Many phytophagous insects utilize specific plants for breeding and feeding as a consequence of a plant-insect evolutionary arms race. The trait of flower consumption has evolved in numerous insect lineages; nevertheless, its selectivity has been overlooked. Flowers sometimes contain more defensive compounds than leaves, so the flower-breeding insects may have more severe selectivity compared to leaf eaters. On the other hand, flower-breeding insects may use various flower species flexibly, since the blooming seasons are relatively limited, thus extreme narrow selectivity may be disadvantageous for breeding and feeding.
　Drosophila elegans is a flower-breeding fly, with adult visit blooming flowers to lay eggs, and the larvae feed on the fallen flowers. However, the extent to which they selectively utilize specific flower species has not been investigated. To examine the flower-visiting and breeding selectivity in their natural habitat, the numbers of flies that visited and emerged from each flower were quantified. We found that the flies visited several flower species, such as Ipomoea (order Solanales), Alpinia (order Zingiberaceae), Lilium (order Liliales), and Thunbergia (order Lamiales), but not Mansoa and Allamanda, indicating that they selectively visit phylogenetically diverse flower species. Importantly, numerous flies emerged from Ipomoea and Alpinia, while almost none emerged from Lilium and Thunbergia. This suggests that D. elegans selectively utilizes only specific flower species for breeding, despite visiting a variety of flowers. To verify this, we examined the egg-laying selectivity under the experimental condition, and found the numbers of eggs laid on Ipomoea and Alpinia were significantly greater than on Lilium. To test whether the egg-laying selectivity aligns with the flower qualities as larval food, the adult emergence ratios of collected fly eggs developed in a harvested flower were quantified. More adults were successfully emerged from Ipomoea and Alpinia than from Lilium, where no adults emerged, indicating that the flowers preferred by flies for oviposition were more suitable for breeding. Finally, to clarify the reason why D. elegans visits Lilium unsuitable for breeding, we investigated both the feeding behavior and the survival increase of starved adult flies in the presence of flowers. We found that the adults fed on, at least, the pollen coat, and the existence of Lilium flowers increased their survival. Thus, they do not breed in Lilium, but utilize them for feeding. Together, we demonstrate that D. elegans utilizes a diverse range of flower species and selectively employs different flowers based on the purposes of breeding and feeding.