There is one guest nobody invites to a summer picnic and everybody expects anyway. The wasp arrives around the time the food does, hangs over the jam, dive bombs the glass of cider, and gets swatted at by six people at once who all miss.
Across Britain this year, it mostly did not come.
That is the observation, and it came from the one person in the country best placed to notice, because finding wasps is her job. Seirian Sumner is a professor of behavioural ecology at University College London, and she has spent her career on social wasps at a time when hardly anybody else wanted to. When she wrote up what she was seeing, the detail that stuck was not grand. It was that her students could not get hold of enough wasps to run their experiments.
And the ones that did turn up were small. Not slightly small. Spring small, in the middle of summer, which for anyone who knows how a wasp colony is supposed to work is the strange part.
Here is the thing she was careful to say, and it deserves to be said just as plainly here, because a lot of the coverage that followed lost it. These are anecdotes, not data. There is no peer reviewed finding. There is no confirmed population count for the year. What there is, at the moment, is a specialist noticing an absence that does not match anything she has recorded before, and saying so out loud while the counting is still going on.
Which makes this a story about the gap between noticing something and knowing it, and about a national experiment that happens to be positioned exactly in that gap.
The experiment is called the Big Wasp Survey. It started in 2017, and the method is about as unglamorous as science gets. Ordinary people put a small amount of beer in a trap, hang it in the garden for a set number of days during a fixed window in late summer, then send in what they caught so it can be identified to species. That is it. Beer, a bottle, a week, a post.
The first year, more than 2,300 people signed up and about 1,294 of them actually returned results, which produced 6,680 wasps identified to species. The breakdown was tidier than you might expect. Common yellowjacket and German yellowjacket split the catch almost evenly at around 44 per cent each, European hornets made up about 6 per cent, and a handful of other species accounted for the rest. Later, DNA work on those samples produced a genuinely useful result, which was that the common yellowjacket across the country behaves as one large interconnected population rather than a patchwork of separate local ones.
None of that sounds dramatic. It is, however, the only national wasp monitoring this country has. And when Sumner wrote up her observation in high summer, the survey had not yet started sampling for the year. The traps go out in a window in August and another at the turn of the month. So the person raising the alarm was doing it in the one part of the calendar where she could not yet check.
That is not a flaw in the story. That is the story.
The beer trap is doing something clever with all of that. It is cheap enough that thousands of people can run one, it is standardised enough that the results can be compared between a garden in the far north and a garden in the south, and it is timed to the exact stretch of the year when workers are out and easy to catch. It also produces physical specimens rather than sightings, which means species can be confirmed under a lens and, as the DNA work showed, interrogated years later for questions nobody was asking at the time. That is a lot of scientific return for a bottle of cheap lager.
To understand why small wasps in August are a signal rather than a curiosity, you have to know what a wasp colony’s year looks like, and it is more precarious than the picnic version suggests. A social wasp colony does not overwinter. Every single nest you have ever ducked away from was built from nothing that year by one female, working alone.
A queen comes out of hibernation in spring, finds a cavity, chews wood into paper, builds a few cells, lays into them, and then feeds and raises that first tiny batch of workers entirely by herself. There is no colony to help her. If she dies in that window, or if the weather keeps her from foraging long enough, that is the end of it. Nothing is left behind. The whole enterprise rests on one insect having a good few weeks in spring.
Once those first workers emerge, the arithmetic flips. They take over foraging, the queen switches to laying full time, and the colony scales up fast through the summer until it is the loud, confident, jam stealing operation everyone recognises. Workers that emerge early are naturally small, because there were few foragers to feed the larvae. By late summer they should be noticeably bigger, because by then there are hundreds of adults bringing food in.
So small workers in August mean one of two things, and possibly both. Either the colonies never built up enough foraging capacity to feed their larvae properly, or the larvae developed too fast in unusual heat and emerged underfed and undersized. Neither of those is the signature of colonies that simply started late.
There is a reason beer works, and it is the same reason wasps become a nuisance in the first place. For most of the summer a worker wasp is not interested in your food at all. She is hunting protein, caterpillars and flies and aphids, to carry back to the larvae in the nest. What she gets in return, from the larvae themselves, is a drop of sugary liquid. That exchange is the engine of the whole colony, and it is why a wasp ignores you in June.
Late in the season the queen stops laying, the larvae run out, and the sugar supply that kept the workers going simply ends. Thousands of adults are suddenly unemployed, hungry for sugar and with nothing to do. That is the wasp at your table. It is not aggression. It is an entire workforce made redundant at once, going looking for the only thing it still wants. They find fallen fruit, they find your drink, and they get clumsy and bold in a way that reads as malice and is closer to desperation.
Meanwhile a small number of new queens have been produced, mated, and left to find somewhere to spend the winter under bark or in a shed. Everyone else dies with the first hard cold. The nest is never reused. Next spring the whole thing starts again from those few hibernating females, which is why a bad spring does not dent a colony so much as delete a generation of them.
Which brings in the weather, and here the numbers need handling with care. Sumner points at a spring of extremes, warm dry stretches broken by cold damp spells and chilly nights, hitting precisely during the period when lone queens are most exposed. Then came the heat. Social wasps are reported to have a critical thermal maximum somewhere around 45 degrees Celsius, and during the summer’s heatwaves ground surfaces in the country reportedly exceeded 50. For scale, honeybees are generally put at around 49. Wasp nests, especially the ones started in shallow ground cavities and banks, sit right where that heat lands.
That figure of 50 degrees at the ground surface is the one to hedge, and it is worth saying why. It is a surface temperature, not an air temperature, and it comes through a comment piece rather than a published dataset. It is entirely plausible and it is not a measurement anyone has yet tied directly to a count of dead nests.
There is also a serious counterargument, and it comes from the same expertise. Social wasps are supposed to be tough. Nests are insulated by their own paper construction. Workers cool them behaviourally, fanning and carrying water. The diet is broad rather than specialist, which usually protects an animal when one food source fails. On paper, a wasp should ride out a bad summer better than a fussier insect would. That is exactly why a summer this quiet is interesting rather than expected.
And there is a longer pattern underneath it. Wasp numbers swing wildly year to year, far more than most insects. Last year was the opposite of this one, a boom year following a warm dry spring, with the predictable wave of newspaper stories about plagues of wasps. The absence of those same stories this year was, oddly, one of the first clues anybody noticed. An analysis published years ago that pulled together nearly four decades of records from a handful of English sites found the same thing in the long data: enormous swings, boom and bust, driven largely by what the weather does in a narrow spring window.
So the honest question is not whether wasps have crashed. It is whether the swings are getting wilder, and whether the window a queen needs is being squeezed from both ends, by heat that arrives too early and cold that returns too late.
There is one more pressure being raised, and it comes from people who deal with wasps commercially rather than academically. Pest controllers say they have had far fewer callouts for nest removal this year, which is its own kind of evidence, collected by accident. One of them has also flagged a different problem entirely: spring trapping campaigns aimed at invasive Asian hornets are not selective, and native wasp queens reportedly end up in those traps too, during the exact weeks when the loss of a single queen costs an entire colony. That claim comes from a pest control operator rather than a study, and it is worth knowing about rather than treating as settled.
Now the part that decides whether any of this matters to anyone who does not love wasps, which is nearly everyone.
Sumner and colleagues went through more than 500 academic papers a few years ago, covering roughly 33,000 species of stinging wasps, and put together the case that wasps do the same categories of work bees do while receiving almost none of the credit or the funding. Wasps are predators, and they are efficient ones. They take aphids and caterpillars in volume, which is to say they eat the things that eat crops. Insect predation as a global pest control service has been valued at somewhere around 416 billion dollars a year, and wasps are barely counted in that figure at all, mostly because nobody has done the work to count them.
They pollinate too, which surprises people. The review found evidence of wasps visiting 960 plant species, and 164 of those are completely dependent on wasps for pollination, meaning that without wasps those plants simply do not reproduce. Global insect pollination is valued at well over 250 billion dollars a year. Wasp venom and saliva have antibiotic properties, and yellowjacket venom has been studied for possible use against cancer cells. In parts of the tropics, wasp larvae are already food.
That is a substantial resume for an insect whose entire public identity is ruining a barbecue.
The funding gap is the reason this summer is so hard to resolve. Bees get monitored, mapped, modelled and mourned. Wasps get a citizen science project running on beer and goodwill, because the people who fund insect research fund the insects people like. The consequence is that when something unusual happens to wasps, the country’s ability to say what actually happened comes down to how many strangers hung a bottle in a hedge in August.
Two caveats before the end. The first is geographic. Everything here is Britain. There is no comparable set of reports from elsewhere, and it would be wrong to read this as a global event. The second is the one Sumner put first, and it still stands. Nothing here is a confirmed population decline. It is an absence, described precisely by somebody qualified to describe it, waiting on a count.
That count is happening now. The traps went out in the usual late summer windows, the returns come in afterwards, and the samples get sorted and identified species by species, the same way they have been for close to a decade. For most of those years the survey has been building a baseline that nobody had an urgent reason to look at. This year it has a question waiting for it, which is the situation every long running monitoring project secretly hopes for and never quite expects.
And if the traps come back light, the finding will not be that a nuisance went away. It will be that a predator, a pollinator and a decomposer went quiet at the same time, and that the only reason anyone can put a number on it is that ordinary people spent nine summers counting an insect they do not like.
The wasps may well be back next year. They usually are, and a boom summer would surprise nobody. But this is the first time the absence of something everybody swats at has been measurable, and that is worth more than the picnic it did not ruin.