Have you never had only one of your colonies rob the others? I have. It took me a while to figure out why one colony had three times more honey than the others.
The first time I had a huge persistent mite load in one colony I sugar rolled a number of bees entering the hive. Guess what? Quite a few were carrying varroa. I thought foragers didn’t have any? Hmmmmm
Absolutely but how do particular colonies farm mites when they have been vaped repeatedly?
I’m not convinced my one hive in question is farming mites.
The only time I've had a colony rob another, in my apiary, was a nuc that was robbed by all the other colonies ... probably my fault - I had used a queen cell as a 'back up' when a colony made queen cells - the queen cell in the nuc produced a queen but she didn't get mated - by the time I figured out what was going on there was lots of honey in the nuc but not enough bees ... a recipe for robbing and it happened .. just two days and the nuc was stripped. I think once it starts any colony in the immediate vicinity will notice and they all pile in.
However, if the colony you had consistent high varroa loads (and only that one colony) surely, once your 'mite bomb' was stripped (and it does not take long) are you saying that this one colony specialised in finding other varroa ridden weak colonies to rob every few days ? Are all these mite bombs dead outs ?
On the balance of probabilities it would seem unlikely, when your other colonies were not robbing the same weak colonies - or perhaps they were but the mites were selective about the bees they jumped on... How prevalent is bees robbing bees at any distance from their own hive ? They are opportunists but they are only going to rob colonies that they can easily overcome or which are dead outs.
I don't know - perhaps nobody knows - but I do know that some colonies seem to manage varroa better than others and possibly it is the ones that don't that become attractive to the mites ?
Of course foragers carry mites and the likelihood is that they pick up mites from other bees - but testing returning foragers is only half the story - you would have to test those leaving as well, as they may be carrying the same mites when they leave ...
Too many variables to be conclusive and whilst the mite bomb theory has some circumstantial evidence in its favour - it's in no way conclusive. Possibly, your one colony was a mite farm ... even with vaping, if large numbers of mites in that colony were phoretic (I know .. they are no longer classed as phoretic) then there could be enough between vapes for them to breed exponentially ... more so if that colony was not good at dealing with them ?
Who knows ? But ... if you have a colony that has high infestation levels ... consistently, it's not one I would like to breed from ...
