The Heather Shield Bug is one of many varieties of shield bug. It is normally found in wet heathland or moorland, and feeds on beetles associated with heather (such as the heather beetle). Most insects develop in stages, these bugs have several stages from nymph to adult, these stages are called 'instars'. The one here is actually a nymph, and will look quite different when it's fully grown - it will have more of a shield shape. The pale bands on its legs are characteristic of this species.