THEY breathe through their legs, can process heavy metal and can even provide us with a tasty lunch. ENHS member GAIL CRANE visits the complex world of the humble woodlice and explains why we should treat them as best friends.
Next time you lift a flowerpot and are tempted to get rid of woodlice hiding beneath, you may want to re-consider. Those much-maligned creatures could turn out to one of our best friends.
Believe it or not, woodlice are considered bio-indicators of a healthy garden and are mostly beneficial. They feed on decomposing plant material breaking it down into a form easily digestible by protozoa, fungi and bacteria, making it easy for them to convert it into nitrates, phosphates and other vital soil nutrients.
Woodlice are one of the few creatures that can live in contaminated ground. They are capable of processing heavy metals such as cadmium, arsenic and lead by ionising them in their gut, thus preventing toxic matter from leaching into ground water. They effectively de-contaminate the ground.
Woodlice also play a vital role in the food chain as a food source for many other creatures such as shrews, toads, centipedes, spiders and flies.
For certain birds, such as robins, wrens and pied fly catchers, woodlice provide an abundant supply of the calcium they need to form their eggs. A woodlouse contains more than three times more calcium than a snail shell.
There are more than 5,000 known species of woodlouse worldwide. We have thirty species here in the UK, five of which are common in our gardens, including the common woodlouse and the pill woodlouse.
All woodlice have a segmented exoskeleton with seven sections, each with a pair of legs. They vary in colour from grey to pink. They are not insects but terrestrial isopod crustaceans, so they are related to crabs and shrimps.
No longer aquatic, most species of woodlice left the oceans millions of years ago. However, they still need a coating of water on their legs, which is where their lungs are, in order to breathe. They spend their days in damp places and only come out at night to feed.
Woodlice have acquired a huge diversity of local names, some quite affectionate. On Exmoor and in West Somerset, they may be called lucky-pigs, chucky-pigs, granferjigs or cheesebugs. In Devon they are known as chiggy-pigs, in Cornwall, gramersows.
Slater, wood-pig, potato-bug, sow-bug, stinky-pig and Johnny-grump are just a few of their many local names. The pill woodlouse, which rolls in to a ball when threatened, is often known as pill-bug, or roly-poly.
Some of these common names relate to their smell. Woodlice convert their urine into a strong-smelling ammonia gas which they expel through gill-like structures - a link to their aquatic past.
There are still maritime woodlice species, such as sea slaters. A further link to their marine crustacean ancestry is their copper-based blood: they eat their own faeces, called frass, in order to recycle the copper in their diet.
The females are excellent mothers. Eggs are produced in spring and retained inside her body until they hatch. For several days, the newly-hatched offspring, called mancas, are cared for in a brood pouch, or marsupium, on the underside of the female. She continues to watch over her young until they mature.
These mancas shed their outer shells several times as they grow until, by late summer, they become adults. After over-wintering, the fully-grown young begin to reproduce the following year. A woodlouse will produce several generations a year and may live for two to four years.
A surprising and probably little-known fact is that, like their relative the saltwater prawn, they are edible and an excellent source of protein. Just pop them in boiling water and enjoy! Another benefit of these under-rated creatures?
So, though you may not fancy them for lunch, and they may be partial to the odd strawberry, woodlice have a lot going for them. On balance, they are hugely beneficial to us and to the environment.
Maybe we should ‘live and let live’ and allow them to exist in peace beneath their flowerpots.