The Small White is one of the commonest and most abundant of the butterflies. Its area of distribution extends from the
British Isles and
North Africa as far as
Japan. It has been introduced even to
North America,
Australia,
Hawaii,
New Zealand and
Tasmania. It is a dangerous pest in some places. In central
Europe two to three generations occur not strictly seperated in time, whereas there is only one generation in populations living in high mountains. The spring form is easily distinguished from the summer one. It is usually smaller with less distinct pattern.
A great number of different forms have been described. The female seldom lays more than one or two eggs at a time, the total number being 150-200. After hatching, the caterpillar devours its egg shell. Then it starts feeding on the surface of the leaves, making irregular holes in them. It pupates after the fourth moulting. The pupal stage lasts 7 to 10 days- in hibernating pupae up to ten months. It is easy to breed these caterpillars in captivity and they are often used in scientific experiments. In nature the caterpillars and pupae are often infested with parasites of the orders Hymenoptera and Diptera.