There has been much discussion about the effect of high voltage lines on
all sorts of organisms, humans and  farm animals as well as bees, but no
hard evidence of a direct damage mechanism. Because of the fast fall off
in field strength with distance it is perhaps unlikely that there are
direct magnetic or electric field effects.

However the possibility of indirect effects are perhaps more possible.

There has been some research carried out in the UK (I think at Bristol
Univ.-forgive me if I've got the wrong institution), on the effects of
the electrostatic fields under power lines in concentrating polution
particles.

The idea is that if a power line is situated downwind from e.g. a major
roadway, then the field would concentrate the pollution particles to the
extent that any "air breathing " organism in the vicinity would get an
enriched pollution ingestion. Presumably this would affect bees as much
as any other animal, and might lead to a general "feeling of swarminess"

Alan Riach
Edinburgh, Scotland