The Small White (Pieris rapae) is a small- to medium-sized butterfly species of the Yellows-and-Whites family Pieridae. It is also commonly known as the Small Cabbage White and in New Zealand simply as white butterfly. The names "Cabbage Butterfly" and "Cabbage White" can also refer to the Large White.
It is widespread across Europe, North Africa and Asia and has also been accidentally introduced to North America, Australia and New Zealand where they have become pests on cultivated cabbages and other mustard family crops.
In appearance it looks like a smaller version of the Large White. The upperside is creamy white with black tips to the forewings. Females also have two black spots in the center of the forewings. Its underwings are yellowish with black speckles. It is sometimes mistaken for a moth due to its plain-looking appearance. An adult's wingspan is roughly 32–47 mm (1.25–2 in).
Description taken from Wikipedia: http://en.wikipedia.org/wiki/Small_White
+0.25 exposure compensation in ACR