Secondly think of the "Invasions" of spiders over the English Channel at
times.......the young spiders climb up plants/trees etc then let out
thread
till it is caught by the wind which carries them off to a new area,
sometimes 40 or 50 miles away, No reason why Red spider cant do the
same.

There is - though it is an arachnid, it is not a spider, it's an acarid.

Emrys made the same mistake. It's a mite, not a spider - but a spider-mite.
Mind you, it does spin a very fine silky 'web', so the point about
paragliding might still be valid, I suppose.

Andrew