Dry Sugar

Do the bees store dry sugar or do they just consume it as needed?

I think they just use it as needed and a couple of my colonies are visibly hauling it out and dumping it. Cost of doing business because it has definately kept some alive.

I believe it is like an emergency trail bar.

They mostly use it as needed.
I had a hive that stored a small amount in a few comb cells, though

The cluster will be in physical contact with the sugar. There is usually a thin layer of semi-liquid sugar at the boundary of the cluster, which I think they use as needed.

As a general rule, they use it as they need it. But if warm weather comes and there is still a dearth they may start storing it.