Science: The Flight of Insects

As a flying machine, a mosquito is not efficient, but since its weight is low it gets 450 million miles per gallon of nectar, which it uses as fuel. In the Scientific Monthly, Professor Brian Hocking of the University of Alberta tells about his experiments with the flight of insects. He puts his subjects on a “flight mill”: a delicate arm that turns round and round, propelled by a buzzing insect cemented to its tip. A photoelectric cell counts the revolutions, and from its records the insect’s speed, power and mileage can be computed.

The insects easiest to study in this way are mosquitoes, bees, flies, etc. Dr. Hocking puts one of them on the mill and makes it fly until it is exhausted, which means that its nectar tank is empty. Then he refuels it (a tricky business) with a measured amount of nectar and starts it flying again. When it stops he knows how far it has flown on the fuel that he gave it. Modifications of this experiment enable Dr. Hocking to figure the most economical cruising speed of each insect. Mosquitoes fly most efficiently at 2 ½ m.p.h. Bees cruising at 7 m.p.h. get 4,000,000 miles per gallon of nectar; flies get 2,000.000 miles per gallon at 10 m.p.h.

The French scientist, A. Magnan, studied bumblebees for years and came to the conclusion that they should not be able to fly at all. Dr. Hocking is not much more impressed by the flying abilities of his pets. They are good at control and maneuverability, but they waste fuel. The maximum fuel efficiency of a mosquito is only .03%. Most insects fly much slower than they appear to. Top speed for horseflies is 14.8 m.p.h., far below the speed of horses. Dragonflies are insect speed champs, flying at more than 40 m.p.h.

The distance that insects can fly depends largely on the help that they get from the wind. If they stay in the air for long periods, as many of them can, they will be carried long distances even if their own speed is low. A few insects do fairly well without any wind. Dr. Hocking calculates that desert locusts can fly 217 miles at 5.6 m.p.h. Best of all are monarch butterflies, which can fly 650 miles at 6.2 m.p.h. They can stay in the air so long that a good tail wind would help them across the Atlantic without refueling.