AdventiveA species which arrives in the British Isles with the direct assistance of an external vector, without which it would not be present. Adventives are species that one would not expect to find in this country, either through inadvertent migration or through any other natural means of dispersal, with the exception perhaps of the most extreme meteorological event or possibly the transportation of a stage in the life cycle in a highly unlikely but natural means (e.g. an ovum or larva being transported upon the foot, bill, or plumage of a migratory bird). Adventive species are usually transported to the British Isles by man's intervention (e.g. Geranium Bronze, or pests of imported food products). Such species may be regularly recorded in the British Isles but would not ordinarily arrive without direct or indirect intervention by man. Adventive species may also reproduce in the British Isles, forming temporary colonies that are dependent upon favourable climate and suitable larval food plant for survival.
MigrantA species which arrives in the British Isles, sometimes in numbers, as part of an established migratory pattern and that may, or may not, complement resident populations. The British Isles is within the normal range of the species. The British Isles may, however, be at the outer limits of the Palaearctic distribution of a given species. In such cases, temporary populations may establish themselves annually in the British Isles and complete an entire life cycle, although this is usually truncated by the onset of winter in mainland Britain and populations rarely persist beyond one season. Small populations may become established and survive one or more winters in the most favourable conditions but this is exceptional, and dependent upon unusually favourable climatic conditions (e.g. Clouded Yellow). Migrant butterflies of a given species may not arrive in the British Isles every year; however, when conditions are favourable they may be present (and reproduce) in significant numbers.
OviposturingGoing through the apparent motions of ovipositing without actually laying any eggs.
ResidentA species with continuously present populations in the British Isles. Resident species complete their entire life cycle in the British Isles. Resident populations in the British Isles may be bolstered by annual migrations from continental Europe (as is the case with the Large White); however, these additional numbers are not essential for the species' continued presence and survival in the British Isles. The populations of resident species are therefore self-sustaining.
VagrantA species which does appear on occasion, but whose normal migratory range does not include the British Isles. The term Vagrant embraces butterflies that wander or are 'blown off course' from their regular migration route that does not include the British Isles. Vagrant butterflies may also arrive here as a result of specific meteorological conditions which precipitate unusual dispersal from populations that are resident in neighbouring countries (e.g. Long-tailed Blue). Vagrant species may reproduce in the British Isles if the climatic conditions and available habitat are favourable; however, colonies are always transitory.