Giant bumblebees attack bees, but they have a secret weapon

Gigantic bumblebees are very aggressive and attack hives en masse: but bees have a secret weapon against bumblebee attacks.

It often happens that they are confused, but bees and bumblebees are two different animals. The former feed on pollen, and only the females have a stinger, which they use only when necessary. The latter instead are much larger, reaching 5 centimeters in length, and also more aggressive: when they have to attack, they can mobilize the entire colony, therefore 700 individuals. And above all, as if bees didn't already have the risk of extinction to worry about, they must also defend themselves from bumblebees, which hunt them down by attacking their hives.

But bees have learned to defend themselves, developing a secret weapon.

How bees defend themselves against giant bumblebees

There is one species of bumblebee in particular that is most aggressive, the "giant" bumblebee, the Vespa Soror, found in parts of Asia. When they attack a hive, they kill as many bees as they can, decapitate them and kidnap their young.

Until now, scientists were aware of some of the techniques used by bees to defend themselves, from "fecal spotting," which is putting the feces of other animals at the entrance to the hive to keep the bumblebees away, to "balling," a technique by which many bees surround a bumblebee, begin to vibrate their flight-related muscles and produce enough heat to kill it.

Researchers at the Royal Society Open Science have discovered a new defense technique: bees scream.

Researchers' discovery

We call them screams, but that's an approximation. Rather, it is a sound similar to the sound of air passing through a tube. The bees gather together, and by vibrating their wings they raise their abdomen, thus exposing a gland used to release a pheromone that then serves to guide them to the hive.

In this way the bees produce an "antipredatory" sound, which to the human ear sounds like a high-pitched whine. For bees, it's a call to arms: "they don't communicate through sounds," explains Heather Mattila, a biologist who co-authored the discovery, "but through vibrations, which are released into the surrounding environment and captured by the bees through their legs."

It's an important discovery, because it could be the first step in demonstrating that communicating a state of danger could be a universal experience for animals. And bees do well to feel in danger with Soror Wasps, which have large mandibles capable of dismembering multiple bees together and stingers so sharp they pierce bee suits.

That "screaming" is a clever technique that allows bees to defend themselves, but it's also not the first skill they've developed to adapt to their environment.