With summer gone at last after a blissful final fortnight of sunshine, I wish to advance a proposition with which many people may disagree: having fewer wasps around is not necessarily a good thing.

In Britain, wasps are high on the list of what my wife refers to as nature’s unloved creatures. With their propensity to swarm around our picnics, seek out our sandwiches and then sting us painfully if we try to swat them away, the unpopularity of wasps is great and understandable. So if I say that the more common wasps are tumbling in numbers you may well give a hearty cheer.

But I’m afraid I won’t join in, for this decline represents another facet of a very troubling phenomenon: the catastrophic crash of our insect populations over recent decades, almost certainly because of the amount of pesticides now used in farming. That’s something else which people may instinctively applaud, since insects in general – apart from butterflies and perhaps bees – are often thought of simply as shudder-inducing creepy-crawlies.

But insects, and invertebrates in general, are “the little things that run the world”, playing a key role in many ecosystems, and if you take them away there will be consequences, just as surely as there would be consequences if you took a third of the parts out of a Boeing 747 and then tried to fly it. A few weeks ago I gave an example in this column: the disappearance of one of our most charming small songbirds, the spotted flycatcher, which has declined across Britain by 90 per cent, to the great sadness of many people who used to love it; there is little doubt that it has vanished because the insects upon which it feeds have largely vanished themselves.

That wasps fall into this category – that they too are tumbling in numbers – is not generally known. It’s not appreciated because their decline is a prime example of what’s known as the shifting baseline syndrome: each generation takes what it finds around it to be the norm. Thus, if you had a picnic this August attended by three wasps, that would be annoying enough, and you would probably not register the fact that 30 years ago, there would have been 10.

Yet such is the case. “Wasps have declined enormously,” said Matt Shardlow, director of Buglife, the Invertebrate Conservation Trust. “Going back to my childhood, in the Seventies and Eighties, on a sunny August afternoon you could get huge numbers of wasps in the garden, and that just doesn’t happen any more. I think what would be a very bad year for wasps then, would be a very good year for wasps now.”

The perception is not just anecdotal. Matt drew my attention to a study in the journal Ecological Entomology by Michael Archer of York St John University, which has had virtually no publicity, showing that populations of our two most familiar wasps, the common wasp Vespula vulgaris and the German wasp Vespula germanica, have suffered major losses, the most likely cause being “the increased use of pesticides acting directly by killing the wasps and indirectly by reducing their food resources”.

The last point about food resources is key. For wasps are predators. They are carnivores – as opposed to bees, which are vegetarians – feeding their grubs on other insects such as aphids and tiny caterpillars (they switch to carbohydrates such as the jam on our picnic tables in late summer when their grubs have grown).

At a tiny level, they could almost be compared to birds of prey; and their prey is vanishing. The decline of wasps, at the apex of their own food chain, is an infallible signal that a vast mass of insects underneath them is vanishing too, and that the whole system, which has worked perfectly for millions of years, is now in serious trouble.