To date, there has been a paucity of evidence to support the contention that
field-realistic doses of Imidacloprid have any tangible effect on bees.  We
have some now, fresh out of embargo:

"Transient Exposure to Low Levels of Insecticide Affects Metabolic Networks
of Honeybee Larvae" in PLOS ONE.

http://dx.plos.org/10.1371/journal.pone.0068191

I've read it through all afternoon, and run it by several genetics wonks who
worked on the CCD Working Group, and we cannot find any obvious defect in
the paper.  The lack of a "dose response curve" is a drawback, but I suspect
others will provide some additional points on the graph when they attempt to
duplicate this.  The work is otherwise consistent with the tools and methods
known to be reliable in current genetics, no tricky bleeding edge
technologies, nothing too new, experimental, or unproven.

Reading as a beekeeper, the most significant paragraph seemed to be this:

"Concerted Effect on Glycolytic and Carbohydrate-metabolising genes

Balancing energy requirements under varying conditions necessitates
coordination of lipid and glucose-metabolising pathways. We found that genes
of the gluconeogenesis and glycolysis pathways have altered expression upon
imidacloprid exposure ...

While transcriptional changes of individual glycolytic genes have little
effect on glucose flux [41], several reports indicate that coordinated
changes in their expression levels occur as part of the physiological
response to starvation. Diminished expression of genes involved in
glycolysis has been observed in nutrient deprived Drosophila larvae [38] and
can be modulated by at least two different transcription factors: the
ecdysone receptor (EcR) and the estrogen-related receptor (dERR),
respectively [42], [43]. The Drosophila ERR is an essential regulator of
carbohydrate metabolism and a deficiency in mutant Drosophila larvae is
associated with diminished ATP and triacylglyceride (TAG) levels [43]."

Translation: Imidacloprid at 2 ppb messed with the bee's ability to utilize
sugars, not a good thing for a flying machine that runs on a diet of almost
pure sugars.

I'm not calling this a smoking gun, as I lack subject-matter expertise to
make a personal judgment here.  
But the barrel seems very warm to me, and there's a ringing in my ear.

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