Pericystis Betts (1912)[1] Ascosphaera is a genus of fungi in the family Ascosphaeraceae.

It was described in 1955 by mycologists Charles F. Spiltoir and Lindsay S.

[2] Members of the genus are insect pathogens.

The type species, A. apis, causes chalkbrood disease in honey bees.

[3] The reproductive ascospores of the fungus are produced within a unique structure, the spore cyst, or sporocyst.