Two Common Slater Species Living in My Garden: Armadillidium vulgare and Porcellio scaber

The Two Common Species of Isopods Living in My Garden Armadillidium vulgare and Porcellio scaber 

When people think about garden creatures, they usually think about insects, spiders, worms, birds, or perhaps lizards.  However, some of the most common animals living quietly among the leaf litter are not insects at all. 

Isopods are a large group of crustaceans that includes familiar garden animals such as slaters, woodlice, pill bugs, and roly-polies.  Although they live on land, they are more closely related to crabs and prawns than insects. 

To help with a little basic nomenclature: Isopod is the scientific group.  Slater, woodlouse, pill bug and roly-poly are common names used for various terrestrial isopods in different parts of the world.

I've always had plenty of slaters in my garden, but it wasn't until I started looking at them more closely that I realised I wasn't looking at just one kind.  Two species in particular are extremely common here: Armadillidium vulgare and Porcellio scaber. 

Both species play an important role in breaking down organic matter, turning dead leaves and plant material into nutrients that can return to the soil.

When I was a child, these animals were commonly called "wood lice".  Common names vary between regions.  Where I live in Australia at the moment, 'slater' is commonly used.  While 'isopod' is a correct scientific term, it refers to an entire order of crustaceans rather than just the familiar garden species. 

Finding isopods in my garden

My garden in the Canberra region has plenty of hiding places for isopods: under mulch, beneath pots, in compost, around old plant material, under rocks, and in areas where the soil remains moist.

At first glance, many slaters look very similar.  However, if you look closely, you start to notice that several different types can be living in the same garden. The two most common species here are Armadillidium vulgare and Porcellio scaber.  

I decided to keep small colonies of both species so I could observe them more closely and try to selectively breed for interesting colour variations. 

Interestingly, neither species is native to Australia.  They were introduced, presumably accidentally, and likely several times.  Now that they are established, they are widespread and unlikely to disappear.  We have a few native isopod species, but they are less commonly seen in my garden.  

Colony of rough slaters Porcellio scaber

Are slaters insects?

No.  Despite often being found alongside insects in gardens, slaters are not insects.  They are terrestrial crustaceans.  Their distant relatives include crabs, prawns and lobsters, although you wouldn't expect to find a slater scuttling around a rock pool.

This surprises many people because slaters are usually found in the same places as insects: underneath mulch, among fallen leaves, in compost, under pots, and around decaying plant material.  They are small, have lots of legs, and are often grouped together with the other tiny creatures we find in the garden.

However, slaters are much more closely related to animals such as crabs, prawns, and lobsters than they are to beetles, ants or flies.  They are crustaceans that have adapted to life on land, although they haven't escaped all the constraints of being aquatic animals.

Slaters breathe using modified appendages called pleopods.  These function rather like gills, which helps explain why they are so strongly associated with damp environments.  This is why they are usually found in cool, damp places where they can keep their bodies moist.  It is also why you often find large numbers of them under logs, rocks, pots, mulch, and compost.

Their need for moisture is also why they are such useful members of the garden ecosystem.  Rather than being pests that invade the garden, they can help to recycle organic material by feeding on dead leaves, rotting wood and other decaying plant matter.

So while they may look like tiny garden insects at first glance, slaters are actually small land-dwelling crustaceans quietly performing the same kind of recycling role that their marine relatives perform in aquatic environments. 

Difference between Armadillidium vulgare and Porcellio scaber

One of the easiest ways to tell these two species apart is by looking at their body shape, movement, and how they respond when disturbed.

Feature	Armadillidium vulgare	Porcellio scaber
Shape	Rounded	Flatter
Rolls into ball	Yes	No
Movement	Slower	Faster
Appearance	Smooth, domed	Rougher texture

Armadillidium vulgare – common pill bug

Armadillidium vulgare is probably the garden isopod most people recognise.  When disturbed, it can curl itself into a tight ball, which is why overseas it is often called a pill bug or roly poly.  

The ones in my garden are mostly a dark gunmetal grey colour.  Many also have small yellow markings along the sides of their bodies.  Some are lighter, sort of honey coloured.

Armadillidium vulgare some rolled up

The yellow markings seem to occur naturally in my population, and some have far more yellow than others.  At this stage I am treating them as normal colour variation rather than a separate colour form, but it is interesting to see how much variation occurs in this population.  I am keeping the ones with the most yellow for breeding, to see if I can select a highly coloured line of them. 

Unlike some other isopods, A vulgare is quite slow moving.  When I disturb leaf litter, they often respond by curling up rather than quickly running away.  I like the looks of these ones, they have a cute round shape.  I enjoy the interesting coloured dots that sometimes appear, and I also like the ones that are entirely grey, I'm not sure which I prefer.  

When I was a child I kept A vulgare in a little container with some earwigs.  They fascinated me.  I remember one year I looked under a rotting log and saw my first Porcellio scaber, and I was perplexed.  I didn't realise they were different, and thought it was just A vulgare that was somehow defective and could not roll into a ball.  Over the next year or so, P scaber went from an unknown entity, to being the dominant and most seen species in that area.  

Wild coloured Armadillidium vulgare

Porcellio scaber – rough slater

Porcellio scaber is another very common garden isopod.

Compared with Armadillidium vulgare, it has a flatter appearance and cannot roll completely into a ball.  Instead, it relies on speed and hiding when disturbed.

Various aged rough slaters

The Porcellio scaber in my garden are mostly grey, with some individuals showing mottled grey or brown patterns.  Some are almost white, while others are a mix of grey, brown, white, and orange, all on the same animal.  I've even once found an albino individual in my garden.

I also found one particularly unusual orange Porcellio scaber among the local population in my garden. I kept it and have started a small breeding experiment to see whether the colour is inherited. I'll be documenting that experiment separately, because I think this little orange slater deserves an article of its own. 

Grey and brown slaters and an orange slater Porcellio scaber

Are slaters good or bad for the garden?

Usually neither. They're part of the normal garden ecosystem, although large numbers can sometimes cause problems for vulnerable plants.

Like many garden creatures, the answer depends on the situation.  Most of the time, isopods are reasonably beneficial.  They feed heavily on decaying plant material and are part of the community of animals involved in breaking down organic matter.

Occasionally, large populations may nibble very soft seedlings, burrow into strawberries, or even damage healthy plant material. In a healthy garden they are generally part of the natural nutrient recycling system.  

Why I am keeping garden isopods

One of the things I enjoy about gardening is influencing the small ecosystems that develop over time.

Just as I experiment with unusual plants, perennial vegetables, and fermentation, keeping these isopods gives me another opportunity to observe a small piece of nature more closely.

Although keepers usually buy brightly coloured exotic isopods, I decided to begin with the two species already thriving in my own garden and see if I could breed my own fun coloured ones or albino lines.  They are hardy and well adapted to local conditions so I don't need to mess around with heating their enclosure.  I like the natural variation already present in wild populations, and I wonder how colourful they could become with a little selective pressure.

I hope to learn more about these small but important garden inhabitants, particularly the natural colour variation in my local populations and whether any of these unusual colours can be selectively bred.

For me, part of the fun of keeping these slaters is seeing what happens. I don't really know yet how successful the colour breeding experiments will be, but if I end up with healthy captive-bred colonies that are large enough to share, I may occasionally make some available.

I list things I have grown, propagated, or bred on my monthly For Sale page, so that's where any available isopod cultures will appear.