Sandy's Garden ... Oniscus Asellus

What am I?

I am a small terrestrial crustacean from the monophyletic suborder Oniscidea within the isopods with a greyish segmented body. I live in damp habitats and have a segmented, dorso-ventrally flattened body with seven pairs of jointed legs and specialised appendages for respiration. Like other peracarids, my mother carried me, as a fertilised egg, in her marsupium, through which she provided me with water, oxygen and nutrients. (Adapted from Wikipedia). What am I?

Another clue? My scientific name is Oniscus asellus and I am a member of a very large extended family. Lots and lots of my immediate relatives live in the United Kingdom; and four other branches of my family are almost as common in the UK as my immediate family is. We … my immediate family … live pretty much anywhere in Northern and Western Europe, as far east as Ukraine, as well as in the Azores and Madeira; my family has also emigrated to the Americas very successfully. If you consider my extended family, there are probably five thousand different branches of it; and we live in as many continents as you can shake a stick at.

I have lots and lots of common names … "grandad" in some parts of Scotland, “granny grey” in South Wales, “butcher boy” around Melbourne in Australia and many hundreds more … but in Northern Ireland, New Zealand, Australia and Scotland I am usually called a “slater.”

Falkirk Herald gardening guru Sandy Simpson

I expect that’s what you call my cousins … or me, for that matter … when you find us in your garden, concealed under stones, logs and in other suitable, damp, hidey-holes.

These are the places where we like to pass the day, coming out at night to do what slaters do, which is mainly feeding, growing and mating. Oh, and by the way, lots of people call me a common wood louse; I think that’s very demeaning, don’t you?

Well, there are plenty of Oniscus asellus right here in my garden in Polmont. The closest that I am aware of are within five metres of where I am sitting, enjoying a mild, damp afternoon beneath some of my pots and planters. They do sometimes venture into houses, but are unlikely to survive long indoors unless they find a nice damp place in which to shelter.

I hope there aren’t any in or under my house for, although they are not likely to do any damage … they don’t burrow into wood or spread infection … their presence is a sure sign of damp. They don’t usually do much damage in the garden either, where they contribute significantly to breaking down dead plant material, thereby assisting in the composting of plant detritus.

They are sometimes blamed as vandals who damage soft fruit when it’s more likely that the original damage was done by slugs, snails or caterpillars and the slaters are actually helping to clear up the residual mess. Since they are such good recyclers of plant debris …and are present in large numbers in a typical garden … we should welcome them when we discover them sheltering under some garden feature, apologising for disturbing their daytime doze.

Slaters, being nocturnal feeders, find their food by taste and smell. They themselves are regarded as food by the likes of toads, centipedes and some species of spiders and beetles; and they can grip a surface very tightly with their fourteen feet, making it difficult for a predator to dislodge them. They are gregarious if not exactly sociable, almost always being found in what I might call ‘colonies.’

And they have been around for a very long time, having left their original watery homes in favour of damp ground quite literally hundreds of millions of years ago. Contrary to popular belief, slaters are not insects but are crustaceans, kissing cousins of crabs and shrimps.

So, gardeners, let your primitive friends help you; and cooks who enjoy shellfish, I understand that Oniscus asellus casserole is distinctly unappetising!