Confidence: I'm as sure as I can be.
Notes: Where the antennae reaches the head, there is a gentle curve which narrows it down to M.rubra or M.ruginodis. It has a rounded top to the petiole, so is M.rubra (as opposed to the flat top of ruginodis). It looks like a queen as well because of the dark patches on the thorax. I guess it was over 5mm