Second article, A Common Pesticide Decreases Foraging Success and Survival in Honey Bees, (pdf).

Non-lethal exposure of honey bees to thiamethoxam (neonicotinoid systemic pesticide) causes high mortality due to homing failure at levels that could put a colony at risk of collapse. Simulated exposure events on free-ranging foragers labeled with an RFID tag suggest that homing is impaired by thiamethoxam intoxication. These experiments offer new insights into the consequences of common neonicotinoid pesticides used worldwide.

To make matters even worse, clothianidin is the breakdown product of thiamethoxam.