Natural regulation of Pieris rapae Linnaeus (Lepidoptera : Pieridae) in Canterbury, New Zealand

摘要

Abstract Life tables were constructed for five populations of Pieris rapae L. Field counts of all stages fitted a negative binomial distribution, and a plan for sampling to a fixed level of precision is given. Mortality of early-instar larvae was due mainly to predation by syrphid larvae and the harvestman Phalangium opilio L. Bird predation was evident only on late-instar larvae during the second generation and on overwintering pupae. Life table analysis showed that mortality factors which contributed most to population trend operated at the pupal stage.