Observed and compared the morphological characters of various instars of Encyrtus sasakii Ishii parasitized in Eulecanium kuwanai Kanda. Microphotographs were taken of the bodies. Study shows that： Encyrtus sasakii Ishii reproduces annually and overwinters as pupa in their host. Besides the individual differences resulting from development, the 1st and 2nd instar larvae have long breath pedicles in the end of abdomen, and with the larva molting during development, the exuvia accumulate at the end of the body, form a hollow sac called caudal sac that cover the breath pedicle during 3rd and 4th instar larvae. The scutulis of females are yellow, and foreside of wings is light fumed with a dark blotch covered by dense black thick hairs. While the males are black brown, the wing is light in color without a dark blotch.
