, and a complete, synoptic reevaluation of diagnostic morphological characters used to discriminate species within Nubenocephalus is presented for all known species of the genus in the New World. Nubenocephalus nebraskensis is reported from Argia apicalis for the first time.