Honeybees Scream in Alarm When Attacked by Giant Asian Hornets

by Katy - Bee Missionary November 11, 2021

Honeybees Scream in Alarm When Attacked by Giant Asian Hornets

We really had to think about whether to post this story, because for bee lovers it is heartbreaking. We decided to post it because we all need to be aware of just how many hazards honeybees face every day in our world. These vicious hornets are a growing problem for honeybees around the globe.

Hearing the bees scream is an unbearable sound. The giant hornets slaughter them brutally and at warp speed. Knowing that the bees actually scream indicates that they know what awful fate awaits them.

This is the first time that scientists have been able to document the warning cry that bees send out as one of their survival strategies, to warn the hive to move into defense mode.

This unrelated 1:41-minute video by LiveScience is the first video where you can hear the bees:

 

 

Heather Mattila is an associate professor at Wellesley College, in the department of biological sciences. She was part of the team of scientists that discovered and identified the bees’ warning noise.

The team’s paper was published in the journal Royal Society Open Science on Tuesday, and indicates that Asian honeybees (Apis cerana) only emitted the sound when giant hornets attacked the Vietnamese hive the research team was studying.

Once a scout hornet finds a target hive, all resident bees in the entire hive are wiped out within hours. They kill the adult bees, occupy the nest, and harvest the baby bees to feed to their own young.

Bees aren’t entirely defenseless, but have disadvantages. Asian honeybees have been dealing with Asian giant hornets for a very long time, but the hornets were just seen for the first time in the US in 2019, when they arrived in Washington state.

Mattila describes the warning signal as harsh and noisy, with fluctuating pitches and durations. It is now known as the “antipredator pipe.” She feels a visceral reaction when she hears it because the bees are clearly agitated. Worker bees string individual pipes of various lengths together to make longer signals and change pitch to make them stand out.

This unrelated 0:49-second video by New Scientist gives another view of how the bees react and scream:

 

 

According to Mattila, the study showed that the bees only made the sound if there were hornets. It was made less when smaller hornets attacked, a little more often if a giant hornet could be smelled (but not seen). They screeched by far the most when a giant hornet was directly at their nest.

Although they haven’t tested all predatory scenarios, this is good evidence that only a real hornet attack on Asian bees triggers this response. The signal triggers some defensive mechanisms honeybees have in their arsenal to deploy against the murder hornets, she said.

Some bee strategies are dung spotting — when bees collect animal poop and smear it at the entrances of their hive to confuse and repel hornets — and swarming (bee balling) to neutralize the enemy.

Balling involves hundreds of bees surrounding a hornet in just seconds, squeezing it, and constricting its ability to breathe. The bees raise their body temperatures to a level that is lethal to the hornet. This literally cooks the hornet. Mattila says the bees act as a collective boa constrictor.

Unlike the Asian honeybee, Western honeybees (Apis mellifera) have not evolved any strategies to defend themselves against Asian giant hornets yet. It is unknown how the Asian giant hornets arrived in the USA, but it likely was tied in with international container ships or travelers.

In 2021, there were 14 sightings, and 3 nests were found in Washington state.

According to Mattila, US honeybees are defenseless against the giant hornets, so they would not make sounds the Asian honeybees (Apis cerana) make or perform other important hornet defenses. The US honeybee has no experience of evolving a defense against Asian giant hornets.

In fact, when US honeybees are taken to Asia for beekeeping, they are an easy attack target for Asian giant hornets because they are so defenseless.

To read more about Professor Heather Mattila and this story, please click here

 

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Katy - Bee Missionary
Katy - Bee Missionary

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