Greetings
I have long wondered if rapid collapse of honey bee colonies infested
by varroa, and the so-called "colony collapse disorder" might not be
caused by a mass exodus of bees in an attempt to rid the colony of
parasites. This could in fact be a last ditch effort to save the queen
and enough bees to carry on. Obviously, it fails when carried out in
the fall, in northern climates but could have evolved in tropical bees
where a small nucleus could in fact regenerate the colony. This idea
was put into print in the latest American Bee Journal on page 104. See
"Dying outside for the good of the colony" by Jasna Kralj of
Ljubljana, Slovenia. She and Stefan Fuchs wrote about this last year
in Apidologie (how did I miss that article?)

Excerpt:

We suggest there could be a colony benefit from
not returning to the colony by the removal of
the pathogens. Smith-Trail discussed
the possibility for an adaptive sacrifice of one's
life for the benefit of kin in response to parasites
("suicide hypothesis"), and some examples
have since been described in butterflies
and aphids. In social insects, bumble bees infested
by conopid flies respond by behavioural
changes costly to the individual but beneficial
to the colony, but up to now there are no clear examples
that parasitized individuals might leave
the colonies in order to remove pathogens.

Parasitic Varroa destructor mites influence flight duration
and homing ability of infested Apis mellifera foragers
Jasna Kralj, Stefan Fuchs
Apidologie 37 (2006) 577–587

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