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According to some source or other (I forget which now) it is theoretically impossible for bumblebees to fly by virtue of their size/bulk/aerodynamic properties. Is this old adage apocraphyal or true? And if its true, how come they do fly?

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The Wikipedia article on bumble bees covers this pretty well: – Mitchell Mar 31 '11 at 15:11
This myth is well known in GB, practically unknown in Germany. (at least before Internet and Wiki spread such stories) For that reason I doubt Prantls role (as written in Wiki) in spreading that myth. – Georg Mar 31 '11 at 17:28
I really feel like saying "Nothing is impossible with God." However, a bumblebee flying has absolutely nothing to do with its drag since it isn't a fixed-wing "aircraft". – Arlen Beiler Aug 8 '12 at 1:00
up vote 5 down vote accepted

This story may have originated with August Magnan and André Sainte-Laguë. In the forward to his book Le vol des insectes, August Magnan wrote

Tout d'abord poussé par ce qui se fait en aviation, j'ai appliqué aux insectes les lois de la résistance de l'air, et je suis arrivé avec M. Sainte-Laguë a cette conclusion que leur vol est impossible.

First, prompted by what is done in aviation, I applied the laws of air resistance to insects, and with M. Sainte-Laguë came to the conclusion that their flight is impossible.

(my translation ... please correct if it's wrong).

He is talking about insects, and not specifically bumblebees.

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No it's an urban myth. It's impossible for them to fly using a very simple and inappropriate model of wing behaviour - possibly closer to say that bumble bees can't glide like albatrosses

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The ironic thing is that this answer, since it doesn't give any meaningful description of the sorts of mistakes that were made in the flawed flight analysis, is probably itself simply an accepted doctrine - a regurgitation of a myth that happens to be true. – Mark Eichenlaub Mar 31 '11 at 17:38
@MArk, I suppose at some point it's an urban myth that there is an urban myth that bees can't fly ! – Martin Beckett Mar 31 '11 at 17:42

Insect flight is different than bird flight. With insects, the rapidly moving wings, which do a figure 8 sort of motion, generates a vortex tube over the wings. This vortex by Bernoulli principle has less pressure, which permits the larger air pressure underneath to lift the animal up. If one is trying to understand insect flight according to the mechanics of bird or aircraft flight you are then pounding a square peg into a round hole, which makes you conclude bees can’t fly.

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I would just like to add something here.

These answers are great but I might have another answer. At first it was indeed a mystery how these insects were capable of flying, but thanks to high speed recordings they found something which investigators didn't concider. The wing motion has a sort of dubble lift feature. By twisting her wings over at the end of each downstroke, the upward momentum is never lost. basically, this means that even when the wings are going upwards, the wings provide upward lift.

(this also explains why bumblebees are so massive, they need a lot of muscle to get at the needed (Ca.) 300 flaps a minute)

I hope this was a complete answer! Cheers.

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Technically this was covered in the 'figure 8' of the other answers, but you explained it properly so posting a new answer is justified. +1 – Manishearth Apr 11 '12 at 17:14

The key is to correctly take scale into account. At insects scale, the Reynolds number is low, meaning that flow around an insect wing is mostly laminar, not turbulent. Moreover, kinematic viscosity of air is higher than water : at their scale, insects do not fly like birds, they litteraly swim in air.

More information:

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protected by Qmechanic Feb 4 '14 at 12:46

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