Have you seen the Jamie Ellis presentation on YouTube (National Honey Show)? He didn't seem to think it was such a big deal...yet I was beside myself when I was counting varroa and I saw what looked like a SHB larva crawling across the sticky board (3 pairs of legs...what looked like horns at the posterior end).....then I remembered I was looking down a microscope at 20* magnification!
I'm not sure what it was but it was transparent, not like a waxmoth larva. I wish I had more time to do more microscopy...there is so much more crawling around on the bottom of a beehive than most people ever see.
I've seen Keith Delaplane talk on this subject a long time ago. I'm not sure that I followed his point at the time. I think you have to be ready to receive the message sometimes....and if you aren't ready to hear it (perhaps because of educational background or whatever reason) the message is lost. Yet, if you hear the same thing after studying some more, the penny drops and you see things in a new light. Does this make sense? Thats how I feel anyway.