Thursday, May 7, 2020

Asian Giant Hornets

Asian Giant Hornet (Vespa mandarina)
Photo by: []
     There's been a lot of hype lately concerning the Asian Giant Hornet (Vespa mandarina) after a New York Times article revealed that some had been found in Washington state a year ago. They even gave them an equally sensational name of "murder hornets" despite no entomologist ever having called them this. So I think it's time to set the record straight on these large wasps and the couple of things locally you really are much more likely to get them confused with.
     So let's be clear that this discovery was last year, first in September in Nanaimo in Vancouver in British Columbia, Canada, They quickly destroyed the nest and set up traps to see if any other ones were around. It was in December of last year that they found dead Asian Giant Hornet about 50 miles away in Washington state. Despite it's proximity, some tests determined that it was not from the same underground colony as the others. Since then, there have not been any more of these hornets seen live or dead in the USA, just the ones from 2800 miles away the previous year.
     Now if these Asian Giant Hornets, the largest of all hornets, are found to have been established colonies, that would be bad for our European honeybees that did not evolve with them and have no defenses such as the Japanese honeybees do. But this unlikely to happen with controls in place and it would be near impossible for that to happen here in the DC area.
     So all the hype is just that, just hype. I've already been getting people sending me pictures to see if they have found one. They have of course all been negative, just local species that people have people have made the villains. Let's recall a few natural history facts relating to Asian Giant Hornets. Much like other hornets, they only produce queens that can start a new colony at the end of the year when their original nests fall apart. Each individual worker hornet cannot produce any new nests. Only those at the end of the year that have been fertilized by male nonstinging hornets can produce eggs. Please recall that no male bees, hornets, or yellowjackets can sting, as the stinger is a modified ovipositor (egg layer). So males, as they don't lay eggs, can't sting. The odds of a fertilized queen finding their way over here in the DC area, knowing that a very small population at best was found 2800 miles away, is extremely small. They also prefer deep woods to establish their underground nests, which again is not as likely to happen in our DC urbanized area.
     Let's also look at this sensationalized name of "murder hornets". Now despite the claims, they are actually have less toxic venom than some of our local yellowjacket species. Now they are bigger so likely may inject more, but they are not looking to sting people. Much like our other social wasps, they will defend their nests, when they're threatened, but overall do not look for people or attack them in more numbers than any of our local wasps. If someone does have an allergy to them, then that could be a problem, and no tests have shown they are any more likely to have people allergic to them than our own honeybees. In fact, more people die of allergic reactions to honeybees in the US than they do from Asian Giant Hornets worldwide each year. And this is still less than those that die from getting hit by lightning each year as well.
     Now complete disclosure, I am (or perhaps was) allergic to yellowjacket stings. This did not mean I was allergic to other stinging insects such as paper wasps or honeybees.When you have an allergic reaction, it is often pretty specific. The venom of each is different, so just because someone is allergic to bees, does not mean that they are also allergic to hornets or yellowjackets, or vice versa. For me, as I'm outdoors all the time, I had been stung too many times, including when I was with kids who batted at yellowjackets for which I got stung getting them out of the way. I got stung once too many times and ended up in the hospital. I've since gone through therapy getting injections from yellowjackets so that I'm supposedly resistant again to them. Funny that since I was aware of this, I've not gotten stung in many years. I'm gotten almost a 6th sense about yellowjackets, even though my job often requires me to investigate these stinging reports.
     Now again, despite all the hype, you are very unlikely to find any anywhere near the DC area, we will show what they look like compared to the two other locally found large species in our area. Now of course many people will look at size as the first thing they will notice. And it would be important. Maxing out at 2.2 inches, Asian Giant Hornet queens are the largest of the hornets. The workers which you would most likely see if any were any in this area are much smaller at 1.5inches. Believe it or not, people actually eat their larvae in some places.
A comparison of the 3 largest stinging insects in our area. These are all workers, except for the Cicada Killer which is a female. Notice the eye placement of the Asian Giant Hornet well in front of the head.
Photo from Franklin Master Gardeners

     While size maybe the first thing you notice, we have two others of similar or greater sizes (recall a Cicada Killer is not a hornet and the females who prey on cicadas are larger than other workers). For Asian Giant Hornets, their eyes are set far forward on their yellowish/orange heads. They tend to have distinctive fairly similar stripes across their abdomen. And once again, a reminder that No Asian Giant Hornets have been found in the DC area, or outside of last year's discovery of a dead one in Washington state.
     The creature most likely to be confused with the Asian Giant Hornet around here is the European Hornet, a rather large relative with a dark head and irregular stripes across its abdomen. These were originally introduced into the USA over a 150 years ago, and have in that time extended their range to the eastern third of the United States. This does go to show, that with similar life cycle to Asian Giant Hornets, it would indeed take a long time for them to really expand their range. Right now the extremely large queen European Hornets have overwintered and are looking for places to build their nests. These are the most easily confused to the Asian Giant Hornets. They usually choose an opening in a tree, but some have occupied sides of buildings.
A European Hornet worker (Vespa crabro) showing its size difference with a Yellowjacket flying over top. They take all sorts of other insects as food for their young, particularly preferring cicadas leading many to confuse them with Cicada Killers.

     These nonnatives have never endeared themselves to people. Workers are large at about 1.4inches long. They spend most of the summer hunting other insects to feed their young. This includes taking of large butterflies like swallowtails and Monarchs, along with large bees and wasps. I've seen them wait for the pollinator to use a flower and then trap their prey against the bloom. I've also seen them take down full grown mantids.
     They also cause damage to trees. They will tear off small pieces of bark to use in making their nests. They seem to really prefer lilacs, but also take advantage of sapsucker wells to start striping the bark in squares. They will often eventually lead to stripping so much bark they girdle the tree so it dies.

A tree girdled by hornets.

    These are also one of the few wasps and hornets that are attracted to light. This does confuse and puts them in a bad mood, should they come to your porch lights.

An injured European Hornet that has been attracted to light and then caused damage to itself against the light fixture.

    In the Fall, after much of their raising of their young has concluded, they are often attracted to fruit. This does make these nonnatives a pest of orchards.

An apple tree feeding European Hornets.

     The other large creature (they can get to just over 2inches) often confused for Asian Giant Hornets are Cicada Killers (Sphecius speciosus) or Cicada Hawks. These are large solitary wasps that build individual holes in the ground they then fill with cicadas for their young to feed on. Though on average larger than the other species talked about here, they are actually quite docile and difficult to get angered enough to sting. People often mow grass right along side them with no fear of retaliation. They're stings are also said to be very mild as well, contrary to the reputation of the previous wasps discussed. As these are solitary, they prefer to fly away than to defend their nests, for if they die, no one will raise their young. So despite their large and ominous appearance (the males who can't sting are often flying low over burrows and can be intimidating), females only go after cicadas and are harmless to other creatures. These tend to come out in mid summer and look for sandy areas to build their holes. You can read more about them here in this blog:

A female Cicada Killer makes off with a cicada to provision her burrow for her young.

     There are few others that are large enough to be mistaken for Asian Giant Hornets. One is another hornet, the Bald-faced Hornets that are large and have their nests in trees. More on the in this blog:

A Bald-faced Hornet (Dolichovespula maculate )
     A short video of several wasps taking advantage of an injured tree with sap is here:
     Most people recognize fuzzy bumblebees so as to not confuse them with others. A few though get worried due to the size of carpenter bees, as I've been sent some pictures to ID them. While they may also seem to be intimidating, they are pretty much harmless. More here on them and bumblebees here: .
     The bottom line is that though it's always good to be aware of invasives, the scare tactics out there so far is just hype. Calling them "murder hornets" and scaring people on what really is an extremely low chance of anything happening around here is poor reporting at the very least. The damage they've done as people just start destroying other beneficial pollinators has already taken place. While destroying a few nonnatives European Hornets is not a bad thing, the others such as cicada killers and other pollinators that will also suffer is sad to see. Folks, please don't get scared by these poor reports that are going on out there. The chances of seeing any Asian Giant Hornets, "murder hornets", when they've only been seen a year ago 2800 miles away is extremely low. So its good to be aware, but irrational to let this scare you that every big bug you see is a danger to you.