A Hawthorn shield bug climbs on the leaf of a Dogwood.
The hawthorn shield bug, Acanthosoma haemorrhoidale, is a common European shield bug. Its chief food is haws, the fruit of the hawthorn tree, but adults can overwinter on a diet of leaves, and individuals can be found on many potential food plants, including pedunculate oak, sessile oak and whitebeam.
They may grow up to 17 mm long, and are camouflaged in shades of green and brown. Like many so-called "stink bugs", they may release unpleasant odours when disturbed.
The hawthorn shield bug is found across Europe, from Portugal to Russia, and is common in the southern part of Great Britain. Its distribution appears to be spreading north, being only reported as far north as Birmingham in 1892, but having now extended its range to Northern England and even the Scottish Highlands.
Description taken from Wikipedia: http://en.wikipedia.org/wiki/Hawthorn_shield_bug