Even the most ecologically-orientated gardeners sometimes harbour murderous intentions towards slugs. When they devastate our crops we might spurn slug pellets in favour of beer traps, parasitic nematode worms that eat them alive or simply crushing them under foot - but do all slug species in gardens deserve to die? Occasionally I read claims that there are good slugs and bad slugs, and it’s certainly the case that the smaller, most numerous species do the most damage to vulnerable garden plants. The Little book of Slugs , published by the Centre for Alternative Technology, nominates the field slug (Deroceras reticulatum), the keeled slug (Milax budapestensis), the garden slug (Arion hortensis) and the black slug (Arion ater) as the worst offenders but from time to time I read claims that some species are harmless to garden plants. How true these claims are is open to question - so much of what’s printed in wildlife gardening books seems to be simply copied uncritically from older sources that may well have been wrong – but next spring I plan to do some tests of my own to see if there is any slug species that can be trusted to spend the night in a plot of young, succulent lettuce plants. The most likely ‘good slug’ seems to be the great grey or leopard slug Limax maximus – like this one (above) that’s spending winter under loose bark on an old log in my garden. Edward Step FLS, in his book Shell Life: An Introduction to the British Mollusca, published in the early years of the 20th. century, ventured the opinion that this species “declines all foods containing chlorophyll” but was particularly partial to “kitchen garbage that is not green, such as fat, bread, meat scraps and milk”. More gruesomely, he found that this species was a cannibal, eating the remains of fellow slugs that he’d killed after finding them in milk jugs in his kitchen. Whatever the great grey’s taste in food, it certainly has some very exotic mating habits which you can watch at
http://www.youtube.com/watch?v=GSW9kWIRCOQ
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