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Flies are like sheep: They seem to follow their leader, without it being clear which of them is their leader. This was my conclusion from watching flies approaching the flypaper I hung in my bedroom recently.

Our house in the country is invaded by insects every year, a different species, or at most two species, taking it in turns, as if by rota. One year it was the turn of Cydalima perspectalis, the box tree moth, which covered the walls as graffiti artists cover concrete. This moth is a species that was introduced, like electric cars, into Europe from China, spread very rapidly, and wiped out Buxus shrubs more thoroughly even than electric cars are wiping out the European car industry.

There are several methods to control this moth, whose population tends to explode when conditions are right. There are chemical insecticides, moth sex hormones that confuse the adult moth worse than contemporary children’s books confuse children about their sexual identity, nematode worms that parasitize the moth, and bacteria that excrete a toxin specially toxic to caterpillars of the species. But as in politics, no victory over the moth is final, and like discredited ideas, it is bound to return in a few years’ time.

This year it has been the flies (again) and the stink bugs. The latter is the brown marmorated stink bug, the scientific name being Halyomorpha halys. This is another import from China, though I hesitate to allege any malicious intent on the part of the CCP. This slow-moving insect aggregates in houses by the hundreds or thousands to escape the winter cold. It flies blindly into things with a characteristic little smacking noise, and its flight emits a buzzing that irritates sensitive persons such as I. Worst, of course, is the smell it emits when frightened, annoyed, or inadvertently squashed. The unpleasant odor it emits can linger; it consists mainly of two aldehydes called trans-2-octenal and trans-2-decenal. These chemicals have been tested for their bactericidal properties, particularly on antibiotic-resistant Staphylococci (a menace in hospitals), so one day Halyomorpha halys may prove to have been a blessing to humanity. For the moment, though, it is a pest, which we control by the advised method, the vacuum cleaner. There are fewer of these insects now, but, like financial scandals, they continue to emerge.

As to the flies, I now understand why for many centuries, indeed for two millennia, people believed in the theory of spontaneous generation, that is to say the theory that life emerges spontaneously from nonliving matter (as, presumably, it must once have done).

However many times I thought that I had cleared the room of flies, they always returned, but I could never find the place from which they emerged. One minute they weren’t there, and the next they were. This was the kind of experience that led the great naturalist Aristotle to conclude that life was spontaneously generated, a belief that Louis Pasteur was concerned to refute more than 2,000 years later. It is salutary to remember that the endurance of a belief is not an infallible guide as to its truth.

I used an old-fashioned method of ridding the room of flies: flypapers. Gone are the days when flypapers containing arsenic were soaked by disgruntled spouses who disposed of their husbands or wives by feeding them the resultant tasteless, odorless solution. Nowadays, they, the flypapers, consist of rosin, the sticky residue of pine resin after evaporation of the resin’s water content, applied to tape. Flies are attracted to rosin, but once they land on it they are trapped physically.

The packaging told me that the flypapers contained no insecticide, and the website of the company that made them claimed that it was “ecoresponsible” and took into account all the environmental, social, economic, and ethical effects of its activities. Naturally, I am not in favor of companies behaving immorally, for example by unmercifully exploiting people or by carelessly polluting the area round their own factories, but I wish we could sometimes have a rest from the epidemic of high-mindedness that afflicts our times and which, by reaction, introduces wicked thoughts into our minds.

Actually, the new flypapers are rather cruel, to flies if not to spouses. They don’t kill the flies directly, but only by exhaustion and inanition. The flies are stuck on the paper until they expire, which as I have observed can take more than 24 hours, even more than 48. I touch their wings or their legs and see them move. I feel a certain pity for them.

I do not want to make myself out to be some kind of benevolent biophilic mystic, a sadhu. While I think that a fly considered individually and close-up is a creature of beauty, in any numbers, they are (to me, at least) repellent. But even when there are many dead flies trapped on the flypaper, I cannot help but think of William Blake’s poem when I focus on one of them:

Am not I
A fly like thee?
Or art thou not
A man like me?

This, of course, gives rise to an intimation of our mortality and tenuous hold on the thread of life:

For I dance
And drink and sing:
Till some blind hand
Shall brush my wing.

Or as the Duke of Gloucester in King Lear puts it, “As flies to wanton boys are we to the gods; they kill us for their sport.”

Can, or do, flies suffer? Certainly they struggle to free themselves from the flypapers, as if they valued their freedom and their lives, but such behavior could be, and presumably is, purely mechanical, that of mere automata. Curiously, though, when first I hang the flypaper in the room, the flies are wary of it. They approach it and then fly away, and approach it again, and fly away again. They seem to be attracted and wary at the same time. But once one of them is trapped, seemingly by chance, by flying too near the rosin or landing on it, a floodgate is opened, and the pioneer is soon followed by many more.

I suppose you could call the first fly an influencer.

Theodore Dalrymple’s latest book is On the Ivory Stages (Mirabeau Press).