From Cosmos Magazine:
Researchers at the Los Alamos National Laboratory in New Mexico, USA, said they trained honeybees to stick out their proboscis – the tube they use to feed on nectar – when they smell explosives in anything from cars and roadside bombs to belts similar to those used by suicide bombers.
“Scientists have long marveled at the honey bee’s phenomenal sense of smell, which rivals that of dogs,” said Tim Haarmann, who led the research, dubbed the Stealthy Insect Sensor Project. “But previous attempts to harness and understand this ability were scientifically unproven. With more knowledge, our team thought we could make use of this ability.”
Using Pavlovian training techniques in which bees were exposed to the odour of explosives followed by a sugar water reward, researchers said they had trained bees to recognise substances ranging from dynamite and C-4 plastic explosives to the Howitzer propellant grains used in improvised explosive devices in Iraq.