Hmmm. There's stuff in there that makes me wonder...
Initially, the comment about using purple because bees can see into the ultra-violet. Just because they can see in ultra-violet means nothing in respect of how they respond to purple as opposed to, say, green or blue. I don't get that at all.
I also wonder how many mites actually leave the hive on bees thereby enabling the system to count them. Clearly some do, but I look for mites on every foraging bee I see and I've never seen one. I've seen them on bees in swarms, but never on a forager. So are they common enough to give a meaningful result? It makes me realise that there's a bit of the process I don't understand. If a forager carries a mite back to a hive, how does the mite make it into a cell to reproduce? Does it climb off and wander around to find the brood? Generally I thought foragers didn't really get involved with the brood directly.
The idea of segregating incoming bees that have mites is an interesting one and I can see how that might be done, but will it genuinely help? Surely all it takes is the failure to detect a single mite and the hive is "infected" though you may not know about it until weeks later?
James