Mike photographed this late flying Green-veined White at Southbourne Undercliff on 5/11/17.
Whites can be quite confusing to ID, but the black markings on the tips of the fore-wing establishes this butterfly as a Green-veined White given the time of year it was seen.
Similar species are female Orange Tip, and Small White. However all have very different underside patterns which when seen makes for easier ID.
Text books suggest in England this butterfly has two broods, April-May and mid June-July, but that further south in Europe it has 2-4 overlapping broods March-October.
Does this suggest that this butterfly could be an immigrant?