What is a Slug

“So what exactly is a slug?”  I hear you enquire...

Gastropods & molluscs

Well, slugs belong to the large animal group of gastropods – from the Latin ‘gastro’ (stomach) and ‘poda’ (foot). Although you’re probably more familiar with the garden varieties of slugs and snails, gastropods have diversified to colonise most habitats on the planet; from woodlands to deserts, from high mountains to rivers, and the depths of the deepest oceans. In fact, the most abundant forms are the marine gastropods – sea slugs and snails.

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). There are estimated to be 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 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 him a little house. That’ll make him look prettier.”

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

Why the slime?

A slug moves around using a sort of ‘muscular foot’. Because this is quite tender and the ground quite rough, it secretes a kind of mucus (slime) over which it glides. Rather like laying down its own silvery path over which to travel. This is one reason why slugs prefer wet conditions – their slime is hygroscopic, meaning it absorbs moisture and becomes more efficient. Needing to produce excessive slime in drier weather can cause dehydration.

Why not create a slug barrier around your cherished plants using something uncomfortable and abrasive such as grit or broken eggshells.

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

Fascinating fact

One fascinating fact is that slugs are hermaphrodite – having both male and female sex organs. The slug can mate with itself if necessary, and both produce clusters of tiny eggs. I guess that’s why there are so many of the little bugg beasties around!

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

Most slugs are harmless

Britain has 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. In fact, there are only really four species that do all the damage, so it’s good to learn to recognise these few ‘baddies’.

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 level, with potatoes and tulip bulbs being particular favourites.

What do you want to do now?

• Recognise the bad slugs
  Find out which slugs you don’t want in your garden.
• So many slugs
  Why Britain is the slug capital of the world.