Does anyone know what the little blackish/dark greyish insects are that
sometimes live in soil (usually around sickly plants)? They jump about a
bit if disturbed (they're not fleas). I've always thought they were
springtails but I now realise these are white. Do the little jumpy things
cause damage? If they do, how do I get rid of them and prevent them from
arriving in the first place?

TIA
--Alison