BBC News
By Helen Briggs
image captionBrambles are a big source of food for honeybees
DNA detective work on honey has given a rare insight into the foraging habits of honeybees.
Scientists used genetic tools to discover which plants the pollinators visited in the countryside.
They compared this with a study from 1952, finding big shifts in the wildflowers available to bees.
In the 1950s, honeybees mainly gathered pollen and nectar from white clover. Today, there is not so much of this plant about, so they seek alternatives.
These include oilseed rape and Himalayan balsam.
And there are fears that honeybees and other vital pollinators are running out of food supplies as wildflowers disappear in hedgerows and fields.