Shield Bug Mates

Caught these two in the act. They were on the garden trellis supported Ivy. I may be completely wrong but I think they are mating rather than taking a back to back defensive attitude, or maybe both at once. I believe that the one on the left is the male since it appears to be pushing with it's hind legs whereas the one on the right appears to be taking a resistive to sliding motion stance. I am no biologist, perhaps somebody in the community can advise. I dithered about uploading it, should this be tagged as 'Adult Content', or should I not have uploaded it at all? There was negligible cropping with this image; just enough to centralise the subjects left to right.