An introduced butterfly species that all vegetable gardeners know as a pest of cabbages, broccoli, etc.
They have an erratic flight usually low over vegetation.
Their green larva is pictured below.
Helping with control of this butterfly is the parasitic Chalcid Wasp. The picture below shows the pale yellow cluster of the cocoons of this wasp's larvae, having emerged from the larva of the Cabbage White. Do not destroy them or the Cabbage White larva they have emerged from. They will later hatch into Chalcid wasps. That caterpillar is already doomed to die.
Similar butterflies: Pearl Whites Elodina sp. lack the black spots on the forewings; the migratory Common Albatross Appias paulina looks similar but is larger and faster flying.
You probably know this caterpillar as a pest of your Brassicas
A male Cabbage White feeding on Salvia
A male Cabbage White feeding on a Wallflower
Parasitic Chalcid wasp, Pteromalus puparum, cocoons on a Cabbage White caterpillar.