The picture is off Google, I put a 1ft square piece of cardboard on floor, encouraged it onto cardboard and took it outside. The wife was hiding in caravan.Yes, seen many over the years and glad to, they are good news in they feed on maggots and slugs.
Don't provoke it or it might fire a nasty smelling fluid at you, and if you invite it, they will bite with those rather large jaws.
Arched as in your photo is because it has gone into the defensive mode.
Without provocation, it is not going to trouble you and as said is really "your" friend.