Hi:  There are several reasons for spotting in the hives.  One of the
reasons those of us in winter climates use upper entrances is to allow
the bees to fly during warm weather to cleanse themselves.  If the snow
buries the entrance, the bees can't get out.  I once found a hive that
had sagged shut.  I popped the lid up a bit and ended up covered from
head to foot with yellow rain.  Had on a good parka, had to send it to
the dry cleaners.
 
Hovever, there is one cause of spotty across the top bars that most of
you will never see, but one that we have seen all too often.  Exposure to
arsenic (usually from industrial sources like smelters) produces this
effect.  Arsenic poisoning often culminates in death of the colony during
the winter or early spring.
 
I wouldn't worry too much about this problem unless you have bees in
industrial regions or in those rare parts of the world where arsenic
levels are naturally high in groundwater.
 
Jerry Bromenshenk
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