## 3 Results
### Behavioural Tests  
The results of the Y-tube olfactory bioassays are presented in Figure 2. When olfactory cues were provided, _A. melinus_ mated females showed significant preferences for lemon fruit infested with _A. aurantti_ over non-infested ones, but no such preference was observed when compared between non-infested and infested oranges or mandarins. (lemon: \(\chi^{2}\) = 4.900, df = 1, \(p\) = 0.027; orange: \(\chi^{2}\) = 2.500, df = 1, \(p\) = 0.114; mandarin: \(\chi^{2}\) = 1.600, df = 1, \(p\) = 0.206). There was no significant time differences of _A. melinus_ to choose the chamber connected to _A. aurantti_ infested citrus fruit. Indeed, _A. melinus_ females slightly preferred and taken the initiative to the chambers containing infested fruit rather than health fruit (lemon: \(\chi^{2}\) = 26.000, df = 21, \(p\) = 0.206; orange: \(\chi^{2}\) =28.000, df = 21, \(p\) = 0.140; mandarin: \(\chi^{2}\) = 26.333, df = 21, \(p\) = 0.194) (Table 2).  
\begin{table}
\begin{tabular}{l l l c c c c c c c} \hline \hline \multirow{2}{*}{**Feature ID**} & \multirow{2}{*}{**NIST RI**} & \multirow{2}{*}{**Chemical Compounds**} & \multicolumn{2}{c}{**Lemon**} & \multicolumn{2}{c}{**Mandarin**} & \multicolumn{2}{c}{**Change**} \\ \cline{3-10}  & & & **Non-Infected** & **Infected** & **Non-Infected** & **Infected** & **Non-Infected** & **Infected** \\ \hline
4.644-151.1 & 1302.2 & \multirow{2}{*}{Methodary polynomial cosine} & 4.25 \(\pm\) 1.362 & 4.79 \(\pm\) 0.307 & 5.568 \(\pm\) 1.504 & 4.512 \(\pm\) 1.337 & 12.081 \(\pm\) 2.677 & 9.811 \(\pm\) 0.43  
Figure 1: Principal Component Analysis (PCA) of volatile profiles from infested and non-infested fruit of three different citrus species. PCA scores plot and biplot of lemon (**a**), mandarin (**b**) and orange fruit (**c**), showing volatile correlations with the first and second principal component; PCA score plot, highlighting cluster of VOCs attributable to species or infestation status; PCA biplot highlighting changes in chemicals attribute to species or infestation status.  
Figure 3: Attraction of female _Aphytis melinus_ to VOCs differentially emitted by _A. auranti_-infested citrus fruits. Choice bioassays were conducted in a Y-tube olfactometer presenting one of the two dosage levels (10 and 20 \(\mu\)L/mL) of citrus fruits VOCs vs. hexane. Asterisks indicate significant differences between numbers of VOC and control choices (\(\chi^{2}\) test with [PERSON] correction, \(p<0.05\)). To the left of the bars is the proportion of females that made a choice for one of the two odours, as well as the total number of females that were tested.  
Figure 2: Attractiveness of _Aonidiella auranti_-infested citrus fruit towards _Aphytis melinus_ mated females. Two choice bioassays were conducted in a still air arena with citrus fruit, infested or not by California red scale, providing olfactory cues. Forty wasps were tested in each bioassay. For each test, asterisks indicate significant differences in the number of wasps choosing different cue (\(\chi^{2}\) test with [PERSON] correction, \(p<0.05\)). To the left of the bars is the proportion of females that made a choice for one of the two odours, as well as the total number of females that were tested.