Apiguard works by killing the mites(fairly obvious, that). Most of those hanging on the workers will be killed off early on, hopefully, and then the apiguard is there to kill mites emerging from cells as the bees hatch.
There may well be some that survive and dive into a cell a few days(?) after the treament starts. Those will then be safe to breed until they emerge (and are hopefully 'mopped up' by the continued treatment). Mites are probably more vulnerable when recently emerged and can be killed before they are completely developed sexually)
So you should understand the futility of doing mite counts while the treatment is on-going. Initially a large drop (mites on adults and those emerging), then mainly those emerging from hatched cells (about a steady 10%ish) and finally a 'mopping-up' exercise to get the ones missed earlier. Mind you, it may not (probably won't) work to the theory - depending on temperatures, any excess ventilation, where and how the packs are positioned, rate of removal from the tray by the bees and probably several other factors. We know it is not 100% effective.
Not sure what you mean by 'out-laying' the mites. More larvae, fewer mites per pupating larva, but more adults damaged (albeit less so than multiple mites per cell). Can't win the war with varroah at present, only the battles.
Regards, RAB
Its little wonder we have colonies collapsing with this many varoa. Having said that my carnolian queen is very prolific in laying I hope she can out lay the varoa
