The number of moth species living in Britain is changing all the time as some species become extinct here and new ones colonise from continental Europe or further afield.
During the twentieth century, 62 resident moth species (micros and macros) were lost from Britain. Examples included the Essex Emerald, Lesser Belle and Viper's Bugloss. Three other species have not been seen for a number of years and may also now be extinct here (e.g. Orange Upperwing, Bordered Gothic and Brighton Wainscot). Although the loss of moths from Britain is of grave concern, all of these species still occur in other parts of the world; they have not become globally extinct.
In contrast, 89 species colonised Britain successfully during the twentieth century. For example, the Light Brown Apple Moth, a micro-moth native to Australia, was first recorded breeding in the wild in Britain in Cornwall in 1936. Since the 1980s it has expanded rapidly and is now recorded widely across England and Wales, and has been reported recently in Scotland and Ireland. It is a generalist with a wide range of larval food-plants, but many other recent colonisers are specifically associated with non-native plants in our gardens and parks, for example the Firethorn Leaf Miner on Pyracantha shrubs and Blair's Shoulder-knot on Cypress trees.
Many other new moths have been seen in Britain for the first time in recent years. Over 100 new species have been recorded from the year 2000 onwards, but most of these have occurred only as occasional immigrants or accidental imports so far. Over 20 moth species have become established in Britain since the Millennium, including macro-moths such as Langmaid's Yellow Underwing, Sombre Brocade, Blair's Mocha and Clancy's Rustic. The latter was first recorded in 2002 at New Romney, Kent, but has established itself very successfully since then. It has spread along the east and south coasts and colonised parts of Suffolk, Essex, Sussex, Hampshire, the Isle of Wight and Dorset. This rapid spread is continuing and there have been recent records from Somerset, Devon and Cornwall.
Perhaps a less welcome event has been the colonisation (in 2002) and rapid spread of the Horse Chestnut Leaf-miner, a micro-moth that causes unsightly damage to the leaves of Horse Chestnut trees.