An inconspicuous, thornlike insect is changing how scientists examine survival as global temperatures rise.
Researchers from St. Louis University's Fowler-Finn lab studied how heat affects the survival and reproduction of Missouri treehoppers. Study co-author and SLU biology professor Kasey Fowler-Finn said their resilience could give more insight into how insects are adapting to curb population loss and total extinction.
"This is more of a story of resilience and predicting what species and populations are going to be resilient and which are not," said Fowler-Finn. "I think the story really shifts our perspective from looking just at do animals survive temperatures to can they thrive? Can they actually reproduce at those temperatures?"
Fowler-Finn and the team gathered juvenile Enchenopa binotata treehoppers and then divided them into two separate temperature environments. As temperatures increased, juvenile insects were more likely to succumb. However, the heat gave an added bonus to the adults – their fertility got an extra boost.
"What we found here was that while warmer temperatures reduced survival, they actually increased your ability to produce eggs," Fowler-Finn said. "So that was a little bit surprising."
The heat has also affected how treehoppers "sing." The whalelike sound can only be heard using specialized equipment. Treehoppers also struggle to regulate their body temperature: The insects have even learned to become more strategic in their own habitats to stay cooler.
"Anything over about 36 degrees Celsius is physiologically stressful for these animals," Fowler-Finn said. "At that point they'll jump off the branch that they're on in hopes of finding a better branch that's maybe a little bit cooler. It turns out the reason why they only do this when it's really, really hot is that the trees that they live on are so thermally variable."
Insects including treehoppers play a vital role in biodiversity and overall ecosystem function. Insects represent more than 70% of species of animals on Earth. Fowler-Finn said their decline has significant consequences including bird population loss.
"[Insects] do all sorts of things like decompose things," Fowler-Finn said. "They pollinate. They can get rid of natural predators. They can be natural predators. Once you start taking those out it's kind of like Jenga. You start destabilizing the system and at some point it's going to collapse."
Treehoppers are roughly a half-centimeter long, or half the size of a single pea. Their small frames are mostly black with two yellow spots on their backs. Their pronotum, which sticks out from its head, is reminiscent of a wizard's pointy hat. The insect typically spends its single year of life on a woody shrub.
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