And - honeybee spiracles are surrounded by hairs which will block particles the size of Oxalic Acid microcrystals - ergo - Oxalic Acid never gets to enter the body of the honey bee. LJ, isn't the vapor a gas particle and that is too small to enter honeybee spiracles?
No - this is where the terminology being used isn't doing us any favours ...
A vapour IS a gas particle, certainly. When Oxalic Acid Dihydrate is heated, the first thing that happens is that it's water component (the Dihydrate) is boiled-off. Then, when the Oxalic Acid reaches it's sublimation temperature, it 'sublimates' - that is, it changes from a solid to a gaseous state, without going through a liquid phase. At that point in time, it IS a vapour, it IS a gas.
However, upon immediately leaving the heat source, it's temperature drops below it's sublimation temperature and the Oxalic Acid vapour reverts again to it's solid state, as individual molecules of solid OA. These immediately absorb moisture to again form the Dihydrate. These molecules of Oxalic Acid Dihydrate then clump together to form large (in molecular terms) microcrystals which become visible to the naked eye as a white 'smoke'. (The vapour itself is invisible)
All of this happens very quickly and within a short distance from the heated pan. Anyone who has experimented with various methods of vapourising OA will have observed that OA residue can often be found a few millimeters from the heat source, and certainly within a centimetre (say, half an inch).
What enters the beehive is NOT Oxalic Acid 'vapour', but rather a coarse dust of Oxalic Acid particles - which is why a) a good quality dust mask is all that is sufficient for respiratory protection, b) the dust particles never get to enter the body of the bee, and c) OA is unable to enter capped brood cells.
For as we know, the wax cap of brood cells is porous, which allows the developed bee to breath prior to it's emergence. But these pores are not large enough to allow the Oxalic Acid dust particles to enter. Formic Acid, on the other hand, forms a true vapour, and in this constant gaseous form it CAN enter brood cells via their porous caps - which is why Formic Acid can be used to treat those Varroa breeding on sealed brood, whereas Oxalic Acid cannot.
Perhaps it would be more accurate to describe the process as one of 'dusting' the bees with an aerosol of fine Oxalic Acid powder - with that aerosol having been generated by the action of vapourisation.
I am sure you would not intentionally do something to harm your honeybees but if you believe that OAV is the silver bullet against mites I can't see you pushing for research that would prove the harm. There isn't even any push to find out how it works. This is not logical to me.
Do we really NEED to know how it works ? Surely, all that's necessary is to know that it DOES work, and what doseage is safe.
As beekeepers we're often faced with decisions which have to be made. When faced with a hive infested with the Varroa mite, what choices of action are there ? Well, the first decision is whether to treat or not.
Now, I fully understand the thinking behind letting Nature work the problem out for itself. But - how many colonies of bees must die-out (and in the most miserable of ways) before a chance genetic mutation occurs which gives rise to a hygenic trait ? Should a breed of bee ever evolve with that stable genetic trait, then I'll be one of the first in the queue to buy such a queen.
But - in the abence of any better solution - I treat the mites instead. And so the next decision is "what to treat them with ?" I have looked carefully at the proprietary medications on offer, most of which have dreadful side-issues, and the actions of which many mites have quickly become immune. But not so Oxalic Acid: there are no apparent side-effects, and no evidence of any immunity having developed over two decades - so it would appear to be the best solution to the presenting problem currently on offer.
But ... just suppose you're right, and there is some small amount of harm (although not yet detected) which occurs to the bees ... ? As I see it, it's a situation not dissimilar to that faced by surgeons in the Napoleonic and First World Wars when presented with a patient who had contracted gangrene - the decision of course being whether or not to cut-off the limb in order to save the patient's life. But such decisions are easy (if uncomfortable) to make - for it becomes 'the lesser of two evils', as it is for me with regard to the health of honey-bees.