Insect parasitoids – those insects that deposit their eggs on or in the eggs, larvae or adults of other insects and whose offspring use the resources of those hosts to fuel development – provide a rich area of study for theoretical and mathematical biology. They also provide a broad collection of examples of how the tools developed in the previous chapters can be used (and they are some of my personally favorite study species; the pictures shown in Figure 4.1 should help you see why).

There is also a rich body of experimental and theoretical work on parasitoids, some of which I will point you towards as we discuss different questions. The excellent books by Godfray (1994), Hassell (2000a), and Hochberg and Ives (2000) contain elaborations of some of the material that we consider. These are well worth owning. Hassell (2000b), which is available at JSTOR, should also be in everyone's library.

It is helpful to think about a dichotomous classification scheme for parasitoids using population, behavioral, and physiological criteria (Figure 4.2). First, parasitoids may have one generation (univoltine) or more than one generation (multivoltine) per calendar year. Second, females may lay one egg (solitary) or more than one egg (gregarious) in hosts. Third, females may be born with essentially all of their eggs (pro-ovigenic) or may mature eggs (synovigenic) throughout their lives (Flanders 1950, Heimpel and Rosenheim 1998, Jervis et al. 2001). Each dichotomous choice leads to a different kind of life history.