SummaryArrhenosphaera cranei, gen. et sp. nov., fungus, gen.Arrhenosphaera, family Ascosphaeraccae, order Ascosphaerales, class Ascomycetes, series Plectomycetes, subclass Euascomycetidae, was found in Venezuela in 1971. Its segmented and multinucleate hyphae are partly haploid heterothallic and partly diploid monoecious.Sexual reproduction was observed on a nutritive substrate of agar with honey. The gametangia are oval, black ascogonia with 4–10 trichogynes, and colourless, oval antheridia. Following conjugation plasmogamy occurs, by a part of the antheridial cytoplasm with some nuclei passing via a trichogyne into the ascogonium. This is followed by karyogamy and the subsequent mitotic and meiotic parthenogenetic divisions produce four male and four female haploid nuclei which remain within the former membrane to form an ascus. The unfertilized gametangia and segments of adjacent hyphae mass with the asci and unite in groups into compact spore balls and with some free spores form sporocysts (ascomata).Asexual reproduction occurred in slide culture without nutritients. The mycelium produced conidia with slightly larger spores than during sexual reproduction.Infected honeybee larvae filled with mycelium and sporocysts become dry and chalky, and infected pollen forms dry, hard plugs. The only known control of this fungus is achieved by maintaining strong colonies that are able to clean the combs of the fungus, and by burning combs containing infected larvae and flame-disinfecting other frames and the hive.