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Janet · 16-05-2012, 12:52 PM posted to uk.rec.gardening

In article ,
says...

On Wed, 16 May 2012 00:37:13 +0100, Janet wrote:

I found a large sodden bumble bee struggling in the pond, fished it out
and put it in the sun to dry off. As it dried it kept wiping itself with
its middle legs; then I realised it was trying in vain to rub off small
live mites; it had a dozen or more crawling around on its back.

Are these varroa? Or do bumble bees get different mites?

Janet
They're not varroa, and yes they get different mites. The following is
a quote from http://www.bumblebeeconservation.org.uk/
"At least 15 genera of mites are associated with bumblebees. The most
familiar of these are mites of the genus Parasitellus which are very
often to be seen attached to the bodies of adult bumblebees,
particularly queens. These mites are only ever found in close
association with bumblebees. However, they do not feed directly upon
bumblebees, but are phoretic, using the adult bees for transport
between nests. This is a common phenomenon; mites have poor locomotory
abilities, but with their small size they can easily attach themselves
to larger organisms and so gain a free ride. Parasitellus species are
thought to feed upon wax, pollen, and other small arthropods that are
found in bumblebee nests. Only the deutonymph stage is phoretic,
colonising new nests by transferring from workers to flowers, and then
awaiting the arrival of another worker. The prevalence of Parasitellus
spp. is generally high - up to 80% of queens are affected. With this
level of prevalence at the beginning of the season, it is not
surprising that the vast majority of bumblebee nests become infested
by the end of their growth.

Because these mites do not feed upon the bees themselves, it is
debatable whether they have a negative impact. However, infestation
levels can be high. Up to 165 mite have been found on a single. It
seems inevitable that loads of this magnitude must hamper a queen's
ability to fly, and so her ability to find food, a mate and a
hibernation site. Try to help these queens by brushing off the mites."

Thanks very much.

Janet