Flying out into the snow is well explained by John Free in his book Honeybee
Biology. In short he says unlike a fly that has a gryroscope balance the bee
uses whats called dorsal light reflex. This means that in order to keep a
proper flying attitude they need more light falling on the upper part of the
eyes then the lower. If more light is coming from below then above the bee
will turn over an crash. Heinrich called back yesterday to answer his
question. He took off the cover and let bees run up out of the center of the
cluster and found they too where full of wastes. So why do some bees fly out
into cold and others not. Maybe its the older bees that cant hold it that
fly out. I had the temp. on those bees wrong. The abdomen was 16 C, probably
warm enough to function, the thorax was 30 C.