The Wood White, Leptidea sinapis (L.) is a member of the subfamily Dismorphiinae which has only two other European representatives. It is very locally distributed in Britain and over the last 200 years its range has become greatly restricted. It is now confined to certain parts of southern and western Britain where it occurs in discrete and often isolated populations. However, the larvae of L. sinapis feed on a variety of leguminous plants, many of which are common and widespread. A detailed ecological study has been carried out on L. sinapis for several years. This paper summarises the information obtained about its biology, behaviour, habitat utilisation, distribution and status. The possible reasons for its decline in Britain are also discussed. Animals and man; Disturbance by man; Commercial activities; Nutrition; Diet; Reproduction; Reproductive behaviour; Life cycle and development; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Host parasite relationships; Ecology; Population dynamics; Habitat utilization; Land and freshwater zones; Palaearctic region; Europe; United Kingdom Leptidea sinapis (Pieridae); Forestry; Woodland management changes, population effects; Food plants; Larval, also adult flower visiting; Oviposition; Food plant age preference & deposition sites; Life cycle; Hymenopteran parasites; Apanteles & Trichogramma; Prevalence; Acrolyta; Apanteles & Trichogramma (Hymenoptera) parasites; England; Population changes; Woodland management effects; Britain; Habitat preference; United Kingdom & Ireland compared; Republic of Ireland; United Kingdom; Past & present distribution, status & biology Apanteles (Braconidae ); Acrolyta (Ichneumonidae ); Trichogramma evanescens (Trichogrammatidae ); Lepidopteran hosts; Leptidea sinapis; Rate of parasitism; Prevalence; Leptidea sinapis (Lepidoptera); England; Northamptonshire; Prevalence on lepidopteran host