6.2. Names of aggregates of species or subspecies. A specific name may be added in parentheses after the genus-group name, or be interpolated in parentheses between the genus-group name and the specific name, to denote an aggregate of species within a genus-group taxon; and a subspecific name may be interpolated in parentheses between the specific and subspecific names to denote an aggregate of subspecies within a species; such names, which must always begin with a lower-case letter and be written in full, are not counted in the number of words in a binomen or trinomen. The Principle of Priority applies to such names [Art. 23.3.3]; for their availability see Article 11.9.3.5.
Recommendation 6B. Taxonomic meaning of interpolated names. An author who wishes to denote an aggregate at either of the additional taxonomic levels mentioned in Article 6.2 should place a term to indicate the taxonomic meaning of the aggregate in the same parentheses as its interpolated species-group name on the first occasion that the notation is used in any work.
Example. In the butterfly genus Ornithoptera Boisduval, 1832 the species O. priamus (Linnaeus, 1758) is the earliest-named member of an aggregate of vicarious species that includes also O. lydius Felder, 1865 and O. croesus Wallace, 1865. The taxonomic meaning accorded to the O. priamus aggregate may be expressed in the notation "Ornithoptera (superspecies priamus)", and the members of the aggregate by the notations "O. (priamus) priamus (Linnaeus, 1758)", "O. (priamus) lydius Felder, 1865", and "O. (priamus) croesus Wallace, 1865".