Last night I got into a discussion about the myth that "science says bumblebees can't fly". Unfortunately the discussion derailed into a minor train crash from that point on, but my lesson is also that this myth still lives.
And amazingly, even the most basic research would bring about evidence against this myth! Yes, "amazingly" was sarcastic.
A repetition of the myth, from an apparently respectable media
Possible origin of the myth
The Straight Dope
A little on the harm this myth is causing
Yet more on the subject and how some people refuse to use their brain for thinking
Anyway, here's a quick checklist if you hear someone make a claim like this: If the claim (e.g. "bumblebees can't fly") does not correspond to observable facts (e.g. bumblebees flying), then either 1) the claim is an old theory which has now been disproven or 2) the claim is false. The claim could be false in general but true in specific scenarios or under specific conditions. For instance the claim could be that if only a specific set of conditions are considered then something specific holds true (e.g. "according to present knowledge of aerodynamics we cannot explain how a bumblebee can fly").
Return to that last example and count how many modifiers to the claim there are...
EDIT: Of course there's at least a third option: 3) The observation is wrong :-)