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The Asian Hornet - Our Guide

Asian hornet sussex
Asian Hornet

We hope this post will act as a guide to the Asian hornet both in Sussex and the UK.



The background


Approximately 20 years ago a single mated female hornet (Vespa velutina) like the one above, was accidentally imported into southern France from China. Hidden amongst some bonsai trees imported to the area this stowaway's offspring quickly spread through western Europe at 78km per year, causing havoc to honeybee populations, honey yields and wild native bees as they went.


As of 2020 the hornets have conquered northern Spain and Portugal in the south, Germany and Italy in the east, and as far as Denmark in the north.


Separated by the English Channel their incursion into the UK has been delayed in comparison and since 2016 sightings of solitary nests have been managed by the NBU (National Bee Unit) whose policy is on a search and destroy basis.


The first sighting was in Tetbury, Gloucester - again just as in France, the hornet hitched a lift on a container lorry. A day after the Gloucestershire discovery another specimen was positively identified in Somerset. In both cases the NBU searched 20km radius' around the nest sites but discovered no more nests.


Genetic testing identified both cases as having come from 'French' hornets. Indeed, not long after, some dead hornets were found near Tetbury in a timber pile that had been imported from the Loire Valley. Similarly, dead hornets were found in camping equipment near the Somerset case after a camping trip to France.


The good news at this stage was that the males were sterile and that the nests had been destroyed.


In those early years more lone hornet nests were found in Scotland, Lancashire (in Cauliflowers transported from Lincolnshire), Cornwall, Hampshire & Surrey. Genetic testing showed they did not originate from the first sightings so likely from other random imports. The bad news was that the males were now fertile.


During this time the Channel Islands were fighting their own fight to protect their bees. At a relatively short 12 mile flight from Cherbourg France they've had more hornet queens than mainland UK. A civilian beekeeping taskforce set about destroying nests and learning all they could about these insects. Much of our knowledge comes from these dedicated folk.


in 2023 72 nests were killed in England. Twice as many as the year before. Unfortunately it looks like they are here to stay.

Hornets in Sussex and the south coast.


In 2023 the NBU destroyed 72 hornet nests, most of them were in Kent. The ports of Dover & Folkestone are obvious points of entry but experts think with the aid of a tail wind its likely some of these simply flew across the channel.


Its also been confirmed that the hornets are now 'overwintering' in the south with confirmed sightings in Rye, Hastings & Four Oaks in East Sussex in 2023 & the first part of this year.


Its inevitable a sighting will be made in West Sussex sometime very soon.


 

How to identify an Asian hornet


Summary:

Slightly larger than a wasp. Almost entirely black/very dark brown except for a thin yellow stripe by its waist and a a yellow stripe on the 4th abdominal segment (or tergite). It has an orange face from the front. Perhaps easier to see are the yellow 'socks'.


In comparison our native hornet is larger than the Asian, with a yellow abdomen and a very brown thorax and head.


asian hornet comparison european hornet
Asian hornet comparison with European hornet
an asian hornet identification
An Asian hornet
asian hornet european hornet honeybee wasp
Size comparison of Asian hornet and other insects

 

Honey bee predation


Asian hornets act much like our native hornet and wasps in that they target the adult bees for their meaty thorax and the hive itself for the honey. According to a study by Couto et al. hornets are attracted primarily to the smell of the hive (pollen, honey, larvae) and to a lesser degree to the adult bee pheromone Geraniol. One conclusion for their apparent preference for hives, rather than adult bees, was purely practical in that locating a large fixed target rather than individual bees was more effective for the hornet. In the study hornets preferred a hive over other sources of protein and sugar such as fish, which without bees present they would normally devour.


Once hornets have located a bee hive they begin 'hawking' behaviour. Patrolling the front of the hive at a small distance picking off returning foragers laden with honey or pollen. Observations of the hornets show them to pick off about 25 returning bees every half an hour. Over a prolonged period this will weaken the hive of its adult bees to point where it can be taken over completely. Or weaken the hive sufficently in the Autumn that it will not survive the winter.


In France beekeepers observed a stillness at apiaries when the hornets were about. Honeybees stayed inside the hive and other insects hid. If honeybees can't go out and forage they will eat through their stores and die.


At present the European honey bee (Apis mellifera) has no defence to this hawking behaviour. In Asia the honeybee Apis Cerana speeds up as it enters the hive to twice the speed of our European honeybee. It also leaves the hive in a straight line immediately rather than circling about like the European.


According to Sarah Bunker in her excellent Asian Hornet Handbook the Asian honeybee recruits more guard bees at the hive entrance and the colony performs a 'shimmering' movement which warns the hornets off. Apis Dorsata, another Asian honeybee also performs this shimmer dance.


Apis Cerana will also 'ball' hornets by mobbing them to form a tight ball, overheating and stinging the hornet. Our honeybee has this capability and I've seen it happen with random unwanted intruders but overall they don't tend to weaponise this capability against the hornets (or wasps for that matter).



 

The impact of the Asian hornet


The Asian hornet has no known active predator in the UK. In France some green woodpeckers and jays have been seen eating larvae from hornet nests when on the winter decline but nothing has been observed taking them 'on the wing'.


The impact of the hornets will come in waves and it will affect us on an economic, social and environmental level. Those first affected will be honeybees and beekeepers. The honeybees evolutionary choice to live in large colonies, which us humans stick in a nice tidy box makes the perfect target for hungry hornets. Colonies will be lost and honey yields will be lower. Many amateur beekeepers will give up and bee farmers like myself will have yet another problem to contend with. As if the rain, feed prices and varroa aren't enough. A figure of 30% losses is suggested by those who have studied hornets in France.


Second to be affected will be the pollination of crops. Honeybees are only responsible for 10% of crop pollination so the fact these hornets feed upon social wasps and wild bees, spiders and a variety of insects all vital for pollination is extremely worrying. Fruit farmers in France reported a drop in productivity resulting from both a loss of pollinating insects and also the hornets need for sugar from the ripe fruit at the end of the summer.


More worrying than all of this however, and ultimately more difficult to quantify will be the effect on wild bee species and the wider ecosystem. Song birds will suffer at a time where many are already feeling the pressure.


How the Asian hornet will coexist with our native hornet is also unknown. There will undoubtedly be competition for food sources and nesting places. European hornets do feed on honeybees but it is rare for it to cause a problem. I've seen many European hornets overwinter in the top of a beehive for warmth. The bees don't seem to care and a few bees will just chase it off when they want to in the spring. (seen in the picture below)


European native hornet and honeybee

sussex bee farm honey bee and fighting european hornet
Sussex Bee Farm honeybee versus european hornet


Our native insect species will also feel the fallout of the misinformation and hysteria in the media. I've already lost count of the number of times a newspaper has printed a picture of the Giant Asian Hornet alongside an article about our problem Asian hornet. They look and act very differently and although the Giant Asian hornet is a problem in the US, its never been an issue here. (touch wood). Misinformation will lead to misidentification and missed opportunities to kill nests. It will also cause hysteria in some camps and result in native hornets being killed.


Incidentally, the first sighting of the Asian hornet was confirmed in the US last year so now they will have to contend with both.


A quick word on stings... since the Asian hornet will have an impact on those allergic to stings and those who work outdoors.


The sting of the Asian hornet is more potent than that of our native wasp (Vespa vulgaris), although slightly less painful than that of our native hornet (Vespa crabro).


The problem arises due to the aggression of the animal on the other end of the sting. Our European hornet is less aggressive than its Asian counterpart if disturbed - more importantly though is that like the honeybee the Asian hornet releases an alarm pheromone when stinging which attracts its friends to 'the party'. Its sting is not barbed like a honeybee and so it can sting more than once.


Reports that the hornet can spray venom seem unfounded. (Sarah Bunker, The Asian Hornet Handbook).


 

What to do if you find an Asian hornet

Sightings of Asian hornets are legally required to be reported.


There are several ways of doing it and all can be found here.



 

Other yellow stripey things... not to be confused with the Asian hornet



A hornet moth not asian hornet

A hornet mimic fly not asian hornet

Giant horntail not asian hornet



 


Sources


The Asian Hornet Handbook by Sarah Bunker



Incidence and predation rate of hornets on European honeybee

Shah & Shah 1991



Olfactory Attraction of the Hornet Vespa velutina to Honeybee Colony Odors and Pheromones - Couto et al.



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