Hi,
 
The business of Mellifera not recognising Varroa as a threat is, I
believe, not yet fully understood. We know of course that Varroa is a
*new* threat to Mellifera (one century at the most out of millions of
years) but its still hard to understand why they don't recognise it --
maybe they think it's a Braula.
 
There have been experiment using Cerana with Mellifera to groom the
Mellifera (Cerana groom each other), but with no effect, it seems that
there are probably some behavioural signals that Mellifera just don't
have. Mellifera is also familiar with Braula and seems happy to co-exist
with this essentially harmless creature -- there is even a suggestion
of a possible symbiotic relationship as bees seem not to kill them even
when they move between the mandibles to 'steal' food. It may be that
there is a hygiene activity here (like with cleaner fishes?). Mellifera
plus Cerana experiments continue in the hopes that Mellifera will
eventually 'get the idea'.
 
Sorry if my mail is out of sequence -- I get the daily digest from bee-l
rather than individual letters as CompuServe charge a minimum per letter
for mail received from the Internet.
 
Bye for now, Gordon.