Abstract: The infection process of two isolates of Metarhizium anisopliae on Plutella xylostella larvae was studied using transmission electron microscopy. The results showed that the penetration of the integument of P. xylostella larva by M. anisopliae，which was first observed in 22 h after inoculation, was the combination of mechanical pressure and enzymatic action. The penetrant hyphae produced lots of granule hyphal bodies by budding or septation, which became distributed throughout the body cavity of infected larva. Some filar hyphae were also seen in the hemocoel of infected larva.

Key words: Plutella xylostella, Metarhizium anisopliae, propagation, invasion process, transmission electron microscopy