As its common name suggests the gorse shieldbug (Piezpdorus lituratus) is, indeed, a shield-shaped bug that is associated with gorse and also broom. Those who follow my nature notes will know I caution against trusting common names but here is a case where you can! As it feeds on gorse and broom it can be found anywhere these plants grow but the most likely place to find it is on the Dorset heaths. Although quite common they get lost in the gorse and one does not see them very often.
This is an interesting species as the adults vary in colouration throughout the year. They hibernate as adults and the first to emerge in spring can be seen in March and the early specimens are green with blue edges to the wings and they have reddish antennae. Those later in the year in September and October have a purple triangle on the wing cases and purple antennae! It seems the purple colouring wears off over winter during hibernation. The purple triangle can be a bit of a problem with identification as other species of shieldbug display similar markings.