Spring has arrived, which means more time in the garden. On a sunny afternoon in March we lifted the lid off the sandpit and peered in, for the first time in a while. Spiders scattered to the edges as the sunlight hit their previously dark, cool hiding place. The sand was criss-crossed with tracks from the adventures of some unknown invertebrate.
I was doing a quick spot-clean, picking out a few dried-up slugs, rescuing a couple of panicked earwigs, and suddenly realised I was holding a balled-up woodlouse in my hand. It struck me that I couldn’t remember having seen a curled-up woodlouse for years, and that I used to see many more. Why was that? Do some curl up and not others? I was instantly curious and wanted to find out more about these little armoured invertebrates who are under every rock and plant pot, and must number in their thousands in every small urban garden.
This one was showing no signs of waking up, sadly, and I remembered that woodlice don’t survive well in dry environments. It had probably got stuck in there and couldn’t get back up the steep sides before drying out. I was just lowering my hand to show my son, when the antennae started to twitch! The woodlouse uncurled its body, legs waving in the air, expertly flipped over and began scurrying towards the edge of my hand.
‘We have to put her back where she lives!’ instructed my two-year-old.
But where? She was an outsider. I realised, now, that she looked different from the other woodlice in our garden. The level movement of her shiny armoured back, with fourteen scurrying legs underneath, put me in mind of seven cartoon people running along as they hide under an upturned boat.
The other woodlice hanging around were in contrast a lighter grey, their matt armour flattened out near the sides, a jagged edge to their bodies. But hoping for solidarity among woodlouse species, we placed our little survivor among the busying grey bodies in the damp shadows of our garden hedge.
Eat, prey, love
Solidarity is called for, as theirs is a story of woodlice vs the world. These little troopers are prey for pretty much everyone else. Plentiful and peaceful, they are the rabbits of the invertebrate world.
Woodlice are gobbled up by centipedes, rodents and spiders – in particular Dysdera, also known as the woodlouse spider, which specialises in eating woodlice. I found one of these amazing arachnids underneath our recycling bin last summer. With its bright red legs and thorax, and bulbous pale abdomen, I had never seen anything like it before, and learned that their powerful jaws are specially adapted for piercing a woodlouse’s tough armour.
That’s one reason woodlice are good to have around: they are an important part of the food chain. All these predators go on to become food themselves for larger birds and mammals.
Your loveable ‘land lobster’
There are lots of other reasons to like woodlice. They are useful, but also fascinating and charming. Zoologist Paul Richards sings their praises in an excellent two-part webinar for the Tanyptera Project. Paul clearly has a great affection for the invertebrates he calls ‘land lobsters’ or ‘house shrimps’.
Woodlice might look like insects, but they are actually crustaceans, more closely related to crabs. Woodlice are isopods, with hard exoskeletons and jointed limbs. Their deep sea relatives, the wonderful giant isopods, can grow to a foot in length, but other than that they look very much like their land-dwelling cousins.
Our terrestrial isopods (Oniscidea) have adapted brilliantly to life on land, having evolved the ability to walk and breathe air. But woodlice haven’t shaken their watery roots. They can regulate water loss (osmoregulation) to some degree, but need to stay close to moisture.
Their love of dark damp places also makes woodlice interesting to play with. I remember doing an experiment in primary school science class where we put woodlice in Petri dishes which were half dark and half light, or with a wet tissue on one side, and watched them migrate towards their preferred habitat. It’s this need for moisture that makes woodlice huddle together.
So if you find woodlice in your house, says Paul, move them out again. They don’t want to eat your floorboards or furniture, and they might be doing you a favour just by being there, alerting you to a damp wood problem you need to take a look at. But probably they’re lost, and would much rather be relocated back outside. They like it cool, damp and dark.
Cleaning up
The Royal Horticultural Society confirms that our ‘house shrimps’ are indeed not pests, far from it. Woodlice clear up decaying plants and recycle nutrients, and do us no harm whatsoever.
I start wondering what our parks and gardens would look like without woodlice and other detritivores. Would we be wading through piles of sticks and leaves, like in the Carboniferous period before wood-eating microbes arrived on the scene? Woodlice play an essential role in recycling dead plant matter and turning it into protein for animals higher up the food chain. We need them.
I wonder, then, why they are not universally liked. Is it the ‘lice’ in ‘woodlice’ which gives them a bad press, as the thought of other lice makes our skin crawl? Is it the ‘wood’ in ‘woodlice’ which leads some people to think they will eat good wooden furniture?
Monkey peas
Not all people dislike them though. They have an affectionate place in our culture and language, with an astonishing number of different colloquial names for these humble isopods, many of them referring to their snuffly pig-like quality.
So, what do you call a woodlouse? Cheese-pig, potato bug, Granny Grey, pill-bug, slater, or monkey pea? There are maybe 176 different names, according to one count.
Paul also cites their appearances in poetry, music, art and even medicine (crushed woodlice have been used to cure stomach aches); and food, including an 1885 recipe for woodlouse sauce. But be warned: too many can have a diuretic effect, earning them the Dutch name ‘pissebed’.
How is a woodlouse like a koala?
It’s not a joke, it’s the most wonderful woodlouse fact of all. Because they still need to lay their eggs underwater – which could be tricky for a terrestrial isopod – the female has a watery brood pouch for her eggs, from where her babies can hatch out. The pouch is adorably named a ‘marsupium’.
When a baby woodlouse hatches out in its mum’s pouch, they are already a miniature version of their adult self. Unlike koalas, they will shed their skin as they grow; half a skin at a time, to help protect themselves.
Woodlouse detective
I’m surprised to learn that there are over 60 different species of woodlice in the UK. Some of these have been imported in plants and are found in greenhouses, but 40 or so species are found outdoors. You can find woodlouse identification tips on the British Myriapod and Isopod Group (BMIG) website.
Our sandpit survivor is a common pill woodlouse (Armadillidium vulgare), one of the larger species. They roll into a ball as a defensive move, a strategy which also conserves water. This might explain how our friend made it out of the sandpit alive.
Most of the others mooching around our garden are common rough woodlice (Porcellio scaber), with flatter bodies which cannot roll into a ball. This gives the species their own defence mechanism though, as they can flatten their bodies down to the ground like limpets, making it trickier to pick them up.
A little orange woodlouse I found in a plant pot recently may have been a juvenile of the same, as colour can vary within the species. And this mottled brown woodlouse seems to be a common rough woodlouse too (it’s the same size, and also has a continuous body outline, which is one of the BMIG’s identification tips).
It hadn’t really occurred to me before that there could be several different species of woodlouse living in my garden, or how many different colours they can be. Go and take a look in your own garden or park, and you’ll probably be surprised by the variations too. It’s fun and easy looking for woodlice as they are reliable, turning up almost everywhere. Check anywhere damp and dark: under rocks, plant pots, logs and leaf litter.
I’ve had a glimpse of a great wide world of woodlouse spotting, and will be keeping my eyes open for some of the more specialist species in future, like the gorgeous ant woodlouse (Platyarthrus hoffmannseggii) which is white and found in ants’ nests, or the very large sea slaters (Ligia oceanica) which can be found in coastal areas and measure over an inch long.
I think I’ve realised, too, why I saw so many more curled-up woodlice when I was a child. Simply, I was noticing them more, as I’m now doing again.
There is something reassuring about the woodlouse; resilient and timeless. As Paul said, you could remove the tree cover in a forest and the woodlice probably wouldn’t notice for some time. With some leaf litter and moisture they get along just fine. In a world where so many species are struggling with the effects of climate change and habitat loss, it’s been good to get to know these hardy little survivors who’ve been here since the dinosaurs, and will be around for many millions of years to come.
Find out more
- British Myriapod and Isopod Group: www.bmig.org.uk
- For children: we’ve been enjoying Woody the woodlouse who forgot how to roll into a ball
- Watch Paul Richards’ talk on YouTube:
small world 