chelsea and leigh ann of maine ask:
do bumble bees really defy gravity by flying, and if so, what happens if they get caught in rain? do they just sink?
The Nerd responds: The mystery of how a bumblebee flies is interesting, but it has been somewhat overstated historically. What I mean by that is that this mystery has often been thought in terms of: "Ha! Ha! Science says that the bumblebee can't fly, but everyone knows it does!"
This is way overstating the situation. Science doesn't say that a bumblebee shouldn't be able to fly. On the other hand, science still can't say for sure how it happens (even though recent research has gone a long way). This isn't such a shocking thing. As I sit here typing I can think of several things science recognizes but cannot fully explain: How trees draw water up their trunk a hundred or more feet into the air to their leaves, for instance. Or how birds navigate on their long migrations.
The supposed contradiction of a bumblebee's flight seems to have originated in the 1800's. One story has that a naturalist was explaining the dimensions of this bee to an engineer at a dinner party, and the engineer doing some quick calculations concluded that the insect should not be able to fly. The naturalist thought that this proved that the mysteries of nature were beyond science and the story got so exagerated that people believed that science claimed to have proved the bee couldn't fly.
An example of the complex movement of insect flight
What this engineer, and no one for over 100 years, didn't realize was that bumblebees (and insects in general) do not fly like birds. In fact, modern flying insects may well have evolved from waterbugs that "swam" along the surface of water and slowly evolved their swimming motion so that they could start to "swim" through the air. And, indeed, the flight of insects is much more like swimming than the traditional rigid-winged lift-causing flight of birds and airplanes. Bumblebees actually roll and bend their wings in a way that roils the air to create a vortex along the edges of their wings that give them an extra lift that has gone undetected to science for a long time.
As to flying in the rain? Bumblebees will actually brave the rain more than many insects--probably for the same reason that their flight has so longed confused scientists: and that is that they are big enough to withstand some inclement weather that would knock smaller bugs out of the air. On the other hand, bumblebees have sense to stay home in a truly heavy downpour.