Host and parasitoid recruitment for quantifying losses from parasitism, with reference to Pieris rapae and Cotesia glomerata

A technique for quantifying mortality due to insect parasitoids in insect populations is presented. The method is based on the measurement of recruitment to both the host susceptible stage and the pool of parasitized hosts. The technique provides estimates of generational mortality due to parasitism and, when combined with estimates of population density, provides estimates of other mortality rates acting on both host and parasitoid populations. Such estimates are available both for the generation as a whole and for separate sampling periods. The method is illustrated by application to two generations of Pieris rapae L. (Lepidoptera: Pieridae) and its larval parasitoid Cotesia (Apanteles) glomerata (L.) (Hymenoptera: Braconidae).