From New Scientist magazine, 29 July 2000.
by Stephanie Pain
Hate housework? Can't find a reliable cleaner? Try a slug
Hardly surprising, really. Robinson and his partner Lynne McNairn had chosen to live in an old, two-storey, brick-and-fibro house in Narraweena, a soggy suburb to the north of Sydney. The bedrock is so close to the surface that when it rains, water oozes out of the ground and turns the garden into a bog. Damp comes with the territory, and in a poorly ventilated bathroom, mould was inevitable. It was one long battle against the fuzzy fungus until, one day, Robinson decided to take on domestic help. He started with one, then three, and eventually a whole army of cleaners. They were small, cost only bed and board, and didn't use nasty chemicals around the house. They were slugs: a motley crew of striped ones, red ones and big, fat grey ones.
As a naturalist, Robinson is keen to experiment with biological controls of all sorts. Since he settled in Narraweena, he has offered houseroom to a whole menagerie of creatures in return for their doing a few chores. His ultimate aim is to build up a trouble-free staff of animals that can be left alone to get on with the job. Already, he has turned up previously hidden talents among some of the local fauna.
The slugs were his first employees. "Some slugs love mould. They thrive on it," says Robinson. "I noticed a few came into the house and headed for the bathroom. A friend of mine had seen slugs eating mould in his house so I thought I'd test it out." Worried that the molluscs would never make it across the vast expanse of carpet that lay between them and the bathroom, he gathered them up and carried them to their new home. "Lo and behold, it worked. They kept the mould down. They didn't get rid of it completely but we only needed to do a little work. They are particularly good at cleaning grout, silicone sealer and other hard-to-reach places," he says.
Slugs have a strong homing instinct, foraging in the damp night air and spending the deadly desiccating daylight hours in a cool, moist retreat. Robinson provided his new staff with comfortable lodgings in the shape of a little ceramic pot perforated with stars and crescent moons--the sort more usually used to waft perfumed oils around the place. "They soon learnt that was home," he says. Each night, the slugs crawled out of the moons and stars and slithered off on their fungal foray. At daybreak, they crept home where they were safe from bare feet and torrents of hot water. In the breeding season, the slugs took a break from housework, heading down the drain and out of the vent pipe to seek a mate in the garden. After a brief romantic interlude, some came back, unable to resist Robinson's increasingly furry shower curtain. Those that failed to return were replaced with new recruits from the garden.
Since he took on his first few slugs, Robinson has tried out several species, hoping to find the perfect home help. The leopard slug is a good mould-grazer, but tends to slip out of the bathroom at night to explore the house. "You might step on it during its nightly wanderings, so it wasn't ideal," says Robinson. The little striped slug--not so little at 3 to 5 centimetres long--was better. It has a healthy appetite for mould and goes about the job as energetically as a slug can. The red triangle slug, which can grow up to 10 centimetres, was a bit too picky. "It will eat mould but it won't go on the ground. It's good for shower curtains but won't clean the other parts of the bathroom." The best slug for the job turned out to be Limax flava, the much-maligned great grey slug familiar in European gardens and introduced to Australia. L. flava is a big, beefy slug, 9 centimetres at full stretch, so it eats a lot of mould. But it's also pretty sluggish, for want of a better word, and doesn't wander far at night, so there's little risk of finding one squashed into the carpet the next morning.
At one point, great greys, stripys and a young red triangle shared the workload and Robinson was more than happy with their efforts. They were efficient and didn't stain the carpets as cleaning with bleach did. Eventually, though, it was time for a new bathroom: that pink-and-grey just had to go. Freshly plumbed and neatly tiled in green and white, the new bathroom is airy and bright. The old plastic shower curtain has gone, replaced by a shiny, glass cubicle. "We do have a silicone strip around the shower tray which is hard to clean and the slugs do that brilliantly," says Robinson.
Even so, redundancies loomed. It was time to downsize the staff. The celestial slug house has gone, and the slimmed-down workforce consists of three small stripy slugs. "They are small enough to fit in the groove of the sliding door without getting squashed," says Robinson. "Occasionally they get fed up and crawl down the plughole, but generally they do a good job."
Robinson has been well and truly bitten by the slug bug and hopes other people will give them a try. "It's an alternative for those who can't be bothered scrubbing or who don't like chemicals," he says. "They don't remove all the mould, but they do keep it down to an acceptable level." For those who don't fancy the sight of fat grey slugs in the bath, he is working on a range of designer slugs in fetching bathroom colours. L. flava varies naturally from grey to yellow, and also comes in albino. "The yellow form is quite attractive," says Robinson. "And the white ones can be tinted by feeding them vegetable dyes--although you have to keep this up or they revert to white again."
Apart from the odd silvery trail up the bathroom wall and a few droppings that are easily swilled away during the morning shower, slugs don't have any real drawbacks--unless you collect vintage wines. "They like the mouldy labels," warns Robinson. "They eat them, and then you don't know what's in the bottle."
With Sydney's warm, damp climate--and especially on Robinson's boggy patch of land--there's plenty of work for a large household staff. Keeping down cockroaches, for instance. Roaches come in all sizes, from the thumb-sized Periplaneta species to the smaller but more persistent Blattella germanica. "They're a problem--for other people," says Robinson. His house is so well protected, he sees about one cockroach a month. The first line of defence is a colony of leaf-tailed geckos--prickly-looking lizards with flat, leaf-shaped tails. These particular geckos don't have sticky feet and can only cling by their claws to rough surfaces. They live outside on the brickwork, where they are active at night. "They form a sort of moat of geckos that insects have to get past before they can make it into the house," says Robinson.
Any that do get in risk an encounter with the "lounge lizards", secretive skinks that skulk by day behind the lounge (that's a sofa to non-Australian speakers). The skinks emerge in the evening to hunt a whole range of unwelcome guests, including cockroaches, spiders and silverfish. "You hardly notice they are there. But they'll eat anything that's moving on the ground," says Robinson.
Cockroaches might be unpleasant, but termites are a householder's worst nightmare. Given half a chance, they'll eat the house--unless something eats them first. In Narraweena, termites have a natural enemy in the little black ant. If the ants come across a band of termite workers, they'll follow them down into their galleries where they'll eat termites at every stage of development from egg to adult. Above ground, any termite king or queen setting out to found a new nest is fair game. If they land anywhere near the ants they're done for--and that's one fewer nest to worry about. Robinson and McNairn are happy to share their home with a few black ants in exchange for a termite-free house, although the ants themselves can become a nuisance. "They'll eat our food too--from the sugar to breakfast cereals--and they get everywhere. You might find them living in the teapot, for instance. But we tolerate them. They patrol the places a human cleaner can't get to," says Robinson.
Scuttling insects and stationary eggs are relatively easy to deal with, but in Australia it's hard to avoid flying insects, especially mosquitoes. Most people keep them out with wire screens. Robinson's insect screens are woven from silk and tailor-made by orb spiders. Webs on either side of the ramp leading to the first-floor entrance create an insect-screened corridor to the house. Golden orb spiders are best for this job. They build fairly permanent webs, and although they don't always build them in the right place or at the right angle, the webs can be moved into position by carefully detaching the supporting strands and fastening them to a more suitable twig or stem. Garden orb spiders do their bit too, but they have a serious drawback--they build a new web each night, eating the old one the following morning. "This means we sometimes walk straight into a web at night that wasn't there during the day," says Robinson.
There are plenty of pests left to keep a whole range of wildlife fed, from dragonflies to bats, to fish and frogs which live in the garden's pools and ponds, even insect-eating sundews and pitcher plants, which thrive on the boggy ground. And about this time of year, the anti-mosquito task force is swelled by the arrival of several species of Toxorhynchites--unusually large mosquitoes with glittering iridescent bodies and wings. There are dozens of species of Toxorhynchites around the world and they share one endearing habit: as larvae they have a voracious appetite for the young of other mosquitoes. The adult insects suck plant sap and nectar, not blood, and they lay their eggs in small pools, containers filled with rainwater, tree holes and even waterlogged footprints in the lawn. The offspring of other mosquitoes don't have much of a chance. A single Toxorhynchites larva can eat its way through 400 smaller mosquito larvae before it reaches adulthood. "Although we've still got plenty of mosquitoes, there are fewer than there might have been," says Robinson.
Apart from their battery of biological controls, Robinson and McNairn restrict their fight against pests to mechanical methods--squashing snails, for instance--or at most, sloshing ecologically friendly soapy water over bad infestations of scale insects. The result is a garden filled with native species, from mud-burrowing spiny crayfish to seven species of insect-eating lizard. Native honeybees, rescued from a fallen tree, nest in two hives that Robinson has provided, each potentially giving him a litre of lemony-tasting honey a year. Native wasps have moved into other artificial nest sites--and keep down harmful caterpillars. "We provide what the animals want, and they come," says Robinson. "And the more diversity there is, the less likely we are to have pests. Pests may get used to chemicals, but they never get used to being eaten."
And there's a bonus. There's always a ready supply of new additions to the household staff. "We'll probably never have a scrupulously clean and tidy house but we have one that's comfortable, entertaining and doesn't give us too much work."
For anyone thinking of following Robinson's example, it's probably best to check that it's OK with any other humans living in the house. Fortunately, McNairn shares Robinson's enthusiasm. "I like having the critters around," she says. "They make our life interesting, and generally you don't even know they are there. They just quietly get on with their jobs and every now and then you see one of the geckos or slugs and think, that's nice, they're still here."
Unless they are spiders, that is. "There was a bit of a
problem when a large banded huntsman spider I'd introduced to the
garden took up residence in a drawer," admits Robinson.
"When Lynne went to take out her favourite grey jumper, part of
it moved under her hand," he recalls. Her piercing scream
persuaded him to put the spider at the farthest part of the garden.
"It never returned," he says, "probably because its
sound receptors are still ringing."