>>You can prove smaller cells reduces varroa, but why is this so? Maybe because there's less room, period.

I read somewhere that bees vibrate the comb for communication.  (I've seen queens vibrate the comb, when feeling threatened, and this causes the surrounding bees to freeze.)  Supposedly, plastic foundation differs from wax in the vibratory response.  Vibrations may be used during scouts' dances to inform others of nectar sources...

I don't know if bees sense varroa, or pupae in trouble, by smell or vibratory response or otherwise.  Perhaps the smaller cells fine-tune the vibratory response?  Dennis has a picture of bee-bitten varroa in his TBHs on his website.  Something helps bees focus defensively on the mites.  Dennis reported seeing more damaged varroa on the hive bottom in the fall when the brood is in the lower, smaller cell comb.

I think bees need to remove varroa-infected pupae when the mites are still immature.  I've observed bees dragging out damaged young bees where the bee doing the removing had a light-colored (semi-mature) mite on their body.  I think semi-mature mites can jump from a damaged bee to the removing bee and return to the hive.

Waldemar

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