Another option for detecting consumption is to spike the diet with an  
indicator dye.  I did that years ago with termites - since they have  alkaline 
guts, chose a dye that would change color under alkaline  conditions.  Have 
to be careful about toxicity, but I found dyes that had  no lethal effect.  
 
Now, since termites are light colored, you could see the color in the gut  
without dissection.  For bees, it would still speed things up - just yank  
the gut and look for color.
 
Jerry

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