|MadSci Network: Biophysics|
I have read that bumblebees are not supposed to be able to fly because their body is too heavy when compared to the size of the wing. Perhaps this is why you have posted this question. Clearly they do fly and they follow the same laws of aerodynamics that all other flying bodies have to follow!
Any flying object has to overcome the resistances to motion, namely weight and drag. Bumblebees are bulky, but they are able to beat their wings at around 200 times per second. The wings twist and turn as they beat up and down allowing them lower resistance on the up-stroke. The twisting essentially maximises the forward thrust and lift to counter the drag and the weight of the bumblebee's body.
Bees have also improved flying efficiency by coupling their wings. Their hind wings have reduced in size and are joined to the fore wings by a row of hooks. This makes the two pairs of wings act like one and are therefore much easier to control. This allowed bees and other more advanced insects to take of advantage of the click mechanism.
In more primitive insects such as dragonflies, each stroke of the wing is triggered by an impulse from the central nervous system. However, the central nervous system in insects cannot fire impulses at 200 times a second. Dragonflies can only beat their wings at about 20-30 times a second compared to a thousand times in some flies.
In the click mechanism, the contraction of a muscle is stimulated by its own extension. If you have a pair of muscles working in tandem (i.e. The contraction of one extends the other and vice-versa), then you have a muscle system that can run somewhat independently of stimulation from the central nervous system.
The central nervous system still needs send impulses to keep the click mechanism going, but at a much slower rate. In brief the bee can fly because:
bee couples it wings to make them easier to control.
It beats its wings at 200 times per second using the click mechanism.
The wing is able to twist in flight to maximise flight efficiency.
I hope this answers your question. Flight is a very interesting subject in insects because it explains why they are so successful and, to a large extent, the way in which different insects evolved.
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