When to Capitalize and When to Italicize Scientific Names

People who write about wildlife sometimes need to use scientific names. A species’ scientific name is the one scientists use to be sure they are talking about the same critter no matter which country they come from or which language they speak. It is the recognized Latin name given to an organism. An animal may have numerous common names depending on local preference, but every species known to science has just one scientific name.

A scientific name is comprised of the genus and species. These two words are always written in italics. The genus is capitalized. The species is not, even if it is based on a proper noun such as a place or a person’s name. An example is Merriam’s kangaroo rat, named for C. Hart Merriam: Dipodomys merriami.

The questions that most often come up when dealing with scientific names and other elements of a species’ taxonomy are when to capitalize words and when to italicize them. (See “Kings Play Chess On What?” for more on taxonomy.)

Recently, I had to look up whether to italicize the genus when it stands alone, apart from the species. I was editing an article on trout and salmon and had reviewed it several times. Up to that point, I had left the genus name Salmo in roman type. Sometimes, when you edit, you get into a “fun” mental loop. One part of your brain says, “If I left it this way before, I must have had a good reason. I must have looked it up, and I just don’t remember doing it.” The other part replies, “It doesn’t feel right. Look it up again.” The two sides may haggle, with one side arguing that looking something up twice would indicate you are growing dull-witted. Ignore that judgment and all it implies. Look it up again (and again, if you must).

I did, and I’m glad. I found this great reference page on the National Geographic website that told me everything I needed to know (and then some):


I highly recommend bookmarking National Geographic’s page, if you sometimes have to publish scientific names or other information related to taxonomy and want to get it right. And by the way: The genus should be italicized, even when it stands alone. Thanks, National Geographic!


2 thoughts on “When to Capitalize and When to Italicize Scientific Names

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  1. Also, check out the OWAA Outdoor Reference Manual, pg.124. A similar discussion. Couldn’t find any info in the AP Stylebook, but I seem to remember some disagreement with an editor over the use of italics for scientific names not meeting AP style. Your post reflects what was taught to fisheries majors at Michigan State. Sidebar: when writing longhand, always underline genus and species.

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