This paper is a bit technical, but reading through it, it sounds like there are two issues with insects flying at low temperatures: (1) the temperature where the muscles can begin to “shiver”; and (2) the temperature where the muscles can produce enough power to fly. Cold muscles can do low-power things like moving the legs around slowly, but they can’t “buzz” the wings for flight, and if they are too cold, they can’t even shiver. Once the insect is warm enough to start shivering, it can warm up the wing muscles enough to get them to a temperature where they can produce enough power to fly. There’s evidently a lot of variation in the minimum shivering temperature – honeybees lose the ability to shiver and lapse into a coma at around 10 degrees C (about 50 F), while certain cold-adapted moths can shiver all the way down to the freezing point.

I’ve wondered about this, particularly when talking about bees and wasps. Is there something particular to the flight muscles that requires high temperatures? Or is it the insect metabolism in general? The scurrying you mention about (when bringing insects into your house) seems to indicate the latter. But I thought I’ve read that bees also vibrate their wings before take-off, in order to warm up that part of their body.

I wish I could give myself more energy just by cranking up the thermostat.