Elasmucha grisea Parent Bug
A medium-sized reddish shieldbug with a black and white connexivum. There is usually an obvious black patch on the scutellum.
This species overwinters as an adult, emerging and mating in the spring. The smaller male dies soon after, but the female surives for some time, brooding the eggs and young larvae, which feed on birch and alder. New adults may be found from August onwards. Common and widespread across Britain and Ireland.
Info from British Bugs