Influence of E. variegatus and S. littoralis infestation on 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. Different experience types are pooled. Control = Uninfested plant; S.l. = S. littoralis infested plant; E.v. = E. variegatus infested plant; Empty = Empty arms. Different letters indicate significant differences between treatments (p < 0.05) (n = 6). (b): Average choice of C. marginiventris parasitoids with different previous host- or non-host experience. Naive = No experience; SS = Host-presence with S. littoralis induced plant odours; SE = Host presence with E. variegatus induced plant odours. EE = Non-host presence with E. variegatus induced plant odours; ES = Non-host presence with S. littoralis induced odours. 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. 1 = (Z)-3-hexenal; 2 = (E)-2-hexenal; 3 = (Z)-3-hexen-1-ol; 4 = β-myrcene; 5 = (Z)-3-hexenyl acetate; 6 = (Z)-β-ocimeneN; 7 = linalool; 8 = (3E)-4,8-dimethyl-1,3,7-nonatriene (DMNT); 9 = phenethyl acetate; 10 = indole; 11 = methyl anthranilate; 12 = geranyl acetate; 13 = E- β-caryophyllene; 14 = (E)-α-bergamotene; 15 = E-β-farnesene; 16 = β-sesquiphellandreneN 17 = unknown sesquiterpeneN. Compounds denoted with "N" were only tentatively identified. Stars denote significant differences between S. littoralis and E. variegatus induced plants (p < 0.05). (d): Average change in gene expression (+SE) of herbivore infested maize seedlings relative to uninfested control plants. Stars in graphs (c) and (d) denote significant differences between S. littoralis and E. variegatus induced plants (p < 0.05).