Interactions between the egg and larval parasitoids of a gall-forming midge and their impact on the host

1. The gall-forming midge Rhopalomyia californica was exposed experimentall y to parasitism and predation during only the egg stage, during only the la rval stage, during neither stage, or during both stages. 2. The combined action of natural enemies that attack during both the egg s tage and the larval stage led to the lowest number of midges and total inse cts (midges + parasitoids) in the next generation, and the highest percenta ge parasitism. 3. The larval parasitoid killed a large fraction of hosts without producing new parasitoid offspring, while there is some indication that the egg para sitoid on its own tended to produce the most parasitoid offspring. The cont rasting implications of host mortality versus parasitoid production for bio logical control are discussed. 4. Exposure to larval parasitoids resulted in a reduction in the number of egg parasitoid offspring produced, but exposure to the egg parasitoid did n ot affect the number of larval parasitoid offspring produced significantly.