What is a Slug

Every gardener loathes their presence but, “What exactly is a slug?” I hear you enquire...

Black slug on a leaf

Black Slug  (Arion ater)

Gastropods and molluscs

Well, slugs belong to the large animal group called gastropods, from the Latin ‘gastro’ (stomach) and ‘poda’ (foot). You’re probably more familiar with the garden varieties of slugs and snails, but gastropods have diversified to colonise most habitats on the planet; from woodlands to deserts, and from high mountains to the deepest rivers. The most abundant forms are the marine gastropods such as sea slugs and snails.

But not content with being such a hugely diversified animal group in their own right, gastropods themselves belong to the even bigger family of molluscs, from the Latin ‘molluscus’ (thin shelled). It’s estimated there’re around 100,000 species of mollusc, and with the exception of the gastropods, all other classes are marine dwellers.

The giant squid, octopus, and cuttlefish are all members of the marine mollusc family, along with the more obvious forms such as clams, oysters, muscles, and other shellfish.

Snail without a shell

A slug is basically a snail without a shell, and did in fact evolve from the snail. This dispels the popular myth that snails came after as an attempt by a well meaning angel to cover up the fact that God made slugs when he wasn’t paying proper attention.

“I know...  I’ll give them a little house. That’ll make them look prettier.”

To this day, most slugs still have the remnants of that shell – called the ‘mantle’ – which is usually internal. A few species actually do carry a small external shell.

Losing its shell may seem rather an evolutionary dumb move as it did provide some degree of protection, but the slug had a cunning plan. You see, it can now slither effortlessly through the spaces between the soil; an almost impossible feat when carrying a cumbersome shell on your back. This opens up a whole new subterranean world for the slug to inhabit; a world safe from many surface dwelling predators that still prey on the snail.

Slug slime

A slug gets around using a sort of ‘muscular foot’, and because this is quite tender and the ground quite rough, it secretes a kind of mucus (slime) over which it glides. This slime is hygroscopic, meaning it absorbs moisture and becomes more efficient. It’s the reason why slugs prefer wet conditions; needing to produce excessive slime in drier weather can cause dehydration.

Useful tip

Don’t attempt to wash slug slime off your hands with water. Instead, rub them together and it soon turns into little balls that you can discard.

Slugs need to keep moist or they’ll dehydrate and die. It’s another reason why they’re more active during wet weather. It’s also why they’re largely nocturnal; to avoid the heat of the day.

Fascinating slug fact

Cluster of tiny slug eggs

Cluster of tiny slug eggs

Did you know; slugs are hermaphrodite. They have both male and female sex organs! The slug can mate with itself if necessary, and both sexes can produce clusters of tiny pearl-like eggs.

I guess that’s why there are so many of the little bugg beasties around!


Handy hint

Turn logs, stones, and pots to expose any eggs to the elements...  and to visiting wildlife.

Most slugs are harmless

Britain is home to around 30 species of slug and, contrary to popular belief, most cause little damage in the garden. Some are even beneficial, feeding mainly on decaying vegetation. There are only really four species that do all the damage, so it’s good to learn to recognise these few bad slugs.

Some species, such as the Field Slug, are surface dwellers, munching their way through your tender plants. Others, like the Garden Slug, also attack below ground, with potatoes and tulip bulbs being particular favourites.

A staggering 95% of the slugs in your garden are living out of sight below ground at any given time, which is why the totally organic nematode slug control methods are rapidly gaining popularity among gardeners. One particular nematode species is a natural slug parasite that also lives below ground.

The Gardener’s Year

The Gardeners Year: book cover

The Gardener’s Year

Dad always said to me, “Gardening is tied to the seasons, and being a successful gardener is all about planning ahead.”

You need to know what you should be doing, when, and why, so what needs doing in April?

Read The Gardener’s Year by Alan Titchmarsh and get month by month advice that shows you how to keep your garden growing its best throughout the entire year.

The Gardener’s Year
Find out more
...

More gardening year books


What do you want to do now


Did you
 know?

A slug smells with its body


The Gardener’s Year

by Alan Titchmarsh

The Gardeners Year: book cover

What to do in April?

Gardening is intimately linked to the seasons, and being a successful gardener is all about planning ahead.

Alan Titchmarsh gives you month by month advice and shows you what you should be doing, when, and why.

The Gardener’s Year
Find out more
...


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