>Don't we all agree that neonics kill bees?

I think that we would all agree that any insecticide, at a high enough
dose, will kill bees.



> >However, it is also clear that all of the IMI metabolites that Suchail et
> al studied behaved just the same as the original IMI in that mortality
> began for each after 72 hours.


If you look carefully at her graphs, mortality began between 24 and 48 hrs.
 But it is not clear that such mortality was due to the insecticide.



> > It turns out that these metabolites are also AChR agonists, and some of
> them are much more powerful than the original compound (IMI)


Are you sure that you are reading the toxicity figures correctly?  Suchail
states that "only two metabolites  exhibited a toxicity close to that of
imidacloprid."  If the LD50 goes up, that means that it has *less*
toxicity, not more!

In any case those toxic metabolites were not detectable in the bee at 72
hrs.  The two that were detectable were far less toxic than the parent
compound.  Please correct me on this if I have misread Suchail's paper
(Table 1 in Suchail 2001).


> >...these are the ones still found in bee tissues at 72 hours.


Actually, according to Suchail's Plate 2, only two of the metabolites were
detectable at 72 hours (no detection, and only in the thorax and abdomen
(the abdomen is where they are held in the rectum), and only at 2% of the
original dose of IMI.  All the rest of the IMI and all other metabolites
were cleared by 72 hrs.  So at 72 hrs, Suchail's studies suggest that the
only metabolites left are those that are relatively nontoxic, and only at a
very low level.

Christina, I'm not trying to defend IMI.  I'm trying to understand its
dynamics in the bee.  I'm looking at the same studies as you, but we seem
to be seeing different things.  How can that be?


> > What they say is that IMI rapidly breaks down.  The breakdown
> products...the metabolites...do NOT.


Suchail's plate shows that only two relatively nontoxic metabolites remain
at 72 hrs, totaling perhaps 5% of the original labeled radioactivity.  I
readily grant that this 5% apparently continues to bind, although in the
thorax alone, ostensibly due to the preponderance of muscle tissue, some
still remains at 72 hours.

The other 95% of IMI and metabolites completely disappears.  Please correct
me if I'm misinterpreting, but doesn't that indicate that they are no
longer "irreversibly" binding?

> We both think this delayed mortality could be the result of stressed
neurons failing after days of trying to repair the membrane leaks....they
are under excess load and they fail sooner than they should, so the bee's
life is shortened.  But of course, this is just an educated guess.

Thank you for this!  That is the kind of information that I was hoping for.

So the question remains, How can bees consume canola, melon, or soy nectar
at about 1ppb and thrive, or as in Cresswell (2013) 125ppb and survive for
8 days.  But roughly 70% of Suchail's bees died by 10 days when fed IMI at
1ppb, and half died when fed only 0.1ppb--one one thousandth of the dose
fed by Cresswell?

I can understand your neuronal stress hypothesis, but I'm not seeing much
support for it in either published research or anecdotal reports.

Is anyone else on the List even following this?

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

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