There are times when Nature seems to be nothing but a revelation of beauty and glory and divinity; when it seems utterly obvious that the Creator is not only a thoroughly good chap but one who takes a special pleasure in beauty.

I've been watching swallows, you see, and that tends to unsettle the mind. I was walking a sunken path, to my left an expansive field of green corn, and saw flying low, apparently for the simple pleasure of getting their tummies tickled by the tips of the corn stems, a small group of swallows lost in the wonder of their own agility.

It was a cheering sight in what looks like a frighteningly poor year for migrants. What is more perfect than a swallow? The effortless flight, the astounding speed and accuracy - earlier that day I'd been watching them, flying in and out of the stables, charging in through the small openings as if they intended to ram the inside walls and knock the building down.

A splendidly natty colour scheme, pale below and navy above, with the elegant touch of a red face mask. Pretty birds are expected to have drab voices, but not the swallow: a glorious jumbled twittering and a smart double-note announce arrival and departure at the barn door.

The swept-back, fighter-plane wings, the long tail streamers, the way they love curves and despise straight lines, the knowledge that they have travelled in sweeps and swerves all the way from Southern Africa: they look as if they have come here specifically to tell us that the run-stealers flicker to and fro, to and fro, that there is honey still for tea, that God's in His Heaven, all's right with the world.

Mind you, it's possible that an insect would see a swallow as something different - a ravening beast from Doctor Who, perhaps, or one of those unexpected monsters from a Ted Hughes poem that attack the sensibilities. But when we see a swallow, we human beings, at least, experience beauty and thoughts of the benignity of Creation lurk in every curving, twittering fly-past.

White relief

On the same walk, a small white butterfly, of the species known as small white. Butterflies seem to have been created entirely for the delectation of human beings: fluttering fripperies, apparently comprising nothing but colour, exquisite eye candy for God's people.

I stopped to watch, having a taste for small things, and a marvellous thing happened. The butterfly flew to a hawthorn, a white may tree in a great froth and lather of blossom. It stopped, basked and half-disappeared - white on white, a lovely creature conjoining with the flower that sent Proust half-mad with joy.

Would it be possible to paint such a sight without being sentimental? Is it possible that even a photograph of this conjunction could be unsentimental? Ben Nicholson gave us white circles on white backgrounds. Here was the same thing done lush, yet stripped of all self-consciousness.

Cowpat Venus

More small things. A group of handsome flies, about half a dozen of them on the sunny side of a dead oak - beetle-shiny bodies with transparent wings, chestnut brown at the base. I was pretty certain they were true flies, that is to say, of the order Diptera. That is as precise as seeing a mouse or a human being and saying “mammal”. Well, rather less precise than that - there are reckoned to be about a quarter of a million species of Diptera, less than half of which have been described.

I rang my friends at the charity Buglife to see if they could narrow it down a little more, and they cut the possibilities down to two: Tachina grossa, or Mesembrina meridiana. The first are parasites: the larvae hatch out in caterpillars and eat them from the inside, starting on non-essential organs to keep their victim fresh for as long as possible. The second of these, also known as the noon fly or noon-day fly, is merely disgusting. The adult rises like Venus from a sea of cow shit. The eggs are laid in a cowpat and the larvae have their being in this lovely stuff before emerging gloriously as adults. This, I eventually worked out, was the oak tree basker. There is a fine herd of red cattle just the far side of what we in Suffolk amusingly call a hill, so there are plenty of potential nurseries.

A glorious fly in a glorious creation. The noon fly's fellow Diptera are immensely versatile creatures; among many, many other things, they are the vectors for malaria, dengue fever and encephalitis.

William Blake asked of his Tyger, did He who made the Lamb make thee? You might also ask, did he who made swallows and butterflies make shit-flies, caterpillar scoffers and sundry disease bearers? I wouldn't for the world tell anyone what to believe in or, for that matter, what not to believe in: I merely suggest that we consider every aspect of the evidence - in all its teeming, disturbing, intoxicating complexity - before jumping to conclusions.

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