Italicize words and phrases from other languages unless they have become part of English, such as the French word “bourgeois” and the Italian “pasta.” If a word is in an English dictionary, it does not need italics.

At last one of the phantom sleighs gliding along the street would come to a stop, and with gawky haste Mr. Burness in his fox-furred shapka would make for our door.

—VLADIMIR NABOKOV, Speak, Memory

Always italicize Latin genus and species names.

The caterpillars of Hapalia, when attacked by the wasp Apanteles machaeralis, drop suddenly from their leaves and suspend themselves in air by a silken thread.

—STEPHEN JAY GOULD, “Nonmoral Nature”