Researchers at the University of Cincinnati in the United States have identified an unexpected biological mechanism in insects: their internal clocks can be set not only by light and temperature, but also by cyclical changes in humidity. The study was published in the journal npj Biological Timing and Sleep and examined several insect species, including fruit flies, mosquitoes, kissing bugs and beetles.
In controlled lab experiments, the scientists exposed the insects to alternating humidity cycles without changing light or temperature. The insects adjusted their activity patterns to match the humidity rhythm. In some species, even after humidity was returned to a constant level, the insects continued to follow the previously established schedule.
Lead researcher Prof. Joshua Benoit said, "The insects use humidity as a biological cue like any other." The findings add humidity to the short list of environmental signals, known as zeitgebers, that can reset biological clocks, alongside light and temperature.
The team also studied insects with genetic defects in their biological clock mechanisms or humidity sensors. Those insects responded much more weakly to humidity cycles, suggesting the effect is built into biology rather than being random behavior. The researchers said the discovery could help explain how small insects avoid dehydration and choose the best times to be active, although humidity appeared weaker than light and temperature, and mosquitoes showed less consistent responses. The work also raises questions about whether humidity influences other animals, possibly including humans, though the researchers said that understanding is still at an early stage.
