>Yep. I've seen many examples of multiple invasion of cells by maternal
>mites, which must allow for cross fertilisation between the progeny.

These maternal mites are most likely "sisters". Even with multiple invasions
the females are going to be close relatives most of the time. Maternal mites
carry all of the DNA so offspring are going to be clones of the parent. Once
a hive is infested with mites I would guess that the population is going to
tend to be close relatives.

So inbreeding is still the case. I was told last week by someone doing DNA
research on the mites that they have found only a few strains. I think only
two strains in the United States??