Peter,

Thought this might help.
The proventriculus filters the nectar and removes debris such as pollen 
grains and the fungal spores that cause foul brood.  A valve at the bottom 
of the proventriculus prevents the filtered nectar from entering the bee’s 
digestive system, but allows the debris removed from the nectar to pass 
into the bee’s alimentary canal and into the intestines where it is first 
stored then later voided from the rectum. 

Testing the speed and efficiency in which an introduced contaminate passes 
thru the digestive system might be the best method for determining which 
lines have a well developed proventriculus.   


THE R-VALUES OF HONEY: POLLEN COEFFICIENTS
http://www.nhb.org/download/research/rvalue.pdf


“The honeybee’s filtering process is rapid and effective (Snodgrass and 
Erickson, 1992). The bee sucks nectar into a slender tube that ends in the 
bee’s abdomen where it becomes an enlarged thin-walled sac called the 
honey stomach. This honey stomach is greatly distensible and can expand to 
hold large amounts of nectar. Once in the honey stomach, the nectar flows 
over the proventriculus that serves as a regulatory apparatus filtering 
and controlling the entrance of food into the bee’s stomach. The anterior
end of the proventriculus, called the honey stopper, projects into the 
bee’s honey stomach like the neck of a bottle. At its anterior end is an x-
shaped opening consisting of four, thick, triangular-shaped, muscle 
controlled lips. Nectar in the honey stomach is drawn back and forth into 
the funnel-shaped proventriculus. This process filters the nectar and 
removes debris such as pollen grains and the fungal spores that cause foul 
brood. The posterior end of the proventriculus extends into the anterior 
end of the ventriculus, the part of the bee’s alimentary canal (mid gut) 
where digestion and food absorption occurs. A valve at the bottom of the 
proventriculus prevents the filtered nectar from entering the bee’s 
digestive system, but allows the debris removed from the nectar to pass 
into the bee’s alimentary canal and into the intestines where it is first 
stored then later voided from the rectum. From time to time people get 
alarmed about a phenomenon referred to as “yellow rain” (Newman, 1984). 
When large numbers of bees forage on nectars that are laden with pollen, 
the rapid removal of those pollen grains from their honey stomachs and the 
resulting defecation by those swarms of bees can appear as “yellow rain” 
spots on leaves, cars, sidewalks, or buildings.

Todd and Vansell (1942) conducted many experiments to determine the 
efficiency of pollen removal from the nectar in a bee’s honey stomach, 
which was noted during earlier research by Whitcomb and Wilson (1929). 
Todd and Vansell goals included determination of the effectiveness of 
pollen removal from the honey stomach, the duration of the removal 
process, and the equality of pollen removal by the
filtering process of a bee’s honey stopper. In one experiment, honeybees 
in a caged laboratory hive were fed only diluted, unifloral star thistle 
(Centaurea sp.) honey that had been produced by other honeybees foraging 
in the wild…”

Best Wishes,
Joe

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