Ko Mochizuki from the University of Tokyo has made an exciting discovery: Vincetoxicum nakaianum, a dogbane species native to Japan that he and his team first described just a year ago, mimics the odor of ants that have been attacked by spiders. This clever strategy allows the plant to attract flies that feed on these injured ants, ultimately leading to the pollination of its flowers. This marks the first known instance of a plant mimicking ant smells, showcasing that floral mimicry is more varied than we previously thought. The findings are published in the journal Current Biology.
The enticing aroma of warm, freshly baked bread lures many customers into shops, and grass flies are no exception; they are similarly drawn to the scent of injured ants, which they consider a meal. While searching for these vulnerable ants, the flies inadvertently pollinate the flowers they visit. Given that ants are one of the most common insects, and that various invertebrate species have evolved to mimic them, it’s plausible that plants could also develop similar mimicry. Yet, this had never been documented until now.
“I was engaged in another research project,” Mochizuki explains, “and initially collected this species as a reference. By chance, I noticed chloropid flies hovering around its flowers at the Koishikawa Botanical Gardens and realized the flowers might be mimicking dead insects.”
This insight stemmed from a series of unrelated experiences. His participation in a training course in 2019 helped him identify the fly species flocking to the flowers, and he was familiar with past research indicating that plants pollinated by chloropid flies emit scents resembling those of insects.
Encouraged by his hunch, Mochizuki began observing the flower visitors and analyzing the scents released by both the flowers and various insects. He discovered that the aroma of ants under spider attack was the closest match. However, his hypothesis about ant mimicry was tenuous, as there were no documented instances of chloropid flies—or similar species—specifically targeting ants hurt by predators like spiders. Turning to social media for unconventional evidence, Mochizuki found numerous amateur naturalists documenting observations of ants attacked by spiders, which in turn attracted kleptoparasitic flies. This bolstered his confidence to test the hypothesis and determine whether chloropid flies were indeed more attracted to the scent of spider-attacked ants than to other odors.
“Seeing those flies on the flowers was a moment of inspiration,” Mochizuki recalls, “as my hypothesis began to take form. This experience taught me that unexpected discoveries often stem from a blend of preparation and serendipity.”
Speaking of preparation, Mochizuki is already gearing up for his next project. “I plan to investigate the evolutionary background of ant mimicry by comparing the pollination systems, evolutionary history, and genetic makeup of Vincetoxicum nakaianum and its relatives. Additionally, since this study implies that many forms of floral mimicry may be currently undiscovered, I intend to explore other species within Vincetoxicum and in unrelated plant groups to find more potential examples of mimicry.”
Summary: Ko Mochizuki of the University of Tokyo has found that the plant Vincetoxicum nakaianum imitates the smell of injured ants attacked by spiders to attract pollinating flies. This groundbreaking discovery highlights a new form of floral mimicry and suggests many more examples may exist in nature, prompting further research into plant-insect interactions.
