Olfactory Response of Sitophilus zeamais Adults to Odours of Semolina Pasta and Semolina Pasta Enriched with Different Amounts of Acheta domesticus Powder

The behavioural response of adult maize weevil, <i>Sitophilus zeamais</i>, to different types of semolina pasta enriched or not enriched with increasing proportions (5%, 10%, and 15%) of house cricket (<i>Acheta domesticus</i>) powder was investigated in olfactometer arena bioassays by using trap devices. In the five-choice behavioural bioassays, the number of <i>S. zeamais</i> adults attracted to 100% durum wheat semolina pasta was significantly higher than those attracted to the other pasta types enriched with <i>A. domesticus</i> powder. In the two-choice behavioural bioassays, the Response Index for each pasta type was positive and significant. However, although not significant, there was a progressive reduction in the Response Index as the cricket powder content increased. In similar experiments, there were no significant differences between cricket powder alone and the control in the number of attracted <i>S. zeamais</i>, indicating a neutral effect towards insects. These observations suggest that the lower attractiveness of pasta enriched with house cricket powder is mainly due to the masking of host food odours. Solid-phase microextraction coupled to gas chromatography-mass spectroscopy identified a total of 18 compounds in the head-space samples of the different types of pasta, highlighting differences in volatile composition. Some volatile compounds were only present in the pasta produced with cricket powder. In particular, 1-octen-3-ol and phenol were present in the samples containing 5%, 10%, or 15% cricket powder; pentanal, benzaldehyde, and dimethyl disulphide were present in samples containing 10% or 15% cricket powder; and 2,5-dimethyl-pyrazine was present in the sample containing 15% cricket powder. Further investigation with individual compounds and mixtures is needed to define the chemical basis of the differences in the insect olfactory preference observed in this study.