## 2 Results
### O. vulgaris Terpenoids Exert Toxic Effects on S. littoralis larvae  
Having assessed the ability of _O. vulgare_ to respond to _S. littoralis_ feeding by modulating terpenoid biosynthesis and gene expression, we tested the effect of _O. vulgare_ terpenoids on _S. littoralis_ larvae. After several trials we found that the 2 nd and 3 rd instar larvae showed a higher sensitivity to _O. vulgare_ terpenoids; therefore, we used these two instar stages for all tests and measurements were performed during transition from one instar to the next one. Feeding on _O. vulgare_ leaves caused a significantly (\(p<0.05\)) lower survival percentage of _S. littoralis_ larvae, with respect to the artificial diet (ACD) \begin{table}
\begin{tabular}{c c c c} \hline
**Compounds** & **Control** & **HW** & **Frass** \\ \hline
**Green Leaf Volatiles** & & & \\ (_E_)-2-Hexenal & nd & 8.96 \(\pm\) 3.66 ** & nd \\ (_Z_)-3-Hexenol & nd & 9.43 \(\pm\) 0.79 ** & nd \\ \hline
**Monoterpenses** & & & \\ Sabinene & 116.32 \(\pm\) 0.24 & 133.99 \(\pm\) 8.09 & 2.84 \(\pm\) 0.34 \\ \(\beta\)-Pinene & 4.18 \(\pm\) 0.03 & 4.75 \(\pm\) 0.56 & nd \\ \(\beta\)-Myrcene & 31.93 \(\pm\) 1.00 & 34.61 \(\pm\) 1.88 & 0.42 \(\pm\) 0.04 \\ \(\alpha\)-Terpinene & 25.62 \(\pm\) 0.5 & 32.38 \(\pm\) 2.30 * & 0.77 \(\pm\) 0.12 \\ _p_-Cymene & 53.87 \(\pm\) 18.84 & 83.43 \(\pm\) 10.39 & 2.97 \(\pm\) 0.60 \\
1-Octen-3-ol & 5.12 \(\pm\) 0.31 & 13.75 \(\pm\) 3.67 & nd \\ Limonene & 14.55 \(\pm\) 2.13 & 20.21 \(\pm\) 0.05 * & nd \\ \(\beta\)-Dellandrene & 17.91 \(\pm\) 1.36 & 28.83 \(\pm\) 2.95 * & nd \\ \(\gamma\)-Terpinene & 187.89 \(\pm\) 1.61 & 193.92 \(\pm\) 15.28 & 8.60 \(\pm\) 1.17 \\
1-Octenyl-3-acetate & 20.01 \(\pm\) 0.93 & 24.75 \(\pm\) 4.29 & nd \\ _Trans_-sabinene hydrate & 52.28 \(\pm\) 5.31 & 98.07 \(\pm\) 10.80 ** & 1.41 \(\pm\) 0.32 \\ _Cis_-sabinene hydrate & 700.21 \(\pm\) 71.55 & 1062.03 \(\pm\) 167.15 ** & 19.38 \(\pm\) 1.53 \\ Linalool & 7.40\(\pm\)0.49 & 17.79 \(\pm\) 0.62 * & nd \\ Linalool oxide & 4.33 \(\pm\) 0.15 & 6.90 \(\pm\) 0.74 & nd \\ Terpinen-4-ol & 8.12 \(\pm\) 0.86 & 10.78 \(\pm\) 2.03 & 1.16 \(\pm\) 0.16 \\ \(\alpha\)-Terpineol & 43.64 \(\pm\) 4.56 & 60.50 \(\pm\) 11.09 * & 1.80 \(\pm\) 0.20 \\ _Trans_-dihydroxycorvone & 4.04 \(\pm\) 0.28 & 5.88 \(\pm\) 0.23 ** & nd \\ _Cis_-dihydroxycorvone & 9.20 \(\pm\) 0.56 & 12.70 \(\pm\) 1.68 * & 1.57 \(\pm\) 0.29 \\ Sabinene hydrate acetate & 5.59 \(\pm\) 0.09 & 6.76 \(\pm\) 1.11 & nd \\ Carvacrol methyl ether & 44.29 \(\pm\) 1.77 & 86.34 \(\pm\) 5.03 ** & 3.35 \(\pm\) 0.44 \\ Linaly acetate & 51.03 \(\pm\) 3.11 & 88.85 \(\pm\) 10.51 ** & 2.45 \(\pm\) 0.18 \\ Thymol & 4.11 \(\pm\) 0.33 & 6.92 \(\pm\) 0.32 ** & nd \\ Carvacrol & 959.26 \(\pm\) 8.90 & 1159.39 \(\pm\) 84.46 & 109.76 \(\pm\) 6.96 \\ \hline
**Sesquierpenses** & & & & \\ Bicyclebenzene & 11.49 \(\pm\) 1.54 & 18.95 \(\pm\) 1.32 * & nd \\ \(\beta\)-Cubebene & 5.99 \(\pm\) 0.92 & 12.13 \(\pm\) 0.03 ** & nd \\ \(\alpha\)-Copaene & 10.93 \(\pm\) 1.31 & 7.73 \(\pm\) 2.10 & nd \\ \(\beta\)-Caryophyllene & 40.81 \(\pm\) 2.66 & 58.38 \(\pm\) 5.43 * & 1.69 \(\pm\) 0.29 \\ \(\alpha\)-Humulene & 5.65 \(\pm\) 1.04 & 7.65 \(\pm\) 0.20 & nd \\ Germacrene D & 37.19 \(\pm\) 2.72 & 49.46 \(\pm\) 2.96 * & 1.79 \(\pm\) 0.37 \\ Bicyclogermacrene & 24.05 \(\pm\) 3.32 & 33.18 \(\pm\) 2.12* & 1.13 \(\pm\) 0.12 \\ \(\beta\)-Bisabolene & 93.00 \(\pm\) 7.33 & 114.85 \(\pm\) 4.94 * & 5.33 \(\pm\) 0.93 \\ \(\alpha\)-Farmesene & 2.54 \(\pm\) 0.16 & 6.44 \(\pm\) 0.59 * & nd \\ \(\beta\)-Sesquierphalendrene & 6.91 \(\pm\) 0.92 & 12.71 \(\pm\) 0.80 ** & nd \\ Germacrene D-4-ol & 4.14 \(\pm\) 0.50 & 7.18 \(\pm\) 1.10 * & nd \\ _Trans_-farnesol & 3.94 \(\pm\) 0.07 & 4.07 \(\pm\) 0.38 & 0.81 \(\pm\) 0.15 \\ TOTAL & 2617.54 \(\pm\) 27.15 & 3544.65 \(\pm\) 66.13 & 163.16 \(\pm\) 6.58 \\ \hline \end{tabular} nd, not detectable indicates values below the limit of detection (LOD = 0.1 \(\mu\)g g\({}^{-1}\)).  
\end{table}