Figure 3. Effect of parasitism on host-predator interactions in the laboratory.

A predator was introduced on a twig, 2–4 cm away from a parasitized or unparasitized caterpillar, without disturbing the caterpillar. A. Upon being encountered by a predator, parasitized caterpillars (black bars: mean+s.e.m.) swung their heads more frequently than unparasitized (white bars: mean+s.e.m.) caterpillars (***: GLM with quasi-Poisson errors, F_1,37 = 57.6, P<0.001). B. The proportion of predators that gave up or were knocked off the twig was higher for parasitized compared with unparasitized hosts (**: Fisher's Exact Test, P = 0.008). Numbers of replicates are given in brackets.