Many of you have probably seen the headlines circulating in major newspapers and Facebook posts about the Murder Hornet making an appearance in the United States and Canada. Although I am glad to see attention being drawn to this serious threat to our honey bees and the beekeeping industry, I want to clarify a few points, raise awareness (and appreciation), and hopefully calm some fears.
The hornets appeared first here in Canada, being spotted on Vancouver island in August/September of 2019. Shortly after a couple of independent sightings, a nest was located and destroyed. This is not the end of the story however, as another Giant Asian Hornet was found on the mainland in British Colombia in November. And then in December, a specimen was collected in Washington State. According to a recent news article, the hornet found in Washington State had a different genetic background from the hornets found in BC, meaning they are unrelated to one another. It is hard to say how significant this will be, but when dealing with an invasion of a foreign pest we ideally want to find it as soon as possible before it can become established. Having what seems like at least 2 independent introductions makes me more concerned that at least one of these introduction of hornets will be able to get nice and cozy here. The flip side though is that this means the same family of hornets did not spread from Vancouver Island to mainland BC to Washington, making it more hopeful that we have eliminated them before they were able to spread.
So what exactly is a Giant Asian Hornet? Scientifically, it goes by the name Vespa mandarinia and it is the largest hornet in the world. They can be up to 50mm in length with a wingspan of 76mm! Just the stinger alone is 6mm, and is said to be far more painful than the bees and wasps we are used to. But it isn’t just size that sets them apart from the Vespa species we are used to sharing our continent with. They are fierce hunters of honey bees, and capable of mass destruction. And even though I do not want any bees to be harmed, and I worry about the potential impact on our beekeepers, they are a pretty cool insect in their own right.
Mated queens, known as the foundress, will set up a nest in an underground cavity, and she will start to lay eggs that will develop into the workers. These workers will expand on the nest by excavating and removing little balls of soil in their mouths. They drop the balls outside at the entrance, building up a distinctive platform of soil over the season. The population will increase over the summer, and once autumn hits new queens and drones (males) will be raised. The new queens will leave the nest to mate and will then find a protected site to overwinter by themselves. These queens will be the foundresses of new nests come the spring, with the old nest dying off with the cold weather of winter. And like our honey bees, these hornets need lots of protein to feed to the baby hornets (larvae) that are rapidly growing within their nests. But unlike our honeybees, they do not use pollen for this, but depend on meat from other insects, as well as carrion. And in their gigantic eyes, honey bees make a great target.
When preying on honey bees, Vespa mandarinia will hang out near the entrance of the hive waiting for victims venturing out or returning home. The hornet will catch a bee, not a fair fight given the size difference, and remove it’s head, legs, wings and abdomen. All that will remain of the honey bee is the thorax – a sort of bee meatball – and this will be taken back to the nest to be fed to the larvae. Understandably, the presence of these hornets can cause stress for the honey bee colony and decrease foraging, and this type of predation can cause a drop in population size over time. But it can also get far worse. Sometimes the Giant Asian Hornet will change from this hunting behaviour to a slaughtering behaviour. When this happens, anywhere from 3 to 50 hornets will target a single colony and they will deliver fatal bites to the bees without stopping until they can gain access to the inside of the hive. Thousands of bees can be killed in a matter of hours, with the corpses being left in a heap on the ground. Once inside the hive, the hornets will begin to steal the developing pupae, and later the bee larvae to take back to their nest as an extra special protein snack. It is important for beekeepers to be aware that once the hornets have occupied a hive they will aggressively defend their conquered territory. And even if a few living bees remain, the colony will essentially be dead.
These hornets are native to temperate Asia, where they have evolved alongside the Asian honey bee, Apis cerana. This co-evolution has created one of the coolest counter-attack techniques I have ever learned about. When there are hornets outside the colony A. cerana will use stop-signaling to communicate to all of the bees inside the colony that they should stay inside the hive and increase guarding. If a hornet happens to enter the hive, the bees will all pile onto it and start to vibrate their flight muscles. These vibrations will generate body heat, increasing the temperature of this little bee ball (with the hornet in the middle) to 46 degrees Celsius. This temperature is lethal to the hornet, whereas the bees can tolerate temperatures of 48 to 50 degrees Celsius. Unfortunately, Apis mellifera, which is the honey bee that we keep here in North America has not shown the ability to perform this awesome heat-balling technique.
Images of honey bees being decapitated and slaughtered, and hornets being cooked to death, certainly sound like something out of a horror movie. And with these hornets now affectionately being referred to as Murder hornets, it is not wonder many people are feeling a little uneasy about these visitors which could potentially become permanent residents. It is important to keep some perspective. First, these hornets are not wide-spread across Canada and the US. If you live in Ontario, like I do, it is extremely unlikely that you will spot one flying around your garden this year. Secondly, we do not yet know if these hornets will even survive our climates. It is plausible that the milder winters along our pacific coast will be suitable, but the harsher winters in the prairies and central Canada may not allow them to stay here year after year. Hopefully we do not get a chance to find out. And lastly, even though these hornets have large stingers, and an associated painful sting, they are not out hunting humans. They will, like the other wasps and hornets we are accustomed to, aggressively defend their nests. So if you see one out flying, leave it alone and it will do the same. If you stumble upon a nest, get out of dodge! In a way, I am thankful for all of the media coverage, even if it is overly sensationalized. Our greatest defense against these hornets setting up permanent residency is finding them and alerting the proper authorities. The more people that are aware, the more likely they will be spotted! If you do happen to find what you think is one, try to snap a picture and please contact the Provincial/State Apiary Programs, Ministry of Agriculture or the Canadian Food Inspection Agency. That being said, not every large insect you see this summer will be a Giant Asian Hornet. In fact, it is highly unlikely. So please be respectful of the insects we do share our home with. Even the ones we do not particularly like (I’m looking at you Yellow Jacket) play a valuable role in our ecosystem. So do not be afraid, but please do be vigilant.