Figure 14.3 Effects of a parasitoid on populations of red scale insects. (a) The California red scale, a tiny insect with a hard shell, feeds on the sap of citrus trees and other plants. The parasitoid wasp lays its eggs under the hard shell of the scale insect. When the eggs hatch, the larvae slowly consume the scale insect. (b) After introducing large numbers of scale insects to trees—during the months indicated by yellow shading on the x axis—the scale insect population grew rapidly. Soon after the addition of the scale insects, the number of juvenile and adult parasitoid wasps began to rapidly increase. This increase in parasitoid wasps caused a subsequent rapid decline in scale insects.

Data from W. Murdoch et al., Host suppression and stability in a parasitoid-host system: Experimental demonstration, Science 309 (2005): 610–613.