Table 2. Main gland volatiles identified by GC-MS.

Retention indices	Compound name	CAS-Number	MW	Comment
1011/1018	methyl-1,4-benzoquinone	000553-97-9	122.04
1098/1109	ethyl-1,4-benzoquinone	004754-26-1	136.05
1350/1367	methyl-1,4-hydroquinone	000095-71-6	124.05
1432	ethyl-1,4-hydroquinone	2349-70-4	138.07
1477	1,6-pentadecadiene	58045-15-1	208.38	a, low peak
1492	1-pentadecene	013360-61-7	210.24
1552	1,2-dimethoxy-4-n-propylbenzene	005888-52-8	180.12	b, low peak
1593	1-hexadecene	000629-73-2	224.25	low peak
1663/1672	1,8-heptadecadiene	Not available	236.25	a
1693	1-heptadecene	006765-39-5	238.27

a: based on previous data [21], the positions of the double bonds (especially the second one) need to be confirmed; b: based on PBM (probability-based matching algorithm) database searching result (matching quality 86%). The data refer to both prothoracic and abdominal glands from wild-type adult beetles at stage A10.