Bumblebees Can Spot Which Flowers Have the Best Pollen Before Landing

Not all flowers are created equal and now, it turns out that bumblebees can tell the difference. Scientists have found that these insects can connect differences in pollen quality with floral features, like petal color, so that they only land on flowers that offer the best rewards.

Bees don't ingest pollen while foraging on flower. That's why researchers have long wondered how these insects could form associative relationships between what a flower looks like and the quality of its pollen. In order to find out, the scientists examined bumblebee forages under controlled conditions.

"There is still very little known about how bees decide which flowers to visit for pollen collection," said Natalie Hempel de Ibarra, one of the researchers, in a news release. "Easily learning floral features based on pollen rewards, without needing any nectar rewards, is a fast and effective way to recognize those flower species which bees have previously experienced to be the best ones."

The researchers manipulated the quality of pollen offered to the bees under controlled conditions by diluting the samples. Then, the scientists examined which pollen the bees preferred to collect, and if they could differentiate quality before landing by smell and sight of the pollen alone. In all, the researchers presented the bees with four different colored discs containing stronger and less diluted pollen.

"Bees need to be able to select flowers providing the most nutritious food for rearing their young," said Elizabeth Nicholls, one of the researchers. "Since bumblebees don't eat pollen when foraging, it was unclear if or how they might be able to assess differences in quality. Here we've shown that they are able to detect differences in pollen, even before landing, which means they may be able to tell, just from the color of the petals, which flowers are worth visiting."

The findings are published in the Journal of Experimental Biology.