Lost a Hive in North Texas and Another One is All But Gone

[donm]

Sadly, the girls are gone.  I don't understand it.  They had 3-full, medium supers of honey, a significant amount of pollen in the brood chamber and they are gone.  I have another hive that is all but wiped out.  They had 4-full supers.  They cleaned out the one right above the brood chamber and stayed there.  They didn't move up into the full supers.  I opened them up to put some mega bee on them today.  I certainly did not expect what I found. 2009 was my first year as a beekeeper in North Texas.  I kept bees in Houston for several years and never lost a hive during the winter.  Does anyone out there have any ideas why they did not move up into the full supers.  I removed the queen excluders this past fall?   

[Finski]

Does anyone out there have any ideas why they did not move up into the full supers.  I removed the queen excluders this past fall?   

The hive is too big to the cluster. They have started to winter in some point. Perhaps they have brood which they do not leave. It has been a several days very cold snap . In they site food have finished and bees have died very quickly.

Reasons 

- cold hive
- too much room, bees wate energy
- too much ventilation
- no insulation
- mesh floor ?
- windy place

That has happened to me over 30 years ago when I had non insulated hives.
but not after insulating.

4 medium boxes has 50 kg honey. It is awfully much for winter . Have you extracted at all?

[Finski]

If it is cold, the cluster has difficulties to move over the gap between two boxes.
A big cluster makes a bridge over that gap because of its size.