Figure 7.

Clothianidin, imidacloprid and thiamethoxam elicit biphasic dose-response curves in leafcutter bees. Leafcutter bees were provided untreated honey-water or honey- water containing 50 µg/µl, 2.5 µg/µl, 125 ng/µl, 6.25 ng/µl, 312.5 pg/µl, 15.6 pg/µl, 0.78 pg/µl and 0.039 pg/µl acetamiprid, imidacloprid, thiamethoxam and clothianidin for 24 hours in cage trials. The cages were then provided honey-water ab libitum for 14 days. As a conservative estimate, we used the highest consumption rate or 34 µl for all LD₅₀ calculations. Cages were assessed daily for the number of bees dead in a cage, the number of bees exhibiting symptoms, the type of symptoms, and the duration or outcome of symptoms. The average values and standard errors are provided for each concentration applied. The data were collected from 6 independent experiments and expressed as proportion of bees dead. The four neonicotinoids are identified as follows: acetamiprid (blue triangle), clothianidin (red diamond), imidacloprid (green square) and thiamethoxam (purple circle).