[thedoc (OP)]

Ultraviolet Keating asked the Naked Scientists:

   If a japanese honey bee was as large as a person, could they fly? And how much heat could their wings produce?

What do you think?

[Bored chemist]

A bee the size of a person couldn't breathe.

[evan_au]

The largest known flying insect is a dragonfly from the Carboniferous period, with a wingspan of over half a meter.
It is thought that the oxygen content of the air was higher at that time.
See: http://en.wikipedia.org/wiki/Meganeura

The oxygen content can't get very much higher than the current 20%, as many substances become flammable when the oxygen content of air is above 50%.

But if we are talking wild speculation (like human-sized bees), consider what might be possible on a planet with a low gravity and a dense atmosphere. After all, dolphins are similar in size to a human, and they manage to stay afloat without too much in the way of wings.

[yellowcat]

The oxygen content can't get very much higher than the current 20%, as many substances become flammable when the oxygen content of air is above 50%.

In the Carboniferous period atmospheric oxygen peaked at 35%.

[alancalverd]

There's an old saying in aviation: "A piano will fly if you put a big enough engine on it". And a rocket-powered airplane can indeed fly with the tiniest of wings. The problem is to match the engine power to the wing loading. You need about 0.5 horsepower to lift 1 lb/sq ft of wing area. Man-powered aircraft have flown, with wing areas of 300 sq ft or more, because a human can generate up to 0.3 horsepower for a short time, but an insect the size of a human can't consume oxygen fast enough to match that - you need active lungs rather than passive spiracles. Whilst the power/weight ratio of an insect  is much higher than a human, the engine doesn't scale up to large sizes. Dogs and birds, however, have a much larger continuous power/weight ratio than humans thanks to their very large chests.