Host Regulation by Insect Parasitoids

The effects of the parasitoid on the development, behavior, physiology, and morphology of the host have been described and often attributed to the feeding larvae within the host. It has become increasingly clear that these effects on the host are often due to factors injected into the host by the ovipositing female. This realization, along with the realization that the host is often dramatically altered after oviposition by the parasitoid, has given rise to the concept of host regulation as one of the key aspects of parasitoidism. The physiological and biochemical changes that occur after parasitoidism are described. These include paralysis; changes in growth, feeding, and development; changes in hemolymph solutes, proteins, carbohydrates, lipids, nitrogen metabolism and excretion; as well as changes in select tissues including the endocrine and reproductive system of the host. The sources of the factors that may elicit these changes are discussed and include the role of the adult female, her progeny, and associated teratocytes.