How conspecific and allospecific eggs and larvae drive oviposition preference in Drosophila.

Where to lay the eggs is a crucial decision for females as it influences the success of their offspring. Female flies prefer to lay eggs on food already occupied and consumed by larvae, which facilitates social feeding, but potentially could also lead to detrimental interactions between species. Whether females can modulate their attraction to cues associated with different species is unknown. Here we analyzed the chemical profiles of eggs and larvae of 16 Drosophila species, and tested whether Drosophila flies would be attracted to larvae treated food or food with eggs from 6 different Drosophila species. The chemical analyses revealed that larval profiles from different species are strongly overlapping, while egg profiles exhibit significant species-specificity. Correspondingly, female flies preferred to lay eggs where they detected whatever species' larval cues, while we found a significant oviposition preference only for eggs of some species but not others. Our findings suggest that both larval as well as egg cues present at a given substrate can drive oviposition preference in female flies.