On August 21, 2017, a team of researchers from the University of Alabama used an unprecedented array of high-tech weather instruments to study how both the atmosphere and insects responded during the brief but profound darkness of a total solar eclipse.
Their study, recently published by the American Meteorological Society, marks the first fine-scale investigation of eclipse impacts on meteorology and insect behavior using multiple Doppler radars, mobile weather stations, and upper-air balloon soundings.
And what they found is as fascinating as it is bizarre: airborne insects, seemingly following a solar compass, suddenly dropped from the sky just before totality—then surged back upward once the Sun returned.
Nature’s Great Disruptor: Totality
Eclipses have long been known to cool the ground and calm the air temporarily. But what happens in those surreal minutes when the world goes dark midday? In the 168 seconds of totality, the atmosphere responded with swift cooling and shifting winds—triggers that appeared to send insects spiraling into a behavioral tailspin.
Temperature near the ground dropped by 7 to 9°F, while wind speeds slowed by nearly 7 mph at the surface. Yet higher up, above 300 feet, the air remained mostly unchanged. This created a shallow layer of cool, stable air hugging the surface—enough to shut down vertical mixing and disorient the flying insects that rely on solar and thermal cues to navigate.
Radar as an Entomologist’s Eyes
Using three mobile Doppler on Wheels (DOW) radars, the research team mapped insect flight patterns in unprecedented detail. Before the eclipse, radar reflectivity showed insects flying at altitudes of 650–1,000 feet (200–300 meters) above the surface, oriented southeast and moving with the wind.
Then came totality.
As the Sun slipped behind the Moon, insect layers collapsed. Radar data showed insects rapidly descending, with the strongest signals vanishing almost entirely at higher altitudes. During the darkest moments, reflectivity dropped by 10 dB—an approximate 90% decline. The insects had landed.
Once sunlight returned, the swarm reanimated. Within minutes, insects began climbing again—some reaching speeds of 2.2 mph (1 m/s) upward—and reoriented themselves toward their pre-eclipse headings, albeit more sluggishly.
Why the Sudden Drop?
It’s not temperature alone. Despite the cooling at ground level, the air aloft stayed within 0.4°F (0.2°C) of pre-eclipse levels. That rules out thermally driven changes as the cause of the abrupt insect descent.
Instead, researchers believe the insects were responding to light—or more precisely, the lack of it. Many insects use the Sun as a compass. When it disappears, they may lose orientation, cease flight, and drop from the sky. This eclipse, with complete totality and minimal atmospheric interference, provided the perfect test bed.
“This was the first time we’ve had the resolution—both temporally and spatially—to see this level of behavioral detail in real time,” the study notes. Previous efforts lacked either full totality, used coarse radar updates, or occurred under cloud cover that muddied the results.
An Eclipse as a Controlled Experiment
Scientists often bemoan the chaos of nature’s laboratory. Tornadoes don’t follow scripts. Thunderstorms don’t wait for sensors. But an eclipse? You can schedule that down to the second.
The 2017 eclipse offered a unique, nearly lab-like experiment. Researchers deployed their gear in flat, treeless plains under crystal-clear skies in Wyoming—eliminating typical confounders like terrain, vegetation, or cloud cover. In doing so, they created what might be the cleanest real-world eclipse experiment ever conducted.
From Eclipse to Ecosystems
The implications go far beyond entomology. This study suggests that total solar eclipses can exert ecosystem-level impacts by temporarily disrupting the biosphere-atmosphere interaction. If insects rely so strongly on sunlight for orientation, the effects of totality could ripple through pollination, predator-prey dynamics, and migratory behavior.
This research breaks new ground not just in what we see, but how we see it—using weather radars, typically reserved for storm tracking, to track the pulse of life in the sky.