The smell of footprints in the Queensland fruit fly: signaling to conspecifics attracts eavesdropping predators

Cuticular hydrocarbons (CHCs) that cover the cuticle of insects and other arthropods, have been extensively studied for their vital role in preventing desiccation as well as for their function as ‘infochemicals’. Knowledge of cuticular chemical communication, however, mostly comes from studies of social insects. In contrast, the role of CHCs as infochemicals in non-social insects, such as Queensland fruit fly (Q-fly), Bactrocera tryoni, has received comparatively little attention. This potentially very important mediator of non-social insect interactions remains obscure in all but a handful of non-social insects. Increasing the potential importance of CHCs to insect ecology, in some insects CHCs are known to be left behind during locomotion. While almost nothing is known, such CHC traces provide ‘footprint’ cues that can be used by conspecifics for information about sex, age and mating status and may also be used by predators to detect and hunt prey. Q-flies are generally solitary insects but mating aggregations do occur in trees at dusk, and multiple females are often attracted to fruits to oviposit. Q-fly CHCs have recently been described and our pilot studies confirm deposition of CHC footprints and indicate that such footprints may have important biological functions. We here seek to investigate how conspecifics use CHC footprints to inform decisions about mating and oviposition, and whether predators use CHC footprints to inform hunting. We anticipate that Q-fly CHC footprints will be persistent markers and play a prominent role in the chemical ecology of Q-fly and its predators. Our study of CHC footprints in Q-flies opens a new path of research that will not only allow us to better understand the biology of Q-flies and other fruit flies, but also to explore the potential use of these chemical cues in the management of major fruit fly pests.