Electroantennographic and Behavioral Response of Female Moroccan locusts [Dociostaurus maroccanus (Thunberg, 1815) (Orthoptera: Acrididae)] to Male-Specific Aldehydes

The Moroccan locust <i>Dociostaurus maroccanus</i> (Thunberg, 1815) (Orthoptera: Acrididae) is recognized as a serious pest of pastures and crops in many Mediterranean countries. So far, the identification of chemical compounds involved in intraspecific communication has been elusive, with only one male-specific compound, namely (2<i>E</i>,7<i>R</i>,11<i>R</i>)-3,7,11,15-tetramethylhexadec-2-enal (2<i>E</i>,7<i>R</i>,11<i>R</i>-phytal), proposed as candidate sex pheromone component. Previous works reported that males also release the sex-specific long-chain aldehydes tetradecanal and hexadecanal, although no evidence of their role in chemical signaling has been presented so far. Here we additionally report another male-specific compound, viz. pentadecanal, and also report the electroantennographic and behavioral responses of virgin and mated females to these three aldehydes. We first demonstrated that their release is age-dependent, with emission overall peaking at 1-2 weeks after fledging. Solid-phase microextraction analyses from male hind legs suggest that these aldehydes are released from this body part. Overall, the antennae of virgin and mated females exhibited a dose-dependent response to increasing concentrations of each aldehyde, except for the response of virgin females to hexadecanal. Significant differences were observed between virgin and mated females at all doses of hexadecanal, while the mating status did not influence the response to tetradecanal and pentadecanal. Furthermore, the behavioral response of females varied according to their mating status. Specifically, mated females showed a significant preference for tetradecanal and pentadecanal, whereas a slight but non-significant attraction to hexadecanal was observed on virgin females. These findings provide new insights into the sexual communication of the species, although further research is needed to decipher their ecological function, especially on mated females.