What's in a Name
Today's manner of naming plants and animals goes back to the Swedish physician and botanist »Carl von Linné (1707–1778) who wrote under the pen-name Carolus Linnaeus. It was he who introduced what is known as the binary or binominal nomenclature – binominal because according to Linné's method of naming each living being is given a binomen, that is a two-part name, just like in humans who have a given name and a surname. In science, the order is the Chinese or Bavarian one: surname first (Mao), given name second (Zedong). Both parts are in neo-Latin, with a large share of Greek and other morphemes, many of them purely artificial.
The primary component of the binomen gives the genus, the secondary part is the name of the species. Thus Homo sapiens denotes the species sapiens within the genus Homo. (The only congenerics we know of are defunct ones like Homo erectus, Homo habilis and Homo neanderthalensis.) Both parts are usually italicized; moreover, the genus is capitalized. As sometimes the same specific names are used for animals of different genera, orders or classes, they are unambiguous only as long as they are preceded by the genus, at least in an abbreviated form. For example, P. brassicae stands for Pieris brassicae, the Large Cabbage White, and distinguishes it from M. (= Mamestra) brassicae which is an owlet moth. If a third component (also italicized) is appended, it denotes a subspecies. All further – infrasubspecific – taxa which some authors have seen fit to introduce, like 'form' or 'aberration,' have no taxonomic standing and are considered more of a nuisance than a help today.
In scientific publications, often the 'author' of the subspecies, species or genus (or some higher taxon) is added, that is the person who named it and also the year when he published the original description (OD). A growing number of non- and semi-scientific publications nowadays omit the author. Nabokov called it "a deplorable practice of commercial origin which impairs a number of recent zoological and botanical manuals in America". (Lep21)
Thus 'Lycaeides argyrognomon longinus Nab., 1949' reads as "the subspecies longinus of a lepidopteron of the species argyrognomon, belonging to the genus Lycaeides first described by Nabokov in a study published in 1949." The expert reader ought to know that the genus Lycaeides belongs to the large butterfly family of Lycaenidae, called Gossamer Wings in the United States.
Scientific names are not just names. If the purpose were only to give each animal or plant an unambiguous name of its own, a single name or perhaps even a number would do. True, the name is to denote a particular animal, but it also is to define the animal's place among the living beings. Linné's is a Systema naturae, a system of nature, not a mere inventory. Naming is classifying. Each name is like the end of a path name in a computer file system. When Linné and his coevals grouped certain species under the roof of a common genus, and certain genera under the roof of a common family, and so on, they did so because all of nature presented itself as a system of morphological similarities and dissimilarities. The system is a strictly hierarchical one. There is no way a species can belong to more than one genus, or a genus to more than one family, even if certain overt features seem to suggest it. No butterfly can be partly a lycaenid and partly a satyrine. Linné's binominal nomenclature ensures that each organism not only has a unique name all to itself but that the name indicates its unique place in the system of the living.