Late at night along 150 kilometers of Perth's northern coast, beetles with fuzzy undersides are gathering on candlestick banksia flowers—not to feed alone, but to mate. A four-year study from La Trobe University has revealed what scientists long missed: these nocturnal hairy scarab beetles are the true pollinators of one of Perth's most common native trees, drawn by flowers that smell uncannily like rockmelon.
The discovery rewrites what we thought we knew about how this iconic Australian tree reproduces. For years, ornithologists and ecologists assumed that honeyeaters and honey possums did the heavy lifting, visiting the flowers during daylight hours. Yet when researchers led by Stanislaw Wawrzyczek trained their cameras and video recorders on the trees, the insects that dominated the nighttime visitor logs were scarab beetles. They arrived not just to feed, but to couple—and in doing so, their hairy bodies became living pollen carriers. The sticky, unusually gooey pollen stuck to their underside as they mated and fed, then transferred to the next plant they visited.
What lured them? The flowers produce specific volatile compounds with a distinctly fruity signature. "The beetles were attracted to the flowers by compounds that smell like rockmelon," explains Dr. Ryan Phillips, senior author and researcher at La Trobe's Department of Ecological, Animal and Plant Sciences. This unlikely pairing—beetles and fruit-scented blooms—reflects something unexpected: the candlestick banksia's pollination strategy echoes beetle-pollination patterns found in tropical plants of South America and Asia, suggesting convergent evolution across continents and centuries.
The significance extends beyond botanical curiosity. Many of the remaining candlestick banksia populations are now confined to small habitat fragments scattered across suburban and agricultural landscapes around Perth. If these beetle pollinators cannot survive in fragmented or urbanized environments, the tree's reproduction could be compromised. Dr. Wawrzyczek, now working in conservation, highlights the urgency: "Our work raises the question of whether these beetle pollinators are persisting in remnant habitat and if their potential loss adversely affects reproduction of the banksia, which is a dominant tree species in banksia woodland."
The research, published in the journal Plant Biology and conducted in collaboration with seven institutions including the University of Western Australia and Royal Botanic Gardens Victoria, used a combination of floral visitor surveys, camera traps, video recordings, and careful quantification of insect pollen loads. Yet mysteries remain. Scientists are still investigating whether beetles are drawn to the rockmelon-scented flowers through learned behavior or through innate, genetically wired attraction—a question that could reshape how we understand plant-pollinator relationships.
For conservation planners, the path forward is clear. Dr. Phillips says the next step is understanding "if the pollinating beetles can live in fragmented or urbanized landscapes and how to best facilitate their persistence." The research highlights a humbling truth: even in familiar landscapes, unexpected pollination strategies await discovery, particularly among plants that conduct their intimate affairs under cover of darkness. In protecting the unseen nocturnal rituals of Perth's beetles, we protect the future of its banksia woodlands.