National Museum of Natural History Scientists Discover That Ancient Insects Perfected Their Plant Palates 165 Million Years Ago

The findings reveal that insects developed modern patterns of herbivory long before flowering plants flourished, upending a long-held hypothesis

Jack Tamisiea

March 3, 2025

Paleontologist Conrad Labandeira, the museum’s curator of fossil arthropods, collects fossils from a field site in South Africa. Labandeira studies plant fossils that preserve damage left behind by ancient insects. Robert Gastaldo

When plants took root on dry land more than 400 million years ago, they made themselves susceptible to hungry herbivores. Over the eons, a vast variety of creatures ranging from dinosaurs and mammoths to millipedes and slugs have evolved to eat leafy greens.

But none of these vegetarians has been as vexing for plants as insects. It has been estimated that up to half of the world’s insects are herbivores. This group includes ants, bees, beetles, butterflies, cicadas, grasshoppers and moths, just to name a few. Collectively, these insects consume more plant material than all vertebrate herbivores. Insects also play a central role in pollination.

Insects and their arthropod ancestors have fed on plant material for hundreds of millions of years. But researchers have long proposed that today’s diversity of herbivorous insect feeding styles developed when flowering plants, or angiosperms, evolved during the early Cretaceous period between 125 and 100 million years ago.

However, a patchy fossil record has made it difficult to determine exactly when insects began feeding on plants like they do today according to Conrad Labandeira, the curator of fossil arthropods at the National Museum of Natural History. “I’ve always wondered how far back this modern style of herbivory goes, but nobody had ever looked at that issue,” said Labandeira, who was recently named a fellow of the American Association for the Advancement of Science for his work studying ancient insect-plant interactions.

To fill in the gaps in the fossil record, Labandeira and his colleagues recently analyzed more than a hundred sprawling datasets of insect-damaged plant specimens. Their findings, published last month in the journal Proceedings of the National Academy of Sciences USA, reveal that the insect herbivory seen today originated 60 million years earlier than previously thought.

The key to the findings was determining how ancient insects ate their meals. According to Labandeira, insects leave distinct damage types on the plants they eat. These damage types are valuable clues for understanding insect-plant interactions and are used to sort herbivorous insects into eleven different feeding groups.

Each of these feeding groups leaves distinctive damage on a plant. For example, hole-feeding insects chew holes into plants while margin-feeders nibble along the edge of a leaf. Mining insects burrow within plant tissues and create winding tunnels and blotches while skeletonizing insects eat away at the leaf until only a network of veins remain. Galling insects create swollen, tumor-like growths called galls while ovipositing insects insert their eggs directly into the leaf tissue, creating lesions surrounded by scar tissue.

When damaged leaves fossilize, these telltale traces are also preserved. Labandeira and his colleagues examined numerous insect damage types from 134 plant assemblages spanning the last 305 million years of Earth’s history.

The team paid special attention to three well-documented fossil sites that record a transition in terrestrial plant communities between the late Middle Jurassic and the latest Early Cretaceous. For example, the older two sites (Northeastern China’s Daohugou and Dawangzhangzi plant assemblages) are dominated by cone-producing gymnosperms like cycads, ginkgos, conifers and several extinct plant lineages. By contrast, the youngest of the three sites (Nebraska’s Rose Creek plant assemblage) is rich flowering angiosperm plants.

"It’s like two different worlds of herbivory.”

— Conrad Labandeira, curator of fossil arthropods at the National Museum of Natural History

Once the team crafted its database of insect damaged plants, they used statistical analyses to determine if there was a pattern to the herbivory. They discovered that modern insect damage appears to have emerged in the Middle Jurassic, long before the rise of flowering plants. “It’s like two different worlds of herbivory,” Labandeira said. “From the Middle Jurassic on, it looks like the herbivore communities are much more structured than anything we see before.”

The findings reveal that insects largely utilized similar feeding strategies even as the plants around them changed. The damage the researchers observed on Jurassic conifers, for example, was similar to how more recent insects chewed through the leaves of flowering plants in the Cretaceous.

While the broader insect lineages themselves have not changed, the species of herbivorous insects that munched on cycads and conifers in the Jurassic are no longer around. But their feeding styles live on in modern insects. Labandeira compares it to a baseball team’s lineup. The positions like pitcher, shortstop and first baseman stay the same, but the players themselves swap out as they are traded or retire or, in the case of prehistoric insects, go extinct.

While the new findings help elucidate an important ecological milestone in Earth’s past, they also shed light on how the insect-plant dynamic may evolve in the future according to Lifang Xiao, a former postdoctoral researcher at the museum who is now affiliated with the Institute of Zoology at the Guangdong Academy of Science in China. “Insect herbivory research can help answer important questions that scientists are currently concerned with, especially regarding the origins of insect and plant biodiversity and its implications for ecosystems under future climate and environmental changes,” she said. [Liang Chen, a predoctoral researcher in Labandeira’s lab who is now at Capital Normal University in Beijing, also contributed to the project.]

According to Labandeira, future environmental changes may make certain insects even more ravenous. As atmospheric concentrations of greenhouse gases like carbon dioxide increase, it would decrease the amounts of important elements like nitrogen in plants that are essential for the metabolic health of insects. This would force insects to consume more plant material to reach the requisite amount of nitrogen in their diets.

The increased consumption would decrease available plant material, causing a domino effect on the rest of the terrestrial ecosystem. A delicate balance that has existed between herbivorous insects and their plant hosts for more than 160 million years could be disturbed.

Labandeira and his colleagues in China are now conducting further investigations into those three critical plant assemblages spanning the gymnosperm to angiosperm transition. “The next step is to really dig into the weeds and find if there is something particularly special about angiosperm foliage that insects prefer,” Labandeira said.

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Jack Tamisiea is a Science Communications Specialist at the Smithsonian's National Museum of Natural History. In addition to covering all things natural history for the museum's blog, Smithsonian Voices, he tracks media coverage and coordinates filming activities for the museum's Office of Communications and Public Affairs. Jack recently completed his masters in science writing at Johns Hopkins University and his writing has appeared in the New York Times, Scientific American, National Geographic and other science-focused publications. In his free time, he loves exploring the outdoors with a sketchbook and camera. You can read more of Jack's work at https://jacktamisiea.com.