A while ago, I was proudly showing a friend a barrow-load of my best garden compost. She recoiled squeamishly: "It's moving!" And indeed it was. Red brandling worms, dust-coloured woodlice, leggy spiders, shiny centipedes and plenty of other crawly or slithery things were threading their way through its moist particles. And those were just the obvious individuals. Invisible to the naked eye were millions of microbes: a frenzy of soil creatures, gobbling and reproducing and dying - and enriching the good, brown humus in their busy process.
I didn't tell all this to my new-to-gardening friend - who's bravely overcoming a dread of the scurrying spiders in her greenhouse. She might turn her back on gardening forever if she knew that every spadeful of healthy soil was host to such a seething multitude.
But as any seasoned gardener knows, most of the invertebrate creatures that share our gardens are our co-workers in cultivating our patches. Without their help in recycling dead plant material we would be metres-deep in undissolved vegetable matter. And, without their convenient appetites for other critters, we would be up to our ankles in throngs of aphids, slugs, snails and other plant-destroyers.
But some of our gardening allies are pretty scary-looking, moving with frightening swiftness through our communal territory. Spiders have far too many athletic legs, as well as unnerving, questing sense organs (known as "palps") and poison-injecting fangs. Centipedes - the amber-coloured express trains of the invertebrate world - race along startlingly on just 30 galloping feet. And the devil's coach-horse, a lean, malevolent-looking beetle - as the name suggests - rears up its hind-quarters like a scorpion and opens its large jaws when disturbed.
Yet these are chums, every one of them, devouring hundreds - or even thousands - of sap-sucking, bark-munching, leaf-crunching insects. True, we may find their fast, powerful and unpredictable movements somewhat alarming, but it is this same brutal hustle that makes them successful predators of the slow-moving vegetarians that are their quarry.
Among the fastest of the garden carnivores are the many species of ground beetle. These range in length from just a few millimetres to over two centimetres, and are insatiable eaters of the eggs and larvae of cabbage and carrot root flies, and of slugs, caterpillars and aphids. Many are nocturnal and hide during daytime under pots and stones - a pity, because they are sometimes mistaken for vine weevils and are bumped off by the over-wary gardener. Ground beetles are dapper fellows, often shiny and usually black, brownish or slightly metallic; they set off at top speed when you accidentally uncover them. Vine weevils, on the other hand, are drab things, with dull, brownish-grey bodies and they're never in a hurry to get anywhere.
Of course, our best-loved beetle is the cartoonish ladybird, wearing not just the familiar black-spotted red livery, but also black-spotted orange, and white-spotted brown. Both the adults and their odd, reptilian larvae dine mightily on aphids, while some species also consume mealy bugs, scale insects and spider mites.
Hoverflies are also prodigious aphid-eaters, although the adults, in their mock wasp suits, feed only on pollen and nectar. It is the tiny, greyish, almost slug-like larvae that knock back about a thousand aphids each before entering the next stage of their life cycle. Just a few will clean a greenfly-infested plant in days. There's a savage satisfaction in watching a dun-coloured larva lift an insect into the air, suck its innards, cast it away and pick up the next one.
Even common wasps are valued garden assistants, plucking other insects off plants to feed to the young. It is only in late summer and autumn, when the offspring-rearing is done, that they become an annoyance, feeding off sweet fruits, sugary soft drinks and jam. And miniature parasitic wasps (harmless to humans) lay their eggs on the grubs and eggs of certain moths, which are then used as grisly, living meals by the wasp larvae.
No, it's not a pretty life out there amongst the carnivorous invertebrates, but without them, our gardens would be host to biblical infestations of plant-ravaging pests. Far more acceptable are the gangs of earthworms, brandling worms, bristletails, springtails and other soil inhabitants who placidly gnaw their way through tons of garden detritus. Even the unlovely woodlouse - which has a not-undeserved reputation for snacking on seedlings - is in the main, a good citizen. The bulk of this crustacean's diet is made up of decayed plant material.
The earthworm, however, is the most heroic of garden workers. It takes in soil, small stones and organic matter before excreting them in a mixture that - according to Charles Darwin - "mingles the whole intimately together, like a gardener who prepares fine soil for his choicest plants".
Jane Powers is at: jpowers@irish-times.ie