Traditionally, Latin (genus, species and subspecies) names of plants and animals are italicized; additional (following) designations (such as “var.” for a variety of a species) are set in roman type. The genus name is capitalized and the species lowercased (even when it is a proper adjective). After initial use, the genus name may be abbreviated.
The traditional style is used by Columns, but most newspapers and AP Style do not use italics, setting everything roman.
Divisions higher than genus—phylum, class, order, family—are capitalized and set roman.
Common names (except of course those that are trademarked or patented) are set lowercase roman, only proper nouns and adjectives are capitalized.
The state bird of Georgia is the brown thrasher or Toxostoma rufum. Other members of the Mimidae family common in Georgia are the gray catbird (Dumetella carolinensis) and the northern mockingbird (Mimus polyglottos). The American robin belongs to a different family.