I spotted two of these shield bugs while out for a walk along a track, we call the bog road, close to our house. It is a Hawthorn shield bug.
This is not it’s final adult stage. The female lays eggs that hatch into nymphs. These are wingless and crawl among plants and feed. They go through a number of instars. It takes about six weeks to reach an adult. They will hibernate during the winter months as adults. They feed mainly on hawthorn berries (hence their name), though this one was feeding on rowan berries.