Looking at the rings of the 4 x 4 post I'm thinking it was about 25mm long not including the antenna, but I felt it was larger initially (of course I had my eye in the viewfinder and the lens 2 inches away, this was a very tolerant subject, so maybe shooting insects in the late afternoon of a cold winter day is better?)
The 'thing' sticking out of it's posterior throws me, so I'm not sure what this is.
The arrangement of three dots in a triangle and the one on the section behind it's head, and it's face make me think it is a wasp, but I can't find anything like it in the photo guide.