The green-veined white butterfly is often mistaken for the small white. The distinguishing feature is, of course, the green veins. This example was visiting the flowers of a burdock growing by the River Wye in Herefordshire. Helpfully, the sex of the green-veined white can be determined by the spots on the forewing - the female has two and the male only one.
photo © T. Boughen Camera: Olympus OMD E-M10