Falling atmospheric pressure is often associated with bad weather such as thunderstorms and can be accompanied by different combinations of high wind speeds, rainfall, rapid changes in temperature, and solar radiation, all conditions that can result in high mortality in small insects.
Many of them, moths included, have adapted to predict - to some degree - upcoming weather associated with decreasing barometric pressure. This evolutionary modification has long been documented for large migrating insects that take advantage of the convective storms that precede typical cold fronts by enhancing their flight activity.
For small and short-lived insects, detecting atmospheric pressure changes and adjusting their behaviour accordingly (when to migrate, when to breed and lay eggs etc), expresses their ingeniously adaptive abilities.
Antique tiger moth (c. 1920s), vintage barometer, 2019