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Nature & Wildlife

Across the region, we are lucky to have a wide variety of habitats and landscapes giving us the opportunity to observe a wide range of flora and fauna. From windswept shores to inland waterways, from plains to craggy rockfaces, each has secrets to share. 

At Living, we have teamed up with experts in the region to show you what to watch out for at the different times of year...

 

Asian hornets - the truth behind the myths

Asian hornets - the truth behind the myths

It is now over ten years since the Asian Hornet was first brought into France. Chris Luck discusses how their introduction has impacted on honey bees and humans, and separates the myths from reality…

It is believed that the first Asian Hornet was imported to France from China in 2004 in a container of pottery passing through the port of Bordeaux. Judging from what I see on a day to day basis it’s quite clear that there is still a great deal of confusion for some people with what Asian Hornets are as well as what they look like. This hasn’t been helped by some fairly poor journalism and often mixing the Asian Hornet, Vespa velutina nigrithorax, the species which is present in France, with the Giant Asian Hornet, Vespa mandarinia, which isn’t present in France.

Despite various scare stories they are actually slightly smaller than the European Hornet, Vespa crabro. with queens up to 30mm, and workers up to 25mm. They are easily recognisable by their appearance and difficult to confuse with any other species. The thorax is a velvety black/dark brown with brown abdominal segments. Each abdominal segment has a narrow posterior yellow border, except for the fourth segment, which is orange. The legs are brown with yellow ends and the head is black with an orange yellow face. If we contrast this with the European Hornet which is a little larger and looks like a big wasp with typical black and yellow shaped banding on the abdomen and a reddish brown and black head, we can see at a glance which is which.

Their actual biological life cycle is exactly the same as the European hornet and all of the social or colony-forming European wasps although there are some minor variations with the nest. Most species make their primary nest where it is to stay and be their only nest; this is not the case with the Asian Hornet.

Starting in springtime, mated Asian Hornet queens from the previous year emerge from hibernation and look for places to make a primary nest that will be, almost without exception, situated in a sheltered place. This could be anywhere - attached to the inside roof of a shed, a barn, under the eaves of a house, in an old wine barrel, a cavity in a wall or somewhere similar. The nest is made from chewed wood made into a sort of papier-mâché and, when she has built the first 7 six-sided cells, she puts an egg in each. Within 2 or 3 days, the eggs hatch. She feeds insects to the larvae, usually honey bees, that she has chewed up for them and they mature inside their cells. After 12 to 18 days of this, the larvae encase themselves in their cells with silk cocoons to pupate then, after about 12 more days, they come out fully grown. As soon as theses initial larvae have started to pupate she is free to make more cells and lay more eggs. As the workers, which are sterile females, start to hatch they help and gradually take over continued nest and cell construction leaving the queen to stay in the nest. Somewhere in these early stages the queen may decide to move with her entourage to another location and start a new nest which is typically near the top of a large tree but it could be in a bush or hedge as close as 50cm from the ground. What has become clear is that although the nests in the early years following their arrival in France were exclusively high in trees, they can now be found almost anywhere. I have seen them in stone walls and even in one of my empty topbar bee-hives. The nest grows slowly to start and it isn’t normally until at least late August or more usually late September that the colony starts to reach its full size. This is when the queen starts to lay different eggs that will produce males and new fertile queens. When they emerge, the males mate with the new virgin queens and the colony dies completely leaving only the newly-mated queens to go their separate ways and find places to hibernate for the winter. This is exactly the same for our European Hornet and all our other colony forming wasps, only the newly-mated queens survive the winter.

Dealing firstly with the issue of how dangerous they are to humans this has been grossly exaggerated by some news sources. According to Dr Stephane Guez, head of the unit of allergic diseases CHU de Bordeaux, their sting is no more dangerous than other insects of the same type, (wasps, hornets, honey bees etc.). The fact that there have been a handful of instances of mortality resulting from Asian Hornet stings should be looked at in the context of the number of deaths or hospitalisations resulting from other stings every year. Before you panic, actual deaths from wasps and bees amount to perhaps a dozen a year at the most for the whole of France, are rarely the result of a single sting and usually the person has a pre-existing health condition.

Now we come to the vexed issue of just how great is the risk they pose to honey bees and as always it’s difficult to get objective unbiased information. Many bee-keepers are culpable, in my opinion, for blaming the demise of a colony on what they assume has happened without actually knowing or understanding the underlying situation. Hence there are bee-keepers that will tell you that European Hornets or wasps have destroyed a colony without understanding that the colony was already weak and failing which made it vulnerable. Even a small colony of perhaps ten or fifteen thousand bees, if they are healthy and vigorous, will defend itself against wasps. It’s the same story with wax moth which is often given as a cause for the demise of a colony when in fact a strong healthy colony will either remove, or coat with propolis, any wax moth caterpillars that do manage to hatch inside the hive. Only a colony that has died or nearly died will succumb to a serious infestation of wax moth.

To get to the point, what we can say with certainty is that Asian Hornets do take honey bees to feed their larvae (they don’t actually eat them themselves). What isn’t clear is how much impact that will have on a healthy colony and in what circumstances? I have Asian Hornets around my hives taking bees every year and even had a sizeable nest in a tree last year not 50 metres from my hives which I didn’t see until the leaves fell in autumn. Yet even with this situation there wasn’t enough bee killing activity to give me cause for concern. Perhaps it’s because I have a lot of hives that the burden is spread between them and it’s possible that an isolated hive or two would in some situations become too disrupted by a high loss of bees bringing in pollen and nectar that is essential for a bee colony preparing for winter and raising their winter bees. What is becoming clear is that as they have spread over France during the last ten years it hasn’t produced the catastrophic colony losses that some initially feared. Although good news it isn’t a cause for complacency, we still need to do what we can to limit their numbers. Realistically this breaks down into two things, destruction of nests when located before October and the killing of any that are seen in spring before May as these will probably be mated queens. Trapping or killing of individual workers from May until October is a fairly pointless activity in my view and will make little or no difference whatever means are used.
Although the European Hornet will also take honey bees and other insects to feed their larvae this is a perfectly natural situation and should be of no concern. They have lived alongside each other for thousands of years and their nests should be left unharmed unless causing a real danger to humans. In most situations if you leave them alone, they will leave you alone.

Should you find an active Asian Hornet nest between May and November you should contact your local Mairie or the Pompiers. They can hopefully advise you as to the situation regarding destruction where you are as, in some départements, this is a free or part-funded service.

 

 

© Living Magazine. Orinally published in October 2015