> The average life expectancy for Varroa mites is about 50 days. http://gears.tucson.ars.ag.gov/rf/varroa/varroa.html
If only things were that simple.
From my 2002 study on which I based my monitoring, and which is available at http://www.honeybeeworld.com/diary/2...2.htm#mitedrop
.says: "The average life expectancy for Varroa mites is about 50 days".
says: "Female mites produced in the summer live 2 to 3 months, and those produced in the fall live 5 to 8 months. Without bees and brood, the mites can survive no more than 5 days. They can, however, live in a comb with sealed brood at 68 ° F for up to 30 days."
Personally, I'll go with the MAAREC info and consider the Tucson page to be a generalization for purposes of education. Also, remember that Tucson is Tucson. I have seen swarms in January near Tucson.
For my purposes, at the times of year that I do drops, 100 days works well. My recent comparison to alcohol wash this fall verified that number, to my mind, at least.
Mite drops are necessarily a very rough guide. Even alcohol wash does not account for the mites in brood.