Hungry bumblebees make the flowers bloom

The bumblebee's diet consists of sweet nectar and protein-rich pollen. But sometimes flowers are scarce among plants. Then hungry bumblebees whirl around among the green leaves without any flowers to pollinate.

Insect researchers in Swiss Zurich observed a strange behavior in these bumblebees. They use their tongue and trunk to make large holes in the leaves

The researchers did an experiment with hops colonies that had not been allowed to eat pollen for a while and placed them among young tomato and blackberry plants.

The hungry bumblebees bit holes in the leaves and that behavior caused the plants to start blooming up to a month earlier compared to the plants that were not visited by bumblebees.

Bumblebees, on the other hand, had the pollen to eat did not exhibit the same behavior, which indicates that the behavior occurs only when they are in need of flowers, the researchers have published their discovery in this week's Science. 

- What a quiet study! It shows that the bumblebees can affect flowering, says Lina Herbertsson, an insect researcher at Lund University.

The experiment also had a group of plants where the researchers, with the help of a razor blade, caused the same mechanical damage to the leaves as the bumblebees did. Those plants also began to flower earlier than usual, but not as early as those that were bitten by hops.

The presence of the bumblebees thus does something more with the plants. If they inject, or suck something out, the researchers don't know yet.

- There is no logic in how this works, bumblebees have the ability to learn some cause-and-effect relationships, but the chewed plants did not start flowering until between five and 50 days after chewing. It's a long time for a bumblebee that only lives for a few weeks, says Lina Herbertsson.

This is not the first time a study has shown that the interaction between hops and the plants they pollinate is complex. Previously, a group of Israeli scientists have shown that the humming of the bumblebees causes the flowers to produce extra sweet nectar.

 - When the bumblebee growl near the flowers, the petals begin to vibrate at a certain frequency and in just a few minutes the amount of sugar in the nectar of the flowers increased, says Lina Herbertsson.