Four kinds of microsporidian spores,different in morphology and in pathogenicity tosilkworm,Bombyx mori,were collected from silkworms and wild insects,i. e. MA-1 andMD-1 from silkworm rearing production,Pha-M from a mulberry insect Phyllobroticaarmata in Sichuan Province and Ha-M from mulbeery looper,Hemerophila atrilineata,in Zhenjiang area. Their spore morphology,pathogenicity to silkworms,serological rela-tionships,parasitizing sites and pathological changes in infected tissues and cells insidethe silkw...