Excerpts from a recent article
>The ability of Varroa destructor to reproduce in the African honey
>bee Apis mellifera scutellata was studied. In addition, the effects
>of space within the brood cell and short brood develop-mental time
>on mite reproduction, was investigated using A. m. scutellata cells
>parasitised by a A. m. capensis worker pseudo-clone.
>
>In A. m. scutellata worker cells Varroa produced 0.9 fertilised
>females per mother mite which is the same as found in susceptible
>European honey bees, but greater than the 0.4 produced in cells
>containing the pseudo-clone.
>
>Low mite reproductive success in cells containing pseudo-clone was
>mainly as a result of increased mite mortality. This was caused by
>male protonymphs and some mothers becoming trapped in the upper part
>of the cell due to the pseudo-clone being 8% larger than their host
>and not due to their short developmental time.
>
>Although reproduction of Varroa sp. is affected by the space between
>the develop-ing bee and cell wall, reducing cell sizes as a mite
>control method will probably fail to be effective since the bees are
>likely to respond by rearing correspondingly smaller bees
>
>Therefore, mite populations in South African A. m. scutellata and A.
>m. capensis honey bees are expected to increase to levels observed
>in Europe and USA.


Comment:
This study was done in Africa. The scuts had infestation rates
similar to European bees, despite their smaller size.  He says:

>mite populations in AHB [Africanized American honeybees] fluctuate
>during the year but their numbers rarely exceed several thousand
>while mite populations in both A. m. scutellata and A. m. capensis
>colonies have been reported to regularly exceed 10 000 (Allsopp,
>1998; Allsopp et al., 1999; Allsopp, 2000).

This is because, while scuts are smaller, there is still ample room
for mites to reproduce. In the case where a bee is too large for the
cell, as when Capes invade Scuts, there is a reduction of mite
reproduction. Of course, the infestation by Cape pseudo-queens wrecks
the hive.

It would appear that mite levels are reduced in AHB due to *some
other factor* other than small cell size. Furthermore, this
"resistance" seemed to weaken as they moved into the more temperate,
humid areas, which points to a very strong environmental component.

ref:

Reproduction of Varroa destructor in South African honey bees:
does cell space influence Varroa male survivorship?

Stephen J. MARTIN , Per KRYGER
Apidologie 33 (2002) 51-61



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Peter Borst <[log in to unmask]>