In a discovery that could rewrite the story of how plants and insects communicate, Harvard researchers have found that cycads—ancient seed plants dating back hundreds of millions of years—attract their beetle pollinators by heating up their reproductive cones and emitting infrared radiation. This newly uncovered pollination signal, invisible to the human eye but crucial to the beetles, may be among the oldest forms of plant-animal communication on Earth, predating the colorful displays and perfumes of flowering plants by eons.
Published on December 11, 2025, in the journal Science, the study reveals that cycads, often called "living fossils," employ a sophisticated thermal signaling system to guide their exclusive beetle partners, such as Rhopalotria furfuracea, from male to female cones. According to Science, this is the first time infrared radiation has been identified as a pollination cue—a breakthrough that could reshape our understanding of plant-pollinator evolution.
“This is basically adding a new dimension of information that plants and animals are using to communicate that we didn’t know about before,” lead author Wendy Valencia-Montoya, Ph.D., a junior fellow at the Harvard Society of Fellows, told Phys.org. “We knew of scent and we knew of color, but we didn’t know that infrared could act as a pollination signal.”
The research, led by Valencia-Montoya in collaboration with Professor Nicholas Bellono and Professor Naomi Pierce at Harvard, was largely conducted at the Montgomery Botanical Center in Florida, a shift necessitated by pandemic travel restrictions. But the roots of the project stretch back more than a dozen years, to Valencia-Montoya’s undergraduate days studying cycads in Colombia and her fieldwork in the Peruvian Amazon. There, she marveled at how the tiny beetles seemed to find the plants with uncanny precision in the dense rainforest. “You see one cone, and the next day you just see all the beetles there. I just found that quite magical,” she told National Geographic.
Cycads themselves are relics of a distant past, appearing around 275 million years ago and reaching peak diversity during the Jurassic period, roughly 150 million years ago. These stout-trunked, feather-leaved plants superficially resemble palms or ferns but are more closely related to conifers. Today, only about 300 species survive, most of them endangered. What sets cycads apart is their ancient partnership with beetle pollinators, which has been documented in fossils dating back at least 200 million years.
To understand how cycads and beetles communicate, Valencia-Montoya and her colleagues focused on Zamia furfuracea, a Mexican cycad commonly known as the "cardboard palm," and its dedicated pollinator, the long-snouted weevil Rhopalotria furfuracea. The relationship is a textbook example of “push-pull pollination”: male cones produce pollen and heat up, attracting beetles with a blend of warmth, scent, and humidity. After feeding and mating in the male cones, the beetles are repelled by overwhelming signals and migrate to the female cones, which begin to warm up about three hours after the males cool down. This orchestrated sequence ensures that pollen is transferred efficiently from male to female plants.
Thermal imaging revealed that male cycad cones can heat up to 46 degrees Fahrenheit above ambient temperature, while other species can surpass even that. According to National Geographic, some cycads in the wild have been observed to warm themselves by more than 25 degrees. The researchers marked beetles with ultraviolet fluorescent dyes and tracked their nighttime movements, confirming that the insects were drawn to the warmest parts of the cones—first the males, then the females. “This was one of the early compelling pieces of evidence that this is probably related to pollination,” Professor Bellono explained to Phys.org. “Male and female plants were actually heating in a circadian-controlled manner—and we could see it locks with the beetle movement.”
But how could beetles sense this heat? The answer lay in the fine structure of their antennae. Using electron microscopy, electrophysiology, and gene expression analysis, the team discovered that the beetle antenna tips are equipped with specialized thermosensitive organs packed with neurons expressing the protein TRPA1. This protein, as National Geographic notes, is also used by snakes and mosquitoes to detect infrared radiation from warm-blooded prey. The beetles’ thermal sensors are finely tuned to the specific temperature ranges produced by their host cycads, and behavioral experiments using 3-D printed cycad models confirmed that beetles preferred heated cones, even when only infrared light—not direct warmth—was accessible.
“Nature seems to just recycle the same old molecular players and use them again,” Valencia-Montoya remarked to National Geographic, reflecting on the evolutionary convergence between beetles, snakes, and mosquitoes. This is the first time scientists have identified the molecular and cellular basis for infrared sensing in any beetle species, a finding that could have broader implications for understanding how other insects interact with their environments.
The implications extend beyond cycads and beetles. The study challenges the long-held assumption that plant heating is merely a byproduct of metabolism or a means to volatilize scents. Instead, it suggests that heat—and the infrared radiation it produces—was likely one of the earliest plant signals used to attract animal pollinators, predating the evolution of color vision in bees and butterflies. As Valencia-Montoya told Phys.org, “Long before petals and perfume, plants and beetles found each other by feeling the warmth.”
Interestingly, as flowering plants rose to dominance over the last 70 million years, visual cues like color became more important, and many pollinators evolved more sophisticated vision. Beetles, with their relatively poor color perception, may have relied on heat signals for millions of years, while bees and butterflies developed trichromatic and tetrachromatic vision to navigate the vibrant world of angiosperms. This evolutionary shift is reflected in modern plant diversity: the more color diversity in a seed plant family, the less likely those plants are to heat themselves up to attract pollinators.
The cycads’ thermal signaling strategy may also help explain their persistence through mass extinctions and dramatic environmental changes. Their nocturnal beetle pollinators, which lay eggs in the cones, are intimately tied to the plants’ life cycles. “So without beetles, there’s no plants, and without plants, there’s no beetles,” Valencia-Montoya explained to National Geographic. The study’s findings open the door to exploring whether other ancient plant-insect relationships are governed by similarly hidden sensory cues, such as heat, humidity, or even sound.
For now, the discovery of infrared radiation as a pollination signal in cycads offers a rare glimpse into a world of communication that has been unfolding, unseen, for hundreds of millions of years. As Professor Bellono put it, “All the sensory cues that have been recognized very fast are the ones that we can perceive. But the ones that are hidden may be as important.”
With only about 300 cycad species left—most of them endangered—understanding these ancient relationships is more than a scientific curiosity. It’s a reminder that the survival of some of Earth’s oldest plants may depend on a delicate, invisible dialogue with their insect partners, a dialogue we are only just beginning to understand.
