Species without genus : Suetonius, Frontinus, and the organisation of imperial prose

The construction per species is attested in several Latin prose authors of the first and second centuries CE as a principle of thematic organisation. Frontinus, in his Strategemata, develops this into a fully explicit genus/species framework. Suetonius, in the programmatic statement of Aug. 9.1, employs per species as the counterpart to per tempora, yet never refers to overarching genera. This article investigates the significance of that asymmetry. Through an analysis of the semantic history of species — from visual perception to classificatory and rhetorical usage — and of the construction per species in Republican and imperial authors, the study shows that the term functions in this period as a flexible yet consistently recognisable principle of thematic organisation. A close comparison between Frontinus' fully theorised genus/species system and Suetonius' rubric-based arrangement reveals that Suetonius' lexical choice is theoretically informed rather than casual: organising biographical material per species, without subsuming them under explicit genera, produces implicit evaluation through structure and reflects a broader methodological horizon shared by imperial Latin prose. The semantic range of species in Suetonius — spanning both the dissimulation of power and the thematic organisation of discourse — further suggests that this lexical choice is not without broader cultural resonance.