Effect of fibre polarity on the male compounds collected by SPME.

We compared the effect of fibre polarity on the male and female compounds collected by SPME, using an apolar carbowax/divinylbenzene StableFlex fibre (CW/DVB, 70 µm, Supelco, St Quentin-Fallavier, France) and a polar polydimethylsiloxane fibre (PDMS, 100 µm, Supelco, St Quentin-Fallavier, France). Both fibres were consecutively rubbed on the principal external parts of the same individual fly (head, thorax, wings, abdomen, genitalia). To avoid any effect of the first rubbing on the second SPME sampling, we swapped both sampling procedures as follows: Sampl. 1 & 2: first CW/DVB sampling on intact flies (Sampl. 1) followed by PDMS sampling (Sampl. 2); Sampl. 3 & 4: first PDMS sampling on intact flies (Sampl. 3) followed by CW/DVB sampling (Sampl. 4).The SPME fibre was introduced into the GC-MS injection port as described in EXPERIMENTAL PROCEDURES.Results are given as the mean (and SEM) of the relative amount of each compound (expressed in %). For each compound, the data obtained by the four sampling methods were compared using a Kruskal-Wallis test followed by Dunn's multiple pairwise comparisons (two-tailed with Bonferroni correction). Significant Kruskal-Wallis tests are shown by the K and p values, while the results of the subsequent Dunn's multiple pairwise comparison ares shown by the lowercase letters besides the relative amounts. The peak numbers and abbreviations refer to the compounds listed in Table 1.