Mathilde Scheifler, Léonore Wilhelm, Bertanne Visser

Parasitoids have an exceptional lifestyle where juvenile development is spent on or in a single host insect, but the adults are free-living. Unlike parasites, parasitoids always kill their host. How parasitoids use such a limiting resource, particularly lipids, is important for their chances to survive and reproduce. In part 1, we describe the parasitoid lifestyle, including typical developmental strategies. Lipid metabolism in parasitoids has been of interest to researchers since the 1960s and continues to fascinate ecologists, evolutionists, physiologists, and entomologists alike. One reason of this interest is that the majority of parasitoids do not accumulate triacylglycerols as adults. Early research revealed that some parasitoid larvae mimic the fatty acid composition of their host, which may result from a lack of de novo triacylglycerol synthesis. More recent work has focused on the evolution of lack of adult triacylglycerol accumulation and consequences for life history traits in parasitoids. In part 2 of this chapter, we discuss research efforts on lipid metabolism in parasitoids from the 1960s onwards. Parasitoids are master manipulators of their host’s physiology, including lipid metabolism. Parasitoids have indeed evolved a range of mechanisms to affect the release, synthesis, transport, and take-up of lipids from their host. We detail the effects of parasitism on host physiology in part 3 of this chapter.