All plants and animals in the world, whether living or fossil, are classified in a system of scientific names that is accepted universally and is regulated by an international code of nomenclature (the science of naming organisms). The most basic system of classification is called binomial nomenclature, whereby every plant and animal is identified by a unique two-part name consisting of a genus name and a species name. This system, developed by the Swedish botanist Carl von Linné (Linnaeus), was first applied to butterflies in 1758. All butterflies, including skippers, were placed by Linnaeus in a single genus (Papilio) and given species names in this genus (e.g., Papilio antiopa Linnaeus is the Mourning Cloak).
Since the time of Linnaeus, butterflies have been arranged into many hundreds of genera (plural of genus) to better show their relationships: the Mourning Cloak is now known as Nymphalis antiopa (Linnaeus). These butterfly genera, like those of all plants and animals, are arranged into a hierarchical classification that classifies plants and animals into superfamilies, families, subfamilies, tribes, genera, species, and subspecies. Most of these categories are subjective, and different specialists may disagree on how inclusive or restrictive they should be. For example, the differences between the former butterfly families Satyridae, Nymphalidae, Danaidae, Heliconiidae, and Libytheidae are now recognized by most researchers as being relatively trivial when compared to the differences between other families of butterflies, so the recent trend is to treat each of these groups as a subfamily within the family Nymphalidae.
The scientific name of each species is followed by the name of the person who proposed the name, and the author's name is given in parentheses if the name was proposed in a different genus than the one now used. For example, Nymphalis antiopa (Linnaeus, 1758) was proposed by Linnaeus in 1758, but in a genus other than Nymphalis; in this instance, it was in the genus Papilio. Where the date of a publication in which a name was first proposed is actually different from the date printed in the publication, the corrected date is shown in square brackets; there are many examples of this in older butterfly names.
There has been general agreement among systematists (scientists who study evolution and classification) that butterflies should be grouped into two superfamilies: Hesperioidea for skippers and Papilionoidea for the "true butterflies." Also most of our butterfly species are well defined and firmly established through years of research and debate. In some instances, however, several "species" may still be combined into a single species, or species "split" into additional species as further research adds to our understanding of butterflies. More rarely, species new to science are still being discovered and described. Most of the controversy that persists in butterfly classification is in arranging geographical variation in butterflies into "subspecies" and in defining the limits of some genera and species. Some difficulties with genera, species, and subspecies are discussed in detail below.
A generic name is used to associate a group of closely related species. Since the limits of a genus are subjective, there has been disagreement among specialists as to whether some groups of butterflies should be placed in a single genus or arranged in a larger number of smaller genera. There was a tendency in the 1960s and 1970s to subdivide genera into smaller genera that were frequently defined on relatively trivial characteristics. The need for many small genera can be alleviated by using the categories of subgenera and species groups; these two categories are most frequently used by the specialist to develop a classification that gives a higher resolution to details of how the species are related without having genera that can only be recognized by the specialist.
Through many years of research and debate, the limits of most genera have been established and accepted by butterfly researchers, and many small "genera" were eliminated in the 1980s as a more conservative approach to generic classification became established. Twelve generic names still remain controversial in that they continue to be "split" or "lumped" by different workers. Unfortunately this is usually done without explanation, so we have included below a brief discussion of these twelve genus-group names to explain our usage of them. They are discussed in the order in which they appear in the text. Our usage and a comparison with several frequently used reference works are summarized in the table below.
The two smaller species of Nymphalis, our milberti and European urticae (Linnaeus), have been segregated into a separate genus (Aglais) by some workers. Aglais is well defined by several peculiarities of the genitalia (e.g., elongate penis, long saccus). The trouble is that without Aglais the genus Nymphalis can only be defined by its lack of the Aglais peculiarities, suggesting that Aglais might be a highly modified (derived) group within Nymphalis. Higgins (1975: 175) suggested Nymphalis could be defined by the loss of brachia in the genitalia (a process on each side of the genitalia above the valve) otherwise present in many other butterflies, including Aglais and related genera. The brachia, however, are not actually lost in Nymphalis, but are partially fused to the dorsal margin of the valve; in Nymphalis vaualbum the valve-brachia fusion is similar in degree to that in Aglais. In fact, the Compton Tortoiseshell (Nymphalis vaualbum) is a critical species to understanding relationships within Nymphalis. The Compton Tortoiseshell combines characteristics of the genus Nymphalis with some aspects of the commas (genus Polygonia); it has the wing shape and genitalia structure typical of Nymphalis, but there is a white comma mark on the underside of the hindwing, the head of the larva has a pair of branched spines on the top like those along the body (head spines are lacking in other Nymphalis), and the larva has branched middorsal spines on abdominal segments one to eight (the spine is absent on the first abdominal segment in Aglais and from the first two segments in other Nymphalis). Since head spines are also present in buckeyes (Junonia) and a complete set of abdominal spines are present in buckeyes and the genus Vanessa, the two larval characters are interpreted as being originally present in Polygonia and Nymphalis and subsequently lost in all but the most primitive Nymphalis (i.e., the Compton Tortoiseshell). Many
species of Nymphalis, including our californica and the European urticae and polychloros (Linnaeus), have definite traces of a yellow comma mark. The result is that the two species of Aglais are more closely related to other Nymphalis than is the Compton Tortoiseshell; thus Nymphalis, with Aglais excluded, is not a natural group. If Aglais is maintained as a separate genus, then the Compton Tortoiseshell would require a separate genus as well. We include all of these groups in Nymphalis.
Species are defined as individual organisms and populations of organisms potentially capable of interbreeding. Most butterfly species in Canada are well defined and easily identified. In some instances, however, the limits and identity of species can be confusing. For example, the Spring Azure (Celastrina argiolus (Linnaeus)) and the Mustard White (Pieris napi (Linnaeus)) have both been treated for many years as single species that occur throughout most of Eurasia and North America. Recent research has shown that both are species complexes with several species involved; the number of species, their defining characteristics, and their geographical ranges are still imperfectly known.
Similar confusion exists in other groups, especially among some blues, sulphurs, marbles, and swallowtails. In other instances, populations that are currently treated as geographical subspecies of a single species may in fact be distinct species, with supposed zones of hybridization actually being variation that superficially looks like hybridization. Some of the greater fritillaries (Speyeria) are examples of this phenomenon.
A third type of problem in defining species is seen in groups such as fritillaries (Boloria and Speyeria), sulphurs (Colias), blues (Euphilotes), and hairstreaks (Callophrys subgenus Mitoura). In these groups different populations may come together in some areas and behave as distinct species with little if any hybridization, while in other areas their ranges come together and they interbreed freely. These populations fall in between the species and subspecies categories and our treatment of them varies with the individual circumstances. For example, we treat Callophrys rosneri and C. barryi as separate species because they remain separate where they occur together in British Columbia, although they are reported to hybridize extensively in parts of Oregon.
The "line" between distinct species and geographical and foodplant forms within a species forms a grey area where there is no "right" answer in some situations. For practical purposes, we draw a line through this grey area, but it is important to recognize that it is there and that the populations may vary in their distinctness, both structurally and genetically, geographically and through time.
The correct name for a species is the oldest name that has been proposed for that species. In some instances a name may be in use in North America and an older name for the same species may be discovered in the literature. This is especially true of our northern species, where names in the Russian literature may be found to apply to species known both from northern Canada and Siberia; for example, in the writings of A.I. Kurentzov, who published a series of articles on the butterflies of the Soviet Far East. The combination of a text written in Russian, rather poor ink-sketch illustrations, and unavailability of the material studied meant that North American workers could not identify the new species proposed by Dr. Kurentzov. Fortunately, J.D. Lafontaine, working with Jim Troubridge, was able to borrow Kurentzov's original Type Specimens from his widow in Vladivostok. These were located by V.S. Kononenko, also of Vladivostok, and transported to Ottawa by Kauri Mikkola via Finland. Study of these specimens by Troubridge and comparison with the type specimens of species described from northern Canada by Troubridge and others leads to the following new synonymies:
Oeneis alpina Kurentzov, 1960 is the correct name for Oeneis excubitor Troubridge, Philip, Scott, and Shepard, 1982.
Oeneis rosovi Kurentzov, 1960 is the correct name for Oeneis philipi Troubridge, 1988.
Oeneis polixenes beringianus Kurentzov, 1960 is the correct name for Oeneis polixenes luteus Troubridge and Parshall, 1988.
Many butterflies vary in appearance in different parts of their geographical range and the use of subspecies categories is our way of placing formal names on this variation. When populations of butterflies look different in geographically separated areas, subspecies classification can be relatively straightforward. In most instances, however, the range of a species, and consequently the variation, is more or less continuous. Frequently, populations in open arid areas like the Great Plains tend to be much paler than populations of the same species from wetter forested areas, and specimens in the northern part of the species range tend to be smaller and darker than those from farther south. To place formal names on this type of continuous and habitat-influenced variation can be endless, with no two specialists agreeing on where limits should be drawn.
At the other end of the spectrum, many western checkerspots and parnassians can look quite distinctive in different mountain ranges and sometimes from colony to colony. Again, there can be problems trying to group this type of variation into subspecies. We do not give a lot of weight to the concept of using formal subspecies names for most types of geographical variation, but we do list and briefly discuss the subspecies names that are currently in use for populations in different parts of Canada.
© 2003. Reproduced with permission from The Butterflies of Canada by Ross A. Layberry, Peter W. Hall, and J. Donald Lafontaine. University of Toronto Press; 1998. Specimen photos courtesy of John T. Fowler.
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Date Modified: 2010-05-31