Nicotine-like pesticides are likely to cause long-term damage to wild honey bee populations even though they might initially appear to be harmless, a new study has shown.
The bees counteract the immediate impact of neonicotinoid pesticides by producing more female workers at the expense of male drones, whose job is to breed.
With fewer males available for mating with queens, the long-term survival of the colony is put at risk, the research suggests.
The findings may help explain apparently conflicting evidence about the effect of the controversial chemicals on bee populations.
While work involving the artificial exposure of honey bees to the pesticides has indicated that the chemicals impair the insects' ability to forage for pollen and nectar, by and large this evidence has not been supported by wild bee studies.
The new research suggests that in the wild, the bees themselves help to cover up the evidence. Even though pesticide exposure led to "significant excess mortality" of free-ranging bees, colonies compensated for the loss by altering their demographics.
"The most exposed colonies modified the timing of their reproductive investment, delaying drone brood production in favour of increased worker brood production," the researchers concluded.
Because of the possible risk to bees, in 2013 the European Union banned the use of three neonicotinoids on flowering crops for two years.
But the move was highly controversial and opposed by the UK government, which was nevertheless obliged to enforce the ban.
The study led by Dr Mickael Henry, from the French INRA agricultural institute in Avignon, was published in the journal Proceedings of the Royal Society B.
