If they eat the wrong thing, bees cannot find their way home. Two new studies confirm that a group of widely used pesticides subtly affect the insects' behaviour, and may be partly to blame for their falling populations.
Neonicotinoid pesticides are used around the world to protect major crops like oilseed rape (canola). But studies have suggested that they are harmful to bees – they make them more susceptible to gut parasites, for example.
In field tests of 75 colonies of buff-tailed bumblebees (Bombus terrestris), David Goulson at the University of Stirling, UK, and colleagues found that food treated with realistic levels of one neonicotinoid, called imidacloprid, dramatically slows their spring population growth.
Dosed colonies also produced 85 per cent fewer queens than control colonies – a major problem as only the new queens survive the winter to found new colonies the following year.