## 4 Discussion  
The results of multiple-choice behavioural bioassays showed that _S. granarius_ adults are able to selectively respond to odours of different types of Italian cereal- and legume-based pastas. In fact, in both the day one and day seven tests, cereal-based pastas were overall more attractive than legume-based ones. Among all pasta samples tested, those made from _T. turanicum_ (Khorasan) and five cereals (wheat, spelt, barley, maize, and rye) were the most attractive. Whereas, those from whole wheat _T. durum, T. dioccum_, and particularly from different legumes, were the weakest attractants. To investigate the nature of the low attractiveness of legume-based pastas to granary weevil adults, two-choice behavioural bioassays were performed. In these experiments, pastas obtained from _T. turanicum_ (Khorasan pasta) and _C. arietinum_ (chickpea pasta) confirmed their respective high and low attractiveness to adult insects. Whereas, a 1:1 mixture of the two pastas elicited a significant insect attraction, comparable to that of _T. turanicum_ pasta. This strongly suggests that the low attractiveness of legume-based pastas to granary weevils mainly depends on the lack of attractive odour stimuli rather than the presence of repellent volatile compounds. This hypothesis was further confirmed by pairwise comparisons of different mixtures of the two types of pasta where a preferential insect orientation was not observed due to the presence of both the attractive (Khorasan pasta) and the non-attractive source (chickpea pasta) in both test odour-stimuli. Several studies have highlighted the importance of ratios and concentrations of volatiles for host location by phytophagous insects [38-42]. Male and female granary weevil antennae are capable of selectively perceiving a wide range of individual cereal grain volatiles [43] and kernel solvent extracts from different durum and bread wheat genotypes [35]. In behavioural bioassays testing various concentrations of 20 EAG (Electroantennography)-active volatiles, five compounds (1-butanol, 3-methyl-1-butanol, pentanal, maltol, and vanillin) acted uniquely as attractants, three compounds (1-pentanol,(_E,E_)-2,4-heptadienal, and phenylacetaldehyde) were attractive at lower concentrations but repellent at higher doses, and 12 compounds (1-hexanol, butanal, hexanal, heptanal, (_E_)-2-hexenal, (_E,E_)-2,4-nonadienal, (_E,E_)-2,4-decadienal, 2,3-butanedione, 2-pentanone, 2-hexanone, 2-heptanone, and furfural) were repellent at high doses, strongly suggesting that host finding behaviour of granary weevils depends on the balance of positive and negative semiochemical stimuli [13]. In the head-space of different pasta samples, a total of 50 volatile compounds were identified by chemical analysis. Even though many of these compounds were found in the head-space fractions of both cereal- and legume-based pastas, differences in their relative proportions along with qualitative differences were highlighted. In fact, the odour profiles of cereal-based pastas mainly contained aldehydes, followed by alcohols, aromatics, furans, and hydrocarbons whereas those of legume-based pastas were characterised by a high content of alcohols, followed by aldehydes, aromatics, furans, and lactones. Short chain aldehydes are lipid oxidation products of the hydroperoxide lyase pathway of oxylipin metabolism [44; 45], which can be converted into the corresponding alcohols by the action of alcohol dehydrogenase [46]. Ketones and hydrocarbons are also derived from lipid oxidation, from both enzymatic and non-enzymatic oxidative degradations, while terpen are naturally present/synthesised by the plant [47]. Lactones are strongly related to legumes [48]. Furans are mainly produced by the Maillard reaction during pasta drying [34; 49]. Differences in composition of the pasta volatile fractions might account for differences in attractiveness of various pasta samples to granary weevil adults. In our study, _S.