Asked by: Chris Kirk, by email
Bluebottles fly quite fast for their size, but in absolute terms the speed is only around 11km/h – slower than a honeybee and much slower than most birds. But the main thing that protects them from damage is their very low mass. Kinetic energy is equal to half the mass times the velocity squared. For a fly that weighs less than 100mg, this comes to less than half a millijoule of energy. This is the same as the energy an adult man would have at a practically immobile speed of 3mm per second.