David, I think this bee looks like it might be a older bee, it appears rather shiny looking, young bees are more fuzzy looking, like Michael said. Bees die basically because their wings wear out and become too frayed to fly anymore.
The virus Michael is talking about is a direct result of the varroa mite. In all honesty, check the ground around your hives and see if you see alot of bees fumbling around with bad looking wings (or even stubs of wings for that matter), see if you can ascertain the age of the bees. If they are younger looking bees, you surely have a bad mite problem.
You should perform a sticky board trap test to see where you are at with mite levels, high, low, none. Leave the sticky boards in the hives for 3 days, that is 72 hours.
This is a pretty good measurement of mite levels. The ratio for determining is mite level count goes as follows.
Insert sticky boards for 72 hours.
After approximately 72 hours, count the mites (all of them on each board, do not only count one square and multiply the mites by the number of squares, that is not accurate enough)
Divide the number of mites that you see by the number of hours the boards have been in the traps
This will give you the avearge daily natural mite drop count.
If you have mites, then you must treat, or face the consequence of eventual colony collapse. And believe me. It happens. I had 9 colonies collapse last year, a direct result of mite overload. My fault. I was not attentive enough, nor knew enough about the devastation that high mite levels can do to a hive.
It is important to do the sticky board 3 days to give an accurate mite count.
Good luck, you have some work ahead of you, but you must look after your girls if you want them to look after you. Have a wonderful day, best of this life. Cindi
If you want to get more information about the prorated mite detection, there is a site that explains it deeper.http://www.mitegone.com/