Influence of E. variegatus on S. littoralis induced parasitoid attraction, volatile emission and defense gene expression. (a): Choice of C. marginiventris, shown as the average numbers (+SE) of wasps per release (groups of 6) and olfactometer arm. Control = Uninfested plant; S.l. = S. littoralis infested plant; E.v.+S.l. = E. variegatus and S. littoralis infested plant; Empty = Empty arms. Different letters indicate significant differences between treatments (p < 0.05). (n = 8). (b): Average choice of C. marginiventris parasitoids with different previous host-experience. Naive = No experience; SS = Host-presence with S. littoralis induced plant odours; SES = Host presence with E. variegatus and S. littoralis induced plant odours. Different letters denote a significant difference between experience type within a treatment (p < 0.05). Stars denote significant effects of treatment (T), experience (E) and the interaction (TxE) (*p < 0.05, **p < 0.01, ***p < 0.001). (c): Average volatile emission (+SE) of herbivore infested maize seedlings. For compound descriptions, see legend in Figure 1. (d): Average change in gene expression (+SE) of herbivore infested maize seedlings relative to uninfested control plants. Stars denote significant differences between S. littoralis and E. variegatus and S. littoralis induced plants (p < 0.05) (n = 3).