The Cabbage White is native to Europe, North Africa and Asia, but has spread to North America, Australia and New Zealand.  It is a very cold-hardy butterfly, and can sometimes be seen flying during midwinter thaws as far north as Washington, DC.  It has one of the longest seasons of any butterfly, emerging from the chrysalis in early Spring and remaining active until the first hard freeze.  In areas where winter temperatures stay above freezing, it can breed year-round.

As their name implies, Cabbage Whites are white in color, though the undersides of their wings range from white to pale yellow and are often speckled with black.  Individuals often have black upper wingtips, and females have a black dot in the center of the upper wing.  Because of their simple coloring, they are sometimes mistaken for moths.

Cabbage White caterpillars are green, which affords them very good camouflage.  Unlike their larger cousin the Large Cabbage White, (Pieris brassicae), Small Cabbage White caterpillars are tasty to predators, so they keep to the undersides of the leaves in order to avoid being spotted.  Because they live on Brassicas, many of which are food crops, the caterpillars can be a crop pest.

Small Cabbage Whites are very strong flyers, and though they rarely range farther than 2 miles (6.2 km) or so, it is estimated that they can fly over 100 miles (160 km) over their lifespan.  They regularly fly to Britain from the European mainland, and when they were first introduced to Australia, they spread from Melbourne all the way west to the western coast (a distance of over 1,800 miles (2,900 km)) in only three years.