For rearing their young, bees need to be able to select flowers providing the most nutritious pollen and they know it even before landing on the flower simply by looking at the colour of the petals, says a study.
As bees do not ingest pollen unlike nectar while foraging on flowers, it has been unclear whether they are able to form associative relationships between what a flower looks like and the quality of its pollen.
The study used bumblebee foragers housed under controlled conditions to test whether they do learn about flowers during pollen collection.
Bumblebees can individually assess pollen samples and discriminate between them during collection, quickly forming preferences for a particular type of pollen, the findings showed.
"Here we have shown that they are able to detect differences in pollen, even before landing, which means they may be able to tell, just from the colour of the petals, which flowers are worth visiting," said Elizabeth Nicholls from University of Sussex in Britain.
The experiments involved manipulating the quality of pollen offered to the bees by diluting the samples.
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The researchers examined what they preferred to collect, if they could differentiate quality before landing by only letting the bees smell and see the pollen rather than probing it.
They then presented the bees with four different coloured discs containing stronger and less diluted pollen to record preferences and change of preferences over time.
The study appeared in the Journal of Experimental Biology.