The Hawthorn Shield Bug (Acanthosoma haemorrhoidale) is a species in the family Acanthosomatidae.
It resembles the Birch Shieldbug (Elasmostethus interstinctus), but the triangel on its back is green whereas the triangel of the Birch Shieldbug has more colours, sometimes with yellow or even orange or red.

1st photo: In my yard, Hilversum, The Netherlands, 29 August 2012
2nd photo: In my yard, Hilversum, The Netherlands,  25 July 2019