According to BBC Science Focus, there are three main factors that limit the altitude that flying insect species can reach. These are air density, temperature, and oxygen availability.
All three factors are related to the fact that the gravitational force of Earth weakens as altitude increases, causing air molecules to disperse. With the same volume of air, fewer molecules make the air “thinner” or less dense.
Bumblebees can move their wings to maintain flight in thin air.
As air density decreases, flying at high altitudes becomes increasingly challenging because the number of air molecules that an insect’s wings push against is reduced. Like humans, insects need oxygen to survive, but at altitudes above 6 km, the oxygen concentration is less than 50% of that at sea level, making it more difficult to maintain wingbeats.
Finally, fewer molecules mean that the heat generated by the random collisions of molecules is also reduced. Temperature varies in complex ways with altitude, and some layers of air are warmer than others, but between Earth and an altitude of 10 km, the temperature gradually decreases to below -50 degrees Celsius.
Despite these challenges, some insect species have developed strategies that allow them to fly at high altitudes. According to a scientific study from 2014, bumblebees living at an altitude of 3.25 km above sea level use different wingbeats when ascending to higher altitudes, adjusting their wing movements to maintain flight in thin air.
In laboratory settings, bumblebees can even fly in chambers that simulate air density and oxygen concentration at altitudes of 9 km—higher than the summit of Mount Everest (Everest is the highest mountain in the world, standing at 8,849 m). In reality, the extreme cold at such heights would incapacitate the flight muscles of bumblebees.
Bumblebees refer to species within the genus Bombus in the family Apidae. They are primarily distributed in the Northern Hemisphere, with some species also found in South America.
