Life tables were constructed for the noctuid Plutella xylostella in a broccoli field in Okayama in June, September and October 1989. Natural enemies and/or rainfall were excluded using a net, a tangle-foot coated fence and a plastic roof. One-third to one-half of individuals disappeared in the early immature stages. Mortality was less in the plots with no rainfall, indicating that washing off of eggs and larvae by rain and drowning of young larvae after rain were major mortality factors. The percentage parasitism by the larval parasitoid, Apanteles plutellae [Colesia pluiellae], and the pupal parasitoids, Diadromus subtilicornis and Tetrastichus sokolowskii, was high in September. Temperatures of more than 30'C tended to delay development, and reduced the survival of immature stages and the fecundity of females. When the moth was fed on the wild cruciferous weed Capsella bursa-pastoris, its reproductive capacity was lower compared with that when fed on broccoli. none