According to a study, bumblebees use an amazing technique to fend off attacks from Asian hornets. According to this, the insects that belong to the bees fall to the ground when they are attacked by the invasive species. The dark bumblebee (Bombus terrestris), which is common in Europe, can either free itself directly from the hornet's grip or use its stinger to ward off the hornet (Vespa velutina), as the researchers write in the journal "Communications Biology".
Unlike honey bees, which are relatively defenseless against attacks by predatory insects from Southeast Asia, bumblebees' defense is almost always successful, according to a statement from the University of Exeter. Researchers from the universities of Vigo and Santiago de Compostela were also involved in the study.
"Asian hornets prey on a wide range of insects, including honeybees, but little is known about their impact on other pollinators," said Thomas O'Shea-Weller from the Environment and Sustainability Institute at the University of Exeter.
Negative effect on bumblebee populations
Despite the successful defense against attacks, the presence of the Asian hornet, which is also spreading in Germany, has a negative effect on bumblebee populations, as the study also shows. Accordingly, bumblebee colonies grow more slowly when there are many Asian hornets in the area. The exact reason for this is not yet known, said O'Shea-Weller. However, it stands to reason that the hornets reduced the success of the bumblebee colonies, for example because defending against attacks requires a lot of energy.
For the study, the researchers placed twelve commercially bred bumblebee colonies at twelve locations in the Spanish province of Pontevedra in places with varying densities of Asian hornet presence. The bumblebee nests were weighed every two days to determine growth.