Why do slugs die when sprinkled with salt?

You're dehydrating them. It's actually an asshole thing that you're doing. They aren't hurting anything.

Slugs need to be saturated in order to survive. The salt absorbs a lot of the water from their bodies and makes them dry up, thus killing them. Its the same idea why if you are lost at sea you don't drink the salt water. It'll just make you more thirsty and dry up your body faster.

i have no idea i think salt has a chemical that reacts with the slug's slimy body. I used too drown fly's untill they died and poured salt on its body and it would end up digging itself out but if i dident put salt on it it would stay dead

Dehydration.

The salt is hygroscopic so it 'draws' the water from the slug.

yeah like snails...good question...and then why dont snails when cooked..like escargo...not melt anymore when salted?..hmmm