Some bugs have a host plant, I recognised that this one was very similar in shape (the pronotum but mainly the scutellum) to one I have which is called Woundwort Shieldbug (Eysacoris venustissimus) which is what prompted me to search for the plant in your case. They are supposed to be specific to the plant, and I have seen them mating on Hedge Woundwort (Stachys sylvatica) which is native and I found some growing on the roadside at the front of my property. The plant has since spread and I have a large patch of it under the Horse Chestnut tree which in turn attracts a species of bee which isn't often seen.
Back to the story.
I have also seen the Woundwort Shieldbug mating on white deadnettle (same family), and found their nymphs on Fuchsias which are by my south facing wall. I found they do sometimes use other plants such as Fuchsias so yours might too. I haven't seen any real damage to the plants, and their numbers are small, I prefer to let nature do it's thing (preservation of all species is important).
