The Uses of Italic
XIV. Italicize particular letters of the alphabet when referred to as such.
We use a much more frequently than q.
XV. Authorities in science differ in the use of italics and capitals. In strictly scientific matter it is better to follow copy if the copy is intelligently prepared; if not, follow some recognized text-book on the subject.
In general the following rules will be found serviceable.
(a) In botanical, zoological, geological, and paleontological matter, italicize scientific (Latin) names of genera and species when used together (the generic name being in the nominative singular), and of the genera only, when used alone. When genera and species are used together the genus always comes first, species second.
Agaricus Campestris, Felis leo, Conodectes favosus, Phyteuma Halleri,