About Lepidoptera
Butterflies belong to the order of insects called Lepidoptera, which also includes moths. It is generally accepted that there are 59 breeding species of butterfly in the British Isles; three of these are migrants from Europe, and one is only found in Ireland. Other species such as Long-tailed Blue, Queen of Spain Fritillary and the continental form of the Swallowtail occasionally breed in Britain.
Over 2400 moth species have been recorded in the British Isles, of which about 800 are macro-moths.
Both butterflies and moths are key indicators of the state of the environment because of their short life-spans and complex lifecycles. Each stage of their lifecycle (egg, caterpillar, chrysalis, butterfly) has specific environmental needs in order to survive to the next stage, reach adulthood and produce the next generation. Their presence or absence provides a rapid and undeniable indication of the health of the environment.
Most butterflies live for between three and seven days as adults (this can be demonstrated by mark-and-release trials in the field). They suffer a consistent mortality rate which is independent of their age; an individual only has a 75% chance of surviving until the next day, probably because of predation at night. The exception to this is those species which over-winter as adults; these can live for nine or ten months.
Butterflies and moths are in trouble in Britain. The report The State of the UK's Butterflies 2015 found that 76% of the UK’s resident and regular migrant butterfly species declined in either abundance or occurrence (or both) over the past four decades. Ten-year trends show that 52% of species decreased in abundance and 47% decreased in occurrence.
The destruction and deterioration of habitats as a result of land-use change (e.g. intensification of agriculture, changing woodland management) are still considered the prime causes of long-term decline among habitat specialist butterflies in the UK.
Two species of butterfly are regarded as being critically endangered in Britain, the Large Blue and High Brown Fritillary, and a further eight are endangered: Chequered Skipper, Wood White, White-letter Hairstreak, Black Hairstreak, Duke of Burgundy, Pearl-bordered Fritillary, Glanville Fritillary and Heath Fritillary.
Moths are also in decline. The report The State of Britain's Larger Moths 2013 shows clearly that the total number of larger moths recorded in the national network of Rothamsted trap samples decreased by 28% over the 40 years from 1968 to 2007. Two-thirds (227 species) show decreasing population trends over the 40 year study and over one-third (37%) of the species decreased by more than 50%.
The widespread decline of Britain’s butterflies and moths is a clear signal of potentially catastrophic biodiversity loss caused by human impacts on the environment. Moths, and to a lesser extent butterflies, comprise a substantial part of Britain's biodiversity and play important roles in food chains and as pollinators. Their decline will have knock-on effects on the birds, bats and mammals, which depend on them for food, and shows widespread degradation of our environment caused by habitat loss.