SNAILS AND SLUGS

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Without snails and slugs, the glow-worm cannot exist!   So, to safeguard the glow-worm, we have to look after snails.  

There are thousands of different snails in the world, they are a very successful creature.  They once lived in the sea, but adapted to survive on land, although many are still aquatic.  Slugs are snails who have evolved a little further, and have lost their shell because it is no longer needed.  They have tougher skins and more slime than snails.  There are also snails with tiny shells that they cannot get into.  In a few more centuries, perhaps they will have evolved enough to have lost their shells completely too.

   Advantage of shells

• protect the snail from different weathers, this includes, sun and wind that dries their body out.  
• give protection against predators.
• provide a safe 'home:' snails can sleep in their shell over night.
• shells grow with the snail, he doesn't have to moult, as insects do, so has constant protection.
• a tiny shell called a protoconch grows in the egg so that the snail has protection from day one.

Disadvantage of shells

• weight, slowing the snail down.
• cumbersome, top heavy.
• the snail needs a larger living space.
• a supply of calcium carbonate (chalk) is needed to make the shell.