Possible links between diesel fumes and collapsing honey bee colonies are being investigated by scientists.
A University of Southampton study will investigate whether tiny particles from diesel engines could be affecting bees' brains and their navigation.
The three-year study will look into whether it is one of the factors affecting bee numbers.
Colony collapse disorder has hit large numbers of hives in Europe and North America in recent years.
Biologists, nanotechnology researchers and ecologists at the university will test the behaviour and neurological changes in honey bees when they are exposed to diesel nanoparticles.
Ecologist Professor Guy Poppy said: "Diesel road-traffic is increasing in the UK and research from the US has shown that nanoparticles found in its fumes can be detrimental to the brains of animals when they are exposed to large doses.
"We want to find out if bees are affected in the same way - and answer the question of why bees aren't finding their way back to the hive when they leave to find food," he added.
Chemical ecologist Dr Robbie Girling, said: "The diesel fumes may have a dual affect in that they may be mopping up flower smells in the air, making it harder for the bees to find their food sources."
The collapse of bee populations has been recorded around the world although extensive research has yet to identify the cause of the decline.
Bees are estimated to contribute £430m a year to the UK alone, by pollinating crops and producing honey, the researchers said.