Scientists have been responsible for spreading a popular urban myth – that it should be physically impossible for bumble bees to fly. Of course, everybody knows that this is not true; we’ve all seen bees buzzing among the flowers, going about their business of collecting nectar and performing an essential pollination service.
So where did science go wrong?
The original hypothesis suggested bumblebees should be incapable of flight, because they don’t have the capacity (in terms of wing size or beats per second) to achieve flight with the degree of wing loading necessary. Calculations variously attributed to a number of European scientists are based upon aerodynamic studies of aircraft. Of course, animal wings are infinitely more complex than anything developed by man! They provide both the lift and the propulsion (as in a helicopter) but in a much more sophisticated way. For instance, a fly’s wing confirmation is not only capable of rapid adjustment in flight, but the wings themselves are actually highly sophisticated sense organs. Check out this TED video for more on the aerodynamic attributes of flies.
For the technically minded, the original bee flight calculations assumed a simplified linear treatment of oscillating aerofoils. The method assumes small amplitude oscillations without flow separation and ignores the effect of dynamic stall, an airflow separation inducing a large vortex above the wing, which briefly produces several times the lift of the aerofoil in regular flight. More sophisticated aerodynamic analysis shows that the bumblebee can fly because its wings encounter dynamic stall in every oscillation cycle.
In fact, a bee’s wings act more like a helicopter’s blades, as do a humming bird’s wings, which beat in a figure-of-eight pattern. Hummingbirds’ main flight feathers slide as they flap, changing the shape and size of the wing and precisely controlling the lift their wings produce. Here’s some great video explaining how a humming bird flies.
Insects, birds and mammals (in the shape of bats) are the true masters of the air, although some fish (flying fish), amphibians (various flying frogs), reptiles (flying snakes) and mammals (flying squirrels) can also glide for periods.
So why do animals fly? Obviously, they do this to look for food and escape danger but there are also a number of other reasons, such as locating and attracting mates, and exploring for new places to live – dispersion and migration.
Wing shape is important in terms of the type of flight an insect or bird can undertake on a regular basis. For instance, birds’ wings tend to come in four distinct types (although some species have intermediate forms):
- elliptical wings – short and round, and highly manoeuvrable as in song birds and hawks;
- high-speed wings – pointed wings and rapid wing beats as in a peregrine falcon;
- high-aspect-ratio wings – used by kestrels for hovering and seabirds like the albatross for long-distance gliding; and
- soaring wings with slots – favoured by larger inland birds like vultures and storks.
These different shapes correspond to different trade-offs between beneficial characteristics, such as speed, low energy use, and manoeuvrability, and vary according to the habits of the individual species.
Fun flight facts
- Today, the largest dragonfly is Megaloprepus caerulatus, with a wingspan of 19cm. However, fossil records show prehistoric dragonflies such as Meganeuropsis permiana had a wingspan of some 75 cm and an estimated body weight of over 450g, making it about the size of a crow.
- The Monarch butterfly is known for its long-distance southward migration in North America to over-wintering grounds in Mexican pine forests. However, the Painted Lady butterfly is credited with the longest known journey, from North Africa to Iceland, a distance of 4,000 miles.
- Buzz, buzz: another common, yet incorrect, assumption about bumble bees is that the buzzing sound is caused by the beating of their wings. It actually results from the bee vibrating its flight muscles. Bumble bees must warm up their bodies to get airborne at low ambient temperatures and have been known to reach an internal thoracic temperature of 30°C using this method.
- True flies (Diptera) only have one pair of wings, although they have small balancing organs known as halteres, substituting for where the second pair of wings would be in other insects. These halteres vibrate with the wings, acting as mini gyroscopes, and sense changes of direction.