Science writing and editing: How to write scientific names

The Latin scientific name of a species, be it plant, animal, bacterium, fungus, etc., is a two-part name consisting of the genus name first (by the way: one genus, two genera) and the species name second. For example, the domestic cat is known as Felis catus. Although the genus name can be used on its own (there are several other species in genus Felis, for instance the wildcat, Felis silvestris), the species name never appears on its own.

The basic rule for writing a scientific name

1. Use both genus and species name: Felis catus.
2. Italicize the whole name.
3. Capitalize only the genus name. (In the past you would capitalize the species designation if it was derived from a proper name, e.g., Megalonyx Jeffersonii, but now the species designation is always lowercased: Megalonyx jeffersonii.)

Rules for abbreviating the genus name

After the first use, the genus name can be abbreviated to just its initial: F. catus.

1. When a section of the text might be displayed on its own, you might want to spell out the name in full the first time it appears there. For instance, some academic journals require that you write out the genus in full the first time it is used in the abstract, and in all tables and table captions.
2. When you introduce the name of another species in the same genus, you can use the abbreviated genus name for the new species:1 The domestic cat is species Felis catus. Both F. catus and its wild relative, F. silvestris . . .
3. If you are discussing two species that belong to different genera that nevertheless start with the same letter, say, Leopardus pardalis, the ocelot, and the Canada lynx, Lynx canadensis, it is better not to abbreviate their genus names.
4. Abbreviations of more than one letter: I’ve seen a few instances of two-letter abbreviations of genus names, for instance Au. afarensis and Ar. ramidus for Australopithecus afarensis and Ardipithecus ramidus, and I’ve seen discussion of two- or three-letter genus abbreviations for some taxonomic groups. Butcher’s Copy-editing2 says they are to be avoided, but they’re permissible to avoid ambiguity.3 I recommend checking with your target publication to see whether they allow this style.
5. Sometimes the full genus name isn’t spelled out on first use. Some organisms, such as the famous study organisms E. coli and C. elegans, are so well known that it’s common in informal discussion to just use the abbreviated version of the name.

Names of taxonomic levels above the genus level

The names of higher taxonomic levels (family, order, class, phylum or division, and kingdom) should be capitalized but not italicized (see Chicago 8.126 and Butcher’s 13.5.1). Common names derived from taxon names, for instance “felines” for members of the family Felidae, are not capitalized. A common name that is derived from a genus name, such as gorilla, is not capitalized either (see Chicago 8.127).

Names of taxonomic levels below the species level

Below the level of species there are subspecies and varieties.

1. The subspecies name is italicized.
2. In zoology, the subspecies is not indicated by any label; it just follows the species name: the European wildcat is Felis silvestris silvestris. If the subspecies name is the same as the species name, it can be abbreviated: Felis s. silvestris.
3. In botany, the subspecies is indicated by “subsp.” or “ssp.” (Butcher’s recommends subsp.4): Juncus effusus subsp. solutus. The “subsp.” label is not italicized.
4. The name of a variety is italicized, but the “var.” label is not: The insecticide BTK is produced by Bacillus thuringiensis var. kurstaki.

Unknown or unspecified species

When referring to an unidentified species, use the abbreviation “sp.”: The meadow contained several sedge plants (Carex sp.). The plural form is “spp.”: The forest floor contained several species of pixie cup lichen (Cladonia spp.). The “sp.” and “spp.” labels are not italicized.

The species author and the sp. nov. tag for introducing new species in the literature

When a species is being formally introduced in a scientific paper, the name of the author (the person who first described the species in academic literature) is usually given.

1. The author name is not italicized: The straightleaf rush is Juncus orthophyllus Coville.
2. The name may be abbreviated. Carolus Linnaeus, a biologist who is such a hero his name was Latinized, gets the abbreviation “L.”: The European meadow rush is Juncus inflexus L.
3. If the author name is in parentheses, that indicates that the species was originally assigned to a different genus.
4. The abbreviation “sp. nov.” indicates that a species is being introduced in the literature for the first time. Do not italicize “sp. nov.”: “Pyrococcus furiosus sp. nov. represents a novel genus of marine heterotrophic archaebacteria growing optimally at 100°C”

References

• The Chicago Manual of Style, 17th Edition has a short but useful section on scientific names of organisms. See section 8.119 and following: “Scientific Names of Plants and Animals.”
• Butcher’s Copy-editing, 4th Edition has a good section on biological classification and nomenclature in its science and mathematics chapter.
• For a more in-depth treatment of the subject, Chicago recommends: Council of Science Editors Scientific Style and Format, the International Code of Botanical Nomenclature, and the International Code of Zoological Nomenclature

• The New Hart’s Rules also has some useful information on the format of Latin names.
• Wikipedia has a comprehensive entry on binomial nomenclature.

More help with writing scientific papers

For some more help with formatting and style in scientific writing, see “Making your science papers look good.”

Notes

1 Butcher’s Copy-editing 4th Edition, p. 328
2 Judith Butcher, Caroline Drake, and Maureen Leach, Butcher’s Copy-editing, 4th Edition. Cambridge University Press, 2006. ISBN: 9780521847131
3 Butcher’s Copy-editing 4th Edition, p. 328
4 Butcher’s Copy-editing 4th Edition, p. 329