en Green-veined white
Pieris napi is a circumboreal species widespread across Europe and Asia, including the Indian subcontinent, Japan, the Maghreb and North America. It is found in meadows, hedgerows and woodland glades but not as often in gardens and parks like its close relatives, the large and small whites, for which it is often mistaken.
The eggs are laid singly on a wide range of food plants including hedge mustard (Sisybrium officinale), garlic mustard (Alliaria petiolata), cuckooflower (Cardamine pratense), water-cress (Rorippa nastutium-aquaticum), charlock (Sinapis arvensis), large bitter-cress (Cardamine amara), wild cabbage (Brassica oleracea), and wild radish (Raphanus raphanistrum), and so it is rarely a pest in gardens or field crops.
The generations vary with location, elevation and season. In northern Europe there are two or three generations from April to early September. In warmer areas and in some good years there is a fourth generation. In southern Europe there are three or more partially overlapping generations from March to October. (source: Wikipedia)