Why do bees land below front of hive to die (full of pollen)?

[Hethen57]

I have two hives which were made from splits last July (using different queen stock), they survived the winter and seem strong.  However, both (located on opposite ends of my hive row) seem to have a high number of bees that collect pollen on nice days and land short of the hive (full of pollen) and walk around on the ground or the hive stand, congregate, and die over night.  Probably 50-100+ do this on nice Spring days, but my other hives may only have a dozen or less doing this.  Are these just old bees on their last day of flying?  Could it be that the later summer split resulted in more bees ready to die as soon as the weather got nice?  Maybe they just get too cold to fly back into the hive?  Does anyone else notice this type of activity.  I hate to lose all the bees, but I have tried putting some back on the landing porch and they just seem to be moving to slow to try to save themselves.  The temps are 45 to 55, but as the sun goes down the temp drops down to high 30's.

[D Coates]

I've noticed exactly that.  When it's the beginning of the Spring here I've seen it happen at my hives at pretty much those exact temperatures.  I've picked some of them up and warmed them in my hands and they're pepped and ready to go.  I've also found that this occurs more with the hives I have in the shade.  Long story short I believe it's that they get too cold working during marginal weather and die due to lack of warmth

[Hethen57]

That's kind of what I was thinking, they must land hoping to soak up enough heat to get back to the hive, but it's just too cold to do so, plus the sun moves down behind the hive and then they are in the shade...next time I am going to do an experment and run an extension cord out to the hives and put a small heat lamp 3 or 4 feet above them to see if it gives them enough energy to get back in.  My 3 carnie hives don't do it, but my 2 hives with hybrid queens do.

[gardeningfireman]

I had the same thing happen to my two hives last fall. I lost probably around 500 bees just in front of the hives, all fully loaded with pollen. It lasted about two or three days and then stopped. My neighbor had his lawn sprayed the evening before the die-off. I attributed it to pesticide poisoning, but it may have been coincidence :?
ps. both hives made it through the winter! :-D

[AllenF]

If they are the end hives on the row, do you think it could be from bees drifting?   They get to the end hive and say "that's not my house" and the cold gets them before they get in.