Altered volatile profile associated with precopulatory mate guarding attracts spider mite males.

Proximate factors affecting animal behavior include stimuli generated by conspecifics. In spider mites of the genus Tetranychus (Acari: Tetranychidae), males guard pre-reproductive quiescent females, because only the first mating results in fertilization. In a dual-choice experiment, more adult males of T. urticae were attracted to females guarded by a male than to solitary females. Because spider mites are known to perceive volatiles, we hypothesized that guarded and solitary females differ in the volatile blends emitted. To test this hypothesis, headspace volatiles of guarded females, solitary females, and solitary males were collected, respectively. GC/MS analysis detected octanal, methyl salicylate, ethyl 4-ethoxybenzoate, and methyl cis-dihydrojasmonate in all of the groups. Orthogonal Projection to Latent Structures Discriminant Analysis (OPLS-DA) of the blends clearly discriminated guarded females from solitary females, supporting our hypothesis. Individual compounds did not show significant difference in emission rates for guarded females vs. solitary females, suggesting that differences lay in the total blend composition. OPLS-DA did not discriminate between the blends emitted by guarded females and solitary males. In conclusion, the differences in the volatile blends are likely to mediate male discrimination between guarded and solitary females.