A sting in the tale
The long, hot summer of 2018 has been fabulous for wasps of all species – especially for dedicated hornet watchers.
Explore the social world of the hornet with a photographer who gets a buzz out of these striped insect predators
Afew years ago I was ambling through the woodlands of the RSPB’s Arne reserve in Dorset in pursuit of striped ladybirds. These are a fairly scarce and localised species associated with Scots pine, and Arne happens to be great for them. Suddenly, without warning, I came across some much more imposing insects: I found myself near patrolling European hornets – the largest species of social wasp native to this country, or indeed the continent. A steady stream of these chestnut-and-gold insects flew by me. They were simply mesmerising.
I felt immensely privileged. For while hornets may be big and somewhat intimidating, they are characteristically secretive – far more so than the common wasps with which we are more familiar (and which made their presence felt during 2018’s long heatwave). Standing just a metre or two from the Arne hornets, I was captivated by their beauty – and, yes, their calm.
Hornets are relatively common in mature woods across central and southern England, but also occur in parks and rural gardens.
They are expanding in range, and now can be seen as far north as Northumberland. I encounter individual hornets reasonably frequently in and around my own garden in Oxfordshire, and am always delighted to get a glimpse of these alluring predators. But one man has taken things a step further.
Stephen Powles has long had a passion for hornets, and quite literally has a window into their secret lives, thanks to a rather special nestbox that he has made in the converted barn where he lives in Devon, with a window facing into his spare bedroom. He had been hoping to attract blue or great tits, but ended up hosting a much more interesting species.
Instead of welcoming birds, the nestboxes have for the last few years been occupied by hornets – and Stephen is delighted. His passion for these wasps is inspiring. “My interest in hornets began when they moved into one of my barn-owl nestboxes,” he says. This choice of nest site is not that unusual, since hornets readily use roof spaces and outhouses, as well as hollow trees. What is a little out of the ordinary is that Stephen’s barn-owl nestbox was built into the gables of his roof. Up there, the hornet nest was able to reach impressive dimensions.
“One summer I climbed into the loft to check for possible signs of a roosting barn owl,” Stephen recalls. “I carefully opened the ‘back door’ of the nestbox, only to be greeted by 200 or 300 irate hornets. I don’t know who was more surprised – them or me! I quickly closed the door again, and so began a 15-year fascination with these insects.”
Since then, Stephen has spent hours capturing hornet behaviour on film and in photographs, creating a uniquely detailed perspective on the life history of, in his words, “these much-maligned super-wasps”. In 2016, BBC Wildlife writer Mike Dilger even paid a visit, with film crew in tow (their remarkable film is still available to view on BBC One’s The One Show website).
Hornets are closely related to a number of other social wasps within a group called Vespinae. Many of these are yellow and black, whereas hornets are yellow and brown. Hornets are large wasps, with queens reaching about 3.5cm in length and workers about 3cm. They are commonly confused with queens of the median wasp, but lack the deep black markings of that species. Additionally, hornets do not have yellow markings on the thorax, while the median wasp has distinctive yellow bands running along its sides and the workers are, of course, much smaller than hornets.
In recent years, the Asian hornet has also been much in the news in this country, though as ever with non-native species, some of the reporting has been sensationalist. Slightly smaller than the European hornet, this species has yellow ends to its legs, unlike the all-brown legs of its relative. Its head is dark from above but orange in front, while
“My interest actually began when hornets moved into one of my barn-owl nestboxes.”
the head of the European hornet is yellow from above and to the front.
Hornets are described as ‘advanced eusocial wasps’ – that is, they form a colony comprising overlapping generations, with the adults represented by the reproductive queen and non-reproductive workers. The workers undertake various tasks, from caring for the larvae that develop in small cells within the nest, to foraging for food, water and nest materials. There is some evidence that, as with honeybees, worker hornets take on different tasks at different stages in their short lives. “The life of a worker hornet is certainly very busy,” says Stephen.
Clearly, the queen hornet has the most important role in the colony – that of producing offspring. Indeed, she is mother to all the individuals within the colony, which can eventually, as with the nest in Stephen’s owl box, grow to include several hundred workers. Like other social wasps in Britain, hornets have an annual life-cycle – in other words, it begins afresh each year, starting with the emergence of a mated queen from her winter hideout. Stephen has finally succeeded in documenting most stages of this fascinating cycle, which ends with the demise of the entire colony, except for the newly mated queens.
A mated queen hornet will spend the winter alone in a sheltered position, such as under bark or in a crevice of some kind. In common with many British insects, she is dormant throughout the cold winter months. In spring, she emerges to find a suitable nest site – at this time of year, queen hornets can be seen foraging for wood fibres, scraping dead wood with their strong mandibles and macerating it with saliva to form a pulp for constructing a small, embryonic nest resembling a sphere.
Inside are hexagonal cells that open downwards within structures known as combs. The queen will lay her first brood of eggs in these cells; these eggs hatch after about a week and the queen rears the larvae on a mixture of mashed-up insects and spiders. A predatory role is important; by feeding on invertebrate species, hornets contribute to the functioning of our ecosystems. It is an intensive start to the year for the queen hornet, who feeds on carbohydrate-rich substances such as nectar and honeydew – or even honey stolen from colonies of bees.
After about two weeks, the hornet larvae have gone through five growth stages called instars and are ready to pupate. Each larva produces a silk-like substance to close its cell and then pupates for a couple of weeks. The newly emerging adult worker rasps at the surface of the silk cover with its strong mandibles, slowly rotating its head while progressively scraping away, and only cutting through the cover once it has been breached.
The new worker hornets then remain in the nest for a few days before taking their first flight. During this time they fulfil the
A predatory role is important; by feeding on invertebrate species, hornets contribute to a functioning ecosystem.
important task of raising the temperature of the cells they sit on. The way in which social insects can control the temperature of their nests is quite incredible. Not only can hornets warm up cells, but they can also reduce the temperature by rapidly beating their wings to fan the cells or by delivering and spreading cooling water to the surface of the cells.
The first brood of adult workers takes over the nest-building work and looks after the new broods hatching from the queen’s eggs. So the colony grows. Every second counts to ensure its survival. “Hornets will continue to fly well after dark on warm evenings all through the summer and early autumn,” Stephen points out. “Like moths, they’re attracted to the lights in our homes. So hornets can be seen circling outside security or porch lights, or flying up and down lit windows.”
Things don’t always go to plan, however. There are a number of guests – some possibly unwelcome – sometimes to be found within the hornet nests. Some are simply scavenging and feeding on left-overs within the nest, but there are some beetles and parasitic wasps that will feed on the developing brood.
Later in the season, the internal architecture of the nest changes, as large cells are built to accommodate the rearing of new queens. At this stage males, characterised by their long, black antenna and lack of a sting, will also be produced, but they will usually be assigned the smaller cells. Before the onset of winter, the founding queen is neglected by the workers and she dies.
Now the young queens and males emerge from the nest and mate. Most queen hornets mate with only a single male. This is not always the case, however: sometimes a queen might mate with two or three males, but even in that scenario, most of the queen’s offspring will be eggs fertilised by only one of the males, so the female workers are still extremely closely related. Following mating, the queens settle down for the winter and the workers all gradually die off.
The magnificent sight of hornets in flight is cause alone to stop and watch, but when you delve a little deeper, you realise these wasps are masterminds of architecture and social organisation. “The ways in which individuals within a colony work together is inspiring and captivating in equal measure,” says Stephen.
If you are fortunate enough to see hornets, then please do, like Stephen, take your time to observe them. Enjoy the behaviour of these incredible aerial predators, though keep a safe distance and don’t cross their flight paths. While Stephen has spent “countless happy hours” very close to hornet nests, this is not without its risks. But as his pictures on these pages show, these unsung heroes of the insect world are worth celebrating.
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Above: A queen returns to her nest in a grassy tussock. The European hornet Vespa crabro feeds on insects and other invertebrates, supplemented by sugary sap from trees and windfall fruit.
The queen begins building the nest in spring. The larvae develop in hexagonal cells which are sealed with a cap made from a silk-like substance under which they will pupate.
Clockwise from above: a male (note the long black antennae) basks on a tree stump while looking for a queen to mate with. The larvae develop in hexagonal cells where they are fed by the workers. Note the protein ball (probably insect wing muscle) that has been brought to the nest. Larvae of the hornet rove-beetle, which often lives in the nest with the hornets and feeds on their detritus. The nest is built up layer by layer.