The number of known species of butterflies throughout the world has been put at about thirteen thousand, and it has been suggested by Dr. Sharp that there may be nearly twice as many still awaiting discovery. Dr. Staudinger in his "Catalog" gives a list of over seven hundred kinds of butterflies as occurring in the whole of the Palæarctic Region. This zoological region embraces Europe, including the British Islands, Africa north of the Atlas range of mountains, and temperate Asia, including Japan. The entire number of species that can by any means be regarded as British does not exceed sixty-eight. Even this limited total comprises sundry migratory butterflies, such as the Clouded Yellows, the Painted Lady, the Red Admiral, the Camberwell Beauty, and the Milkweed Butterfly; and also the still less frequent, or perhaps more accidental visitors, the Long-tailed Blue and the Bath White. Again, the Large Copper is now extinct in England, and the Mazarine Blue does not seem to have been observed in any of its old haunts in the country for over forty years. The Black-veined White is also scarce and exceedingly local.
The majority of the remaining fifty-seven butterflies may be considered natives, and of these about half are so widely distributed that the young collector should, if fairly energetic, secure nearly all of them during his first campaign. The other species will have to be looked for in their special localities, but a few kinds are so strictly attached to particular spots, that a good deal of patience will have to be exercised before a chance may occur of obtaining them.
A few remarks may here be made in reference to the names and arrangement adopted in the present volume.
As will be adverted to in the descriptive section, the English names of our butterflies have not always been quite the same as those now in general use. There has, however, been far less stability in scientific nomenclature, and very many changes in both generic and specific names have been made during the past twenty years, more especially perhaps within the last decade.
Genera are now founded by some specialists on characters which formerly served to distinguish one species from another, whilst other authorities merge several genera in one upon certain details of structure that are common to them all.
Patient research into the entomological antiquities has revealed much important material, some of which may furnish a new interpretation of the Linnean classification of Lepidoptera.
The discovery of the earliest Latin specific name bestowed upon an insect, is a labour which entails a large expenditure of time and requires fine judgment. Great credit is therefore due to those who undertake such investigations, the result of which may tend to the establishment of a fixed nomenclature in the, probably not remote, future, although it sadly hampers and perplexes students in the meanwhile.
All things considered then, it has been deemed advisable not to make many changes in specific names, and to retain the old genera as far as possible. The arrangement of families, genera, etc., will be found to accord with that most generally accepted both in England and on the continent.