When hives begin to overheat, large numbers of bees take to the outside of the box in order to get away from the combs (and thus improve ventilation), and cluster around the entrance and face of the hive. The key word being 'cluster'.
But here, the bees are NOT clustered, but are spread out as wide apart as possible across the face of the hive. I've seen this many times, usually associated with an absent queen: either when a virgin is out on her mating flight, or when the colony had lost their queen a day or two before.
I've always interpreted this behaviour as the bees sending out the widest possible stream of pheromone as a 'homing signal' to assist their queen to return home safely. Although it may well be seen at other times.
I watched one colony in particular (which I'd made queenless, prior to re-queening) set up this display (which I call a 'pheromone curtain') from dawn to dusk, every day for a week. Behaviour which I found quite pathetic. (in the sense of pathos: arousing pity from vulnerability - and NOT 'ridiculously inadequate')
I'm not a particularly emotional person, but to see these creatures trying so hard and for so long to regain their queen - well, I found it very moving indeed.
LJ