> This adding up of theoretical accumulated exposure
> is thereby inherently invalid, as bees can metabolize
> imidaclopird.  Suchail et all (2003, ("Metabolism
> of Imidacloprid in Apis mellifera" Pest Mnmgt Science;
> 60, 291-296)) found that the metabolism half-life of
> imidacloprid in honey bees was 4.5 to 5 hours with no
> detectable residues found in bees 24 hours after exposure

Below is from the abstract for the Suchail paper on chronic
toxicity.  Judge for yourself whether "adding up accumulated
exposure is inherently invalid":

Environmental Toxicology and Chemistry

DISCREPANCY BETWEEN ACUTE AND CHRONIC TOXICITY INDUCED BY IMIDACLOPRID AND 
ITS METABOLITES IN APIS MELLIFERA

Séverine Suchail, David Guez, and Luc P. Belzunces

 ...To test chronic toxicity, worker bees were fed sucrose solutions 
containing 0.1, 1, and 10 μg/L of imidacloprid and its metabolites for 10 d. 
Fifty percent mortality was reached at approximately 8 d. Hence, considering 
that sucrose syrup was consumed at the mean rate of 12 μl/d and per bee, 
after an 8-d period the cumulated doses were approximately 0.01, 0.1, and 1 
ng/bee (0.1, 1, and 10 μg/kg). Thus, all tested compounds were toxic at 
doses 30 to 3,000 (olefin), 60 to 6,000 (imidacloprid), 200 to 20,000 
(5-OH-imidacloprid), and >1,000 to 100,000 (remaining metabolites) times 
lower than those required to produce the same effect in acute intoxication 
studies. For all products tested, bee mortality was induced only 72 h after 
the onset of intoxication. 

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