Thanks for reposting this paper Stan, I somehow missed its original
posting.  What a well-done study, with surprising findings.

Interesting points are the apparent accumulation of IMI in bumblebee brains
over 3 days.  Unfortunately, there was no longer-term data to see whether
it reached an asymptote (where dietary exposure reached equilibrium with
detoxification).  I'd sure like to see comparable data for honey bees,
since a number of studies suggest that neonics affect bumblebees more
strongly than they do honey bees.

The authors state: "Therefore, any toxicity to adult bees is likely limited
to neuronal dysfunction rather than acute brain damage."  This brings us
back to the question as to what is actually happening in the neuron? Is it
a compensatory mechanism that then leaves the neuron damaged?

The difference results found between exposure to IMI or chlorpyrifos are of
interest.  The end result of either is excessive stimulation of the neuron,
but by different mechanisms (IMI binds to the receptor, holding it open;
chlorpyrifos suppresses normal breakdown of the natural transmitter ACh by
the enzyme AChE).

The action by IMI thus appears to exert a longer-term effect, meaning that
if the insect isn't killed, it may still remain neurologically damaged.

Again, it has in recent years become quite apparent that the impact of
neonics on bumble and solitary bees should be of concern.  As far as honey
bees, perhaps less so, since they turn over their population during
foraging season roughly every 42 days, compared to once a season for the
other bees.  So much stronger overall effect on other bee populations.

Take home:  in bumblebees, IMI does indeed appear to accumulate in the
brain, at least for the first three days, and exhibit adverse effects.  One
would suspect that something similar happens in the honey bee brain,
although Suchail's data seem contrary.

I'll post comments on the Belzunces paper separately, after I've digested
it.

-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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