Leaf-Biting Bees

By Brayden Yin

Hungry for pollen? Just bite some leaves.

Three species of bumblebee bite the leaves of plants that they want pollen from. To study these unique bees, a chemical ecologist named Consuelo de Moraes set up experiments with mustard and tomato plants. When hungry bees want pollen, they bite the leaves of the plant, and send them a message to go into bloom. 

For some reason, plants bitten by bumblebees bloom days or even weeks before the unbitten ones. The bumblebees start colonies in the spring, and they need to feed their young. Pollen is a valuable source of protein for the bumblebee larvae. To test how leaf biting and pollen shortages were related, the researchers did a test with caged bees. First the researchers didn’t feed the bees pollen for three days. Then, they trapped bees with plants that didn’t bloom at all. The bees were more likely to start poking holes in the leaves than to go in a bee group drinking from flowers.

Tomato plants that were punctured five to ten times bloomed thirty days earlier than the unbitten ones, on average. The time that it took for the plants to bloom varied from plant to plant. For example, the black mustard plant bloomed sixteen days earlier, on average.

Scientists on the lab roof tried to simulate the bee bites with forceps and razors. There was only a slight difference in time for the black mustard and no change for the tomatoes. This proved that there must be something special in the bumblebee’s bite. Some bees don’t drink nectar through the flowers but instead bite the leaves to drink. “I can imagine that hungry bees unable to find flowers might try biting leaves in desperation,” Dave Goulson at the University of Sussex in England says. Flower biting might have turned into leaf biting, or the other way around. 

With leaf biting in mind, now is a good time to watch some bees. 


Bumblebees may bite leaves to spur plant blooming

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