Further to all this, I came cross some old data to show why I am not as worried about tracheal or sampling more bees as some think I should be. Here are results from Fall 1997, a year in which I sampled but never treated: Yard Positive Negative Total Tested Infestation level Railway 3 47 50 High Jahns 2 48 50 Medium Meglis 10 40 50 Medium & Low Falks 6 44 50 Medium Kievers 1 49 50 Low Dixons 4 46 50 Low There are 6 more yards, but the above are actually some of the worst, and 4 of the next 6 were zeros. The other two were a ten and a one. I'm too lazy to type them in. The point is that I was unable to see any visible differences between yards, or losses that I could attribute to the higher tracheal levels in some yards. We have varroa now, and did not then. I understand the effects are somewhat additive, so am lowering my threshold of concern a bit. Nonetheless, the current results are so much better than these that I am not too worried. allen http://www.internode.net/honeybee/diary/